FIBERTEK, INC.

Progress On Laser Transmitters For Direct Detection Wind Lidars

Floyd Hovis, Fibertek, Inc.

Jinxue Wang, Raytheon Space and Airborne Systems

Michael Dehring, Michigan Aerospace Corp.

Jan 18, 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 Risk Reduction Laser–Air Force SBIR to develop a 1 J, 100 Hz 1064 nm pump source

Iterate designs for improved compatibility with a space-based mission–Lighter and smaller–Radiation hardened electronics

Fibertek Laser/LIDAR Expertise- Many NASA and DOD SBIRS- Extensive experience in fieldable single frequency laser transmitter development

Raytheon Laser/LIDAR Expertise- Over 30,000 laser/lidar systems for DOD- Leader in engineering & packaging rugged laser/LIDAR systems for air and space- Significant IRAD investment

A space-qualifiable laser in the same form and factor

as the flight laser!

FIBERTEK, INC.

Related Laser Programs at Fibertek

Customer Application Required 1 m Performance Program Status

Raytheon Doppler Wind Lidar 1000 mJ at 50 Hz Final build in progress

Air Force Remote Imaging Lidar 800 mJ at 100 Hz Final build in progress

Univ. of NH Doppler Wind Lidar 150 mJ at 50 Hz Delivery complete delivered

NASA Langley Ozone DIAL 900 mJ/pulse at 50 Hz Final build in progress

NASA Langley Phase II SBIR Seed & Metrology Laser 50 mW single frequency Funded (4/05 start)

NASA Langley High Spectral Res. Lidar 200 mJ at 200 Hz Funded (12/05 start)

NASA Langley Mars exploration 40 mJ at 20 Hz Final contract in negotiation

Navy Rangefinder/Designator 400 mJ at 25 Hz Final contract in negotiation

Single frequency pump head & resonator technology will support a significant number of next generation lidar applications

We Have Significant Ongoing Support for Space-Qualifiable and Single Frequency Laser Development

FIBERTEK, INC. Raytheon Related Laser/LIDAR

Experience Examples

• ABL-TILL: Track ILluminator Laser for the Air Force AirBorne Laser Program

• Advanced Airborne Targeting Laser (500 mJ Nd:YAG) for ATFLIR for F/A-18 (volume production)

• Synthetic Aperture LADAR for Tactical Imaging (SALTI)

Laser Transmitter Laser Transmitter Receiver (LTR)Receiver (LTR)

Laser Laser Electronics Electronics Unit (LEU)Unit (LEU)

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. 2005 Accomplishments

Delivery of the BalloonWinds laser transmitter for integration at Michigan Aerospace

Assembly of the injection seeded ring oscillator for the Raytheon system Diode pumped head has been assembled, tested, and fully vacuum baked for contamination control Optical bench has been populated and vacuum baked Final assembly and test is in progress

Validation of the final amplifier design for the Raytheon system The NASA Ozone single-sided pumped amplifiers have been shown to be capable of 100 Hz operation with good beam quality A pair of NASA Ozone single-sided pumped amplifiers will provide the first stage of amplification Incorporation of 100 W diode bar arrays will increase pulse energy from 300 mJ to over 450 mJ for the pair of NASA Ozone style amplifiers in the Raytheon laser A single power amplifier operated at only ¾ power (in both current and pump pulsewidth) has demonstrated over 700 mJ/pulse output for 280 mJ input with good beam quality. This design will be the basis for the final Raytheon laser amplifier

The final optical bench and canister design for the Raytheon system is complete Purchase orders have been placed, delivery is due in February

Board level assembly of the electronics is complete and testing is well underway Control electronics boards have been fully tested Diode driver testing is underway Electronics housing and thermal interface plate are on order

All key features of the optical design have been validated and assembly of the laser

module subassemblies have begun

FIBERTEK, INC. BalloonWinds Laser TransmitterIntegrated and Tested

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

FIBERTEK, INC.

Control and Power Electronics

Successful acceptance testing of the BalloonWinds laser transmitted has validated the Raytheon Wind Lidar laser transmitter electrical design

Interior view of the Laser Electronics Unit

DC-DC converters

Diode drivers

Analog and digital control boards

FIBERTEK, INC.

