Preliminary design of a Tm:Lu2O3-based amplifier for J-scale ultra-short pulses at a kW average power

We report on the conceptual design of a 2 μm, ultrashort pulse laser system including power amplification based [1] on Tm-doped gain medium. We consider ceramic [2] Tm:Lu₂O₃ with a direct diode-pumping architectures to develop a solid-state laser technology for high-efficiency, high repetition rate and ultra-short pulse laser, with high peak power and kWscale average power.. A CW pumping (duty cycle of the diodes 100%) and a multi-pulse extraction mode [3] scheme are considered with a multipass scheme with thin disk Tm:Lu₂O₃ doped at 4% and with lateral (edge) [5] pumping (EPDL). Here we show the preliminary results of the modelling of a two-stage amplifier operating at a repetition rate of 1 kHz, output energy of <500mJ, with a maximum fluence of about 1.5 J/cm2 for the first stage and of about 2 J/cm2 for the second stage. The optical model of the two-stages is based on a multi-pass configuration and designed for a gain of 50x and 12x respectively. Each stage consists of two gain media in active mirror configuration. This conceptual design represents the best balance between constructive complexity and efficiency in terms of energy gain.