Materials science

Refractive index

Band-stop filter

Low-pass filter

Coupled mode theory

Computer science

Silicon

Guided-mode resonance

Wavelength

Filter (signal processing)

Physics

Optical filter

Optics

Resonator

Diffraction grating

Stopband

Optoelectronics

Computer vision

Journal of Lightwave Technology

A silicon metasurface with a symmetry-protected quasi-dark resonant mode is designed and demonstrated as a refractometric sensor and tunable notch filter in the near-infrared spectrum. The resonant mode is excited by perturbing a periodic array of Si cuboids patterned on a glass substrate. Thanks to the delocalized nature of the resonant mode, intense light-matter interaction with the overlayer material is manifested. Such interaction leads to strong dependence of the resonant wavelength on the overlayer refractive index and high achievable quality factors, including the case of lossy materials. High sensitivity and figure of merit is calculated for operation of the metasurface as a refractometric sensor. In a complementary approach, three types of tunable notch filters are demonstrated, based on the use of thermo-optic, electro-optic polymers, and nematic liquid crystals.

Quasi-Dark Resonances in Silicon Metasurface for Refractometric Sensing and Tunable Notch Filtering