Abstract

With the rapid development of high transparent ceramics, it is possible to achieve high laser output powers. Currently, high average power lasers with high efficiencies and good beam qualities are desired for many applications. To develop such an ideal optical source, it is necessary to avoid thermal effects. Giesen et al. [1] proposed a thin disk laser concept. This concept used a face cooled thin, disk-shaped active medium. This face cooling minimized the temperature gradient and the phase distortions transversal to the direction of the beam propagation, and allowed realization of a laser with high output power (> 5.3 kW), high efficiency (> 65%), and good beam quality (M² < 24), simultaneously from a single Yb:YAG disk. The laser was pumped up to about 4 kW/cm². Alternatively, Tsunekane et al. [2] reported a diode edge pumped microchip laser, and 414 W CW output powers were obtained at incident pump powers of 946 W from a 200-μm thick microchip laser. In their work, the pump density was about 8.8 kW/cm² and the slope and optical-to-optical efficiency were 52% and 44%, respectively. However, the temperature rise at the high-reflection coating was considerable due to its low thermal conductivity. In fact, the temperature of the opposite surface which was non-cooled was measured to be 228 °C at the input of 946 W. Without the high-reflection coating and the heat sink, the temperature rise can be suppressed, leading to higher operation.

© 2009 IEEE