Photoinduced dichroism in thin films of amorphous As/sub 2/Se/sub 3/

We have measured the dichroism in amorphous As₂Se₃ induced by a polarized beam of near band-gap light (632.8 nm). Most glassy material is initially isotropic and homogeneous. When As₂Se₃ absorbs an intense pump-beam of polarized light, the absorption coefficient for light polarized in the same direction as the pump-beam is less than for the perpendicular polarization, i.e. the sample becomes anisotropic (dichroic). Induced dichroism is potentially useful in various photonic devices including optical switches, optical memory, and polarizers. In our experiments, the total induced dichroism amounts to 0.24% after 10 minutes of illumination by polarized laser light (632.8 nm) with an intensity of 130 mW/cm². The induced dichroism is reversible by rotating the polarization of the pump light by 90deg. A total change of 0.48% is achieved between the two orthogonal states. We find that the time dependence of the induced dichroism fits a stretched exponential function