ANNUAL REPORT 2002 - Aaltometrology.aalto.fi/annual_reports/mri-annual-2002.pdf · Distribution: Helsinki University of Technology Metrology Research Institute P.O. Box 3000 FIN-02015

Helsinki University of Technology

Department of Electrical and Communications Engineering

Metrology Research Institute Report 21/2003

Espoo 2003

ANNUAL REPORT 2002


Metrology Research Institute Report 21/2003

Espoo 2003

ANNUAL REPORT 2002Editor Petri Kärhä

Helsinki University of TechnologyDepartment of Electrical and Communications EngineeringMetrology Research Institute

Teknillinen korkeakouluSähkö- ja tietoliikennetekniikan osastoMittaustekniikan laboratorio

Distribution:


Metrology Research Institute

P.O. Box 3000

FIN-02015 HUT

Finland

Tel. +358-9-451 1

Fax. +358-9-451 2222

E-mail: [email protected]

© Metrology Research Institute

ISSN 1237-3281

Picaset Oy

Helsinki 2003

Cover: Coupling supercontinuum radiation generated in a photonic

crystal fiber (fabricated by Crystal Fibre A/S, Denmark) into a

multimode fiber

1

CONTENTS

1 INTRODUCTION............................................................................... 32 PERSONNEL ...................................................................................... 43 TEACHING......................................................................................... 8

3.1 Courses.................................................................................................. 83.2 Degrees.................................................................................................. 9

3.2.1 Doctor of Science (Technology), D.Sc. (Tech.) 93.2.2 Licentiate of Science (Technology), Lic.Sc. (Tech.) 93.2.3 Master of Science (Technology), M.Sc. (Tech.) 9

4 NATIONAL STANDARDS LABORATORY................................ 115 RESEARCH PROJECTS................................................................. 12

5.1 Optical Radiation Measurements ........................................................ 125.1.1 Absolute scale of spectral diffuse reflectance 125.1.2 Optical metrology of thin films with oblique-incidence

spectrophotometric measurements 135.1.3 Characterization of temperature dependence of thin-film

filters for optical communications 145.1.4 Applications of laser scanning method 155.1.5 Development of spectral comparator facility to calibrate

ultraviolet detectors with low sensitivity 165.1.6 Characterization of a photometer measuring LED sources 175.1.7 Improved calibration facilities for UV-meters and UV

standard lamps 195.1.8 Extension of spectral irradiance scales 205.1.9 Radiation temperature measurement 20

5.2 Length Metrology................................................................................ 225.2.1 Iodine-stabilized Nd:YAG laser 225.2.2 Iodine-stabilized He-Ne lasers 225.2.3 Optical frequency comb generator 235.2.4 Transmission grating based diode lasers 24

5.3 Fiber-Optics......................................................................................... 255.3.1 Supercontinuum generation in photonic crystal fibers 255.3.2 Supercontinuum in tapered fibers 265.3.3 Spectral modulation in photonic crystal fibers 275.3.4 Polarization properties of photonic crystal fibers 285.3.5 Compact wavelength reference for optical communications 30

5.4 Microtechnologies............................................................................... 325.4.1 High-Q micromechanical silicon oscillators 325.4.2 Micromechanical resonators for RF-applications 335.4.3 Finite element modeling of microsystems 35

5.5 Applied Quantum Optics..................................................................... 375.5.1 Trapping of neutral atoms 37

2

5.5.2 Laser frequency doubling using a periodically polednonlinear KTP crystal 38

6 INTERNATIONAL CO-OPERATION.......................................... 406.1 International Comparison Measurements............................................406.2 Thematic Networks .............................................................................42

6.2.1 Thematic network for ultraviolet measurements 426.3 Conferences and Meetings ..................................................................426.4 Visits by the Laboratory Personnel......................................................446.5 Research Work Abroad .......................................................................446.6 Guest Researchers ...............................................................................456.7 Visits to the Laboratory .......................................................................45

7 PUBLICATIONS .............................................................................. 467.1 Articles in International Journals.........................................................467.2 International Conference Presentations...............................................487.3 National Conference Proceedings .......................................................527.4 Other Publications ...............................................................................537.5 Patents ................................................................................................53

3

1 INTRODUCTION

The Metrology Research Institute is one of the units at the Department ofElectrical and Communications Engineering of HUT. The research work ofthe Institute consists of optical radiation measurements, laser applications, fi-ber optics and microtechnologies. In 2002, significant achievements weremade in supercontinuum generation in photonic crystal fibers and tapered fi-bers. The supercontinuum can be applied to construct an optical frequencycomb generator on which subject an extensive new project was started. Thecomb generator will eventually allow direct absolute measurement of the op-tical frequencies of laser lines.

One interesting application of optical radiation measurements is spectropho-tometric determination of the parameters of thin-film optical coatings whichare important for various optical components. Our spectrophotometricequipment has significant advantages in reliable determination of the thin-film parameters. In microtechnologies, silicon-based oscillators have beendeveloped which have a short-term stability comparable with quartz oscilla-tors. The micromechanical oscillators would have important advantages inapplications when integrating the components with other circuit elements.

Much of our research work is highly dependent on collaboration with otherorganizations. For the work briefly described in above paragraphs, importantresearch partners are Crystal Fiber A/S (Denmark), Center for Metrology andAccreditation, Moscow State University (Russia), Laser Zentrum Hannover(Germany), VTT, and Nokia Research Centre, just to mention a few.

The Metrology Research Institute provides calibration services for externalcustomers resulting in 50 certificates in 2002. During the year a considerableeffort was devoted to the quality system of these services, which was com-pleted by the end of the year. The quality system relies on international com-parison measurements participated on a regular basis. Favorable results werereceived from these comparison measurements in 2002.

Considering the teaching activities of the Institute, one doctoral degree andfourteen Master’s degrees were completed in 2002. The latter number is anew record of the Institute.

Erkki Ikonen

4

2 PERSONNEL

Helsinki University of TechnologyDepartment of Electrical and Communications EngineeringMetrology Research Institute (Mittaustekniikan laboratorio)P.O.Box 3000, FIN-02015 HUT, Finland

Visiting address: Otakaari 5 A, Espoo (Otaniemi) Finland

Switchboard +358 9 451 1Telefax +358 9 451 2222http://www.hut.fi/HUT/Measurement/

In 2002, the total number of employees working at the Metrology ResearchInstitute was 40.

Telephone E-mail

Wallin, PekkaProfessor, Head of Department,Laboratory Director

451 22800400-445 699

[email protected]

Ikonen, Erkki, Dr.Tech.Professor, Head of the NationalStandards Laboratory

451 2283050-550 2283

[email protected]

Tittonen, Ilkka, Dr.Tech.Professor

451 2287040-543 7564

[email protected]

Ludvigsen, Hanne, DocentAcademy research fellow

451 2282 [email protected]

Hänninen, JaanaAdministrative secretary(leave of absence from July 1)

451 2288050-308 8403

[email protected]

Saloranta, SoileCoordinator (from June 5)

451 2288050-308 8403

[email protected]

http://www.hut.fi/HUT/Measurement/

5

Metsälä, SeppoLaboratory technician(till November 30)

451 2220

Ahtee, Ville, studentResearch assistant


Auromaa, Mikko, studentResearch assistant


Chekurov, Nikolai, studentResearch assistant


Envall, Jouni, studentResearch assistant


Genty, Goëry, M.Sc.Research scientist


Hahtela, Ossi, M.Sc.Research scientist


Heiliö, Miika, M.Sc.Research scientist


Hovila, Jari, M.Sc.Research scientist


Jankowski, Tomasz, studentResearch assistant


Kimmelma, Ossi, M.Sc.Research scientist


Koskenvuori, Mika, M.Sc.Research scientist


Kärhä, Petri, Dr.Tech.Senior research scientist,Quality manager

451 2289050-511 0307

[email protected]

Lehtonen, Mikko, M.Sc.Research scientist


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Lindvall, Thomas, M.Sc.Research scientist


Rissanen, Anna, studentResearch assistant


Manoocheri, Farshid, Dr.Tech.Research scientist,Head of calibration services


Merimaa, Mikko, Dr.Tech.Senior research scientist


Mwakipesile, Gibson, studentResearch assistant(till July 31)

[email protected]

Nera, Kaisa, M.Sc.Research scientist


Nevas, Saulius, M.Sc.Research scientist


Niemelä, Arto, studentResearch assistant(till July 31)


Niemi, Tapio, Dr.Tech.Senior research scientist,Student advisor


Nieminen, Juha, studentResearch assistant


Niinikoski, Laura, studentResearch assistant


Noorma, Mart, M.Sc.Research scientist


Nyholm, Kaj, DocentSenior research scientistMIKES(leave of absence from Oct 21)


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Rantakari, Pekka, studentResearch assistant


Ritari, Tuomo, M.Sc.Research scientist


Salo, Päivi, studentResearch assistant


Simonen, Tarmo, studentNetwork and PC Administrator


Tuominen, Jesse, M.Sc.Research scientist


Vainio, Markku, M.Sc.Research scientist


Väisäsvaara, Juha, studentResearch assistant


Docents and lecturers:

Jokela Kari STUK, Radiation and NuclearSafety Authority

+358 9 759 881

Kalliomäki Kalevi University of Oulu +358 8 553 1011

Kaivola Matti Helsinki University of Technology +358 9 451 3151

Kauppinen Jyrki University of Turku +358 2 333 5670

Ludvigsen Hanne Helsinki University of Technology +358 9 451 2282

Ståhlberg Birger University of Helsinki +358 9 191 1

Franssila Sami Helsinki University of Technology +358 9 451 2332

Häkkinen Esa Helsinki Institute of Technology +358 9 310 8311

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3 TEACHING

3.1 Courses

The following courses were offered by the Metrology Research Institute(Mittaustekniikan laboratorio) in 2002. Those marked by * are given bienni-ally.

S-108.180 Electronic Measurements and Electromagnetic Compatibility2 credits (Petri Kärhä, Esa Häkkinen, Kristian Lahti)

S-108.181 Optics2 credits (Erkki Ikonen)

S-108.186 Microsystem technology4 credits (Ilkka Tittonen and Sami Franssila)

S-108.187 Laboratory course on microsystems3 credits (Ilkka Tittonen and Sami Franssila)

S-108.189 Project Work in Measurement Technology2-5 credits (Pekka Wallin)

S-108.191 Fundamentals of Measurements Y2 credits (Tapio Niemi, Mikko Lehtonen, Pekka Wallin)

S-108.194 Electronic Instrumentation3 credits (Pekka Wallin)

S-108.195 Fundamentals of Measurements A2.5 credits (Tapio Niemi, Mikko Lehtonen, Pekka Wallin)

S-108.198 Biological Effects and Measurements of Electromagnetic Fieldsand Optical Radiation2 credits (Kari Jokela)

S-108.199 Optical Communications and Optical Instruments5 credits (Erkki Ikonen, Edward Mutafungwa)

S-108.901 Electrical Engineering Project1-5 credits (Pekka Wallin)

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S-108.903 Fourier Transforms in Measurements*4 credits (Jyrki Kauppinen)

S-108.911 Postgraduate Course in Measurement Technology7.5 credits (Ilkka Tittonen)

S-108.913 Postgraduate Course in Physics of Measurement*3 credits (Birger Ståhlberg)

S-108.914 Research Seminar on Measurement Science1 credit (Erkki Ikonen)

3.2 Degrees

3.2.1 Doctor of Science (Technology), D.Sc. (Tech.)

Tapio Niemi: Dispersion measurements of fiber-optic components and appli-cations of a novel tunable filter for optical communications

Opponent: Prof. Kristian Stubkjær, Technical University of Denmark/COM

3.2.2 Licentiate of Science (Technology), Lic.Sc. (Tech.)

The Licentiate degree is an intermediate research degree between M.Sc. andD.Sc.

