electronically-steerable, coherent laser arrays · 2011. 5. 14. · narrowline, kilowatt-class...
TRANSCRIPT
Electronically-Steerable, Coherent Laser ArraysREALLY Small, Lightweight, High Power Lasers for DoD Applications
Electronically-Steerable, Coherent Laser ArraysREALLY Small, Lightweight, High Power Lasers for DoD Applications
MTO SymposiumJoseph Mangano, PM
March 7, 2007
MTO SymposiumJoseph Mangano, PM
March 7, 2007
Report Documentation Page Form ApprovedOMB No. 0704-0188
Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering andmaintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information,including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, ArlingtonVA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if itdoes not display a currently valid OMB control number.
1. REPORT DATE 07 MAR 2007
2. REPORT TYPE N/A
3. DATES COVERED -
4. TITLE AND SUBTITLE Electronically-Steerable, Coherent Laser Arrays REALLY Small,Lightweight, High Power Lasers for Do DApplications
5a. CONTRACT NUMBER
5b. GRANT NUMBER
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) 5d. PROJECT NUMBER
5e. TASK NUMBER
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) DARPA
8. PERFORMING ORGANIZATIONREPORT NUMBER
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT NUMBER(S)
12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution unlimited
13. SUPPLEMENTARY NOTES DARPA Microsystems Technology Symposium held in San Jose, California on March 5-7, 2007.Presentations, The original document contains color images.
14. ABSTRACT
15. SUBJECT TERMS
16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT
UU
18. NUMBEROF PAGES
23
19a. NAME OFRESPONSIBLE PERSON
a. REPORT unclassified
b. ABSTRACT unclassified
c. THIS PAGE unclassified
Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18
Solid-StateLaser
Amplifier
Diode-Pumped, Solid-State Laser Systems
θDL(M2 = 1)
Divergence Angle = θ = M2 θDL
θLaser Diode
Array
Prime Power, Pprime
ηLDA ηSSL Atmospheric Transmission– Turbulence (including aero-optics)– Absorption (molecular/aerosol)
TargetIrradiance(watts/cm2)
AdaptiveOptics
Power Delivery Efficiency ~ ηLDA ηSSL ηBDM4
Challenges– Power Scaling– Efficiency– Beam Quality– Size and Weight– Lifetime/Reliability– Electronically-steered, Conformal,
Adaptive, Optical Phased Arrays
Solid-StateLaser
Amplifier
Beam Director
(Diameter D)
Beam Director
(Diameter D)
ηBD
Technologies:– Electronically-Steered, Optical Phased Arrays
driven by:– Fiber Laser Amplifiers (APPLE)
or directly by:– Coherent Laser Diode Arrays (COCHISE)
Challenge: Electronically-Steered 100 kW Laser System at 2 kg per kilowatt
APPLE Laser Beam Directors Adaptive Photonic Phase-Locked Elements
APPLE Laser Beam Directors Adaptive Photonic Phase-Locked Elements
All-Electronic Beam Steering with 45o Field-of-Regard
Power and Aperture Size Scaling through Coherent Beam Combining of Multiple Sub-apertures (2.5 - 5 cm dimension)
Conformal to Most Military Platforms– replaces aerodynamically-challenged turret-mounted beam directors
