Abstract

We investigated the laser materials Er(50%):YAG at 2.94 μm and Er(15%):YLF at 2.81 μm. For the quasi-cw laser experiments we used a lens duct [1] for collecting the diode laser beams and imaging them longitudinally into the laser crystal (Fig. 1). The resonator consists of a thin incoupling mirror (AR 970 nm and HR 0.1% 2.8-3 μm) and a slightly curved output mirror. For the experiments with Er:YAG a rear mirror transmission of 0.2% and for Er:YLF of 2% was chosen. We coupled two water cooled SDL-6200 diode stacks into the lens duct, each consisting of five 1 μm × 10 mm arrays emitting around 970 nm and being supplied with micro- cylindrical lenses for the fast divergence direction. In the horizontal plane the light is focused to the exit face of the lens duct by the refraction of the entrance face. The slow axis divergence of about 10° in the vertical plane is guided to the exit face of the lens duct by total reflections at the side faces. The exit face has a side length of 1.5 mm. The transfer efficiency of the lens duct is about 90%.

© 1996 IEEE