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7 pages, 837 KiB

Open AccessCommunication

Dielectric Catenary Metasurface for Broadband and High-Efficiency Anomalous Reflection

by Xinjian Lu, Wenxin Li, Guiyong Chen, Bo Liu, Xin Xie, Zhongming Zang, Kuo Hai and Zhu Li

Photonics 2025, 12(7), 684; https://doi.org/10.3390/photonics12070684 - 7 Jul 2025

Viewed by 194

Abstract

This paper proposes a broadband and high-efficiency anomalous reflection device based on a dielectric catenary metasurface, addressing the bottleneck problems of low efficiency and narrow bandwidth in traditional discrete metasurfaces. By designing a silicon-based equal-strength catenary structure, the efficient control of circularly polarized [...] Read more.

This paper proposes a broadband and high-efficiency anomalous reflection device based on a dielectric catenary metasurface, addressing the bottleneck problems of low efficiency and narrow bandwidth in traditional discrete metasurfaces. By designing a silicon-based equal-strength catenary structure, the efficient control of circularly polarized light beams within a wide angular range in the infrared band has been achieved. Simulation results show that the designed metasurface exhibits excellent beam steering performance when the deflection angle reaches 65°. Furthermore, to characterize the diffraction efficiency of the metasurface within a large angular range, the results indicate that under oblique incidence (0–60°), the diffraction efficiency of the ±1st order exceeds 80%, and the undesired higher-order diffractions are significantly suppressed. This ultrahigh working efficiency is attributed to the nearly perfect polarization conversion and continuous phase profile of the dielectric catenary structure. By combining catenary optics with the low-loss properties of the dielectric material, this design provides a new solution for the design of efficient, broadband, and wide-angle planar optical devices. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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12 pages, 1285 KiB

Open AccessEditor’s ChoiceArticle

Performance Analysis of Space-to-Ground Downlink for Polarization Shift Keying Optical Communications with a Gaussian-Schell Model Beam

by Jiajie Wu, Yuwei Zhang, Qingyan Li, Siyuan Yu and Jianjie Yu

Photonics 2025, 12(7), 643; https://doi.org/10.3390/photonics12070643 - 24 Jun 2025

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Abstract

Free-space optical communication has emerged as a pivotal technology for space-to-ground downlinks; however, signal degradation caused by atmospheric turbulence continues to pose a significant challenge. In this study, a model for the polarization transmission characteristics of a Gaussian-Schell model (GSM) beam in downlink [...] Read more.

Free-space optical communication has emerged as a pivotal technology for space-to-ground downlinks; however, signal degradation caused by atmospheric turbulence continues to pose a significant challenge. In this study, a model for the polarization transmission characteristics of a Gaussian-Schell model (GSM) beam in downlink was established, and conditions sufficient for maintaining the polarization transmission characteristics were derived. The impact of the source spatial coherence on the performance of optical communication systems using circular polarization shift keying (CPolSK) modulation was investigated. Additionally, models for the probability density distribution and scintillation index of the optical intensity under atmospheric turbulence were developed along with a bit error rate model for the optical communication system. The effects of the laser spatial coherence on these models were also analyzed. The results indicate that the optimal performance in the turbulent downlink is achieved with fully coherent light, where the GSM-beam-based CPolSK-modulated system demonstrates a reduction of 1.51 dB in the required power compared to that of an on–off keying system. The implications of this study suggest that optimizing spatial coherence could significantly enhance the reliability of space-to-ground communication systems under atmospheric disturbances. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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10 pages, 977 KiB

Open AccessCommunication

Tailorable Brillouin Light Scattering in Air-Slit Suspended Waveguide

by Yanzhao Wang, Hongrun Ren and Yunjie Teng

Photonics 2025, 12(6), 586; https://doi.org/10.3390/photonics12060586 - 9 Jun 2025

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Abstract

Silicon-based optical waveguides exhibit high Brillouin gain, enabling the realization of Brillouin lasers directly on silicon substrates. These lasers hold significant promise for applications such as tunable-frequency laser emission, ultrafast pulse generation via mode-locking techniques, and other advanced photonic functionalities. However, a key [...] Read more.

