HIGH-POWER INJECTION SEEDED OPTICAL PARAMETRIC OSCILLATOR

We have demonstrated the feasibility of an infrared optical parametric oscillator (OPO) without frequency control elements that produces near transform limited 120 MHz bandwidth, 10 ns pulses via injection seeding. The experimental threshold for injection seeding at 1.5-mu-m is only a few mu-W, and the OPO cavity is easily locked to the seed laser. Using a poor spatial quality 540 Hz YAG laser as a pump source, we have obtained 1.5-mu-m pulse energies of 3 mJ/pulse (> 10% energy conversion). However, at present, the OPO gain falls below threshold after continuous operation for approximately 1 hour, due to reversible degradation of the LiNbO3 crystal. A small frequency shift between seed and output frequencies is observed and possible mechanisms are discussed.