Nanosecond periodically poled lithium niobate optical parametric generator pumped at 532 nm by a single-frequency passively Q-switched Nd:YAG laser

We report an efficient, visible, nanosecond optical parametric generator of periodically poled lithium niobate pumped at 532 nm by a frequency-doubled, diode-pumped, passively $Q$-switched, single-mode Nd:YAG laser with $90‐\mathit{\mu }\mathrm{J}$ pulse energy. The signal radiation is tunable from 637 to 593 nm. The maximum signal-conversion efficiency is 23%. Optical parametric amplification of a He–Ne laser at 632.8 nm is also studied.