All solid-state diode pumped Nd:Yag MOPA with stimulated Brillouin phase conjugate mirror

At the Nederlands Centrum voor Laser Research (NCLR) a 1kHz diode-pumped Nd:YAG Master Oscillator Power Amplifier (MOPA) chain with a Stimulated Brillouin Scattering (SILS) Phase Conjugate mirror has been designed and operated. A small Nd:YAG zig zag slab (1.8 by 1.7 by 40mm) is side pumped with 200μs diode pulses in a stable unidirectional ring oscillator. The oscillator is Q switched and injection seeded with a coin menial diode pumped single frequency CW Nd:YAG laser. The output consists of 25μs FWHM-pulses at 1064mm in a single-transverse, single-longitudinal mode. The oscillator slab is imaged on a square aperture that transmits about 80% of the energy. The aperture is subsequently imaged four times in the amplifier. The amplifier is a 3 by 6 by 60mm Brewster angle zig-zag slab, pumped by an 80-bar diode stack with pulses up to 250μs. After the second pass the light is focused in two consecutive cells containing freon-113 for wave-front reversal in an oscillator/amplifier-setup with a reflectivity of 60%. The light then passes through the amplifier twice more to produce 40W output with near diffraction limited beam quality. The zig-zag slab in the oscillator effectively reduces thermal lensing effects and the Brillouin scattering reverses any alterations originating from the amplifier.