Cryogenic Diode Laser Array Pump for High Power YAG Lasers

This Phase I SBIR proposal describes a program that will design a cryogenic, liquid nitrogen (LN) cooling system for efficient operation of multi-kW level diode laser arrays, and determine the diode laser array design parameters for optimal LN operation with emission in the 800 nm to 950 nm spectral region. Such high power diode laser arrays are needed for optically pumping LN-cooled solid-state Nd:YAG and Yb:YAG lasers with superior operating characteristics. Phase I will investigate various forced-flow LN cooling configurations designed to avoid gas-phase interface formation at multi-kW level heat loads, utilizing materials with matched thermal expansion coefficients to minimize thermal stress. The naturally high thermal conductivity of most materials at LN temperature will be exploited. Diode laser design parameters such as epitaxial layer configuration and laser bar mounting details will be investigated for the favored optical pump bands for these solid-state laser materials. Phase II will deal with fabrication of a prototype cooling system to interface with the high power diode laser arrays for efficient YAG laser pumping. Spire’s laser bar fabrication expertise and current involvement with high power 630 nm LN temperature optical pump arrays will be of great benefit to the proposed program.