The direct side-pumping of Nd:YAG rods with laser diodes has been shown to be a cost effective scheme for scaling to simultaneous high average and high peak power operation. Careful control of the parameters that govern the performance of a multi-spatial mode MOPA system has led to the demonstration of reliable Q-switched average powers of up to 1600 W and peak powers in excess of 18 MW at the 1064 nm fundamental wavelength. The techniques used to refine the properties of an infrared stable resonator in order to optimise intra-cavity second harmonic generation are discussed. Average powers of up to 290 W and peak powers of up to 0.45 MW at 532 nm have been demonstrated from a single cavity. By polarisation multiplexing the outputs of two cavities emitting at 532 nm, we have achieved single-beam average and peak powers of up to 580 W and 0.9 MW respectively and gained flexible control of pulse duration and temporal shape.

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