Giant strong coupling in a Q-BICs' tetramer metasurface.

Due to their ultrahigh Q-factor and small mode volume, bound states in the continuum (BICs) are intriguing for the fundamental study of the strong coupling regime. However, the strong coupling generated by BICs in one metasurface is not always strong enough, which highly limits its efficiency in applications. In this work, we realize a giant strong coupling of at most 60 meV in a quasi-BICs' (Q-BICs) tetramer metasurface composed of four Si cylinders with two different sets of diagonal lengths. The Q-BICs are induced from two types of electric quadrupole (EQ), for which detuning can be flexibly controlled by manipulating the C4v symmetry breaking Δd. The giant Rabi splitting in our proposed metasurface performs more than 15 times of the previous works, which provides more possibilities for important nonlinear and quantum applications, such as nanolaser and quantum optics.

Dynamically tunable multi-band quasi-permittivity-asymmetric BIC in the GST225 metasurface.

Bound states in the continuum (BICs) on metasurfaces have garnered significant interest for their ultrahigh Q-factor potential in sensing applications. Reconfigurability and multi-band resonance are highly desirable for sensing systems. In this work, we introduce a metasurface comprising four nanocubes with different permittivity asymmetries, which can be dynamically adjusted using Ge2Sb2Te5 (GST225), a phase-change material, in the near-infrared (NIR) region. Additionally, a simulation for a liquid molecule sensor based on the metasurface shows a sensitivity of 1017 nm/RIU. This research introduces a novel, to the best of our knowledge, approach for designing multi-band, dynamically tunable quasi-BIC metasurfaces, which are good candidates for tunable, high-sensitivity biochemical sensing and nonlinear optics applications.

InSb all-dielectric metasurface for ultrahigh efficient Si-based mid-infrared detection.

Mid-infrared (MIR) Si-based optoelectronics has wide potential applications, and its design requires simultaneous consideration of device performance optimization and the feasibility of heterogeneous integration. The emerging interest in all-dielectric metasurfaces for optoelectronic applications stems from their exceptional ability to manipulate light. In this Letter, we present our research on an InSb all-dielectric metasurface designed to achieve ultrahigh absorptivity within the 5-5.5 µm wavelength range. By integrating an InSb nanodisk array layer on a Si platform using wafer bonding and heteroepitaxial growth, we demonstrate three kinds of metasurface with high absorptivity of 98.36%, 99.28%, and 99.18%. The enhanced absorption is mainly contributed by the Kerker effect and the anapole state and the peak, with the added flexibility of tuning both the peak and bandwidth of absorption by altering the metasurface parameters. Our findings provide an alternative scheme to develop high-performance detectors and absorbers for MIR silicon photonics.

Integration of an InSb photodetector on Si via heteroepitaxy for the mid-infrared wavelength region.

In this study, InSb p-i-n photodetectors with In0.82Al0.18Sb barrier layers were grown on a (100) 6° offcut Si substrate by heteroepitaxy via an AlSb/GaSb buffer. Based on an interfacial misfit array growth mode, the dislocations at the GaSb/Si and InSb/AlSb interfaces accommodated the lattice mismatch. The In0.82Al0.18Sb barrier layer increased the 77 K R0A of the detector. From 180 K to 300 K, the generation-recombination mechanism dominated the dark current generation in the detector and surface leakage became dominant below 120 K. The detector exhibited a 77 K responsivity of 0.475 A/W and a Johnson-noise-limited detectivity of 3.08 × 109 cmHz1/2W-1 at 5.3 µm.