Vector Bessel beams (VBBs), combining vector beams and non-diffracting Bessel beams, hold great potential in optical trapping, communication, and particle acceleration. However, existing studies are limited by fixed polarization evolution trajectories and insufficient multiplexing capability. Here, we propose all-dielectric spin-multiplexing metasurfaces for VBB generation. By superimposing two orthogonally polarized Bessel modes with different topological charges and axial wave vectors, longitudinal polarization evolution of VBBs is realized. The rotation direction of polarization evolution is easily reversed by swapping the numerical aperture (NA) configurations of two orthogonal components. Furthermore, we demonstrate simultaneous generation of four VBBs with independent polarization evolution without additional deflection phases. It confirms the high fidelity of the generated VBBs at wavelength of 1550 nm, whose polarization evolution conforms to the theoretical trajectory on the higher-order Poincaré sphere. This work enriches the degrees of freedom for structured light manipulation and provides a compact technical route for related optical devices.

Wavelength-selective routing based on valley-Hall photonic crystals (VPCs) has emerged as a promising approach for topology-assisted wavelength demultiplexers in silicon photonic chips. In current strategies, spectral control is typically achieved through in-plane geometric modulation; however, such tuning can introduce additional reciprocal-lattice Fourier components, enhance inter-valley scattering, and thereby degrade device performance. Here we show that the slab height of planar VPCs provides an effective out-of-plane tuning degree of freedom for spectral control while keeping the in-plane geometry unchanged. By modifying vertical confinement and the effective modal index, slab-height variation shifts the Dirac-point frequency and repositions the spectral window of interface-confined valley kink states. Adopting height-detuned inversion-related VPCs domains, we design a planar VPCs diplexer in a Y-shaped configuration, where the input spectral components are routed into two spatially separated output ports. Full-wave 3D finite-element simulations validate two well-separated passbands: the higher-frequency port operates over 223.7-228.4 THz (1313-1341 nm, 28 nm in 3-dB bandwidth) with transmission better than -2.83 dB and an inter-port isolation of 14.85 dB, and the lower-frequency port operates over 207.5-215.0 THz (1395-1446 nm, 51 nm in 3-dB bandwidth) with transmission better than -4.64 dB and an inter-port isolation of 24.03 dB. Parameter sweeps over the junction layout (including port separation and transition length) and output slab heights further quantify the trade-offs among 3-dB bandwidth, transmission efficiency, and inter-port isolation, and identify height ranges that maintain device functionality. These results establish slab-height-controlled band-structure tuning and interface-mode dispersion as a practical route toward robust and scalable on-chip topological multi-wavelength demultiplexers.

A dual-polarized (DP) patch antenna based on mode-composite feeding method with high isolation is presented. The dual polarization is achieved by employing the TE10 mode of the substrate integrated waveguide (SIW) and the quasi-TEM mode of the substrate integrated coaxial line (SICL) to independently excite a split-patch through a crossshaped slot. The inherent orthogonality between the TE10 and quasi-TEM modes ensures high isolation of the antenna. The simulated results show that the proposed antenna demonstrates DP radiation from 9.5 to 10.5 GHz, featuring a reflection coefficients better than −10 dB and isolation better than 45 dB.

Electrically driven short-wave infrared (SWIR) thermal emitters with dynamic tunability are highly desirable for advanced applications in spectroscopy, sensing, and communications, yet they remain challenging to realize. Here, we propose and numerically demonstrate a dynamically tunable thermal emitter based on an epsilon-nearzero (ENZ) material-integrated plasmonic metasurface. By incorporating an ultra-thin indium tin oxide (ITO) film into a metal-insulator-metal metastructure, we achieve significant modulation of absorption within the SWIR band. Under an applied bias of 3.5 V, the carrier density in the ITO layer is electrically tuned, shifting its permittivity to the ENZ regime and enabling a remarkable transition of the device from a highly reflective state to a broadband, strongly absorbing one. The structure also exhibits desirable features such as thermal stability, polarization insensitivity, and wide-angle emission stability. This work highlights the potential of ENZ-based active metasurfaces as integrated, spectrally selective, and electrically switchable thermal emitters, paving the way for intelligent infrared photonic systems.

Perfect fractional vortex beams extend the concept of perfect vortex beams by introducing non‐integer orbital angular momentum (OAM) and exhibit distinctive phase discontinuities, thereby offering additional degrees of freedom for optical communication and particle manipulation. This work demonstrates a spin‐multiplexing metasurface for generating perfect quasi‐fractional vortex beams (PqFVBs). By integrating the phase functions of an axicon, a spiral phase plate, and a Fourier lens into a compact metasurface design, The platform enables the selective generation of PqFVBs under orthogonal circular polarizations. The experimental measurements confirm that the beam radius can be flexibly customized via the phase parameters, specifically, the focal length and numerical aperture, while remaining decoupled from the OAM value. Furthermore, through introducing controllable phase dislocations, the number of donut‐shaped intensity lobes can be precisely engineered. Those structured optical vortices with customizable spatial distribution and topological features will open new avenues for optical communication and optical manipulation.

