Transcript
Page 1: US Army RDECOM/AMRDECUS Army RDECOM/AMRDEC …

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Modulator Evaluation and DemonstrationModulator Evaluation and Demonstration

Paul Ashley

US Army RDECOM/AMRDECUS Army RDECOM/AMRDEC Redstone Arsenal, AL 35898

March 19, 2008March 19, 2008

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Outline

Current status of the evaluation of packaged modulators from Lumera Corporation.

Current status of the investigation of the effect of thin buffer layers on poling.

Plans for transition opportunity modulator demo for military/space applications.

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Thermal Stability of LPD80

Thermal stability of the modulators were evaluated by monitoring the Vπ at the storage temperature of 800C. (Data provided by Lumera Corpration)

Two-parameter KWW model and Jonscher model were used in predicting the usable lifetime of the devices over 5 10 year periodusable lifetime of the devices over 5-10 year period.

The distribution width of relaxation times (0 < β < 1)

Jonscher Model

relaxation times (0 < β < 1)

KWW Model

The average relaxation time constant

• R. Kohlrausch, Ann. Phys. (Leipzig) 12, 393 (1847)• G. Williams and D. C. Watts, Trans. Faraday Soc. 66, 80 (1970)

Jonscher model was preferred because of the its consistency with causality

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Thermal Stability of LPD80

Ignored Average of 5 data sets Normalized (Vπ = 1.0 V at t=0)

1.5

Jonscher Model

Error bars represent the standard deviationCoefficient of determination (r2 = 0.96)

1.1

1.3

V_pi

V π(V

)

τ = 606168 hrsβ = 0.22

( )

0 500 1000 1500 2000 2500Ti (H )

0.9

1.4

1.6

_pi(V)Predictions were made up to

10 b t l ti th

Time (Hrs)

1.2

V_V π10 years by extrapolating the fitted curve. In 5 yrs, Vπ = 1.56 ± 0.01 V

In 10 yrs, Vπ = 1.65 ± 0.02 VWith KWW model, 5 & 10 year predictions were 1 60 V d 1 70 V ti l

0 2 4 6 8 10Time (Years)

1.01.60 V and 1.70 V respectively.

The differences in the predicted values of the models become significant at t >> τ (~ 70 yrs).

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Thermal Cycling

Linear ramp : 300C 800C 300CRamp rate : ~ 0 6 0C/minRamp rate : 0.6 C/minVπ, Modulation Depth, and Total Insertion Loss were monitored in real time.

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Thermal Cycling : Summary

Vπ(V) 3.2 Vπ(V) 3.3 Vπ(V) 3.2

300C 300C

850C

300C 300C

850C3.2

TIL (dB)

9.9

Mod Depth 11 6

3 3

TIL (dB)

9.3

Mod Depth 11 2

3.2TIL (dB)

9.5

Mod Depth 11 630 C 30 C

2 hrs30 C 30 C

3 hrsDepth (dB)

11.6 Depth (dB)

11.2 Depth (dB)

11.6

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Thermal Cycling : Vπ

755

60

75

)

4

5

) )

45

Tem

p(C

)

3

V_pi

(V)

pera

ture

(0C

)

V π(V

olts

)

30

T

2

V

Tem

p

Initial modulation depth ~ 11.2 dB

Final modulation depth ~ 11.5 dB

0

15

0

1Modulation depth varied during the thermal cycle.Mechanical instability in the input fiber connector is suspected.

00 50 100 150 200

Time (min)

0

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Thermal Cycling : TIL (2nd cycle)

7510 5

11.0

60

75

10.0

10.5

(dB

)

45

Tem

p(C

)

9.5

TIL

(dB

)

erat

ure

(0C

)

ertio

n Lo

ss (

30

T

9.0

T

Tem

pe

Tota

l Ins

e

0

15

8 0

8.5

00 50 100 150 200

Time (min)

8.0

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Thermal Cycling : TIL (1st cycle)

10

11.0

60

75

10.0

10.5

C)

45

emp(

C)

9.5

TIL

(dB

)

pera

ture

(0C

n Lo

ss (d

B)

30

T

9.0

T

Tem

tal I

nser

tion

0

15

8 0

8.5Tot

05 30 55 80 105 130 155

Time (min)

