Thermo-optic dispersion formulas for YCOB and GdCOB laser host crystals

We report on a comparative study of anisotropy and dispersion of thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path for monoclinic oxoborate YCOB and GdCOB laser host crystals. Near 1 μm, all dn/dT coefficients are found to be negative: dnX/dT = –1.2, dnY/dT = –3.7 and dnZ/dT = –2.5 × 10−6 K−1 for YCOB, dnX/dT = –3.8, dnY/dT = –4.8 and dnZ/dT = –3.7 × 10−6 K−1 for GdCOB. Thermo-optic dispersion formulas are derived for these crystals in the spectral range of 0.4–2 μm. The existence of athermal directions is predicted for both YCOB and GdCOB