Near-Diffraction-Limited Beam Quality, Corrected for:– atmospheric turbulence – aero-optic effects
APPLE Beam Director Technology can provide:
Fast, Electronically-Steered, Optical Phased Array adaptable to essentially all DoD Laser Applications
− ro ~ 5 mm/ BWatm ~ 1 kHz− ro ~ 5 cm / BWatm ~ 10 kHz
4
APPLEAdaptive Photonic Phase-Locked Elements
Lasercom Links Multi-target Search and TrackTarget ID
Laser Countermeasures
Laser Weapon Laser Sensing
Multiple, Conformal, Electronically-Steered SubaperturesIndependently Targeted or Coherently Combined into a Single Beam
Illuminator-Laser
Power-in-the-Bucket Metric
Controller(Global SPGD)
Phase-Lock
Control Loop
Phase-Locked,CompensatedSub-apertures
Seed-Laser
LiNbO3Phase, Intensity& Polarization
Controllers
Fiber Pre-Amplifier
High-PowerFiber AmplifierReceiver
Adaptive Optic Control Loop(tip-tilt, LC HEX 127)
APPLE ConceptAPPLE Concept
Target
Atmospheric Turbulence
Assembled APPLE SubapertureAssembled APPLE Subaperture
Adaptive Optic
Beam Expanding Telescope
100W Fiber Lase Feed
PZT Actuatorfor Tip-Tilt
Zone Fill OPAs
Zone Select OPAs
BraggGratings
100 W Fiber Laser Feed
Challenge: Coherent Array of APPLE Subapertures with Fast Adaptive Optics
Electronic Beam Steering
100 Coherently-Combined Apertures (10 x 10 Array)Need High Power Fiber Laser Amplifiers– 2 kW – Single Transverse Mode– Single Polarization– < λ/20 Phase Noise – No SBS/SRS - Narrowline
These 2 kW Fiber Laser Amplifiers do not exist– 200 watts Commercially Available
Weapon Concepts Require Single-Mode,Narrowline, Kilowatt-Class Fiber LasersWeapon Concepts Require Single-Mode,Narrowline, Kilowatt-Class Fiber Lasers
50 cm
200 kW Phased Array
APPLEArray
Element
5 cm
Fiber LaserAmplifier
Narrowline FiberLaser Oscillator
Challenge: Scale these Fiber Amplifiersto 2 kW and Beyond
Why Coherent Diode Arrays?– Electrical Efficiency
– Thin Disk Lasers (HELLADS) 15%– Fiber Lasers 25-30%– Coherent Laser Diode Arrays 30-50%
Three Approaches:
– Talbot Cavity – Spatially-Coupled Oscillators in Supermode– Phase-Locked Loops driven from a common seed beam– Coherent Combining with SPGD Algorithm as in APPLE
IncreasingRisk
Coherent, High PowerLaser Diode Arrays
Challenge: Coherently Combine Kilowatt Laser Diode Arrays
Challenge: Coherently Combine Kilowatt Laser Diode Arrays
Remove Multi-Mode, UnphaseableRogue Emitters in 10s of nsec
SlabConfining Layer
Slab-Coupled Optical Waveguide Laser(SCOWL)
SlabConfining Layer
Coherent Output Beam
::
N-elementDiode Array
TalbotCavity
MaxReflector
Partial Reflector
w
dzT/2 = 2 d 2/λ
N-elementDiode Array
TalbotCavity
MaxReflector
Partial Reflector
w
dzT/2 = 2 d 2/λ
MaxReflector
Partial Reflector
w
dzT/2 = 2 d 2/λ
Partial Reflector
w
ddzT/2 = 2 d 2/λ
Partial Reflector
zT/2 = 2 d 2/λ ~ 2 cm
Talbot Cavity
1 cmw
d
N-element Single -ModeDiode Array
VBG
::
N-elementDiode Array
TalbotCavity
MaxReflector
Partial Reflector
w
dzT/2 = 2 d 2/λ
N-elementDiode Array
TalbotCavity
MaxReflector
Partial Reflector
w
dzT/2 = 2 d 2/λ
MaxReflector
Partial Reflector
w
dzT/2 = 2 d 2/λ
