Measurement of thermooptic coefficients dnE/dT and dnO/dT of AgGaS2 at 308 and 97 K

Thermooptic coefficients (dn_E/dT and dn_O/dT) of AgGaS₂ have been measured at temperatures of ∼308 and 97 K, using temperature-induced shift in the frequency of the interference fringes in the Fourier transform infrared (FTIR) transmittance spectrum of a 2-mm-thick etalon. Values of dn_E/dT and dn_O/dT are reported for the spectral regime from 12.4 μm to 1.06 μm; the subscripts E and O refer to extraordinary and ordinary rays, respectively. Our values of dn_E/dT and dn_O/dT at 308 K are significantly lower (∼1/3) than those reported previously.