Apodized waveguide arrays induced by photorefractive nonlinear surface waves.

ABSTRACT

A new type of nonlinear waveguides, photorefractive surface optical waveguides is suggested, which can be induced by photorefractive surface waves on the boundary of photorefractive crystal. The disturbed refractive index distribution of such waveguides behaves as a periodic lattice with apodized envelope, thus we call them photorefractive surface apodized waveguide arrays. Moreover, the dispersion relation and corresponding modes are analyzed. It is very interesting that the dispersion curves of index-guided modes and Bragg-guided modes couple and intertwine with each other, and anti-crossings instead of crossings between them hence generate some mini-gaps. Moreover there exists a type of extraordinary modes constituted by the splice of index-guided modes and Bragg-guided modes.