Compact Power Amplifier for Hybrid Fiber/Bulk Wind Lidar Transmitters

Measuring global winds from space using eye-safe coherent laser radar is an important on-going NASA technology and instrument development effort that will ultimately improve the fidelity of meteorological climate models, near-term weather forecasting, and commercial aviation management and optimization. Activities like NASA LaRCs Wind-SP coherent lidar program are pushing these laser and lidar technologies forward with regard to high-energy eye-safe transmitter lasers, low-noise fast-tunable master and local oscillator lasers, improved lidar photoreceivers, and active optical alignment and lag-angle compensation functionalities specific to space-based applications. Specifically in this proposal, Beyond Photonics plans to develop a compact next-generation Power Amplifier/Transceiver Module for current and future NASA missions focused on lidar systems in the short-wave infrared wavelength region near two microns. We will emphasize the design and development of very compact and alignment-insensitive Ho:YLF/LuLF amplifiers operating near 2.05 m, monolithically integrated with very compact lidar transmit/receive optics and photonics, and capitalize optimally on very efficient hybrid fiber/bulk-crystal MOPA designs. Efficient, compact approaches using optimally-configured Tm:fiber-based front end transmitters and preamplifiers followed by dual-pass Tm bulk crystal amplification will be a focus to reach flexible performance on the order of 40 mJ/pulse, 400 Hz PRF, and high beam quality, which can serve as an effective transmitter for many upcoming NASA remote-sensing applications. Operationally flexible, low-SWaP path-to-space approaches will be emphasized. These innovations will apply directly to current NASA missions and instruments (Doppler wind lidar, IPDA, LAS) and accelerate commercial development and availability of practical ground-based and airborne systems (e.g. compact airborne CO2 concentration-measuring instruments) at BP and elsewhere. Beyond Photonics recognizes the need for significant improvements to the size, weight, and prime power requirements of pulsed transmitter lasers and bulk amplifiers for eye-safe lidar applications.  Specifically, improved 2-micron wavelength transmitters for next-generation lidar systems aimed at space-based measurements of 3D winds like WIND-SP, airborne applications, and atmospheric CO2 and H20 concentrations using IPDA lidar and similar remote spectroscopy techniques are needed for NASA and emerging commercial applications.  Compact, efficient 2 µm wavelength master-oscillator/power-amplifier (MOPA) sources like those proposed will also find military and commercial application. Our team’s extensive past experience with such components and systems lends a unique and extraordinary perspective that we believe will yield significant gains in system compactness, efficiency, and reliability for a wide array of operational applications relevant to NASA’s missions, and improve the potential for near-term application to other commercial and military laser remote sensing requirements. Demonstrate full performance (40 mJ, 400 Hz, 200-500 ns, with M2 <1) 2.05 micron wavelength Ho:LuLF amplifier using laboratory breadboard.   The objective is to demonstrate that a seed input of 0.5 mJ at 400 Hz PRF and with 200-500 ns pulse durations can be amplified to 40  mJ at 400 Hz while maintaining high beam quality (M2<1), Design compact brassboard amplifier module based on the optimized breadboard configuration.  Incorporate advanced fabrication techniques allowing the use of small and rugged optical components and optical mounting techniques. Build compact brassboard amplifier module and perform detailed lab testing to show objective performance is achieved Perform limited environmental testing of the brassboard module to demonstrate that it maintains performance over moderate temperature variations, and vibration and shock levels. Deliver brassboard amplifier module to NASA LaRC and support integration and testing activities at NASA LaRC.

Potential NASA applications of the proposed hybrid fiber/bulk power amplifier/lidar transceiver technology include on-going and future measurement of global winds from space; ground-based and airborne coherent lidar programs; eye-safe remote laser spectroscopy applications for measurement of atmospheric constituents like CO2, water vapor, and methane; tracking of fast-moving space debris and asteroid hazards; spacecraft docking applications; and other shortwave-IR wavelength instrument developments in the 1.5-to-2.0 micron wavelength region. Non-NASA commercial uses of fiber/bulk MOPA transmitters include DoD hard target and space debris tracking/imaging problems & research/industrial applications requiring very compact efficient front-end transmitter lasers and bulk amplifiers at eye-safe SWIR wavelengths. Commercial development is planned for compact, high-FOM remote-sensing products for winds and other remote sensing applications.

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