Photonics

11 pages, 1758 KiB

Open AccessArticle

Nonlinear Absorption Properties of Phthalocyanine-like Squaraine Dyes

by Fan Zhang, Wuyang Shi, Xixiao Li, Yigang Wang, Leilei Si, Wentao Gao, Meng Qi, Minjie Zhou, Jiajun Ma, Ao Li, Zhiqiang Li, Hongming Wang and Bing Jin

Photonics 2025, 12(8), 779; https://doi.org/10.3390/photonics12080779 (registering DOI) - 1 Aug 2025

Abstract

This study synthesizes and comparatively investigates two squaric acid-based phthalocyanine-like dyes, SNF and its long-chain alkylated derivative LNF, to systematically elucidate the influence of peripheral hydrophobic groups on their third-order nonlinear optical (NLO) properties. The NLO characteristics were comprehensively characterized using femtosecond Z-scan [...] Read more.

This study synthesizes and comparatively investigates two squaric acid-based phthalocyanine-like dyes, SNF and its long-chain alkylated derivative LNF, to systematically elucidate the influence of peripheral hydrophobic groups on their third-order nonlinear optical (NLO) properties. The NLO characteristics were comprehensively characterized using femtosecond Z-scan and I-scan techniques at both 800 nm and 900 nm. Both dyes exhibited strong saturable absorption (SA), confirming their potential as saturable absorbers. Critically, the comparative analysis revealed that SNF exhibits a significantly greater nonlinear absorption coefficient (β) compared to LNF under identical conditions. For instance, at 800 nm, the β of SNF was approximately 3–5 times larger than that of LNF. This result conclusively demonstrates that the introduction of long hydrophobic alkyl chains attenuates the NLO response. Furthermore, I-scan measurements revealed excellent SA performance, with high modulation depths (e.g., LNF: 43.0% at 900 nm) and low saturation intensities. This work not only clarifies the structure–property relationship in these D-A-D dyes but also presents a clear strategy for modulating the NLO properties of organic chromophores for applications in near-infrared pulsed lasers. Full article

(This article belongs to the Section Optoelectronics and Optical Materials)

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14 pages, 3905 KiB

Open AccessArticle

Stability of Ultrafast Laser-Induced Stress in Fused Silica and Ultra-Low Expansion Glass

by Carolyn C. Hokin and Brandon D. Chalifoux

Photonics 2025, 12(8), 778; https://doi.org/10.3390/photonics12080778 (registering DOI) - 1 Aug 2025

Abstract

Stress fields imparted with an ultrafast laser can correct low spatial frequency surface figure error of mirrors through ultrafast laser stress figuring (ULSF): the formation of nanograting structures within the bulk substrate generates localized stress, creating bending moments that equilibrize via wafer deformation. [...] Read more.

Stress fields imparted with an ultrafast laser can correct low spatial frequency surface figure error of mirrors through ultrafast laser stress figuring (ULSF): the formation of nanograting structures within the bulk substrate generates localized stress, creating bending moments that equilibrize via wafer deformation. For ULSF to be used as an optical figuring process, the ultrafast laser generated stress must be effectively permanent or risk unwanted figure drift. Two isochronal annealing experiments were performed to measure ultrafast laser-generated stress stability in fused silica and Corning ultra-low expansion (ULE) wafers. The first experiment tracked changes to induced astigmatism up to 1000 °C on 25.4 mm-diameter wafers. Only small changes were measured after each thermal cycle up to 500 °C for both materials, but significant changes were observed at higher temperatures. The second experiment tracked stress changes in fused silica and ULE up to 500 °C but with 4 to 16× higher signal-to-noise ratio. Change in trefoil on 100 mm-diameter wafers was measured, and the induced stress in fused silica and ULE was found to be stable after thermal cycling up to 300 °C and 200 °C, respectively, with larger changes at higher temperatures. Full article

(This article belongs to the Special Issue Advances in Ultrafast Laser Science and Applications)