Tuomas Lamminmäki: Coupled micromechanical silicon resonators for highfrequency

3.2.3 Master of Science (Technology), M.Sc. (Tech.)

Mikko Luusalo: Valokuitutukan etäisyys- ja vaimennusmittauksen kalibrointiaktiivisen viiveen avulla

Mika Koskenvuori: Mekaanisen resonaattorin toteuttaminen MHz-alueellaSOL-teknologialla

Samuli Laukkanen: Laser-based Photoacoustic Gas Measurement

Mikko Lehtonen: Supercontinuum generation in photonic crystal fiber

Mikael Sokolnicki: WDM-kaupunkiverkon teknistaloudellinen analyysi

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Mart Noorma: Characterisation of filter radiometers with wavelength – tun-able laser source

Antti Reijonen: Base transceiver station integration and verification

Marko Karhiniemi: Modern optical access networks and services

Jesse Tuominen: Wavelength reference for optical telecommunication

Gibson Mwakipesile: Characterization of temperature effects in thin-film fil-ters for optical communications

Reijo Kärkäs: Kiihtyvyysanturituotteen visuaalisen tarkastuksen automati-sointi

Ossi Kimmelma: Laser frequency doubling using a periodically poled nonlin-ear crystal

Tuomo Ritari: Measurement of polarization-mode dispersion of novel opticalfibers

Miikka Jalanka: UMTS terrestrial radio access network protocols and trans-mission testing environment for the third generation base station

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4 NATIONAL STANDARDS LABORATORY

Metrology Research Institute is the Finnish national standards laboratory forthe measurements of optical quantities. The institute was appointed by theCentre for Metrology and Accreditation (MIKES) in April 1996.

The institute gives official calibration certificates on various optical quanti-ties in the fields of Photometry, Radiometry, Spectrophotometry and FiberOptics. During 2002, 50 calibration certificates were issued. The calibrationservices are mainly used by the Finnish industry and various research organi-zations. There are three accredited calibration laboratories in the field of opti-cal quantities.

The institute offers also other measurement services and consultation in thefield of measurement technology. Various memberships in international or-ganizations ensure that the laboratory can also influence e.g. internationalstandardization so that it takes into account the national needs.

The Metrology Research Institute performs its calibration measurements un-der a quality system approved by MIKES. The quality system is based onISO/IEC 17025.

Further information on the offered calibration services can be obtained fromthe web-pages of the laboratory (http://metrology.hut.fi/). Especially the fol-lowing sub-pages might be useful:

Maintained quantities: http://metrology.hut.fi/cgi-bin/index.cgi?calibration

Price list for regular services: http://metrology.hut.fi/files/pricelist.pdf

Quality system: http://metrology.hut.fi/quality/

Additional information may also be asked from Farshid Manoocheri (Head ofCalibration Services) or Petri Kärhä (Quality Manager):

[email protected], Tel. +358-9-451 2337

[email protected], Tel. +358-9-451 2289

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5 RESEARCH PROJECTS

5.1 Optical Radiation Measurements

5.1.1 Absolute scale of spectral diffuse reflectance

S. Nevas, F. Manoocheri, and E. Ikonen

Measurements of spectral diffuse re-flectance provide valuable informa-tion in various fields of industrialand research applications. They areusually performed relative to a refer-ence standard traceable to an abso-lute scale. At present in Europe, thereare only a few traceable scales of ab-solute diffuse reflectance. The pres-ent scale of spectral diffuse reflec-tance at HUT is based on direct com-parison with standards obtained fromthe absolute scales of PTB (Physika-lisch-Technische Bundesanstalt,Germany) and NRC (National Re-search Council, Canada). In order toovercome the limitations of a relativescale, a gonioreflectometer has beendeveloped that will provide spectraldiffuse reflectance and bi-directionalradiance factors of a range of stan-dards in absolute units.

The instrument consists of a lightsource and a goniometric detectionsystem. The source system includesxenon-arc and quartz-tungsten-halogen lamps and a double mono-chromator with input and output op-tics. The layout of the detection sys-tem is shown in Figure 5.1.1-1. Thedetector consists of a precision ap-

erture followed by a lens, severalbaffles, and a silicon photodiode withhigh-gain preamplifier. The aperturedefines the solid angle for the re-flected radiant flux. The lens focusesthe beam such that the detector is un-derfilled. It also images the plane ofsample surface onto the detector,giving a well-defined collection fieldof view.

Detector pos. 1(incident beam)

Detector pos. 2(reflected radiance)

Sample

Incident beam

Rotary stages

L

θθθθview

θθθθillumination

Figure 5.1.1-1. The layout of the go-niometric detection system.

The spectral radiance factor is meas-ured at a particular illumination andviewing angle. This is realized bymeasuring ratio of the reflected andthe incident fluxes. The diffuse re-flectance is obtained by numericalintegration of the radiance factorsover the whole hemisphere includingas many combinations of incidence

13

and reflection angles as possible inthe measurement plane.

The measurement facility has beencarefully characterized by identifyingall possible sources of systematic er-rors and by establishing uncertainty

budget of the measurements. The de-veloped instrument is going to beused to establish an absolute scale ofspectral diffuse reflectance at HUT.

The work has been financially supported bythe Center for Metrology and Accreditation.

5.1.2 Optical metrology of thin films with oblique-incidence spectropho-tometric measurements

S. Nevas, F. Manoocheri, and E. Ikonen

Dielectric thin films find variety ofapplications in optical technology. Itis often necessary to determine opti-cal parameters of the deposited layer:the complex index of refraction andthe thickness of the film. Opticalcharacterization techniques such asleast-squares fitting of spectropho-tometric transmittance and reflec-tance data are widely used for thispurpose. Usually, normal incidencetransmittance measurements are ex-ploited. However, to compare re-flectance and transmittance meas-urement data, also oblique angle-of-incidence transmittance resultsshould be available. Furthermore,oblique-incidence data may provideadditional information, such astransmittance at Brewster angle withp-polarized light, which would givedirectly the absorption of the sample.

An important precondition for theanalysis procedures to yield reliableresults is accuracy of the spectro-photometric measurements with well-collimated beams. We are able tocarry out high-accuracy measure-ments of spectral regular transmit-

tance and reflectance in such condi-tions. This is a good starting point forstudying characterization of thinfilms by using normal and obliqueangles of incidence.

By employing a thin-film mathemati-cal model we have analyzed the ef-fect of systematic errors onto the de-rived optical parameters of thin films.The studied systematic effects in-clude the angle of incidence, the dis-tribution in the angle of incidencedue to beam collimation, and the an-gle between the plane of polarizationand the plane of incidence.

We have also measured and charac-terized several thin-film samples.The results of optical parameters areconsistent over the incidence anglesbetween 0 and 60 degrees, within thepresent angle-determination uncer-tainties. It is especially important todetermine correctly the angle of inci-dence and the polarization anglewhen measuring close to the Brew-ster angle.

The work has been financially supported byTEKES, Planar, Guideoptics and Liekki.

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5.1.3 Characterization of temperature dependence of thin-film fil-ters for optical communications

G. Mwakipesile, T. Niemi, and E. Ikonen

Wavelength division multiplexing(WDM) in optical-fiber transmissionsystems are very attractive due totheir many advantages, i.e., increasedtransmission capacity, applicabilityto two-way transmission and simul-taneous transmission of digital andanalog signals. Consequently, WDMis used in almost all types of optical-fiber transmission systems, such aslong and short-haul transmissionsystems.

One of the key elements in the WDMoptical communication systems is theoptical filter which is used as a mul-tiplexer and demultiplexer. Narrow-band interference filters have beencommercially in use for some dec-ades, they permit isolation of wave-length intervals down to a few na-nometers or less. In using these fil-ters it is often desirable to know howthe angle of incidence, temperaturevariations and possible imperfectionsaffect their performance. Usually,only the center wavelength, band-width and loss are specified. Amongthe important properties with respectto their application is the wavelengthshift with temperature changes whichcauses a drift of the central wave-length and thus degraded perform-ance.

In this work, the temperature effectsof two kind of thin-film filters, gainflattening filter and dense wave-length division multiplexing filter,are investigated. For making thesemeasurements a special holder forthe filters was designed. The filterwas inserted in this holder which in-cluded a thermo-electric cooler. Theholder was inserted in the air-gap oftwo collimators.

A wavelength-tunable laser was usedas the light source and a wavemeterwas used to measure the opticalpower and wavelength. Control anddata acquisition program (LabView)was used to monitor and record themeasurements while the temperatureof the filter was manually tuned andcontrolled by a temperature control-ler.

It was found out that changes in thetemperature resulted in a shift of thecenter wavelength of the passbandand had relatively little effect on itsshape. The measured wavelengthshift for these filters was ~1pm/ºC ata temperature range of 27ºC – 72 ºC.

The work has been financially supported byTEKES, Planar, Guideoptics and Liekki.

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5.1.4 Applications of laser scanning method

M. Noorma, P. Kärhä, F. Manoocheri, and E. Ikonen

Laser scanning method is a methodto simulate spatially uniform light bysuperposition of laser beams. Thefirst application of the resultingknown spectral irradiance is themeasurement of the spectral irradi-ance responsivity of filter radiome-ters with standard uncertainty lessthan 1×10-3.

In 2002, we studied the method forcharacterization of 900-nm narrow-band filter radiometers, using awavelength-tunable Ti:Sapphire laseras the light source. The effect of in-terference between the reflectionsfrom filter surfaces in the case of co-herent laser light was studied and re-duced with special filter design withanti-reflection coatings. Measuringthe responsivity as a function ofwavelength over a very narrow bandwas used to reveal remaining inter-ference effects. Uncertainty analysisand test results indicate that filter ra-diometers can be characterized with arelative standard uncertainty of9×10-4 using the scanning method.The results were compared with moreconventional monochromator-basedmeasurements. As can be seen inFigure 5.1.4-1, the results agree well,which illustrates improved credibilityof both methods.

Another application of the scanningmethod is the aperture area meas-urements. During the year 2002 we

revealed an interesting effect in thestability of the areas of precision ap-ertures made of black anodized alu-minum.

a)

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

870 880 890 900 910 920 930

Res

pons

ivity

, µA/

(Wm

-2)

Scanning method

Conventional method

b)

-0.06

-0.03

0.00

0.03

0.06Wavelength, nm

RSM

( λ)-R

CM

( λ),

µA/(W

m-2

)

Original differenceWavelength shiftedEffect of resolution included

Figure 5.1.4-1. Spectral irradianceresponsivities measured with thescanning method, RSM(λ), and withthe conventional method, RCM(λ).Absolute differences at measuredpoints are shown in figure b).

We have measured the areas of a setof apertures during a period of fiveyears. The aperture area has tradi-tionally been considered to be stablewith time. However, our measure-ment results indicate a systematic de-crease in the area, which signifi-

16

cantly exceeds the uncertainty ofcalibrations. We have calibrated a setof apertures with 3 mm, 4 mm and8 mm diameters during 1997-2002.The laser scanning method with a633-nm HeNe laser is used for thehigh-precision area measurements.The relative standard uncertainty ofthe calibrations is in the order of4×10-4.

The calibration results indicate acontinuous decrease in the areas ofall measured apertures. The relativedecrease is on the average 6×10-4 peryear, which corresponds to a de-crease in radii by 0.5 µm/year. Thebehavior does not seem to depend onthe use of the apertures.

