Optically-pumped mid-infrared Tm:LuScO3 crystal laser at 2.1 and 2.3 μm with high slope efficiency

Abstract

It is a substantial interest of mid-infrared coherent sources for a broad range of science and technology applications, including those in spectroscopy, detection, and information technology. However, compared to the mature near-infrared lasers around 1 μm, the output power and lasing efficiency of mid-infrared lasers at 2.1 and 2.3 μm were still underdeveloped. Here, we reported the optically-pumped mid-infrared laser generation in the mixed Tm³⁺:LuScO₃ sesquioxide crystals. In order to improve the lasing efficiency, two different pump sources were adopted, that fiber-laser at 1.7 μm for the in-band pumping and diode-laser at 790 nm for the resonant pumping with high quantum efficiency. For the ³F₄ → ³H₆ transition, we realized the mid-infrared laser at 2122–2129 nm with the highest slope efficiency of 33.8 % and 50.2 % via the in-band and resonant pumping, respectively. To our knowledge, these results represent one of the highest slope efficiencies in the Tm³⁺-doped sesquioxides laser around 2.1 μm. In addition, the continuously tunable lasers at 2019.4 – 2165.4 nm and 1994.9 – 2140.4 nm were also realized in different pumping setups. Finally, using the resonant-pumping at ³H₄ → ³H₅ transition, we achieved the first diode-pumped laser at 2.3 μm in Tm³⁺-doped sesquioxide crystal, and the maximum output power was 751 mW with a high slope efficiency of 20.3 %. Accordingly, Tm:LuScO₃ crystal should be an excellent gain medium for the highly efficient mid-infrared laser generation at 2.1 and 2.3 μm.