Testing of the Space Winds LIDAR Laser Transmitter Prototype Floyd Hovis, Fibertek, Inc. Jinxue Wang, Raytheon Space and Airborne Systems June 28, 2006

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

Status of Related Laser Development Programs CustomerApplication Required 1  m PerformanceProgram Status Univ. of NHDoppler Wind Lidar150 mJ at 50 HzDelivery complete NASA LangleyOzone DIAL1000 mJ/pulse at 50 HzDelivery complete Raytheon Doppler Wind Lidar1000 mJ at 50 HzTesting in progress Air ForceRemote Imaging Lidar500 mJ at 100 HzFinal build in progress NASA Langley Phase II SBIRSeed & Metrology Laser50 mW single frequencyPrototype demonstrated NASA LangleyHigh Spectral Res. Lidar IIP200 mJ at 200 HzPDR complete NASA LangleyMars exploration40 mJ at 20 HzFinal build in progress Navy SBIRRangefinder/Designator300 mJ at 25 HzSystem study underway NASA GSFCDoppler Wind Lidar IIP100 mJ at 200 HzSystem 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

Summary of Technical Approach An all solid-state diode-pumped laser transmitter featuring: Injection seeded ring laserImproves emission brightness (M 2 ) Diode-pumped zigzag slab amplifiersRobust 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 / boresightStable and reliable operation over stable 1.0  m cavity and optical benchenvironment Conduction cooledEliminates circulating liquids w/in cavity High efficiency third harmonic generationReduces on orbit power requirements Space-qualifiable electrical designReduces cost and schedule risk for a future space-based mission

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 Expansion telescope Amplifier #2 Amplifier #1 LBO doubler 355 nm output LBO tripler Fiber port Ring Resonator Fiber-coupled 1  m seed laser Optical isolator

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 TEM 00, M 2 =1.2 at 50 Hz  30 mJ TEM 00, M 2 =1.3 at 100 Hz  50 mJ square supergaussian, M 2 = 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 suppressor 2. Cube polarizer 3. Odd bounce slab 4. Steering wedge 5. /2 waveplate 6. Mode limiting aperture 7. RTP phase modulator 8. 45° Dove prism 9. Non-imaging telescope 10. RTP q-switch Seed Final Zerodur Optical Bench (12cm x 32cm)

Testing of Raytheon Wind Lidar Laser Is In Progress Completion of integrated laser and electronics modules for the BalloonWinds system in 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

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/diode drivers Analog and digital control board stack Seed laser

Performance of Ring Resonator in Raytheon Laser Transmitter Near field profile Beam quality data Oscillator was aligned for square supergaussian output. Output energy was Hz, M 2 was 1.4

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

Amplifier 1 and 2 Beam Quality Beam quality after amplifiers 1 and 2 was M x 2 = 1.9 and M y 2 = 1.9 for 530 mJ/pulse at 50 Hz

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 M 2 at 50 Hz 1020 mJ/pulse, 5.3 mm x 7.5 mm M x 2 = 3.6, M x 2 = 2.9, 910 mJ/pulse, 4.5 mm x 6.7 mm M x 2 = 2.5, M x 2 = mJ/pulse, 5.0 mm x 6.8 mm M x 2 = 3.2, M x 2 = 2.4,

COLD 1 WARMUP 2 FAULT 3 HPWR 6 LPWR 5 DIAG 7 ARMED 4 Power-up WARMUP FAULT ARMED LPWR HPWR DIAG ARMED LPWR HPWR DIAG LPWR HPWR DIAG CNTRL INITIALIZE CNTRL LASERDISARM CNTRL HTRSON CNTRL CLRINT CNTRL LASERARM CNTRL LPWRMODE CNTRL HPWRMODE CNTRL DIAGMODE CNTRL LPWRMODE CNTRL HPWRMODE CNTRL STOP WARMUP ARMED LPWR HPWR DIAG Any active fault “1” “4” “-” (hyphen) “D” “7” “2” “8” “C” “A” Blue text indicates alternative command characters when operating laser system from Hyperterminal serial interface Raytheon Laser Transmitter Modes and Power Consumption 28 W 32 W 687 W 87 W

COLD: Control electronics on Heaters off Faults suppressed Diode power supplies off All diode & QS pulses off WARMUP: THG and SHG heaters on Faults acknowledged Diode power supplies off All diode & QS pulses off FAULT: Active fault detected/latched Heaters on (unless heater fault is active) Diode power supplies off All diode & QS pulses off ARMED: THG and SHG heaters on THG and SHG at nominal temperatures Faults acknowledged Seed laser on Diode power supplies on All diode & QS pulses off HPWR: Heaters on Faults acknowledged Diode power supplies on All diode pulses on, nominal PW QS on Full optical output power (after ramp-up) LPWR: Heaters on Faults acknowledged Diode power supplies on All diode pulses on, nominal PW QS on Low optical output power DIAG: Heaters on Faults acknowledged Diode power supplies on All diode pulses on QS off No significant optical output Raytheon Laser Transmitter State Definitions

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 ( Hz) 1064 nm output was 687 W (27.7 V, 24.8 A) 6.6% system level wall plug 1064 nm Laser mass -43 kg Laser volume -10 cm x 42 cm x 69 cm = 29,000 cm 3 Preliminary 355 nm results Hz 2.2% system level wall plug 355 nm Expected 355 nm results -> Hz (>45% THG) >3% system level wall plug 355 nm

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 W average power W peak power 50% duty cycle W average power W peak power 100% duty cycle W average power W peak power

Raytheon Laser Transmitter Harmonic 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

Direct Detection Winds LIDAR Laser 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 Q and beyond at Raytheon. Demonstrate TRL 5 in 2006

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