Photonics

15 pages, 4558 KiB

Open AccessArticle

Red Blood Cell-Based Biological Micromotors Propelled by Spiral Optical Fields

by Kunpeng Wang, Zhelin Qu, Yifei Chen, Tianli Wu, Chao Feng, Jian Zhang, Xian Zhao and Jun-Lei Wang

Photonics 2025, 12(6), 531; https://doi.org/10.3390/photonics12060531 - 23 May 2025

Abstract

Micromotors play a crucial role in microsystems technology, with applications in nanoparticle propulsion, targeted drug delivery, and biosensing. Optical field propulsion, particularly optical tweezers (OTs), enables precise, noncontact control but traditionally relies on Gaussian traps, which require preprogramming and offer limited rotational control. [...] Read more.

Micromotors play a crucial role in microsystems technology, with applications in nanoparticle propulsion, targeted drug delivery, and biosensing. Optical field propulsion, particularly optical tweezers (OTs), enables precise, noncontact control but traditionally relies on Gaussian traps, which require preprogramming and offer limited rotational control. Here, we introduce a micromotor driven by optical vortex beams, utilizing phase gradients to generate optical torque. This eliminates preprogramming and enables real-time control over rotation and positioning. Using this method, we design red blood cell (RBC)-based micromotors for targeted cellular debris collection in liquid environments. Our findings provide a versatile strategy for micro-/nano-object manipulation with potential applications in biomedicine and precision transport. Full article

(This article belongs to the Special Issue Coherence Manipulation, Propagation and Applications of Vortex Beam)

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15 pages, 6035 KiB

Open AccessArticle

Machine Learning-Assisted Optimization of Femtosecond Laser-Induced Superhydrophobic Microstructure Processing

by Lifei Wang, Yucheng Gu, Xiaoqing Tian, Jun Wang, Yan Jia, Junjie Xu, Zhen Zhang, Shiying Liu and Shuo Liu

Photonics 2025, 12(6), 530; https://doi.org/10.3390/photonics12060530 (registering DOI) - 23 May 2025

Abstract

Superhydrophobic surfaces have garnered significant attention due to their pivotal roles in various fields. Femtosecond laser technology provides a feasible means for inducing superhydrophobic microstructures on material surfaces. However, due to the unclear influence mechanisms of process parameters, as well as the high [...] Read more.

Superhydrophobic surfaces have garnered significant attention due to their pivotal roles in various fields. Femtosecond laser technology provides a feasible means for inducing superhydrophobic microstructures on material surfaces. However, due to the unclear influence mechanisms of process parameters, as well as the high cost and time-consuming nature of experiments, identifying the optimal femtosecond laser processing parameters within the process space remains a significant challenge. To address this issue, a process optimization framework that couples machine learning and genetic algorithms was proposed and successfully applied to the optimization of femtosecond laser-induced groove structures on TC4 alloy surfaces. Firstly, based on 64 sets of experimental data, the effects of the power, scanning speed, and scanning interval on the micro-groove structures and their wetting properties were discussed in detail. Furthermore, by utilizing this small sample dataset, various machine learning algorithms were employed to establish a prediction model for the contact angle, among which support vector regression demonstrated the optimal predictive accuracy. Three additional dimensional variables, i.e., the number of effective pulses, energy deposition rate, and roughness, were also added to the original dataset vectors as extra dimensions to participate in and guide the model training process. The prediction model was further coupled into a genetic algorithm to achieve the quantitative design of femtosecond laser processing. Compared to the best hydrophobicity in the original dataset, the contact angle of the designed process was improved by 5.5%. The proposed method provides an ideal solution for accurately predicting wetting properties and identifying optimal processes, thereby accelerating the development and application of femtosecond laser-induced superhydrophobic microstructures. Full article

(This article belongs to the Special Issue Ultrafast Optics: From Fundamental Science to Applications)

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20 pages, 1124 KiB

Open AccessReview

Advances in and Applications of Microwave Photonics in Radar Systems: A Review

by Luka Podbregar, Boštjan Batagelj, Aljaž Blatnik and Andrej Lavrič

Photonics 2025, 12(6), 529; https://doi.org/10.3390/photonics12060529 - 23 May 2025

Abstract

Modern radar systems frequently encounter constraints on bandwidth, transmission speed, and resolution, particularly within complex electromagnetic settings. Microwave photonics (MWP) provides solutions through the integration of photonic elements to improve radar’s functionalities. This review paper examines the question of how to improve radar [...] Read more.

