An optical device provides optical routing functions, such as switching or redirecting of optical signals. The device utilizes one or more control light beams, which couple through a top surface of a planar substrate (via relatively small control windows) into one or more preselected regions of optical channels formed in the substrate. The presence of a control light beam at a control window increases the refractive index of the nonlinear optical medium of a portion of a channel. The portion of the channel includes a structure that functions as an on/off filter to reflect or transmit an optical signal propagating in the channel in a manner that is responsive to the intensity of the control light beam applied to the portion of the channel. In some embodiments, the optical channels interrupt a 2D PBG structure, which functions as a boundary for the optical channels.