Lili Gui

Vortex beams (VBs) carrying orbital angular momentum (OAM) exhibit a range of intriguing optical properties owing to their unique phase profile and hold great promise for applications across diverse fields from optical communications to precision measurement. Vortex fiber lasers (VFLs), serving as a pivotal class of vortex light sources, allow direct generation of high-purity and highly stable VBs within the laser cavity. However, previous VFLs have typically focused on manipulating only unidirectional light fields, largely overlooking the propagation-direction degree of freedom naturally supported by bidirectional laser resonators. Here, we demonstrate Janus vortex meta-lasers (JVMLs), which enable simultaneous asymmetric control and full 2 π phase modulation of intracavity counter-propagating light fields, owing to the asymmetric–symmetric hybrid configuration of the intracavity Janus metasurface (IJMS). As a proof of concept, we constructed JVMLs capable of simultaneously emitting a pair of counter-propagating VBs featuring high mode purity and large topological charge (TC) differences (e.g., |Δ ℓ |=3, 10, and 32, determined by the IJMS design). To our knowledge, this work presents the first experimental realization of asymmetric bidirectional VB generation within a fiber laser cavity, opening an avenue for expanding the dimensionality of laser mode control by exploiting the intracavity propagation-direction degree of freedom. The proposed IJMS configuration further provides a generalized framework for high-quality structured light generation and intracavity multidimensional optical engineering.

All‐polarization‐maintaining fiber (all‐PMF) lasers can greatly improve the operational stability and integration of multi‐pulse sources, serving as highly promising alternatives to conventional multi‐cavity sources. In this work, we propose a simple intracavity modulation strategy to regulate dual‐wavelength pulse states by adjusting the rotational splicing angle of polarization‐maintaining single‐mode fibers (PM‐SMFs). This method enables precise modulation of intracavity polarization coupling and spectral response of the equivalent Lyot filter. With this scheme, we realize the continuous and controllable transition from asynchronous dual‐comb pulses to synchronous bound solitons in an all‐PMF fiber laser mode‐locked by a carbon nanotube saturable absorber. When the splicing angle is fixed at 45°, the laser outputs stable asynchronous dual‐comb pulses with a repetition frequency difference of 1.35 kHz. Furthermore, the dynamic evolution of synchronized bound solitons with phase differences from π to π /2 is also observed at a splicing angle of 30°. This work provides a feasible solution for flexible manipulation of dual‐wavelength pulse nonlinear dynamics, and lays a foundation for the development of compact, high‐stability multifunctional ultrafast fiber lasers and dual‐comb sources.

Surface lattice resonance (SLR) is a key mechanism for achieving high-Q resonances in plasmonic nanostructures. However, the oblique incidence or refractive-index matching required during excitation makes it challenging in practical applications. As a solution, we demonstrate SLR metasurfaces under normal incidence and in an asymmetric environment, with a Q-factor of 47 and a resonant transmission peak of 0.43 in the 1-μm band in experiments, by skillfully exciting the high-order multipole modes and out-of-plane resonance of ordinary gold nanorods. The influence of structural parameters on SLR characteristics is explored, providing insight into the effective regulation of the transmission response and achieving the transition from a transmission dip to a transmission peak. Benefiting from the strong light-matter interaction of the SLR systems, we experimentally demonstrate linear refractive index sensing with a bulk sensitivity of 1014 nm/RIU, along with an 80-times relative enhancement (compared with an unpatterned Au film of the same thickness) in second harmonic generation and an appreciable third-order saturable absorption response. Our work provides a simple and efficient strategy to tailor narrow-band plasmonic SLR metasurfaces, enabling promising potential in sensing, nonlinear optics, pulse optics, and other fields.

The growing demands for compact and asymmetric optical components in various systems have drawn significant attention to Janus metasurfaces (JMSs), which are known for their unique transmission properties that enable directional and asymmetric optical responses. However, metasurfaces that simultaneously multiplex the degrees of freedom of both the incident and outgoing directions to achieve a one-way mirror effect remain challenging to realize. In this work, we present Janus full-space metasurfaces (JFSMSs) that exhibit one-way-mirror optical behavior, whereby transmission or reflection is selected based solely on the direction of the incident wavevector relative to the metasurface. As proof of concept, a series of JFSMSs were numerically designed for holographic displays, optical encryption, vortex beam emitters, and bidirectional optical combiners. The proposed JFSMS strategy offers a promising route for advancing multifunctional and spatially multiplexed metasurfaces in the optical regime and extending related application scopes.

