-
Experimental Observation of Surface Wave States at the Gold–Silver Interface
-
A Miniature Liquid Flowmeter Using All-Fiber Fabry–Perot Cavity for Real-Time Measurement
-
Penrose Scattering in Quantum Vacuum
-
Spatially Resolved, Real-Time Polarization Measurement Using Artificial Birefringent Metallic Elements
Journal Description
Photonics
Photonics
is an international, scientific, peer-reviewed, open access journal on the science and technology of optics and photonics, published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
- Journal Rank: JCR - Q2 (Optics)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15.5 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Companion journal: Optics.
Impact Factor:
2.1 (2023);
5-Year Impact Factor:
2.1 (2023)
Latest Articles
Lights off the Image: Highlight Suppression for Single Texture-Rich Images in Optical Inspection Based on Wavelet Transform and Fusion Strategy
Photonics 2024, 11(7), 623; https://doi.org/10.3390/photonics11070623 (registering DOI) - 28 Jun 2024
Abstract
A wavelet-transform-based highlight suppression method is presented, aiming at suppressing the highlights of single image with complex texture. The strategy involves the rough extraction of specular information, followed by extracting the high-frequency information in specular information based on multi-level wavelet transform to enhance
[...] Read more.
A wavelet-transform-based highlight suppression method is presented, aiming at suppressing the highlights of single image with complex texture. The strategy involves the rough extraction of specular information, followed by extracting the high-frequency information in specular information based on multi-level wavelet transform to enhance the texture information in the original images by fusion strategy, and fusing with the same-level specular information to achieve the highlight suppression image. The experimental results demonstrate that the proposed method effectively removed large-area highlights while preserving texture details, and demonstrated the authenticity of the highlight estimation and the ‘lights off’ effect in the highlight-suppressed images. Overall, the method offers a feasibility for addressing the challenges of highlight suppression for visual detection image with rich texture and large-area highlights.
Full article
(This article belongs to the Special Issue New Perspectives in Optical Design)
►
Show Figures
Open AccessReview
Advances in Femtosecond Coherent Anti-Stokes Raman Scattering for Thermometry
by
Kaiyuan Song, Mingze Xia, Sheng Yun, Yuan Zhang, Sheng Zhang, Hui Ge, Yanyan Deng, Meng Liu, Wei Wang, Longfei Zhao, Yulei Wang, Zhiwei Lv and Yuanqin Xia
Photonics 2024, 11(7), 622; https://doi.org/10.3390/photonics11070622 (registering DOI) - 28 Jun 2024
Abstract
The combustion process is complex and harsh, and the supersonic combustion flow field is also characterized by short duration and supersonic speed, which makes the real-time diagnostic technology for the transient environment extremely demanding. It is of great significance to realize high time-resolved
[...] Read more.
The combustion process is complex and harsh, and the supersonic combustion flow field is also characterized by short duration and supersonic speed, which makes the real-time diagnostic technology for the transient environment extremely demanding. It is of great significance to realize high time-resolved accurate measurement of temperature, component concentration, and other parametric information of the combustion field to study the transient chemical reaction dynamics of the combustion field. Femtosecond CARS spectroscopy can effectively avoid the collision effect between particles in the measurement process and reduce the influence of the non-resonant background to improve the measurement accuracy and realize the time-resolved measurement on a millisecond scale. This paper introduces the development history of femtosecond CARS spectroscopy, points out its advantages and disadvantages, and looks forward to the future development trend to carry out high time-resolved measurements, establish a database of temperature changes in various complex combustion fields, and provide support for the study of engine mechanisms.
Full article
(This article belongs to the Special Issue Emerging Topics in High-Power Laser and Light–Matter Interactions)
Open AccessArticle
Simplified 1.5 μm Distributed Feedback Semiconductor Laser (DFB-LD) Frequency Stabilization System Based on Gas Absorption Chamber
by
Ju Wang, Ye Gao, Jinlong Yu, Ziheng Cai, Hao Luo and Chuang Ma
Photonics 2024, 11(7), 621; https://doi.org/10.3390/photonics11070621 (registering DOI) - 28 Jun 2024
Abstract
The classical 1.5 m band frequency-stabilized laser using acetylene gas saturated absorption can achieve high frequency stability and reproducibility, but its system design is complex and bulky. For some practical applications, a simple, compact system containing anti-interference abilities is preferred. In this
[...] Read more.
