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FIBERTEK, INC.
Testing of the Space Winds LIDAR Laser Transmitter Prototype
Floyd Hovis, Fibertek, Inc.
Jinxue Wang, Raytheon Space and Airborne Systems
June 28, 2006
FIBERTEK, INC.
Program Overview
Develop a robust, single frequency 355 nm laser for airborne and space-based direct detection wind lidar systems
–All solid-state, diode pumped–Robust packaging–Tolerant of moderate vibration levels during operation–Space-qualifiable design
Incorporate first generation laser transmitters into ground-based and airborne field systems to demonstrate and evaluate designs
–Goddard Lidar Observatory for Winds (GLOW)–Balloon based Doppler wind lidar being developed by Michigan Aerospace and the University of New Hampshire for NOAA
Develop scaling to higher powers and pulse energies–Raytheon funded Space Winds Lidar Risk Reduction Laser Transmitter–Air Force SBIR to develop a 500 mJ, 100 Hz 1064 nm pump source
Iterate designs for improved compatibility with a space-based mission–Lighter and smaller–Radiation hardened electronics
FIBERTEK, INC. Status of Related Laser Development Programs
Customer Application Required 1 m Performance Program Status
Univ. of NH Doppler Wind Lidar 150 mJ at 50 Hz Delivery complete
NASA Langley Ozone DIAL 1000 mJ/pulse at 50 Hz Delivery complete
Raytheon Doppler Wind Lidar 1000 mJ at 50 Hz Testing in progress
Air Force Remote Imaging Lidar 500 mJ at 100 Hz Final build in progress
NASA Langley Phase II SBIR Seed & Metrology Laser 50 mW single frequency Prototype demonstrated
NASA Langley High Spectral Res. Lidar IIP 200 mJ at 200 Hz PDR complete
NASA Langley Mars exploration 40 mJ at 20 Hz Final build in progress
Navy SBIR Rangefinder/Designator 300 mJ at 25 Hz System study underway
NASA GSFC Doppler Wind Lidar IIP 100 mJ at 200 Hz System study underway
Single frequency pump head & resonator technology will support a significant number of next generation lidar applications
Single frequency laser development has a broad support base
FIBERTEK, INC.
Summary of Technical Approach
An all solid-state diode-pumped laser transmitter featuring:
Injection seeded ring laser Improves emission brightness (M2)
Diode-pumped zigzag slab amplifiers Robust and efficient design for use in space
Advanced E-O phase modulator material Allows high frequency cavity modulation for improved stability injection seeding
Alignment insensitive / boresight Stable and reliable operation over stable 1.0 m cavity and optical bench environment
Conduction cooled Eliminates circulating liquids w/in cavity
High efficiency third harmonic generation Reduces on orbit power requirements
Space-qualifiable electrical design Reduces cost and schedule risk for a future space-based mission
FIBERTEK, INC. Raytheon 1 J Risk Reduction Laser Optical Layout
Final System Optical Configuration
Both the original NASA Ozone amplifiers and the power amplifier have been shown to be capable of 100 Hz operation
Power amplifier
Expansiontelescope
Amplifier #2
Amplifier #1
LBO doubler
355 nm output
LBO tripler
Fiber port
Ring Resonator
Fiber-coupled 1 m seed laser
Optical isolator
FIBERTEK, INC. Packaged Single Frequency Laser Ring Laser Design Has Been Validated
Optical Schematic
Design Features
Near stable operation allows trading beam quality against output energy by appropriate choice of mode limiting aperture
30 mJ TEM00, M2 =1.2 at 50 Hz30 mJ TEM00, M2 =1.3 at 100 Hz50 mJ square supergaussian, M2 = 1.4 at 50 Hz
Injection seeding using an RTP phase modulator provides reduced sensitivity to high frequency vibration PZT stabilization of cavity length reduces sensitivities to thermal fluctuations Zerodur optical bench results in high alignment and boresight stability
1. Reverse wave suppressor2. Cube polarizer3. Odd bounce slab4. Steering wedge5. /2 waveplate6. Mode limiting aperture7. RTP phase modulator8. 45° Dove prism9. Non-imaging telescope10. RTP q-switch
1 2 3 4 5 6 2
2 4 9 5 8 5 7 2
5
10
Seed
Final Zerodur Optical Bench (12cm x 32cm)
FIBERTEK, INC. Testing of Raytheon Wind Lidar Laser Is In Progress
Completion of integrated laser and electronics modules for the BalloonWinds systemin 2005 validated many of the key elements of the Raytheon design in a packaged unit
Injection seeded single frequency ring oscillator
Key mechanical design features
High voltage power supply design
Diode drive electronics
Control electronics printed circuit boards and software
User interface
Thermal control through conductive cooling
Space-Winds Lidar Laser Transmitter
FIBERTEK, INC.
