Elasto-optical response of diamond at variable temperatures

The effect of temperature on the elasto-optical response of diamond is examined in the range 80--380 K for various photon energies below 5.5 eV. It is found that the elasto-optical constants exhibit a small linear decrease with increasing temperature. Theoretical results based on the contributions to piezobirefringence of various band-structure critical points show that such behavior can be attributed to the temperature dependence of the fundamental energy gap. The latter dependence is determined quantitatively from the present optical data. It is observed that the piezobirefringence measurements can give information about nonuniformities in the strain distribution.