Silicon-based optical waveguides exhibit high Brillouin gain, enabling the realization of Brillouin lasers directly on silicon substrates. These lasers hold significant promise for applications such as tunable-frequency laser emission, ultrafast pulse generation via mode-locking techniques, and other advanced photonic functionalities. However, a key challenge in silicon-based Brillouin lasers is the requirement for long waveguide lengths to achieve sufficient optical feedback and reach the lasing threshold. This study proposes a novel floating waveguide architecture designed to significantly enhance the Brillouin gain in silicon-based systems. Furthermore, we introduce a breakthrough method for achieving wide-range phonon frequency tunability, enabling precise control over stimulated Brillouin scattering (SBS) dynamics. By strategically engineering the waveguide geometry (shape and dimensions), we demonstrate a tunable SBS phonon laser, offering a versatile platform for on-chip applications. Additionally, the proposed waveguide system features adjustable operating frequencies, unlocking new opportunities for compact Brillouin devices and integrated microwave photonic signal sources. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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13 pages, 2693 KiB

Open AccessEditor’s ChoiceCommunication

Prediction of Aluminum Alloy Surface Roughness Through Nanosecond Pulse Laser Assisted by Continuous Laser Paint Removal

by Jingyi Li, Rongfan Liang, Han Li, Junjie Liu and Jingdong Sun

Photonics 2025, 12(6), 575; https://doi.org/10.3390/photonics12060575 - 6 Jun 2025

Viewed by 357

Abstract

Reducing surface roughness can enhance the mechanical properties of processed materials. The variation law of the aluminum alloy surface roughness induced by continuous-nanosecond combined laser (CL) with different continuous laser power densities and laser delay is investigated experimentally. A back propagation neural network [...] Read more.

Reducing surface roughness can enhance the mechanical properties of processed materials. The variation law of the aluminum alloy surface roughness induced by continuous-nanosecond combined laser (CL) with different continuous laser power densities and laser delay is investigated experimentally. A back propagation neural network (BPNN) coupled with a sparrow search algorithm (SSA) is employed to predict surface roughness. The nanosecond laser energy density, continuous laser power density and laser delay are input parameters, while the surface roughness is output parameter. The lowest surface roughness is achieved with completely paint film removed by the CL while the nanosecond laser energy density is 1.99 J/cm², the continuous laser power density is 2118 W/cm² and the laser delay is 1 ms. Compared to the original target and the target irradiated by nanosecond pulse laser (ns laser), the reductions in the surface roughness are 20.62% and 12.00%, respectively. The SSA-BPNN model demonstrates high prediction accuracy, with a correlation coefficient (R²) of 0.98628, root mean square error (RMSE) of 0.024, mean absolute error (MAE) of 0.020 and mean absolute percentage error (MAPE) of 1.30% on the test set. These results indicate that the SSA-BPNN demonstrates higher-precision surface roughness prediction with limited experimental data than BPNN. Furthermore, the findings confirm that the CL can effectively reduce surface roughness. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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8 pages, 1537 KiB

Open AccessCommunication

Ag-Grid and Ag-Nanowires Hybrid Transparent Electrodes to Improve Performance of Flexible Organic Light-Emitting Devices

by Hao Yang, Yangang Bi, Shirong Wang, Congfang Wang, Haipeng Wang, Gaoda Ye and Jing Feng

Photonics 2025, 12(3), 272; https://doi.org/10.3390/photonics12030272 - 16 Mar 2025

Cited by 1 | Viewed by 945

Abstract

Flexible transparent conductive electrodes, with high optical transmittance, electrical conductivity, and flexible stability, still challenge the commercial development of flexible organic light-emitting devices (OLEDs). In this work, a novel Ag-grid and Ag-nanowire (Ag-grid/AgNW) hybrid transparent conductive film was proposed with extraordinary optoelectronic and [...] Read more.

Flexible transparent conductive electrodes, with high optical transmittance, electrical conductivity, and flexible stability, still challenge the commercial development of flexible organic light-emitting devices (OLEDs). In this work, a novel Ag-grid and Ag-nanowire (Ag-grid/AgNW) hybrid transparent conductive film was proposed with extraordinary optoelectronic and mechanical performance. The hybrid film exhibited a low resistivity of 9 Ω/sq and a high transparency of 67.9% at the wavelength of 550 nm, as well as outstanding mechanical robustness by surviving over 5000 bending cycles. By applying the proposed Ag-grid/AgNW hybrid electrode in flexible OLEDs, the electroluminescence performance, flexibility, and mechanical reliability of the devices were significantly improved. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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10 pages, 3490 KiB

Open AccessCommunication

Laser Linewidth Measurement Using an FPGA-Based Delay Self-Homodyne System

by Fanqi Bu, Zhongan Zhao, Longfei Li, Cunwei Zhang, Tie Li, Yaoyao Qi, Jie Ding, Bingzheng Yan, Chen Zhao, Yulei Wang, Zhiwei Lu, Yu Ding and Zhenxu Bai

Photonics 2025, 12(3), 203; https://doi.org/10.3390/photonics12030203 - 26 Feb 2025

Viewed by 750

Abstract

Narrow-linewidth lasers play a crucial role in nonlinear optics, atomic physics, optical metrology, and high-speed coherent optical communications. Precise linewidth measurement is essential for assessing laser noise characteristics; however, conventional methods are often bulky, costly, and unsuitable for integrated applications. This paper presents [...] Read more.