8.0

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Photobleaching

0 035

0.040AJ 416

n 0 025

0.030

0.035 AJ 416AJ 309AJ 404LPD 80AJ-CKL1

Photobleached time : 8 – 16 hrs

Δ

0.015

0.020

0.025

UV intensity : 7.9 mW cm-2 (@ 365 nm)

0.005

0.010

0.015

Time (hrs)0 4 8 12 16

0.000

0.005

Time (hrs)

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Preparation of Test Samples for the Measurement of E-O Coefficients

Fabrication of buffer layers on ITO coated glass substrates : Northwestern Univ.Core (AJ-CKL1 in APC) provided by Univ. of WashingtonFabrication of polymer layer and gold electrodes :Fabrication of polymer layer and gold electrodes : AMRDEC, Redstone Arsenal

Poling and removal of gold : by AMRDEC, Redstone ArsenalE-O measurements : Laboratory for Physical ScienceE O measurements : Laboratory for Physical Science

SampleBuffer

Thickness Sample(nm)

ITO/Polymer 0

ITO/SiO2/Polymer 50

6 mm diameter

ITO/SiO2/Polymer 280

ITO/TiO2/Polymer 50

ITO/TiO2/Polymer 250

ITO/In2O3/Polymer 50

ITO/In2O3/Polymer 250

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Poling Parameters using AJ-CKL1 E-O Polymer

Polarity: negative on top electrodeVoltage: 70V/μm (based on thickness of core material only)Voltage is turned on at the temperature of 25ºCVoltage is turned on at the temperature of 25 CTemperature: ramp at 10ºC/min from 25ºC to 135ºCDwell time at 135ºC: 30 secCool down from 135ºC to 25ºC within about 5-6 min.Voltage is turned off at the temperature of 25ºC

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Poling Process for AJ-CKL1/APC without buffer layer

Polymer thickness = 2.3 μm

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AJ-CKL1 Low TemperatureCurrent Peak

α γ

Double Current Peak in single layer polingTypically indicates a low temperature dipole alignment peak (α) followed yp y p p g p ( )by a higher temperature conduction peak (γ)These peaks are generally coincident in materials previously evaluated

α

γ

Double Current Peak in buffer layer polingPlot shows a much smaller peak for the 50 nm TiO2 buffer layerp 2 yNo discernable peaks in thicker TiO2 or either of the SiO2 samplesIndicates boundary charge layer is damping the signal

• Need to investigate boundary charge effect on dipole relaxation

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Poling Process for AJ-CKL1/APC With SiO2 Buffer Layer

Buffer : 50 nm SiO2Polymer : AJ-CKL1 in APC

Buffer : 280 nm SiO2Polymer : AJ-CKL1 in APC Polymer : AJ CKL1 in APC

Polymer thicknes = 2.4 μmPoling Voltage = 167V

yPolymer thicknes = 2.4 μmPoling Voltage = 167V

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Poling Process for AJ-CKL1/APC With TiO2 Buffer Layer

Buffer : 50 nm TiO2Polymer : AJ-CKL1 in APC

Buffer : 250 nm TiO2Polymer : AJ-CKL1 in APC Polymer : AJ CKL1 in APC

Polymer thicknes = 2.4 μmPoling voltage = 167V

yPolymer thicknes = 2.4 μmPoling voltage = 167V

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Experimental Results

r33 (pm/V) at 1310nm

S l Thi k ( ) #1 #2 #3 #4 AVGSample Thickness (nm) #1 #2 #3 #4 AVG

NB1 No Buffer-1 0 N/A 74.0 N/A 67.0 70.5

NB2 No Buffer-1 0 55.0 55.0 55.0 N/A 55.0

SI280H SiO2 280 40 0 42 2 46 6 40 0 42.2SI280H SiO2 280 40.0 42.2 46.6 40.0 42.2

SI50H SiO2 50 39.3 44.0 34.6 38.1 39.0

TI250H TiO2 250 N/A 85.0 N/A 82.0 83.5

TI50H TiO2 50 84.0 78.9 82.1 N/A 81.7

60 0

70.0

80.0

90.0

20.0

30.0

40.0

50.0

60.0

r33

(pm

/V)

0.0

10.0

20.0

NB1 NB2 SI280H SI50H TI250H TI50H Measured by Laboratory for Physical Science

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Preparation of Test Samples forConductivity Measurements

SampleBuffer

Thickness (nm)

