Forward and backward propagation guided-mode waves of electric dipole resonances in an h-BN metasurface

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The generation of a backward propagation (BP) and forward propagation (FP) guided mode in a double ridge h-BN metasurface (DRM) is investigated. h-BN is a hyperbolic metamaterial with two Reststrahlen frequency bands (RBs). The incident wave can excite guided modes in DRM, where the Poynting vector parallel component of the FP mode is identical and the BP mode is opposite to that of the incident wave. Based on the optimized structure, the frequency range of the BP mode for TE waves was found near the type II hyperbolic band (HB II), while for TM waves, it was found in the gap between the range of HB I and HB II in h-BN. To comprehensively understand the physics underlying BP and FP modes, we present the electric and magnetic field intensities in DRM, the electric field profile of beam steering, and the radiated powers of multipole resonances. The electric dipole (ED) moment contributes most significantly to the FP and BP modes, with its power being much greater than that of other multipolar moment modes. A proportion of BP mode power and incident power decreases with increasing incident angle of TE waves. There are two peaks of the proportion with TM waves. The maximum proportion is near 75% ofTE waves and 16% ofTM waves. The DRM has shown promising potential in the field of sensors based on BP mode, with a sensitivity of 3.9675 µm/RIU of TE waves and 5.1479 µm/RIU of TM waves. These findings suggest that DRMs hold significant promise for the development of optical metasurfaces, optical switches, and high-performance sensors.