Figure 5.1.4-2. Edge of a precision aperture. The height of the photo corre-sponds to approximately 40 µm.

The actual shape of the aperture edgeis shown in Figure 5.1.4-2. The de-crease could be explained by a con-tinuous growth of the aluminum ox-ide layer. However this effect shouldbe theoretically much slower. Other

possible causes include diffusion ofthe black dye to the surface of theoxide layer, mechanical stresses inthe bulk, and contamination.


5.1.5 Development of spectral comparator facility to calibrate ul-traviolet detectors with low sensitivity

J. Envall and P. Kärhä

The result of calibration of abroadband ultraviolet detector, usingconventional methods, usually de-pends on the light source. This is dueto the non-ideal spectral responsivityfunction of the detector, which maydiffer considerably from the desiredbox shape. Systematic measurementerrors as high as 50 % are possible if

the detector is used to measure lightsources with different spectralshapes [1].

If the spectral responsivity functionof the detector is known, correctionfactors can be calculated to transferthe calibration between differentlight sources. However, measurement

17

of the spectral irradiance responsivityof UV meters is often complicatedbecause of the low sensitivity of themeters. Detectors have attenuators toallow measurements of high-intensitysources without saturating the photo-diodes used as sensitive elements.

0

20

40

60

80

250 300 350 400 450

Wavelength/nm

µ µµµA/(W

/cm

2 )

Figure 5.1.5-1. Measured spectralirradiance responsivity of a com-mercial UVA detector.

We have developed a high-intensityspectral comparator facility. Theequipment consists of a single grat-ing monochromator and a lightsource. 450-W Xe lamp has beenused as light source because of itssmooth and continuous spectrumover the UV region. In the future, ahigh-intensity Hg lamp will be ac-

quired to produce narrow, intensespectral lines.

Detectors are calibrated in overfilledmode in the diverging output beamof the monochromator. A lineartranslator is used to switch the cali-brated meter with the reference de-tector. As the reference, UV-enhanced, large area silicon photodi-odes with precision apertures areused. For the characterization of thephotodiodes, a pyroelectric radi-ometer with flat spectral responsivityis used.

Figure 5.1.5-1 shows an example of ameasured spectral irradiance respon-sivity of a UVA detector. The irradi-ance levels within the calibrationsare between 1.5 and 4 µW⋅cm-2⋅nm-1

throughout the UVA and UVB re-gions. The uncertainty of the calibra-tions is estimated to be less than 2 %.


[1] G. Xu and X. Huang, “Characteriza-tion and calibration of broadband ul-traviolet radiometers”, Metrologia,37, 235-242 (2000).

5.1.6 Characterization of a photometer measuring LED sources

J. Hovila, P. Kärhä, and L. Mansner*

* Sabik Oy, Porvoo, Finland

The technology to produce LEDs hasimproved rapidly and this hasquickly brought them to wide use inthe lighting industry. The robust

structure and long lifetime of LEDsmake them superior to incandescentlamps in certain applications. How-ever, characterization, colorimetry

18

and photometry of LED light sourcesare complicated because of the sharpspectral features. Measurement errorsup to several percents may occur un-less these spectral features are ac-counted for in the calibration.

In this work we studied different ap-proaches to calibrate a photometerused to measure the luminous inten-sities of LED buoy lanterns (Figure5.1.6-1) used in maritime applica-tions. The International Associationof Marine Aids to Navigation andLighthouse Authorities (IALA) rec-ommends two alternative methodsfor photometer characterization whenmeasuring LED sources [1].

Figure 5.1.6-1. Sabik LED 155buoy lantern (height 140 mm, di-ameter 170 mm).

The first method is more traditionalphotometry, where SCFs are calcu-lated from relative spectral respon-

sivity of the photometer and the rela-tive spectra of the lanterns. Final cor-rection factors are obtained by multi-plying the SCFs with a correctionfactor obtained from CIE standardilluminant A calibration.

The second method is quite different,since the LED lanterns are used asstandard light sources during cali-bration where the photometer is cali-brated absolutely against the refer-ence photometer. The relative spectraof the lanterns are also measured, butonly to calculate the color correctionfactors for the reference photometer.

Measurements were done with bothmethods for red, green, yellow andwhite lanterns. The results agree wellwithin their uncertainties (~1 %).However, our experiences indicatethat the first method, despite beinglaborious, is more practical and ap-plicable way to calibrate a photome-ter for measuring LED sources.Geometrical properties of LEDsources are complicated, thus addinguncertainty to measurements, if lan-terns are used as standard lightsources. Corrections based on rela-tive spectra can be calculated moreaccurately. Also introducing newLED-types to production line is morestraightforward, when only the rela-tive spectra of the new LEDs have tobe known.

[1] International Association of MarineAids to Navigation and LighthouseAuthorities, “Recommendation on thePhotometry of Marine Aids to Navi-gation Signal Lights,” IALA Recom-mendation E-122 (IALA, 2001).

19

5.1.7 Improved calibration facilities for UV-meters and UV stan-dard lamps

P. Kärhä

During 2002, HUT presented twonew UV calibration facilities - Spec-troradiometric calibration setup forbroadband UV meters and a verticalcalibration setup for DXW lamps.

The vertical setup for calibratingDXW lamps is presented in Figure5.1.7-1. The lamp is aligned on topof a 1-m optical rail. The referencefilter radiometer for HUT realizationof spectral irradiance is assembled onthe bottom at 0.5-m distance from thereference surface of the lamp. Be-tween the lamp and the filter radi-ometer one can either install a dual-beam alignment laser or a baffle. Be-hind the lamp there is a radiationshield directing the back reflection ofthe lamp away. The calibration serv-ice is mainly used by institutes meas-uring solar UV, because their stan-dard lamps have to be calibrated withthe same orientation that is used inthe spectroradiometer calibration.

The calibration facility for broadband UV meters is based on a cali-brated spectroradiometer (wave-length region 250 – 845 nm) and acollection of 18-W UV fluorescenttubes. The meters are calibrated withthe same type of lamps that the cus-tomers plan to measure with theircalibrated meter. Also the measure-ment distance is unified if practical.

The lamp is first calibrated at thespecified location using the spectro-radiometer. The measured spectrumis used to calculate the desired meas-urement quantity that can be for ex-ample UVA, UVB, Erythema orV(λ). Measurement of the samesource with the customer meter in thesame location yields an accuratecalibration factor for the specifiedmeasurement situation.

Figure 5.1.7-1. Vertical setup forcalibrating DXW-lamps.

Calibration of the UV-meters de-pends strongly on the source used. Ifthe light source needed can not befound in the HUT lamp collection,

20

the customers may submit their ownlamps to be used with the calibration.


5.1.8 Extension of spectral irradiance scales

P. Kärhä and F. Manoocheri

In 2002, HUT started a new projectthat aims to extend the spectral re-gion of the spectral irradiance cali-brations. Measurements can presentlybe done in the wavelength region 290– 900 nm. The plan is to extend thisregion to cover 250 nm – 2.5 µm thatwould better fulfil the requirementsof customers.

Two new filters at wavelengths of220 and 256 nm were purchased tobe used with a trap detector. Charac-terization of the filters indicated that

the out-of-band transmittances of thefilters are too high. Furthermore, theleakage can not be reduced by addi-tional glass filters because this wouldreduce the peak transmittances toomuch. Preliminary measurementswith lamps verified these findings.The signals obtained in lamp meas-urements were too high. To over-come the problem, solar-blind photo-diodes will be studied.


5.1.9 Radiation temperature measurement

T. Jankowski, M. Noorma, P. Kärhä, T. Weckström*,L. Uusipaikka*, and E. Ikonen

* Centre for Metrology and Accreditation (MIKES)

In 2002, HUT continued in a coop-eration with the Centre for Metrologyand Accreditation (MIKES) the de-velopment of the radiation tempera-ture measurement project as an alter-native to the already existing stan-dards of ITS-90 temperature scale.During this year, three measurementsessions were performed to identify,and eliminate various sources of er-rors, such as misalignment of the fil-ter radiometer, temperature fluctua-tions of the cavity of the radiator andpossible contribution of the back-

ground. Additionally, various nu-merical simulations were performedin order to estimate the influence ofthe leakages of the filers used in fil-ter radiometer.

Misalignment studies led to obtain-ing various angular characteristics ofboth the filter radiometer, and the ra-diator revealing a small misalignmentof the cavity of the radiator.

Performed intercomparisons betweenthe filter radiometer (500 – 900 nm)and the pyrometer (650 nm) of

21

MIKES revealed varying differencesof the order of 5 – 0.5 K betweentemperature values measured withITS-90 and the filter radiometerequipped with different filters. Theobserved temperature dependence ofthe signal lead to discovery of thethermal expansion of insufficientlycooled aperture plate of the blackbody. Analysis of this effect reducedthe discrepancies. The error between

the reference pyrometer and the 800-nm filter was brought down to0.73 ºC in the measurement of1500 ºC temperature.

The work was summarized in themaster thesis titled “Measurement ofRadiation Temperatures with theFilter Radiometers” containing allthe obtained data together with theirinterpretation.

22

5.2 Length Metrology

The lasers used for the basic realization of the meter are located in the labo-ratories of the Metrology Research Institute. The devices are property of theCentre for Metrology and Accreditation (MIKES).

5.2.1 Iodine-stabilized Nd:YAG laser

M. Merimaa, M. Vainio, K. Nyholm*, and E. Ikonen


The frequency stabilization of a fre-quency-doubled Nd:YAG laser isbased on observing saturated absorp-tion of iodine at 532 nm in an exter-nal iodine cell. The Nd:YAG-laser isdirectly modulated and the standardthird-harmonic technique is used forfrequency locking.

The laser system was characterized in2001 in an international comparisonof Nd:YAG lasers (BIPM, May2001). Since then the frequency sta-bilization set-up has been further im-proved (Figure 5.2.1-1). The size ofthe laser set-up has been reduced byone-third and the set-up can now beaccommodated with longer iodinecells. An attenuated infrared output isalso added for e.g. frequency combapplications.

Figure 5.2.1-1. A photograph ofthe frequency stabilization set-up.

5.2.2 Iodine-stabilized He-Ne lasers

K. Nyholm* and M. Merimaa


Three iodine-stabilized red He-Ne la-sers and two multi-color He-Ne la-sers constructed jointly by MIKES

(Centre for Metrology and Accredi-tation) and HUT (Helsinki Universityof Technology) have been main-

23

tained in the qualified conditions.The multi-color MGI2 laser partici-pated in an international comparisonof 543 nm iodine-stabilized He-Nelasers held at BIPM, France, in Feb-

ruary 2002. Absolute frequencymeasurement of the R(12)26-0 andR(106)28-0 transitions in 127I2 at543 nm were carried out during thecomparison.

5.2.3 Optical frequency comb generator

M. Merimaa, K. Nyholm*, V. Ahtee, and E. Ikonen


A new research project was started toconstruct an optical frequency combfor direct frequency measurements atthe optical range. A commercialfemtosecond Ti:Sapphire laser (Gi-gaoptics GigaJet 20) and photoniccrystal fiber (PCF) are used to gener-ate a frequency comb extending overa full optical octave (Figure 5.2.3-1).

Figure 5.2.3-1. Optical setup of thefrequency comb.

The PCF-expanded frequency combis collimated into free space and par-

ticular frequency ranges are sepa-rated for frequency measurements.The frequency comb repetition ratewill be locked to a frequency stabi-lized Nd:YAG-laser (σ(2,τ) ≈1×10-13

at τ =1 s), which serves as a low-noise oscillator. The repetition rateand frequency comb offset frequencyare then determined and referencedto a Cs-atomic clock, which provideslink to the primary frequency stan-dard.