Fabrication of buffer layers on ITO/Au coated glass substrates : by Northwestern Univ.Core (AJ-CKL1 in APC) provided by Univ. of Washington

ITO/Polymer 0

Au/Polymer 0

ITO/SiO2 50

Fabrication of polymer layer and gold electrodes : by AMRDEC, Redstone ArsenalConductivity measurements : by NAVAIR, China Lake

ITO/SiO2 280

ITO/TiO2 50

ITO/TiO2 250

ITO/In2O3 50

ITO/In2O3 250

Au/SiO2 50

Au/SiO2 280

Au/TiO2 50

Au/TiO2 250

3- 4 mm diameter

Au/In2O3 50

Au/In2O3 250

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Resistivity measurements by China Lake

FilmSample T avg V I avg R calc Thickness Resistivity *p g g y

(oC) (volts) (amps) (ohms) (cm) (ohm cm)TiO2 030408 25.7 26.85 1.10E-03 2.44E+04 3.84E-05 7.64E+07

132 2 26 85 1 11E-03 2 43E+04 3 84E-05 7 60E+07132.2 26.85 1.11E 03 2.43E 04 3.84E 05 7.60E 07

SiO2 030508 25.7 18.9 2.21E-07 8.56E+07 2.71E-05 3.80E+11135.3 18.9 7.88E-07 2.40E+07 2.71E-05 1.06E+10

Polymer 25.8 160.4 3.09E-07 5.19E+08 2.29E-04 2.72E+11AJCKL1 03 136.6 160.4 6.32E-04 2.54E+05 2.29E-04 1.33E+07

•Resistivity = (R calc) x (Electrode Area) / (Film Thickness)

•electrode diameter = 0.4 cm; electrode area = 0.12 cm2

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Effects of Blocking Layers in Nonlinear Optical Polymer PolingNonlinear Optical Polymer Poling

Michael Watson/NASA MSFC Ramarao Inguva/EWERamarao Inguva/EWE

Dielectric Constant and Conductivity yEffects on Core Voltage during Poling

Modeling of Experimental Results

Modeling UpdatesAtomic Basis of Maxwell Wagner Effect

Polymer/Polymer InterfaceMetal/Polymer Interfacey

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Dielectric Constant and Conductivity Effects on Core Voltage during Poling

Polymer stacks are capacitive voltage division circuits during poling

Charging between layers taking on the order of 1000 hours tosettle before stack relaxes to a resistive voltage divider

Dielectric Constant drives the division of voltage between the layers

Conductivity differences drive the polarity of charge build up at theConductivity differences drive the polarity of charge build up at the polymer/polymer interfaces

This charge layer enhances or degrades the core voltage

σBuffer > σcore : Enhancing

σBuffer< σcore : Degrading

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Dielectric Constant and Conductivity Effects on Core Voltage during Poling

Each polymer layer can be modeled as an RC circuit

The interface between each layer can also be modeled as an RC circuit to account for boundary charge effects

The combined RC values drive the circuit response during poling and modulation

Capacitance => Dielectric ConstantResistance => Conductivity

σB>σc σB<σc

Vp lower across Vp lower across

εB>εc

pcore; Enhanced

by boundary charge field

pcore; Degraded

by boundary charge field

Vp higher across Vp higher across

εB<εc

Vp higher across core; Enhanced

by boundary charge field

Vp higher across core; Degraded

by boundary charge field

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Modeling of Experimental Results

Northwestern University TiO2 films are much more conductive than those produced by sputtering at AMRDEC

σBNWU >> σBAMRDEC

Northwestern University SiO films are less than or equalNorthwestern University SiO2 films are less than or equal conductivity compared to those produced by sputtering at AMRDEC

σBNWU ≤ σBAMRDEC

Resulted in a shift in poling efficiency

AMRDECσSiO2_AMRDEC > σTiO2_AMRDEC

σSiO2 ≤ σcoreσTiO2 << σcore

NorthwesternσSiO2_NWU << σTiO2_NWU

σSiO2 ≤ σcoreσTiO2 ≥ σcore

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Modeling of Experimental Results

AMRDEC Sputtered Film Results (10/2007)

λ = 1.55 μm r13 (pm/V) Sample location 1 r13 (pm/V) Sample location 2 r13 (pm/V) Sample location 3

