Coherent light amplification and optical phase conjugation in photoconductive electro-optic materials

The electric field and fringe spacing dependence of the stationary energy transfer between two writing beams in volume phase-hologram formation with photoconductive electro-optic materials (KNbO3:Fe2+, Bi12(Si, Ge)O20) has been studied. Experimental results are compared with the theoretical expressions describing the influence of the different photoinduced space-charge fields in photorefractive media. A peak exponential gain of Γ = 15 cm-1 has been reached in KNbO3:Fe2+ for the proper choice of experimental parameters such as recording wavelength, fringe spacing, applied electric field etc.).Results of the electric field dependence of the wave front reflectivity ρ in degenerate four-wave mixing experiments are reported and discussed in terms of a similar theoretical treatment as the two-wave mixing experiments. It is shown, that peak reflectivities of ρ = 10 percent have been reached for KNbO3:Fe2+, that conjugate complex wave fronts can be generated and that distorted optical wave fronts can be effectiviely corrected by four-wave mixing experiments in KNbO3:Fe2+.