Efficient ASE control in cryogenic gas cooled Yb:YAG multislab amplifiers with Cr⁴⁺:YAG interlayers

Abstract

A novel approach based on Cr4+:YAG interlayers to break the transmission paths of amplified spontaneous emission (ASE) in a cryogenic gas cooled Yb:YAG multislab amplifier geometry was presented for the suppression of ASE in the power scaling of high energy, high average power laser systems. The benefits of Cr4+:YAG interlayers for the overall performance of an amplifier were illustrated with respect to energy storage capacity, heat generation and amplification of the seed pulses based on the theory of quasi-three-level Yb3+ ions and Cr4+:YAG saturable absorption, the Monte Carlo and ray-tracing methods. For the amplifier with optimized Cr4+:YAG interlayers, it was found that the energy storage efficiency was increased from 39.12% to 47.38% in comparison with the amplifier without interlayers. The maximum output energy of 1119.53 J with an optical-to-optical efficiency of 28.91% in the amplifier with interlayers was obtained, while it reduced to 810.61 J with an optical-to-optical efficiency of 20.94% in the amplifier without interlayers. To our knowledge, this is the first quantitative characterization of the performance of a cryogenic gas cooled Yb:YAG multislab amplifier with Cr4+:YAG interlayers.

A 61-mJ, 1-kHz cryogenic Yb:YAG laser amplifier*

“…To overcome this problem, Cr:YAG is usually adopted to absorb the spontaneous light, whether diffusion bonded to the four lateral faces of Yb:YAG crystal [12] or used as interlayers in an Yb:YAG multislab amplifier. [15] This adds difficulty to crystal production. In contrast, rod-type Yb:YAG is more suitable for amplifiers with output power below 200 W. [16] With a low doping rate and long length, the accumulated heat can be transferred to the heat sink efficiently through the lateral surfaces of the Yb:YAG crystal.…”

Amplified spontaneous emission suppression of a saturable absorber in a nanosecond double-pass laser amplifier

“…11) SA cladding is also widely used to prevent transverse lasing in disk or slab amplifiers. [12][13][14][15] In this letter, we consider that an SA-inserted between the gain medium and the return mirror of a nanosecond doublepass amplifier can effectively absorb the ASE until the seed pulse arrive. To evaluate the effectiveness of this method, we develop a theoretical model for the SA-inserted double-pass amplifier by combining existing the SA model 16) with the modified Frantz-Nodvik equation.…”