Xiangkui Ren

Modes of photorefractive surface waves

We consider the modes of surface waves with the diffusion mechanism by the band transport model of the photorefractive effect and the nonlinear equation for the first time. We demonstrate the relationship between the modes of surface waves and the angles of incidence. The conditions for the realization of surface modes at the interface between photorefractive crystal and a metal, a linear dielectric with a lower refractive index, or another photorefractive crystal are discussed.

Photorefractive surface waves at the interface of Sr0.6Ba0.4NbO3 and air with diffusion mechanism

Photorefractive surface waves on the surface of Sr0.6Ba0.4NbO3 with a diffusion mechanism of nonlinearity have been observed. The formation time of the photorefractive surface waves is related to the intensity of the incident beam and the background illumination. The formation time of the photorefractive surface waves is about 40 min with a beam intensity of 3 mW, 25 min with 10 mW, and 30 s with 10 mW when an additional background illumination is applied. The experimental results showed that an appropriate background illumination will shorten the photorefractive response time.

Photorefractive lattice surface waves with diffusion nonlinearity

We introduce what we believe to be a new type of nonlinear surface wave, photorefractive lattice surface wave, which can form at the interface between uniform linear media and periodic optical lattice with nonlocal photorefractive diffusion nonlinearity. This type of surface wave originates not only from the gaps but also from the bands of the optical bandgap structures, which are different from surface lattice solitons and can be classified into three kinds, i.e., band lattice surface wave, gap lattice surface wave, and outside bandgap lattice surface wave. The diffusion nonlinearity ensures the concentration of light energy near the boundary of optical lattice and brings a downward shift of the optical bandgap structure.

Surface waves in two-photon photorefractive media

We present the evolution equation of surface waves due to the two-photon photorefractive effect. It is shown theoretically that the surface waves can be supported by two-photon photorefractive media. The spatial frequency of photorefractive surface waves can be changed by an applied external electric field, which indicates a method for transforming the surface waves between high-frequency modes and low-frequency modes.

Photorefractive surface waves in liquid crystal

We predict the formation of electrically and optically controlled photorefractive surface waves in liquid crystal, with orientational photorefractive effects. In contrast to the case for photorefractive surface waves in inorganic crystals, the penetration depth of photorefractive surface waves in liquid crystal can be controlled by means of the applied external electric field, while the position of the photorefractive surface waves in the liquid crystal can be controlled by means of the applied external electric field and the polarization of incident light beams.