Development of THz TDS system on the basis of the S …accelconf.web.cern.ch/AccelConf/PAC2013/talks/weobb1_talk.pdfHowever, the accuracy of the THz-TDS system should be improved

NA-PAC 2013@Pasadena, 2nd October, 2013

1

Ryunosuke Kuroda

Senior Researcher, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan

Development of THz TDS system on the basis of the S-band compact electron linac

(Visiting lecturer, Waseda University, Tokyo, Japan)

Y.Taira, M. Tanaka, H. Toyokawa, K. Yamada (AIST)M. Kumaki1, M. Tachibana1, K.Sakaue1, K. Kan2, M. Yoshida3, H. Tomizawa4

1 RISE, Waseda University, Japan, 2 ISIR, Osaka University, Japan3 KEK, Japan4 RIKEN, SPring-8 Center, Japan

Colleagues of THz research


2

Outline• Introduction

• Instruction of THz region

• Methods of THz generation

• Coherent THz radiation (CSR, CTR in our case)

• S-band compact electron linac and THz beam lines at AIST

• Measurement of THz-CTR characteristicsTHz-CTR Profile, Polarization, Frequency-range measurements

with THz real-time camera, Polarizer and BPFs

• Present status of THz-CTR Time-domain spectroscopy (TDS)Setup of THz-CTR-TDS, Preliminary experiment results of THz-TDS with samples

• Summary

In collaborating with Central Custom Laboratory(Japan Custom)

of Ministry of Finance Japan


3

Spin excitation Molecular vibration electronic transition Molecular rotation

Frequency

Wavelength

IR UV

CO2

1nm1μm1mm1m

ArF

Radio wave Light wave

101810151012109106

(0.1~10THz)

THz region :(0.1 ~ 10 THz; 30μm ~ 3mm)

Terahertz (THz) LaserLasercm-

wavem-

waveVHF

Imaging

Science Vol. 297, 761 （2002 ）20 40 60 80 100

0.6 1.2 1.8 2.4 3.0 Frequency/THz

HMX

PETNRDX

PE4

TNT

Semtex

Abso

rban

ce

Wavenumber/cm-1

Nature PhotonicsVol. 2, 541 (2008)

Finger-print spectrumof explosives

Inspection

THz GAP for security fields Hz


4

• Photoconductive antenna with fs-laser (B)

• Nonlinear crystal with fs-laser (B) or (M)

Methods of THz generation

• Parametric Oscillation（TPO, is-TPG） (M)

100nw～10mW

10mW～1W

• Free electron laser（FEL） (M) > 1 kW (up to MW)

Peak power

Academic : Measurement of complex dielectric constant, reflective index(organic electroluminescence(EL), polymer…) …etc

Security : Inspection of explosives, illegal drug, handgun, knives …etcMedical : Diagnostics of skin/ breast cancer …etc

• Coherent radiation with ultra-short electron bunch (B) > 1 kW (up to MW)

High Peak Power

For the in-situ measurement and the solvation sample measurement,High peak-power THz source is strongly required.

Type: Broadband (B), Monochromatic (M)

Application Fields

Therefore

However, THz radiation is strongly absorbed by the atmosphere (water)!Low peak power THz source can not be applied to industrial uses.

Laser based

Accelerator based


5

Coherent THz radiation

Coherent Transition radiation (CTR)

Coherent Synchrotron radiation (CSR)

))()1(1( fNII inctot

lc c /Intensity of Coherent radiation

Critical frequencyωcCoherent radiation methods

Frequency (THz)

Inte

nsity

(a.u

.)

To generate the coherent THz radiation, the electron bunch should be compressed to less than 0.5 ps.

THz CSR has been developed for THz imaging (only measure intensity deference

THz CTR has been developed for THz time domain spectroscopy (TDS) . (Fourier limited pulse, small spot size)

In our case

forwardbackward

@40MeV


6

THz freq.: 0.1 ~ 2 THz (up to 5 THz)Pulse energy: >100 nJPeak power: >10 kWSource: CSR for imaging

CTR for spectroscopy

THz specificationFreshness measurement

S-band comapct electron linac at AIST

THz beamlines

Solvation sample measurement

Explosive inspection Inside of Envelope

Envelope

2,4 2,6 3,4 DNTIsomers

0.1THz

0.6THz

@2THz

0.3THz

THz beam lines summary at AIST


7


• Instruction of THz

• Generation methods of THz wave

• S-band compact linac and THz beamlines at AIST

• Coherent THz radiation source and its applicationsTHz-CTR Profile, Polarization, Frequency-range measurements



• Summary

• Introduction • Instruction of THz


• Coherent radiation (CSR, CTR in our case)

• S-band compact linac and THz beam lines summary at AIST




• Summary


8

Measurement of THz-CTR characteristicsTHz-CTR Profile measurement

with THz Camera (made by NEC corp.)

View area :7.5mm×5.6mmFrame rate: 30Hz

Ultra-short electron beam

Rotating Polarizer, Band Pass Filter(BPF) etc

Al Al2O3

ForwardTHz-CTR

Backward


9

THz-CTR Profile measurement

Ultra-short electron beamTHz-CTR Polarization measurement



10



Linearly Polarizer

THz-CTR Polarization measurementwith THz Camera (made by NEC corp.)


