Endlessly single-mode heat-sink waveguide

Summary form only given. Recently, a new form of optical fiber, the photonic crystal fiber, has been reported. This fiber has a hexagonal array of submicrometer air holes running along its length and a lattice site without a hole (a line defect) in its center. The defect acts as a core, confining light that travels along the fiber as a guided mode. This structure can be endlessly single mode, never supporting more than one confined mode no matter what the diameter of the core or the wavelength of the light. Having discovered this effect experimentally and provided a qualitative explanation for the observed behavior, we present here a planar version of this fiber. Periodic arrays of parallel planar fins are placed on both sides of and perpendicular to a central plate of the same high-index material, giving a structure that resembles a heat sink. The central plate acts as a defect in a one-dimensional periodic cladding, made up of the fins and the material between them. In contrast to the photonic crystal fiber, this structure is analytically tractable using an adapted transfer-matrix method, which has some features in common with the treatment of multilayer planar waveguides. This involves matching the Bloch wave fields of the cladding to plane waves within the defect layer.