The classical 1.5 m band frequency-stabilized laser using acetylene gas saturated absorption can achieve high frequency stability and reproducibility, but its system design is complex and bulky. For some practical applications, a simple, compact system containing anti-interference abilities is preferred. In this study, a low-cost and simple-structured 1.5 m frequency-stabilized laser is constructed using digital control methods, wavelength modulation technology, and acetylene gas absorption. The fiber input and output optical devices of the system significantly simplify the optical path and reduce the volume of the system. The error signal is obtained by the first-order differential method, and a combination of the high-speed comparator circuit and the microcontroller unit (MCU) is used to detect the error signal. Through the feedback control method of coarse temperature adjustment and fine current adjustment, the second-level frequency stability of the laser is stabilized within 100 kHz, that is, the frequency stability reaches 10 . The designed system achieved continuous and stable operation for more than 6 h, and the long-term frequency stability reached 10 .
Full article
(This article belongs to the Special Issue Laser Technology and Applications)
►▼
Show Figures
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g001-550.jpg?1719583180)
Figure 1
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g003-550.jpg?1719583181)
Figure 3
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g004-550.jpg?1719583183)
Figure 4
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g005-550.jpg?1719583183)
Figure 5
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g006-550.jpg?1719583184)
Figure 6
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g007-550.jpg?1719583185)
Figure 7
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g008-550.jpg?1719583186)
Figure 8
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g009-550.jpg?1719583187)
Figure 9
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g010-550.jpg?1719583187)
Figure 10
![](https://pub.mdpi-res.com/photonics/photonics-11-00621/article_deploy/html/images/photonics-11-00621-g011-550.jpg?1719583188)
Figure 11
Open AccessCommunication
Polarization-Dependent Formation of Extremely Compressed Femtosecond Wave Packets and Supercontinuum Generation in Fused Silica
by
Ilia Geints and Olga Kosareva
Photonics 2024, 11(7), 620; https://doi.org/10.3390/photonics11070620 (registering DOI) - 28 Jun 2024
Abstract
Previous studies of formation of extremely compressed wave packets during femtosecond filamentation in the region of anomalous group velocity dispersion in solid dielectrics mostly considered the case of linearly polarized laser pulses. However, recent results suggest potential applications of polarization state manipulation for
[...] Read more.
Previous studies of formation of extremely compressed wave packets during femtosecond filamentation in the region of anomalous group velocity dispersion in solid dielectrics mostly considered the case of linearly polarized laser pulses. However, recent results suggest potential applications of polarization state manipulation for ultrafast laser writing of optical structures in bulk solid-state media. In the present work, evolution of radiation polarization parameters during formation of such extreme wave packets at the pump wavelength of 1900 nm in fused silica is studied numerically on the basis of the carrier-resolved unidirectional pulse propagation equation (UPPE). It was revealed that initial close-to-circular polarization leads to higher intensity of the anti-Stokes wing in the spectrum of the generated supercontinuum. Numerical simulations indicate a complex, space–time variant polarization state, and the resulting spatiotemporal electric field distribution exhibits a strong dependence on the initial polarization of the femtosecond pulse. At the same time, electric field polarization tends to linear one in the region with the highest field strength regardless of the initial parameters. The origin of this behavior is attributed to the properties of the supercontinuum components generation during filament-induced plasma formation.
Full article
(This article belongs to the Special Issue Ultrafast Intense Laser Filamentation and Beyond)
Open AccessArticle
High–Speed Laser Modulation for Low–Noise Micro–Cantilever Array Deflection Measurement
by
Weiwei Xue, Yong Su and Qingchuan Zhang
Photonics 2024, 11(7), 619; https://doi.org/10.3390/photonics11070619 (registering DOI) - 28 Jun 2024
Abstract
In this paper, an innovative approach is introduced to address the noise issues associated with micro–cantilever array deflection measurement systems employing multiple lasers. Conventional systems are affected by laser mode hopping during switching, resulting in wavelength instability and beam spot fluctuations that take
[...] Read more.
