Abstract

We present a high-index contrast dielectric grating design for polarization-independent narrowband transmission filtering. A reduced symmetry hexagonal lattice allows coupling to symmetry-protected modes (bound states in the continuum) at normal incidence, enabling high-Q spectral peaks. The peak linewidth is tunable via degree of geometric symmetry reduction. Using diffraction efficiency calculations, we gain further insight into the design and physics of one-dimensional (1D) and two-dimensional (2D) asymmetric high contrast gratings. The grating design provides a filter response that is simultaneously polarization independent and functional at normal incidence, overcoming limitations of 1D asymmetric gratings and 2D symmetric gratings.

© 2020 Optical Society of America

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