New Nonpolarizing Resonant Beam Splitters

We present wideband nonpolarizing beam splitters (NPBSs) for the telecommunication C-band. We show that silicon-on-insulator subwavelength periodic elements operating near leaky-mode resonance provide useful spectral expressions enabling effective beam division. Particle swarm optimization is the design method of choice. Periodic single-layer and multilevel NPBSs are provided exhibiting ~50/50 beam ratio under oblique and normal incidence. We compare the spectral performance of the beam splitters with that of their thin-film effective-medium counterparts, thereby verifying the resonance-mediated origin of the spectra sought. The beam splitters are found to be reasonably tolerant to deviations in angle of incidence and structural parameters.