Modern radar systems frequently encounter constraints on bandwidth, transmission speed, and resolution, particularly within complex electromagnetic settings. Microwave photonics (MWP) provides solutions through the integration of photonic elements to improve radar’s functionalities. This review paper examines the question of how to improve radar performance by using MWP-based radar components for signal transmission, local oscillator signal generation, radar waveforming, optical beamforming networks, mixing, filtering, co-site interference suppression, real-time Fourier transformation, and analog-to-digital conversion. MWP radar systems achieve wider bandwidths, greater resistance to electromagnetic interference, and reduced phase noise, size, weight, and power consumption. Consequently, the integration of MWP into radar systems has the potential to increase the accuracy of these systems. Full article

(This article belongs to the Special Issue Recent Advancement in Microwave Photonics)

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19 pages, 2392 KiB

Open AccessArticle

Intelligent Resource Allocation for Immersive VoD Multimedia in NG-EPON and B5G Converged Access Networks

by Razat Kharga, AliAkbar Nikoukar and I-Shyan Hwang

Photonics 2025, 12(6), 528; https://doi.org/10.3390/photonics12060528 - 22 May 2025

Abstract

Immersive content streaming services are becoming increasingly popular on video on demand (VoD) platforms due to the growing interest in extended reality (XR) and spatial experiences. Unlike traditional VoD, immersive VoD (IVoD) offers more engaging and interactive content beyond conventional 2D video. IVoD [...] Read more.

Immersive content streaming services are becoming increasingly popular on video on demand (VoD) platforms due to the growing interest in extended reality (XR) and spatial experiences. Unlike traditional VoD, immersive VoD (IVoD) offers more engaging and interactive content beyond conventional 2D video. IVoD requires substantial bandwidth and minimal latency to deliver its interactive XR experiences. This research examines intelligent resource allocation for IVoD services across NG-EPON and B5G X-haul converged networks. A proposed software-defined networking (SDN) framework employs artificial neural networks (ANN) with a backpropagation technique to predict bandwidth control based on traffic patterns and network conditions. The new immersive video storage, field-programmable gate array (FPGA), Queue Manager, and logical layer components are added to the existing OLT and ONU hardware architecture to implement the SDN framework. The SDN framework manages the entire network, predicts bandwidth requirements, and operates the immersive media dynamic bandwidth allocation (IMS-DBA) algorithm to efficiently allocate bandwidth to IVoD network traffic, ensuring that QoS metrics are met for IM services. Simulation results demonstrate that the proposed framework significantly enhances mean packet delay by up to 3% and improves packet drop probability by up to 4% as the traffic load varies from light to high across different scenarios, leading to enhanced overall QoS performance. Full article

(This article belongs to the Section Optical Communication and Network)

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21 pages, 2362 KiB

Open AccessArticle

Non-Markovian Dynamics of Giant Atoms Embedded in an One-Dimensional Photonic Lattice with Synthetic Chirality

by Vassilios Yannopapas

Photonics 2025, 12(6), 527; https://doi.org/10.3390/photonics12060527 - 22 May 2025

Abstract

In this paper we investigate the non-Markovian dynamics of a giant atom coupled to a one-dimensional photonic lattice with synthetic gauge fields. By engineering a complex-valued hopping amplitude, we break reciprocity and explore how chiral propagation and phase-induced interference affect spontaneous emission, bound-state [...] Read more.

