High Average Power Diode Pumped Solid State Lasers: Power Scaling With High Spectral and Spatial Coherence

摘要

The main program objective was the development of a kilowatt class, cw Nd:YAG diode-laser-pumped solid-state laser (DPSSL) with quantum noise limited amplitude and phase, 24by7 operation capability and the ability to be repaired while in operation. The approach was a master-oscillator power- amplifier (MOPA) laser utilizing a series of zig-zag slab power amplifiers stages. We developed fiber amplifiers at the 200W level to generate power with high optical efficiency that can effectively extract energy from the power amplifier slabs. We also worked on the generation of high average power visible light by developing nonlinear optical materials with large apertures, low photo- refraction and minimal visible induced infrared absorption. The second objective was to develop a 1 joule, pulse-modulated, diffraction limited MOPA laser with less than 1 MHz line-width. A follow-on objective was frequency conversion to 1.5 or 2.0 microns for remote sensing applications. We demonstrated Yb:YAG slab lasers pumped with high brightness laser diodes. Supporting this project was the development of laser diodes operating in the 1.5 micron region for pumping of erbium doped laser hosts, and the synthesis of new low-loss polycrystalline laser host materials for in-band pumping into the upper laser level to improve the laser efficiency at eye-safe wavelengths. We developed orientation patterned Ga-As to frequency convert high peak power 1- micron radiation to eye-safe wavelengths in the mid-infrared for defense applications. The third objective, power scaling and determining the potential for phase-locking of ultra-fast laser systems for a wide range of sensing and machining applications, was demonstrated as well.