Fig. 1. Energy band interpretation of BIC. (a) Schematic of continuum domains and bound states^[45]; (b) momentum space polarization field^[46]

Fig. 2. Topological explanation of BIC^[48]. (a) Schematic diagram of c_x and c_y nodal lines in momentum space; (b) possible configurations of polarization field near BIC

Fig. 3. Classification mechanism of BICs

Fig. 4. Strong coupling physical model^[66]. (a) Resonance interaction between two-level atom and confined electromagnetic field of resonator, resulting in two new hybrid states separated by Rabi splitting energy ħΩ_R; (b) double-peak transmission spectrum and relative transmission spectrum

Fig. 5. Strong coupling of BIC in two-dimensional materials. (a) Schematic of Si nanorod dimer metasurface arranged on SiO₂ substrate^[67]; (b) metasurface unit cell with detailed geometric description^[67]; (c) SEM image of metasurface when α=0.3^[67]; (d) calculated band structures of the dimer metasurface, and the inset denotes the schematic of the first Brillouin zone of square lattice^[67]; (e) structural schematic diagram supporting quasi-BIC resonance^[68]; (f) calculated anti-cross spectrum^[68]; (g) three dimensional schematic diagram of nanostructure^[69]; (h) mapping data of absorption spectra as a function of incident angle on nanostructures^[69]

Fig. 6. Strong coupling of BIC based on plasmon. (a) Schematic of the monolayer WS₂‒Ag nanohole hybrid structure^[73]; (b) SEM image of Ag nanohole array, and top-left inset shows an actual photograph of the sample, while the bottom-right corner shows a high-magnification SEM image^[73]; (c) calculated angle-resolved emission spectra^[73]; (d) TA spectra at different angles at 0.5 ps with an excitation wavelength of 420 nm^[73]; (e) schematic of the ultrasensitive quasi-BIC metasurface driven by strong mode coupling^[74]; (f) the system's sensitivity to nonradiative losses, in region IV, both coupled modes p and q exhibit low Q factors, and the resonator exhibits high sensitivity to nonradiative losses^[74]

Fig. 7. Microcavity laser based on BIC (UV‒visible‒infrared wavebands). (a) Schematic diagram of the manufactured quantum well BIC laser system^[75]; (b) directional laser emission in resonant GaAs nanowire arrays^[76]; (c) structure and laser output characteristics of TiO₂ dielectric nanowire array devices^[77]; (d) schematic diagram of GaN UV BIC laser and full width at half maximum of single-mode laser^[78]; (e) schematic diagram of Mini-BIC laser device (left) and micro-photoluminescence spectrum of cavity mode (right)^[79]; (f) merged BIC laser^[80]

Fig. 8. Exciton‒polariton laser. (a) Schematic diagram of room temperature BIC polariton condensation from CsPbBr₃‒PhC lattice with air holes^[86]; (b) tilted SEM image of CsPbBr₃‒PhC lattice with pores^[86]; (c) calculated energy dispersion of CsPbBr₃‒PhC lattice mode TM polarization^[86]; (d) calculated Q-factors of the four PhC lattice modes^[86]; (e) angle-resolved reflectance spectra of CsPbBr₃‒PhC lattice with air holes under TM polarization^[86]; (f) under quasi-CW excitation at 80 K, the integrated emission intensity as a function of the pump density of CsPbBr₃‒PhC lattice and original microcrystal^[86]; (g) schematic diagram of chiral laser emission from the designed metasurface^[87]; (h)‒(j) LCP and RCP luminescence spectra and their fitting results^[87]; (k) laser emission spectra^[87]

Fig. 9. Topological laser based on organic materials for BIC^[88]. (a) Schematic diagram of polariton BIC device with two-dimensional metasurface and the molecular structure of CzPVSBF; (b) TE resonance modes and their Q value near exciton emission in CzPVSBF calculated by finite element method; (c) polarization dispersion calculation based on strong coupling of photon mode and exciton resonance of CzPVSBF using computational method; (d) evolution of PL spectra from broadband to peak with pump energy, revealing an increase in the polariton condensation threshold of 0.30 μJ·cm^-2 and the temporal coherence of polariton emission; (e) relationship between polariton emission intensity and FWHM near θ=0° and pump flux; far-field patterns of (f) BIC2 and (h) BIC1 polariton condensates before and after passing through linear polarizers with different polarization orientations; polarization vector fields of (g) BIC2 and (i) BIC1 polariton condensates