The diffraction properties and applications of photorefractive volume holographic gratings

Photorefractive volume holographic grating (PVHG) is predicted to have attractive applications in optical communications and optical sensors due to its flexibility for fabricating, easy erasure and repeatable use. In this paper, we present some theoretical analyses and experimental results on the diffraction properties and applications of PVHGs in LiNbO₃:Fe crystal. Based on the angle selectivity of PVHG, the corresponding refractive index modulation depth and effective thickness are measured. Using these calculation values in addition to recording parameters, some special diffraction properties of PVHG can be designed. In order to avoid the polarization dependent diffraction efficiency due to the anisotropy of photorefractive crystals, double PVHGs are suggested to record in the same position of the crystal with two ordinary and extraordinary recording beams, respectively. As a filtering device, the PVHG can be well used to demodulate the wavelength reflected by a fiber Bragg grating. And the corresponding wavelength demodulation experiment is demonstrated in this paper.