Efficient Tm:YAG and Tm:LuAG lasers pumped by 681 nm tapered diodes
Appl. Opt., vol. 58, no. 11, pp. 2973-2980 (2019).
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In this paper, we present highly efficient continuous-wave (cw) laser operation of Tm:YAG and Tm:LuAG lasers pumped by high-brightness red tapered diodes. The single-emitter tapered diode lasers (TDLs) provide up to 1W of pump power around 680 nm. By adjusting the operation temperature of the TDL, the pump central wavelength could be matched to the strong absorption peak of Tm3+ ions in this region (3H6 → 3F3 excitation). This absorption peak is around threefold stronger than the usually employed 785 nm transition (3H6 → 3H4). In the cw laser experiments, we have achieved slope efficiencies exceeding 55% at room temperature, which is far above the Stokes limited slope efficiency (34%), indicating presence of a strong two-for-one cross-relaxation process. Pumping with high-brightness tapered diode lasers further facilitated usage of smaller pump spots (enabling quite low lasing thresholds) and generation of near-diffraction limited output beam profiles from standard z-type cavities. To the best of our knowledge, this is the first report of diode pumping of Tm-doped solid-state lasers around 680 nm as well as the first usage of TDLs as pump sources in Tm-doped laser systems.
1 Department of Electrical-Electronics Engineering, Recep Tayyip Erdogan University, Rize 53100, Turkey
2 Ferdinand-Braun-Institut, Leibniz Institut für Höchstfrequenztechnik, D-12489 Berlin, Germany
3 Laser Technology Laboratory, Department of Electrical and Electronics Engineering, Antalya Bilim University, 07190 Antalya, Turkey
4 Center for Free-Electron Laser Science, Deutsches Elektronen Synchroton (DESY), Hamburg, Germany