Efficient Tm-Fiber-Pumped Ho:YLF Laser System for Coherent LIDAR Applications

We propose to employ a recently developed, efficient, high-power, heavily-doped Tm:silica-fiber technology as a high-gain fiber pre-amplifier and as a fiber-laser-pump for the laser crystal Ho:YLF to provide a 2050-nm source for remote-sensing applications, including coherent DIAL systems. The resultant source has the potential for much higher electrical efficiency than current technology. One of our innovations is the use of a directly diode-pumped, heavily-doped Tm:silica fiber laser as the pump, to provide efficient conversion of electrical power to optical pump power. The second innovation is the use of heavily-doped Tm:silica fiber as a high-gain pre-amplifier for a low-power 2050-nm master oscillator. The third innovation is made possible by the high gain available from our fiber-laser-pumped Ho:YLF amplifiers. In contrast to seeded oscillators, our laser system has enough gain to amplify a cw, externally-modulated, single-frequency laser, allowing control of the pulsewidth and wavelength while preserving the frequency stability of the source. The use of a Tm-fiber preamplifier simplifies the system architecture and increases the system efficiency. In the Phase I effort, we plan on demonstrating the amplification of a cw, single-frequency laser, as well as developing designs for complete compact, efficient mJ-level lidar sources.