Research on laser diode end-pumped Er:YSGG/YSGG composited crystal at 2.79 μm

Abstract

Lasers at 2.79 μm emitted by Er:YSGG crystal have attracted considerable interest in biological and medical applications. However, due to the thermal effect of laser crystal, the output power has been limited. In this paper, the advantages of Er:YSGG/YSGG composite crystal in reducing thermal effects and achieving high output power are investigated theoretically and experimentally. The numerical results show that the temperature rising and total thermal deformation of Er:YSGG/YSGG composite crystal are evidently reduced because the undoped YSGG absorbs the heat generated from the Er:YSGG. The maximum temperature rising reduces with increasing of the length of undoped YSGG crystal, and its location moves from the pump face to the inside of the Er:YSGG. The optical path difference of the Er:YSGG/YSGG composite crystal is obviously reduced comparing with that of Er:YSGG crystal, which indicates the thermal focal length of the Er:YSGG/YSGG composite crystal is increased, and the thermal effects are reduced. In experiments, the maximum continuous wave output power of 900 mW with slope efficiency of 12.1% at wavelength of 2.79 μm is obtained in laser diode end pumped Er:YSGG/YSGG crystal. To our knowledge, the output power of Er:YSGG/YSGG crystal is the highest value for the laser diode end pumped Er:YSGG crystal. The thermal focal length of the Er:YSGG/YSGG measured in experiment is increased comparing with that of Er:YSGG. Investigations have demonstrated that the Er:YSGG/YSGG composite crystal has a great advantage in reducing the influence of thermal effects and achieving high output power.