A power splitter with a wideband arbitrary splitting ratio, which provides flexibility and adaptability in forming photonic devices such as microring resonators and Mach–Zehnder interferometers, proves to be essential in photonic integrated circuits (PICs). We designed and fabricated a directional coupler-based power splitter with a wideband arbitrary splitting ratio and a microring resonator with a wideband uniform extinction ratio (ER) based on artificial gauge field (AGF) optimization. The neural network-aided inverse design method is applied to complete the target. Less than 0.9 dB power splitting variation and 1.6 dB ER variation have been achieved experimentally over a 100-nm bandwidth. Wideband performance, design efficiency, and device compactness are obtained by utilizing this optimization, which indicates great potential and universality in PIC applications.

Microcirculation imaging is crucial in understanding the function and health of various tissues and organs. However, conventional imaging methods suffer from fluorescence label dependency, lack of depth resolution, and quantification inaccuracy. Here, we report a light-sheet dynamic light-scattering imaging (LSH-DSI) system to overcome these shortcomings. LSH-DSI utilizes selected plane illumination for an optical sectioning, while a time-frequency analysis method retrieves blood flow velocity estimates from dynamic changes in the detected light intensity. We have performed imaging experiments with zebrafish embryos to obtain angiographs from the trunk and head regions. The results show that LSH-DSI can capture label-free tomographic images of microvasculature and three-dimensional quantitative maps of local blood flow velocities.

Confronting the escalating global challenge of counterfeit products, developing advanced anticounterfeiting materials and structures with physical unclonable functions (PUFs) has become imperative. All-optical PUFs, distinguished by their high output complexity and expansive response space, offer a promising alternative to conventional electronic counterparts. For practical authentications, the expansion of optical PUF keys usually involves intricate spatial or spectral shaping of excitation light using bulky external apparatus, which largely hinders the applications of optical PUFs. Here, we report a plasmonic PUF system based on heterogeneous nanostructures. The template-assisted shadow deposition technique was employed to adjust the morphological diversity of densely packed metal nanoparticles in individual PUFs. Transmission images were processed via a hash algorithm, and the generated PUF keys with a scalable capacity from 2875 to 243401 exhibit excellent uniqueness, randomness, and reproducibility. Furthermore, the wavelength and the polarization state of the excitation light are harnessed as two distinct expanding strategies, offering the potential for multiscenario applications via a single PUF. Overall, our reported plasmonic PUFs operated with the multidimensional expanding strategy are envisaged to serve as easy-to-integrate, easy-to-use systems and promise efficacy across a broad spectrum of applications, from anticounterfeiting to data encryption and authentication.

In recent years, many phase space distributions have been proposed, and one of the more independently interesting is the Bai distribution function (BDF). The BDF has been shown to interpolate between the instantaneous auto-correlation function and the Wigner distribution function, and be applied in linear frequency modulated signal parameter estimation and optical partial coherence areas. Currently, the BDF is only defined for continuous signals. However, for both simulation and experimental purposes, the signals must be discrete. This necessitates the development of a BDF analysis workflow for discrete signals. In this work, we analyze the sampling requirements imposed by the BDF and demonstrate their correctness by comparing the continuous BDFs of continuous test signals with their numerically approximated counterparts. Our results permit more accurate simulations using BDFs, which will be useful in applying them to problems such as partial coherence.

Optical phased arrays (OPAs) are crucial in beam-steering applications, particularly as transmitters in light detection and ranging and free-space communication systems. In this paper, we demonstrate a on-chip OPA that emits multiple orbital angular momentum (OAM) beams in different directions, each carrying unique topological charges. By superimposing a forked 1 × 3 Dammann grating on the grating array, six OAM beams with topological charges of ±3, ±4, and ±5 can be radiated from the OPA region. The OPA chip was fabricated on a silicon-on-insulator platform, and the simultaneous generation of multiple OAM beams was realized experimentally. The directions of these vortices can be steered by adjusting the wavelength of the input light and the bias voltages of the phase shifters, enabling a remarkable field of view (FOV) of 140 deg × 40 deg within a 120-nm wavelength range. We pave the way for developing systems with ultrawide FOVs, improving the resolution of remote sensing and broadening the possibilities of free-space communications.

Plasmonic colors are attracting attention for their subwavelength small size, vibrant hues, and environmental sustainability beyond traditional pigments while suffering from angular and/or polarization dependency due to distinct excitations of lattice resonances and/or surface plasmon polaritons (SPPs). Here, we demonstrate the sodium metasurface-based plasmonic color palettes with polarization-independent wide-view angle (approximately >±60 deg in experiment and up to ±90 deg in theory) and single-particle-level pixel size (down to ∼60 nm) that integrate both pigment-like and structure coloring advantages, fabricated by the templated nanorod-pixelated solidification of wetted liquid metals. Such intriguing performances are mainly attributed to the particle plasmon dominant spectral response by steering the filling profile and thus the interplay between localized surface plasmons and SPPs. Combining low material cost, potentially scalable manufacturing process, and pronounced optical performance, the proposed sodium-based metasurfaces will provide a promising route for advanced color information technology.

