High-average-power diode-pumped lasers near 2 um

The development of a high brightness diode laser pump source and a scalable end-pumped resonator design are key issues in achieving high average power diode-pumped solid-state lasers without sacrificing efficiency and beam quality. The above is particularly true for the low gain, quasi-three level 2 micrometers solid-state laser systems. Spatial multiplexing of multiple diode lasers into a single optical fiber creates a high power, versatile pump source which is compatible with end-pumping. A diode laser pump module was built that produced 15 W of 785 nm light out of a 400 micrometers core diameter multimode fiber within numerical aperture of 0.25. A periodically imaged resonator (PIR) incorporates multiple end-pumping ports for high efficiency average power scaling, yet can be made very resistant to the adverse thermal effects of end-pumping. Fifteen watts of continuous wave, fundamental mode, 2 micrometers radiation were obtained from a 4% Tm:YAG PIR end-pumped with 46.5 W of fiber- coupled 785 nm diode laser emission.