Mode-division multiplexing has emerged as a powerful strategy for enhancing the capacity of photonic integrated circuits, where compact and versatile mode manipulation devices in bus waveguides play a central role. In this work, we present the inverse design of two ultra-compact mode cyclic converters with size of only 7 µm in length, enabled by the integration of the finite-element method, Bernstein polynomial-based deformation parameterization, and the gradient-based method of moving asymptotes. The first device, a dual-mode cyclic converter (DMCC) with efficient TE0/TE1 mutual conversion, is obtained within just 20 optimization iterations. Three-dimensional finite-difference time-domain simulations on a silicon-on-insulator platform confirm high conversion efficiencies of -0.053 dB (TE0-to-TE1) and -0.043 dB (TE1-to-TE0), with mode purities reaching 99.3%. Extending this approach, a triple-mode cyclic converter (TMCC) for TE0/TE1/TE2 cyclic conversion is realized through a two-stage optimization strategy, converging at around 100 iterations. The TMCC exhibits conversion efficiencies of -0.67 dB (TE0-to-TE1), -1.1 dB (TE1-to-TE2), and -0.67 dB (TE2-to-TE0), accompanied by high mode purities of 96.4%, 93.6%, and 98.3%, respectively. Robustness analyses further demonstrate tolerance to fabrication deviations of ±10 nm. These results highlight the potential of inverse design in deformed multimode silicon waveguides for realizing efficient mode cyclic conversion, thereby advancing mode-division multiplexing in photonic integrated circuits.

A dual-band dual-circularly polarized transmitarray antenna (TA) operating in the 28/39 GHz millimeter-wave band is proposed in this article. The TA unit consists of two parts: a broadband linearly polarized (LP) receiving part and a dual-band dual-circularly polarized transmitting part. An over-2-bit phase compensation is achieved by changing the size of the U-shaped slot and the rotation status of the receiving part. A 24 × 24 TA model with an aperture size of 88.8 mm × 88.8 mm is built up by using the proposed units and fed by a wide-band corrugated horn antenna. The simulated results show that the maximum gain of the dual-band dual-circularly polarized TA is 26.28 dBic within the low-band (26.5–29.5 GHz) and 27.4 dBic within the high-band (37–40 GHz). To verify the accuracy of the simulation, a prototype of the proposed TA is fabricated and measured. The measured maximum efficiencies are 53.56% and 42.89% in low and high bands, respectively. The proposed TA covers two bands (28/39 GHz) for fifth generation (5G) millimeter-wave applications. Moreover, it features low cost, high gain, and high efficiency.

Tailoring vectorial optical fields (VOFs) with polarization singularity along the propagation path advances the development of fundamental physics and optical communications. This study demonstrates that spin-multiplexing metasurfaces can introduce a seamlessly varying propagation path related phase difference, enabling the generation of VOFs with longitudinally evolving polarization distributions. By superposing two orthogonal circularly polarized components, we achieve dynamic polarization evolution from radial to azimuthal polarization along the optical path. Experimental results confirm that the observed polarization distributions along the propagation path align with the evolution trajectory on the higher-order Poincare spheres. The design strategy offers substantial flexibility for crafting longitudinally varying VOFs with arbitrary polarization orders. Further, we show the generation of dual VOFs with distinct polarization evolution along the propagation axis. This approach opens new avenues for applications in light-matter interactions, complex structured light generation, and advanced polarization engineering.

Edge-enhanced imaging and polarization detection are critical for computer vision and biomedicine by enabling geometric feature extraction and object characterization. Conventional implementations, however, rely on bulky optics and complex systems, hindering miniaturization and integration. This work reports that a sub-micrometer-thick metasurface can simultaneously achieve bifocal bright-field/edge-enhanced imaging and polarization detection. The design incorporates a spiral phase to modulate the spectrum plane, while a lens phase performs an inverse Fourier transform on the spectrum plane to achieve edge-enhanced imaging. Meanwhile, through strategically arranging three polarization multiplexing units, full Stokes polarization parameters are captured in single-shot imaging. This sub-micrometer multifunctional metasurface eliminates complex optics and post-processing, paving the way for compact and integrated optical systems.

