• • BIC-enabled nonlinear conversion: second-harmonic generation (SHG) in all-dielectric quasi-BIC resonators achieves ultimate conversion efficiency limited primarily by nonlinear refraction of dielectrics, with experimental demonstrations in WS2 monolayers and MoS2 hybrid metasurfaces showing enhancement factors exceeding 10^3 relative to unpatterned films—critical for compact frequency-conversion devices where legacy birefringent crystals fail at sub-wavelength scales.
• • Dynamic tunability via phase-change materials: thermally switchable metalenses based on quasi-BICs demonstrate reversible focal length modulation with switching energies below 1 nJ per pixel and cycling stability >10^4 cycles, enabling reconfigurable optical systems that eliminate mechanical actuation and reduce system-level power consumption by an order of magnitude.
• • High-Q sensing and imaging: quasi-BIC edge-detection imaging achieves spatial resolution of 1.5 µm with a noise-equivalent power below 100 pW/Hz^0.5, outperforming conventional guided-mode resonance filters by suppressing background transmission to <0.1%—directly applicable to real-time biomedical diagnostics and machine-vision pre-processing.
• • Polarization-independent nonlinear enhancement: doubly degenerate quasi-BICs in lithium niobate metasurfaces yield third-harmonic generation enhancement factors of ~10^2 with polarization-independent operation, removing a key bottleneck in free-space optical interconnects where polarization scrambling causes >3 dB insertion loss penalties.