In this paper, an innovative approach is introduced to address the noise issues associated with micro–cantilever array deflection measurement systems employing multiple lasers. Conventional systems are affected by laser mode hopping during switching, resulting in wavelength instability and beam spot fluctuations that take several hundred milliseconds to stabilize. To mitigate these limitations, a high–speed laser modulation technique is utilized, leveraging the averaging effect over multiple modulation cycles within the sampling window. By driving the lasers with a high–frequency carrier signal, a low–noise and stable output suitable for micro–cantilever beam deflection measurement is achieved. The effectiveness of this approach is demonstrated by simultaneously modulating the lasers and rapidly observing the spectral and centroid variations during high–speed switching using a custom–built high–speed spectrometer. The centroid fluctuations are also analyzed under different modulation frequencies. The experimental results confirm that the high–speed modulation method can reduce the standard deviation of beam spot fluctuations by more than 90%, leading to significant improvements in noise reduction compared to traditional laser switching methods. The proposed high–speed laser modulation approach offers a promising solution for enhancing the precision and stability of multi–laser micro–cantilever array deflection measurement systems.
Full article
(This article belongs to the Special Issue Recent Advances in 3D Optical Measurement)
Open AccessArticle
Temperature-Dependent Localized Surface Plasmon Resonances of Noble Nanoparticles Covered with Polymers
by
Dimitrios Ntemogiannis, Maria Tsarmpopoulou, Constantinos Moularas, Yiannis Deligiannakis, Alkeos Stamatelatos, Dionysios M. Maratos, Nikolaos G. Ploumis, Vagelis Karoutsos, Spyridon Grammatikopoulos, Mihail Sigalas and Panagiotis Poulopoulos
Photonics 2024, 11(7), 618; https://doi.org/10.3390/photonics11070618 (registering DOI) - 28 Jun 2024
Abstract
Self-assembled gold and silver nanoparticles were fabricated in medium vacuum conditions on Corning glass substrates by means of DC magnetron sputtering. The samples were deposited either at 420 °C or 440 °C, or they were initially deposited at room temperature followed by post
[...] Read more.
Self-assembled gold and silver nanoparticles were fabricated in medium vacuum conditions on Corning glass substrates by means of DC magnetron sputtering. The samples were deposited either at 420 °C or 440 °C, or they were initially deposited at room temperature followed by post annealing. Subsequently, they were covered with three different polymers, namely Polystyrene-block-polybutadiene-blockpolystyrene (PS-b-PBD-b-PS), Polystyrene-co-methyl methacrylate (PS-co-PMMA) and Polystyreneblock-polyisoprene-block-polystyrene (PS-b-PI-b-PS), using spin coating. Localized surface plasmon resonances were recorded in the temperature range of −25 °C–100 °C. We show that the resonance position changes systematically as a function of temperature. Theoretical calculations carried out via the Rigorous Coupled Wave Analysis support the experimental results. Based on these findings, the investigated materials demonstrate potential as components for the development of temperature sensors.
Full article
(This article belongs to the Special Issue Plasmon-Enhanced Photon Emission in Nanostructures)
Open AccessArticle
A CMOS Inverter-Based Active Feedback Transimpedance Amplifier
by
Somi Park, Sunkyung Lee, Bobin Seo, Yejin Choi, Yunji Song, Yeojin Chon, Shinhae Choi and Sung-Min Park
Photonics 2024, 11(7), 617; https://doi.org/10.3390/photonics11070617 (registering DOI) - 28 Jun 2024
Abstract
This paper presents an inverter-based active feedback transimpedance amplifier (IAF-TIA), in which an active feedback is applied to a voltage-mode inverter-based TIA, and therefore, the controlled positive regeneration process enables the proposed IAF-TIA to achieve the limiting operations for input currents greater than
[...] Read more.
This paper presents an inverter-based active feedback transimpedance amplifier (IAF-TIA), in which an active feedback is applied to a voltage-mode inverter-based TIA, and therefore, the controlled positive regeneration process enables the proposed IAF-TIA to achieve the limiting operations for input currents greater than 100 μApp. However, the active inverter feedback mechanism might be prone to instability, hence mandating a very careful optimization of the loop gain. For this purpose, a diode-connected NMOS transistor is employed as a switch in the feedback path with its gate connected to the input, which helps not only to mitigate the corresponding issue but also to accommodate large input currents up to 1.5 mApp. The proposed IAF-TIA implemented in a standard 180 nm CMOS process demonstrates a 70.5 dBΩ transimpedance gain, 1.21 GHz bandwidth, 4.3 noise current spectral density, 63.5 dB input dynamic range, and 23.6 mW power dissipation from a single 1.8 V supply. The chip core occupies an area of 180 × 50 μm2, including an on-chip P+/N-well/Deep N-well avalanche photodiode as an optical detector.
