Multi-parameter BIC control and high-sensitivity sensing characteristics based on all-dielectric elliptical holes
Abstract
<p indent="0mm">In the field of micro-nano biosensors, it is important to study metasurfaces with an ultra-high quality factor (<italic>Q</italic>). Bound states in the continuum (BIC) have attracted much attention due to their infinite <italic>Q</italic> factor and zero linewidth in theory. In this study, an all-dielectric elliptical hole sensor based on BIC with ultra-high sensitivity is proposed. By systematically adjusting four parameters, such as the long and short axis size and the rotation angle of the two elliptical holes at the diagonal position, the symmetry-protected BIC (SP-BIC) supported by the device is excited. Compared with the single method of traditional BIC regulation, this method is more flexible and diverse, and provides higher design freedom and optimization space. The collaborative regulation of multiple parameters also provides design ideas for the realization of dual-channel and multi-channel quasi-bound states in the continuum (QBIC) resonances. The electromagnetic field of this symmetry-protected resonance mode can be expanded in multiple expansions. It is found that QBIC resonance modes are mainly excited by magnetic quadrupole (MQ) and toroidal dipole (TD) modes, in which MQ makes the main contribution to the resonances. The resonance <italic>Q</italic> factor excited by the device can reach 10<sup>5</sup> orders of magnitude. Using its ultra-high quality factor, an ultra-high sensitivity refractive index sensor is designed. The sensitivity of the sensor reaches 276 nm/RIU, and the figure of merit (FOM) can be as high as 7000. The sensing performance is greatly improved compared with previous studies. The metamaterial device has great application prospects in the fields of biosensors, optical switches, and filter devices.</p>
