Cryogenic Kilowatt Diode Pumps for Cryogenic Yb:YAG Disk Lasers

摘要

Cryogenically cooled, kW-level ytterbium:yttrbium aluminum garnet (Yb:YAG) disk lasers offer intrinsic advantages over their room-temperature counterparts due to their high efficiency, increased thermal conduction, decreased coefficient of thermal expansion, and decreased temperature dependence of refractive index. With a 940-nm optical pump band, these disk lasers can be optically pumped with cryogenically cooled diode laser arrays, thereby eliminating the need for power-hungry water-cooled heat exchangers. This paper describes the development and evaluation of liquid-nitrogen cooled, kW-level diode laser arrays emitting in the 940-nm Yb:YAG pump band. Diode laser material design parameters are optimized for liquid nitrogen temperature operation, and diode laser array performance characteristics are presented. Factors limiting the diode laser array output power and reliability are analyzed and discussed. Diode array ruggedization and heat exchanger design modifications expected to result in higher output power levels are presented.