Partial Reflector
w
ddzT/2 = 2 d 2/λ
Partial Reflector
zT/2 = 2 d 2/λ ~ 2 cm
Talbot Cavity
1 cmw
d
N-element Single -ModeDiode Array
VBG
Partial Reflector
zT/2 = 2 d 2/λ ~ 2 cm
Talbot Cavity
1 cmw
d
N-element Single -ModeDiode Array
VBG
Talbot Cavity - Laser Diode Phased Array
Indium bump bondsIndium bondSCOWL Wafer Carrier
Common Heat Sink
SCOWL Array
SiCMOS Driver Circuit
~ 0.3 mm
SCOWL Wafer Carrier
12 mm
Common Heat Sink
SCOWL Array
SiCMOS Driver Circuit
~ 3 mm Side View
Individually drive Each Emitter in the Bar
LightOut
Diffraction-Limited Bar1 wattSingle ModeUltra-low Noise
N-element Single-ModeDiode Array
Drive each Emitter in SCOWL BarIndependently
Drive each Emitter in SCOWL BarIndependently
Independent Drivers for Each Emitter in a 10-Emitter Bar
Challenge: CMOS Drivers Conformally CoupledDirectly to the Diode Bar for Current Sharing and Phase Control
12
10
8
6
4
2
020151050
Current (A)C
W O
utpu
t Pow
er (W
)
980-nm COCHISE ArrayIQE-OMVPE-36, Wafer #5, Bar #2, Array #12100 µm pitch, 10 elements, ind. addr.All 10 elements on Facet Coatings R=95%/0%External Mirror R=4%, 15 µm from facetT = 5° C11/22/06
6 µm
Device 5, 0.9 A, no mirror
12
10
8
6
4
2
020151050
Current (A)C
W O
utpu
t Pow
er (W
)
980-nm COCHISE ArrayIQE-OMVPE-36, Wafer #5, Bar #2, Array #12100 µm pitch, 10 elements, ind. addr.All 10 elements on Facet Coatings R=95%/0%External Mirror R=4%, 15 µm from facetT = 5° C11/22/06
6 µm
Device 5, 0.9 A, no mirror
Vertically-Coupled Large Area (VECLA) LaserVertically-Coupled Large Area (VECLA) Laser
PerformanceVery low optical internal loss (<0.2 cm-1)
Very low electrical resistance, but not too low
Very low thermal resistance (~2oC/watt-mm)
Design FeaturesLow modal overlap to doped layers (<0.02)
Highly doped cladding layers (~1018 cm-3)
Thin top cladding layer (~0.05µm)
Large optical mode (~4 x 15 µm2)
Challenge: 10 watt, low noise, single-mode emitters at 50% Efficiency
APPLE Sub-aperture driven bya Coherent Laser Diode Array
SPGDAlgorithm
TARGETSCOWLArray
THERMALMANAGEMENT
PRIMEPOWER
DIODEARRAYSDIODE
ARRAYSDIODE
ARRAYSTHERMAL
MANAGEMENT
PRIMEPOWER
Potential: 100 kW Laser Systems at 2 kilograms per kilowatt!
APPLE Sub-aperture driven by a Fiber Laser Amplifier
CalibratingDetector
Array
Overall Electrical Efficiency ~ 30-50% !Liquid Crystal, Fast, Ultra-Wide-Angle Electronic Steer
SPGDAlgorithm
FIBER LASER
TARGET
Liquid CrystalAdaptive Optic
Liquid Crystal, Fast, Ultra-Wide-Angle Electronic Steer
LiNbO3Phase Shifter
FIBER OSCILLATOR
VBG
Additional Challengesand Areas of Interest
Additional Challengesand Areas of Interest
Laser Diode Technology – for pumping Thin Disk Lasers• Increase SHEDS Diode Bar Power to ≥ 100 watts/bar-cm
– Efficiency ≥ 70%– Lifetime > 1000 hours– 1 cm bar with 1.5 mm pitch– Wavelength ~ 808nm (Nd:YLF or Nd:ceramic YAG Pump)
• Thermal Resistance from Junction to Heat Sink is the limiting factor
Fiber Laser Technology – 100 kW • Explore Ultimate Fiber Amplifier Array Scaling Limits
– Single-Mode (M2 < 1.5)– Single-Polarization
• Pump Diode Brightness is the limiting factor
