Jin Chen

Orbital-angular-momentum (OAM) beams provide high-dimensional channels for metasurface holography, but their ideal orthogonality is strongly degraded in finite, discretized metasurfaces. In filter-free OAM multiplexing, multiple holographic channels therefore compete for limited structural modulation degrees of freedom, leading to severe crosstalk and reduced reconstruction fidelity. Here, we propose polarization-assisted vortex holography, in which an orthogonally polarized component is introduced as an auxiliary coherent degree of freedom rather than an independent decoding channel. By jointly exploiting the OAM-dependent helical phase and the polarization-dependent Jones response of the metasurface, the method redistributes the encoding burden among vectorial field components and relaxes the OAM-only modulation constraint. Full-wave simulations show that the proposed strategy consistently improves image correlation and channel distinguishability compared with conventional OAM-only multiplexing under identical filter-free conditions. We further demonstrate its compatibility with output-polarization and propagation-distance multiplexing, enabling 10 filter-free holographic channels. This work establishes polarization assistance as a compact vectorial mechanism for high-fidelity OAM metasurface holography.

Optical physical unclonable functions (PUFs) provide hardware‐level identifiers based on stochastic material disorder, but many reported optical PUFs rely on fixed readout states or require structural reconfiguration to update their responses. Here, we present a lithography‐free, voltage‐addressable optical PUF platform based on multiply stacked exfoliated MoS ₂ microstructures. The device combines a static bright‐field grayscale readout with two gate‐dependent photoluminescence (PL) observables, namely PL intensity and PL peak wavelength. The stochastic MoS ₂ stacking process produces spatially heterogeneous optical responses, while electrostatic gating enables reversible voltage‐dependent PL readout across 41 measured gate‐voltage states without permanently rewriting the material structure. Correlation and mutual‐information analysis show that the grayscale, PL‐intensity, and PL‐wavelength responses are complementary and partially decorrelated readout channels derived from the same disordered flake network. The generated binary responses exhibit near‐ideal inter‐Hamming‐distance statistics, low empirical bit bias, and low authentication‐error probability, with the aged responses after 10 months still maintaining TAEP below 2 × 10 ⁻³⁶ for PL intensity and 2 × 10 ⁻²² for PL wavelength. These results demonstrate a compact optical PUF architecture that integrates structural disorder and voltage‐addressable PL modulation for multidimensional authentication.

Extreme suppression of free-space radiation in open planar photonic systems remains a long-standing goal in nanophotonics. Conventional bound states in the continuum (BICs), constrained by symmetry-protected or accidental singularities, restrict experimental Q - k scaling exponents to n = 2-8 because ordinary bands lack sufficient degrees of freedom to host, redistribute or merge additional radiation-suppressing singularities. Here we demonstrate a degeneracy-driven topological-reconfiguration mechanism: an E ₂ -type high-order degeneracy at Γ acts as a multi-charge reservoir, enabling controlled release, inversion and merging of topological charges under symmetry breaking. This unlocks a Q ∝ k ⁻¹⁰ radiation-suppression regime in a single-layer all-dielectric metasurface. Experimentally, we realize ultrahigh free-space Q-factors with 3% geometric robustness and a maximum Q of 1.1 × 10 ⁶ . A 100-pixel array exploiting these resonances demonstrates picometre-scale spectral discrimination by resolving ultranarrow H ¹³ C ¹⁴ N absorption lines. These results establish high-order-degeneracy-enabled BIC physics for robust ultrahigh-Q photonics and precision free-space spectroscopy.

Room-temperature infrared photodetection has long been constrained by broadband thermal radiation, which injects background photons and drives detectors toward a background-limited regime. Beyond stochastic photon fluctuations, this radiation produces a deterministic mean photocurrent offset that can overwhelm weak signals under ambient conditions. This limitation originates from unipolar spectral integration, where background photons across the response band contribute with the same photocurrent polarity. Here we demonstrate an in-sensor background-offset cancellation mechanism enabled by spectral polarity inversion. By engineering wavelength-dependent photocurrent reversal, photons from different spectral bands generate opposite-signed responses within a single device, suppressing the mean background-induced current under fixed blackbody illumination without external subtraction or balanced readout. We realize this concept using an optically reconfigurable mixed-dimensional Ge/black phosphorus van der Waals heterostructure photodetector. The zero-bias device achieves a room-temperature detectivity of 7.89 × 10¹⁰ Jones, within a factor of 4.11 of the background-limited benchmark for unity-quantum-efficiency integration-type detectors.

Accurate spectral analysis in compact platforms is essential for portable sensing, integrated photonics, and on‐chip materials characterization. Single‐detector computational spectrometers offer an appealing route toward extreme miniaturization, but their performance is fundamentally constrained by the intrinsic structure of bias‐dependent responsivity curves: these responses evolve smoothly and non‐orthogonally with wavelength, producing highly correlated photocurrent patterns that collapse the effective rank of the responsivity matrix. Such low‐rank encoding leads to ill‐conditioned inverse problems, making the reconstruction of multi‐peak or densely spaced spectra particularly fragile to noise and device imperfections. Here, we overcome this long‐standing limitation by introducing gate‐tunable band‐profile modulation in an in‐plane dual‐bottom‐gate black phosphorus photodetector. Independent gate control forms a reconfigurable local potential barrier that generates strongly wavelength‐dependent photocurrent maps, substantially enhancing spectral discriminability and improving the effective rank and numerical conditioning of the responsivity matrix. Leveraging this encoding mechanism, a single detector enables high‐accuracy single‐peak identification over a 500‐nm near‐infrared band and reliable one‐to‐eight‐peak reconstruction within a calibrated window. We further demonstrate robust graphene layer‐number identification, including regimes where Raman spectroscopy becomes ambiguous. This work establishes band‐profile engineering as a general device‐level strategy for advancing single‐detector computational spectrometers and enabling compact, high‐fidelity spectral sensing.

