Photoelastic constants of potassium chloride at 106 μm

The piezooptic constants of pure KCl and KCl doped with KI have been measured in the visible and at 10.6 microm by interferometric and polarimetric techniques. The dispersion of the elastooptic constants, computed from the piezooptic constants, differs from the dispersion calculated from a theory based on a two-oscillator model of the refractive index.