ER-YAG-LASER AT 2.94-MU-M Q-SWITCHED BY A FTIR-SHUTTER WITH SILICON OUTPUT COUPLER AND POLARIZER

A FTIR-shutter based on the principle of frustrated total internal ref lection was studied as an active Q-switch for 3 mu m lasers. The FTIR- shutter used consists of two truncated YAG crystal prisms with a small air gap between them. The gap width is modulated by two piezoelectric al cells attached on the truncated facets of the prisms. The switching time and the spatial transmission profile of the shutter were measure d, An Er:YAG-laser was Q-switched with this shutter. Furthermore, we d emonstrate that conventional semiconductors like silicon and germanium wafers are effective output couplers and Brewster polarizers for 3 mu m lasers. Linearly polarized and stable laser pulses with pulse energ y up to 50 mJ and pulse duration of less than 60 ns are achieved.