Parametric study of photorefractive beam coupling in BaTiO3 at multiple wavelengths
TL;DR: In this paper, the photorefractive signal beam gain is measured as a function of the pump beam intensity, beam ratio intensity, spatial frequency of the grating, and angle between grating vector and c axis of the crystal.
Abstract: photorefractive two-beam coupling and energy transfer in BaTiO3 are studied at multiple wavelengths using He-Cd, He-Ne, and diode lasers. The photorefractive signal beam gain is measured as a function of the pump beam intensity, beam ratio intensity, spatial frequency of the grating, and angle between the grating vector and c axis of the crystal. The exponential gain coefficient is calculated from signal beam gain, and its dependence on the same parameters is studied. The dependence of the signal beam gain and exponential gain coefficient on spatial frequency are also evaluated theoretically and found to be in good agreement with the experimental data. Also, the signal beam gain is studied as a function of wavelength, and a very high value is obtained at 441.6 nm. Figure-of-merit parameters such as the maximum change in the refractive index, the space charge field at saturation, the trap density of the charge carriers, and the photorefractive sensitivity of the crystal are calculated from the experimental data. since the absorption in BaTiO3 varies strongly with wavelength, its influence has been included in the calculations of the figure-of-merit parameters. The results are discussed in the light of the present understanding of photorefractive phenomena in crystals.
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