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Photonics
Volume 11
Issue 6
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Photonics, Volume 11, Issue 6 (June 2024) – 100 articles

Cover Story (view full-size image): Cardiomyocytes are embedded in a complex extracellular matrix (ECM) that includes the basement membrane (BM) and interstitial matrix, which are crucial for maintaining cardiac morphology and function during development and adulthood. Effective tools are essential for analyzing these interactions in freshly dissected tissue and myocardial remodeling. This study used multimodal stimulated emission depletion (STED) microscopy for detailed characterization of the cardiomyocyte microenvironment in myocardial tissue. Paired with second harmonic generation and autofluorescence, the multimodal STED enabled multiplexed 3D imaging of protein distributions. The study revealed subdiffractional structures of the BM and capillaries, while also providing quantitative data on sarcomere length and capillary density, which are critical for assessing myocardial architecture. View this paper
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22 pages, 28838 KiB  
Article
Design of Multi-Waveguide Merged Multi-Frame Integration System for Integrated Interference Imaging System
by Chen Wang, Chunyu Liu, Huiling Hu, Yi Ding, Shipeng Ying and Quyouyang Gao
Photonics 2024, 11(6), 583; https://doi.org/10.3390/photonics11060583 - 20 Jun 2024
Viewed by 214
Abstract
The integrated interferometric imaging system has pointed out a highly promising direction for the development of high-resolution, small-volume, and lightweight optical imaging systems in orbit. However, the current integrated interferometric imaging system has the problem of a low signal-to-noise ratio (SNR) in orbit, [...] Read more.
The integrated interferometric imaging system has pointed out a highly promising direction for the development of high-resolution, small-volume, and lightweight optical imaging systems in orbit. However, the current integrated interferometric imaging system has the problem of a low signal-to-noise ratio (SNR) in orbit, which seriously restricts the practical application and development of the system. To solve this problem, a design method for a multi-waveguide merged multi-frame integration (MWMMFI) system is proposed in this paper. This method proposes a novel non-uniform sampling time axis, which achieves accurate extraction of multi-frame integration signals between interferometric arms, overcoming the limitations of traditional time delay integration (TDI) techniques that are not applicable to tilted optical waveguide arrays. Consequently, it extends the integration time and increases the accumulation of effective optical signals. Additionally, noise is suppressed through an accumulate first and then differentiate algorithm. Ultimately, this achieves an enhancement of the system’s SNR and optimizes the quality of the reconstructed images, all without increasing motion degradation. Simulation experiments indicate that compared to traditional systems, the MWMMFI design can increase the peak signal-to-noise ratio (PSNR) up to 4 times when the merging number is two, and up to 6.58 times when the merging number is three. This provides both technical insights and theoretical guidance for addressing the issue of enhancing the SNR of integrated interferometric imaging systems in orbit. Full article
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13 pages, 1736 KiB  
Article
Coalitional Game Theory-Based Resource Allocation Strategy for Robust IRS-VLC System
by Changling Liu, Jianping Wang, Lifang Feng, Huimin Lu, Haijian Sun and Rose Qingyang Hu
Photonics 2024, 11(6), 582; https://doi.org/10.3390/photonics11060582 - 20 Jun 2024
Viewed by 199
Abstract
This study investigates the optimization of energy efficiency in robust visible light communication (VLC)—intelligent reflecting surface (IRS) systems through a novel resource allocation strategy based on coalitional game theory. By employing coalitional game theory, the proposed strategy optimizes LED power and IRS energy [...] Read more.
This study investigates the optimization of energy efficiency in robust visible light communication (VLC)—intelligent reflecting surface (IRS) systems through a novel resource allocation strategy based on coalitional game theory. By employing coalitional game theory, the proposed strategy optimizes LED power and IRS energy consumption within practical constraints. IRS elements form coalitions centered around a central unit or units, enhancing the system performance through coordinated element management. Simulation results demonstrate significant improvements in energy efficiency and signal quality compared to conventional methods, validating the effectiveness of the proposed strategy. Full article
(This article belongs to the Special Issue Advancements in Wireless Optical Communication: Integrating Visible Light and Beyond)
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14 pages, 5431 KiB  
Article
The Optimization Design of a Lightweight 2 m SiC Mirror for Ground-Based Telescopes
by Zhichen Wang, Tao Chen, Yuyan Cao, Wenqiang Fan, Honghao Wang and Wenpan Wang
Photonics 2024, 11(6), 581; https://doi.org/10.3390/photonics11060581 - 20 Jun 2024
Viewed by 229
Abstract
The weight of the primary mirror increases as the aperture of ground-based telescopes increases, making it more challenging to maintain the positional stability and surface accuracy of the solid primary mirror. Consequently, a 2 m lightweight silicon carbide (SiC) mirror and an optimization [...] Read more.
