28 February 2014 Diode pumped tunable lasers based on Tm:CaF2 and Tm:Ho:CaF2 ceramics
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Abstract
The Tm:CaF2 (4% of TmF3) and Tm:Ho:CaF2 (2% of TmF3, 0.3% of HoF3) ceramics, prepared using hot pressing, and hot formation technique had been used as an active medium of diode pumped mid-infrared tunable laser. A fibre (core diameter 400 μm, NA = 0.22) coupled laser diode (LIMO, HLU30F400-790) was used to longitudinal pumping. The laser diode was operating in the pulsed regime (6 ms pulse length, 10 Hz repetition rate). The duty-cycle 6% ensures a low thermal load even under the maximum diode pumping power amplitude 25W (ceramics samples were only air-cooled). The laser diode emission wavelength was 786 nm. The 80mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.85 − 2.15 μm, HT @ 0.78 μm) and a curved (r = 150mm) output coupler with a reflectivity of ∼ 98% @ 1.85 − 2.0 μm for Tm:CaF2 laser or ∼ 99.5% @ 2.0 − 2.15 μm for Ho:Tm:CaF2. Tuning of the laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle. Both samples offered broad and smooth tuning possibilities in mid-IR spectral range and the lasers were continuously tunable over ∼ 100 nm. The obtained Tm:CaF2 tunability ranged from 1892 to 1992nm (the maximum output energy 1.8mJ was reached at 1952nm for absorbed pumping energy 78 mJ). In case of Tm:Ho:CaF2 laser tunability from 2016 to 2111nm was reached (the maximum output energy 1.5mJ was reached at 2083nm for absorbed pumping energy 53 mJ). Both these material are good candidates for a future investigation of high energy, ultra-short, laser pulse generation.
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Jan Šulc, Jan Šulc, Michal Němec, Michal Němec, Helena Jelinková, Helena Jelinková, Maxim E. Doroshenko, Maxim E. Doroshenko, Pavel P. Fedorov, Pavel P. Fedorov, Vyacheslav V. Osiko, Vyacheslav V. Osiko, } "Diode pumped tunable lasers based on Tm:CaF2 and Tm:Ho:CaF2 ceramics", Proc. SPIE 8959, Solid State Lasers XXIII: Technology and Devices, 895925 (28 February 2014); doi: 10.1117/12.2040763; https://doi.org/10.1117/12.2040763
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