In a few-mode erbium-doped fiber (FM-EDF), which is a key section in a space-division multiplexing (SDM) communication system, linearly polarized (LP) and orbital angular momentum (OAM) modes, as two-mode bases with different phase profiles, can be transformed into each other. In principle, the LP and OAM modes have a different mode spatial intensity distribution and a gain difference for FM-EDF amplifiers. How to analyze and characterize the differential mode-bases gain (DMBG) is important, but still an issue. We build, for the first time to our knowledge, a local analysis model composed of discrete elements of the FM-EDF cross section in areas of mode spatial intensity distribution azimuthal variation. Using the model of the two mode bases, analysis of local particle number distribution and detailed description of the local gain difference are realized, and the overall gain difference between the two mode bases is obtained. By building an amplifier system based on mode phase profile controlling, the gain of two mode bases is characterized experimentally. The measured DMBG is ∼0.8 dB in the second-order mode, which is consistent with the simulation result. This result provides a potential way to reduce the mode gain difference in the FM-EDF, which is important in improving the performance of the SDM communication system.

Mid-infrared (MIR)-polarized thermal emission has broad applications in areas such as molecular sensing, information encryption, target detection, and optical communication. However, it is difficult for objects in nature to produce polarized thermal emission. Moreover, simultaneously generating and modulating broadband MIR thermal emission with both circular and linear polarization is even more difficult. We present a chiral plasmonic metasurface emitter (CPME) composed of asymmetric L-shaped and I-shaped antennas. The CPME consists of In3SbTe2 (IST) phase-change material (PCM) antennas, an Al2O3 dielectric layer, and an Au substrate. It is demonstrated that the CPME can selectively emit polarized light with different polarization states. Numerical simulations show that the CPME can achieve full Stokes parameter control of MIR thermal emission. By changing the state of the PCM IST, the spectral emissivity of 0 deg, 45 deg, 90 deg, and 135 deg linearly polarized (LP) lights and left-handed/right-handed circularly polarized (LCP/RCP) lights can be adjusted. In the crystalline state, the CPME exhibits the total degree of polarization (DoP) greater than 0.5 in the wavelength range of 3.4 to 5.3 μm, the degree of linear polarization (DoLP) greater than 0.4 in the range of 3.0 to 5.1 μm, and the degree of circular polarization (DoCP) greater than 0.4 in the range of 4.5 to 5.6 μm. The physical mechanism of polarized emission has been investigated fully based on the near-field intensity distribution and power loss distribution. Finally, the potential applications of the designed CPME in infrared polarization detection and antidetection are verified through numerical calculations.

Depolarizing behavior is commonly observed in most natural samples. For this reason, optical tools measuring the differences in depolarization response among spatially separated structures are highly useful in a wide range of imaging applications for enhanced visualization of structures, target identification, etc. One commonly used tool for depolarizing discrimination is the so-called depolarizing spaces. In this article, we exploit the combined use of two depolarizing spaces, the indices of polarization purity (IPP) and polarizance–reflection–transformation (PRT) spaces, to improve the capability of optical systems to identify polarization–anisotropy depolarizers. The potential of these spaces to discriminate among different depolarizers is first studied from a series of simulations by incoherently adding diattenuations or retarders, with some control parameters emulating samples in nature. The simulated results demonstrate that the proposed methods are capable of increasing differences among depolarizers beyond other well-known techniques. Experimentally, validation is provided by conducting diverse phantom experiments of easy interpretation and mimicking the stated simulations. As a useful application of our approach, we developed a model able to retrieve intrinsic microscopic information of samples from macroscopic polarimetric measurements. The proposed methods enable non-invasive, straightforward, macroscopic characterization of depolarizing samples, and may be of interest for enhanced visualization of samples in multiple imaging scenarios.

Diffractive optical neural networks (DONNs) have exhibited the advantages of parallelization, high speed, and low consumption. However, the existing DONNs based on free-space diffractive optical elements are bulky and unsteady. In this study, we propose a planar-waveguide integrated diffractive neural network chip architecture. The three diffractive layers are engraved on the same side of a quartz wafer. The three-layer chip is designed with 32-mm3 processing space and enables a computing speed of 3.1 × 109 Tera operations per second. The results show that the proposed chip achieves 73.4% experimental accuracy for the Modified National Institute of Standards and Technology database while showing the system’s robustness in a cycle test. The consistency of experiments is 88.6%, and the arithmetic mean standard deviation of the results is ~4.7%. The proposed chip architecture can potentially revolutionize high-resolution optical processing tasks with high robustness.