In this paper we investigate the non-Markovian dynamics of a giant atom coupled to a one-dimensional photonic lattice with synthetic gauge fields. By engineering a complex-valued hopping amplitude, we break reciprocity and explore how chiral propagation and phase-induced interference affect spontaneous emission, bound-state formation, and atom–field entanglement. The giant atom interacts with the lattice at multiple, spatially separated sites, leading to rich interference effects and decoherence-free subspaces. We derive an exact expression for the self-energy and perform real-time Schrödinger simulations in the single-excitation subspace, for the atomic population, von Neumann entropy, field localization, and asymmetry in emission. Our results show that the hopping phase

ϕ

governs not only the directionality of emitted photons but also the degree of atom–bath entanglement and photon localization. Remarkably, we observe robust bound states inside the photonic band and directional asymmetry, due to interference from spatially separated coupling points. These findings provide a basis for engineering non-reciprocal, robust, and entangled light–matter interactions in structured photonic systems. Full article

(This article belongs to the Special Issue Advanced Research in Quantum Optics)

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12 pages, 8961 KiB

Open AccessCommunication

Damage Characteristics in Glass Fiber-Reinforced Epoxy Resin Composites Under Continuous Wave and Pulsed Laser Modes

by Xue Zhang, Jian Peng, Tengfei Li, Jing Xiao, Guiyong Chen, Yanjun Tang, Miao He and Jinghua Han

Photonics 2025, 12(6), 526; https://doi.org/10.3390/photonics12060526 - 22 May 2025

Abstract

Composite materials have been extensively utilized in unmanned aerial vehicles (UAVs) and other aerospace applications due to their unique advantages, while laser countermeasures have emerged as a critical approach in anti-UAV warfare. Different laser modes produce significantly different effects. In this study, we [...] Read more.

Composite materials have been extensively utilized in unmanned aerial vehicles (UAVs) and other aerospace applications due to their unique advantages, while laser countermeasures have emerged as a critical approach in anti-UAV warfare. Different laser modes produce significantly different effects. In this study, we have mainly considered the ablation and damage characteristics of composite materials affected by continuous wave (CW) and pulsed laser (PL) modes. Through comparative analysis of damage morphologies and elemental variations, the damage characteristics and mechanisms of composite materials have been studied, and thermodynamic models have been established. The results demonstrate that the damage produced using the CW mode is primarily thermal ablation, induced through power intensification, whereas the PL mode predominantly causes thermal stress fractures via energy concentration. This investigation provides fundamental references for optimizing laser-based counter-UAV systems. Full article

(This article belongs to the Special Issue Combined Pulse Laser: A Reliable Tool for High-Quality, High-Efficiency Material Processing)

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12 pages, 1810 KiB

Open AccessArticle

Nanoscale Temperature Sensor with Dual Circular and Square Structures Based on MIM Waveguides

by Shubin Yan, Hongfu Chen, Yuanyuan Gao, Weixin Liu, Xiaoran Yan, Aiwei Xu and Taiquan Wu

Photonics 2025, 12(6), 525; https://doi.org/10.3390/photonics12060525 - 22 May 2025

Abstract

This paper proposes a refractive index sensor with high sensitivity, which operates based on the Fano resonance phenomenon. The sensor is constructed using a metal–insulator–metal (MIM) waveguide integrated with a double square ring (DSR) configuration, enabling enhanced performance in refractive index detection. The [...] Read more.

This paper proposes a refractive index sensor with high sensitivity, which operates based on the Fano resonance phenomenon. The sensor is constructed using a metal–insulator–metal (MIM) waveguide integrated with a double square ring (DSR) configuration, enabling enhanced performance in refractive index detection. The propagation characteristics of the proposed structure are systematically investigated using the finite element method (FEM). Using a control variable method, this study systematically investigates the impact of refractive index changes and specific geometric parameters of the DSR structure on the sensor’s performance. Through the careful optimization of structural parameters, the sensor achieves a peak sensitivity (S) of 2700 nm/RIU along with a figure of merit (FOM) as high as 54. Owing to its simple configuration and high sensitivity, the proposed sensor holds significant potential for applications in temperature sensing and related fields. Full article

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11 pages, 9569 KiB

Open AccessArticle

MgO-Based Fabry-Perot Vibration Sensor with a Fiber-Optic Collimator for High-Temperature Environments

by Jiacheng Tu, Qirui Zhao, Jiantao Hu, Yuhao Huang, Haiyang Wang, Jia Liu and Pinggang Jia

Photonics 2025, 12(6), 524; https://doi.org/10.3390/photonics12060524 - 22 May 2025

Abstract

In this paper, a MgO-based high-temperature Fabry-Perot (F-P) vibration sensor with a fiber-optic collimator is proposed and experimentally demonstrated at 1000 °C. The sensor is composed of a sensing unit and a fiber-optic collimator. The F-P cavity is formed by the upper surface [...] Read more.