Conventional multispectral photodetectors typically rely on multiple electrical terminals to discriminate different wavelengths, which inevitably increases structural complexity. Here, we break this paradigm by demonstrating a dual-color visible–infrared photodetector based on a simple two-terminal Au/MoS₂/Te heterostructure. The device operates through a bias-switching mechanism: reversing the voltage polarity selectively activates either the MoS₂/Au Schottky junction for visible-light detection (520 nm) or the Te/MoS₂ heterojunction for infrared detection (1550 nm). This bias-controlled wavelength selectivity is unambiguously verified by scanning photocurrent mapping. Beyond dual-color discrimination, an adaptive convolutional neural network is employed to decode the nonlinear current–voltage characteristics and enable precise spectral identification, achieving a reconstruction error of approximately 4.5%. Furthermore, high-fidelity dual-color imaging is demonstrated at room temperature. These results establish a hardware–algorithm co-design strategy based on a minimalist two-terminal architecture, providing a viable route toward compact and intelligent spectral-sensing systems.

Flat photonic bands enable enhanced light–matter interaction but are often accompanied by increased radiative loss or strong angular sensitivity, limiting their practical utility. We report a photonic crystal (PhC) slab combining extreme band flatness with normal-incidence high-Q resonances through two physically cooperative mechanisms. Through effective mass engineering near the Γ point, we realize an ultra-flat dispersion with a relative variation as low as Δλ/λ ≈ 2.4 × 10 ^-4 , creating a momentum-robust optical mode. Independently, accidental bound states in the continuum (BICs) are manipulated to merge at the zone center, yielding Q-factors exceeding 10 ⁸ . The distinct behaviors of these degenerate modes enable a self-referenced sensing scheme with intrinsic stability against thermal perturbations. This work establishes a unified approach to decoupling dispersion flattening and radiation suppression in planar photonics.

Spatial Fourier processing is commonly implemented using 4f optical architectures, in which spatial filtering and imaging are carried out on physically distinct Fourier and image planes. Our work proposes a metasurface-based imaging system. By introducing a quadratic phase factor at the object plane to pre-modulate the optical field, and integrating a metasurface with a filtering function and a focusing phase profile at the spectral plane, the system simultaneously executes frequency-domain filtering and spatial-domain imaging. This enables four-channel (x, y, 45°, and 135°) polarization-resolved edge imaging in a single exposure. Finally, by capturing images from four polarization channels and employing the Stokes vector method for polarization-state retrieval, the system reconstructs the original polarization information. This synchronous tuning scheme for spatial-domain and Fourier-domain information offers a novel, to the best of our knowledge, solution for compact optical processors and on-chip polarization imaging.

Simultaneous and continuous control over polarization and wavelength—two orthogonal and information-rich degrees of freedom—remains a central challenge in metasurface photonics, long hindered by intrinsic dispersion constraints and structural degeneracy. Here, we customize continuous polarization–wavelength mapping through a nonlocal metasurface platform that decouples birefringent evolution from structural dispersion. We achieve programmable, spectrally resolved polarization shaping across the broadband mid-infrared regime by introducing an equivalent nonlocal Jones matrix formalism and a dimension-interlaced vectorial diffraction neural network. This framework enables fully continuous and arbitrarily prescribed mapping across the joint polarization–wavelength space—beyond the capabilities of segmented or interleaved metasurface designs. We experimentally demonstrate non-degenerate multicolor vectorial holography, broadband achromatic imaging, and arbitrary elliptical polarization multiplexing with high fidelity and minimal crosstalk, maintaining strong channel isolation. Our results establish a scalable route toward continuous-domain photonic encoding, offering a powerful foundation for ultracompact optical communication, vectorial information encryption, and high-dimensional light-field processing.

Benefiting from the extraordinary ability of manipulating lightwaves at the subwavelength scale, metasurfaces are expected to achieve multifunctional and multichannel integration to increase information capacities. However, their practical application has been limited by fixed electromagnetic responses post‐fabrication. To overcome this constraint, we propose a dynamically tunable metasurface that leverages the insulator‐to‐metal phase transition of vanadium dioxide (VO ₂ ), which synergistically combines the geometric (Pancharatnam‐Berry) phase and the propagation phase to overcome the limitations of static or single‐channel devices. This architecture integrates four independent wavefront‐manipulation channels on a single platform, enabling switching between functionalities for linearly polarized (LP) and circularly polarized (CP) incitations via thermal actuation. When VO ₂ in its insulating state, the metasurface operates as a spin‐decoupling device under CP incidence, enabling independent wavefront engineering for left‐handed circularly polarized (LCP) and right‐handed circularly polarized (RCP) waves. Upon transition to the metallic state, it serves as a polarization multiplexer for orthogonal LP waves. By integrating four distinct operational modes on a single dynamically reconfigurable platform and employing simple thermal switching—rather than complex control mechanisms—this work demonstrates a significant advance in functional integration and practical feasibility for applications in terahertz communication, holography, and sensing.