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2 pages, 149 KiB

Open AccessCorrection

Correction: Pogorelsky, I.V.; Polyanskiy, M.N. Harnessing Ultra-Intense Long-Wave Infrared Lasers: New Frontiers in Fundamental and Applied Research. Photonics 2025, 12, 221

by Igor V. Pogorelsky and Mikhail N. Polyanskiy

Photonics 2025, 12(8), 777; https://doi.org/10.3390/photonics12080777 (registering DOI) - 31 Jul 2025

Abstract

There were some text errors in the original publication [...] Full article

(This article belongs to the Special Issue High-Power Ultrafast Lasers: Development and Applications)

23 pages, 3850 KiB

Open AccessReview

Speckle-Correlation Holographic Imaging: Advances, Techniques, and Current Challenges

by Vinu R. V., Ziyang Chen and Jixiong Pu

Photonics 2025, 12(8), 776; https://doi.org/10.3390/photonics12080776 (registering DOI) - 31 Jul 2025

Abstract

The imaging modalities of correlation-assisted techniques utilize the inherent information present in the spatial correlation of random intensity patterns for the successful reconstruction of object information. However, most correlation approaches focus only on the reconstruction of amplitude information, as it is a direct [...] Read more.

The imaging modalities of correlation-assisted techniques utilize the inherent information present in the spatial correlation of random intensity patterns for the successful reconstruction of object information. However, most correlation approaches focus only on the reconstruction of amplitude information, as it is a direct byproduct of the correlation, disregarding the phase information. Complex-field reconstruction requires additional experimental or computational schemes, alongside conventional correlation geometry. The resurgence of holography in recent times, with advanced digital techniques and the adoption of the full-field imaging potential of holography in correlation with imaging techniques, has paved the way for the development of various state-of-the-art approaches to correlation optics. This review article provides an in-depth discussion of the recent developments in speckle-correlation-assisted techniques by focusing on various quantitative imaging scenarios. Furthermore, the recent progress and application of correlation-assisted holographic imaging techniques are reviewed, along with its potential challenges. Full article

(This article belongs to the Special Issue Recent Progress in Holography and Its Future Prospects)

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17 pages, 2389 KiB

Open AccessArticle

Designing an SOI Interleaver Using Genetic Algorithm

by Michael Gad, Mostafa Fedawy, Mira Abboud, Hany Mahrous, Gamal A. Ebrahim, Mostafa M. Salah, Ahmed Shaker, W. Fikry and Michael Ibrahim

Photonics 2025, 12(8), 775; https://doi.org/10.3390/photonics12080775 (registering DOI) - 31 Jul 2025

Abstract

A multi-objective genetic algorithm is tailored to optimize the design of a wavelength interleaver/deinterleaver device. An interleaver combines data streams from two physical channels into one. The deinterleaver does the opposite job. The WDM requirements for this device include channel spacing of 50 [...] Read more.

A multi-objective genetic algorithm is tailored to optimize the design of a wavelength interleaver/deinterleaver device. An interleaver combines data streams from two physical channels into one. The deinterleaver does the opposite job. The WDM requirements for this device include channel spacing of 50 GHz, channel bandwidth of 20 GHz, free spectral range of 100 GHz, maximum channel dispersion of 30 ps/nm, and maximum crosstalk of −23 dB. The challenges for the optimization process include the lack of a closed-form expression for the device performance and the trade-off between the conflicting performance parameters. So, for this multi-objective problem, the proposed approach maneuvers to find a compromise between the performance parameters within a few minutes, saving the designer the laborious design process previously proposed in the literature, which relies on visually inspecting the Z-plane for the dynamics of the transmission poles and zeros. Designs of better performance are achieved, with fewer ring resonators, a channel dispersion as low as 1.6 ps/nm, and crosstalk as low as −30 dB. Full article

(This article belongs to the Special Issue Advanced Materials and Devices for Silicon Photonics)

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9 pages, 1131 KiB

Open AccessArticle

The Impact of Low-Level Laser Irradiation on the Activity of Alpha-Amylase

by Mustafa Salih Al Musawi

Photonics 2025, 12(8), 774; https://doi.org/10.3390/photonics12080774 (registering DOI) - 31 Jul 2025

Abstract

Background: Clinical diagnostics, food industries, and biotechnological processes typically use an enzyme called alpha-amylase to metabolize carbohydrates. Objective: The aim of this study is to investigate how low-level laser irradiation (LLLI) affects alpha-amylase activity towards determining the usability of LLLI in non-invasive [...] Read more.