The emergence of vectorial optical fields (VOFs) featuring polarization singularities has introduced a new dimension to high-capacity optical communication. Cylindrical vector beams (CVBs) with VOFs play a pivotal role in enhancing multiplexing capabilities due to their transmission stability and resilience to turbulence. Straightforwardly and efficiently demultiplex CVBs with minimal crosstalk remain challenging for practical applications. This study proposes a single-layer dielectric metasurface for demultiplexing CVBs at telecommunications wavelengths. By leveraging polarization multiplexing and adjusting the rotation angle of customized metasurface units, effective spatial separation of CVB pairs is demonstrated. Furthermore, the methodology extends to demultiplexing multiple CVB pairs using interleaved unit cells set at distinct customized angles. The demultiplexing of 12-channel CVBs and their subsequent focusing into Gaussian spots were successfully demonstrated as a proof of concept. This work holds the significant potential for complex structured light manipulation and high-capacity optical communications.

Despite significant advancements in the power conversion efficiency (PCE) of perovskite/silicon tandem solar cells, improving carrier management in top cells remains challenging due to the defective dual interfaces of wide-bandgap perovskite, particularly on textured silicon surfaces. Herein, a series of halide ions (Cl−, Br−, I−) substituted piperazinium salts are designed and synthesized as post-treatment modifiers for perovskite surfaces. Notably, piperazinium chloride induces an asymmetric bidirectional ions distribution from the top to the bottom surface, with large piperazinium cations concentrating at the perovskite surface and small chloride anions migrating downward to accumulate at the buried interface. This results in effective dual-interface defect passivation and energy band modulation, enabling wide-bandgap (1.68 eV) perovskite solar cells to achieve a PCE of 22.3

A circularly polarized transmitarray antenna is proposed based on the unit cell composed of a magneto-electric dipole and a helical structure. The receiving unit and transmitting unit are electromagnetically coupled via planar pads, enabling a layer-by-layer fabrication process without bonding. An 18×21 unit prototype is developed, with spatial phase compensation achieved through rotation of the transmitting units. Simulation results show that the prototype exhibits a reflection coefficient below -20 dB and an axial ratio better than 1 dB over 16.5-24 GHz, with a peak gain of 27.1 dBic and a 1 dB gain bandwidth of 34.15%.

The ring structure radius of a perfect vortex beam (PVB) is invariant to topological charge, offering promising applications in optical communication, particle manipulation, and quantum optics. Integration of PVBs into on- chip optics remains challenging because complex and bulky optical devices are conventionally applied to generate PVBs. This paper reports that PVBs at telecommunication wavelengths can be generated through phase modulation in a single dielectric metasurface. The metasurface enables to generate PVBs with two distinct topological charges under orthogonal circular polarization illumination by employing a spin-multiplexing design strategy. Numerical simulations demonstrate that the radius of a PVB can be manipulated by modifying the structural parameters of the designed metasurface with high design flexibility. Further modulation of the polarization state of the incident light allows for the linear superposition of two PVBs with orthogonal circular polarization states to create a perfect Poincare beam (PPB), which is characterized by a vectorial optical field on a higher-order Poincare sphere. Our results introduce a straightforward method to develop versatile nanophotonic platforms for complex structured light generation and polarization engineering.

A dual-band circular polarization switchable planar array based on gap waveguide (GW) technology is presented. The array consists of a dual-circularly polarized (DCP) waveguide radiator that utilizes a septum polarizer, a metal plate with pins, and a 1 to 4 power divider. The polarization of the array can be switched between right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) by moving the radiator position relative to the other two parts. The simulated results show that the proposed array antenna works in dual bands of 19-21.2 GHz and 27.5-30 GHz, with return loss better than 12 dB, an axial ratio below 3 dB, and an antenna efficiency higher than 68%.

A 4 × 4 wideband millimeter-wave (mmWave) slot array antenna excited by the TE440 mode based on the groove gap waveguide is presented in this paper. A vertical waveguide located in the center of the cavity and two ridges are used to excite the TE440 mode. In addition, a pair of corrugations acting as the soft surface are added on the top of the array antenna to improve the gain. A 4 × 4 prototype is fabricated and measured. The measured and simulated results are in great agreement. The measured results show that the proposed array antenna achieved an impedance bandwidth (|S11| < −10 dB) of 26.7% from 26.14 to 34.2 GHz, and the maximum gain is 17.7 dBi. The proposed array antenna avoids the complicated feeding network, allowing us to reduce the manufacturing cost.

Two-dimensional Janus structures have been regarded as promising candidates for nanoscale optical devices due to the unique optical responses resulting from vertical atomic asymmetry within a monolayer. In this paper, we systematically investigate the second harmonic generation (SHG) in 54 Janus MXY (M = Cr, Hf, Mo, Nb, Ta, Ti, V, W, Zr, and X/Y = O, S, Se, Te, and X =/ Y) monolayers and calculate the second-order nonlinear susceptibilities of each material at six incident laser wavelengths of 405 nm, 532 nm, 800 nm, 1030 nm, 1064 nm and 1550 nm through first-principles calculations. The X-M-Y asymmetry results in non-zero components in the vertical direction, in contrast to non-Janus structures. Focusing on the SHG induced by incident light at wavelengths of 800 nm, 1064 nm, and 1550 nm, polarization-dependent responses of three Janus CrXY (X/Y = S, Se, Te, and X =/ Y) monolayers are demonstrated. S-polarization exhibits six-fold rotational symmetry, whereas p-polarization exhibits triple rotational symmetry. We expect these results to provide theoretical support and guidance for further screening and designing new nonlinear optical materials.

