Intracavity frequency doubling of a diode pumped nd:yag laser using a knbo₃ crystal

Abstract

In this paper we present first results on intracavity frequency doubling of a diode-pumped Nd:YAG laser at Λ = 1.064 μm with single domain KNbO₃ crystals. Potassium niobate, with its large nonlinear optical coefficients, is well suited for efficient frequency doubling of light from various near infrared lasers. Non critical 90° type I phase matching can be achieved using the nonlinear optical coefficient d ₃₁ = –15.8 pm/V at a temperature of 188°C. The width at half maximum of the temperature tuning curve was measured to be 0.5°C. The 6.2 mm long KNbO₃ crystal was mounted in a small, temperature stabilized oven at the center of a 10 cm long confocal resonator. An end pumped configuration was used with one mirror as an output coupler for the frequency doubled radiation. The pump radiation (Λ = 808 nm) was focused through the other mirror into a 5 mm long Nd:YAG rod. An output power of 2 mW in the green was measured with a laser diode optical power of 200 mW.