Xue Feng

As an essential module of optical systems, a varifocal lens usually consists of multiple mechanically moving lenses along the optical axis. The recent development of metasurfaces with tunable functionalities holds the promise of miniaturizing varifocal lenses. However, existing varifocal metalenses are hard to combine electrical tunability with a scalable number and range of focal lengths, which limits the practical applications. Our previous work shows that the electrically tunable channels could be increased to 2 ^N by cascading N polarization‐dependent metasurfaces with liquid crystals (LCs). Here, we demonstrate a compact eight‐channel electrically tunable varifocal metalens with three single‐layer polarization‐multiplexed bi‐focal metalens and three LC cells. The total thickness of the device is ∼6 mm, while the focal lengths can be switched among eight values within the range of 3.6–9.6 mm (3.6, 4.2, 4.5, 4.9, 6.2, 6.9, 8.4, 9.6 mm). The scheme is scalable in both the number and range of focal lengths, as well as has the advantage of further miniaturization. We believe that our proposal would open new possibilities for miniaturized imaging systems, AR/VR displays, LiDAR, etc.

Photonics is promising to handle extensive vector multiplications in artificial intelligence (AI) techniques due to natural bosonic parallelism and high-speed information transmission. However, the dimensionality of current photonic linear operation is limited and tough to improve due to the complex beam interaction for implementing optical matrix operation and digital-analog conversions. Here, we propose a programmable and reconfigurable photonic linear vector machine with extreme scalability formed by a series of emitter-detector pairs as the independent basic computing units. The elemental values of two high-dimensional vectors are prepared on emitter-detector pairs by bit encoding and analog detecting method without requiring large-scale analog-to-digital converter or digital-to-analog converter arrays. Since there is no interaction among light beams inside, extreme scalability could be achieved by simply multiplicating the independent emitter-detector pair. The proposed architecture is inspired by the traditional Chinese Suanpan or abacus, and thus is denoted as photonic SUANPAN. Experimentally, the computing fidelities for vector inner products could achieve >98% in our implementation with an 8 × 8 vertical cavity surface emission laser (VCSEL) array and an 8 × 8 MoTe ₂ two-dimensional material photodetector array. Furthermore, such implementation is applied on two typical AI tasks as 1024-dimensional optimization problem is successfully solved and competitive classification accuracy of 88% is achieved for handwritten digit dataset. We believe that the photonic SUANPAN could serve as a fundamental linear vector machine and enhance various future AI applications.

Scalability remains a major challenge in building practical fault-tolerant quantum computers. Currently, the largest number of qubits achieved across leading quantum platforms ranges from hundreds to thousands. In atom arrays, scalability is primarily constrained by the capacity to generate large numbers of optical tweezers, and conventional techniques using acousto-optic deflectors or spatial light modulators struggle to produce arrays much beyond ∼10,000 tweezers. Moreover, these methods require additional microscope objectives to focus the light into micrometer-sized spots, which further complicates system integration and scalability. Here, we demonstrate the experimental generation of an optical tweezer array containing 280 × 280 spots using a metasurface, nearly an order of magnitude more than most existing systems. The metasurface leverages a large number of subwavelength phase-control pixels to engineer the wavefront of the incident light, enabling both large-scale tweezer generation and direct focusing into micron-scale spots without the need for a microscope. This result shifts the scalability bottleneck for atom arrays from the tweezer generation hardware to the available laser power. Furthermore, the array shows excellent intensity uniformity exceeding 90%, making it suitable for homogeneous single-atom loading and paving the way for trapping arrays of more than 10,000 atoms in the near future.

Electro-optic (EO) modulators with ultra-high speed and low driving voltage are essential for high-performance optical computing, optical communication, and broadband microwave photonic links. In this work, we have proposed an electrode optimization method for periodic structures, based on the RGLC transmission line model and exemplified by sawtooth traveling-wave electrodes (STWEs). We have established analytical expressions for characteristic parameters including the resistance, inductance, capacitance, as well as the slot depth and width of STWEs for the first time, achieving synchronous optimization of microwave loss minimization and velocity matching. Validated through simulations on thin-film lithium niobate modulators, the approach achieves an ultra-high EO bandwidth of up to 290 GHz and a low voltage-length product of 2.5 V·cm. The optimized STWEs feature a minimum linewidth of 5 μm and a metal thickness as thin as 500 nm, which are compatible with deep ultraviolet lithography and suitable for large-scale, low-cost fabrication. This work would pave the way for developing scalable ultra-high-speed EO modulator arrays.

Cherenkov radiation has attracted much attention for promoting the free electron radiation sources. Using hyperbolic metamaterial, Cherenkov radiation can be excited using low-energy electrons and thus on-chip free electron radiation source has been realized. However, direct experimental observations of on-chip free-electron-based Cherenkov radiation have been limited to the visible region, and the tunability has not been thoroughly explored. In this work, by constructing a hyperbolic metamaterial with graphene and hexagonal boron nitride, on-chip, free-electron-based terahertz Cherenkov radiation is observed and the frequency tunable range spans 3.2 to 14 THz in a hundred-micron-scale dimension. Compared with other free-electron terahertz sources, the chip size is over three orders of magnitude smaller, and the tunable range is one of the widest. This work extends the on-chip free-electron-based Cherenkov radiation into terahertz domain, highlighting its tunability and paves the way for further advancements in free electron radiation source.

In regular magneto‐optical trap (MOT) systems, the delivery of six circularly polarized (CP) cooling beams requires complex and bulky optical arrangements including waveplates, mirrors, retroreflectors, etc. To address such technique challenges, a beam delivery system for miniaturized MOT is proposed entirely based on meta‐devices. The key component is a novel polarization decoupling multi‐port beam‐splitting (PD‐MPBS) metasurface that relies on both propagation phase and geometric phase. The fabricated samples exhibit high beam‐splitting power uniformity (within 4.4%) and polarization purities (91.3–93.2%). By leveraging such a beam‐splitting device as well as a reflective beam‐expanding meta‐device, an integrated six‐beam delivery system for miniaturized MOT application is implemented. The experimental results indicate that six expanded beams have been successfully delivered with uniform power (within 9.5%), the desired CP configuration, and a large overlapping volume (76.2 mm ³ ). It is believed that a miniaturized MOT with the proposed beam delivery system is very promising for portable application of cold atom technology in precision measurement, atomic clock, quantum simulation, and computing, etc.

Quantum teleportation is a crucial function in quantum networks. The implementation of photonic quantum teleportation could be highly simplified by quantum photonic circuits. To extend chip-to-chip teleportation distance, more effort is needed on both chip design and system implementation. In this work, we demonstrate a time-bin-based chip-to-chip photonic quantum teleportation over optical fibers under the scenario of a star-topology quantum network. Three quantum photonic circuits are designed and fabricated on a single chip, each serving specific functions: heralded single-photon generation at the user node, entangled photon pair generation and BSM at the relay node, and projective measurement of the teleported photons at the central node. The unbalanced Mach–Zehnder interferometers (UMZI) for time-bin encoding in these quantum photonic circuits are optimized to reduce insertion losses and suppress noise photons generated on the chip. Besides, an active feedback system is employed to suppress the impact of fiber length fluctuation between the circuits, achieving a stable quantum interference for the BSM in the relay node. As a result, a photonic quantum teleportation over optical fibers of 12.3 km is achieved based on these quantum photonic circuits, showing the potential of chip integration for the development of quantum networks.