Efficient operation of a pulsed diode pumped cryogenic gas cooled Yb:YAG multislab amplifier delivering 7.4 J at 10 Hz

摘要

The next generation of ultra-intense laser facilities, currently being developed in European projects such as HiPER [1] and ELI [2], require the development of a laser amplifier technology capable of producing kJ-level pulses with nanosecond duration. These will need to operate at multi-Hz repetition rate and high wall-plug efficiency, which is only possible using diode-pumped solid-state laser (DPSSL) technology. The DiPOLE project at the Central Laser Facility (CLF) is developing a scalable and efficient high pulse energy DPSSL architecture based on a cryogenic gas cooled, multi-slab ceramic Yb:YAG amplifier concept, capable of generating kJ pulse energies. To test the viability of this concept, a scaled-down prototype amplifier has been built, designed to deliver 10 J pulses at 10 Hz repetition rate with an optical-to-optical (ηo-o) efficiency of 25% [4]. Recently, a new multi-pass relay-imaging extraction architecture, including spatial filtering, has been installed that allows up to eight passes through the amplifier head. This has enabled more efficient extraction at higher coolant temperatures, where gain is lower and the impact of ASE is reduced [4], as well as improving the spatial quality of the output beam.