Narrowband, polarization-independent free-space wave notch filter
Abstract
A two-dimensional-corrugated-slab-waveguide add/drop filter providing 100% resonant reflection at 1.55 µm wavelength for both TE and TM polarizations with identical FWHM is designed. The fabricated device exhibits a reflectivity spectrum of more than 95% peak reflection for both polarizations at 1.537 m. The coupling scheme involves the TE0 guided mode only; it is made relatively tolerant by means of a double-sided crossed grating