Metasurfaces serve as a pivotal platform integrating orbital angular momentum (OAM) encoded holography and nanoprinting technology, boasting broad application prospects. Nevertheless, nanoprinting techniques struggle to achieve in-depth integration with multi-channel OAM modulation, failing to meet the demands of integrated and broadband applications. This paper proposes a broadband, multi-channel, single-layer all-dielectric metasurface architecture. By utilizing customized polarization-sensitive nanopillar structures, two transmission channels and independent decoding of distinct OAM holographic patterns are realized under the illumination of circularly polarized vortex beams. The proposed scheme enables multi-channel multiplexing of OAM holographic images and nanoprinted images across a broad visible spectrum, and is further applied to multi-level information encryption. Herein, polarization states and OAM modes function as secret keys, and information decryption is completed through joint decoding. This study breaks through the application restrictions of single-function metasurfaces and provides an innovative solution for the design of broadband, multi-channel integrated photonic devices.

In this paper, an optical fiber vector magnetic field and temperature dual-parameter sensor based on multimode intermodal interference (MMI) is proposed and experimentally demonstrated. The sensor head is prepared by using magnetic fluid (MF) encapsulated single-mode fiber (SMF) -six-hole single-core fiber (SHSCF) -noncore fiber (NCF) -SMF structure. Wherein offset splicing between the lead-in SMF and the SHSCF is adopted to obtain a noncircular symmetry structure and effectively excite higher-order modes. In addition, employing a segment of NCF to be sandwiched between the SHSCF and the lead-out SMF is further to generate richer higher-order modes. Experimental results indicate that the transmission spectrum intensity of the sensor is highly sensitive to the magnetic field, while the wavelength shift of the transmission spectrum is extremely sensitive to temperature. Therefore, wavelength shift can be used to monitor temperature, and intensity can be used to measure the magnetic field. In our experiments, magnetic field intensity sensitivity, direction sensitivity and temperature sensitivity of the proposed fiber sensor were 1.34 dB/mT, 0.23 dB/degrees, and 2.31 nm/degrees C, respectively. The proposed optical fiber sensor has a compact structure, is easy to fabricate, and exhibits high sensitivity. It provides a novel sensing solution for the simultaneous measurement of magnetic field and temperature by combining the MF's optical absorption and refractive index tunability through intensity and wavelength demodulation methods.

Integrating orbital angular momentum (OAM) holography and nanoprinting holds great potential for high-capacity optical multiplexing. However, realizing this integration on a single metasurface faces bottlenecks, including severe mode coupling and OAM crosstalk. Moreover, physical-layer encoding may provide limited information protection when used alone. To address these challenges, we propose an optical information system that integrates metasurface-based physical encoding with neural network steganography. On the hardware front, we engineer a multifunctional metasurface that synergizes Malus’s law, optimized phase modulation, and mode separation algorithms to achieve low-crosstalk, multi-channel nearfield nanoprinting and farfield OAM holography. On the software front, we introduce a U-Net steganography network as a post-processing layer. By combining metasurface-based physical modulation with neural network processing, we establish a dual-layer information-protection architecture. This approach provides a potential framework for secure optical storage and communication, with potential applications in anti-counterfeiting and privacy protection.

Abstract Conventional optical lenses achieve focusing and zooming through curved surfaces and stacked structures, which inherently suffer from large volume, complex configuration, and low integration. These drawbacks make them difficult to adapt to miniaturized and high-precision optical systems. Metalenses have emerged as ideal alternatives due to their planar configuration and exceptional wavefront manipulation capabilities. However, achieving high-quality simultaneous multi-physics manipulation and multispectral independent response within a single all-dielectric device remains a widely researched focus and technical difficulty in the field. Accordingly, this paper proposes a multispectral varifocal metalens based on spin–orbit angular momentum multidimensional multiplexing. Using the geometric phase modulation mechanism, we successfully construct a variety of metalens platforms that enable the cooperative control of multiple parameters including spin angular momentum, orbital angular momentum, and wavelength, and realize their selective addressing and focusing at arbitrary positions in three-dimensional space. By precisely regulating the polarization state, topological charge, and operating wavelength of the incident vortex beam, we achieve six-step focal length switching within the range of 20–80 μ m along the optical axis, high-quality bifocal output, and distributed focusing of multiple foci in 3D space. This work exploits multidimensional physical properties to realize selective addressing and focusing of incident vortex beams, with high polarization conversion efficiency maintained over a broad visible band. It opens new avenues for transformative applications in high-resolution bioimaging, multidimensional precision detection, wavelength-division-multiplexed micro-optical communication systems, and other fields.

