Corrected infrared Sellmeier coefficients for gallium selenide

We have measured the room-temperature refractive indices of GaSe throughout the 0.7-1.4 and 2.4-5 mu m ranges using the minimum-deviation method of light through a prism with polarization either parallel (extraordinary refractive index n(e)) or perpendicular to the crystal optical c axis (ordinary refractive index n(o)). The birefringence (Delta n) at room temperature has been measured directly using polarized light interference fringes obtained in the transmittance from 1.73 to 4.97 mu m (three samples with thicknesses of 1108 +/- 1, 2480 +/- 1, and 2660 +/- 1 mu m) and in the range from 11.85-16.37 mu m (sample thickness of 6000 +/- 1 mu m). The n(o), n(e), and Delta n values determined from the positions of fringe maxima were compared to those obtained from prism measurements in the mid-IR and with previously published results which were mainly obtained by indirect methods. It was found that the prism method and interference fringe method resulted in values of n(o), n(e), and Delta n accurate to +/- 0.003 and +/- 0.006, respectively. (c) 2005 American Institute of Physics.