Light storage in wavy dielectric grating with Kerr nonlinearity

Periodical corrugation in dielectric slab transfers the two waveguide modes at zero Bloch wave number into a leaky resonant mode and a symmetry protected bound states in the continuum (BIC) with small frequency detune. The leaky resonant mode can be directly excited by weak linearly polarized normally incident optical field. In the presence of Kerr nonlinearity, the BIC can be indirectly excited by an optical bistable response. Two types of bistable operations are considered. For the first type, the intensity of the incident field gradually increases to exceed a critical value, and then decreases to zero. For the second type, the intensity is fixed, while the linear polarization angle of the incident field gradually increases to exceed a critical value, and then decreases to 0$^{o}$. Theoretically, the indirectly excited BIC can store the optical energy without loss, even though the intensity of the incident field decreases to zero. Incidence of an optical field with double frequency or orthogonal linear polarization can erase the stored optical field by destroying the BIC. The proposed optical system could function as optical storage and switching device.