Background: Clinical diagnostics, food industries, and biotechnological processes typically use an enzyme called alpha-amylase to metabolize carbohydrates. Objective: The aim of this study is to investigate how low-level laser irradiation (LLLI) affects alpha-amylase activity towards determining the usability of LLLI in non-invasive enzymatic modulation. Methods: Enzyme solutions were irradiated at 10, 20, 30, and 40 J/cm² utilizing 589 nm and 532 nm diode-pumped solid-state lasers. The iodine–starch colorimetric method was used to quantify post-irradiation enzymatic activity, with inverse correlations found between absorbance and activity levels. Modulation was determined by the wavelength and dosage. Results: Enzymatic activity significantly improved when utilizing 589 nm irradiation at lower doses, maximizing at 120% at 20 J/cm² (p < 0.01). Neutral or inhibitory effects were revealed when higher doses were applied. Enzymatic activity showed progressive inhibition when 532 nm irradiation was applied, declining to 75% at 40 J/cm² (p < 0.01). Conclusions: These outcomes indicate that conformational flexibility and catalytic efficiency occur when applying lower-energy photons at 589 nm, whilst oxidative stress and impaired enzymatic function are induced by higher-energy photons at 532 nm. This is consistent with the biphasic dose–response characteristic of photobiomodulation. Full article

(This article belongs to the Special Issue Advanced Technologies in Biophotonics and Medical Physics)

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15 pages, 3113 KiB

Open AccessArticle

Dark Soliton Dynamics for the Resonant Nonlinear Schrödinger Equation with Third- and Fourth-Order Dispersions

by Weiqian Zhao, Yuan Wang, Ziye Wang and Ying Wang

Photonics 2025, 12(8), 773; https://doi.org/10.3390/photonics12080773 (registering DOI) - 31 Jul 2025

Abstract

Optical solitons have emerged as a highly active research domain in nonlinear fiber optics, driving significant advancements and enabling a wide range of practical applications. This study investigates the dynamics of dark solitons in systems governed by the resonant nonlinear Schrödinger equation (RNLSE). [...] Read more.

Optical solitons have emerged as a highly active research domain in nonlinear fiber optics, driving significant advancements and enabling a wide range of practical applications. This study investigates the dynamics of dark solitons in systems governed by the resonant nonlinear Schrödinger equation (RNLSE). For the RNLSE with third-order (3OD) and fourth-order (4OD) dispersions, the dark soliton solution of the equation in the (1+1)-dimensional case is derived using the F-expansion method, and the analytical study is extended to the (2+1)-dimensional case via the self-similar method. Subsequently, the nonlinear equation incorporating perturbation terms is further studied, with particular attention given to the dark soliton solutions in both one and two dimensions. The soliton dynamics are illustrated through graphical representations to elucidate their propagation characteristics. Finally, modulation instability analysis is conducted to evaluate the stability of the nonlinear system. These theoretical findings provide a solid foundation for experimental investigations of dark solitons within the systems governed by the RNLSE model. Full article

(This article belongs to the Section Optoelectronics and Optical Materials)

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13 pages, 2435 KiB

Open AccessArticle

Preliminary Evaluation of Spherical Over-Refraction Measurement Using a Smartphone

by Rosa Maria Salmeron-Campillo, Gines Martinez-Ros, Jose Angel Diaz-Guirado, Tania Orenes-Nicolas, Mateusz Jaskulski and Norberto Lopez-Gil

Photonics 2025, 12(8), 772; https://doi.org/10.3390/photonics12080772 (registering DOI) - 31 Jul 2025

Abstract

Background: Smartphones offer a promising tool for monitoring refractive error, especially in underserved areas where there is a shortage of eye-care professionals. We propose a novel method for measuring spherical over-refraction using smartphones. Methods: Specific levels of myopia using positive spherical trial lenses, [...] Read more.

