E cavities are accountable for the operation of optical bistability at
E cavities are accountable for the operation of optical bistability at a low power. The all-dielectric guided-mode resonance (GMR) grating nanostructure is among the most significant nanoresonators for effective nonlinear photonic devices [127]. The GMR nanostructure fabricated in Kerr nonlinear components was studied for optical bistable devices [18]. The field inside the waveguide layer might be dramatically enhanced in the resonance wavelength to realize low-power optical bistability. Further, the GMR has higher degree of optical tunability for devices, for example wavelength, polarization, phase and intensity [18]. Most importantly, GMR nanostructures of large-scale patterning is usually fabricated by laser interference lithography or electron-beam lithography combining with nanoimprintNanomaterials 2021, 11, 2843. https://doi.org/10.3390/nanohttps://www.mdpi.com/journal/nanomaterialsNanomaterials 2021, 11,two oflithography for high-throughput and cost-efficient specifications [18]. The theoretical study on optical bistability in corrugated waveguides dates back greater than 30 years [19,20]. Numerous performs have been performed to boost the Q factor to lower the intensity threshold of optical bistability in GMR, including the coupled GMR nanostructures of air gaps [21], GMR of double-layer gratings [22], and low-index material embedded inside the waveguide layer [23]. Nonetheless, these solutions are somewhat complex for nanofabrication, along with the intensity threshold of optical bistability continues to be around the high-level of MW/cm2 . In current years, the optical BICs of ultra-high Q-factor has drawn considerably consideration, as a result of incredibly confined light field to dramatically enhance the light atter interaction for sensing, nanolasering and nonlinear optics [24]. The optical multistable behavior inside a one-dimensional Si photonic crystal slab of nonlinear BICs was predicted at the pump power of various /cm2 [25]. Having said that, the efficient Streptonigrin supplier refractive index modulation amplitude n is utilized within the short article, not the precise distribution of refractive index modulation related to nearby intensity, which can sensitively affect the optical transmission and reflection. The evolution of reflection or transmission with the modify in input intensity can also be lacking. So, Guretolimod custom synthesis further works are needed to study the optical bistable behavior in the resonance structures of BICs. Not too long ago, the GMR nanostructures consisting of a four-part grating layer of quasiBICs with ultra-high Q factors have been investigated for Goos chen shift and harmonic generation [26,27]. Within this paper, we additional investigate the optical bistability in GMR nanostructures of quasi-BICs. The complementary metal xide emiconductor (CMOS) compatible material silicon nitride (SiN) is employed to style the GMR structure. The temporal coupled-mode theory (TCMT) and finite element process (FEM) are employed to study the optical behaviors in nonlinear GMR nanostructures. Aided by the giant enhanced neighborhood field inside the waveguide in the quasi-BICs, the optical bistability of ultra-low threshold intensity at the amount of 100 W/cm2 is predicted. Importantly, the optical bistable devices functioning inside a broad band may be realized by changing the incident angles to tune the resonance wavelength of your nanostructures. The effects of typical defects of grating on the functionality from the optical devices are discussed. 2. Numerical Model and Material Parameters The schematic unit cell of the SiN MR structure on a fused silicon substrate is shown in Figure 1a, simi.