In this paper, a MgO-based high-temperature Fabry-Perot (F-P) vibration sensor with a fiber-optic collimator is proposed and experimentally demonstrated at 1000 °C. The sensor is composed of a sensing unit and a fiber-optic collimator. The F-P cavity is formed by the upper surface of the inertial mass block and the countersunk hole of the cover layer. The length of the F-P cavity changes with external vibrations. The sensing unit is prepared by wet etching technology and three-layer direct bonding technology, which ensure its stability and reliability in high-temperature environments. The experimental results indicate that the sensor can operate stably within a range from room temperature up to 1000 °C. The sensitivity and non-linearity of the sensor at 1000 °C are 1.3224 nm/g and 3.8%, respectively. Furthermore, the sensor operates at frequencies of up to 4 kHz while remaining unaffected by lateral vibration signals. The high-temperature F-P vibration sensor can effectively deal with the fiber damage in extreme environments and exhibits considerable potential for widespread applications. Full article

(This article belongs to the Special Issue Emerging Trends in Fiber Optic Sensing)

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19 pages, 3423 KiB

Open AccessArticle

Reexamination of Gain Theory for Intrinsic Photoconductive Devices

by Nenad Vrucinic and Yong Zhang

Photonics 2025, 12(5), 523; https://doi.org/10.3390/photonics12050523 - 21 May 2025

Abstract

The quantum efficiency

(Q E)

or gain

(G)

of a photoconductive device is most commonly given in the literature as a ratio of carrier lifetime to transit time, allowing for a value much greater than unity. In this work, [...] Read more.

The quantum efficiency

(Q E)

or gain

(G)

of a photoconductive device is most commonly given in the literature as a ratio of carrier lifetime to transit time, allowing for a value much greater than unity. In this work, by assuming primary photoconductivity, we reexamine the photoconductive theory for the device with an intrinsic (undoped) semiconductor, with nearly zero equilibrium carrier densities. Analytic gain formula is obtained for arbitrary drift and diffusion parameters under a bias voltage and by neglecting the polarization effect due to the relative displacement in the electron and hole distributions. We find that the lifetime/transit-time ratio formula is only valid in the limit of weak field and no diffusion. Numerical simulations are performed to examine the polarization effect, confirming that it does not change the qualitative conclusions. We discuss the distinction between two

Q E

definitions used in the literature: accumulative

Q E

({Q E}_{a c c})

, considering the contributions of the flow of all photocarriers, regardless of whether they reach the electrode; and apparent

Q E

(

{Q E}_{a p p})

, measuring the photocurrent at the electrode. In general,

{Q E}_{a c c} > {Q E}_{a p p}

, due to an inhomogeneous photocurrent in the channel; however, both approach the same unity limit for strong drift. We find that

{Q E}_{a c c} \neq {Q E}_{a p p}

is a deficiency of the commonly adopted constant-carrier-lifetime approximation in the recombination terms. Full article

(This article belongs to the Special Issue Advances in Integrated Photonics)

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14 pages, 15441 KiB

Open AccessCommunication

Numerical Study of Electric Field Enhancement in Inverted-Pyramid Gold Arrays with Tunable Spacing

by Yaumalika Arta, Iman Santoso, Hao Chang, Ying-Pin Tsai, Fu-Li Hsiao, Tsung-Shine Ko and Yang-Wei Lin

Photonics 2025, 12(5), 522; https://doi.org/10.3390/photonics12050522 - 21 May 2025

Abstract

This study presents a comprehensive numerical and experimental investigation of electric field enhancement in inverted-pyramidal gold (Au) array substrates, focusing on variable inter-pyramidal spacing for surface-enhanced Raman scattering (SERS) applications. We conducted a series of finite element method (FEM) simulations to model the [...] Read more.

