Instantaneous characteristics study of the diffracted and transmitted light of a static photorefractive reflection volume holographic grating read by an ultrashort pulse laser

The time-domain diffraction and transmission of reflection volume holographic gratings (RVHGs) recorded in photorefractive LiNbO3 crystals are theoretically studied and compared with transmission volume holographic gratings (TVHGs) when they are illuminated by ultrashort pulse laser light. The modified Kogelnik's coupled-wave theory, combining the dispersion effect in the crystal, is used. The results show that larger diffraction intensity can be obtained by choosing a larger grating period, grating thickness and modulation index for a given pulse duration. The RVHG has higher diffraction intensity than the TVHG with the same grating parameters. Also, it is found that the diffracted pulse of the RVHG and the TVHG shift in opposite directions along the time-axis. The values of the shifts are functions of the readout pulse duration and grating parameters. The overmodulation phenomenon appears in the diffracted pulse of the TVHG at high values of the grating thickness and refractive index modulation, but it does not occur in the RVHG. The results of our study can be used in choosing proper grating parameters for pulse shaping and signal processing applications