Conventional metasurfaces suffer from fixed functions and single-mode responses, which can hardly meet the practical demands of dynamic reconfiguration and multi-channel multiplexing. To address this issue, in this work, a polarization-multiplexed binary-switching metasurface is developed based on the phase-change material Ge2Sb2Te5 (GST). The particle swarm optimization algorithm is employed to globally optimize the structural parameters of the metasurface nanopillars. By leveraging the crystalline/amorphous phase transition characteristics of GST, the dynamic switching modulation of metasurface functions is realized. Combined with polarization manipulation parameters, it is clarified that Gaussian focusing can be achieved under the condition of x-polarization and crystalline state, and vortex beam generation can be realized under y-polarization and amorphous state, thereby constructing a binary switching system with synergistic polarization-phase interaction. The proposed strategy exhibits promising application prospects in optical communications, quantum information, imaging systems and other related fields.

Objective Magnetic field sensing plays an irreplaceable role in a wide range of applications, including geological exploration, biomedical diagnostics, and military operations. Modern magnetic field data acquisition systems not only require the measurement of the absolute value of magnetic flux density but also demand simultaneous acquisition of spatial vector distribution and its temporal variations. These requirements impose stringent demands on sensor sensitivity, stability, and multi-parameter measurement capability. Conventional magnetic field sensors, such as Hall sensors, optically pumped magnetometers, and fluxgate magnetometers, have been widely used in specific applications; however, their reliance on electronic components renders them susceptible to strong electromagnetic interference. Furthermore, their performance can degrade significantly in harsh environments, such as high temperature, high humidity, strong corrosion, or intense radiation. Additionally, these sensors often have complex structures, bulky form factors, and high maintenance costs, making them unsuitable for long-term online monitoring or large-scale deployment. In contrast, optical fiber magnetic field sensing technology, which uses light waves as information carriers, offers distinct advantages including immunity to electromagnetic interference, corrosion resistance, lightweight design, long-distance signal transmission, and high sensitivity. Over the past decade, it has emerged as a promising solution for magnetic field measurements. However, most existing optical fiber magnetic field sensors are limited to measuring only the magnetic field intensity and cannot simultaneously capture vector direction information. This limitation poses challenges in high-precision navigation, geophysical exploration, medical imaging, and space magnetic environment monitoring. Therefore, developing a simple-structure, high-sensitivity optical fiber magnetic field sensor with vector measurement capability is of both theoretical and practical importance. To address this need, we propose a novel all-fiber vector magnetic field sensor based on magnetic fluid (MF), in which specialty optical fibers are integrated with magneto-sensitive materials. The sensor leverages the tunable refractive index property of MF and the multimode interference (MMI) effect to simultaneously measure magnetic field intensity and direction. The proposed design maintains a compact and symmetric structure, ensuring stable signal output, and can be fabricated through a low-cost, straightforward process suitable for batch production. This approach provides a new pathway for promoting optical fiber magnetic field sensing technology in vector measurement applications. Methods The core structure of the proposed vector magnetic field sensor comprises a single-mode fiber (SMF)-hollow-core fiber (HCF)-dual-core single-hole fiber (DCSHF)-HCF-SMF arrangement. First, the end faces of all fiber segments are prepared using a high-precision fiber cleaver to ensure minimal splicing loss. Subsequently, the fibers are directly aligned and fusion-spliced in sequence using a conventional fusion splicer under microscope assistance, resulting in a symmetric hybrid all-fiber configuration. To achieve magnetic field responsiveness, the fabricated fiber structure is encapsulated in a capillary quartz tube filled with MF, ensuring complete immersion of the sensing region in the