All-optical self-switching with ultralow incident laser intensity assisted by a bound state in the continuum

We present a new, to the best of our knowledge, scheme of realizing all-optical switching by exploiting the phenomenon of the bound state in the continuum (BIC) supported by an array of slotted silicon disks. The air slot in an individual silicon disk works as a void antenna and can then help to excite the quasi-BIC (QBIC) mode by a linearly polarized plane wave. Thanks to the high quality factor of the QBIC resonance and the associated large local electric field enhancement, the self-switching effect is quite pronounced, and a laser power intensity level less than 1KW/cm² is required to achieve a change of transmittance from 0 to above 65%.