Full Resonant Transmission of Semiguided Planar Waves Through Slab Waveguide Steps at Oblique Incidence

Sheets of slab waveguides with sharp corners are investigated. By means of rigorous numerical experiments, we look at oblique incidence of semiguided plane waves. Radiation losses vanish beyond a certain critical angle of incidence. One can thus realize lossless propagation through 90^\circ corner configurations, where the remaining guided waves are still subject to pronounced reflection and polarization conversion. A system of two corners can be viewed as a structure akin to a Fabry-Perot interferometer. By adjusting the distance between the two partial reflectors, here the 90^\circ corners, one identifies step-like configurations that transmit the semiguided plane waves without radiation losses, and virtually without reflections. Simulations of semiguided beams with in-plane wide Gaussian profiles show that the effect survives in a true 3-D framework.