NOA  ‐3 ‐3 ‐3 σNOA ≤ σcoreNOA core

50 nm SiO2 not poled ‐14 ‐13 σSiO2 ≤ σcore

500 nm SiO2 ‐18 not poled ‐15 σSiO2 ≤ σcore

50 nm TiO2 ‐0.5 ‐0.4 ‐0.4 σTiO2 << σcore

h l l ( / )

2 TiO2 core

500 nm TiO2 ‐5 not poled not poled σTiO2 << σcore

Single  ‐10 ‐11 not poled

Northwestern Film Results (3/2008)

λ = 1.55 μm r13  (pm/V) r33  (pm/V)

280 nm SiO2 8 25 σSiO2 ≤ σcore

250 nm TiO2 13 47 σTiO2 ≥ σcore

No buffer 12 39

NotesPoling efficiency increases with buffer layer thicknessConductivities are still estimates and need to be accurately measured (within an order of magnitude)

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Modeling Results withAMRDEC Films

Core VoltageCore VoltageTiO2 buffer -103.7 V

Single Layer -105 VSingle Layer -105 VSiO2 buffer -118.5 V

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Modeling Results withNorthwestern Films

Core VoltageCore VoltageTiO2 buffer -169.4 V

Single Layer -168 VSingle Layer -168 VSiO2 buffer -165.7 V

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Atomic Basis of Maxwell-Wagner Boundary Charge Density

Reviewed article “Energy Level Alignment and Interfacial Electronic Structures at Organic/Metal and Organic/Organic Interfaces”Structures at Organic/Metal and Organic/Organic Interfaces , Advanced Materials, 1999.

Work Function mismatch (interface energy shift) forms the basis of the Maxwell Wagner Effectg

The level mismatches are reflected in the dielectric constant differences

Dielectric provides a measure of the charge storage capacity which is related to the molecular energy levelsgy

Polymer/Polymer layers are currently in the model as defined by the charge density equations (Gauss Law)

Electrode (Metal)/Polymer interface boundary charge density is being ( ) y y g y gincorporated

Investigating representation of this charge layer

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Conclusions on the Effects of Blocking Layers

Dielectric Constant main driver on core voltage during poling

C d ti it t ib t t h t d d ti f th liConductivity contributes to enhancement or degradation of the poling voltage across the core

Buffer layer fabrication processes affect the buffer layer conductivity and can dramatically affect the poling efficiencyand can dramatically affect the poling efficiency

Conductivity measurements of buffer layers need to be completed

Twin poling peaks indicate low temperature dipole alignmentp g p p p gNeed to investigate relaxationNeed to investigate affect of buffer layer on stability

Modeling updateModeling updateAtomic Basis of Maxwell Wagner Effect

Polymer/Polymer Interface already incorporatedMetal/Polymer Interface under investigationMetal/Polymer Interface under investigation

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Wideband Agile Receiver (WAR)

An integrated photonic electronic digital receiver

Application : RF sensing for war fightersApplication : RF sensing for war fighters

Approaches :Employing a photonics front end to provide flexibility in decentralizing RF sensors on a mobile platformUsing linearized modulators with high dynamic range to increase sensor

Program Manager :Charles Cerny, AFRL/RYRE

Prime Contractor :Lockheed Martin,

resolution.

Drawbacks in current technology :

Current system requirements are only up to 18 GHz. However, program goals could not be met by available components

Lockheed Martin, Newtown and Moorestown

by available components Linearization schemes involving electro- absorption modulators (EAM) result in performance trade-offs.

Solution : Modulators with high performance electro-optic polymers can improve the bandwidth and also compensate for the performance trade-offs. pTBD : Improvement in system performance with MORPH modulator.

WAR Photonics Architecture

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NASA Applications

NASA E l ti T h l D l t PNASA Exploration Technology Development Program (ETDP)

- Lunar Surface Systems- Orbital Communications/ Surface Positioning Systems

Rovers and surface infrastructure

High bandwidth surface communication relays

Orbital Communications/ Surface Positioning SystemsProgram Element Manager :Diane Hope, Langley Research Center

GPS corollary for moon and mars exploration support

Communication relay satellites

Space hardened navigation grade gyroscopes require low power consumption (< 15 W) and 0.01 deg/hr maximum drift.

High bandwidth (100 GHz ) modulators operating in space environments are required for communication.

High performance polymer modulators are potential candidatesHigh performance polymer modulators are potential candidates.


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