Adaptive running hologram recording and phase-shift measurement inphotorefractive crystals

摘要

The author reports the use of phase modulation techniques intwo-wave mixing (2WM) experiments for measuring the phase shift ψbetween the interference pattern projected onto a photorefractivecrystal and the resulting recorded hologram, as a function of theexternally applied electric field E. Such data are used for computingthe photoelectron trap density N_A in the crystal. Phasemodulation techniques in conjunction with an adaptive fringe-lockingmethod was also applied for running hologram recording under appliedfield E, which allows both matching of optimal recording conditions andmeasuring the `resonance' hologram velocity v_o. From v_o vs. E data, the diffusion length L_D and thephotoelectron generation rate g_o are found and the quantumefficiency for the process may be computed. Experimental results for Bi₁₂SiO₂₀ (BSO) and Bi₁₂TiO₂₀(BTO) are reported