Narrow-linewidth lasers play a crucial role in nonlinear optics, atomic physics, optical metrology, and high-speed coherent optical communications. Precise linewidth measurement is essential for assessing laser noise characteristics; however, conventional methods are often bulky, costly, and unsuitable for integrated applications. This paper presents a compact and cost-effective delay self-homodyne system for laser linewidth measurement, leveraging a field-programmable gate array (FPGA)-based data acquisition circuit. By employing fast Fourier transform (FFT) analysis, the system achieves high-precision linewidth measurement in the kHz range. Additionally, by optimizing the fiber length, the system effectively suppresses low-frequency and 1/f noise, providing an integrated and efficient solution for advanced laser characterization with enhanced performance and reduced cost. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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Review

Jump to: Research

19 pages, 2372 KiB

Open AccessReview

Frontier Advances and Challenges of High-Power Thulium-Doped Fiber Lasers in Minimally Invasive Medicine

by Wen-Yue Xu, Gong Wang, Yun-Fei Li, Yu Yu, Yulei Wang and Zhiwei Lu

Photonics 2025, 12(6), 614; https://doi.org/10.3390/photonics12060614 - 16 Jun 2025

Viewed by 611

Abstract

Lasers are increasingly used in the biomedical field because of their concentrated energy, good stability, ease of use, and other advantages, promoting the development of precision medicine to a higher level. Medical laser equipment has transformed from a single therapeutic tool in an [...] Read more.

Lasers are increasingly used in the biomedical field because of their concentrated energy, good stability, ease of use, and other advantages, promoting the development of precision medicine to a higher level. Medical laser equipment has transformed from a single therapeutic tool in an intelligent and precise diagnostic system. Existing clinical laser equipment has significant technical bottlenecks regarding soft-tissue ablation precision and multimodal diagnostic compatibility, which seriously restricts its clinical application. High-power thulium-doped fiber lasers with operating wavelengths of 1.9–2.1 μm provide a revolutionary solution for minimally invasive surgery due to their high compatibility with the absorption peaks of water molecules in biological tissues. This study reviews recent advances in high-power thulium-doped fiber lasers for minimally invasive therapies in the biomedical field. Breakthrough results in four major clinical application scenarios, namely, urological lithotripsy, tumor precision ablation, disfiguring dermatological treatment, and minimally invasive endovenous laser ablation, are also summarized. By systematically evaluating its potential for multimodal diagnostic and therapeutic applications and thoroughly exploring the technical challenges and strategies for clinical transformation, we aim to provide a theoretical basis and practical guidance for the clinical transformation and industrialization of new-generation medical laser technology. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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24 pages, 3261 KiB

Open AccessReview

Some Insights on Kerr Lensing Effects

by Kamel Aït-Ameur and Abdelkrim Hasnaoui

Photonics 2025, 12(6), 596; https://doi.org/10.3390/photonics12060596 - 10 Jun 2025

Viewed by 1469

Abstract

The research on high-order transverse modes in lasers was largely abandoned a few years after the invention of the laser in 1960. The main reason for this was that high-order beams are more divergent and less bright than the Gaussian beam. In the [...] Read more.

The research on high-order transverse modes in lasers was largely abandoned a few years after the invention of the laser in 1960. The main reason for this was that high-order beams are more divergent and less bright than the Gaussian beam. In the present paper, we showed that the behaviour of

L G_{p 0}

beams faced to the optical Kerr effect (OKE) varies considerably depending on the mode order (p = 0 or

p \geq 1

). We focused our attention on the properties of

L G_{00}

and

L G_{10}

beams when subject to OKE, and we found that the

L G_{10}

beam keeps its focusability much better than the

L G_{00}

beam. This property has at least two applications concerning first the conception of high-intensity laser chains not based on a Gaussian beam but on an

L G_{10}

beam and second, the use of an

L G_{10}

beam instead of the usual Gaussian beam which can reduce drastically the protection of optical limiters based on OKE; this constitutes a counter-measure against such limiters. Full article

(This article belongs to the Special Issue Advanced Methods in Exploring Light–Matter Interactions and Nonlinear Effects Optics Applications)

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