MATERIAL ISSUES: Auxiliary Properties--Optical Loss ONO2000 Tutorial Photothermal Deflection Spectroscopy convenient for defining mechanisms accounting

MATERIAL ISSUES: AuxiliaryProperties--Optical LossONO2000

Tutorial

1

1 0

1 0 0

1 0 0 0

1 0 0 0 0

1 0 0 0 0 0

1 0 0 0 0 0 0

0 . 5 1 1 . 5 2 2 . 5 3

P h o t o n E n e r g y ( e v )

Photothermal Deflection Spectroscopy convenientfor defining mechanisms accounting for absorptionlosses. For telecommunication wavelengths, C-Hvibrational overtones usually dominate.

CLD in APC

MATERIAL ISSUES: AuxiliaryProperties--Optical LossONO2000

Tutorial

It is important to measure optical loss associated with both absorption and scattering. Common methods include those of Teng (shown below) and the cut back method

- 1 . 5

- 1 . 4

- 1 . 3

- 1 . 2

- 1 . 1

- 1 . 0

9876543

D i s t a n c e ( m m )

L o s s = 0 . 7 d B / c m

D a t a

F i t

Optical loss measured for FTC chromophore (max loading) in PMMA

MATERIAL ISSUES: AuxiliaryProperties--Optical Loss

ONO2000Tutorial

•Mechanisms of Absorption Loss--Interband electronic absorption--Vibrational absorption

•Mechanisms of Scattering Loss--Material heterogeneity associated with spin castng--Material heterogeneity associated with poling

-Associated with lattice hardening-Associated electrophoretic effect

--Material damage associated electric field poling--Dust particles and foreign contamination--Optical loss associated with solvent attack during deposition of cladding layers--Optical loss from due to cladding problems--Optical loss associated with reactive ion etching or photochemical processing

MATERIAL ISSUES: AuxiliaryProperties--Lattice Hardening

ONO2000Tutorial

HO OHHO OH

OH

1. spin cast with

diisocyanate crosslinker

2. electric field poling

3. thermal crosslinking

x y z

free-radical copolymerization

with methyl methacrylate and

hydroxyethylmethacrylate

3-D crosslinked network

Unless a high glass transition polymer is utilized, lattice hardening must be carried out to insure adequate thermalstability of the poling-induced electro-optic activity. On suchlattice hardening scheme is the DEC shown below

MATERIAL ISSUES: AuxiliaryProperties--Thermal Stability

ONO2000Tutorial

APC - background

• Full chemical name: Poly(Bisphenol A carbonate-co-4,4'-(3,3,5-trimethylcyclohexylidene)diphenol -- (available from Aldrich Chemical Co.)

• Most common “generic” Polycarbonate is Poly(Bisphenol A carbonate) -- it is notoptimal for devices

• First identified APC as candidate host 2/99

• One of ~20 hosts screened for key properties with & without chromophore Tg = 205°C (compared with 145 -160 °C for Poly(Bisphenol A carbonate)

• Chemical structure lowers tendency to form crystalline regions (haze) common insome other polycarbonates

APC (“amorphous polycarbonate”):

L O C K H E E D M A R T I N

SE 99

C O C O

O

C H

3

C H

3

n

H

3

C

C H

3

C H

3

O O C O C O

O

C

O

C H

3

C H

3

x

y

n

Poly(Bisphenol A carbonate)

(“garden-variety” polycarbonate)

In thermal stability to 100-120 is adequate, thena good host is the APC polymer identified byLockheed-Martin


ONO2000Tutorial

The trick to controlling processing losses is to make sure that thepolymer is sufficiently hard to avoid dielectric breakdown (poling-induced damage) and damage from the solvent used for cladding deposition. A hard lattice also helps to minimize losses in reactive ion etching (RIE). It is also important to maintainconditions of a chemical etch (low kinetic energy of reactive ions). By control of RIE conditions, excess loss due to RIE processing can be kept to 0.01 dB/cm.

With control of all processing conditions, waveguide optical loss can be kept to 1.0 dB/cm.

The greatest source of optical loss associated with active EO circuits is insertion loss associated with mode size mismatch between spherical (approx. 10 m) silica fiber core and elliptical (approx. 1-2 micron) core polymeric waveguide.