magnetic fluid. The incorporation of two short HCF sections effectively excites multiple high-order cladding modes, which undergo interference in the sensing region and exhibit high sensitivity to variations in the surrounding refractive index. This significantly enhances the sensor's ability to detect MF refractive index changes. The inherent strong circular asymmetry of the DCSHF endows the sensor with natural sensitivity to the angular orientation of the magnetic field. When the external magnetic field changes in intensity or direction, the magnetic nanoparticles in the MF redistribute anisotropically, leading to a refractive index variation in the MF. This, in turn, alters the effective refractive index difference between propagating modes and causes a shift in the interference dip wavelength in the transmission spectrum. Real-time monitoring of this wavelength shift enables simultaneous acquisition of magnetic field intensity and direction information. In addition, because the refractive index of MF is also temperature-dependent, the interference dip wavelength experiences thermal drift. If required, an optical fiber Bragg grating (FBG) can be cascaded with the sensing structure to enable temperature compensation, thereby improving measurement accuracy in environments with varying temperatures. Results and Discussions Experimental results demonstrate that when the DCSHF length is 10 mm, the proposed sensor exhibits excellent linear responses in measuring both magnetic field intensity and direction. In the range of 43 -67 mT, the magnetic field sensitivity reaches-511 pm/mT with a linearity of 0.99. The sensor also demonstrates strong magnetic field orientation detection capability, with the polar response curve showing a symmetric and stable 8 pattern, and a maximum orientation sensitivity of-267 pm/(degrees). Moreover, within the temperature range of 40-65 degrees C, the sensor exhibits a temperature sensitivity of-172 pm/degrees C. Compared to similar MF-based optical fiber magnetic field sensors reported in the literature, the proposed device offers significant advantages in fabrication simplicity, sensitivity, and measurement range. Conclusions In this study, we have proposed a novel MF-coated all-fiber vector magnetic field sensor based on an SMF-HCF-DCSHF-HCF-SMF structure, capable of simultaneous measurement of magnetic field intensity, vector orientation, and temperature. Experimental results indicate that with a DCSHF length of 10 mm, the sensor achieves a maximum magnetic field sensitivity of-511 pm/mT over 43-67 mT, a maximum orientation sensitivity of-267 pm/(degrees), and a temperature sensitivity of-172 pm/degrees C within 40-65 degrees C. The sensor features a compact structure, simple fabrication process, low cost, high sensitivity, and excellent environmental adaptability, making it suitable for precision magnetic field measurements and multi-parameter monitoring in demanding environments.

Structured light beams have significant application value in fields like optical communication, microscopic imaging, and biomedicine due to their unique spatial field distribution characteristics. However, traditional structured beam generation systems based on discrete optical components have inherent drawbacks such as strict alignment requirements and poor tunability, which severely limit their practical applications. This paper proposes a new method for broadband bifunctional generation of structured beams based on fiber-integrated metasurfaces: by integrating spin-multiplexing bifunctional phase metasurfaces with the end faces of optical fibers, broadband sub-wavelength Bessel beams and focused vortex beams were, respectively, generated on demand in an all-fiber configuration when different circularly polarized light was input. The experimental measurements showed that the transmission characteristics of the generated beams were highly consistent with the numerical simulation results. Our scheme fully exploits the flexible waveguide (bendable) advantage of fibers, breaking through the constraint of poor optical path tunability in traditional "hard connection" systems due to strict alignment requirements. Since the implemented device simultaneously possesses broadband operation, sub-wavelength-scale field control, and spin-multiplexing characteristics, this study provides a new paradigm for multidimensional and multifunctional dynamic light field manipulation, and it holds significant application potential in fields such as fiber-optic imaging and fiber sensing. (c) 2026 Chinese Laser Press

