  Highly directional and lossless surface wave has significant potential
applications in the two-dimensional photonic circuits and devices. Here we
experimentally demonstrate a selective Dyakonov surface wave coupling at the
interface between a transparent polycarbonate material and nematic liquid
crystal 5CB. By controlling the anisotropy of the nematic liquid crystal with
an applied magnetic field, a single ray at a certain incident angle from a
diverged incident beam can be selectively coupled into surface wave. The
implementation of this property may lead to a new generation of on-chip
integrated optics and two-dimensional photonic devices.
