Temperature variation of refractive index in GaSe.

Measurements of the ordinary refractive index of GaSe single crystals at various temperatures between 300 K and 75 K in the 0.5-2.5-eV energy range, obtained through an interference technique, are reported. On the basis of these data the energy dispersion of the thermal coefficient of the refractive index has been deduced by using a very simple computational approach. The experimental results were discussed in the framework of a single oscillator model of the optical constants.