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

Abstract

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, dn_o/dT=-7.8, and dn_e/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.