Background: Smartphones offer a promising tool for monitoring refractive error, especially in underserved areas where there is a shortage of eye-care professionals. We propose a novel method for measuring spherical over-refraction using smartphones. Methods: Specific levels of myopia using positive spherical trial lenses, ranging from 0.00 D to 1.50 D in 0.25 D increments, were induced in 30 young participants (22 ± 5 years). A comparison was conducted between the induced over-refraction and the measurements obtained using a non-commercial mobile application based on the face–device distance measurement using the front camera while the subject was performing a resolution task. Results: Calibrated mobile app over-refraction results showed that 89.5% of the estimates had an error ≤ 0.25 D, and no errors exceeding 0.50 D. Bland–Altman analysis revealed no significant bias between app and clinical over-refraction, with a mean difference of 0.00 D ± 0.44 D (p = 0.981), indicating high accuracy and precision of the method. Conclusions: The methodology used shows high accuracy and precision in the measurement of the spherical over-refraction with only the use of a smartphone, allowing self-monitorization of potential myopia progression. Full article

(This article belongs to the Special Issue Advances in Optometric and Ophthalmic Technologies: Innovations and Applications)

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18 pages, 4411 KiB

Open AccessArticle

Research on Enhancing Target Recognition Rate Based on Orbital Angular Momentum Spectrum with Assistance of Neural Network

by Guanxu Chen, Hongyang Wang, Hao Yun, Zhanpeng Shi, Zijing Zhang, Chengshuai Cui, Di Wu, Xinran Lyu and Yuan Zhao

Photonics 2025, 12(8), 771; https://doi.org/10.3390/photonics12080771 - 30 Jul 2025

Abstract

In this paper, the single-mode vortex beam is used to illuminate targets of different shapes, and the targets are recognized using machine learning algorithms based on the orbital angular momentum (OAM) spectral information of the echo signal. We innovatively utilize three neural networks—multilayer [...] Read more.

In this paper, the single-mode vortex beam is used to illuminate targets of different shapes, and the targets are recognized using machine learning algorithms based on the orbital angular momentum (OAM) spectral information of the echo signal. We innovatively utilize three neural networks—multilayer perceptron (MLP), convolutional neural network (CNN) and residual neural network (ResNet)—to train extensive echo OAM spectrum data. The trained models can rapidly and accurately classify the OAM spectrum data of different targets’ echo signals. The results show that the residual network (ResNet) performs best under all turbulence intensities and can achieve a high recognition rate when

C_{n}^{2} = 1 \times 10^{- 13} m^{- 2 / 3}

. In addition, even when the target size is

η = 0.3

, the recognition rate of ResNet can reach 97%, while the robustness of MLP and CNN to the target size is lower; the recognition rates are 91.75% and 91%, respectively. However, although the recognition performance of CNN and MLP is slightly lower than that of ResNet, their training time is much lower than that of ResNet, which can achieve a good balance between recognition performance and training time cost. This research has a promising future in the fields of target recognition and intelligent navigation based on multi-dimensional information. Full article

(This article belongs to the Special Issue Advancements in Optics and Laser Measurement)

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14 pages, 1161 KiB

Open AccessArticle

Multipath Interference Impact Due to Fiber Mode Coupling in C+L+S Multiband Transmission Reach

by Luís Cancela and João Pires

Photonics 2025, 12(8), 770; https://doi.org/10.3390/photonics12080770 - 30 Jul 2025

Abstract

Multiband transmission is, nowadays, being implemented worldwide to increase the optical transport network capacity, mainly because it uses the already-installed single-mode fiber (SMF). The G.654E SMF, due to its attributes (e.g., low-loss, and large-effective area in comparison with the standard G.652 SMF), can [...] Read more.

