High-peak power nanosecond optical parametric amplifier with periodically poled KTP

A two-stage optical parametric amplifier generating 5 ns 208 kW peak power pulses in the spectral region at 1.535 microm in a diffraction-limited beam was realized in a single periodically poled KTP crystal. The maximum small-signal gain for the two stages reached 75dB and the total conversion efficiency was 30%. An analysis of the small-signal gain dependence on the M2 of the pump beam is presented for the collinear and noncollinear OPA. Efficient spectral broadening of the signal was demonstrated in short pieces of single-mode telecommunication fiber.