In this work, a three-stage Time-to-digital converter (TDC) based on the average measurement in the system is proposed for ranging. The ranging chip needs to provide 20 MHz reference clock signal externally, which is doubled to 1 GHz through the Phase-Locked Loop (PLL) circuit and sent to TDC to provide stable high frequency reference clock signal for the circuit. The circuit uses PLL cascaded oscillator units to generate multiple clock signals and vernier delay structures to construct two-stage interpolation. During the measurement process, the input signal is allocated to different channels of the TDC for multiple measurements and averaging. This not only reduces the random error caused by clock jitter due to noise, but also improves the utilization of TDC channels. The chip is based on X-Fab 0.18 μm CMOS process, the core TDC layout area is 500 μm × 350 μm, the power consumption is about 16.55 mW, and the resolution is 14 ps. Analysis of the results of the post-simulation shows that the differential nonlinear peak is less than 0.4 LSB, and the integral nonlinear peak is less than 0.6 LSB. The dynamic range can increase the number of high-segment counter bits according to the needs of actual application scenarios. High measurement accuracy, linearity and wide dynamic range are achieved.

The propagation of vortex beams in anisotropic nonlocal nonlinear media(ANNM) gives rise to distinctive structural transformations. This paper investigates the dynamical behavior of an off-axis chirped Laguerre-elliptic Gaussian vortex beam (OACLEGVB) in such media, employing a combined approach of analytical derivation and high-resolution numerical simulation. Anisotropic nonlocality makes it difficult for OACLEGVB to maintain structural stability, and instead enables the periodic conversion between Laguerre-Gaussian (LG) modes and Hermite-Gaussian (HG) modes. The normalized rotation angular momentum J_o is effectively governed solely by the second-order chirp parameter(SOCP), the mode parameter, and the anisotropic nonlocality parameter(ANP). The normalized revolution angular momentum J_e is precisely manipulated by the off-axis parameter(OAP), the SOCP, the ANP and the incident direction. Interestingly, when the power is constant( P = P_cx = P_cy ), the parameters of the higher-order mode beams have a linear relationship with those of the fundamental mode beams. The anisotropic nonlocal modulation breaks the rotational symmetry of the beam, resulting in the normalized orbital angular momentum not being a constant value and triggering periodic oscillation phenomena. This study provides a theoretical foundation for the precise control of propagation trajectory, mode interconversion, and optical field structuring of the OACLEGVB in anisotropic nonlocal nonlinear media.

This paper presents, to our knowledge, a novel micro-ring wavelength selective switch device based on a contradirectional coupler (contra-DC), which utilizes the transparent window formed by the contra-DC to select the single resonant wavelength of the micro-ring resonator, avoiding the limitation of free spectral range and realizing the function of wavelength selection/switching. The desired wavelength switching function is achieved by changing the crystal state of the Ge2Sb2Te5 (GST) loaded on the micro-ring resonator. When the device is in the on state, the desired wavelength signal is selectively output from the drop port of the bus waveguide; when the device is in the off state, light is output from the through port. By modifying the GST crystal state, selective routing of light can be achieved, which can be used in optical interconnection networks. The simulation is performed using a 3D finite-difference method. The wavelength selection device achieves a 3 dB bandwidthof 1.6 nm with a side lobe suppression ratio of 20 dB at a length of 230 mu m; the switching device achieves the extinction ratio of about 14.7 dB and a side lobe suppression ratio of 18.2 dB between the on/off states. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

We have proposed and experimentally demonstrated a vector magnetic field sensor based on a magneto-sensitive functionalized three-core fiber (TCF) structure. The fiber-optic magnetic field sensor adopts a sandwich-like magnetofluid encapsulated single-mode fiber (SMF)-TCF-SMF structure. Owing to the noncircular symmetric structure, thereby enabling the fiber sensing structure exhibits response to environmental magnetic field strength and direction. The experimental results shows that the maximum strength sensitivity and direction sensitivity are -1.23 nm/mT and 0.73 nm/degrees, respectively, within the range of 35-44 mT when the TCF length is 10 mm. The proposed magnetic field sensor offers several advantages, including simple structure, ease of fabrication, and high sensitivity.

