Abstract

Q-switched lasers operating in the nominally eye-safe 2 μm wavelength region are important for applications such as material processing, medicine, LIDAR systems, and pumping of optical parametric oscillators based on ZnGeP₂ or periodically poled GaAs. Many of these benefit from wavelengths above 2.05 µm, which are not accessible by the actually widely used Tm-lasers. The long upper laser level lifetime and large energy storage capacity makes Ho-doped crystals very attractive for these applications. In band pumping of singly doped Ho-crystals around 1950 nm enables high laser efficiencies and reduced heat generation inside the laser crystal due to the low quantum defect. Optically pumped semiconductor disk lasers (OPSDL) based on GaSb could be an attractive and compact pump source. These OPSDL can be pumped with cheap laser diodes around 976 nm or 1470 nm and built up in simple and robust setups. In the wavelength range around 2 µm cw output powers up to 17 W have been demonstrated at room temperature [1].

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