Multiband transmission is, nowadays, being implemented worldwide to increase the optical transport network capacity, mainly because it uses the already-installed single-mode fiber (SMF). The G.654E SMF, due to its attributes (e.g., low-loss, and large-effective area in comparison with the standard G.652 SMF), can also increase network capacity and can also be used for multiband (MB) transmission. Nevertheless, in MB transmission, power mode coupling arises when bands with wavelengths below the cut-off wavelength are used, inducing multipath interference (MPI). This work investigates the impact of the MPI, due to mode coupling from G.654E SMF, in the transmission reach of a C+L+S band transmission system. Our results indicate that for the S-band scenario, the band below the wavelength cut-off, an approximately 25% reach decrease is observed when the MPI/span increases to −26 dB/span, considering quadrature phase-shift keying (QPSK) signals with a 64 GBaud symbol rate. We also concluded that if the L-band were not above the wavelength cut-off, it would be much more affected than the S-band, with an approximately 52% reach decrease due to MPI impact. Full article

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

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14 pages, 814 KiB

Open AccessArticle

Impact of Corneal-Hydration-Induced Changes in Ablation Efficiency During Refractive Surgery

by Samuel Arba Mosquera and Shwetabh Verma

Photonics 2025, 12(8), 769; https://doi.org/10.3390/photonics12080769 - 30 Jul 2025

Abstract

(1) Background: A decrease in corneal hydration during refractive surgery is observed clinically as well as in laboratory settings, but the associated consequences are not yet fully understood. The purpose of this paper is to analyze the impact of the gain of ablation [...] Read more.

(1) Background: A decrease in corneal hydration during refractive surgery is observed clinically as well as in laboratory settings, but the associated consequences are not yet fully understood. The purpose of this paper is to analyze the impact of the gain of ablation efficiency due to hydration changes during cornea refractive surgery. (2) Methods: We developed a simulation model to evaluate the influence of hydration changes on the ablation algorithms used in laser refractive surgery. The model simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model considers corneal hydration, as well as environmental humidity, along with the laser beam characteristics and ablative spot properties for evaluating any hydration changes and their effect on laser refractive surgery. (3) Results: Using pulse lists collected from actual treatments, we simulated the gain of efficiency during the ablation process. Ablation efficiency is increased due to dehydration effects during laser treatments. Longer treatments suffer larger dehydration effects and are more prone to overcorrections due to gain of efficiency than shorter treatments. (4) Conclusions: The improper use of a model that overestimates or underestimates the effects derived from the hydration dynamics during treatment may result in suboptimal refractive corrections. This model may contribute to improving emmetropization and the correction of ocular aberrations with improved laser parameters that can compensate for the changes in ablation efficiency due to hydration changes in the cornea. Full article

(This article belongs to the Special Issue Advances and Applications in Visual Optics)

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12 pages, 1829 KiB

Open AccessArticle

Flexible Color Filter Using Lithium Niobate Metamaterial with Ultrahigh Purity and Brightness Characteristics

by Siqiang Zhao, Daoye Zheng, Yunche Zhu, Shuyan Zou and Yu-Sheng Lin

Photonics 2025, 12(8), 768; https://doi.org/10.3390/photonics12080768 - 30 Jul 2025

Abstract

We propose a simulation-based design for a flexible color filter (FCF) using a lithium niobate metamaterial (LNM) to investigate its color filtering potential. The FCF is composed of three periodically arranged half-ellipse LN arrays on a polydimethylsiloxane (PDMS) substrate, denoted as LNM-1, LNM-2, [...] Read more.

