1

5. Integrated Optics and Molecular Films

Characterization and Applications of Molecular Films

Surface immobilization can affect: binding affinity bio-specificity reaction rates

Impact on several technologies: biosensors bio-materials for medical implants catalysis affinity chromatography

=

Signal Enhancement for Studies in Monolayers and Sub-Monolayers

10,000

1

10

Transmission

ATR

5 mm

ATR with a single-mode integrated optical waveguide

500 nm

4

1010tcTA

9899T

log

%.

Interrogation with Integrated Optical Waveguides

4

10log 10

trA T c t

2

0

2

t

wg

tr

E dzA L

SA t

E dz

10+4 = 10+7 10-3

Atr

Awg t

L

Sensitivity Factor

water, nc = 1.33

glass, nw = 1.56

silica, ns = 1.46

2 22 w st n nV

L

Broadband Spectroscopy of Molecular Sub-Monolayers

UV-Vis Spectroscopy

≈ 200 nanometer

≈ 3 nanometer

≈ 1 millimeter ≈ 34 millimeter

Low-Loss Optical Waveguides in the UV-Vis Spectral Region

Materials Deposition Processes

- SiO2, SiOxNy

- MgF2, CaF2, BaF2

- fluoropolymers (cytop) - Al2O3

- e-beam evaporation - RF magnetron sputtering - ion-beam sputtering - sol-gel

- atomic layer deposition

• Covalent growth • Self-limiting • Conformal coating • 0.1 nm/cycle

=

trimethyl aluminun precursor

water precursor

Atomic Layer Deposition:

number of cycles

1.60

1.62

1.64

1.66

1.68

1.70

1.72

1.74

1.76

1.78

1.80

200 400 600 800 1000

Wavelength (nm)

refr

ac

tiv

e in

de

x

UV light (325 nm) propagating along a single-mode IOW for 34 mm and out-coupling

ALD Al2O3 Film for UV-Visible Single-Mode IOW

Broadband Coupler for Waveguide-based Spectroscopy

iin

sineff i iN n m

Grating-Coupler & Optical Beam with Large Numerical Aperture

sin 2 . .i in N A

central effN

central 2central

2central

Solid-Immersion Lens for Large NA

• Aplanatic (aberration free) • Highly Anamorphic (line beam)

Pereira et al.

3) Ion Milling Etching 4) Surface-Relief Grating

1) Holographic Exposure

He-Cd 442 & 325 nm

Loyd’s mirror

2) Photoresist Development

He-Ne = 632.8 nm

detector

photoresist

developer tank

Sub-Micron Surface-Relief Grating

Experimental Setup

IOW UV-Vis Spectra: down-to-300-nm

358 femto-moles/cm2 4.65 ng/cm2

1.6% of a full monolayer

cytochrome c

≈ 34 millimeter

limit of detection ≈ 1 pg/cm2

Mendes et al., Optics Express 15(9), 5595-5603 (2007)

Changes in Protein Conformation at Very Low Surface Coverage

Surface-Adsorption of Chlorophyll a

Effects of: • Salt Concentration • Surface Hydrophobicity

hydrophilic hydrophobic

10 mM NaCl

1 mM NaCl

Surface Hydrophobicity

Ionic Strength of Solution

• 1.4 µM of chlorophyll a • phosphate buffer, pH = 7.2

1 mM NaCl

10 mM NaCl

1 mM NaCl

10 mM NaCl

Hydrophilic Hydrophobic

Opt Eng, July 2011

TM TE

Polarized Spectroscopy for Molecular Orientation

ATE, ATM

What if we don’t know all the details in the waveguide ?

Isotropic calibration

Sample being studied

2222

22222

2

2cos

cTMnormcTM

cTMnormcTM

nNnN

nNnN

isotrTM

isotrTE

sampleTM

sampleTE

isotr

sample

norm

AA

A

A

,

,

,

,

1.03.0cosP2

Isotropic Sample

Molecular Orientation with Polarized Guided Waves

Fluorescence Excitation for a Cholera Toxin

Biosensor donor acceptor

Cholera Toxin

Kelly et al., Optics Letters 24, 1723-1725, (1999)

Monochromator

Detector

with Los Alamos Nat Labs

Higher Level of Device Integration, Lower CO$T

Price: $446.00

Source: Thorlabs, Inc. http://www.thorlabs.com

Integration is highly needed in the opto-electronic industry !!

Price: $38.50 Price: $58.85

78% for alignment and packaging

Evanescent Coupling in Planar Optical Waveguides

θc

z

θc

nhigh

nlow

Array detector

Presence of evanescent fields strongly affect

the spatial emission profile of

radiating dipoles !!!

bound modes

substrate

substrate radiation modes

cover-substrate radiation modes

waveguide cover

Once the fluorophores are excited, where the power goes?

z

x

22 2. i iW E E

2

,

2

, ,

2 y m

m f m eff m

E z

E h

2 2

0

2

2

2

0

2 ( , )s cn n

y s

s

s s

E z kdk

E k

2 2

2

2

2 2 2

2 ( , )s

s c

n

y s

s

cn ns s c s

s

E z kdk

kE k E k

k

TE modes

bound modes:

substrate radiation modes:

cover-substrate radiation modes:

TM modes

bound modes:

substrate radiation modes:

cover- substrate radiation modes:

