Coherent signal beam amplification in two-wave mixing experiments with photorefractive Bi12SiO20 crystals

Abstract The amplification of the input signal beam in two-wave mixing experiments with photorefractive Bi 12 SiO 20 crystals is achieved when an additional phase shift is established between the photoinduced index modulation (phase volume hologram) and the incident fringe pattern. This stationary phase shift is introduced by either moving the crystal or the interference fringes at a constant speed. The transferred intensity is measured versus the applied electric field, fringe spacing and crystal velocity. The crystallographic orientation and the relative displacement with respect to the applied electric field polarity determine the amplitude of the energy transfer. For the first time in this crystal, signal beam amplification is reached for an applied field E 0 > 8 kV cm −1 and a crystal or fringe displacement speed around 5 μm s −1 at the green line ( λ = 514 nm ) of an argon laser.