The weight of the primary mirror increases as the aperture of ground-based telescopes increases, making it more challenging to maintain the positional stability and surface accuracy of the solid primary mirror. Consequently, a 2 m lightweight silicon carbide (SiC) mirror and an optimization method were proposed in this study. The relationship between the gravitational deformation of the mirror and its thickness and number of supports was derived based on force analysis of the mirror; the thickness of the mirror and the appropriate number of supports were obtained as initial parameters for optimization. The back structure of the mirror was designed in a lotus pattern to improve its rigidity. Numerous structural parameters were classified into major and non-major parameters based on the results of a sensitivity analysis. The non-major and major structural parameters were optimized using a Latin hypercube design method and a non-dominated sorting genetic algorithm, respectively. The optimized 2 m lightweight SiC mirror had a mass of 119 kg and an areal density of 38.7 kg/m2. The surface figure error root-mean-square (RMS) in the vertical state of the optical axis and the first modal resonance of the mirror assembly calculated using finite element analysis were 11.3 nm and 76.5 Hz, respectively. Modal tests of the mirror assembly were conducted using the hammering method, achieving a maximum relative frequency error of 7.4% compared with the simulation results. The optimized 2 m SiC mirror was over 50% lighter than traditional passive Zerodur mirrors of the same size. Full article
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16 pages, 4134 KiB  
Article
Simulation Analysis of Mode Hopping Impacts on OFDR Sensing Performance
by Qirui Wang, Nageswara Lalam, Kehao Zhao, Shuda Zhong, Guangyin Zhang, Ruishu Wright and Kevin P. Chen
Photonics 2024, 11(6), 580; https://doi.org/10.3390/photonics11060580 - 20 Jun 2024
Viewed by 317
Abstract
This article examines the impacts of mode hopping on the sensing performance of optical frequency domain reflectometry (OFDR) and explores the potential for developing economical OFDR interrogators employing low-cost distributed feedback (DFB) lasers. By conducting numerical simulations, this study reveals that mode hopping [...] Read more.
This article examines the impacts of mode hopping on the sensing performance of optical frequency domain reflectometry (OFDR) and explores the potential for developing economical OFDR interrogators employing low-cost distributed feedback (DFB) lasers. By conducting numerical simulations, this study reveals that mode hopping has minimal effects on distance sensing measurements in free space due to the limited duration of beat interference signal at the incorrect frequency within the coherence length. Additionally, the simulations indicate that mode hopping only slightly affects the distributed strain sensing of OFDR, resulting in an error range of less than ±1µε when 100µε is applied to the sensing fiber. These findings highlight the potential of using low-cost DFB lasers with a 1-nm wavelength sweep range and a 1-MHz linewidth as tunable laser sources in OFDR while maintaining reliable and accurate sensing performance. Full article
(This article belongs to the Special Issue Quantum Enhanced Devices and Instruments for Sensing Applications)
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9 pages, 2438 KiB  
Communication
Plasmonic Focusing of a High-Order Cylindrical Vector Beam for On-Chip Detection
by Hao Wang, Jinzhan Zhong, Xinrui Lei and Qiwen Zhan
Photonics 2024, 11(6), 579; https://doi.org/10.3390/photonics11060579 - 20 Jun 2024
Viewed by 232
Abstract
We investigate the interaction between cylindrical vector beams (CVBs) and metallic annular structures. The mechanisms for plasmonic focusing and field distributions are studied both analytically and numerically. We demonstrate that the focusing patterns are locked with the order of CVBs due to the [...] Read more.
We investigate the interaction between cylindrical vector beams (CVBs) and metallic annular structures. The mechanisms for plasmonic focusing and field distributions are studied both analytically and numerically. We demonstrate that the focusing patterns are locked with the order of CVBs due to the polarization selectivity for the excitation of plasmonic fields, which can be employed as a simplified yet efficient means of characterizing and detecting CVBs. The robustness of the focusing pattern is analyzed as a deviation between the centers of the CVBs and nanoring is introduced, providing a quantitative indicator of the relationship between the maximum deviation value and the focusing patterns. Our research contributes to a deeper understanding of interactions between CVBs and nanostructures, paving the way for novel applications in light detection and optical imaging. Full article
(This article belongs to the Section Optical Interaction Science)
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13 pages, 28796 KiB  
Article
Enhancing a Display’s Sunlight Readability with Tone Mapping
by Yizhou Qian, Sung-Chun Chen, En-Lin Hsiang, Hajime Akimoto, Chih-Lung Lin and Shin-Tson Wu
Photonics 2024, 11(6), 578; https://doi.org/10.3390/photonics11060578 - 20 Jun 2024
Viewed by 437
Abstract
The sunlight readability of display devices, such as notebook computers, transparent displays, vehicle displays, and augmented reality, is a significant technical challenge due to degraded image quality. To mitigate this problem, by fitting the human eye function, we propose a tone mapping method [...] Read more.