Figure 5.2.3-2. Frequency comb inoperation.

Presently, most of the componentshave been purchased or constructedand generation of the frequencycomb has been demonstrated (Figure5.2.3-2). First absolute frequencymeasurements will be carried out in2003.

24

5.2.4 Transmission grating based diode lasers

M. Vainio, M. Merimaa, K. Nyholm*, and E. Ikonen


External-cavity diode lasers arewidely used e.g. in optical and atomphysics experiments, mainly due totheir good wavelength tunability andimproved spectral properties com-pared to the solitary diode lasers.External-cavity diode lasers havebeen used also in frequency stabi-lized lasers, e.g. at 633 nm, which isan interesting wavelength from themetrology point of view. This inter-est to frequency stabilized diode la-sers has been recently increased as aresult of the invention of the femto-second frequency comb, and conse-quently arisen demand for relativelyhigh power laser sources with highspectral purity.

Using a transmission grating as thefrequency selective component of anexternal-cavity diode laser allowscompact and stable mechanical de-sign. Motivated by the need for opti-cal beat frequency measurementswith the frequency comb, improvediodine stabilized diode laser has beenunder development in 2002. An es-sential part of the implementation hasbeen to construct a more robust andstable transmission-grating laser, op-erating at 633-nm wavelength. Cav-ity of the new laser is hermeticallysealed and it is manufactured fromInvar in order to give protection

against environmental disturbances.Tests and measurements performedwith the first prototype of the laserdemonstrate good spectral purity andenhanced passive frequency stability.

In 2002, the concept of transmissiongrating based external-cavity diodelaser has also been extended to thetelecommunication wavelengthsaround 1.55 µm. In addition to thehigh output power and good spectralpurity, the laser wavelength is widelytunable. These favorable propertiesmake the laser suitable for the pur-poses of optical telecommunications,metrology and spectroscopy. Theoverall tuning range of the con-structed 1.55-µm transmission-grating laser is 128 nm, covering theentire S- and C- bands of opticalcommunications.

The coarse wavelength tuning is ob-tained by mechanically adjusting thegrating angle, while the fine-tuningof approximately 30 GHz is providedby piezoelectric transducers. Due tothe transmission grating geometry,the problem of the beam directionvariation while tuning the wave-length is avoided.

The work has been financially supported bythe Academy of Finland.

25

5.3 Fiber-Optics

5.3.1 Supercontinuum generation in photonic crystal fibers

G. Genty, M. Lehtonen M. Kaivola*, J. Broeng†, and H. Ludvigsen

* Department of Engineering Physics and Mathematics, HUT† Crystal Fibre A/S, Denmark

Photonic crystal fibers (PCFs), alsoknown as microstructured fibers, con-sist of a periodic array of air holesrunning along the core of a silica fiber.This new type of optical waveguidestructure has proven to be particularlyefficient for supercontinuum genera-tion due to the unique dispersionproperties and enhanced optical non-linearities.

We have generated supercontinuum bylaunching femtosecond pulses from amode-locked Ti:Sapphire laser into ahighly birefringent PCF [1]. The fiberhas core dimensions of 1.5×2.4 µm2,and a mode-field area of 2.3 µm2.Evolution of the input pulse spectruminto a supercontinuum was studied bygradually increasing the power of in-put pulses. Figure 5.3.1-1 shows theoutput spectra recorded for the PCF atdifferent average pump powers withthe wavelength lying on the anoma-lous side of the dispersion profile.

Various nonlinear phenomena werefound to contribute to the formation ofthe continuum, such as self-phase

modulation, Raman scattering, four-wave mixing, and soliton decay, de-pending on the type of fiber used togenerate the continuum. This kind of acontinuum source has numerous novelapplications in the fields of opticalmetrology and telecommunications.

-40

-20

0

-40

-20

0

-40

-20

0

400 600 800 1000 1200 1400 1600

-40

-20

0

400 600 800 1000 1200 1400 1600

λpump

=804 nm

Pav

=0.05 mW Pav

=1 mW

c)

e)

g) h)

Pav

=4 mW Pav

=10 mW

Pav

=16 mW Pav

=32 mW

Pav

=45 mW

Spec

tral p

ower

den

sity

[dBm

/nm

]

Pav

=55 mW

Wavelength [nm]

f)

d)

b)a)

Figure 5.3.1-1. Evolution of the su-percontinuum spectrum with in-creasing pump power.

The work has been financially sup-ported by the Academy of Finland.

[1] G. Genty, M. Lehtonen, J. Broeng, M.Kaivola, and H. Ludvigsen, Opt. Ex-press 10, 1083 (2002).

26

5.3.2 Supercontinuum in tapered fibers

T. Niemi, J. Tuominen, M. Lehtonen, G. Genty, and H. Ludvigsen

Tapering of optical fibers refers to aprocess where the diameter of the fiberis reduced by heating and stretching[1]. In practice, the diameter of the fi-ber can be reduced from a standardsize of 125 µm down to 1-2 µm. Asmall diameter of the taper results inhigh intensity of the light. High powerlaser pulses combined with nonlinear-ity of the fiber can be applied in, forexample, generation of an ultra-broadband coherent light source referred toas a supercontinuum [2].

Figure 5.3.2-1. Shape of a fabri-cated fiber taper.

We have built an apparatus for fabri-cating tapers having various profiles.To couple light efficiently from thecore of a standard single-mode fiber tothe tapered waist requires the transi-tion region to be smooth. An exampleof a tapered fiber fabricated with ourdevice is displayed in Figure 5.3.2-1.Lengths of he transition regions are20 mm, the waist is 25 mm long and itis designed to be 3 µm thick. The di-

ameter of the taper is measured with amicroscope. However, a reliablemeasurement of the waist diameterwas not possible due to insufficientmagnification of the microscope.

400 600 800 1000 1200

-40

-30

-20

-10

0

10

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Pump

Inte

nsity

[dB

m]

Wavelength [nm]

Dis

pers

ion

[ns/

nm/k

m]

Figure 5.3.2-2. Supercontinuumfrom tapered fiber (solid line). Dis-persion of tapered fiber (dottedline).

Generation of a supercontinuum ispossible in tapered fibers with a smallwaist. An example of such a contin-uum is shown in Figure 5.3.2-2. It wasgenerated by launching ~200 fs pulsesfrom a femtosecond Ti:Sapphire (Tsu-nami/Spectra-Physics) laser with arepetition rate of 80 MHz and a pumppower of ~100 mW into a ~30 mmlong tapered fiber with a waist thick-ness of ~2 µm. The transition regionsconnecting the taper to the standardsingle-mode fiber are 25 mm long.The spectrum of the laser broadens tocover wavelengths from the blue tonear infrared. This kind of abroadband supercontinuum sourcefinds applications in, e.g., frequency

27

metrology, spectroscopy and tomogra-phy.


[1] T. A. Birks et al., J. Lightwave Tech-nol. 10, 432 (1992).

[2] W. J. Wadsworth et al., JOSA B 19, 2148(2002).

5.3.3 Spectral modulation in photonic crystal fibers

G. Genty, M. Lehtonen, M. Kaivola*, and H. Ludvigsen

* Department of Engineering Physics and Mathematics, HUT

Microstructured photonic crystal fi-bers (PCFs) exhibit some unique opti-cal properties compared to standardoptical fibers. For instance, their dis-persion characteristics can be quiteunusual as the zero-dispersion wave-length of these fibers can be pushedfar into the visible. Also, the possibil-ity to control the mode area in broadranges allows various nonlinear opti-cal processes to be greatly enhanced inPCFs. These characteristics make suchfibers interesting objects for study ofsome fundamental features of pulsepropagation; conveniently in the nearinfrared using short lengths of fiber.We report here on experimental ob-servations on strong modulation in thespectrum of short optical pulsespropagating in a PCF [1].

To observe the phenomenon, an80-MHz pulse train from aTi:Sapphire laser operating at 785 nmwas coupled into a few meter-longhighly birefringent PCF (Crystal FibreA/S). The Ti:Sapphire laser produceslinearly polarized Gaussian pulseswith a FWHM of 200 fs. The spec-trum of the output pulses after propa-

gation through the PCF was recordedusing an optical spectrum analyzer.Spectra of the pulses for different in-put powers are shown in Figure5.3.3-1.

770 775 780 785 790 795 800-60

-40

-20

0

20

40

P p=5 W

P p=5 .5 W

P p=8 W

P p=10 W

Pow

er s

pect

rum

[dB

m]

λ [nm]

Figure 5.3.3-1. Optical spectra ofinitially Gaussian pulses afterpropagation through a PCF. Pp rep-resents the input peak power. An ar-bitrary vertical shift for the spectrahas been added for clarity.

For increasing input power, the am-plitude of the oscillations on the wingsof the spectra is seen to increase andtheir period to decrease. In addition, athigh power levels the shape of thecentral part of the spectrum is alteredand the whole spectrum becomes

28

asymmetrical. We attribute the higheramplitude of the red spectral compo-nents and the shift of the central peakto arise from Raman scattering.

The observations we have made forpulse propagation in the photoniccrystal fiber are in qualitative agree-ment with the earlier results obtainedwith the standard fiber. The oscilla-tions are, however, more pronouncedand extend over a much wider wave-length range.

770 775 780 785 790 795 800-60

-40

-20

0

20

40 P p=5 W

P p=6 W

P p=8 W

P p=10 W

Pow

er s

pect

rum

[dB

m]

λ [nm]

Figure 5.3.3-2. Simulation of opticalspectrum of a pulse after propaga-tion through a PCF using NLS.

To confirm the observed phenomena,we have numerically solved the non-linear Schrödinger (NLS) using thesplit-step Fourier algorithm. Employ-ing the parameter values of our par-ticular fiber (α = 0.15 dB/m, β2 =178 ps2/km, γ = 110 /W/km and TR =15 fs), we have simulated the spec-trum of the pulses after propagationthrough the fiber.

The results are presented in Figure5.3.3-2. Good agreement is foundbetween the experimental observationsand the theoretical predictions. Themodulation is explained to result frominterference between the soliton andthe radiation field, which is createdwhen the Gaussian input pulse evolvesinto an asymptotic soliton [1].


[1] G. Genty et al., CLEO/QELS´02, paperCTuU5.

5.3.4 Polarization properties of photonic crystal fibers

T. Ritari, T. Niemi, H. Ludvigsen, F. Scholder*, M. Legré*, M. Wegmuller*,N. Gisin*, J. R. Folkenberg†, A. Petersson†, and P.M.W. Skovgaard†

* Group of Applied Physics, University of Geneva, Switzerland† Crystal Fibre A/S, Denmark

Photonic crystal fibers (PCFs) are anew class of optical fibers having asilica core surrounded by air holesrunning along the length of the fiber inthe cladding area. We have investi-gated polarization-mode dispersion

(PMD) of PCFs having a large mode-area. PMD is a pulse broadeningmechanism limiting high-speed datatransmission in future optical net-works. The three fiber samples studiedare made of pure silica with a hexago-

29

nal arrangement of air holes aroundthe core. They are labeled PCF10,PCF15, and PCF20, according to theircore sizes of 10.8, 14.8, and 19.4 µm(mean distance between opposite holeedges of the core). The cross-sectionof PCF20 is shown in Figure 5.3.4-1.The ratio of the hole diameter, d, tothe pitch of the structure, Λ, is around0.45.

