Photorefractive-index gratings formed by nanosecond optical pulses in BaTiO_3

Abstract

We write and read a refractive-index grating in a photorefractive crystal BaTiO(3) with a single 20-nsec laser pulse at 532 nm. The grating formed is erasable with similar pulses. Diffraction efficiency decreases exponentially with the cumulative erasing light energy for 20-nsec pulses at intensity levels of 5-30 MW/cm(2). Optical energies required to write and erase gratings with 20-nsec pulses are about an order of magnitude larger than for millisecond-to-to-second-long pulses at 515 nm, even though the grating is still formed by a one-photon process.