Mid-infrared diode-pumped solid-state lasers
Esser, M.J. Daniel
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The concept of a diode-end-pumped Tm3+ laser pumping a Ho3+ laser was utilised to develop mid-infrared solid-state laser devices. After presenting an in-depth literature study of the promising material Tm:GdVO4, it was theoretically predicted and experimentally verified that a diode-end-pumped Tm:GdVO4 laser can be operated over a 100 nm wavelength range merely through the appropriate selection of the resonator output coupling value. The output at 1818 nm is the shortest wavelength demonstrated for a multi-watt Tm:GdVO4 laser, while the quasi-continuous-wave output power of 8.7 W at 1915 nm is the highest reported for a diode-end-pumped Tm:GdVO4 laser. A dual-end-pumped Tm:GdVO4 laser operating at 1892 nm was subsequently designed as pump source for a Ho:YLF laser, the implementation of which was demonstrated for the first time. The Q-switched Ho:YLF laser, pumped with a 83 mJ quasi-continuous-wave pulse of 19 ms duration at 5 Hz repetition rate, produced 1.9 mJ in a 17.6 ns pulse at 2051 nm on the π-polarisation, and 2.1 mJ in a 47.7 ns pulse on the σ-polarisation. This initial research work directed the way towards the development of high-energy Ho3+ lasers and amplifiers pumped with alternative high average power Tm3+ laser devices.