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A diode-pumped microchip laser containing a quasi-monolithic plano–plano cavity is realized on the basis of a $\mathrm{Tm}\text{:}\mathrm{KLu}{({\mathrm{WO}}_4)}_2$ crystal. The maximum CW output power is 3.2 W (at an absorbed pump power of 6.8 W) and the slope efficiency as high as 50.4%. The laser is operating at 1946 nm in the ${\mathrm{TEM}}_{00}$ mode with a ${\mathrm{M}}^2<1.05$. Microchip operation with $\mathrm{Tm}\text{:}\mathrm{KLu}{({\mathrm{WO}}_4)}_2$ is, in principle, due to a special crystal cut along the $N_g$ optical indicatrix axis. This crystal cut possesses positive near-spherical thermal lens that provides the required mode stabilization in the plano–plano cavity. Sensitivity factors of the thermal lens, “generalized” thermo-optic coefficients and constants describing the photoelastic effect are determined for the monolithic $\mathrm{Tm}\text{:}\mathrm{KLu}{({\mathrm{WO}}_4)}_2$ crystal.

We report on, to the best of our knowledge, the first sub-100 fs mode-locked ${\mathrm{Ho}}^{3+}$-laser in the 2 μm spectral range employing a disordered co-doped $\mathrm{Tm},\mathrm{Ho}\text{:}{\mathrm{CaYAlO}}_4$ (Tm,Ho:CALYO) crystal as a gain medium. Pulses as short as 87 fs are produced with an average output power of 27 mW at 80.45 MHz repetition rate. An output power of 96 mW is reached for a pulse duration of 98 fs.

GaSb-based SESAM is successfully employed for passive mode locking of a Tm³⁺:CaGdAlO₄ laser operating near 2 µm. The pulse duration is around 650 fs at a repetition rate ~100 MHz.

We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, $\mathrm{Ca}Ln{\mathrm{AlO}}_4$ ($Ln=\mathrm{Gd}$ or Y). Sellmeier equations were derived for the spectral range of 0.35–2.1 μm. The group velocity dispersion (GVD) in ${\mathrm{CaGdAlO}}_4$ is positive at $\sim 1\mathrm{\mu m}$, $95{\mathrm{fs}}^2/\mathrm{mm}$ and negative at $\sim 2\mathrm{\mu m}$, $-40{\mathrm{fs}}^2/\mathrm{mm}$. The GVD values for ${\mathrm{CaYAlO}}_4$ are similar. In addition, thermo-optic coefficients, $\mathrm{d}n/\mathrm{d}T$, and thermal coefficients of the optical path were determined for ${\mathrm{CaYAlO}}_4$. $\mathrm{d}n/\mathrm{d}T$ is negative at $\sim 1\mathrm{\mu m}$, $\mathrm{d}{n}_o/\mathrm{d}T=-7.8$, and $\mathrm{d}{n}_e/\mathrm{d}T=-8.7\times {10}^{-6}{\mathrm{K}}^{-1}$. Thermo-optic dispersion formulas were constructed. The obtained data are of key importance to the design of high-power mode-locked oscillators at $\sim 1$ and $\sim 2\mathrm{\mu m}$ based on such laser hosts.