Control and Power Electronics

The control board stack for the Raytheon Wind Lidar lasertransmitter has been assembled and tested

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. 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. Amplifier DesignFirst Stage Design Validation

100 Hz Testing of NASA Ozone 1-Sided Pumped AmplifierNASA Ozone single sided pumped amplifiers were reevaluated as 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 also pump on bounce approach but with only 1 array at each bounce point - Beam profile and M2 were taken for with a single amplifier operated at 100 Hz and 200 µs pump pulseFor 30 mJ TEM00 we achieved over 100 mJ out of a single NASA Ozone Amplifier with an M2 of 1.2

Dual NASA Ozone style amplifiers operated with 75 W peak optical power per barmeet the requirements of the first amplifier stage for the Raytheon Wind Lidar transmitter

100 Hz M2 data for a single NASA Ozone amplifierNear field beam profile

FIBERTEK, INC. Amplifier DesignFirst Stage Output Power Modeling

Modeled vs. Measured Results Validate Modeling Approach

Based on a simple Franz-Nodvicamplifier approach

Oscillator Configuration 100 µs pump pulse 55 W/bar 100 bars

Oscillator Output 50 mJ/pulse 0.41 cm x 0.41 cm square beam M2 = 1.2

Amplifier Configuration Vary pump pulse width 55 W/bar 112 bars/amp

Low Energy Telescopic Resonator

Dual NASA Ozone amplfier output vs. 808 nm pump pulse width

808 nm pump pulse width (µs)

0 50 100 150 200 250

Dual amplifier outut energy (mJ)

0

50

100

150

200

250

300

350

400

DataModel

Application of model to the Raytheon Wind Lidar transmitter design (40 mJ TEM00 input,75 W/bar, 200 µs pump pulses) predicts over 500 mJ/pulse output

FIBERTEK, INC. Amplifier DesignPrototype Second Stage Testing

Power Amplifier Extraction Results

Final amplifier electrical to optical efficiency for 700 mJ output was over 11%.Full system electrical to optical efficiency was over 7%.

Measured Input vs.Output for Power Amplifier

1064 nm input pulse energy (mJ)

0 50 100 150 200 250 300

1064 nm ouput pulse energy

100

200

300

400

500

600

700

800

Pump conditions 75 W peak 808 nm ouput/bar 150 µs pump pulse width

In-house NASA Ozone laser output used as input to power amplifier

TEM00 ring configurationwith 30 mJ output

Dual 1-sided pumped amplifiers with only 55 W

peak 808 nm output/bar

Measured output of power amplifier vs. input from NASA Ozone system 75 W peak 808 nm

pump/bar 150 µs pump pulse

FIBERTEK, INC. Power Amplifier

Recent Test Results

Pulse energy of > 700 mJ at 50 Hz in a conductively cooled design

Preliminary M2 measurements found a value of ~2 for final amplifier output

Near field spatial is a rectangular super gaussian

Beam asymmetry in final system will be reduced by fine tuning the cylindrical compensating lens values

Near field beam profile

Recent prototype testing has validated the power amplifier design

FIBERTEK, INC. Raytheon Laser Transmitter Predicted Performance

Performance for 100% duty cycle, 50 Hz operation

Power consumption at 1 J of 1064 nm output

8% electrical to optical conversion

70% primary power conversion 940 W

50 W overhead (measured in BalloonWinds)

Laser mass - 43 kg

Laser volume - 10 cm x 42 cm x 69 cm = 29,000 cm3

355 nm output - 450-500 mJ @ 50 Hz

FIBERTEK, INC. Direct Detection Winds LIDARLaser Transmitter Status in 2006

Demonstration of 1 J/pulse from a single frequency 1064 nm pump laser operating at 50 Hz

Demonstration of greater than 45% conversion to 355 nm to achieve 450 mJ/pulse at 50 Hz

Completion of a risk reduction engineering model in a space qualifiable, conductively cooled

package with the performance given above

Improved first stage amplifier efficiency to bring the system electrical to optical efficiency to >8%

Amplifier tests to demonstrate scaling to 100 Hz

Performance characterization and testing at Raytheon Space and Airborne Systems in Q2 of 2006

10%, 20%, etc. duty cycle ON and OFF operation demonstration at Raytheon planned for Q2 of 2006

Field demonstration of the risk-reduction laser transmitter at GroundWinds site in Q3 of 2006

Continued Life Testing and characterization in Q4 2006 and beyond at Raytheon.

Demonstrate TRL 5 in 2006

FIBERTEK, INC.

Acknowledgement

BalloonWinds laser transmitter is funded by NOAA BalloonWinds Program

through UNH and MAC

Space Doppler winds LIDAR risk-reduction laser transmitter is funded by

Raytheon Internal Research and Development (IRAD)