Efficient and low-threshold Alexandrite laser pumped by a single-mode diode

We report a low-threshold and efficient Alexandrite laser that is pumped by only one state-of-the-art single-spatial-mode diode. The pump diode provided 170 mW of output power at 635 nm. In continuous wave (cw) laser experiments, we demonstrated lasing thresholds as low as 13 mW, slope efficiencies as high as 36%, output powers up to 48 mW, and a tuning range extending from 736 nm to 823 nm. Laser slope efficiency, laser output power, fluorescence lifetime, and emission intensity were further shown to decrease monotonically with increasing temperature. Pure cw operation could be obtained under most circumstances. However, self-Q-switching (SQS) was also observed in slightly misaligned laser cavities. During SQS, stable pulses with pulsewidths in the 5-15 mu s range and pulse repetition rates in the 10-35 kHz range have been obtained. We believe that this compact and efficient Alexandrite laser system may be an attractive source for several applications.