Performance Testing of a Risk Reduction Space Winds Lidar Laser Transmitter Floyd Hovis, Fibertek, Inc. Jinxue Wang, Raytheon Space and Airborne Systems February 8, 2006

Approach to Developing Space- Qualified 355 nm Lasers 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 HzDelivery complete Air ForceRemote Imaging Lidar500 mJ at 100 HzTesting in progress NASA Langley Phase II SBIRSeed & Metrology Laser50 mW single frequencyPrototype demonstrated NASA LangleyHigh Spectral Res. Lidar IIP200 mJ at 200 HzFinal build in progress NASA LangleyMars exploration40 mJ at 20 HzDelivery complete Navy SBIRRangefinder/Designator300 mJ at 25 HzFinal build in progress NASA GSFCDoppler Wind Lidar IIP100 mJ at 200 HzFinal build in progress 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

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 Ring oscillator Amp #2 Power amp Amp #1

Solid Model of Integrated Laser Top View - Electrical Connection End Laser Optics Module (LOM) Laser Electronics Unit (LEU) LEU cooling plates LOM/LEU electrical interconnections 28 VDC terminals

Solid Model of Integrated Laser Top View - Optical Output End Laser Optics Module (LOM) Laser Electronics Unit (LEU) LEU cooling plates Output windows

Solid Model of Integrated Laser Bottom View Laser Optics Module (LOM) Laser Electronics Unit (LEU) LOM cooling plates Mounting foot

Acceptance Testing of Space Winds Lidar Laser Transmitter Is Complete Final acceptance testing was completed in November 2006 Space-Winds Lidar Laser Transmitter Design uses all three amplifiers Autonomous operation controlled through RS232 serial interface Nominal 28 VDC primary power Space-qualifiable electrical design Thermal control through conductive cooling to liquid cooled plates bolted to bottom of laser module 355 nm single frequency output of over Hz (23 W) Delivered system will undergo extended life testing at Raytheon Laser module Electronics module

Acceptance Testing 1064 nm Power & Energy Test Results 50 Hz operation Final 1064 nm power W (888 mJ/pulse) Input electrical power - 684W Wall plug efficiency - 6.5% 77% of final power is reached in 1 min 99% of final power is reached in 2 minutes Short term (20 s) shot to shot energy stability is 0.8% (3  ) Long term (30 min) energy stability is 3.7% (3  ) Pulse width - 14 ns

Acceptance Testing 355 nm Power & Energy Test Results 50 Hz operation Final 355 nm power W (478 mJ/pulse) Input electrical power - 684W 355 nm conversion efficiency % Wall plug efficiency - 3.5% 74% of final power is reached in 1 min 93% of final power is reached in 2 minutes Short term (20 s) shot to shot energy stability is 3.5% (3  ) Long term (30 min) energy stability is 4.3% (3  ) Pulse width - 14 ns

Acceptance Testing 1064 nm M 2 Near field profile Beam quality data M 2 x = 2.2 M 2 y = 2.3

Acceptance Testing 355 nm M 2 Near field profile Beam quality data M 2 x = 4.0 M 2 y =5.7

Acceptance Testing Pointing Stability 1064 nm data 355 nm data 1064 nm pointing stability < 64 µrad (<5% of raw beam divergence) 355 nm pointing stability < 71 µrad (<10% of raw beam divergence) Circle containing 90% of centroid values

Acceptance Testing 1064 nm Frequency Stability Frequency drift is < 1 MHz/min and appears to be dominated by seed laser frequency drift

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