We demonstrate an external-cavity KGd(WO4)2 (KGW) Raman laser, pumped by an actively Q-switch Tm:YLF MOPA. The fundamental spectral line emitting at 1881 nm allowed the KGW bi-axial crystal to lase at two separate output spectral lines, 2198 and 2265 nm, depending on the seed polarization axis relative to the KGW's axis. The Tm:YLF seed was amplified using a double-pass Tm:YLF crystal based MOPA setup. After amplification, the seed achieved an output power of 9.15 W, and an energy pulse of 4.57 mJ, a pulse duration of 43 ns at a repetition rate of 2 kHz. The max output average power achieved for the 2265 nm was 1.85 W, with a pulse energy of 0.923 mJ at a repetition rate of 2 kHz implying a conversion efficiency of ~20.5%. We noticed a very low conversion efficiency of the shorter KGW spectral shift (at 2198 nm). The reason for this efficiency drop was validated to be the 2nd stokes forming and thus consuming the 1st stokes energy. In favor of the KGW inherent properties and according to the aforementioned results, this crystal appears to be suitable for power scaling as well as for improvement of the Raman conversion efficiency in this spectral range. The KGW crystal is well known for its use in shorter spectral wavelengths. To the best of our knowledge, it is the highest average power achieved by lasing in the 2 μm region using SRS with KGW.
Tunable and milli-Joule level pulsed Tm based laser, are demonstrated in this paper. The spectral bandwidth was narrowed down to 0.15 nm FWHM. For the Actively Q-switched Tm:YLF laser, we achieved 33 nm of tunability range between 1873 nm and 1906 nm, using a pair of YAG Etalons. Using the same tunability technic for the Passively Qswitched Tm:YAP laser, we achieved 11 nm of tunability between 1930-1941 nm. The Tm:YLF laser was actively Qswitched using an acousto-optic modulator, while achieving mJ level pulse energy along the whole tuning range at a repetition rate of 1 kHz. Up to 1.97 mJ of energy per pulse was achieved at a pulse duration of 37 ns at a wavelength of 1879 nm, corresponding to a peak-power of 53.2 kW and at a slope efficiency of 36 %. The Tm:YAP laser was Passively Q-switched using Cr:ZnS saturable absorber (SA) as modulator, achieving mJ level pulse energy along the whole tuning range. Up to 1.2 mJ of energy per pulse was achieved at a pulse duration of 24 ns at a wavelength of 1935 nm, corresponding to a peak-power of 50 kW. The combination of both high energy pulsed lasing and spectral tunability, while maintaining narrow bandwidth across the whole tunability range, enhances the laser abilities, which could enable new applications in the sensing, medical and material processing fields. Which in the case of the of the Passively Qswitched Tm laser has a major advantage in terms of foot print.