Control and Power Electronics
Raytheon Wind Lidar laser transmitter electrical design has same control electronics as BalloonWinds and updated power supplies for increased power operation
Interior view of the Laser Electronics Unit
DC-DC converters/diod
e drivers
Analog and digital control board stack
Seed laser
FIBERTEK, INC. Performance of Ring Resonator in Raytheon Laser Transmitter
Near field profile Beam quality data
Oscillator was aligned for square supergaussian output.Output energy was 60 mJ @ 50 Hz, M2 was 1.4
FIBERTEK, INC. Amplifier 1 and 2 Performance
50 Hz Testing of 1-sided pumped amplifiers 1 & 2
Dual single sided pumped amplifiers were used as the first stage of the Raytheon laser transmitter - Recent modeling showed slab bending in 1-sided pumped amplifiers is not as severe as originally believed - NASA Ozone amplifier is pump on bounce approach with only 1 array at each bounce point
Dual amplifiers operated with 75 W peak optical power per bar and 130 µs pump pulses generated 530 mJ/pulse with well a behaved near field spatial profile
Output beam profile
Input beam profile
FIBERTEK, INC. Amplifier 1 and 2 Beam Quality
Beam quality after amplifiers 1 and 2 was Mx2 = 1.9
and My2 = 1.9 for 530 mJ/pulse at 50 Hz
FIBERTEK, INC. Amplifier 3 Performance
Amplifier 3 exhibited a relatively sudden decrease in beam quality as the extracting beam was expanded to achieve higher powers. Filling the amplifier to achieve slightly over 900 mJ/pulse
is a good compromise to achieve both high pulse energies and good beam quality.
Output energies, beam sizes, near field profiles, and M2 at 50 Hz
1020 mJ/pulse, 5.3 mm x 7.5 mm
Mx2 = 3.6, Mx
2 = 2.9, 910 mJ/pulse, 4.5 mm x 6.7 mm
Mx2 = 2.5 , Mx
2 = 2.5
970 mJ/pulse, 5.0 mm x 6.8 mm
Mx2 = 3.2, Mx
2 = 2.4,
FIBERTEK, INC.
COLD1
WARMUP2
FAULT3
HPWR6
LPWR5
DIAG7
ARMED4
Power-up WARMUPFAULTARMEDLPWRHPWRDIAG
ARMEDLPWRHPWRDIAG
LPWRHPWRDIAG
CNTRL INITIALIZE
CNTRL LASERDISARMCNTRL HTRSON
CNTRL CLRINT
CNTRL LASERARM CNTRL LPWRMODE
CNTRL HPWRMODE
CNTRL DIAGMODE
CNTRL LPWRMODE
CNTRL HPWRMODE
CNTRL STOP
WARMUPARMEDLPWRHPWRDIAG
Any activefault
“1”
“4”
“-” (hyphen)
“D”
“7”
“2”
“8”
“C”
“C”
“A”
“A”
Blue text indicates alternative command characters when operating laser system from Hyperterminal serial interface
Raytheon Laser TransmitterModes and Power Consumption
28 W
32 W
687 W
687 W
687 W
87 W
FIBERTEK, INC.
