Kai Zhang

Radiative loss to the surrounding continuum fundamentally limits the quality factor (Q) of the resonant modes in open systems. This constrains the light–matter coupling strength, emission coherence, and efficiency of nonlinear interactions, all of which critically depend on high-Q confinement. Bound states in the continuum (BICs) offer an elegant solution to this challenge by delivering high-Q resonances and strong field localization, even when the resonant frequency lies within the radiation continuum. In this Review, we trace the physics of BICs from their formation mechanisms to platform-dependent implementations and device-level functionalities, highlighting what they enable across different frequency regimes. We identify two broad categories, symmetry-protected and accidental BICs, each realized across metasurfaces, gratings, photonic crystal slabs, integrated waveguides, and hybrid resonant structures. Platform-dependent radiation channels and coupling conditions, in turn, determine three core physical effects, which are enhanced light–matter interaction, topological field modulation, and strong wave confinement. These effects drive applications across the entire electromagnetic spectrum from ultraviolet to radio frequencies. By establishing radiation coupling suppression as a unifying paradigm, BICs have unlocked performance regimes, broad cross platform, and research directions that extend far beyond conventional resonance-engineering applications.

Charge and energy transfer are fundamental processes in van der Waals heterostructures (vdWHs), and controlling the transfer pathway is crucial for applications spanning from photodetection to photoluminescence. However, deterministic modulation of energy transfer (ET) and charge transfer (CT) is limited by static band alignments and physical barrier thicknesses. Here, we integrate an optical microcavity with two-dimensional (2D) heterostructures, leveraging the cavity resonance as a switch to convert the dominant mechanism from energy transfer to charge transfer, an unexpected transition that is tunable via laser parameters and cavity geometry. We reveal that the cavity-modified local electromagnetic environment thermodynamically stabilizes the CT pathways via dipole-selective coupling. Furthermore, cavity-mediated exciton–photon hybridization generates intermediate states that reconstruct the non-equilibrium relaxation landscape, while the cavity-enhanced local field induces photon-assisted tunneling to overcome intrinsic barrier limitations. Our work provides unprecedented flexibility for manipulating carrier dynamics in tunable optoelectronics, opening new avenues for ultrafast photodetectors, low-power photovoltaics, tunable switches, and various interdisciplinary applications.

Over the past two decades, nanoscience and nanotechnology have profoundly transformed modern society─powering next-generation electronics, revolutionizing healthcare diagnostics, and enabling sustainable energy solutions that reshape how we live and work. Established in 2006 as a joint initiative between the Chinese Academy of Sciences and local governments, the Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO) has dedicated itself to application-oriented basic research and the industrialization of nanotechnology. Equipped with world-class scientific infrastructure, including the Nano-X vacuum interconnected nanotech workstation, nanofabrication facility, platform for characterizations of nanomaterials and nanodevices, and NanoBioChem Center, SINANO has spearheaded regional innovation through cutting-edge research in nano optoelectronic materials and devices, nano biomedicine, and functional nanomaterials. As SINANO marks its 20th anniversary, it will continue to uphold its mission of “devoting to nanotechnology innovation and leading the way for emerging industries”, fostering impactful international cooperation, cultivating young talents, and accelerating the transformation of scientific and technological strengths into industrial competitiveness to make greater contributions to the worldwide nanotechnology landscape.

Infrared luminescent semiconductor materials and devices are fundamental to optoelectronic information technology. van der Waals (vdW) semiconductors, notably black phosphorus (BP) and tellurium (Te), possess a narrow direct bandgap and a low surface/Auger recombination rate, making them promising for infrared luminescence and light-emitting devices. The excitonic behavior and widely tunable band structure of such materials offer versatile pathways for modulating light emission, while the weak interlayer vdW interactions facilitate exceptional heterointegration capabilities. This review begins by addressing the challenges and recent progress in the epitaxial growth of BP and Te thin films. Furthermore, we discuss excitonic near-infrared emission in few-layer BP, mid-infrared emitters derived from thicker BP, and Te-based mid-infrared luminescent devices, along with their potential for spectral and polarization tuning. Finally, key challenges and prospects in this evolving field are summarized.

Conventional vision systems for autonomous driving are hindered by energy‐inefficient and latency‐prone architectures due to physically segregated sensing, memory, and processing modules. Here, we report a bio‐inspired vision sensor that emulates the spectral adaptation mechanism of the Pacific salmon retina leveraging a van der Waals heterojunction of NbNiTe ₅ and black phosphorus (BP). Operating at zero bias, the device exhibits intrinsic wavelength‐dependent antagonistic photoresponses: negative photoconductance under 365 nm ultraviolet illumination (mimicking visual suppression in bright environments) and positive photoconductance under 820 nm near‐infrared light (emulating visual enhancement in dim conditions). This built‐in adaptability enables robust environmental perception across extreme illumination scenarios, from high‐glare daylight to low‐light nights. Furthermore, we integrated this sensor into a full functional system that unifies image perception, non‐volatile storage, and in‐sensor processing. When deployed for traffic scenario analysis, a convolutional neural network trained on features extracted by the sensor achieved 96% classification accuracy, with performance scaling proportionally to the system's noise suppression capability. Our work establishes a practical strategy for high‐contrast bidirectional photonic synapses and highlights the potential of biomimetic systems in neuromorphic vision — particularly for autonomous driving and intelligent surveillance, where reliable operation across diverse spectral environments is critical.

