Broadly tunable continuous-wave solid state red source based on intracavity-doubled Cr4+:forsterite laser

Abstract

This work describes the development and characterization of a continuous-wave (cw) room-temperature intracavity-doubled Cr<SUP>4+</SUP>:forsterite laser which produces broadly tunable red radiation. Such a source is potentially important in spectroscopy, display technologies, and medical applications. In the experiments, a 2-cm-long Cr<SUP>4+</SUP>:forsterite crystal was placed in an astigmatically compensated x-cavity which was end-pumped by a 1064-nm Nd:YAG laser. The crystal which had a small-signal pump absorption of 68 percent was maintained at 20 degrees C. An intracavity Brewster-cut SF10 prism was used to tune the output of the laser. Intracavity frequency doubling was achieved by using a periodically poled lithium niobate (PPLN) crystal which had 8 different poling periods. The PPLN crystal was placed inside the resonator between a curved folding mirror and the curved output coupler. The transmission of the output coupler was 2.6 percent at 1260 nm. The PPLN temperature was maintained at 188 degrees C. By translating the PPLN crystal through sections with different poling periods, second harmonic generation was obtained in the wavelength region between 613 and 655 nm. With an incident pump power of 6.8 W at 1064 nm, the Cr<SUP>4+</SUP>:forsterite laser produced 245 mW of cw output power at 1260 nm and intracavity frequency doubling yielded 45 mW at 630 nm.