We propose a design method for few-mode erbium-doped fiber (FM-EDF) incorporating stratified doping. In the simulation design, the FM-EDF effectively reduces the differential mode gain (DMG) through the utilization of stratified doping. Simulations indicate that at an input signal power of -30 dBm, the designed fiber achieves a DMG of less than 0.5 dB across five spatial modes spanning the entire C-band (1530-1570 nm) and exceeds 20 dB gain within the range of 1530-1560 nm. Additionally, experiments using unidirectional pumping demonstrate that the FM-EDF achieves full-band gain greater than 20 dB, with a maximum gain approaching 30 dB and DMG <1 dB, across the C-band in three spatial modes. In summary, the proposed FM-EDF enhances the efficiency and reliability of long-distance signal transmission in optical communication networks, making it suitable for high-capacity optical fiber communication systems as well as long-distance sensing systems.

The work describes a surface plasmon resonance (SPR) sensor that measures the liquid level and refractive index (RI) simultaneously. The sensor is fabricated by a polymer optical fiber (POF) with a side-polished spiral structure. The POF is wound around a plastic rod with the same pitch and polished into a series of separated side-polished areas to form the sensor probe. Afterwards, the polished surfaces are coated with a gold layer to construct the SPR sensor. The proposed sensor can provide multi-point liquid-level measurement besides RI sensing. The influences of structural parameters such as the bending radius, polishing depth, and pitch on the sensing performance are experimentally studied. The experimental results indicate that the RI could be determined by employing the SPR wavelength shift, and the RI sensitivity of 1862 nm/RIU within the 1.34–1.40 range is obtained. Moreover, the SPR peak’s depth variation can be utilized to monitor the liquid level, and the sensor can provide adjustable resolution and a measurement range for liquid level sensing. With its simple fabrication, low cost, and flexible sensing ability, this sensor probe is suitable for the usage in biochemical applications.

This paper describes a laser ranging system based on modulation signal resampling to address the nonlinearity of Frequency-modulated in frequency-modulated continuous wave (FMCW) lidar. Using a 1550 nm DFB laser as a frequency-modulated light source, the modulation scheme adopts direct modulation of the injected current into the semiconductor laser. Based on the equal-frequency resampling method, the clock signal used for resampling undergoes data acquisition, data analysis, and data processing steps to identify and eliminate erroneous sampling points caused by laser frequency noise, mode hopping in frequency-modulated lasers, and sweep reversal points in the injection current. It solves the nonlinear error caused by the relaxation-oscillation effect of the prior art. Additionally, compared with the manual division of sampling points, the algorithm dividing the sampling area can retain as many correct sampling points as possible to improve the distance resolution and repeatability accuracy of the FMCW ranging system. Under the condition of approximately 20 GHz laser modulation bandwidth, the resolution of 10 m in free-space optical ranging is about 6.8 mm and the standard deviation (STD) of 1 m in free-space optical ranging is 0.19 mm.

Metasurfaces have demonstrated significant potential for applications in high-resolution imaging and information security. However, conventional metasurfaces holographic techniques are constrained by low transmittance and limited tunability. In this study, we propose a color image encryption scheme based on a metasurface composed of "dynamic" pixels (Sb2S3) and "static" pixels (Silicon), wherein the color information of the image serves as an integral component of the encrypted data. By manipulating parameters such as polarization state, wavelength of incident light, and crystallization level of Sb2S3, we can flexibly control the display of multichannel color images in both near-field and far-field scenarios. Specifically, images containing specific color information can be displayed only when the incident light is at two specific wavelengths and the crystallization level of Sb2S3 is known. Conversely, at a single wavelength, only a predetermined portion of the image can be displayed. The proposed metasurface represents a potential approach for ultra-high capacity dynamic holographic displays, color image encryption, and efficient information storage.

