Orbital angular momentum (OAM) modes have emerged as a promising solution for enhancing the capacity of optical multiplexing systems, leveraging their theoretically unbounded set of orthogonal spatial modes. However, the generation and detection of OAM multiplexing signals are predominantly reliant on bulky optical components within complex optical setups. We introduce a compact solution for OAM information processing using laser-written glass chips, facilitating efficient multiplexing and demultiplexing of multiple OAM information channels. During the multiplexing process, OAM channels are managed via laser-scribed single-mode waveguides within a glass chip, with their modes converted using laser-written holograms on the side wall of the glass chip. The reciprocal process is employed for OAM demultiplexing. Our chips seamlessly interface with commercial optical fibers, ensuring compatibility with existing fiber-optic communication infrastructure. This work not only establishes, to our knowledge, a novel approach for OAM optical multiplexing but also underscores the potential of laser writing technology in advancing photonics and its practical applications in optical communications.

Single-pixel imaging (SPI) through complex media remains challenging. In this paper, we report high-resolution common-path SPI with dual polarization using random-frequency-encoded time sequences in complex environments where the illumination and detection paths are severely distorted. By leveraging a common-path optical configuration with orthogonal polarization states, a series of dynamic scaling factors can be corrected. The designed random-frequency encoding scheme disperses scattering-induced noise into artifacts to be simply removed. It is demonstrated in optical experiments that the proposed method is feasible and effective to reconstruct high-resolution object images in complex environments. The proposed method does not require complex optical components and prior knowledge about scattering media, providing a robust solution for high-resolution optical imaging in complex scenarios where the illumination and detection paths are severely distorted at the same time.

To address the current issues of low reconfigurability, low integration, and high dynamic power consumption in programmable units, this study proposes a novel programmable photonic unit cell, termed MZI-cascaded-ring unit (MCR). The unit functions analogously to an MZI, enabling broadband routing when operating within the free spectral range (FSR) of the embedded resonator, and it transitions into a wavelength-selective mode, leveraging the micro-ring’s resonance to achieve precise amplitude and phase control for narrowband signals while outside the FSR, featuring dual operational regimes. With the implementation of spiral waveguide structures, the design achieves higher integration density and lower dynamic power consumption. Based on the hexagonal mesh extension of such a unit, the programmable photonic processor successfully demonstrates a reconfiguration of large amounts of fundamental functions with tunable performance metrics, including broadband linear operations like optical router and wavelength-selective functionalities like wavelength division multiplexing. This work establishes a new paradigm for programmable photonic integrated circuit design.

By introducing photonic crystals with Dirac point based on valley edge states, we design heterostructure waveguides on the silicon-on-insulator platform, promising waveguides with different widths to operate in the single-mode state. Benefiting from the unidirectional transmission and backscattering-immunity characteristics enabled by the topological property, there is no scattering loss induced by the mode-mismatch at the transition junction between the waveguides with different widths. Therefore, the valley-locked heterostructure waveguide possesses unique width degrees of freedom. We demonstrate it by designing and fabricating waveguides with expanding, shrinking, and Z-type configurations. Thanks to the free transition between waveguides with different widths, an interesting energy convergency is observed, which is represented from the imaging of the enhanced third-harmonic generation of the silicon slab. Consequently, these heterostructure waveguides can be more flexibly integrated with existing on-chip devices and have the potential for high-capacity energy transmission, energy concentration, and field enhancement.

Multiplexing techniques have always been one of the important components of optical communication research. These techniques can transmit multiple signals in a shared information channel and can greatly increase the maximum capacity of an information channel. The Dirac-vortex cavity is a type of photonic crystal surface emission system, and its characteristics of miniaturization and high stability make it very suitable for on-chip optical system. In this paper, we realized dual-channel emission of the Dirac-vortex cavity, which is achieved by modulating the size and phase of hexagonal holes in the hexagon lattice. The characteristics of dual-channel emission are investigated by numerical simulation, and the dual-channel emission rules are summarized. The double Dirac-vortex cavity model is not only explored for its multiplexing capability but also as an alternative scheme for the application of Dirac-vortex cavity in multiplex communication systems.