Fiber Fiber

Device chip

Motivation

University of Southern California

Propagation loss:

0.4 ~ 1 dB/cm

Fiber coupling loss:

4 ~ 6 dB/ facet

Fiber

Coupling

Loss

Propagation

loss

Device insertion loss = Fiber coupling loss

+ Waveguide propagation loss

MATERIAL ISSUES: AuxiliaryProperties--Coupling Loss andTapered Transitions

ONO2000Tutorial

Conditions on the Mode Matching


N e e d v e r t i c a l e x p a n s i o n

A N D t o k e e p m o d e a w a y

f r o m e l e c t r o d e s / s u b s t r a t e

Waveguide Mode

Fiber Mode

-> Mode size transformer with vertical taper

Upper cladding

C o r e la y e r w i t h

channel waveguide

Lower cladding

Substrate

Top electrode

Ground electrode

MATERIAL ISSUES: AuxiliaryProperties--Coupling Loss andTapered Transitions

ONO2000Tutorial

T a p e r e d u p p e r

c l a d d i n g

L o w e r c l a d d i n g

nc l a d d i n g

< nc

< nc o r e

T o p e l e c t r o d e

G r o u n d e l e c t r o d e a n d s u b s t r a t e

A . B . C .

C o r e

l a y e r

Mode Size Transformer with

Vertical Taper


A . B . C .


ONO2000Tutorial

• Shadow Masking of Ions– Angle ∝ , ,RF Power Gas Pressure

, Time Mask Dimensions– : 0.1-3°Angles

– : 1-9Heights m

– : 200-2,000Lengths m

• Fast Prototyping– Various Angles From Single Mask– No Extensive Fabrication Steps

• Repeatable Quality

4

2

0

0 400 800 1200 1600 (Length )m

Mask

PolymerOffset

6

+ Oxygen CF4 Ions

Three dimensional optical circuits and low loss transitionbetween passive and active waveguides can be fabricated ifvertical transitions can be produced. The first step is toproduce a vertical slope by shadow, gray scale, or offsetmask techniques. Use of a shadow mask is shown below.


ONO2000Tutorial

Variable PhotoresistExposure

RIE SlopeTransfer

WaveguideCompletion

UV

OxygenIons

Cladding

Substrate

Photoresist

Core

Spin-CastingPreserves

Surface Contour

Cladding

Processing steps to produce a vertical transitionare shown.


ONO2000Tutorial

• TM insertion loss ⇒ 8 dB improvement

• TE insertion loss⇒ 9 dB improvement

= 6.5Total length cm– = 2Active core cm– = 1Electrode cm

EO core

Au electrode

-15UV

-73NOA

λ = 1.3 m

3.6 m

1.7 m

A low insertion loss modulator structure is shown.

3-D INTEGRATED OPTICALCIRCUITS: Polarization Splitter

ONO2000Tutorial

Extinctions

TE = 13.6 ± 1.1dB

TM = 15.5 ± 3.7dB

TE TMTE/TM

θ = 0.57°

ΔnTE = 0.025

ΔnTM = 0.019

Analyzerθ

λ=1.31m

PROTOTYPE DEVICE EVALUATION: V

ONO2000Tutorial

V

m

H V

A. Poling

B. Modulator Micro-strip Line

PUSH-PULL DESIGN

PROTOTYPE DEVICE EVALUATION: V

ONO2000Tutorial

Both TACAN and Lockheed-Martin have obtained 1 V V

values for push-pull Mach Zehnder modulators. More typical values for devices such as the package array below is 2-3 V at telecommunication wavelengths.

• Current DeviceV = 2.5 V @ 1300 nm ; 3.7 V @ 1550 nmFrequency to ~ 60 GHzTemperature Maximum ~90°CInsertion Loss 5 - 6 dBExtinction ratio 25-30 dB

• Latest LiNbO3 (Lucent)V = 6 V @ 1550 nmFrequency to 30 GHzTemperature Max. 70°CInsertion loss 6 dB

MATERIAL ISSUES: PrototypeDevice Evaluation--Bandwidth

ONO2000Tutorial

Microstrip line

Etching depth

Waveguide width

Quartz Substrate The active layer

ω1ω2

ωm

LOW FREQUENCYPHOTODIODE

ΔωΔω+ωmΔω−ωm

LOCALOSCILLATOR

MODULATOR

Heterodyne Detection

Δω = ω1 − ω2 eg. Δω =62 GHz

MATERIAL ISSUES: PrototypeDevice Evaluation--Stability

ONO2000Tutorial

TACAN stability data are given below; more data are neededto evaluate thermal and photochemical stability.

DEVICES: Phased Array Radarand Time Stretching

ONO2000Tutorial

Two different approaches to phased array radar including oneutilizing the following voltage controlled RF phase shifter willbe discussed. Also Time Stretching relevant to 100 Gbit/secanalog-to-digital conversion will be demonstrated.