We propose a simulation-based design for a flexible color filter (FCF) using a lithium niobate metamaterial (LNM) to investigate its color filtering potential. The FCF is composed of three periodically arranged half-ellipse LN arrays on a polydimethylsiloxane (PDMS) substrate, denoted as LNM-1, LNM-2, and LNM-3. The electromagnetic responses of the FCF can be controlled by adjusting the periods of the LNMs. Our simulations predict high-quality (Q) factors in transmission spectra, ranging from 100 to 200 for LNM-1, 290 to 360 for LNM-2, and 140 to 300 for LNM-3. When the FCF is exposed to the surrounding environments with different refractive indexes, it exhibits a theoretical figure of merit (FOM) up to 900 RIU⁻¹ and a sensitivity reaching 130 nm/RIU. The electromagnetic field distributions reveal strong confinement within the LNM nanostructures, confirming an efficient light–matter interaction. These results indicate that the proposed LNM-based FCF presents a promising design concept for high-performance color sensing and filtering applications. Full article

(This article belongs to the Special Issue Photonics Metamaterials: Processing and Applications)

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14 pages, 17389 KiB

Open AccessArticle

A Distortion Image Correction Method for Wide-Angle Cameras Based on Track Visual Detection

by Quanxin Liu, Xiang Sun and Yuanyuan Peng

Photonics 2025, 12(8), 767; https://doi.org/10.3390/photonics12080767 - 30 Jul 2025

Abstract

Regarding the distortion correction problem of large field of view wide-angle cameras commonly used in railway visual inspection systems, this paper proposes a novel online calibration method for non-specially made cooperative calibration objects. Based on the radial distortion divisor model, first, the spatial [...] Read more.

Regarding the distortion correction problem of large field of view wide-angle cameras commonly used in railway visual inspection systems, this paper proposes a novel online calibration method for non-specially made cooperative calibration objects. Based on the radial distortion divisor model, first, the spatial coordinates of natural spatial landmark points are constructed according to the known track gauge value between two parallel rails and the spacing value between sleepers. By using the image coordinate relationships corresponding to these spatial coordinates, the coordinates of the distortion center point are solved according to the radial distortion fundamental matrix. Then, a constraint equation is constructed based on the collinear constraint of vanishing points in railway images, and the Levenberg–Marquardt algorithm is used to found the radial distortion coefficients. Moreover, the distortion coefficients and the coordinates of the distortion center are re-optimized according to the least squares method (LSM) between points and the fitted straight line. Finally, based on the above, the distortion correction is carried out for the distorted railway images captured by the camera. The experimental results show that the above method can efficiently and accurately perform online distortion correction for large field of view wide-angle cameras used in railway inspection without the participation of specially made cooperative calibration objects. The whole method is simple and easy to implement, with high correction accuracy, and is suitable for the rapid distortion correction of camera images in railway online visual inspection. Full article

(This article belongs to the Section Optoelectronics and Optical Materials)

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14 pages, 3968 KiB

Open AccessArticle

Investigating the Coherence Between Motor Cortex During Rhythmic Finger Tapping Using OPM-MEG

by Hao Lu, Yong Li, Yang Gao, Ying Liu and Xiaolin Ning

Photonics 2025, 12(8), 766; https://doi.org/10.3390/photonics12080766 - 29 Jul 2025

Abstract

Optically pumped magnetometer OPM-MEG has the potential to replace the traditional low-temperature superconducting quantum interference device SQUID-MEG. Coherence analysis can be used to evaluate the functional connectivity and reflect the information transfer process between brain regions. In this paper, a finger tapping movement [...] Read more.

Optically pumped magnetometer OPM-MEG has the potential to replace the traditional low-temperature superconducting quantum interference device SQUID-MEG. Coherence analysis can be used to evaluate the functional connectivity and reflect the information transfer process between brain regions. In this paper, a finger tapping movement paradigm based on auditory cues was used to measure the functional signals of the brain using OPM-MEG, and the coherence between the primary motor cortex (M1) and the primary motor area (PM) was calculated and analyzed. The results demonstrated that the coherence of the three frequency bands of Alpha (8–13 Hz), Beta (13–30 Hz), and low Gamma (30–45 Hz) and the selected reference signal showed roughly the same position, the coherence strength and coherence range decreased from Alpha to low Gamma, and the coherence coefficient changed with time. It was inferred that the change in coherence indicated different neural patterns in the contralateral motor cortex, and these neural patterns also changed with time, thus reflecting the changes in the connection between different functional areas in the time-frequency domain. In summary, OPM-MEG has the ability to measure brain coherence during finger movements and can characterize connectivity between brain regions. Full article