2

,

2

,0,2

0

12

y m

m f m

eff m

f

dH z

z dz

Hh

n

2

,

2

,0,2

0

2 my m

m f m

eff m

f

H zz

Hh

n

2 2

0

2

2

2

0 0

2

0

,12s c

y sn n

s

s s

s

dH z k

z dzdk

H k

n

2 2

0

2

2

2

0 0

2

0

2 ,s c

sn n

y s

s

s s

s

kH z k

zdk

H k

n

0

2 2

0

2

2

2 22 0

2 2

0

,12s

s c

y sn

s

s s c scn n

s s c

dH z k

z dzdk

H k H kk

n k n

0

2 2

0

2

2

2 22 0

2 2

0

2 ,s

s c

sn

y s

s

s s c scn n

s s c

kH z k

zdk

H k H kk

n k n

Fluorophore location:

1

h

z

h

1.33

1.56 1.46 WTE+WTM

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

Bound modes

Substrate modes

Cover-substrate modes

Sum of all modes

Refractive index

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

Bound modes

Substrate modes

Cover-substrate modes

Sum of all modes

Refractive index profile

2 WTM

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

teBound modes

Substrate modes

Cover-substrate modes

Sum of all modes

Refractive index profile

2 WTE

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

h = 3.6 lambda

h = lambda

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

h = 3.6 lambda

h = lambda

Dependence on WG thickness

single-mode

multi-mode ( , 4 modes)

( )h

nf = 1.56

3.6h

1.30

1.35

1.40

1.45

1.50

1.55

1.60

1.65

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

h = 3.6 lambda

h = lambda

bound modes

sum of all modes

substrate modes

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

h = 3.6 lambda

h = lambda

cover-substrate modes

Dependence on WG refractive-index:

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

nf = 2.30

nf = 1.56

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

nf = 2.30

nf = 1.56

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

nf = 2.30

nf = 1.56

bound modes

sum of all modes

substrate modes

single-mode (nf = 1.56)

multi-mode (nf = 2.30, 4 modes)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

-4 -3 -2 -1 0 1 2 3 4 5z/h

sp

on

tan

eo

us

em

iss

ion

ra

te

nf = 2.30

nf = 1.56

cover-substrate modes

1

h

2s

2wg nn

h2V

Surface-immobilized fluorophores: thickness dependence

h

cover (nc = 1.33)

waveguide (nwg = 1.56)

substrate (ns = 1.46)

2s

2wg nn

h2V

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0 2 4 6 8 10 12 14 16 18 20

Sp

on

tan

eo

us

em

iss

ion

ra

te

Bound modes

Substrate modes

Cover-substrate modes

Sum of all modes

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 2 4 6 8 10 12 14 16 18 20

Sp

on

tan

eo

us

em

iss

ion

ra

te

bound modes

20%

Surface-immobilized fluorophores: wg refractive-index dependence

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20

Sp

on

tan

eo

us

em

iss

ion

rate

sum of all modes

bound modes

1.50

1.56

1.80

2.30

cover (nc = 1.33)

waveguide (nwg, h)

substrate (ns = 1.46)

2 22 wg s

hV n n

1.50 1.56

1.80

2.30

17X

Dipole angular orientation:

cover (nc = 1.33)

waveguide (1.56, h)

substrate (ns = 1.46)

0.0

0.5

1.0

1.5

2.0

2.5

0 0.2 0.4 0.6 0.8 1

0

0.5

1

1.5

2

2.5

0 0.2 0.4 0.6 0.8 1

222 swg nnh

V

2

2z

r =

2 E

z2/(

Ex2 +

Ey2

)

Spo

ntan

eou

s em

issi

on r

ate

V = 1.03

V = 1.53

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 2 4 6 8 10

sum of all modes

bound modes

substrate modes

cover-substrate modes

V = 1.03

V = 1.53

Preview of my Wednesday’s talk

Following Charge-Transfer Processes with Integrated Photonic Devices

Sergio B. Mendes Dept. of Physics and Astronomy

University of Louisville - USA

36 UFRGS - July 15, 2015

NSF, NIH, NASA, KSEF

Acknowledgments:

• Prof. Marty O’Toole • Prof. Bruce Alphenaar • Prof. Cindy Harnett • Prof. Mike Behrenfeld • Prof. S. Scott Saavedra • Prof. Neal R. Armstrong • Prof. Roberto Guzman • Dr. Basil Swanson • Dr. Karen Grace • Prof. Geoff Hoops

• Xue Han (PhD student) • Scott Smith (PhD student) • Jafar Ghithan (Ph.D. student) • Uliana Salgaeva (Ph.D. student, Perm University) • Amna Zojl • Brent Mode • Conrad Smart

Senior Collaborators

Current Students

Financial Support:

• Dr. Rodrigo Wiederkehr (post-doc) • Dr. Mustafa Aslan (post-doc) • Prof. Marcelo B. Pereira (post-doc) • Dr. Brooke Beam (Ph.D.) • Dr. John T. Bradshaw (Ph.D.) • Dr. Anne Runge (Ph.D.) • Dr. Lirong Wang (Ph.D.) • Dr. Emre Araci (Ph.D.) • Sergey Mushinsky (exchange student) • Aleksey Sosunov (exchange student) • Dr. Roman Ponomarev (exchange student) • Boris Anokhin (exchange student) • Donna Orem (MS) • Jennifer Burnett (MS) • Collin Hayes (undergr) • Nathan Webster (undergr) • Courtney Byard (undergr) • Rion Shuppe (undergr) • Paul Davis (undergr) • Daniel Frayer (M.S.) • Jill Craven (undergrad) • Jinuk Jang (undergrad) • Nick Cooper (undergr) • Jason Payne (undergr)

Former Students and Post-Docs