Nonlinear absorption of light in glassy arsenic sulfide fibers in the energy range hν<Eg

Nonlinear absorption of light was discovered in waveguides made of glassy arsenic sulfide at hν<E_g. The transmission of the fibers at λ =0.63 μ varied severalfold as a function of the intensity of the radiation, and of the time for which it acted, for intensities exceeding 1 W/cm². The recovery of the transmission coefficient also depended on the exposure conditions. The results obtained were interpreted on the basis of a two-step transition model.