Improved selectivity of optical transmission through cascaded waveguide–metal-grating filters

We analyze the resonant transmission of two near-field coupled, cascaded bandpass filters, based on metallic stripe or patch gratings. The response, in terms both maximum efficiency and light rejection out resonance, overpasses simple convolution responses isolated while keeping good angular tolerance. Illustrations are given infrared visible ranges where technological integration such compact structures is particularly relevant for detection applications.