The PMD of the fiber samples wasmeasured utilizing three conventionalmeasurement techniques. At HUT theJones Matrix Eigenanalysis (JME) andfixed analyzer methods were used em-ploying a commercially available de-vice (Profile PAT9000). The meas-urement techniques used in the Groupof Applied Physics, Geneva (GAP)were JME and the interferometricmethod. The light source for JME wasa tunable laser with a tuning range of1455-1612 nm (GAP) and 1510-1650 nm (HUT). The source for theinterferometric method was a polar-ized LED with a spectrum of 1517-1565 nm (FWHM). At Crystal FibreA/S (CF), the PMD was investigatedby utilizing the FA method.

The measurement results of HUT andGAP agree within the inherent PMDmeasurement limit [1]. The valuesobtained at HUT are in excellentagreement and the same holds for thevalues measured at GAP. The PMD

results of Crystal Fibre A/S are closerto the values obtained in GAP in thecase of PCF10 and HUT in the case ofPCF20.

dΛ

Figure 5.3.4-1. Cross-section ofPCF20.

An extremely low PMD value ofPCF15 indicates that it has an excel-lent symmetry in the hole structure.This proves that it is possible to manu-facture long fibers with a high sym-metry and an even stress distribution.To our knowledge, this is the first ob-servation of such a low PMD valueindicating high quality of the fiber.This could lead to a major break-through in the production of long PCFstructures.

This work was conducted within the COSTAction 265. The work has been financiallysupported by the Academy of Finland.

[1] T. Niemi et al., ECOC'02, paperM.S1.09.

30

5.3.5 Compact wavelength reference for optical communications

J. Tuominen, T. Niemi, and H. Ludvigsen

Modern WDM systems working overa broad wavelength range requiremeans to monitor and calibrate thechannel wavelengths with high accu-racy. A silicon Fabry-Perot etalonprovides a compact and flexiblewavelength reference for these pur-poses [1]. These references also finduse in calibration of measurement de-vices and frequency stabilization of la-sers.

We have developed a wavelength ref-erence based on a tunable silicon eta-lon. The index of refraction of siliconhas a temperature dependence that canbe utilized to tune the transmissionspectrum of the etalon as shown inFigure 5.3.5-1. Increasing the tem-perature of the etalon moves the peri-odic fringes to higher wavelengths andvice versa. The sensitivity of the tun-ing is ~65 pm/K. By knowing the pa-rameters of the etalon, the positions ofthe transmission fringes can be accu-rately determined. Subsequently, afringe can be tuned to any desiredwavelength in the operating range ofthe device with a change of the tem-perature of the etalon.

A computer program has been writtenwith LabView to automate the calcu-lations and the tuning procedure. Op-erating the device includes only typingthe required wavelength to the user

interface. Another program was de-veloped to turn the device into awavelength meter. The operation isbased on a fringe scanning a wave-length range smaller than the FSR.The transmission is measured at inter-vals throughout the scan and thewavelength is determined from thedata.

Figure 5.3.5-1. Tunable spectrum ofthe etalon.

The wavelength accuracy of the de-vice was determined at the 1.55-µmregion by measuring the beat fre-quency of two lasers. One laser waslocked to the center of a transmissionfringe of the etalon and another laserwas locked to an acetylene absorptionline for an accurate reference. The ac-curacy was measured against over 50absorption lines. The measurementpoints indicate an accuracy better than125 MHz (~1 pm). At a broaderwavelength range, form 1.3 µm to

31

1.6 µm, a proper operation has beenconfirmed with a wavelength meter,which limits the accuracy to ±3 pm.The stability of the device was evalu-ated by measuring the wavelength fora period of more than 100 h. Thewavelength remained inside ±0.5 pmfor the duration of the measurement.

Figure 5.3.5-2. The wavelength ref-erence.

The reference was also tested in aWDM testbed at the Technical Re-search Centre of Finland (VTT).~50 kHz pilot tones with 2 kHz spac-

ing were used to identify the channels.At the receiver end, the reference wasscanned across the channels measur-ing the amplitude of the pilot tonesfrom the –30 dBm signal. The scan-ning takes 3 s of time per channel andthe accuracy of the derived channelwavelength was about 3 pm.

The wavelength reference developedis found to be compact, robust, andcost-effective. Its continuous operat-ing range (1300-1700 nm) is superiorcompared to molecular or atomic ref-erences, covering the whole wave-length range of interest for fiber-optictelecommunications. The accuracy ismeasured to be ~1 pm.

The work has been financially supported byNordic Industrial Fund and MIKES.

[1] J. Tuominen, T. Niemi, P. Heimala,and H. Ludvigsen, URSI GA..´02,p1512.

32

5.4 Microtechnologies

5.4.1 High-Q micromechanical silicon oscillators

K. Nera, O. Hahtela, and I. Tittonen

High-Q oscillators are mechanicalstructures with stable and spectrallyvery narrow resonance. Such oscilla-tors have applications as reference os-cillators, sensors and even in very so-phisticated high-precision experimentsfor observing quantum effects.

Gas damping / gas spring in N2

0

100000

200000

300000

400000

500000

600000

700000

800000

0.001 0.01 0.1 1 10 100 1000 10000

pressure [mbar]

Q

Q475 Q100 Q45 Q20 Q5

Figure 5.4.1-1. Q-factor measuredin vacuum chamber with differentgap sizes (Q475,…,Q5 are gap sizesof 475,…,5 µm respectively).

The dynamics of a high-Q mechanicalsilicon oscillator was studied in nitro-gen gas the planar silicon surface be-ing placed close to the torsionally vi-brating oscillator (Figure 5.4.1-1 andFigure 5.4.1-2).

Squeezed film damping is due to theviscous losses of gas flowing in a nar-row gap and it has effects both on theresonance frequency and Q-factor. Be-sides dissipative damping effect, the

squeezed film damping force intro-duces also a gas spring effect. At largesqueeze number (high frequency,small gap) gas is essentially trapped inthe gap and behaves as an additionalspring which can shift the resonance(Figure 5.4.1-2).

Gas damping / gas spring in N2

48910

48930

48950

48970

48990

49010

0.001 0.01 0.1 1 10 100 1000 10000

pressure [mbar]

Freq

uenc

y [H

z]

F475 F100 F45 F20 F5

Figure 5.4.1-2. Gas spring effectcaused clear shift in resonancewhen gap size was decreased(F475,…,F5 are gap sizes of475,…,5 µm respectively).

Typically MEMS devices are charac-terized by very small air gaps betweenthe moving and fixed parts. Thussqueezed film damping effects mustcarefully be taken into account whendesigning and operating MEMS andthey cannot be ignored until at verylow pressures.


33

5.4.2 Micromechanical resonators for RF-applications

M. Koskenvuori, T. Lamminmäki, P. Rantakari,J. Väisäsvaara, and I. Tittonen

Microelectromechanical (MEM)resonators are electrically excitedand read mechanical resonators thatare usually fabricated on a siliconwafer (Figure 5.4.2-1 and Figure5.4.2-2).

Figure 5.4.2-1. Micromechanicalbeam resonator.

These resonators can be a significantparts in the Radio Frequency (RF) –circuits in the future, because manyof the building blocks of a RF-circuitcan be realized using micromechani-cal resonators as a replacement forlarge and expensive discrete compo-nents (Figure 5.4.2-3). For exampleRF-filters and RF-switches can befabricated using micromechanicalcomponents. The greatest expecta-tions are, however, placed on a refer-ence oscillator realized with the aidof micromechanical resonators. The

annual sales of these oscillatorscould reach up to hundreds of mil-lions.

Figure 5.4.2-2. Micromechanicalring resonator.

Micromechanical resonators have al-ready shown the ability to competewith the quartz crystals in short termstability. In practice this means thatwe have been able to fabricate reso-nators with such a high quality factor(Q), that it is possible to realize os-cillators that are comparable with thequartz oscillators in terms of short-term stability. A length-extensionalmode resonator that has been used torealize the aforementioned demon-stration oscillator is presented inFigure 5.4.2-4.

So far the oscillator circuits havebeen fabricated using the discrete

34

components, but with micromechani-cal resonator. This means that one ofthe key areas in research will be inte-grating the oscillator electronics withthe resonator on a single chip. Theother key areas will include increas-ing the long term and temperaturestability of the oscillator.

Figure 5.4.2-3. Schematic view ofthe RF-circuit of the future.

The effect of external factors on sta-bility can be minimized by packagingthe resonators hermetically. Thisminimizes the damping effect of am-bient air and also excludes the effectof humidity and the contaminatingparticles in the surrounding atmos-

phere. The effect of temperaturevariations, however, cannot be ex-cluded by packaging technology.Also the familiar method to cut thequartz crystal in a direction thatminimizes the temperature depend-ency doesn’t work with silicon. Thisleads to a need to design and developa temperature compensation methodfor oscillator to maintain the refer-ence frequency despite the changesin temperature.

Figure 5.4.2-4. Length-extensionalmicroelectromechanical resonatoron SOI (Silicon On Insulator). Theresonance frequency in the longi-tudinal direction of the beam is13 MHz. The areas surrounded byred are attached to the structurallayer.

The work has been financially supported byTEKES, Nokia Research Centre and VTITechnologies.

35

5.4.3 Finite element modeling of microsystems

P. Rantakari, N. Chekurov, and I. Tittonen

Present-day ‘state-of-the-art’ sensortechnology is quite often based onmeasuring very small and complicatedphysical effects. To analyze and opti-mize these devices properly, a finiteelement method (FEM) based softwareis usually required. Here we give anexample of analysis of thermal ane-mometer utilizing ANSYS multiphys-ics software package.

Figure 5.4.3-1. Dynamical behaviorof the microphone was inspected bytransient analysis.

A thermal anemometer measures avelocity of airflow by measuring atraveling time of a heat pulse from aheater to a detector. A 3-ms long heatpulse was generated every 250 ms.The dynamics of the electrical tem-perature measurement signals werethen used to determine the speed ofthe wind. Thus, the time-dependentheat transfer was needed to be simu-lated both in the solid detector and inthe fluid (air).

Figure 5.4.3-2. Speed profile of theflow above the deflector.

The measured data was averaged over100 pulses. No random fluctuationswere included in the simulation. Thesimulation was performed as long as itwas required for that the initial tran-sient oscillations to disappear and thesignal level to stabilize. The exampleof this phenomenon is shown inFigure 5.4.3-1.

Substrate

Air

Figure 5.4.3-3. The Heat distribu-tion of sensor: heat is transported tothe probe lines much faster byflowing air than by the solid sub-strate.

Before the actual anemometer designwas modeled, the speed profile of the

36

moving air above the sensor had to becalculated (see Figure 5.4.3-2). Thedeflector was assumed to be a thin cir-cular plate in order to avoid any tur-bulent effects also the no slip condi-tion was assumed at the fluid-structural interface.

Next the speed profile result wasadded as a constraint to the fluid do-main and the transient analysis for theheat pulses was performed. During thetransient analysis the heat distributionwas observed in the substrate and inthe air region as a function of time(Figure 5.4.3-3).

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15

Tim e (ms)

Out

put

volta

ge (v

)

2.37 m /s s im 2D 11.48 m/s s im 2D 26.64 m/s s im 2

Figure 5.4.3-4. Delay times of heatpulses with various flow speeds.

From the time depended heat distribu-tion the flow velocity can be resolvedas a function of time (Figure 5.4.3-4).

The work has been financially supported byVTI Technologies, Vaisala, Aplac Solutions,Nokia Research Center, and TEKES.