Full article
(This article belongs to the Section Optoelectronics and Optical Materials)
Open AccessArticle
Impact of Optical-to-Electrical Conversion on the Design of an End-to-End Learning RGB-LED-Based Visible Light Communication System
by
Jose Martin Luna-Rivera, Jose Rabadan, Julio Rufo, Carlos A. Gutierrez, Victor Guerra and Rafael Perez-Jimenez
Photonics 2024, 11(7), 616; https://doi.org/10.3390/photonics11070616 (registering DOI) - 28 Jun 2024
Abstract
Visible Light Communication (VLC) is emerging as a promising technology to meet the demands of fifth-generation (5G) networks and the Internet of Things (IoT). This study introduces a novel RGB-LED-based VLC system design that leverages autoencoders, addressing the often overlooked impact of optical-to-electrical
[...] Read more.
Visible Light Communication (VLC) is emerging as a promising technology to meet the demands of fifth-generation (5G) networks and the Internet of Things (IoT). This study introduces a novel RGB-LED-based VLC system design that leverages autoencoders, addressing the often overlooked impact of optical-to-electrical (O/E) conversion efficiency. Unlike traditional methods, our autoencoder-based system not only improves communication performance but also mitigates the negative effects of O/E conversion. Through comprehensive simulations, we show that the proposed autoencoder structure enhances system robustness, achieving superior performance compared to traditional VLC systems. By quantitatively assessing the impact of O/E conversion—a critical aspect previously overlooked in the literature—our work bridges a crucial gap in VLC research. This contribution not only advances the understanding of VLC systems but also provides a strong foundation for future enhancements in 5G and IoT connectivity.
Full article
(This article belongs to the Special Issue Machine Learning Applied to Optical Communication Systems)
Open AccessArticle
Single Trench Fiber-Enabled High-Power Fiber Laser
by
Yi An, Fengchang Li, Huan Yang, Xiao Chen, Liangjin Huang, Zhiping Yan, Min Jiang, Baolai Yang, Peng Wang, Zhiyong Pan, Zongfu Jiang and Pu Zhou
Photonics 2024, 11(7), 615; https://doi.org/10.3390/photonics11070615 (registering DOI) - 28 Jun 2024
Abstract
As a novel design of large-mode-area fiber, the single trench fiber (STF) providing high higher-order-mode suppression with a large mode area for the fundamental mode shows potential for high-power and high-brightness applications. However, the output power of STFs has remained relatively low over
[...] Read more.
As a novel design of large-mode-area fiber, the single trench fiber (STF) providing high higher-order-mode suppression with a large mode area for the fundamental mode shows potential for high-power and high-brightness applications. However, the output power of STFs has remained relatively low over the past decade. In this paper, we first conducted a design process for STFs and determined the optimal ratio of the fiber structural parameters. Following this ratio, we fabricated an ytterbium-doped STF and demonstrated an all-fiberized fiber amplifier. The system achieved an output power of 2.5 kW with an M2 factor of 1.396. To the best of our knowledge, the power of the STF in this study is approximately three times higher than the previous single-mode power record.
Full article
(This article belongs to the Special Issue Research on Rare-Earth-Doped Fiber Lasers)
Open AccessArticle
A Practicable Optoelectronic Oscillator with Ultra-Low Phase Noise
by
Ziyue Zheng, Jinlong Yu, Ju Wang, Chuang Ma, Hao Luo, Xuemin Su and Ye Gao
Photonics 2024, 11(7), 614; https://doi.org/10.3390/photonics11070614 (registering DOI) - 28 Jun 2024
Abstract
In this paper, an optoelectronic oscillator (OEO) with ultra-low phase noise and high stability based on the injection-locked and phase-locked loop is proposed. In theory, the injection-locked frequency range of the injection signal is studied based on the phase dynamics equation, and the
[...] Read more.
