Manipulating Dual Bound States in the Continuum for Efficient Spatial Light Modulator

Plasmonic Bound States in the Continuum Metasurface-Semiconductor-Metal Architecture Enables Efficient Hot-Electron-Based Photodetector

Plasmonic hot-electron-based photodetectors (HEB-PDs) have received widespread attention for their ability to realize effective carrier collection under sub-bandgap illumination. However, due to the low hot electron emission probability, most of the existing HEB-PDs exhibit poor responsivity, which significantly restricts their practical applications. Here, by employing the binary-pore anodic alumina oxide template technique, we proposed a compact plasmonic bound state in continuum metasurface-semiconductor-metal-based (BIC M-S-M) HEB-PD. The symmetry-protected BIC can manipulate a strong gap surface plasmon in the stacked M-S-M structure, which effectively enhances light-matter interactions and improves the photoresponse of the integrated device. Notably, the optimal M-S-M HEB-PD with near-unit absorption (∼90%) around 800 nm delivers a responsivity of 5.18 A/W and an IPCE of 824.23% under 780 nm normal incidence (1 V external bias). Moreover, the ultrathin feature of BIC M-S-M (∼150 nm) on the flexible substrate demonstrates excellent stability under a wide range of illumination angles from -40° to 40° and at the curvature surface from 0.05 to 0.13 mm-1. The proposed plasmonic BIC strategy is very promising for many other hot-electron-related fields, such as photocatalysis, biosensing, imaging, and so on.

Tunability-selective lithium niobate light modulators via high-Q resonant metasurface

Herein, we propose and demonstrate an efficient light modulator by intercalating the nonlinear thin film into the optical resonator cavities, which introduce the ultra-sharp resonances and simultaneously lead to the spatially overlapped optical field between the nonlinear material and the resonators. Differential field intensity distributions in the geometrical perturbation-assisted optical resonator make the high quality-factor resonant modes and strong field confinement. Multiple channel light modulation is achieved in such layered system, which enables the capability for tunability-selective modulation. The maximal modulation tunability is up to 1.968 nm/V, and the figure of merit (FOM) reaches 65.6 V-1, showing orders of magnitude larger than that of the previous state-of-the-art modulators. The electrical switch voltage is down to 0.015 V, the maximal switching ratio is 833%, and the extinction ratio is also up to 9.70 dB. These features confirm the realization of high-performance modulation and hold potential for applications in switches, communication and information, augmented and virtual reality, etc.

Dynamic light manipulation via silicon-organic slot metasurfaces

Active metasurfaces provide the opportunity for fast spatio-temporal control of light. Among various tuning methods, organic electro-optic materials provide some unique advantages due to their fast speed and large nonlinearity, along with the possibility of using fabrication techniques based on infiltration. In this letter, we report a silicon-organic platform where organic electro-optic material is infiltrated into the narrow gaps of slot-mode metasurfaces with high quality factors. The mode confinement into the slot enables the placement of metallic electrodes in close proximity, thus enabling tunability at lower voltages. We demonstrate the maximum tuning sensitivity of 0.16nm/V, the maximum extinction ratio of 38% within ± 17V voltage at telecommunication wavelength. The device has 3dB bandwidth of 3MHz. These results provide a path towards tunable silicon-organic hybrid metasurfaces at CMOS-level voltages.

High-performance etchless lithium niobate layer electro-optic modulator enabled by quasi-BICs

A facile strategy is proposed for a high-performance electro-optic modulator with an etchless lithium niobate (LN) layer assisted by the silicon resonator metasurface, which pioneers the way to engineer an ultra-sharp spectral line shape via the excitation of quasi-bound states in the continuum (BICs). Meanwhile, strong out-of-plane electric/magnetic fields within the proximity area to the electro-optic layer lead to ultra-sensitive modulations. As a result, only a slight voltage change of 0.2 V is needed to fully shift the resonances and then realize switching modulation between the "off" and "on" states. The findings pave new, to the best of our knowledge, insights in reconfiguration of spatial optical fields and offer prospects for functional optoelectronic devices.

Manipulating Coupled Field Enhancement in Slot-under-Groove Nanoarrays for Universal Surface-Enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) is an ultrasensitive spectroscopic technique that can identify materials and chemicals based on their inelastic light-scattering properties. In general, SERS relies on sub-10 nm nanogaps to amplify the Raman signals and achieve ultralow-concentration identification of analytes. However, large-sized analytes, such as proteins and viruses, usually cannot enter these tiny nanogaps, limiting the practical applications of SERS. Herein, we demonstrate a universal SERS platform for the reliable and sensitive identification of a wide range of analytes. The key to this success is the prepared "slot-under-groove" nanoarchitecture arrays, which could realize a strongly coupled field enhancement with a large spatial mode distribution via the hybridization of gap-surface plasmons in the upper V-groove and localized surface plasmon resonance in the lower slot. Therefore, our slot-under-groove platform can simultaneously deliver high sensitivity for small-sized analytes and the identification of large-sized analytes with a large Raman gain.