Efficient operation of a gain-switched Cr:forsterite laser at 1-2 kHz repetition rates with frequency doubling

Summary form only given. Gain-switched operation of Cr:forsterite (Cr/sup 4+/:Mg/sub 2/SiO/sub 4/) lasers is possible in a wide spectral range extending in the near infrared from 1.13 to 1.37 /spl mu/m. A significant portion of the yellow-red spectral range which is important for medical and photochemical applications can be thus covered through second-harmonic generation. Specifically, for photodynamic therapy high repetition rates and high average powers are advantageous. Although 1-16 kHz operation of gain-switched Cr:forsterite lasers has already been demonstrated, the output power did not exceed 0.3 W and the laser efficiency was limited to /spl ap/10%. Second harmonic generation with 7% conversion efficiency was achieved previously only at 20 Hz. Here we report on efficient kilohertz operation of a Cr:forsterite laser with maximum average power as high as 1 W at 2 kHz. Frequency doubling with >13% conversion efficiency provides 60 mW of average power near 619 nm at 1 kHz.