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Injection-seeded diode-pumped regenerative ring Nd:YAG amplifier for spaceborne laser ranging

We report on a small, all solid state, regenerative ring amplifier designed as a prototype for space application. Features include dual side pumping of a 2 mm*2 mm*10 mm Nd:YAG slab and a triangular ring cavity design, which minimizes the number of optical components. The pump head was fitted with twin single-bar diode arrays consisting of 960 individual stripes, temperature tuned to the Nd:YAG pump bands at 809 nm and capable of operation up to 100 Hz. The single-pass gain of this head was measured at 13% for a pump pulse energy of 18.4 mJ from the diode arrays and the cavity round trip transit time was 3.1 ns. The ring has amplified 170 ps pulses with 10-13-10-14 J of energy by a factor of more than about 106 while preserving both the temporal and spatial shape of the pulses. The seeding threshold was about 10-15 J and a maximum saturated output energy of about 40 mu J was obtained when seeded with pulses greater than 1 pJ. Comparison with modelled performance is also given.