Wavelength-multiplexed metasurfaces enable precise, independent light control at multiple wavelengths within a single platform, demonstrating significant potential for compact applications in imaging, optical communications, and information processing. Exceptional points (EPs) in non-Hermitian systems have garnered considerable interest in optics and physics owing to their unique phase characteristics in parameter space. Prior approaches to wavelength-multiplexing metasurface design employ neural networks, polarization manipulation, or spatial division. In contrast, this work leverages the wavelength dependence of EPs to implement wavelength multiplexing with narrow channel spacing under a single polarization state. By adopting distinct paths in parameter space, we achieve customized wavelength-dependent phase manipulations. As a practical demonstration, we independently manipulate two wavelengths to generate orbital angular momentum (OAM) beams with distinct topological charges (with a wavelength spacing of 38 nm), and customized holographic patterns at shorter wavelength spacing (18 nm).

We demonstrate a Janus vortex meta-laser, which enables simultaneous asymmetric and full 2π phase modulation of two counter-propagating beams, owing to the asymmetric–symmetric hybrid configuration of the intracavity Janus metasurface.

We demonstrate an intracavity multidimensional metasurface assisted vortex fiber laser that emits pulsed LG0,20 beam with high purity in both radial ( p = 0, 88.5%) and azimuthal ( l = 20, 92.1%) modes.

Vortex fiber lasers that directly deliver low-cost and high-performance vortex beams could provide straightforward and compact solutions for structured laser sources and have found applications in various fields. Suffering from either simple and fixed functionality, or large insertion loss together with bulky configurations of phase modulation components such as q -plates and spatial light modulators, the output flexibility and tunability of conventional vortex fiber lasers are limited. Recently, polarization-multiplexing metasurfaces (PMMs) have shown powerful potential for manipulating light in different dimensions. Here we propose and experimentally demonstrate topological charge switchable vortex fiber lasers assisted by on-demand customized PMMs. Importantly, by adjusting the setting of the wave plates within the cavity, the topological charge of the output vortex beams can be effectively switched and even decoupled at will. The design principle and experimental verification offer new perspectives for vortex fiber laser configurations, offering promising applications from large-capacity optical communication and particle manipulation to super-resolution microscopy and quantum information processing.

SignificanceThe effects of optogenetic stimulation (OS) on in vitro neural network behavior were studied through a reservoir computing-based obstacle avoidance task, revealing its impact on the task-processing capabilities of the network. Furthermore, it is demonstrated that a minimal output of signals from 15 neurons in the network is sufficient to achieve stable task control, with a success rate exceeding 95%. The optogenetically enhanced biological reservoir computing frame could find applications in neuro-robotic control and brain-inspired intelligence.AimWe aim to utilize optogenetically controlled in vitro neural networks and the first-order reduced and controlled error (FORCE) learning algorithm to achieve obstacle avoidance in neuro-robotic systems.ApproachWe presented an all-optical biological reservoir computing framework that leverages optogenetics and calcium imaging to precisely regulate and record neuronal activities. A closed-loop system was developed incorporating the FORCE learning algorithm, which guided a virtual car through obstacle avoidance tasks.ResultsThe system demonstrated high accuracy and efficiency in navigating obstacles, achieving optimal performance after ∼150 s of training. OS significantly improved the obstacle avoidance success rate, enhancing the system’s adaptability and accuracy.ConclusionsThe results highlight the potential of optogenetically controlled biological neural networks in neuro-robotic systems, showcasing their capability to achieve accurate and efficient obstacle avoidance through physical reservoir computing.

Dynamic metasurfaces (MSs) have emerged as a transformative technology in miniaturized tunable optics, enabling reconfigurable optical responses and opening new avenues for compact, adaptive, and multifunctional optical design. Here, a microelectromechanical system (MEMS)‐tunable bilayer MS (MEMS‐BMS) is demonstrated for dynamic vortex wave plates (VWPs), achieved by integrating a thin‐film piezoelectric MEMS mirror with bilayer plasmonic nanostructures composed of differently sized anisotropic nanobricks oriented in various directions. By electrically actuating the MEMS mirror to precisely tune the MEMS‐BMS separation, independent 2D phase control at two distinct separation distances is enabled, allowing dynamic switching of the reflected beam between different vortex modes under circularly polarized light excitation. The switching between vortex beams with topological charges of l = 2 and l = −1 is achieved with high polarization conversion efficiency (>80%) and a fast response time (9 microseconds), while preserving the output circular polarization state. The developed MEMS‐BMS VWP with its high efficiency, fast response, and polarization preservation holds strong potential for advanced applications, including high‐resolution imaging, dynamic holography, optical tweezers, optical machining, and beyond.