Quantum photonic processors are emerging as promising platforms to prove preliminary evidence of quantum computational advantage toward the realization of universal quantum computers. In the context of nonuniversal noisy intermediate quantum devices, photonic-based sampling machines solving the Gaussian boson sampling (GBS) problem currently play a central role in the experimental demonstration of quantum computational advantage. A relevant issue is the validation of the sampling process in the presence of experimental noise, such as photon losses, which could undermine the hardness of simulating the experiment. We test the capability of a validation protocol that exploits the connection between GBS and graph perfect match counting to perform such an assessment in a noisy scenario. In particular, we use as a test bench the recently developed machine Borealis, a large-scale sampling machine that has been made available online for external users, and address its operation in the presence of noise. The employed approach to validation is also shown to provide connections with the open question on the effective advantage of using noisy GBS devices for graph similarity and isomorphism problems and thus provides an effective method for certification of quantum hardware.

Soliton molecules (SMs), bounded and self-assembled of particle-like dissipative solitons, exist with versatile mutual interactions and manifest substantial potential in soliton communication and optical data storage. However, controllable manipulation of the bounded molecular patterns remains challenging, as reaching a specific operation regime in lasers generally involves adjusting multiple control parameters in connection with a wide range of accessible pulse dynamics. An evolutionary algorithm is implemented for intelligent control of SMs in a 2 μm ultrafast fiber laser mode locked through nonlinear polarization rotation. Depending on the specifications of the merit function used for the optimization procedure, various SM operations are obtained, including spectra shape programming and controllable deterministic switching of doublet and triplet SMs operating in stationary or pulsation states with reconfigurable temporal separations, frequency locking of pulsation SMs, doublet and SM complexes with controllable pulsation ratio, etc. Digital encoding is further demonstrated in this platform by employing the self-assembled characteristics of SMs. Our work opens up an avenue for active SM control beyond conventional telecom bands and brings useful insights into nonlinear science and applications.

High-resolution seeing through complex scattering media such as turbid water, biological tissues, and mist is a significant challenge because the strong scattering scrambles the light paths and forms the scattering wall. We propose an active polarized iterative optimization approach for high-resolution imaging through complex scattering media. By acquiring a series of sub-polarized images, we can capture the diverse pattern-illuminated images with various high-frequency component information caused by the Brownian motion of complex scattering materials, which are processed using the common-mode rejection of polarization characteristics to extract target information from scattering medium information. Following that, our computational reconstruction technique employs an iterative optimization algorithm that commences with pattern-illuminated Fourier ptychography for reconstructing the high-resolution scene. It is extremely important that our approach for high-resolution imaging through complex scattering media is not limited by priori information and optical memory effect. The proposed approach is suitable for not only dynamic but also static scattering media, which may find applications in the biomedicine field, such as skin abnormalities, non-invasive blood flow, and superficial tumors.

Research on supercontinuum sources on silicon has made significant progress in the past few decades. However, conventional approaches to broaden the spectral bandwidth often rely on complex and critical dispersion engineering by optimizing the core thickness or introducing the cladding with special materials and structures. We propose and demonstrate supercontinuum generation using long-period-grating (LPG) waveguides on silicon with a C-band pump. The LPG waveguide is introduced for quasi-phase matching, and the generated supercontinuum spectrum is improved greatly with grating-induced dispersive waves. In addition, the demonstrated LPG waveguide shows a low propagation loss comparable with regular silicon photonic waveguides without gratings. In experiments, when using a 1550-nm 75-fs pulse pump with a pulse energy of 200 pJ, the supercontinuum spectrum generated with the present LPG waveguide shows an ultrabroad extent from 1150 to 2300 nm, which is much wider by 200 nm than that achieved by dispersion-engineered uniform silicon photonic waveguides on the same chip. This provides a promising option for on-chip broadband light source for silicon photonic systems.

The unique phase profile and polarization distribution of the vector vortex beam (VVB) have been a subject of increasing interest in classical and quantum optics. The development of higher-order Poincaré sphere (HOPS) and hybrid-order Poincaré sphere (HyOPS) has provided a systematic description of VVB. However, the generation of arbitrary VVBs on a HOPS and a HyOPS via a metasurface lacks a unified design framework, despite numerous reported approaches. We present a unified design framework incorporating all design parameters (e.g., focal lengths and orders) of arbitrary HOPS and HyOPS beams into a single equation. In proof-of-concept experiments, we experimentally demonstrated four metasurfaces to generate arbitrary beams on the fifth-order HOPS (nonfocused and tightly focused, NA 0.89), 0-2 order, and 0-1 order HyOPS. We showed HOPS beams’ propagation and focusing properties, the superresolution focusing characteristics of the first-order cylindrical VVBs, and the different focusing properties of integer-order and fractional-order cylindrical VVBs. The simplicity and feasibility of the proposed design framework make it a potential catalyst for arbitrary VVBs using metasurfaces in applications of optical imaging, communication, and optical trapping.