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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.
