Compact 500.9 nm laser based on doubly resonant intracavity sum–frequency mixing

A compact 500.9 nm laser was realized using doubly resonant intracavity sum–frequency mixing. An Nd:YAG crystal and an Nd:YVO₄ crystal were employed as the gain crystals. In two sub-cavities, 946 nm radiation from the Nd:YAG and 1064 nm radiation from the Nd:YVO₄ were mixed to generate 500.9 nm. In the overlapping of the two cavities, sum–frequency mixing was achieved in a type-II critical phase-matched KTP crystal. An output power of 78 mW at a wavelength of 500.9 nm was generated using a total incident pump power of 4 W and the output light exhibited low noise, with the root-mean-square value being 0.3%.