Experimental demonstration of 1D crossed gratings for polarization-independent high-Q filtering

We demonstrate experimentally a spectral filter with high Q-factor (≃3238), wide accordability range (1500-1600 nm) with respect to the angle of incidence, and record polarization independence. This work is an experimental validation of the theoretical work reported in [Opt. Lett. 36, 1662 (2011)]: the filter is composed of two 1D crossed gratings engraved on each side of a planar waveguide. We provide a good comparison with theory and physical interpretations of the features observed experimentally.

Tunable, polarization independent, narrow-band filtering with one-dimensional crossed resonant gratings

We propose an optical component for widely tunable, narrow-band filtering. It takes advantage of the tunability properties, with respect to the angle of incidence, of guided-mode resonance filters. The intrinsic polarization sensitivity of the resonances is suppressed by exciting the modes through two identical, differently oriented one-dimensional gratings flanking a thick substrate. An example is provided that theoretically shows a polarization independent peak at 1.6 μm with a Q factor of 13,000 and a reflectivity greater than 99% at resonance, which is tunable over 100 nm. Finally, we discuss the fabrication limitations and conclude that the proposed configuration is realistic.

Measurement and modeling of 2D hexagonal resonant-grating filter performance

We report the measurement of a polarization-independent guided-mode resonant filter with a Q factor of approximately 2200 functioning near normal incidence in the near infrared (850 nm). Besides this remarkable performance, we provide a detailed optical and structural characterization of the component, which points out the origins of the limitation of the experimental performance. We conclude that the defaults in question can be corrected by improving the lithography process, and we are confident that even greater performance will be obtained in future realizations.