The majority of current beam conversion techniques rely on bulky lens systems for operation. In this paper, we propose a terahertz metasurface that can effectively convert a Gaussian beam into a flat-top beam and convert linearly polarized terahertz waves into their orthogonal counterparts. An improved Gerchberg-Saxton (GS) algorithm was employed in this study to precisely calculate the required phase distribution for the beam shaping device. By adjusting the opening angle of the metal split ring in the middle layer of the metasurface, a full 2π phase coverage was achieved, ensuring precise control over the phase distribution. Simulation results indicate that within the range of 0.4-1.1 THz, the cross-polarization conversion efficiency is greater than 70%, with a relative bandwidth of 93.3%. The root-mean-square error (RMS) can reach 0.143 at 0.75 THz, the non-uniformity of the rectangular spot in the target region is 0.126, and the energy ratio of the rectangular spot to the whole focal plane is 78.03%, demonstrating the achievement of a high-quality flat-top beam. The metasurface beam shaping device we proposed, with its wide operating bandwidth, low transmission loss, high shaping efficiency, and compact structural design, offers an innovative solution for beam shaping techniques in the terahertz frequency band.

This article proposes and demonstrates a magnetic fluid (MF)-coated optical fiber vector magnetic field sensor by fusing a section of side-polished eccentric-core fiber (ECF) between two sections of single-mode fibers. Owing to the distinctive internal structural asymmetry of the ECF, and through the side-polishing process to remove a portion of the cladding, the interaction between the evanescent field and the surrounding MF is enhanced, thereby improving the sensor's sensitivity. The experimental results show that the sensor's sensitivity depends on the side-polishing depth and eccentricity of the ECF. When the eccentricity of the ECF is 20 mu m and the side-polishing depth is 10.40 mu m, the intensity sensitivity of 0.791 dB/mT and 569 pm/mT and the direction sensitivity of 517 pm/degrees are obtained. The proposed all-optical fiber magnetic field sensor has the advantages of compact structure, low cost, and convenient manufacture.

Off-axis-rotating elliptical Gaussian beams(OareGB)oblique incidence in strong nonlocal medium exhibit novel propagation properties.The analytical expressions of semi-axial beam widths,and center-of-mass trajectory equations for transmitting off-axis-rotating elliptical Gaussian beams in strong nonlocal media are obtained using the ABCD transfer matrix method.The study revealed that the trajectory of the mass's center in the cross-section can be controlled by changing the sizes of the OareGB parameters c,d,ζ,and f.The gradient force of the light field causes the spot region to form a spatial potential well in the media,and this spatial potential well can effectively capture nanoparticles.The particles captured by the light field can move along with the beam,realizing the effective manipulation of the particle trajectory.These laws may be applied to modulating the propagation path of light beams and optical tweezer technology.

Integrated photonics is increasingly widely applied in fields such as optical communication and optical micro-operation, especially demonstrating great potential in the dynamic regulation of light wave characteristics. The orbital angular momentum (OAM) carried by vortex beams offers abundant orthogonal channels for optical communication; however, existing generation approaches frequently encounter issues such as large volume, high cost, and complex structure. This paper successfully realizes an ultra-compact dynamic OAM generation device by integrating phase-change materials with a trench waveguide. The device can dynamically generate OAM modes with topological charges of ±1, without changing the physical structure by taking advantage of the refractive index difference between the crystalline and amorphous states of the phase change materials. This design not only reduces the device length to 9.5µm but also enhances its applicability to multiple wavelengths of light waves, presenting extensive possibilities for the development of new photonic devices and systems in fields such as optical communication, quantum information processing, and optical micro-operation.

Far-Field Imaging Metasurfaces leverage their ability to display distinct images at different spatial positions, demonstrating significant application potential in fields such as optical device miniaturization and medical imaging. However, existing design methods typically rely on the Gerchberg-Saxton (GS) algorithm, which primarily optimizes the phase distribution while neglecting the impact of the metasurface unit amplitude distribution on far-field imaging performance. This limitation constrains imaging quality and generally restricts clear image formation to a single depth.To address these limitations, we introduce a Multi-Distance Imaging Metasurface designed using deep learning. This approach breaks through the constraint of single-depth imaging, enabling the formation of multiple clear, independent images at varying observation distances (depths). This advancement enhances metasurface imaging performance.