The sunlight readability of display devices, such as notebook computers, transparent displays, vehicle displays, and augmented reality, is a significant technical challenge due to degraded image quality. To mitigate this problem, by fitting the human eye function, we propose a tone mapping method on a mobile phone display panel to enhance low grayscale image readability under bright ambient light. Additionally, we adapt a mini-LED backlight model to simulate real images under different ambient lighting conditions. Both experimental and simulated results indicate that high luminance displays with an optimized gamma value significantly enhance sunlight readability and image quality. Moreover, global color rendering can alleviate color shift. Such a method is also valid for the optimization of optical see-through devices under diverse environmental conditions. Full article
(This article belongs to the Special Issue On-Chip Photonics)
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19 pages, 7766 KiB  
Article
Spectral-Kinetic Characterization of YF3: Eu3+ and YF3: (Eu3+, Nd3+) Nanoparticles for Optical Temperature Sensing
by Ekaterina I. Oleynikova, Oleg A. Morozov, Stella L. Korableva and Maksim S. Pudovkin
Photonics 2024, 11(6), 577; https://doi.org/10.3390/photonics11060577 - 20 Jun 2024
Viewed by 301
Abstract
YF3: (Eu3+, Nd3+) nanoparticles (orthorhombic phase, D~130 nm) were synthesized via the co-precipitation method, with subsequent hydrothermal treatment and annealing. The Eu3+ τdecay linearly descends with the increase of temperature in the 80–320 K range. [...] Read more.
YF3: (Eu3+, Nd3+) nanoparticles (orthorhombic phase, D~130 nm) were synthesized via the co-precipitation method, with subsequent hydrothermal treatment and annealing. The Eu3+ τdecay linearly descends with the increase of temperature in the 80–320 K range. The τdecay (T) slope values of the annealed YF3: Eu3+ (2.5 and 5.0 mol.%) nanoparticles were the highest (110·10−4 and 67·10−4, μs/K) in the whole 80–320 K range, respectively. Thus, these samples were chosen for further doping with Nd3+. The maximum Sa and Sr values based on the LIR (IEu/INd) function were 0.067 K−1 (at 80 K) and 0.86%·K−1 (at 154 K), respectively. As mentioned above, the single-doped YF3: Eu3+ (2.5%) nanoparticles showed the linearly decreasing τdecay (T) function (5D0–7F1 emission). The main idea of Nd3+ co-doping was to increase this slope value (as well as the sensitivity) by increasing the rate of τdecay (T) descent via the addition of one more temperature-dependent channel of 5D0 excited state depopulation. Indeed, we managed to increase the slope (Sa) to 180·10−4 K−1 at 80 K. This result is one of the highest compared to the world analogs. Full article
(This article belongs to the Section Optoelectronics and Optical Materials)
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13 pages, 2782 KiB  
Article
Richardson–Lucy Iterative Blind Deconvolution with Gaussian Total Variation Constraints for Space Extended Object Images
by Shiping Guo, Yi Lu and Yibin Li
Photonics 2024, 11(6), 576; https://doi.org/10.3390/photonics11060576 - 20 Jun 2024
Viewed by 266
Abstract
In ground-based astronomical observations or artificial space target detections, images obtained from a ground-based telescope are severely distorted due to atmospheric turbulence. The distortion can be partially compensated by employing adaptive optics (pre-detection compensation), image restoration techniques (post-detection compensation), or a combination of [...] Read more.