Some ofMy Current Program Responsibilities
Some ofMy Current Program Responsibilities
Existing Programs:– APPLE – Conformal Laser Beam Director – COCHISE – Coherent Combining of Laser Diodes
ADHELS Single-Mode Laser Diode Development Laser Diode Reliability and Lifetime
– SHEDS – Laser Diode Efficiency
– Ultrabeam – X-ray Lasers
– Nanowriter – E-Beam, Direct-Write, Maskless Lithography Tool
– IM-VAC (DSO) – Compact CT Imaging Technology for Battlefield Use
Posters
Briefed Today
….so see Dr. John Zolper, Director of MTO now!!!Get Recruited as a New MTO Program Manager
Back ups
APPLET ComponentsAPPLET Components
Tip/Tilt Compensator
(HEX 127)
Tip/Tilt Compensator
Fast Beam Steering Element Adaptive Optics Element
LiNO3 Electric Field Controller
• Intensity
• Phase
• Polarization
APPLET
SPGD Algorithmimplemented on FPGA
Fiber Laser Amplifier
Challenge: – 10x Faster Adaptive
Optic Elements
Phase-Locked Looparound a SCOWL Amplifier
Phase-Locked Looparound a SCOWL Amplifier
0 100 200 300 4005806006206406606807007207400.0
0.1
0.2
0.3
0.4
0.5
0.6
SCO
WA
cur
rent
(mA
)Time (sec)
Phas
e (w
aves
)
seed laser SCOWA
λ/2 λ/4
λ/2
NP
NP
Pol.
P.D. (I)
P.D. (Q)
P.D.
+-
Pol.
seed laser SCOWA
λ/2 λ/4
λ/2
NP
NP
Pol.
P.D. (I)
P.D. (Q)
P.D.
+-+-
Pol.
Mach Zehnder Interferometer measures Phase for Feedback Control
1 wave per 180 mA of Diode Current
<5GHzBandwidth
Stabilized Diode Amplifier Output Phase to 0.01 waves at 1 µm!Challenge: Coherent Array of High Power Laser Diode Amplifiers at 2 kW
500 mW SCOWL Amplifier OpenLoop
ClosedLoop
Phase Noise
(rad/√Hz)
Integrated Phase Noise
(rad)
10-1 100 101 102 103 10410-5
10-4
10-3
10-2
10-1 SCOWA#3 @300mA, 15mW seed SCOWA#3 @700mA, 15mW seed SCOWA#3 @1000mA, 15mW seed
SCOWA #4 @300, 700, & 1000mA
Phas
e N
oise
(rad
/Hz1/
2 or r
ad.)
Frequency (Hz)
SCOWA Phase Noise
COCHISE Diode Protection Technology Accelerated Diode Bar Lifetest
Rare Rogue Events Lead to Catastrophic Damage
in Diode Bar
Eliminating Rogue Modes extends Diode Bar Lifetime by >10xNo Impact on Average Power or Efficiency
Fault Mode Frequency increases with Diode Bar Current
Protected UnprotectedExtend Laser Diode Bar Lifetime
Detect Fault Modes from the ElectricalTerminals of the Diode BarCut Power to the Diode Bar within 1 µsecWait for 300 µsec and Re-apply Power to the Bar
Unprotected Fault Mode Protect
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0 50 100 150 200 250
Nor
mal
ized
Opt
ical
Pow
er
0
5
10
15
20
25
Faul
ts (
x 1
04 )
Shots ( x 106)
Lifetest terminated
120A50%
130A62.5%
150A75%
30 hours13 hours
Unprotected Fault Mode Protect
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
0 50 100 150 200 250
Nor
mal
ized
Opt
ical
Pow
er
0
5
10
15
20
25
Faul
ts (
x 1
04 )
Shots ( x 106)
Lifetest terminated
120A50%
120A50%
130A62.5%130A62.5%
150A75%
150A75%
30 hours13 hours
Fault Protected
Efficiency = 50% 70% SHEDS=
Cochise Program Goals
Lifetime = 10 – 100 hours >1000 hrsfor HELLADS and SHEDs
High Power per Bar = 85 watts/bar for HELLADS then >100 watts/bar
Coherent Combination = No Yes