37

5.5 Applied Quantum Optics

5.5.1 Trapping of neutral atoms

T. Lindvall, M. Heiliö, L. Niinikoski, M. Auromaa, E. Herola, M. Merimaa,I. Tittonen, A. Shevchenko*, M. Hautakorpi*, and M. Kaivola*

* Optics and Molecular Materials, HUT

Recently there has been a lot of prog-ress in the field of integrated atomoptics. The research has mainly con-centrated on the use of magnetic con-finement of atoms in the so-calledlow-field seeking states, using themagnetic field created by current-carrying wires. We have proposed analternative technique, where the at-oms are transferred from a gravito-optical trap (GOT) consisting of anevanescent-wave (EW) atom mirroron a prism and a vertical repulsivehollow beam (HB) into transparentmicrotraps fabricated onto the sur-face of the prism, see Figure 5.5.1-1.The microtraps can be electro-optical, using transparent indium tinoxide (ITO) conductors, or magneto-optical, using a transparent magneticyttrium iron garnet (YIG) film. TheITO traps are spin-independent,whereas YIG traps can be made foratoms in either low- or high-fieldseeking states.

The operation procedure is the fol-lowing: First, rubidium atoms arecooled in a magneto-optical trap(MOT) located some millimetersabove the prism surface. The MOT

can be loaded with atoms using aclosely mounted alkali metal dis-penser as a pulsed source. Aftercooling in the MOT, the atoms aretransferred downwards to the GOTinside the hollow beam by simplyletting them fall or by shifting thezero of the magnetic field of theMOT. In the GOT the atoms are fur-ther cooled to a temperature of theorder of a few µK. Finally, the mi-croscopic surface trap is turned on.

prism

EW beam

HBMOTbeams

MOT

EW GOT

Figure 5.5.1-1. The MOT and theGOT. For abbreviations see text.

The ultra-high vacuum system andthe lasers are included in the experi-

38

mental realization of the MOT. Weuse a master-slave configuration,where three diode lasers, capable ofdelivering up to ~50 mW each, areinjection-locked to a transmissiongrating-based external-cavity diodelaser stabilized to the hyperfine

spectrum of rubidium. The vacuumsystem and the Rubidium dispensershave been tested and the realizationof the MOT is the next step.


5.5.2 Laser frequency doubling using a periodically poled nonlinearKTP crystal

O. Kimmelma, S. Buchter*, and I. Tittonen

* Department of Engineering Physics and Mathematics, HUT

Converting the laser light to new opti-cal frequencies can be done by meansof nonlinear optics. In a nonlinearmaterial the polarization of the mate-rial is not only directly proportional tothe electric field. The nonlinear effectscan be observed when the electricfield is strong and the generated fieldinterferes constructively when it ispropagating in the crystal.

Nd:YAG

Lock in amp

HV amp I+DC

RF-signalgenerator

RF-amp

EOMIsolator

PD

piezo

ref

signal

outMode matching

SH separator

oven

PPKTP

Temp control

Figure 5.5.2-1. Setup.

In this work a crystal with periodicallychanged nonlinear coefficient is used.The poling is done by exceeding thecoercive field of the ferroelectriccrystal with an external field. Thetechnique is called periodic poling andthe phase matching using a periodicstructure is called quasi-phase-matching. The used nonlinear material

is potassium titanyl phosphate(KTiOPO4) or KTP and it has verygood mechanical and optical proper-ties for nonlinear optics.

Figure 5.5.2-2. A microscope pic-ture of the poled KTP crystal.

The crystal has been poled with a pe-riod of 9 µm. A Fabry-Perot resonatoris used to amplify the interaction be-tween the laser light and the crystal inorder to convert the fundamental IR-frequency at 1064 nm effectively tothe second harmonic at 532 nm. Thiswavelength is in the region of green.A second harmonic power of 111 mWis created with a fundamental inputpower of 290 mW.

39

For practical applications it is usefulto stabilize the output power. Theresonator is locked to the laser using a

Pound-Drewer-Hall locking scheme.A 2σ stability of 2.5% is achieved inthe period of 8 minutes.

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6 INTERNATIONAL CO-OPERATION

6.1 International Comparison Measurements

CCPR-K1.a International comparison of spectral irradiance

The key comparison is on spectral irradiance measurements of tungsten lampsin the wavelength region from 250 nm to 2500 nm. HUT participates in thewavelength region 290 – 900 nm. HUT conducted their second round of meas-urements in September 2002. The lamps have been returned to NPL for finalmeasurements. Draft A is expected in spring 2003.

CCPR-K2.a International comparison of spectral responsivity in thewavelength region 900 nm to 1600 nm

The measurements for this key comparison were carried out by HUT in 1999.No progress in 2002.

CCPR-K2.b International comparison of spectral responsivity in the visibleregion

The key comparison is on spectral responsivity measurements of trap detectorsand photodiodes in the wavelength region from 300 nm to 1000 nm. The meas-urements for this comparison were carried out by HUT in 2000. Draft A-1 wascirculated to participants in 2002. The results indicate a good agreement forHUT within uncertainties.

CCPR-K6 International comparison of regular spectral transmittance

The key comparison is on spectral regular transmittance measurements in thewavelength region from 380 nm to 1000 nm. The measurements for this com-parison were carried out by HUT in 2000. No progress in 2002.

CCPR-S2 International comparison of aperture area measurements

The measurements for this supplementary comparison were carried out by HUTin 2000. No progress in 2002.

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Bilateral comparison of spectral irradiance with NIST, USA

The spectral irradiance scales of HUT and NIST (1992 scale) were compared inthe 290 – 900 nm region. The comparison indicates an agreement except in theUVB region, where the discrepancies are slightly higher than the uncertainty ofthe comparison. During 2002, the comparison report has published in Metrolo-gia [T. Kübarsepp, H.W. Yoon, S. Nevas, P. Kärhä and E. Ikonen, “Comparisonof spectral irradiance scales between the NIST and the HUT”, Metrologia 39,399-402 (2002)].

Bilateral comparison of illuminance with NIST, USA

The illuminance scales of NIST and HUT were compared in summer 2000. Thecomparison indicates an excellent agreement within the uncertainty of the com-parison. The results have been published in Metrologia [J. Hovila, P. Toivanen,E. Ikonen, and Y. Ohno, “International comparison of the illuminance respon-sivity scales and units of luminous flux maintained at the HUT (Finland) andthe NIST (USA),” Metrologia 39, 219-223 (2002)].

Bilateral comparison of luminous flux with NIST, USA

The new luminous flux scale of HUT was compared with the scale of NIST insummer 2000. The comparison indicates an excellent agreement within the un-certainty of the comparison. The results have been published in Metrologia [J.Hovila, P. Toivanen, E. Ikonen, and Y. Ohno, “International comparison of theilluminance responsivity scales and units of luminous flux maintained at theHUT (Finland) and the NIST (USA),” Metrologia 39, 219-223 (2002)].

Improving the accuracy of ultraviolet radiation measurement

In this project funded by the SMT-programme of the EU, novel filter radiometertechniques developed by HUT were used to compare various ultraviolet cali-bration facilities in Finland (HUT), France (BNM), and UK (NPL). The resultshave been accepted to be published in Metrologia.

Bilateral comparison of spectral diffuse reflectance with MSL, New Zea-land

The diffuse reflectance scale of HUT was compared with the scale of MSL.HUT conducted their part of the measurements in 2001. The results received in2002 indicate good agreement with the white samples. The deviations notedwith gray samples are still under investigation.

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6.2 Thematic Networks

6.2.1 Thematic network for ultraviolet measurements

HUT is the co-ordinator of the Thematic Network for Ultraviolet Measure-ments, which has continued its activities after the EU-funded period.

During 2002, the Thematic Network arranged its fifth Workshop in Kassandra,Greece and published one Newsletter. The Workshop took place on October 6-8. It was hosted by the Aristotle University of Thessaloniki. The number of par-ticipants was 51. Ten oral and nine poster presentations were given to introducelatest innovations in the field of UV measurements. The outcome of the Work-shop was summarized in the extended abstracts published in UVNews 7 in De-cember 2002. This Newsletter and further information on the Workshop can befound in the web-pages of the Network (http://metrology.hut.fi/uvnet/).

6.3 Conferences and Meetings

The personnel participated in the following conferences and meetings:

SPIE’s Photonics West Meeting BiOS 2002, Optoelectronics 2002, LASE 2002,San Jose, California USA, January 19 – 25, 2002; Mikko Merimaa

Meetings with Crystal Fibre A/S and NKT Innovations, Copenhagen, Denmark,February 8 – 10, 2002; Hanne Ludvigsen

Estonian Physics Days, Tartu; Estonia, February 14 – 17, 2002; Mart Noorma

XXXVI Annual Conference of the Finnish Physical Society, Joensuu, Finland,March 14 – 16, 2002; Ilkka Tittonen, Kaj Nyholm, Mika Koskenvuori, PekkaRantakari, Jouni Envall, Jesse Tuominen and Mikko Lehtonen

Micro Structure Workshop 2002, Aronsborg, Sweden, March 19 – 21, 2002;Mika Koskenvuori and Pekka Rantakari

EUROMET Photometry and Radiometry TC meeting, Bern, Switzerland, April7 – 9, 2002; Erkki Ikonen

Finnish Optics Days, Kajaani, Finland, April 24 – 26, 2002; Tomasz Jankowskiand Mart Noorma

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DTIP 2002 of MEMS and MOEMS, Mandelieu, France, May 5 – 8, 2002;Kaisa Nera and Ossi Hahtela

CLEO 2002, Long Beach, California, USA, May 19 – 24, 2002; Goëry Genty

NEWRAD 2002, 8th International Conference on New Developments and Ap-plications in Optical Radiometry, Gaithersburg, USA, May 19 - 23, 2002; ErkkiIkonen, Farshid Manoocheri, Petri Kärhä, Jari Hovila, Saulius Nevas and MartNoorma

UV Workshop, NIST, Gaithersburg, USA, May 24, 2002; Erkki Ikonen, PetriKärhä

Final meeting of the EU-project “Improving the Accuracy of Ultraviolet Radia-tion Measurement,” NMi-VSL, Delft, Netherlands, June 7, 2002; Petri Kärhä

Cooling 2002, Visby, Sweden, June 9 – 12, 2002; Thomas Lindvall

The 4th International Conference on Materials for Microelectronics and Nano-engineering, Espoo, Finland, June 10 – 12, 2002; Saulius Nevas, Mika Kosken-vuori

CPEM 2002, Ottawa, Canada, June 16 – 21, 2002; Mikko Lehtonen, MikkoMerimaa

XXVII General Assembly URSI 2002, Maastricht, the Netherlands, August 17 –24, 2002; Jesse Tuominen

ECOC 2002, Copenhagen, Denmark, September 8-12, 2002; Hanne Ludvigsenand Tapio Niemi

Eurosensors XVI, Praha, Czech Republic, September 15 – 18, 2002; MikaKoskenvuori and Pekka Rantakari

Quantum Optics Euroconference 2002, San Feliu de Guixols, Spain, September21 – 26, 2002; Thomas Lindvall and Ilkka Tittonen

Thematic Network for Ultraviolet Measurements, 5th Workshop on UltravioletRadiation Measurements, Kassandra, Halkidiki, Greece, October 6 – 8, 2002;Petri Kärhä and Erkki Ikonen

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NOT kick-off meeting at NKT Research, Copenhagen, Denmark, October 25,2002; Hanne Ludvigsen and Tapio Niemi

Metrology in European Research Area (MERA) Workshop, Rotterdam, theNetherlands, December 16 – 17, 2002; Erkki Ikonen

6.4 Visits by the Laboratory Personnel

Ilkka Tittonen, University of Konstanz and ETH Zürich, December 29, 2001 –January 4, 2002

Mikko Merimaa, NIST National Institute of Standards and Technology, Boul-der, USA, January 26, 2002 and JILA Joint Institute of Laboratory Astrophys-ics, University of Colorado, Boulder, USA, January 27, 2002

Ilkka Tittonen, Markku Vainio and Ossi Kimmelma, KTH, Stockholm, Sweden,February 4 – 6, 2002

Erkki Ikonen, ETH Zurich, Switzerland, April 10, 2002

Saulius Nevas, National Physical Laboratory (NPL), Teddington, UK, August19, 2002

Erkki Ikonen, Farshid Manoocheri, Petri Kärhä, Jari Hovila, Saulius Nevasand Mart Noorma, National Institute of Standards and Technology (NIST,USA) May 23, 2002.

