High-energy-pulse oscillation in 2.25–3.08 μm using Cr:CdSe pumped with Q-switched Tm:YAG laser

Summary form only given. High-energy pulsed mid-infrared (IR) lasers in the 2 to 3 μm range are of interested for various scientific and industrial applications such as laser radar, chemical sensing, and mid-IR laser processing. In addition the sources are useful as a pump light source for generating mid-IR waves longer than 4 μm in optical parametric oscillation. Cr:CdSe is one of attractive laser mediums for the efficient oscillation of optical pulses in the range, because of its wide tenability and large stimulated-emission cross-section [1]. MaKay et al. have reported a gain-switched nanosecond Cr:CdSe laser pumped with a 2.05 μm Q-switched Tm,Ho:YLF laser. The Cr:CdSe laser was tuned in the range of 2.32-2.88 μm and the output energy was 0.35 mJ at 2.5 μm [2]. Akimov et al. have also reported on a Cr:CdSe laser and increase the output energy up to 17 mJ around 2.65 μm by pumping with a Tm:YAP laser. The temporal pulse width was approximately 300 μs [3]. Generally, microsecond pulses are not suitable for laser radar and nonlinear frequency conversion. In this study, we report on a high-energy, nanosecond pulsed Cr:CdSe laser. We adopted a Z-fold cavity using folding mirrors with a curvature of 1000 mm to realize large fundamental-mode beam radius (-0.6 mm) on the Cr:CdSe surface. The large mode volume at the surface was effective for avoiding optical damage. Using a Q-switched Tm:YAG laser as a pump source, the maximum output energy of 4.4 mJ was accomplished at 2.64 μm. To the best of our knowledge, this is the highest output energy with nanosecond duration ever reported for a Cr:CdSe pulsed laser.