Surface plasmon polaritons (SPPs) and Bloch surface waves (BSWs) have been widely utilized to design sensitive refractive index sensors. However, SPP- and BSW-based refractive index sensors require additional coupling component (prism) or coupling structure (grating or fiber), which increases the difficulty to observe ultra-sensitive refractive index sensing in experiments. Herein, we realize dramatic ellipsometric phase change at the band edges in an all-dielectric one-dimensional photonic crystal for oblique incidence. By virtue of the dramatic ellipsometric phase change at the long-wavelength band edge, we design an ultra-sensitive refractive index sensor at near-infrared wavelengths. The minimal resolution of the designed sensor reaches 9.28×10−8 RIU. Compared with SPP- and BSW-based refractive index sensors, the designed ultra-sensitive refractive index sensor does not require any additional coupling component or coupling structure. Such ultra-sensitive refractive index sensor would possess applications in monitoring temperature, humidity, pressure, and concentration of biological analytes.
We investigate the dual-band perfect absorption and their hybridization on multilayer tungsten disulfide (WS2) gratings with metallic substrates by the finite-difference time-domain method and the coupled-mode theory. Numerical results suggest that, under the illumination of the transverse magnetic polarized plane wave, the special multilayer WS2 grating with high refractive index not only allows the circulating-current-drove magnetic resonance but also provides additional wavevectors to excite the plasmonic resonance on the substrate surface simultaneously. Consequently, the dual-band perfect absorption is obtained in the single-port system by two independent critical coupling. The effect of small changes in the grating period, width, and height on spectral positions of absorption peaks is presented. The inherent multiple dielectric resonances on the WS2 grating under the illumination of the transverse electric polarized plane wave are also demonstrated. Intriguingly, the simultaneous existence of angle-independent magnetic resonances and angle-dependent plasmonic resonances gives rise to the obvious hybridization between the two types of resonances under the oblique incidence. Numerical results are in excellent agreement with theoretical calculations. The structure under study undoubtedly opens perspectives for enhancing light–matter interactions in two-dimensional materials.
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