Abstract

The CW self-frequency-doubling in Nd:MgO:LiNbO₃ crystal has been demonstration by T. Y. Fan et al^[1]. They did not consider the influence of the self-thermal effect of the crystal irradiated by laser beam on itself temperature. We found that the external control temperature for the optimum phase-matching to generate the second-harmonic wave in Nd: MgO:LiNbO₃ CW self-frequency-doubled Laser must be decreased as the input pump powers were increased. Because the pump irradiance absorbed by the crystal inevitablely resulted in the temperature rise, the external control temperrature forced on the crystal must correspondingly be decreased to maitain the optimum phase-matching temperature needed by the self-frequency-doubled process. The dependence of the control temperatures for the phase-matching on the absorbed pump powers was experimentally measured. We obtained up to the CW second-harmonic output power of 3 mW which was three times more than the previous obtained power level^[1] with the Nd:MgO: LiNbO₃ laser cavity pumped by CW Rhodamine 6G dye laser tuned to the 598nm absorption line of the material. The conversion efficiency, defined as the ratio of total second-harmonic output to pump power absorbed above threshold, was about 15% per watt which was twice of previous result^[1].

© 1992 Optical Society of America