In-band Pumping Ho³⁺-doped Solid-state Laser

The2μm eye safe laser sources are mostly produced bythe3F4â†'3H6transition ofTm3+and the5I8â†'5I7transition of Ho3+, The lasing wavelength (1.8μm-2.1μm)coincides with the strong water absorption and a wavelength region with excellentatmospheric transmission, making it very attractive for applications such as medicine,remote sensing, LIDAR and generation of3-5μm mid-infrared laser via pumpingnonlinear crystal (i.e. ZnGeP2). In this paper, high power and efficient operation ofHo:YAG laser in-band pumped by a Tm:fiber laser was shown.In theory, the main content of the research contain three parts. Firstly, based on thetheory of Ho3+ions quasi-three-level, we discussed threshold pump power and outputcharacteristics of the Ho:YAG laser, which in-band pumped by Tm:fiber laser at1907nm or1930nm. Secondly, according to the temperature and thermal effects of Ho:YAGcrystal, the relation of focus length of thermal lens with pump power was also analyzed.Finally, we shown the stable area of resonant cavity of single-rod and tandem-set rodsHo:YAG lasers.In experiments, the output characteristics of tunable Tm:fiber laser and Ho:YAGsolid-states laser ware studied. The experimental facilities of a tunable Tm:fiber laserand a tunable Tm:fiber master-oscillator power amplifier (MOPA) system were built.Based on fiber-bulk hybrid technique, The experimental facility of high-power andefficient operation of Ho:YAG laser, wing-pumped at1933nm using a self-builtTm:fiber laser, was also built.For tunable Tm:fiber laser, the single-stage oscillator lasing wavelength could betuned over140nm from1926nm to2070nm at output levels in excess of52W. TheMOPA laser was tuned over140nm (1936~2081nm) and obtained over54W ofcontinuous-wave (CW) output power over a tuning range of100nm from1962nm to2066nm with3.1W seed laser. For Ho:YAG laser, the output characteristics of single-rod and tandem-set rodsHo:YAG solid-states lasers ware studied. With the single-rod setup, a20.2of CWoutput power at2092nm and19.5W of CW output power at2124nm were generatedwith the10%and5%output coupler. Using two Ho:YAG rods in a tandemconfiguration to improve the overall pump absorption,24.2W of CW output power at2124nm was generated.