REPRESENTATIVE RECENT PUBLICATIONS

ONO2000Tutorial

1. D. Chen, D. Bhattacharya, A. Udupa, B. Tsap, H. R. Fetterman, A. Chen, S. S. Lee, J. Chen, W. H.

Steier, and L. R. Dalton, “High-Frequency Polymer Modulators with Integrated Finline Transitionsand Low V,” IEE E Photonic sTechnol ogy Letters, 11, 54-56 (1999).

2. . . L R Dal , tonA. . W Harper, A. , RenF. , WangG. Todorova, . J Che , . , n C Zhanga . nd ML ,ee“Polymeric Electro-Opt icModulators: Fr om Chromopho reDes ignt o Integra tionwithSemiconductor VLS I Electronic s andSilic aFibe r Optic ,s” I . . nd Eng Che . m Res, 38, 8-33 (1999).

3. S. . M Garner, . V Chuya , .nov S-S. Le , e A. , . Chen WH. Steier, . . and L RDal , “ton VerticallyIntegrate d Wavegui dePolarizat ionSplitte rs Usi ng Polymers,” IEE E Photonic sTechnol ogy Letters,11, 842-4 (1999).

4. S. . M Garner, .S-S. Le , e V. , ChuyanovA. , ChenA. Ya , coubianW. . H Steier, a . . nd L RDalt ,on“Thr eeDimensiona l Integrat edOptic sUs ingPolymer ,s” IEE E Jour nal o f Select ed Topic sinQuantu mElectronics, 35, 1146-55 (1999).

5. . . L R Dal , . ton WH. Steier, . B H. Robins , . , on C ZhangA. , RenS. Garner, A. , . Chen TLonder , ganL.Irw , . in B Carl , sonL. Fifiel , . d GPhel , . an CKinca , id J . Am , end andA. J , “en Fr omMolecule stoOpto-Chips: Organi c Electro-Opt icMaterial ,s” J . . ChemMater., 9, 1905-21 (1999).

6. . B H. Robins , . . on L RDalt , . on AW. Harper, A. , RenF. , . Wang CZ , . hang GTodor , ovaM. Lee, .RAniszfel , . d SM. Garner, A. , ChenW. . H Steier, S, Houbre , chtA. Pers , oonsI. L , edoux J Zys , s andA. . K Y . J , “en T heMolecula r andSupramolecula r Engineer ing o f Polymer icElectro-OpticMaterial ,s” Chem. Phys., 245, 35-50 (1999).

7. . W H. Steier, A. , ChenS.- . S L , eeS. Garner, H. , ZhangV. , ChuyanovL. . R Da , ltonF. Wa , . ng AS., . Ren CZ , hangG. Todor , ovaA. . W Harper, H. . R Fetterma , . n D Che , . n AU , dupaD. Bhattachar ,ya . and BTsa , “p Polym erElectro-Opti c Device sfor Integrat edOptic ,s” Chem.Phys., 245, 487-506

(1999).8. S. . SL , eeA. H. Udupa, . H Er , lig H. Zha , . ng Y Cha , . , ng C ZhangD.H. , . Chang DBhattacharya, .B

Ts , ap W. . H Steier, L. . R Da , ltona . . nd H RFetterma , "n Demonstrati on o f aPhotonicallyControlledR F Phas eShifter," IEE E Microwav e and Gui ded Wa ve Letters, 9, 357-9 (1999).

9. A. . H U , dupaH. Erl , . ig B Ts , ap Y . , ChangD. , ChangH. . R Fetterma , . n H Zha , . ng SS. L , eeF.Wa , . ng WH. Steier, . . and L RDalt , “on High-Frequenc , y Lo -w Crossta lk Modulator Arra ys Base d on

F TC Polym erSystems,” Electr onicLetters, 35, 1702-4 (1999).10. I. Liakatas, . , C CaiM. Bos , ch M. Jager, . Ch Bosshar , . d PGunter, . , C Zhang andL. . R Da ,lton

“Importanc e o f Intermolecula r Interaction s on th eNonline arOptica l Propertie s o f Pole d Polymers,”A . ppl P . hysLett., in press.

11. Y . Shi, . W Li , . n DJ . Ols , . on JH. Bechtel, . H Z , . hang WH. Steier, . , C Zhanga . . nd L RDalt ,on“Realizat ion o f S 1ub - V V Electro-Opt icModulators,” Science, submit .ted

Documents

MATERIAL ISSUES: Auxiliary Properties--Optical Loss ONO2000 Tutorial Photothermal Deflection Spectroscopy convenient for defining mechanisms accounting