Compact diode-pumped continuous-wave and passive Q-switched Tm:GdScO3 mixed sesquioxide crystal laser around 2.1 μm

Solid-state lasers operating around 2.1 μm have attracted significant interest due to their important applications. However, the development of 2.1 μm solid-state lasers has been limited by the lack of efficient pump sources, as well as thermal effects induced by energy transfer within the gain media. Therefore, addressing these challenges is essential for advancing 2.1 μm solid-state lasers. Here, we report the 2.1 μm laser characteristics of a laser diode (LD)-pumped Tm:GdScO₃ mixed sesquioxide crystal operating on the ³F₄ → ³H₆ transitions, including both continuous-wave (CW) and passively Q-switched (PQS) operations. In the CW regime, an uncoated quartz plate is used as the intracavity etalon for wavelength selection. The laser achieves a maximum average output power of 1.68 W at 2104.7 nm, corresponding to a slope efficiency of 19.7 %. To investigate the short pulse laser performance, PQS of the Tm:GdScO₃ laser is realized using a Cr:ZnSe saturable absorber. The laser delivers a maximum average output power of 0.48 W at 2100.8 nm, producing pulses with a shortest duration of 1.48 μs at a repetition rate of 19.98 kHz. The research results indicate that Tm:GdScO₃ is a promising gain medium for solid-state lasers, offering a new paradigm for the development of compact and economically viable 2.1 μm laser sources.