Amplification of high repetition-rate, picosecond laser pulses using a zig-zag slab configuration

Laser sources which generate high peak-pulse energy, picosecond pulse duration outputs at high repetition rates are of particular interest for applications including laser ignition and space fragment detection. In this work, we demonstrate the design and operation of a zig-zag slab, solid-state master oscillator power amplifier (MOPA) which yields high energy amplification. The system uses a weakly-doped Nd:YAG slab as the amplifier medium, to amplify laser pulses from a passively Q-switched microchip seed laser. The seed laser beam undergoes four passes of the slab amplifier resulting in an amplified output pulse with hundreds of picoseconds pulse duration. We investigate the relationship between the angle of incidence of the seed laser beam into the amplifier slab and its effect on the slab fill-factor and overall laser field amplification. We also investigate the impact that the temperature of the laser diode array (LDA) which is used to pump the slab amplifier, has on the amplification efficiency of the MOPA. Experimentally, we demonstrate an amplification factor of ∼90 times from the optimized slab amplifier, and a resultant output laser field with a pulse energy of 99.58 mJ, a pulse duration of 491 ps, and a repetition rate of 200 Hz. We believe that this work will pave the way towards the development of novel all-solid-state amplifier designs for the generation of high-energy, high repetition frequency, sub-nanosecond laser outputs.