In this paper, an optoelectronic oscillator (OEO) with ultra-low phase noise and high stability based on the injection-locked and phase-locked loop is proposed. In theory, the injection-locked frequency range of the injection signal is studied based on the phase dynamics equation, and the phase noise performance of the injection-locked OEO is analyzed. The role of the phase-locked loop on the frequency stability of the OEO is analyzed based on the phase-locked loop transfer function. In addition, this paper builds an injection-locked OEO based on a phase-locked loop. The injection-locked signal is the high-frequency output of the multiplication crystal oscillator (MCO). At the same time, this MCO synchronously outputs a low-frequency signal, which is used as the reference signal of the phase-locked loop. The experimental results show that the proposed OEO output frequency is 10 GHz, and the phase noise is −89.25 dBc/Hz@100 Hz, −121.71 dBc/Hz@1 kHz, and −145.39 dBc/Hz@10 kHz; the side-mode suppression ratio is 80 dB; the frequency stability is 2.06 × 10 @1 s, 9.03 × 10 @10 s, 1.03 × 10 @100 s, and 3.03 × 10 @1000 s. Consistent with the theoretical analysis results, the solution takes into account the frequency stability, side-mode suppression ratio, and phase noise performance. The simple structure is more advantageous in practical applications.
Full article
(This article belongs to the Section Optoelectronics and Optical Materials)
Open AccessReview
Machine Learning in Short-Reach Optical Systems: A Comprehensive Survey
by
Chen Shao, Elias Giacoumidis, Syed Moktacim Billah, Shi Li, Jialei Li, Prashasti Sahu, André Richter, Michael Faerber and Tobias Kaefer
Photonics 2024, 11(7), 613; https://doi.org/10.3390/photonics11070613 (registering DOI) - 28 Jun 2024
Abstract
Recently, extensive research has been conducted to explore the utilization of machine learning (ML) algorithms in various direct-detected and (self)-coherent short-reach communication applications. These applications encompass a wide range of tasks, including bandwidth request prediction, signal quality monitoring, fault detection, traffic prediction, and
[...] Read more.
Recently, extensive research has been conducted to explore the utilization of machine learning (ML) algorithms in various direct-detected and (self)-coherent short-reach communication applications. These applications encompass a wide range of tasks, including bandwidth request prediction, signal quality monitoring, fault detection, traffic prediction, and digital signal processing (DSP)-based equalization. As a versatile approach, ML demonstrates the ability to address stochastic phenomena in optical systems networks where deterministic methods may fall short. However, when it comes to DSP equalization algorithms such as feed-forward/decision-feedback equalizers (FFEs/DFEs) and Volterra-based nonlinear equalizers, their performance improvements are often marginal, and their complexity is prohibitively high, especially in cost-sensitive short-reach communications scenarios such as passive optical networks (PONs). Time-series ML models offer distinct advantages over frequency-domain models in specific contexts. They excel in capturing temporal dependencies, handling irregular or nonlinear patterns effectively, and accommodating variable time intervals. Within this survey, we outline the application of ML techniques in short-reach communications, specifically emphasizing their utilization in high-bandwidth demanding PONs. We introduce a novel taxonomy for time-series methods employed in ML signal processing, providing a structured classification framework. Our taxonomy categorizes current time-series methods into four distinct groups: traditional methods, Fourier convolution-based methods, transformer-based models, and time-series convolutional networks. Finally, we highlight prospective research directions within this rapidly evolving field and outline specific solutions to mitigate the complexity associated with hardware implementations. We aim to pave the way for more practical and efficient deployment of ML approaches in short-reach optical communication systems by addressing complexity concerns.
Full article
(This article belongs to the Special Issue Machine Learning Applied to Optical Communication Systems)
Open AccessArticle
Research on Lateral Inhibition Network Based on Cell Membrane Electrical Model
by
Dao-Han Qi, Ming-Jie Sun and Qing-Zhong Cai
Photonics 2024, 11(7), 612; https://doi.org/10.3390/photonics11070612 - 28 Jun 2024
Abstract
►▼
Show Figures
Lateral inhibition is a prevalent occurrence within the biological neural system, enhancing the human brain’s ability to perceive edge information within a given scene. With the increasing prominence of neural network-based machine vision, there is a significant importance in incorporating this crucial biological
[...] Read more.
Lateral inhibition is a prevalent occurrence within the biological neural system, enhancing the human brain’s ability to perceive edge information within a given scene. With the increasing prominence of neural network-based machine vision, there is a significant importance in incorporating this crucial biological mechanism into the field of machine vision. However, current research on lateral inhibition networks is divorced from biological reality, especially in the study of the inhibition coefficient. To address this issue, we proposed a lateral inhibition network based on the cell membrane electrical model and applied it to image enhancement. Firstly, we analyzed the visual formation mechanism and the lateral inhibition principle, laying the theoretical foundation. Secondly, leveraging the cell membrane electrical model, we construct a lateral inhibition network with a negative exponential distribution. Finally, our experiment demonstrates that a lateral inhibition network with a negative exponential distribution has better image enhancement ability than other distributions. Using images processed with lateral inhibition as an input improved the classification accuracy of the GoogLeNet neural network by 3.39%.
