Sellmeier equations, group velocity dispersion, and thermo-optic dispersion formulas for CaLnAlO_4 (Ln = Y, Gd) laser host crystals

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.