This study presents a comprehensive numerical and experimental investigation of electric field enhancement in inverted-pyramidal gold (Au) array substrates, focusing on variable inter-pyramidal spacing for surface-enhanced Raman scattering (SERS) applications. We conducted a series of finite element method (FEM) simulations to model the spatial distribution of electromagnetic fields within plasmonic metasurfaces under 780 nm laser excitation. The results show that reducing the spacing between inverted pyramidal structures from 10 μm to 3.2 μm significantly increases the electric field intensity at both the tip and edge regions of the inverted-pyramidal Au structure, with maximum fields reaching 6.75 × 10⁷ V/m. Experimental SERS measurements utilizing 4-mercaptobenzoic acid as a Raman reporter support the simulation findings, indicating enhanced signal intensity in closely spaced configurations. These results confirm that geometric field concentration and plasmonic coupling are the dominant mechanisms responsible for SERS enhancement in these systems. This work provides a strategic framework for optimizing the geometry of plasmonic substrates to improve the sensitivity and reliability of SERS-based sensing platforms. Full article

(This article belongs to the Topic Nanomaterials for Photonics and Optoelectronics: Practical Applications and Advances)

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Graphical abstract

11 pages, 544 KiB

Open AccessCommunication

Optical Unidirectional Transport and Directional Blockade in Cold Atoms via Non-Hermitian Four-Wave Mixing

by Xiao Liu, Maurizio Artoni, Giuseppe La Rocca and Jinhui Wu

Photonics 2025, 12(5), 521; https://doi.org/10.3390/photonics12050521 - 21 May 2025

Abstract

We propose a scheme for realizing nonreciprocal optical scattering with non-Hermitian four-wave mixing (FWM) in a double-

Λ

system of cold atoms driven by coupling and dressing phase-mismatched standing-wave (SW) fields. Four scattering channels—direct transmission, cross transmission, direct reflection, and cross reflection—can be [...] Read more.

We propose a scheme for realizing nonreciprocal optical scattering with non-Hermitian four-wave mixing (FWM) in a double-

Λ

system of cold atoms driven by coupling and dressing phase-mismatched standing-wave (SW) fields. Four scattering channels—direct transmission, cross transmission, direct reflection, and cross reflection—can be established for a probe and a signal field, some of which are nonreciprocal due to non-Hermitian spatial modulations when the two SW driving fields exhibit a

π / 4

phase shift. We find in particular that it is viable to attain single-color unidirectional transport, dual-color unidirectional transport, and single-color directional blockade with respect to a probe and a signal field incident upon this atomic sample from the same side, due to perfect destructive interference between direct and cross scattering channels. This work provides a new paradigm for studying non-Hermitian nonlinear optics and offers a theoretical foundation for designing all-optical atomic devices based on multi-channel nonreciprocal scattering. Full article

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13 pages, 1627 KiB

Open AccessArticle

Effects of Light Source Coherence and Offset-Launching Distance on Performance in 49.4 km Power over Multimode Fiber Systems

by Yuemei Li, Yao Guo, Zhaoyang Zhang, Haobo Guo and Zhiguo Zhang

Photonics 2025, 12(5), 520; https://doi.org/10.3390/photonics12050520 - 21 May 2025

Abstract

Based on the offset-launching (OL) scheme, the effects of light source coherence and OL distance on the power performance of the 49.4 km power over fiber (PoF) system using multimode fiber are systematically investigated. We analyzed the effects of light source coherence and [...] Read more.

