Testing of the Space Winds LIDAR Laser Transmitter Prototype

1

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

2
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

3
Status of Related Laser Development Programs
Single frequency laser development has a broad
support base
Customer Application Required 1 mm
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
4
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 mm 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
5
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
6
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 Hz
• 30 mJ TEM00, M2 1.3 at 100 Hz
• 50 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

Final Zerodur Optical Bench (12cm x 32cm)
7
Testing of Raytheon Wind Lidar Laser Is In
Progress
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
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
8
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
Seed laser
Analog and digital control board stack
DC-DC converters/diode drivers
Interior view of the Laser Electronics Unit
9
Performance of Ring Resonator in Raytheon Laser
Transmitter
Beam quality data
Near field profile
Oscillator was aligned for square supergaussian
output. Output energy was 60 mJ _at_ 50 Hz, M2 was
1.4
10
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

Input beam profile
Output beam profile
11
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
12
Amplifier 3 Performance
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, Mx2
2.9,
970 mJ/pulse, 5.0 mm x 6.8 mm Mx2 3.2, Mx2
2.4,
910 mJ/pulse, 4.5 mm x 6.7 mm Mx2 2.5 , Mx2
2.5
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.
13
Raytheon Laser TransmitterModes and Power
Consumption
Power-up
WARMUP FAULT ARMED LPWR HPWR DIAG
Blue text indicates alternative command
characters when operating laser system from
Hyperterminal serial interface
CNTRL INITIALIZE
1
COLD 1
HPWR 6
687 W
28 W
CNTRL HPWRMODE
C
CNTRL HPWRMODE
ARMED LPWR HPWR DIAG
CNTRL HTRSON
C
CNTRL LASERDISARM
4
CNTRL LPWRMODE
D
87 W
A
WARMUP 2
LPWR 5
ARMED 4
CNTRL LPWRMODE
CNTRL LASERARM
687 W
32 W
A
7
CNTRL STOP
CNTRL CLRINT
2
CNTRL DIAGMODE
- (hyphen)
8
LPWR HPWR DIAG
FAULT 3
DIAG 7
687 W
WARMUP ARMED LPWR HPWR DIAG
Any active fault
14
Raytheon Laser TransmitterState Definitions
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 Heate
rs 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
15
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 _at_ 50 Hz) 1064 nm
• output was 687 W (27.7 V, 24.8 A)
• 6.6 system level wall plug efficiency _at_
  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 _at_ 50 Hz
• 2.2 system level wall plug
  efficiency _at_ 355 nm
• Expected 355 nm results - gt410 mJ _at_ 50 Hz (gt45
  THG)
• gt3 system level wall plug
  efficiency _at_ 355 nm

16
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
17
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

18
Direct Detection Winds LIDARLaser Transmitter
Status in 2006

• Demonstrated gt900 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
• gt45 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
19
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