A novel dual-band dual-circularly polarized (CP) array antenna is presented, capable of achieving right-hand circular polarization (RHCP) in the K band and left-hand circular polarization (LHCP) in the Ka band, making it an excellent candidate for satellite communication and other diplexing communication systems. The antenna's radiating element features a double-C-shaped strip design fed through a metallic via. S-shaped slits are precisely etched onto the strips to ensure isolation between segments operating at different frequency bands. The whole array design incorporates a microstrip line feeding network, resulting in a compact and efficient structure. An 8 x 8 array based on the proposed radiating elements and feeding network was designed, fabricated, and measured. The measurement results indicate the impedance bandwidths (|S-11| < -10 dB) of 17-24.7 GHz (36.9%) and 28.5-33.4 GHz (15.8%), as well as the 3-dB axial ratio (AR) bandwidths of 18.5-24.0 GHz (25.9%) and 28.8-34.3 GHz (17.4%), over K and Ka bands, respectively. Therefore, the array achieves the impedance-AR combined bandwidths of 18.5-24 GHz (25.9%) in the K band and 28.8-33.4 GHz (14.8%) in the Ka band, with peak gains of 17.9 and 19.3 dBic, respectively. The relative sidelobe levels remain below-13 dB for both bands, with the antenna efficiency exceeding 62% and 40% within the combined bandwidths of K and Ka bands, respectively. The proposed dual-CP antenna successfully combines wideband performance across K and Ka bands with a low-profile and structurally simple design, offering a practical and cost-efficient solution.

Spin angular momentum (SAM) and orbital angular momentum (OAM) are particularly valued in high-capacity optical communications for their spatial orthogonality. However, the intricate spatial phase distribution optical field carrying OAM restricts its integration into miniaturized systems. Here, we demonstrate a single spin-multiplexing metasurface for spin-orbital angular momentum demultiplexing. This metasurface spatially differentiate the state of an OAM-carrying beam based on its spin state and the topological charge. Introducing an additional helical phase enables precise focusing of the OAM beam into a Gaussian spot, markedly enhancing coupling efficiency into single-mode fibers. A 24-channel spin-orbital angular momentum demultiplexing system is demonstrated using the proposed method. Furthermore, a staggered design can achieve orbital angular momentum demultiplexing of the same channel in a smaller footprint. The proposed method offers a straightforward and effective approach for spin-orbital angular momentum demultiplexing, holding substantial potential for advancing high-capacity optical communication applications.

The optically deficient and intrinsically unstable hole transport layer (HTL) is the Achilles' heel of n-i-p perovskite/silicon tandems. Here, a minimalist transparent hole-selective contact is developed without additional HTL by simply integrating cross-linkable p-type small molecules into antisolvent. This strategy not only improves the perovskite crystallinity, shields the perovskite from external stressors, and suppresses interfacial mass exchange, but also provides efficient defect passivation and favorable band alignment via the formation of graded heterojunction. Consequently, the corresponding 1.65 eV perovskite solar cell achieves a stabilized efficiency of 19.6%, alongside significantly improved thermal, ultraviolet, and operation stabilities. Furthermore, leveraging its outstanding transparency, a bifacial single-junction device is showcased achieving a record bifaciality of 101.4%, and a monolithic perovskite/silicon tandem boasting a certified efficiency of 29.2% for 1.04 cm2, which represents the highest certified efficiency achieved for n-i-p perovskite/silicon tandems. The demonstration of efficient and stable minimalist hole-selective contacts encourages the tandem community to reevaluate the n-i-p structure, with the goal of harnessing the high open-circuit voltage of single-junction n-i-p PSCs.

This letter presents the hybrid integrated suspended line (HISL) platform with multiple inner boards. By employing cutting-out dielectric and multiple-inner board technology, low loss and modal phase velocity balance can be achieved simultaneously. The utilization of HISL platforms helps enhance the mechanical strength of the entire structure. The loss and the modal phase velocity of the structure and the influence of various physical dimensions on the odd-and even-mode impedance are analyzed. Based on the proposed HISL platform with multiple inner boards, a low-loss ultrawideband 2-18-GHz 3-dB coupler utilizing nonuniform technology is designed. The proposed coupler exhibits low measured insertion loss, achieving better than 0.3 dB at the center frequency. Additionally, both measured isolation and return loss are better than 15 dB.