Based on the offset-launching (OL) scheme, the effects of light source coherence and OL distance on the power performance of the 49.4 km power over fiber (PoF) system using multimode fiber are systematically investigated. We analyzed the effects of light source coherence and OL distance on the maximum output power by constructing PoF experimental systems with four different light sources and 30 μm OL ranges. The experimental results show that the OL scheme can significantly enhance the output power in PoF systems with different light source and OL distance configurations. For coherence, the 20 nm light source with weaker coherence performs best in the 10.8 km–36 km PoF link, the advantage of the 12 nm light source is gradually reflected in the range 41 km–49.4 km, and the 2 nm light source is expected to realize the optimal output power in longer-distance. For OL distance, the 20 nm light source performs best in the range of 0–12.5 μm, and the 12 nm light source shows the best performance after exceeding 15 μm. This paper summarizes the optimal light source and OL distance configurations, the work provides ideas for performance enhancement and optimal design of the PoF system, as well as an experimental basis for energy supply to remote devices. Full article

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11 pages, 2649 KiB

Open AccessArticle

Design of an Integrated Circularly Polarized HgCdTe Photodetector Based on Silicon Metasurfaces

by Bo Cheng, Yuxiao Zou, Zihui Ge, Hanxiao Shao, Kunpeng Zhai and Guofeng Song

Photonics 2025, 12(5), 519; https://doi.org/10.3390/photonics12050519 - 21 May 2025

Abstract

Compared with conventional detectors, a circularly polarized detector operating at 4.26 μm effectively suppresses background noise (e.g., solar scattering and atmospheric interference), enabling high-precision CO₂ monitoring across ecosystems like farmland, forests, and wetlands. This capability allows the precise quantification of carbon sink [...] Read more.

Compared with conventional detectors, a circularly polarized detector operating at 4.26 μm effectively suppresses background noise (e.g., solar scattering and atmospheric interference), enabling high-precision CO₂ monitoring across ecosystems like farmland, forests, and wetlands. This capability allows the precise quantification of carbon sink potential and ecosystem health. Our design employs a mid-wave HgCdTe detector—a well-established platform—combined with a CMOS-compatible Si/SiO₂ metasurface. Geometric displacements were applied to break C₂ symmetry, achieving a chiral design. Through multiparameter optimization, we realized a circularly polarized photodetector (CPPD) with a CPER of 18 dB, expected to demonstrate superior CO₂ monitoring performance. These advances may offer researchers and practitioners a robust tool for both fundamental studies and field deployments. Full article

(This article belongs to the Special Issue Latest Advances in Optical Diffraction, Imaging and Display)

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12 pages, 4893 KiB

Open AccessArticle

Wideband Near-Infrared Hot-Electron Photodetector Based on Metal Grating Structure

by Hao Huang, Fei Liu, Zidong Chen, Bowen Zhang and Ailing Zhang

Photonics 2025, 12(5), 518; https://doi.org/10.3390/photonics12050518 - 21 May 2025

Abstract

The generation of hot electrons through non-radiative decay processes of surface plasmons (SPs) has been extensively demonstrated, enabling the preparation of high-performance hot-electron photodetectors without limitations imposed by material band gap widths. In this paper, a near-infrared wideband hot-electron metal semiconductor photodetector (WHEMSPD) [...] Read more.

The generation of hot electrons through non-radiative decay processes of surface plasmons (SPs) has been extensively demonstrated, enabling the preparation of high-performance hot-electron photodetectors without limitations imposed by material band gap widths. In this paper, a near-infrared wideband hot-electron metal semiconductor photodetector (WHEMSPD) is proposed based on a metal grating plasmonic structure, and its optical and electrical properties are numerically verified. This structure exhibits excellent broadband characteristics within the long-wave near-infrared range (LW-NIR) of 1200–1800 nm, achieving an absorption of approximately 0.7 between 1200 and 1700 nm, with a peak of 0.98 at 1400 nm. The metal grating structure can effectively enhance the excitation of plasmons on the surface and thus increase the absorption within a larger bandwidth. In terms of electrical performance, the responsivity of the WHEMSPD reaches over 20 mA/W within the wavelength range of 1200–1500 nm, with the peak responsivity reaching 28.3 mA/W around 1320 nm. WHEMSPDs in the LW-NIR can be widely used in military, remote sensing, communication, and other related fields. Full article

(This article belongs to the Special Issue Thermal Radiation and Micro-/Nanophotonics)

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16 pages, 2304 KiB

Open AccessArticle

Optical Design and Polarization Analysis for Full-Polarization Underwater Imaging Lens

by Zhongju Ren, Keyan Dong, Xiuhua Fu, Ying Lai and Jingjing Zhang

Photonics 2025, 12(5), 517; https://doi.org/10.3390/photonics12050517 - 21 May 2025

Abstract

Underwater polarization imaging has emerged as a fundamental technique for detecting and imaging underwater targets. However, the effectiveness of this technique is hampered by the low light intensity and optical system deformation induced by water pressure in deep-water environments, particularly for the detection [...] Read more.

