We present the first sub-100 fs bulk solid-state laser in the 2-μm spectral range employing the monoclinic Tm-dopedMgWO crystal as an active medium. By applying a graphene-based saturable absorber and chirped mirrors for dispersion management, stable self-starting mode-locked operation at 2017 nm was achieved. Nearly Fourier-limited pulses as short as 86 fs featuring a bandwidth of 53 nm were generated at a repetition rate of 76 MHz. A pulse energy of 1.1 nJ was achieved at 87 MHz for a pulse duration of 96 fs. The mode-locked Tm:MgWO laser exhibits excellent stability with a fundamental beat note extinction ratio of 80 dBc above noise level.
We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, CaLnAlO4 (Ln=Gd or Y). Sellmeier equations were derived for the spectral range of 0.35-2.1 μm. The group velocity dispersion (GVD) in CaGdAlO4 is positive at ∼1 μm, 95 fs2/mm and negative at ∼2 μm, -40 fs2/mm. The GVD values for CaYAlO4 are similar. In addition, thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path were determined for CaYAlO4. dn/dT is negative at ∼1 μm, dno/dT=-7.8, and dne/dT=-8.7×10-6 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 ∼1 and ∼2 μm based on such laser hosts.
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