Compact blue laser devices based on nonlinear frequency upconversion

Miniature sources of coherent blue radiation can be produced by using nonlinear optical materials for frequency upconversion of the infrared radiation emitted by laser diodes. Direct upconversion of laser diode radiation is possible, but there arc several advantages to using the diode laser to pump a solidstate laser which is then upconverted. In either case, the challenge is to find combinations of nonlinear materials and lasers for efficient frequency upconversion. Several examples have been demonstrated. These include intracavity frequency doubling of a diode-pumped 946-nm Nd laser, intracavity frequency mixing of a 809-nm GaAlAs laser diode with a diode-pumped 1064-nm Nd: YAG laser, and direct frequency doubling of a 994-nm strained-layer InGaAs laser diode.