(This article belongs to the Special Issue Advancements in Optical Techniques for Enhancing the Sensitivity and Precision of Atomic Magnetometers)

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11 pages, 1303 KiB

Open AccessArticle

Effect of Wavefront Autorefractor Design on Cycloplegic Refraction in Young Hyperopes: Monocular vs. Binocular

by Gonzalo Carracedo, Carlos Carpena-Torres, Cristina Pastrana, Maria Rodríguez-Lafora, Ana Privado-Aroco, María Serramito and Laura Batres

Photonics 2025, 12(8), 765; https://doi.org/10.3390/photonics12080765 - 29 Jul 2025

Abstract

Objectives: To compare the objective refraction of young hyperopes obtained by two wavefront autorefractors with identical measurement principles but different optical designs: a monocular closed-field (VX 120) and a binocular open-field (Eye Refract), both developed by the same manufacturer (Visionix; Pont-de-l’Arche, France). Methods: [...] Read more.

Objectives: To compare the objective refraction of young hyperopes obtained by two wavefront autorefractors with identical measurement principles but different optical designs: a monocular closed-field (VX 120) and a binocular open-field (Eye Refract), both developed by the same manufacturer (Visionix; Pont-de-l’Arche, France). Methods: A randomized, cross-sectional study was carried out with 37 hyperopic participants (18.2 ± 7.8 years; range 8 to 31 years). Each participant underwent two measurement sessions (one with and one without cycloplegia), during which three measurements were taken per autorefractor (monocular and binocular). Refractive variables (M, J0, and J45) were analyzed in one randomly selected eye. Results: The spherical equivalent (M) showed significant differences between autorefractors under noncycloplegic and cycloplegic conditions (p < 0.001). Without cycloplegia, the binocular autorefractor measured +0.45 (+1.49, −0.58) D more hyperopia than the monocular device. Under cycloplegia, this difference decreased to +0.26 D (+0.99, −0.48) D. Both autorefractors provided higher hyperopia with cycloplegia, with differences inversely correlated with age (r = −0.4; p < 0.05). Conclusions: Whenever possible, refraction in young hyperopes should be measured under cycloplegic conditions using a binocular open-field autorefractor to promote greater accommodative relaxation and ensure more reliable hyperopia measurements in both clinical practice and research. Full article

(This article belongs to the Special Issue Novel Techniques and Applications of Ophthalmic Optics)

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22 pages, 5896 KiB

Open AccessArticle

Point Cloud Generation Method Based on Dual-Prism Scanning with Multi-Parameter Optimization

by Yuanfeng Zhao, Zhen Zheng and Hong Chen

Photonics 2025, 12(8), 764; https://doi.org/10.3390/photonics12080764 - 29 Jul 2025

Abstract

This study addresses two critical challenges in biprism-based laser scanning systems: the lack of a comprehensive mathematical framework linking prism parameters to scanning performance, and unresolved theoretical gaps regarding parameter effects on point cloud quality. We propose a multi-parameter optimization method for point [...] Read more.

This study addresses two critical challenges in biprism-based laser scanning systems: the lack of a comprehensive mathematical framework linking prism parameters to scanning performance, and unresolved theoretical gaps regarding parameter effects on point cloud quality. We propose a multi-parameter optimization method for point cloud generation using dual-prism scanning. By establishing a beam pointing mathematical model, we systematically analyze how prism wedge angles, refractive indices, rotation speed ratios, and placement configurations influence scanning performance, revealing their coupled effects on deflection angles, azimuth control, and coverage. The non-paraxial ray tracing method combined with the Möller–Trumbore algorithm enables efficient point cloud simulation. Experimental results demonstrate that our optimized parameters significantly enhance point cloud density, uniformity, and target feature integrity while overcoming limitations of traditional database construction methods. This work provides both theoretical foundations and practical solutions for high-precision 3D reconstruction in high-speed rendezvous scenarios such as missile-borne laser fuzes, offering advantages in cost-effectiveness and operational reliability. Full article