We present a novel, to our knowledge, optical arbitrary waveform generation (OAWG) technique, termed four-wave optical-waveguided chirp-free ultrafast shaping (FOCUS), which utilizes four-wave mixing (FWM)-based spectral transcription. FOCUS enables the generation of chirp-free pulse sequences with independently adjustable duration, intensity, interval, and central wavelength of sub-pulses. Experimental validation demonstrates that the system achieves a 2 ps temporal resolution and a 400 ps record length while maintaining <1 nm spectral bandwidth, >30 dB extinction ratio, ∼1 nJ pulse energy consumption, and 3.5 nm continuous wavelength tunability. Fundamental analysis reveals that three key parameters govern temporal resolution: spectral shaper resolution (the current limiting factor), pump bandwidth (potentially expandable to 30 nm), and engineered group delay dispersion (GDD). Recent advancements in chip-scale mode-locked lasers, dispersion-engineered waveguides, and nonlinear FWM modules position the FOCUS platform as a promising candidate for next-generation ultrafast photonic systems designed for simultaneous sub-picosecond temporal resolution and nanosecond-scale waveform programmability within compact integrated architectures.

For the first time, to our knowledge, we demonstrate a six-mode transmission over a 960-km fiber link using in-line integrated amplification provided by a six-mode erbium-doped fiber amplifier (6M-EDFA) for a 28-GBaud dual-polarization QPSK signal. This transmission distance is five times longer than that of previously reported works. The integrated 6M-EDFA enabling this long-haul transmission exhibits modal gains of >17.6 dB, while the gains increase to 25 dB with an input power of -25 dBm. Importantly, a Gaussian-like erbium doping profile has been proposed to optimize the differential modal gain to 1.15 dB, ensuring a more uniform signal-to-noise ratio between spatial modes after long-haul transmission.

A conformal metasurface (MS) is required to load on a curved surface and both electromagnetic and mechanical performances need to be considered in practice. In this study, a bandpass circular-protrusion-jigsaw-shaped metasurface (CPJS-MS) is presented to meet the requirement of high mechanical character. In addition, a square-protrusion-jigsaw-shaped MS (SPJS-MS) is proposed, inspired by a mortise and tenon joint of ancient wooden architecture. First, the electromagnetic performance of a planar JS-MS is obtained using the equivalent circuit model (ECM) and simulation. Also, the polarization-independent angular stability for the two JS-MSs is compared with the conventional square-grid MS (SG-MS) to analyze the effect of protrusion structure on the pass band. Second, the transmission characteristics of the conformal JS-MS and SG-MS with different curvature radii are studied based on ECM. Then, the conformal stability of the three MSs is compared with infinite planar form under various incident angles and polarization states to further understand the conformal effect. Most importantly, mechanical properties, which are rarely reported, are discussed and compared. Finally, three MS samples are fabricated and measured to demonstrate the effectiveness and accuracy of the proposed MS designs. The analysis method is beneficial to further understanding electromagnetic and mechanical properties of conformal MSs.

The flexibility and active control of terahertz multi-focal focusing is essential for advancing next-generation terahertz communication systems. Here, we present and experimentally demonstrate a voltage-controlled liquid crystal (LC) integrated terahertz multi-focal metalens capable of dynamically reconfiguring focal configurations. Both simulation and experimental results confirm electrically modulated spatial-spin separation and multi-focal focusing within the 0.44–0.55 THz frequency band, exhibiting single-to-quadruple switching for left-handed circularly polarized (LCP) waves and dual-to-single transitions for right-handed circularly polarized (RCP) waves. The LC cascaded metalens achieves a measured full-width-at-half-maximum (FWHM) of <2.35 mm and a peak focusing efficiency of 70.4%. The normalized total output power of single, two, and four focal points exceeds 85.1%, 54.9%, and 59.3%. The combination of spatial-spin separation and reconfigurable focus modes is expected to significantly increase the capacity and energy efficiency of future terahertz communication systems.

The state of polarization (SOP) on high-order Poincaré spheres (HOPSs), characterized by their distinctive phase profiles and polarization distributions, plays a crucial role in both classical and quantum optical applications. However, most existing metasurface-based implementations face inherent limitations: passive designs are restricted to represent a few predefined HOPS SOPs, while programmable versions typically constrain to 1-bit or 2-bit phase control resolution. In this paper, dynamic generation of HOPS beams with arbitrary SOP based on a transmissive space-time-coding metasurface is demonstrated. By combining 1-bit phase discretizations via PIN diodes with a time-coding strategy, the metasurface enables quasi-continuous complex-amplitude modulation for harmonic waves in both x- and y-polarizations. Based on near-field diffraction theory, arbitrary SOPs on any HOPSm,n can be precisely generated using a linearly polarized basis, which is independently controlled by FPGA reconfiguration. We experimentally demonstrate that polarization holography on HOPS0,0 achieves high polarization purity >91.28%, and vector vortex beams on HOPS1,3 and HOPS-1,3 exhibit high orbital angular momentum mode purities >91.25%. This methodology holds great potential for structured wavefront shaping, vortex generation, and high-capacity planar photonics.