Full article
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-ag-550.jpg?1719565745)
Graphical abstract
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g002-550.jpg?1719565732)
Figure 2
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g003-550.jpg?1719565734)
Figure 3
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g004-550.jpg?1719565734)
Figure 4
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g005-550.jpg?1719565736)
Figure 5
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g006-550.jpg?1719565738)
Figure 6
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g007-550.jpg?1719565740)
Figure 7
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g008-550.jpg?1719565742)
Figure 8
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g009-550.jpg?1719565744)
Figure 9
![](https://pub.mdpi-res.com/photonics/photonics-11-00612/article_deploy/html/images/photonics-11-00612-g010-550.jpg?1719565745)
Figure 10
Open AccessArticle
Compact On-Chip Metalens-Assisted Optical Switch Enabling Efficient and Scalable Beam Switching
by
Chenxi Wang, Hongliang Li, Jinke Li and Sang-Shin Lee
Photonics 2024, 11(7), 611; https://doi.org/10.3390/photonics11070611 - 27 Jun 2024
Abstract
We propose and demonstrate an integrated optical switch that leverages an optical phased array (OPA) and an on-chip metalens, highlighting its potential for efficient and scalable beam switching across multiple ports within a compact footprint. The device consists of an input multimode interference
[...] Read more.
We propose and demonstrate an integrated optical switch that leverages an optical phased array (OPA) and an on-chip metalens, highlighting its potential for efficient and scalable beam switching across multiple ports within a compact footprint. The device consists of an input multimode interference (MMI) coupler, a phase modulator (PM) array, a beam-transformation region featuring an on-chip metalens layer, and a tapered waveguide array serving as the output ports. The PM array, engineered to effectively manipulate multiple phases for a waveguide array using a single voltage, utilizes metal strips of varying lengths to streamline operation. The on-chip metalens, characterized by varying slot lengths, facilitates the wavefront manipulation of the fast Fourier transform, resulting in beam deflection with a focusing length of 20 µm. The simulated validation of the proposed compact optical switch demonstrated efficient beam deflection, yielding a 1 × 8 beam switching at a wavelength of 1550 nm. Combinations of diverse OPAs and metalens configurations resulted in potential scalability, allowing for the realization of optical switches with pathway numbers ranging from 4 to 16. This development of a metalens-assisted optical switch on a compact chip presents significant practical implications for enhancing data transmission efficiency and scalability in photonic integrated circuits.
Full article
(This article belongs to the Section Optoelectronics and Optical Materials)
Open AccessReview
Overview on Space-Based Optical Orbit Determination Method Employed for Space Situational Awareness: From Theory to Application
by
Zhe Zhang, Gaopeng Zhang, Jianzhong Cao, Cheng Li, Weining Chen, Xin Ning and Zheng Wang
Photonics 2024, 11(7), 610; https://doi.org/10.3390/photonics11070610 - 27 Jun 2024
Abstract
Leveraging space-based optical platforms for space debris and defunct spacecraft detection presents several advantages, including a wide detection range, immunity to cloud cover, and the ability to maintain continuous surveillance on space targets. As a result, it has become an essential approach for
[...] Read more.
Leveraging space-based optical platforms for space debris and defunct spacecraft detection presents several advantages, including a wide detection range, immunity to cloud cover, and the ability to maintain continuous surveillance on space targets. As a result, it has become an essential approach for accomplishing tasks related to space situational awareness. However, the prediction of the orbits of space objects is crucial for the success of such missions, and current technologies face challenges related to accuracy, reliability, and practical efficiency. These challenges limit the performance of space-based optical space situational awareness systems. To drive progress in this field and establish a more effective and reliable space situational awareness system based on space optical platforms, this paper conducts a retrospective overview of research advancements in this area. It explores the research landscape of orbit determination methods, encompassing orbit association methods, initial orbit determination methods, and precise orbit determination methods, providing insights from international perspectives. The article concludes by highlighting key research areas, challenges, and future trends in current space situational awareness systems and orbit determination methods.
