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For solar cells based on CuGaSe2(CGS) absorber layers physical vapour deposition (PVD) was employed to deposit polycrystalline CGS thin films. Efficiencies up to 7.9% were achieved by applying a two-stage deposition process for absorber preparation. The high structural quality of the absorbers is shown. For highest cell efficiencies our standard recipe for the CdS buffer deposition had to be re-adapted. Voltage dependent spectral response measurements of the device in conjunction with absorption measurements of the absorber layers allow calculation of the minority carrier diffusion length, space charge region (SCR) width, absorber carrier concentration and the built-in voltage. The defect state density at the buffer/absorber interface is estimated. It can be shown that the benefical effect of the modified buffer deposition is mainly due to a reduced acceptor concentration at the absorber/buffer interface.

We demonstrate cw and Q-switched operation of Er:YAG laser systems emitting eye-safe radiation at 1645 nm. High brightness, narrow bandwidth diode laser modules at 1532 nm are used for resonant pumping, providing an absorption efficiency of 96%. Comparison with broadband diode pumping at 1455 nm shows an increase of the pumping efficiency by a factor of 2.5, leading to an optical efficiency of more than 25% in cw and 10 % in Q-switched mode under cw pumping. In addition, dual-wavelength resonant pumping of the Er:YAG laser is investigated.

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