Petri Kärhä, NMi-VSL, Delft, Netherlands, September 1 – 2, 2002

Petri Kärhä and Erkki Ikonen, Aristotle University of Thessaloniki, Laboratoryof Atmospheric Physics, Greece, October 8, 2002

Goëry Genty and Mikko Lehtonen, Optoelectronics Research Centre, TampereUniversity of Technology, Finland, November 4, 2002

6.5 Research Work Abroad

Dr. Kaj Nyholm, Bureau International des Poids et Mesures (BIPM), ParisFrance, February 4 – 10, 2002

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6.6 Guest Researchers

6.7 Visits to the Laboratory

Dr. Toomas Kübarsepp, Metrosert Ltd., Tartu, Estonia, January 14, 2002

Dr. Yakov Sidorin, Optitune PLC, London, United Kingdom, February 4, May30, June 5, 2002

Prof. Alexander Tikhonravov, Moscow State University, Research ComputingCenter, Moscow, Russia, March 2 – 6, 2002

Dr. Toomas Kübarsepp and Toomas Kolk, Metrosert Ltd., Tartu, Estonia, June12, 2002

Prof. Kristian Stubkjær, Technical University of Denmark/COM, Denmark,June 13 – 15, 2002

Dr. M. Kokarev, Moscow State University, Research Computing Center, Mos-cow, Russia, August 8, 2002

Prof. J. Javanainen, University of Connecticut, Storrs, USA, September 17,2002

Mr. Pan Biqing, Mr. Zhang Yue, Mr. Wu Jian, Mrs. Wang Lanxiang, Mr. LiangJin, and Mrs. Guo Xiaolin, NIM, China, October 4, 2002

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7 PUBLICATIONS

7.1 Articles in International Journals

G. Genty, M. Kaivola, and H. Ludvigsen, “Measurements of linewidth varia-tions within external cavity modes of a grating-cavity laser,” Opt. Commun.203, 295-300 (2002).

G. Genty, T. Niemi, and H. Ludvigsen “New method to improve the accuracy ofgroup-delay measurements using the phase-shift technique,” Opt. Commun.204, 119-126 (2002).

T. Niemi, S. Tammela, and H. Ludvigsen, “Device for frequency chirp meas-urements of optical transmitters in real time,” Rev. Sci. Instrum. 73, 1103-1107(2002).

G. Genty, M. Lehtonen, H. Ludvigsen, J. Broeng, and M. Kaivola, “Spectralbroadening of femtosecond pulses into continuum radiation in microstructuredfibers,” Opt. Exp. 10, 1083-1098 (2002).

A. Haapalinna, S. Nevas, F. Manoocheri, and E. Ikonen, “Precision spectrome-ter for measurement of specular reflectance,” Rev. Sci. Instrum. 73, 2237-2241(2002).

C. J. Marckmann, Y. Ren, G. Genty, and M. Kristensen, “Strength and symme-try of the third-order nonlinearity during poling of glass waveguides,” IEEEPhotonics Technol. Lett. 14, 1294-1296 (2002).

J. Hovila, P. Toivanen, E. Ikonen, and Y. Ohno, “International comparison ofthe illuminance responsivity scales and units of luminous flux maintained at theHUT (Finland) and the NIST (USA),” Metrologia 39, 219-223 (2002).

T. Kübarsepp, H. W. Yoon, S. Nevas, P. Kärhä, and E. Ikonen, “Comparison ofspectral irradiance scales between the NIST and the HUT,” Metrologia 39, 399-402 (2002).

E. Ikonen, “Applications related to maximum intensity correlation of hard xrays,” Phys. Rev. A 66, 065802 (2002).

47

T. Mattila, J. Kiihamäki, T. Lamminmäki, O. Jaakkola, P. Rantakari, A. Oja, H.Seppä, H. Kattelus, and I. Tittonen, “12 MHz Micromechanical Bulk AcousticMode Oscillator,” Sensors and Actuators A 101, 1-9 (2002).

T. Mattila, O. Jaakkola, J. Kiihamäki, J. Karttunen, T. Lamminmäki, P. Ranta-kari, A. Oja, H. Seppä, H. Kattelus, and I. Tittonen, “14 MHz micromechanicaloscillator,” Sensors and Actuators A 97-98, 497-502 (2002).

M. Merimaa, T. Lindvall, I. Tittonen, and E. Ikonen, “All-optical atomic clockbased on coherent population trapping in 85Rb,” J. Opt. Soc. Am. B (in press).

S. Picard, L. Robertsson, L.-S. Ma, K. Nyholm, M. Merimaa, T. E. Ahola, P.Balling, P. Kren, and J.-P. Wallerand, “A comparison of 127I2-stabilized fre-quency-doubled Nd:YAG lasers at the BIPM,” Appl. Opt. (in press).

K. Nyholm, M. Merimaa, T. Ahola, and A. Lassila, “Frequency stabilization ofa diode-pumped Nd:YAG laser at 532 nm to iodine by using third-harmonictechnique,” IEEE Trans. Instrum. Meas. (in press).

S. Picard, L. Robertsson, L.-S. Ma, Y. Millerioux, P. Juncar, J.-P. Wallerand, P.Balling, P. Kren, K. Nyholm, M. Merimaa, T. E. Ahola, and F.-L. Hong, “Re-sults from international comparisons at the BIPM providing a world-wide refer-ence network of 127I2 stabilized frequency-doubled Nd:YAG lasers,” IEEETrans. Instrum. Meas. (in press).

P. Kärhä, N. J. Harrison, S. Nevas, W. S. Hartree, and I. Abu-Kassem, “Inter-comparison of characterisation techniques of filter radiometers in the ultravioletregion,” Metrologia (in press).

P. Kärhä, L. Ylianttila, T. Koskela, K. Jokela, and E. Ikonen, “A portable fieldcalibrator for solar ultraviolet measurements,” Metrologia (in press).

L. Ylianttila, K. Jokela, and P. Kärhä, “Ageing of DXW-lamps,” Metrologia (inpress).

S. Nevas, F. Manoocheri, and E. Ikonen, “Determination of Thin-Film Parame-ters from High Accuracy Measurements of Spectral Regular Transmittance,”Metrologia (in press).

M. Noorma, P. Toivanen, F. Manoocheri, and E. Ikonen, “Characterisation offilter radiometers with wavelength-tunable laser source,” Metrologia (in press).

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7.2 International Conference Presentations

M. Merimaa, “Compact frequency stabilized diode lasers,” in Technical Sum-mary Digest of SPIE’s Optoelectronics 2002, January 20 – 25, 2002, p. 71 (in-vited talk).

T. Lindvall, M. Merimaa, I. Tittonen, and E. Ikonen, “An all-optical atomicclock based on dark states of 85Rb,” in Proceedings of the Sixth Symposium onFrequency Standards and Metrology, Ed. P. Gill, World Scientific, New Jersey,2002, pp. 183-190.

M. Noorma, P. Toivanen, F. Manoocheri, and E. Ikonen, “Characterisation offilter radiometers with wavelength-tunable laser source,” Estonian Physics Day,Tartu, Estonia, February 14 – 17, 2002 (poster).

P. Rantakari, M. Koskenvuori, T. Lamminmäki, and I. Tittonen, “High-Q mi-cromechanical length extensional mode resonator,” Micro Structure Workshop2002, Aronsborg, Sweden, March 19 – 21, 2002 (poster).

P. Rantakari, J. Kiihamäki, M. Koskenvuori, T. Lamminmäki, and I. Tittonen,“Reducing the effect of parasitic capacitance on MEMS measurements,” MicroStructure Workshop 2002, Aronsborg, Sweden, March 19 – 21, 2002 (poster).

K. Nera, O. Hahtela, S. Franssila, and I. Tittonen “Optical interferometric de-tection of a mechanical silicon oscillator,” Proceedings of DTIP 2002 of MEMSand MOEMS, Mandelieu, France, May 5 – 8, 2002, p. 430 (poster).

G. Genty, M. Lehtonen, J. R. Jensen, M. Kaivola, and H. Ludvigsen, “Route tosupercontinuum in photonic crystal fibers,” Proceedings of CLEO/QELS 2002,Long Beach, California, USA, May 19 – 24, 2002, paper CtuU1 (talk).

G. Genty, M. Lehtonen, J. R. Jensen, M. Kaivola, and H. Ludvigsen, “Spectralmodulation due to pulse reshaping in photonic crystal fibers,” Proceedings ofCLEO/QELS 2002, Long Beach, California, USA, May 19 – 24, 2002, paperCtuU5 (talk).

M. Wegmuller, G. F. Scholder, A. Fougeres, N. Gisin, T. Niemi, G. Genty, H.Ludvigsen, O. Deparis, and M. Wicks, “Evaluation of measurement techniquesfor characterization of photonic crystal fibers,” Proceedings of CLEO/QELS2002, Long Beach, California, USA, May 19 – 24, 2002, paper JthA4 (talk).

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P. Kärhä, L. Ylianttila, T. Koskela, K. Jokela, and E. Ikonen, “A portable fieldcalibrator for solar ultraviolet measurements,” in Abstracts of NEWRAD2002,8th International Conference on New Developments and Applications in OpticalRadiometry, Gaithersburg, USA, May 20 – 24, 2002, p. 30 (talk).

P. Kärhä, N. J. Harrison, S. Nevas, W. S. Hartree, and I. Abu-Kassem, “Inter-comparison of characterization techniques of filter radiometers in the ultravioletregion,” in Abstracts of NEWRAD2002, 8th International Conference on NewDevelopments and Applications in Optical Radiometry, Gaithersburg, USA,May 20 – 24, 2002, p. 38 (talk).

S. Nevas, F. Manoocheri, and E. Ikonen, “Determination of thin-film parametersfrom high accuracy measurements of spectral regular transmittance,” in Ab-stracts of NEWRAD2002, 8th International Conference on New Developmentsand Applications in Optical Radiometry, Gaithersburg, USA, May 20 – 24,2002, p. 78 (talk).

T. Kübarsepp, H. Rabus, and C. A. Schrama, “Comparison of methods to derivethe quantum yield of silicon in the near UV,” in Abstracts of NEWRAD2002, 8th

International Conference on New Developments and Applications in OpticalRadiometry, Gaithersburg, USA, May 20 – 24, 2002, p. 97 (poster).

T. Kübarsepp, H. W. Yoon, S. Nevas, P. Kärhä, and E. Ikonen, “Comparisonmeasurements of spectral irradiance between NIST and HUT,” in Abstracts ofNEWRAD2002, 8th International Conference on New Developments and Appli-cations in Optical Radiometry, Gaithersburg, USA, May 20 – 24, 2002, p. 102(poster).

F. Manoocheri, S. W. Brown, and Y. Ohno, “Uncertainty of colorimetric cali-bration of displays at NIST,” in Abstracts of NEWRAD2002, 8th InternationalConference on New Developments and Applications in Optical Radiometry,Gaithersburg, USA, May 20 – 24, 2002, p. 114 (poster).