Full article
(This article belongs to the Special Issue Optical Systems for Astronomy)
►▼
Show Figures
![](https://pub.mdpi-res.com/photonics/photonics-11-00610/article_deploy/html/images/photonics-11-00610-g001-550.jpg?1719490921)
Figure 1
![](https://pub.mdpi-res.com/photonics/photonics-11-00610/article_deploy/html/images/photonics-11-00610-g003-550.jpg?1719490923)
Figure 3
![](https://pub.mdpi-res.com/photonics/photonics-11-00610/article_deploy/html/images/photonics-11-00610-g004-550.jpg?1719490923)
Figure 4
![](https://pub.mdpi-res.com/photonics/photonics-11-00610/article_deploy/html/images/photonics-11-00610-g005-550.jpg?1719490924)
Figure 5
![](https://pub.mdpi-res.com/photonics/photonics-11-00610/article_deploy/html/images/photonics-11-00610-g006-550.jpg?1719490924)
Figure 6
Open AccessArticle
Toward Converged Satellite/Fiber 1550 nm DS-BB84 QKD Networks: Feasibility Analysis and System Requirements
by
Aristeidis Stathis, Argiris Ntanos, Nikolaos K. Lyras, Giannis Giannoulis, Athanasios D. Panagopoulos and Hercules Avramopoulos
Photonics 2024, 11(7), 609; https://doi.org/10.3390/photonics11070609 - 27 Jun 2024
Abstract
Satellite-based QKD is currently being developed to revolutionize global cryptographic key exchange by facilitating secure communication among remote parties at a global scale. By overcoming the exponential loss of fiber transmission, satellite-to-Earth communication can seamlessly interconnect vast distances as the link budget of
[...] Read more.
Satellite-based QKD is currently being developed to revolutionize global cryptographic key exchange by facilitating secure communication among remote parties at a global scale. By overcoming the exponential loss of fiber transmission, satellite-to-Earth communication can seamlessly interconnect vast distances as the link budget of such links is sufficient to support QKD links. In terms of this direction, DV-QKD implementations seems to be technologically ahead since key exchange has been experimentally demonstrated to perform much more efficiently by providing key rates that are orders of magnitude higher compared to entanglement-based key exchange. However, the specific requirements to support effectively functional DV-QKD satellite-to-ground links are yet to be defined. This work attempts to define the satellite and ground segment system requirements needed in order to achieve functional QKD service for various satellites orbits (LEO, MEO, and GEO). Finite key size effects are being considered to determine the minimum block sizes that are required for secure key generation between a satellite node and a ground terminal for a single satellite pass. The atmospheric link channel is modeled with consideration of the most important degradation effects such as turbulence and atmospheric and pointing loss. Critical Tx and Rx system parameters, such as the source’s intrinsic Quantum Bit Error Rate (iQBER), the Rx telescope aperture size, and detection efficiency, were investigated in order to define the minimum requirements to establish an operation satellite-to-ground QKD link under specific assumptions. The performance of each downlink scenario was evaluated for the wavelength of 1550 nm in terms of link availability, link budget, and in the distilling of secure key volumes over time. Finally, the feasibility and requirements for distributing the collected space photons via terrestrial telecom fibers was also studied and discussed, leading to the proposal of a more futuristic WDM-enabled satellite QKD architecture. This comprehensive analysis aims to contribute to the advancement and implementation of effective satellite-based QKD systems, which can further exploit the ground fiber segment to realize converged space/terrestrial QKD networks.
Full article
(This article belongs to the Special Issue Optical Satellite Communications for Quantum Networking)
►▼
Show Figures
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g001-550.jpg?1719479942)
Figure 1
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g003-550.jpg?1719479944)
Figure 3
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g004-550.jpg?1719479945)
Figure 4
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g005-550.jpg?1719479946)
Figure 5
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g006-550.jpg?1719479948)
Figure 6
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g007-550.jpg?1719479948)
Figure 7
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g008-550.jpg?1719479949)
Figure 8
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g009-550.jpg?1719479950)
Figure 9
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g010-550.jpg?1719479952)
Figure 10
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g011-550.jpg?1719479953)
Figure 11
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g012-550.jpg?1719479954)
Figure 12
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g013-550.jpg?1719479956)
Figure 13
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g014-550.jpg?1719479957)
Figure 14
![](https://pub.mdpi-res.com/photonics/photonics-11-00609/article_deploy/html/images/photonics-11-00609-g015-550.jpg?1719479958)
Figure 15
Open AccessCommunication
Efficient Optical Coupling between Dielectric Strip Waveguides and a Plasmonic Trench Waveguide
by
Jia-Ren Wu, Anjali Chandel, Chiashain Chuang and Sheng Hsiung Chang
Photonics 2024, 11(7), 608; https://doi.org/10.3390/photonics11070608 - 27 Jun 2024
Abstract
Buttcoupling is the most efficient way to excite surface plasmon polariton (SPP) waves at dielectric/metal interfaces in order to realize applications in broadband and ultra-compact integrated circuits (IOCs). We propose a reasonable waveguide structure to efficiently excite and collect the SPP waves supported
[...] Read more.
