Confinement and guiding of two-dimensional optical waves by low-refractive-index cores

A new method for confining and guiding two-dimensional (2D) optical waves is proposed using low-refractive-index materials as cores of metal-gap waveguides. A proper choice of the refractive index of claddings prohibits 2D optical waves from propagating inside the claddings, resulting in strong confinement of waves inside the low-refractive-index cores. We numerically demonstrate that this new method for guiding 2D optical waves can achieve stronger confinement than the conventional one using high-refractive-index cores. This strong confinement leads to efficient guiding of 2D optical waves not only at straight path, but also at sharp 90 degrees bends with negligible radiation losses. (c) 2006 Optical Society of America.