Engine ignition using a laser requires very high peak power levels, that can be produced by solid-state lasers such as Yb:YAG passively Q-switched lasers. We developed high repetition rate diode pumped Yb:YAG micro-lasers to study the effect of cumulated pulses on the engine ignition process. The Yb:YAG laser oscillator is pumped by a 5-Hz quasi-continuous wave diode laser emitting 3-ms long pump pulses with up to 20 W peak power. It’s passively Q-switched using a Cr:YAG crystal. Various Yb:YAG dopant concentrations and crystal length have been tested and different initial transmittance values for the Cr:YAG crystal have been compared. As a result of quasi-continuous wave pumping and passive Q-switching, bursts of short pulses are emitted at the 5-Hz repetition frequency of the long pump pulses. The control of the intra-burst repetition rate is achieved through tuning the pump power between a few watts and 20 W. The energy per pulse ranges from 250 μJ to 300 μJ, with a lower than 5 ns pulse duration. The intra-burst repetition rate can go up to 20 kHz. An amplifying stage comprised of one single Yb:YAG crystal is added after this laser oscillator.
P. Bourdon, C. Planchat, D. Fleury, J. Le Gouet, F. Gustave, A. Dolfi-Bouteyre, L. Lombard, H. Jacqmin, and A. Durécu, "Passively Q-switched Yb:YAG micro-laser for high peak power high repetition rate burst of pulses emission," Proc. SPIE 10797, Technologies for Optical Countermeasures XV, 1079707 (Presented at SPIE Security + Defence: September 10, 2018; Published: 9 October 2018); https://doi.org/10.1117/12.2325719.
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