Buttcoupling is the most efficient way to excite surface plasmon polariton (SPP) waves at dielectric/metal interfaces in order to realize applications in broadband and ultra-compact integrated circuits (IOCs). We propose a reasonable waveguide structure to efficiently excite and collect the SPP waves supported in a plasmonic trench waveguide in the long-haul telecommunication wavelength range. Our simulation results show that the coupling efficiency between the dielectric strip waveguides and a plasmonic trench waveguide can be optimized, which is dominated by the zigzag propagation path length in the dielectric strip loaded on the metal substrate. It is noted that nearly a 100% coupling efficiency can be achieved when the distance between the excitation source and the plasmonic waveguide is about 6.76 μm.
Full article
(This article belongs to the Special Issue Integrated Waveguide-Based Photonic Devices)
►▼
Show Figures
![](https://pub.mdpi-res.com/photonics/photonics-11-00608/article_deploy/html/images/photonics-11-00608-g001-550.jpg?1719467523)
Figure 1
![](https://pub.mdpi-res.com/photonics/photonics-11-00608/article_deploy/html/images/photonics-11-00608-g003-550.jpg?1719467524)
Figure 3
![](https://pub.mdpi-res.com/photonics/photonics-11-00608/article_deploy/html/images/photonics-11-00608-g004-550.jpg?1719467525)
Figure 4
Open AccessArticle
MT_Net: A Multi-Scale Framework Using the Transformer Block for Retina Layer Segmentation
by
Enyu Liu, Xiang He, Junchen Yue, Yanxin Guan, Shuai Yang, Lei Zhang, Aiqun Wang, Jianmei Li and Weiye Song
Photonics 2024, 11(7), 607; https://doi.org/10.3390/photonics11070607 - 27 Jun 2024
Abstract
Variations in the thickness of retinal layers serve as early diagnostic indicators for various fundus diseases, and precise segmentation of these layers is essential for accurately measuring their thickness. Optical Coherence Tomography (OCT) is an important non-invasive tool for diagnosing various eye diseases
[...] Read more.
Variations in the thickness of retinal layers serve as early diagnostic indicators for various fundus diseases, and precise segmentation of these layers is essential for accurately measuring their thickness. Optical Coherence Tomography (OCT) is an important non-invasive tool for diagnosing various eye diseases through the acquisition and layering of retinal images. However, noise and artifacts in images present significant challenges in accurately segmenting retinal layers. We propose a novel method for retinal layer segmentation that addresses these issues. This method utilizes ConvNeXt as the backbone network to enhance multi-scale feature extraction and incorporates a Transformer–CNN module to improve global processing capabilities. This method has achieved the highest segmentation accuracy on the Retina500 dataset, with a mean Intersection over Union (mIoU) of 81.26% and an accuracy (Acc) of 91.38%, and has shown excellent results on the public NR206 dataset.
Full article
(This article belongs to the Special Issue OCT Technology Advances and Their Applications in Disease Studies)
►▼
Show Figures
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g001-550.jpg?1719459192)
Figure 1
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g003-550.jpg?1719459196)
Figure 3
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g004-550.jpg?1719459197)
Figure 4
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g005-550.jpg?1719459199)
Figure 5
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g006-550.jpg?1719459200)
Figure 6
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g007-550.jpg?1719459201)
Figure 7
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g008-550.jpg?1719459203)
Figure 8
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g009-550.jpg?1719459204)
Figure 9
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g010-550.jpg?1719459205)
Figure 10
![](https://pub.mdpi-res.com/photonics/photonics-11-00607/article_deploy/html/images/photonics-11-00607-g011-550.jpg?1719459206)
Figure 11