Underwater polarization imaging has emerged as a fundamental technique for detecting and imaging underwater targets. However, the effectiveness of this technique is hampered by the low light intensity and optical system deformation induced by water pressure in deep-water environments, particularly for the detection of polarized signals. To address this issue, a wide-field-of-view oil-immersion lens tailored for deep-sea operations is designed, offering robust imaging performance and an extensive observation range. A Mueller matrix is deployed to scrutinize the polarization properties of the entire optical system across diverse fields of view, and the measurement errors in the polarization degree under incident polarization states are discussed. Simulation results demonstrate that the measurement error for linearly polarized light is greater than that for circularly polarized light. Therefore, the system adopts circularly polarized light as the active illumination source, characterized by minimal polarization effects and high detection accuracy. Finally, a deep-sea camera lens is produced and manufactured. The resulting lens is shown to pass a test in a hydrodynamic simulator machine, demonstrating that it can operate properly and capture images. Full article

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21 pages, 4138 KiB

Open AccessArticle

Noise Suppression in Quadrature Phase-Shift-Keying-Oriented All-Optical Matching Systems Using Highly Nonlinear Fiber

by Xin Li, Feiyang Ruan, Ying Tang, Tenglin Gao and Shanguo Huang

Photonics 2025, 12(5), 516; https://doi.org/10.3390/photonics12050516 - 21 May 2025

Abstract

All-optical matching systems that detect and localize designated target sequences in input all-optical data sequences have attracted significant attention in all-optical processing. They have various applications, including all-optical intrusion detection, optical frame alignment, and optical package identification. In real-world applications, noise is inevitable [...] Read more.

All-optical matching systems that detect and localize designated target sequences in input all-optical data sequences have attracted significant attention in all-optical processing. They have various applications, including all-optical intrusion detection, optical frame alignment, and optical package identification. In real-world applications, noise is inevitable and can lead to incorrect matching results. In particular, noise accumulates in serial all-optical matching systems, rendering the systems useless after several cycles. In this study, we developed a scheme for suppressing noise in quadrature phase-shift-keying (QPSK)-oriented all-optical matching systems. First, we evaluated the impact of input and amplifier noise on a QPSK-oriented all-optical matching system at a transmission rate of 100 Gbaud. We then developed a second-order noise-suppression structure using a highly nonlinear fiber (HNLF). With an input optical signal-to-noise ratio (OSNR) of 6 dB and an amplifier noise figure (NF) of 4 dB, the QPSK-oriented all-optical matching system without the noise-suppression structure output incorrect results. However, when the system was optimized using the proposed noise-suppression structure, correct matching results were obtained. Furthermore, when the NF of the amplifiers was fixed at 4 dB, the optimized system could reduce the minimum input OSNR to 0 dB. With an input OSNR of 0 dB, the logarithm of the bit error rate (BER) of the output matching results of the optimized system tended to negative infinity. The extinction ratio (ER), contrast ratio (CR), and quality (Q) factor of the output of the optimized system were 154.9532, 166.94289, and 161.12 dB, respectively, indicating high noise resistance. These results demonstrate that the system optimized using the proposed noise-suppression scheme exhibits high stability and reliability in noisy environments. Full article

(This article belongs to the Special Issue Advancements in Optical Information Processing and Communication Technologies)

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13 pages, 7359 KiB

Open AccessArticle

Tabletop 3D Display with Large Radial Viewing Angle Based on Panoramic Annular Lens Array

by Min-Yang He, Cheng-Bo Zhao, Xue-Rui Wen, Yi-Jian Liu, Qiong-Hua Wang and Yan Xing

Photonics 2025, 12(5), 515; https://doi.org/10.3390/photonics12050515 - 21 May 2025

Abstract

Tabletop 3D display is an emerging display form that enables multiple users to share viewing around a central tabletop, making it promising for the application of collaborative work. However, achieving an ideal ring-shaped viewing zone with a large radial viewing angle remains a [...] Read more.

