Research On Ho:YAG Laser Pumped By 1.9μm Tm Laser

The 2μm eye-safe laser is located in the atmospheric window, and can be widely used in laser medical, laser radar, environmental monitoring and optical communication, ect. Furthermore, 2μm laser is an efficient pump for 3~5μm broadband tunable mid-infrared optical parametric oscillators. Ho:YAG crystal become one of the preferred crystals that producing 2μm laser with high performance, in order to obtain high power, high efficiency 2μm laser as soon as possible, 2.1μm Ho:YAG laser and its pump source 1.9μm Tm:YLF laser have been carried on theoretical analysis and experiment research in this paper.Theoretically, according to Ho:YAG crystal physical, mechanical and spectral charateristics, the operation mechanism of 2.1μm Ho:YAG laser has been expounded at first; then on the basis of Ho3+ transition machanism, the quasi-two-energy rate equation model considering Ho-Ho up-conversion has been developed, and the laser threshold and output power has been solved according to the developed model; at last, the influences of up-conversion loss, output mirror transmittance, pump-laser mode ratio and crystal parameters on the Ho:YAG laser performance are theoretical simulated and analysized, which providing theoretical guidance for subsequent laser design and experiment.Experimentally, firstly, LD single-end pumped Tm:YLF laser is established, and the influence of output mirror transmittance, curvature radius and cavity length on laser performance are studied in turn to select the reasonable experiment parameters; Secondly, the single LD double-end pumped Tm:YLF laser with conventional mirror is carried, and obtained the 1908 nm laser output of 9.6W, with slope efficiency of 35.9% and optical-optical conversion efficiency of 29% repectively, the linewidth full-width half-maximum(FWHM) is over 2nm,and the wavelength redshift is from 1908.2nm to 1909.8nm as the increase of incident power; Fellow on, using coating volume bragg grating(VBG) instead of conventional mirror realized 8.8W 1908.2nm laser output, and line width is only 0.2nm, and wavelength reshift is less than 0.6nm; then single-pass pumped Ho:YAG laser experiment was conduct, also the influence of output mirror transmittance, curvature radius and cavity length on laser performance are studied in turn, under the condition of optimum output, the 2122 nm laser output of 4.6W is gained, and line width is only 0.2nm, with slope efficiency of 68.1% and optical-optical conversion efficiency of 53.2% repectively; Finally, an optimized design scheme of Ho:YAG laser with high power, high efficiency is proposed according to the analysis of experiment results.