Effect of a High Electric Field on the Absorption of Light by PbI2and HgI2

Abstract

High electric fields produce a shift of the optical band edge to longer wavelengths in single crystals of Pb${\mathrm{I}}_2$ and Hg${\mathrm{I}}_2$. Fields in the range of ${10}^5$ to ${10}^6$ v/cm cause shifts of the band edge up to 30 A. The magnitude of the shift is proportional to the square of the applied field in agreement with the theoretical prediction of Franz. Using ac fields, the frequency response of the effect has been followed up to 5 kc/sec with no observable inertia.