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29 pages, 4763 KiB

Open AccessReview

Quantum-Empowered Fiber Sensing Metrology

by Xiaojie Zuo, Zhangguan Tang, Boyao Li, Xiaoyong Chen and Jinghua Sun

Photonics 2025, 12(8), 763; https://doi.org/10.3390/photonics12080763 - 29 Jul 2025

Abstract

Quantum sensing leverages quantum resources to enable ultra-precise measurements beyond classical limits, driving transformative advancements in metrology. Optical fiber quantum sensing, integrating optical fiber sensing with quantum technologies, enhances measurement precision and sensitivity from multiple perspectives, such as exploring high-sensitivity optical fiber sensing [...] Read more.

Quantum sensing leverages quantum resources to enable ultra-precise measurements beyond classical limits, driving transformative advancements in metrology. Optical fiber quantum sensing, integrating optical fiber sensing with quantum technologies, enhances measurement precision and sensitivity from multiple perspectives, such as exploring high-sensitivity optical fiber sensing installations and generating high-quality optical fiber quantum states. Following decades of comprehensive investigations and remarkable advances in optical fiber quantum sensing technology, this review systematically examines research achievements in this field through two complementary perspectives: one is the basic principle of generating optical fiber quantum states and their applications in sensing and the other is optical fiber quantum interferometers and their applications in sensing. Finally, examine current opportunities and challenges as well as the future development of optical fiber quantum sensing. Full article

(This article belongs to the Special Issue Quantum High Precision Measurement)

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23 pages, 14391 KiB

Open AccessArticle

Design of All-Optical Ternary Inverter and Clocked SR Flip-Flop Based on Polarization Conversion and Rotation in Micro-Ring Resonator

by Madan Pal Singh, Jayanta Kumar Rakshit, Kyriakos E. Zoiros and Manjur Hossain

Photonics 2025, 12(8), 762; https://doi.org/10.3390/photonics12080762 - 29 Jul 2025

Abstract

In the present study, a polarization rotation switch (PRS)-based all-optical ternary inverter circuit and ternary clocked SR flip-flop (TCSR) are proposed and discussed. The present scheme is designed by the polarization rotation of light in a waveguide coupled with a micro-ring resonator (MRR). [...] Read more.

In the present study, a polarization rotation switch (PRS)-based all-optical ternary inverter circuit and ternary clocked SR flip-flop (TCSR) are proposed and discussed. The present scheme is designed by the polarization rotation of light in a waveguide coupled with a micro-ring resonator (MRR). The proposed scheme uses linear polarization-encoded light. Here, the ternary (radix = 3) logical states are expressed by the different polarized light. PRS-MRR explores the polarization-encoded methodology, which depends on polarization conversion from one state to another. All-optical ultrafast switching technology is employed to design the ternary NAND gate. We develop the ternary clocked SR flip-flop by employing the NAND gate; it produces a greater number of possible outputs as compared to the binary logic clocked SR flip-flop circuit. The performance of the proposed design is measured by the Jones parameter and Stokes parameter. The results of the polarization rotation-based ternary inverter and clocked SR flip-flop are realized using a pump–probe structure in the MRR. The numerical simulation results are confirmed by the well-known Jones vector (azimuth angle and ellipticity angle) and Stokes parameter (S₁, S₂, S₃) using Ansys Lumerical Interconnect simulation software. Full article

(This article belongs to the Special Issue Advancements in Optical and Acoustic Signal Processing)

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6 pages, 193 KiB

Open AccessCorrection

Correction: Zhou et al. Research Progress on Modulation Format Recognition Technology for Visible Light Communication. Photonics 2025, 12, 512

by Shengbang Zhou, Weichang Du, Chuanqi Li, Shutian Liu and Ruiqi Li

Photonics 2025, 12(8), 761; https://doi.org/10.3390/photonics12080761 - 29 Jul 2025

Abstract

Text Corrections [...] Full article

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