Absorbing particles have attracted wide interest in multifarious fields due to their strong light absorption characteristics, which can be trapped by optical bottles (OBs), three-dimensional dark regions surrounded by light. Existing OB-based particle manipulation is typically limited to a single functionality, such as the stationary volume or the single manipulated object. This severely limits the versatility and selectivity of micro-manipulation, particularly in the multi-particle system. In this paper, we address these challenges by introducing a dynamic OBs generation method. By modulating optical vortices and multi-parabolic trajectory phases, a series of OBs with targeted positions, numbers, and states is encoded as a battery of holograms, which are imported into the spatial light modulator (SLM). Experimentally, by dynamically reconfiguring the corresponding holograms in the SLM, we validate selectively switching and moving OBs for dynamic particle manipulation. Consequently, a specific fraction of targeted particles can be selectively released, transported 7.2 mm away while the others remain trapped in place, or merged from two 3.5-mm-spaced OBs into a larger single entity. Our results deepen the applications of OB beams and may herald a new avenue for dynamic particle manipulation.

Due to the outstanding anti-interference capability against the ambient noise, LiDARs based on frequency-modulated continuous wave (FMCW) technology with high sensitivity and high signal-to-noise ratio (SNR) are essential to achieve ideal photodetection of weak light. To significantly improve the weak light detection performance of balanced photodetectors, this work first demonstrates a novel near-infrared germanium-on-silicon (Ge/Si) avalanche photodetector with a three-electrode balanced scheme. The single three-electrode avalanche photodetector exhibits a high responsivity of >200 A/W near breakdown voltage. The three-electrode balanced avalanche photodetector (3ele-BAPD) achieves a common-mode rejection ratio (CMRR) of 50 dB at an operating wavelength of 1550 nm. We have set up the FMCW coherent detection system. The minimum detectable power of -93 dBm can be achieved, corresponding to an SNR of 3.2 dB and a detection probability of 54%. In comparison, the performance exceeds that of the two-electrode balanced avalanche photodetector (2ele-BAPD), which exhibits a minimum detectable power of -85 dBm with a corresponding SNR of 3.1 dB and a detection probability of 51%. The superior weak light detection performance enables the 3ele-BAPD to accomplish 3D imaging based on the FMCW LiDAR scheme. Moreover, the 3ele-BAPD is also applied to velocity measurement for 4D sensing. The applications of LiDAR velocity measurement and imaging are verified.

Optical interconnects based on photonic integrated circuits (PICs) are emerging as a pivotal technology to address the relentless surge in data traffic driven by compute-intensive applications. Combining mode-division multiplexing (MDM) with wavelength-division multiplexing (WDM) offers a compelling approach to significantly enhance the shoreline density of optical interconnects. However, existing on-chip MDM systems encounter considerable challenges in simultaneously achieving a large optical bandwidth, multi-band operation, and ultra-compactness, thereby limiting scalability as conventional telecom band resources become increasingly constrained. Here we introduce, to our knowledge, the first inverse-designed multi-band mode multiplexer (MUX) utilizing a digital metamaterial structure to support the first three-order TE modes. The proposed device features an ultra-compact footprint of 6 μm×4.8 μm and exhibits an exceptionally flat spectral response, with numerical simulations confirming spectral variations of less than 0.94 dB across the 1500–2100 nm range. Experimental results further validate its performance, demonstrating insertion losses below 4.3 dB and 4.0 dB, and crosstalk below -11.6 dB and -11.3 dB, within the 1525–1585 nm and 1940–2040 nm bands, respectively. Additionally, system-level optical interconnect experiments using a multi-band MDM circuit successfully achieve single-wavelength transmission rates of 3-modes×180 Gb/s at the 1.55 μm band and record-setting 3-modes×114 Gb/s in the 2 μm band. This work highlights the transformative potential of employing multi-band MDM technology to enhance bandwidth density and scalability, providing a robust foundation for next-generation high-capacity on-chip optical interconnects.

Vector vortex beams (VVBs) have garnered significant attention in fields such as photonics, quantum information processing, and optical manipulation due to their unique optical properties. However, traditional metasurface fabrication methods are often complex and costly, limiting their practical application. This study successfully fabricated an all-dielectric aluminum oxide metasurface capable of achieving longitudinal variation using 3D printing technology. Experimental results demonstrate that this metasurface generates longitudinally varying VVBs at 0.1 THz, with detailed characterization of its longitudinal intensity distribution and vector polarization states. The high consistency between experimental and simulation results validates the effectiveness of 3D printing in metasurface fabrication. The proposed metasurface offers promising applications in optical polarization control and communication, providing, to our knowledge, new insights and technical support for related research.