Widely tunable dual-wavelength operation of Tm:YLF, Tm:LuAG, and Tm:YAG lasers using off-surface optic axis birefringent filters

In this work, we have demonstrated dual-wavelength continuous-wave laser operation in diode-end-pumped Tm:YLF, Tm:LuAG, and Tm:YAG lasers. A 3-mm-thick quartz birefringent filter with an optical axis 45° to the surface plane was exploited for achieving broadly tunable two-color laser operation. By using the different orders of the filter with varying filter width and free spectral range values, dual-wavelength operation has been achieved in 11, 12, and 8 different wavelength pairs in Tm:YLF, Tm:LuAG, and Tm:YAG, respectively. Fine tuning of the rotation angle of the birefringent filter enabled control of laser power in each line. To our knowledge, this is the first report of multicolor laser operation in these gain media, and the technique used is applicable to other laser operation regimes including mode-locking.