Abstract

The performance of a diode laser can be improved by using an external cavity, which include tuning the laser wavelength, narrow spectral linewidth, and increasing the output power. These advantages are useful to generate SHG of a diode laser. By putting a KNbO₃ crystal into an external cavity GaAlAs diode laser, we obtained 135 µW of blue radiation with a linewidth of 1.2 MHz and a tunable wavelength range 426.2–428.6 nm. An unpacked GaAlAs diode laser with AR coating at laser wavelength on the output cleavage plane was placed on a thermoelectric cooler so that the temperature could be stabilized. Diode laser radiation of 20 mW was focused into a KNbO₃ crystal (3×3×8 mm³ with dielectric coating on the ends) by a GRIN rod lens. The light transmitted through the crystal was collimated to a grating with a focal lens. The grating was used to feed back infrared radiation and separate the blue output by its dispersion. A piezoelectric translator (PZT) attached to the grating provided fine tuning of the laser wavelength. The KNbO₃ crystal was mounted in a thermoelectrically temperature-controlled enclosure. To achieve phase matched SHG in the tunable wavelength range, the temperature of the crystal was changed to track the voltage applied to the PZT by an automatically controlled setup.

© 1991 Optical Society of America