COCHISERevolutionizing Laser Diode Bar Technology
Unique COCHISE Diode ProtectionExtends Diode Lifetime by >10x
Diode Beam Quality = 35x Diffraction Limit< 1.4x Diffraction Limit
Brightness and
Coherence
GEN3 Fault ProtectionHELLADS Phase 4
+
+
Cochise will increase Power and Safe Operating Temperature of Laser Diode Bars
Cochise will increase Power and Safe Operating Temperature of Laser Diode Bars
In Year 2, COCHISE will Extend HELLADS Diode Bar Lifetime at Higher:– Diode Bar Power 85 Watts >100 Watts– Inlet Coolant Temperatures 35oC >50oC
Reduce Laser Weapon System Size, Weight, and Cost– Impacts:
• HELLADS Phase 4 • DARPA Fiber Laser Program• All DoD Diode-Pumped Solid State Laser Programs
Challenge: 200 watts/bar-cm by Combining Diode Protection with Improved Bar Cooling Technology
Phase I
24 mo
Phase II
30 mo
Phase 0
12 mo
10
100
1
Pow
er p
er A
pert
ure
(wat
ts)
1000
Hig
h Po
wer C
omp
Dev
elop
High Power Array Development
Algorithms, Atmospherics
Low-power Testbed at ARL
Single aperture- Wide-angle- Adaptive Optics- 100 Watt- 25 mm φ
Demonstrates:- Power Scaling- SPGD Control- Adaptive Optics- 45° FOR
Single aperture- Adaptive Optics- 1000 Watt- 50 mm φ
7 Subapertures- Adaptive Optics- @ 50 mm φ- Wide-angle- @ 200 W
19 Subapertures- Adaptive Optics- @ 50 mm φ- Wide-angle- @ 1 kW
High Power Testing
at AFRL Kirtland
Proposed RoadmapProposed Roadmap
7 Subapertures- Adaptive Optics- @ 25 mm φ- @ 10 W?
Technologies– Conformal Phased Array – Risley Prisms– Gimballed
Programs– HELLADS (TTO) – HPFL (TTO) – ADHELS/COCHISE
Technologies– Thin Disks – Fiber – Coherent Diode Arrays
Challenges– Scalability– Efficiency – Beam Quality/Coherence – Size, Weight, Power
Solid-State Laser Amplifiers
Beam Directors
Program– APPLE
Challenges– Efficient– All-Electronic Steering– Scalable to High Power
and Aperture Size– Conformal to Platform – Minimum Size/Weight
Technologies– High Efficiency Edge/VCSEL/QD Emitters– Slab-Coupled Optical Waveguide
SE-Distributed Feedback– Intelligent Diode Protection
Technologies– Thin Disks – Fiber Lasers– Direct Diode Drive
– Coherently-Combined Diode Arrays– Spectrally-Combined Diode Arrays j
Technologies– Conformal Phased Array
Solid-StateLaser
Amplifier
Diode-Pumped, Solid-State Laser Systems
θDL(M2 = 1)
Divergence Angle = θ = M2 θDL
θLaser Diode
Array
Prime Power, Pprime
ηLDA ηSSL Atmospheric Transmission– Turbulence (including aero-optics)– Absorption (molecular/aerosol)
TargetIrradiance(watts/cm2)
AdaptiveOptics
Power Delivery Efficiency ~ ηLDA ηSSL ηBDM4
Challenges– Power– Efficiency– Beam Quality– Size and Weight– Lifetime/Reliability– Electronically-steered, Conformal
Optical Phased Arrays with AO
Programs– SHEDS– ADHELS/COCHISE
Laser Diodes
Solid-StateLaser
Amplifier
Programs– HELLADS (TTO) – HPFL (TTO) – ADHELS/COCHISE
Solid-State Laser AmplifiersBeam Directors
Program– APPLE
Beam Director
(Diameter D)
Beam Director
(Diameter D)
ηBD
Agenda:
– APPLE Beam Directors– COCHISE Coherent Diode Arrays– Coherent Diode Arrays integrated with APPLE– Challenges