11



Linearly Polarizer



12



Linearly Polarizer

with Linearly Polarizer



13



Linearly Polarizer

with Linearly Polarizer


Radial polarization


15

THz-CTR Profile measurement with BPF

Ultra-short electron beamTHz-CTR measurement



16




BPF


17




1.0THz

BPF


18




1.0THz

BPF (1.0 – 5.0 THz)


20


• Instruction of THz region


• Coherent THz radiation (CSR, CTR in our case)

• S-band compact linac and THz beam lines summary at AIST




• Summary

In collaborating with Central Custom Laboratory(Japan Custom)

of Ministry of Finance Japan


21

-5 0 5 10 15 20 25 30 35

-1

0

1

2

3

4

Am

plitu

de, n

A

Time, ps

0 2 4 6

1E-13

1E-12

1E-11

1E-10

Frequency, THz

Am

plitu

de, a

.u.

Fourier transform

Time domain Frequency domain

THz time-domain spectroscopy (THz-TDS) has recently emerged as a useful probe for the investigation of illegal materials such as explosives and drugs.

THz-CTR Time Domain Spectroscopy(TDS)with EO sampling method

fs-laser based THz-TDS system

(Temporal decoding)


22

Principle of EO sampling method for THz-TDS

[0,0,1]

[-1,1,0]

Ellipsoid of Refractive index THz E_field

Probe laser E_field(horizontaly linear

polarized)

Irradiated THz can make Pockels effect in EO crystal

< 1 1 0 > oriented ZnTe crystal

Measurement of the phase difference Γ

x

y

・ Initial E_field of probe laser

・ Output E_field of probe laser

←horizontal←vertical

←vertical

←horizontal


In Vacuum In Air

EO crystal(ZnTe 1mmt)


Probe beam(fs laser)

PD

PD

THz-CTRSample

Polarizer

Frequency domain

FTTHz Spectrum

Time domain

Setup of THz-CTR Time-domain spectroscopy (TDS)

with EO sampling method (pump-probe technique)

23


24

THz-TDS Result with Polyethylene(PE) sampleTo demonstrate the THz-TDS system, the refractive index measurement has been done using the well-known sample (PE)It is well-known that PE has about 1.5 refractive index from optical to THz region.

THz temporal waveform

THz spectrum

Phase Sample: Polyethylene(PE) plate

(1 mmt)

Calculated

Refractive index

FT


25

PE: n = [email protected] - 2THz



THz spectrum


(1 mmt)

Calculated

Refractive index

FT


26

PE: n = [email protected] - 2THz



THz spectrum


(1 mmt)

Calculated

Refractive index

FT

We have checked the performance of THz-CTR-TDS.


27

Pellet (1 mmt) ofMethoxyphenamine hydrochloride (MPA)

(Imitation Drug of Methamphetamine)


THz spectrum

FT

Calculated

Absorption spectrum

THz-TDS Result with drug sample (MPA)


28




THz spectrum

FT

Calculated

Absorption spectrum



29




THz spectrum

FT

Calculated

Absorption spectrum


The sample absorption has been successfully measured in atmosphere. However, the accuracy of the THz-TDS system should be improved.One of the solutions is the single-shot measurement

with the chirped pulse laser (spectral decoding).Now, we are preparing the single-shot scheme.


In near future, single-shot measurement (Spectral decoding) will be performed.




30

Summary

THz frequency range: 0.1 – 5.0 THz

In-situ Security Inspection (Investigation of explosives

and illegal drugs)

1. High peak power THz source has been developed with CSR, CTR techniqueson the basis of the S-band compact electron linac at AIST.

2. THz-CTR characteristics (Profiles, Polarization, Frequency range) have been measured with the real-time THz camera, Polarizer and BPFs

3. THz-CTR Time-domain spectroscopy (TDS) has been demonstrated in freq. range between 0.1 – 2 THz. The refractive index (PE) and the absorption (MPA) measurements have also successfully performed in atmosphere.


In near future, single-shot measurement (Spectral decoding) will be performed.




31

Summary

THz frequency range: 0.1 – 5.0 THz

In-situ Security Inspection (Investigation of explosives

and illegal drugs)

Thank you for your attention !

1. High peak power THz source has been developed with CSR, CTR techniqueson the basis of the S-band compact electron linac at AIST.

2. THz-CTR characteristics (Profiles, Polarization, Frequency range) have been measured with the real-time THz camera, Polarizer and BPFs

3. THz-CTR Time-domain spectroscopy (TDS) has been demonstrated in freq. range between 0.1 – 2 THz. The refractive index (PE) and the absorption (MPA) measurements have also successfully performed in atmosphere.


32

REFERENCES

Methamphetamine Methoxyphenamine

Documents

Development of THz TDS system on the basis of the S …accelconf.web.cern.ch/AccelConf/PAC2013/talks/weobb1_talk.pdfHowever, the accuracy of the THz-TDS system should be improved