Tabletop 3D display is an emerging display form that enables multiple users to share viewing around a central tabletop, making it promising for the application of collaborative work. However, achieving an ideal ring-shaped viewing zone with a large radial viewing angle remains a challenge for most current tabletop 3D displays. This paper presents a tabletop 3D display based on a panoramic annular lens array to realize a large radial viewing angle. Each panoramic annular lens in the array is designed with a block-structured panoramic front unit and a relay lens system, enabling the formation of a ring-shaped viewing zone and increasing the radial angle of the outgoing light. Additionally, the diffusion characteristics of the optical diffusing screen component are analyzed under large angles of incidence after light passes through the panoramic annular lens array. Then, a method for generating the corresponding elemental image array is presented. The results of the simulation experiments demonstrate that the viewing range is improved to −78.4–−42.2° and 42.6–78.9°, resulting in a total radial viewing angle of up to 72.5°, and the proposed 3D display can present a 360° viewable 3D image with correct perspective and parallax. Full article

(This article belongs to the Special Issue Research on Optical Materials and Components for 3D Displays)

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12 pages, 3972 KiB

Open AccessArticle

A Dengue Virus Detection Using Biosensor-Based Two-Dimensional Photonic Crystal Ring Resonator

by Nadhir Djeffal, Sarra Bendib and Abdallah Hedir

Photonics 2025, 12(5), 514; https://doi.org/10.3390/photonics12050514 - 21 May 2025

Abstract

This study proposes a novel two-dimensional photonic crystal ring resonator for detecting dengue-induced changes in blood components such as platelets, haemoglobin, and plasma. By monitoring shifts in the central wavelength linked to refractive index variations, the structure offers highly sensitive and accurate detection. [...] Read more.

This study proposes a novel two-dimensional photonic crystal ring resonator for detecting dengue-induced changes in blood components such as platelets, haemoglobin, and plasma. By monitoring shifts in the central wavelength linked to refractive index variations, the structure offers highly sensitive and accurate detection. The Lorentzian peak cavity exhibits a high-quality factor, achieving sensitivity up to 1800 nm/RIU, underscoring its potential as a precise diagnostic tool against dengue. Full article

(This article belongs to the Section Biophotonics and Biomedical Optics)

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44 pages, 2528 KiB

Open AccessReview

A Comprehensive Review of Rubidium Two-Photon Vapor Cell Optical Clock: Long-Term Performance Limitations and Potential Improvements

by Asagwegbe C. Obaze-Adeleke, Bryan Semon and Thejesh N. Bandi

Photonics 2025, 12(5), 513; https://doi.org/10.3390/photonics12050513 - 20 May 2025

Abstract

Two-photon vapor cell-based optical clocks are strong candidates for next-generation portable atomic standards, offering simplicity, compactness, and high performance. Their narrow clock transitions with counter-propagating beams enable first-order Doppler-free operation. However, systematic perturbations such as the AC Stark shift, temperature-induced shift, and drifts [...] Read more.

Two-photon vapor cell-based optical clocks are strong candidates for next-generation portable atomic standards, offering simplicity, compactness, and high performance. Their narrow clock transitions with counter-propagating beams enable first-order Doppler-free operation. However, systematic perturbations such as the AC Stark shift, temperature-induced shift, and drifts resulting from the laser system pose challenges cause instabilities to medium- to long-term performance. This paper provides a comprehensive overview of Rb two-photon vapor cell optical standards, focusing on the long-term performance-limiting effects and potential mitigation strategies, aiming for clock stabilities better than 1 × 10⁻¹⁵ over the averaging time of a day and beyond. Full article

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