Owing to their dangling‐bond‐free surfaces and strong excitonic effects, monolayer transition‐metal dichalcogenides (TMDs) hold promise for ultra‐low‐threshold heterogeneously integrated nanolasers. However, despite extensive demonstrations of TMD‐based nanolasers, further reduction of the lasing threshold is hindered by the challenge of simultaneously achieving an ultra‐small mode volume and an ultra‐high quality (Q) factor in conventional optical cavities. Moreover, the dielectric interfaces of these cavities induce strong dielectric screening and defect‐assisted nonradiative exciton recombination, both of which severely suppress exciton emission in monolayer TMDs. Here, we overcome these fundamental limitations by employing the air modes in a twisted lattice nanocavity. By twisting two finite‐sized hexagonal photonic crystal structures in a single layer of SiN _x thin film, we introduce a radial, quasi‐continuous gradient in the air‐filling fraction, thereby forming a radially graded bandgap. This graded bandgap acts as concentric mirrors that tightly confine Bloch modes at the K ‐point, yielding air modes with extreme field confinement in the air and ultra‐high Q factors. By integrating a monolayer WS ₂ with the twisted lattice SiN _x nanocavity, we experimentally achieve a record‐low lasing threshold of 0.03 W/cm ² at room temperature. Our work establishes a versatile platform for advanced two‐dimensional (2D) semiconductor light sources.

High-signal-to-noise ratio and highly integrated terahertz detectors constitute the cornerstone of next-generation wireless communication systems, yet their practical realization remains a persistent challenge. While the hot-carrier-assisted photothermoelectric effect enables zero-bias, broadband terahertz detection, semi-metallic candidates suffer from intrinsic high dark currents and low detectivity, impeding their practical deployment into communication systems. Here, we overcome this challenge by engineering hot-carrier transport in a dual-gated black phosphorus detector, enabling high-signal-to-noise ratio sub-terahertz detection. When the detector is in a p-n or n-p configuration, the detection signal-to-noise ratio can be optimized to 45 dB. Furthermore, an excellent zero-bias sensitivity of 1.44 pW/Hz^1/2 and a response time of 650 ns at 0.1 THz are achieved. This dual-optimization enables robust and high-fidelity signal reception. Our work has established a viable strategy for the realization of chip-scale integrated receivers in terahertz communication systems.

In modern quantum technologies, quantum emitters (QEs) have emerged as core components of quantum communication networks and on-chip quantum information processing, representing a pivotal link in future quantum systems. Due to atomic-scale thickness, the absence of dangling bonds at interfaces, and surface-localized photonic states that facilitate efficient light–matter interactions, two-dimensional (2D) materials are considered ideal platforms for high-performance, wavelength-tunable, and on-chip integrable solid-state QEs. While QEs have been demonstrated in various 2D materials, several challenges and unresolved issues remain. This review systematically summarizes the latest advances in the research of QEs based on 2D materials, aiming to provide comprehensive introductory guidance for beginners or interested readers. We first outline the fundamentals of single-photon emission, including basic principles, performance metrics, and experimental characterization methods. A comprehensive survey of cutting-edge studies on QEs based on hexagonal boron nitride, transition metal dichalcogenides, and twisted moiré heterostructures is presented, highlighting emission mechanisms and structure–luminescence correlations. Furthermore, we summarize strategies for creating and localizing QEs through external field engineering in 2D systems, tuning emission wavelengths, and enhancing emission performance, including wavelength tuning and emission enhancement techniques. Finally, current challenges are analyzed, and perspectives for advancing scientific exploration in this field are proposed. Leveraging their unique physical properties and integration potential, these 2D QEs hold great promise for quantum information technologies, communication systems, and various interdisciplinary fields.

Polarization-sensitive neuromorphic vision sensing excels in distinguishing light polarization states, offering intrinsic advantages in reducing glare and enhancing visual clarity in complex lighting environments, enabling advanced applications in autonomous driving, optical communication, and bioinspired imaging across the visible-to-infrared spectrum. Here, we present a polarization-sensitive neuromorphic phototransistor based on a high-quality, intrinsically anisotropic two-dimensional black arsenic-phosphorus nanosheet, which exhibits exceptional optoelectronic performance with a peak responsivity of 2.88 A W ^-1 , a polarization ratio of 4.7 and a dynamic range of 40 dB within the near-infrared communication band. Through multidimensional input control, including polarization and gate voltage, the phototransistor successfully simulates synaptic behaviors analogous to human neural responses to visual stimuli, with paired-pulse facilitation values reaching 201%. Critically, the device demonstrates gate-tunable short-term plasticity, with optical persistence triggering stable long-term plasticity states that underpin memory consolidation. The neuromorphic properties enable the development of a hybrid optical-electronic neural network which achieves a classification accuracy of over 90% on the Fashion-MNIST dataset and a reconstruction accuracy of 71.38% using data from the Yale Face Database under 0º linear polarization. We demonstrate a polarization-resolved imaging approach utilizing the black arsenic-phosphorus phototransistor to reconstruct hidden targets with high fidelity through Stokes parameter extraction and degree of linear polarization mapping, revealing intricate polarization features invisible to conventional imaging systems. Our work establishes a foundational platform for high-performance neuromorphic vision systems with integrated polarization imaging, computation, and communication functionalities, addressing critical challenges in scalable brain-inspired optoelectronic technologies.