COLD:Control electronics onHeaters offFaults suppressedDiode power supplies offAll diode & QS pulses off
WARMUP:THG and SHG heaters onFaults acknowledgedDiode power supplies offAll diode & QS pulses off
FAULT:Active fault detected/latchedHeaters on (unless heater fault is active)Diode power supplies offAll diode & QS pulses off
ARMED:THG and SHG heaters onTHG and SHG at nominal temperaturesFaults acknowledgedSeed laser onDiode power supplies onAll diode & QS pulses off
HPWR:Heaters onFaults acknowledgedDiode power supplies onAll diode pulses on, nominal PWQS onFull optical output power (after ramp-up)
LPWR:Heaters onFaults acknowledgedDiode power supplies onAll diode pulses on, nominal PWQS onLow optical output power
DIAG:Heaters onFaults acknowledgedDiode power supplies onAll diode pulses onQS offNo significant optical output
Raytheon Laser TransmitterState Definitions
FIBERTEK, INC. Raytheon Laser Transmitter Measured System Performance
Current system, 100% duty cycle, 50 Hz operation
Total DC power consumption (nominal 28 V) at 45.6 W (912 mJ/pulse @ 50 Hz) 1064 nm
output was 687 W (27.7 V, 24.8 A)
6.6% system level wall plug efficiency @ 1064 nm
Laser mass - 43 kg
Laser volume - 10 cm x 42 cm x 69 cm = 29,000 cm3
Preliminary 355 nm results - 300 mJ @ 50 Hz
2.2% system level wall plug efficiency @ 355 nm
Expected 355 nm results - >410 mJ @ 50 Hz (>45% THG)
>3% system level wall plug efficiency @ 355 nm
FIBERTEK, INC. Raytheon Laser Transmitter Alternate Duty Cycle Operation
Measured 1064 nm output during typical Off/On cycle
“Off” operation is in Armed mode (87 W)
“On” operation in HPWR mode (687 W)
88% of full power is reached in 1.5 minutes
93% of full power is reached in 2 minutes
10% duty cycle - 147 W average power - 687 W peak power
50% duty cycle - 387 W average power - 687 W peak power
100% duty cycle - 687 W average power - 687 W peak power
1064 nm power vs. time after Armed to High Power transition
Time (minutes)
0 2 4 6
1064 nm output power (W)
0
10
20
30
40
50
FIBERTEK, INC. Raytheon Laser TransmitterHarmonic Generation Status
Second harmonic generation - 25 mm Type I LBO
- Achieved 31.4 W of 532 nm output from 45.6 W of 1064 nm input
- 69% conversion efficiency
Third harmonic generation with 10 mm Type II LBO- Achieved 13 W of 355 nm output from 45.6 W of 1064 nm input
- 28% conversion efficiency
Third harmonic generation with 25 mm Type II LBO- Achieved 15 W of 355 nm output from 45.6 W of 1064 nm input
- 33% conversion efficiency
Results suggest back conversion may be occurring in 25 mm THG crystal
Additional modeling and tests are underway to clarify lower than expected THG
FIBERTEK, INC. Direct Detection Winds LIDARLaser Transmitter Status in 2006
Demonstrated >900 mJ/pulse from a single frequency 1064 nm pump laser operating at 50 Hz
with good beam quality
Demonstrated 33% conversion to 355 nm to achieve 300 mJ/pulse at 50 Hz >45% conversion still anticipated
Acceptance testing of risk reduction engineering model in a space qualifiable, conductively cooled
package in July
Amplifier tests to demonstrate scaling to 100 Hz in August with Air Force SBIR funding
Performance characterization and testing at Raytheon Space and Airborne Systems in Q3 of 2006
Life testing and characterization in Q4 2006 and beyond at Raytheon.
Demonstrate TRL 5 in 2006
FIBERTEK, INC.
Acknowledgements
BalloonWinds laser transmitter was funded by NOAA BalloonWinds
Program through UNH and MAC
Space Doppler Winds LIDAR risk-reduction laser transmitter was funded by
Raytheon Internal Research and Development (IRAD)
NASA support through the SBIR and Advanced Technology Initiative
programs
Air Force SBIR funding for 100 Hz laser development