946nm Nd:YAG laser frequency doubled with periodically-poled LiNbO₃

Frequency doubling of a 946nm Nd:YAG laser is a route to the generation of high average power in the blue spectral region. Periodically-poled lithium niobate (PPLN), with its combination of high nonlinearity and non-critical phase-matching offers the prospect of high conversion in a simple extra-cavity single-pass arrangement. The PPLN (length 15mm, grating period 4.5µm ) was heated at a temperature of 140°C. With 1.5W incident power at 946nm in a linearly polarized fundamental mode (M2 < 1.1) and in pulsed operation at the relaxation oscillation frequency (160kHz, 300ns pulses), a power of 450mW with M2 = 1.25 was generated at 473nm. The conversion efficiency versus internal fundamental power was 40%. No photorefractive damage was observed