J. Hovila, P. Toivanen, E. Ikonen, and Y. Ohno, “Comparison of illuminance re-sponsivity and luminous flux units between HUT and NIST,” in Abstracts ofNEWRAD2002, 8th International Conference on New Developments and Appli-cations in Optical Radiometry, Gaithersburg, USA, May 20 – 24, 2002, p. 116(poster).

P. Kärhä, J. Envall, and E. Ikonen, “Study of fiber optic power measurementsusing photodiodes with and without integrating sphere,” in Abstracts of

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NEWRAD2002, 8th International Conference on New Developments and Appli-cations in Optical Radiometry, Gaithersburg, USA, May 20 –24, 2002, p. 129(poster).

M. Noorma, P. Toivanen, F. Manoocheri, and E. Ikonen, “Characterization offilter radiometers with wavelength-tunable laser source,” in Abstracts ofNEWRAD2002, 8th International Conference on New Developments and Appli-cations in Optical Radiometry, Gaithersburg, USA, May 20 – 24, 2002, p. 155(poster).

L. Ylianttila, K. Jokela, and P. Kärhä, “Ageing of DXW-lamps,” in Abstracts ofNEWRAD2002, 8th International Conference on New Developments and Appli-cations in Optical Radiometry, Gaithersburg, USA, May 20 – 24, 2002, p. 119(poster).

S. Picard, L. Robertsson, L.-S. Ma, K. Nyholm, M. Merimaa, T. E. Ahola, P.Balling, P. Kren, and J.-P. Wallerand, “Results from international comparisonsat the BIPM: providing a world wide reference network of 127I-stabilized fre-quency-doubled Nd:YAG laser,” in Proceedings of the Conference on PrecisionElectromagnetic Measurements (CPEM'02), Ottawa, Canada, June 16 – 21,2002, pp. 212-213 (poster).

M. Lehtonen, G. Genty, J. R. Jensen, M. Kaivola, and H. Ludvigsen, “Super-continuum generation in highly birefringent photonic crystal fibers,” in Pro-ceedings of the Conference on Precision Electromagnetic Measurements(CPEM'02), Ottawa, Canada, June 16 – 21, 2002, pp. 214-215 (poster).

K. Nyholm, M. Merimaa, T. Ahola, and A. Lassila, “Frequency stabilization ofa diode-pumped Nd:YAG laser at 532 nm to iodine by using third-harmonictechnique,” in Proceedings of the Conference on Precision ElectromagneticMeasurements (CPEM'02), Ottawa, Canada, June 16 – 21, 2002, pp. 474-475(poster).

S. Nevas, F. Manoocheri, and E. Ikonen, “Determination of thin film parametersfrom high accuracy spectrophotometric measurements,” in Proceedings of the4th Intern. Conf. on Materials for Microelectronics and Nanoengineering, Ha-nasaari Cultural Centre, Espoo, Finland, June 10 – 12, 2002, p. 323 (poster).

M. Koskenvuori et al, “Very High-Q Micromechanical 14 MHz Resonator onSOI,” Fourth International Conference on Materials for Microelectronics andNanoengineering, Espoo, Finland, June, 2002, Proceedings of the Fourth Inter-

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national Conference on Materials for Microelectronics and Nanoengineering,2002, pp. 129-132.

J. Tuominen, T. Niemi, P. Heimala, and H. Ludvigsen, “Compact wavelengthreference for optical telecommunication based on a tunable silicon etalon,” inInternational Union of Radio Science - XXVIIth General Assembly (URSI'02),Maastricht, The Netherlands, August 17 – 24, 2002, paper p1512 (invited talk).

T. Niemi, H. Ludvigsen, F. Scholder, M. Legré, M. Wegmuller, N. Gisin, J. R.Jensen, A. Petersson, and P. M. W. Skovgaard, “Polarization properties of sin-gle-moded, large-mode area photonic crystal fibers,” in 28th European Confer-ence on Optical Communication (ECOC'02), Copenhagen, Denmark, 2002, pa-per M.S1.09 (talk).

T. Lindvall, I. Tittonen, A. Shevchenko, and M. Kaivola, “Spin-PolarizingGravito-Optical Trap for Loading of an Atom Chip,” Quantum Optics, Euro-Conference 2002, San Feliu de Guixols, Spain, September 21 – 26, 2002(poster).

A. Shevchenko, T. Lindvall, I. Tittonen, and M. Kaivola, “Loading an AtomChip from a Gravito-Optical Surface Trap,” Cooling 2002, Visby, Sweden, June8 – 12, 2002 (poster).

M. Koskenvuori, A. Oja, T. Mattila, H. Seppä, J. Kiihamäki, H. Kattelus, T.Lamminmäki, P. Rantakari, and I. Tittonen, “Nonlinear Effects in Bulk Acous-tic Mode Microresonators,” Eurosensors XVI, Prague, Czech Republic, Sep-tember 13 – 19, 2002, Book of Abstracts, 2002, pp. 381-382.

M. Koskenvuori, P. Rantakari, T. Lamminmäki, I. Tittonen, A. Oja, T. Mattila,H. Seppä, J. Kiihamäki, and H. Kattelus, “Enhancing the ElectromechanicalCoupling in Bulk Acoustic Mode Microresonator,” Eurosensors XVI, Prague,Czech Republic, September 13 – 19, 2002, Book of Abstracts, 2002, pp. 383-384.

L. Ylianttila, P. Kärhä, K. Jokela, and E. Ikonen, “A portable field calibrator forsolar ultraviolet measurements,” 5th Workshop on Ultraviolet Radiation Meas-urements, Kassandra, Halkidiki, Greece, October 7 – 8, 2002 (Poster) UVNews7, 16-17 (2002).

J. Envall, P. Kärhä, and E. Ikonen, “High-intensity setup for measuring spectralirradiance responsivities of UV meters,” 5th Workshop on Ultraviolet Radiation

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Measurements, Kassandra, Halkidiki, Greece, October 7 – 8, 2002 (Poster) UV-News 7, 18-19 (2002).

P. Kärhä, “Calibration and intercomparison issues with broadband UV meters,”5th Workshop on Ultraviolet Radiation Measurements, Kassandra, Halkidiki,Greece, October 7 – 8, 2002 (Invited talk) UVNews 7, 29-34 (2002).

7.3 National Conference Proceedings

M. Lehtonen, G. Genty, M. Kaivola, J. R. Jensen, and H. Ludvigsen, “Super-continuum generation, photonic crystal fiber,” Proceedings of the XXXVI An-nual Conference of the Finnish Physical Society, Selected Papers 7, Joensuu,Finland, March 14 – 16, 2002, p. 60 (talk).

J. Tuominen, T. Niemi, P. Heimala, and H. Ludvigsen, “Wavelength referencefor optical telecommunications based on a tunable silicon etalon,” Proceedingsof the XXXVI Annual Conference of the Finnish Physical Society, Selected Pa-pers 7, Joensuu, Finland, March 14 – 16, 2002, p. 72 (poster).

M. Heiliö, E. Vahala, K. Lahti, and I. Tittonen, “Digital frequency stabilizationof a Nd:YAG solid state laser using high finesse optical resonator as a refer-ence,” Proceedings of the XXXVI Annual Conference of the Finnish PhysicalSociety, Selected Papers 7, Joensuu, Finland, March 14 – 16, 2002, p. 62(poster).

K. Nyholm, T. Ahola, M. Merimaa, and A. Lassila, “Optical frequency standardat 532 nm,” Proceedings of the XXXVI Annual Conference of the Finnish Physi-cal Society, Selected Papers 7, Joensuu, Finland, March 14 – 16, 2002, p. 73(poster).

J. Envall, P. Kärhä, and E. Ikonen, “Study of fiber optic power measurementsusing photodiodes with and without integrating sphere,” Proceedings of theXXXVI Annual Conference of the Finnish Physical Society, Selected Papers 7,Joensuu, Finland, March 14 – 16, 2002, p. 74 (poster).

P. Rantakari, M. Koskenvuori, T. Lamminmäki, and I. Tittonen, “High-Q mi-cromechanical length extensional mode resonator,” Proceedings of the XXXVIAnnual Conference of the Finnish Physical Society, Selected Papers 7, Joensuu,Finland, March 14 – 16, 2002, p. 286 (poster).

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A. Shevchenko, M. Hautakorpi, J. Lindberg, T. Setälä, M. Kaivola, T. Lindvall,I. Tittonen, A. Huttunen, M. Rodriguez, and P. Törmä, “A loading system forintegrated atom optics,” Proceedings of the XXXVI Annual Conference of theFinnish Physical Society, Selected Papers 7, Joensuu, Finland, March 14 – 16,2002, p. 223 (poster).

M. Noorma, P. Toivanen, F. Manoocheri, and E. Ikonen, “Characterization offilter radiometers with wavelength-tunable laser source,” Proceedings of Fin-nish Optics Days 2002, Kajaani, Finland, April 24 – 26, 2002, p. 28 (talk).

P. Kärhä, M. Noorma, T. Jankowski, T. Weckström, and E. Ikonen, “Radiomet-ric determination of radiation temperatures,” Proceedings of Finnish OpticsDays 2002, Kajaani, Finland, April 24 – 26, 2002, p. 38 (poster).

7.4 Other Publications

P. Kärhä (editor), Annual report 2001, Metrology Research Institute, HelsinkiUniversity of Technology, Espoo 2002, Metrology Research Institute Report20/2002, 64 p.

M. Noorma, “Police speed measurement devices,” (in Estonian), Tehnika-maailm 11, 86-88 (2002).

M. Noorma, “Traffic radar detectors and jammers,” (in Estonian), Tehnika-maailm (in press).

P. Kärhä (editor), UVNews, The official newsletter of the Thematic Network forUltraviolet Measurements, Issue 7, Espoo 2002, 44 p.

7.5 Patents

S. Metsälä, Veröffentlichung DE 195 816 58 T1, Feinmechanische Einstellvor-richtung (Hienomekaaninen poikittaisasemointilaite), Deutsches Patent- undMarketamt, 2002, 23 p.

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HELSINKI UNIVERSITY OF TECHNOLOGY METROLOGY RESEARCH

INSTITUTE REPORT SERIES

HUT-MRI-R11/1998 I. Tittonen (editor),

Annual report 1997.

HUT-MRI-R12/1998 P. Toivanen, A. Lassila, F. Manoocheri, P. Kärhä and E. Ikonen,

A new method for characterization of filter radiometers. 1998


Annual report 1998.

HUT-MRI-R14/1999 T. Kübarsepp, P. Kärhä, F. Manoocheri, S. Nevas, L. Ylianttila and E. Ikonen,

Absolute spectral irradiance measurements of quartz-halogen tungsten lamps

in the spectral range 290-900 nm.

HUT-MRI-R15/1999 T. Kübarsepp,

Optical radiometry using silicon photodetectors.


Annual report 1999.

HUT-MRI-R17/2000 P. Toivanen,

Detector based realisation of units of photometric and radiometric quantities.

HUT-MRI-R18/2001 P. Kärhä (editor),Annual report 2000.

HUT-MRI-R19/2001 M. Merimaa, T. Lindvall, I. Tittonen, and E. Ikonen,All-optical atomic clock based on coherent population trapping in 85Rb.

HUT-MRI-R20/2002 P. Kärhä (editor),Annual report 2001.

ISSN 1237-3281

Picaset Oy, Helsinki 2003

Documents

ANNUAL REPORT 2002 - Aaltometrology.aalto.fi/annual_reports/mri-annual-2002.pdf · Distribution: Helsinki University of Technology Metrology Research Institute P.O. Box 3000 FIN-02015