In ground-based astronomical observations or artificial space target detections, images obtained from a ground-based telescope are severely distorted due to atmospheric turbulence. The distortion can be partially compensated by employing adaptive optics (pre-detection compensation), image restoration techniques (post-detection compensation), or a combination of both (hybrid compensation). This paper focuses on the improvement of the most commonly used practical post-processing techniques, Richardson–Lucy (R–L) iteration blind deconvolution, which is studied in detail and improved as follows: First, the total variation (TV) norm is redefined using the Gaussian gradient magnitude and a set scheme for regularization parameter selection is proposed. Second, the Gaussian TV constraint is proposed to impose to the R–L algorithm. Last, the Gaussian TV R–L (GRL) iterative blind deconvolution method is finally presented, in which the restoration precision is visually increased and the convergence property is considerably improved. The performance of the proposed GRL method is tested by both simulation experiments and observed field data. Full article
(This article belongs to the Special Issue Adaptive Optics: Methods and Applications)
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18 pages, 1507 KiB  
Review
Advances in Lensless Fluorescence Microscopy Design
by Somaiyeh Khoubafarin, Edmond Kwesi Dadson and Aniruddha Ray
Photonics 2024, 11(6), 575; https://doi.org/10.3390/photonics11060575 - 19 Jun 2024
Viewed by 305
Abstract
Lensless fluorescence microscopy (LLFM) has emerged as a promising approach for biological imaging, offering a simplified, high-throughput, portable, and cost-effective substitute for conventional microscopy techniques by removing lenses in favor of directly recording fluorescent light on a digital sensor. However, there are several [...] Read more.
Lensless fluorescence microscopy (LLFM) has emerged as a promising approach for biological imaging, offering a simplified, high-throughput, portable, and cost-effective substitute for conventional microscopy techniques by removing lenses in favor of directly recording fluorescent light on a digital sensor. However, there are several obstacles that this novel approach must overcome, such as restrictions on the resolution, field-of-view (FOV), signal-to-noise ratio (SNR), and multicolor-imaging capabilities. This review looks at the most current developments aimed at addressing these challenges and enhancing the performance of LLFM systems. To address these issues, computational techniques, such as deconvolution and compressive sensing, hardware modifications and structured illumination, customized filters, and the utilization of fiber-optic plates, have been implemented. Finally, this review emphasizes the numerous applications of LLFM in tissue analysis, pathogen detection, and cellular imaging, highlighting its adaptability and potential influence in a range of biomedical research and clinical diagnostic areas. Full article
(This article belongs to the Special Issue Advanced Photonic Sensing and Measurement II)
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15 pages, 1147 KiB  
Article
Impact of Grating Duty-Cycle Randomness on DFB Laser Performance
by Manpo Yang, Xiangpeng Kong and Xun Li
Photonics 2024, 11(6), 574; https://doi.org/10.3390/photonics11060574 - 19 Jun 2024
Viewed by 311
Abstract
The duty-cycle randomness (DCR) of the Bragg grating of the distributed feedback (DFB) lasers introduced by the fabrication process is inevitable, even with state-of-the-art technologies such as electron beam lithography and dry or wet etching.This work investigates the impact of grating DCR on [...] Read more.
The duty-cycle randomness (DCR) of the Bragg grating of the distributed feedback (DFB) lasers introduced by the fabrication process is inevitable, even with state-of-the-art technologies such as electron beam lithography and dry or wet etching.This work investigates the impact of grating DCR on DFB laser performance through numerical simulations. The result reveals that such randomness causes a reduction in the side mode suppression ratio (SMSR), and deteriorates the noise characteristics, i.e., broadens the linewidth and increases the relative intensity noise (RIN). With the grating DCR, the effective grating coupling coefficient decreases as evidenced by the reduced Bragg stopband width. However, the longitudinal spatial hole burning (LSHB) effect in the DFB lasers can somewhat be diminished by the grating DCR. The seriousness of these effects depends on different grating structures and their coupling strengths. Our simulation shows that a degradation of 17 dB can be brought to the SMSR of the uniform grating DFB lasers with their duty cycles taking a deviation of ±25% in a uniformly distributed random fashion. It also broadens the linewidth of the quarter-wavelength phase-shifted DFB lasers by more than 2.5 folds. The impact of this effect on the RIN is moderate—less than 2%. All the performance deteriorations can partially be attributed to the effective reduction in the grating coupling coefficient of around 20% by such a DCR. Full article
(This article belongs to the Special Issue On-Chip Photonics)
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20 pages, 573 KiB  
Review
Angular Deviations, Lateral Displacements, and Transversal Symmetry Breaking: An Analytical Tutorial
by Stefano De Leo and Marco Mazzeo
Photonics 2024, 11(6), 573; https://doi.org/10.3390/photonics11060573 - 19 Jun 2024
Viewed by 325
Abstract
The study of a Gaussian laser beam interacting with an optical prism, both through reflection and transmission, provides a technical tool to examine deviations from the optical path as dictated by geometric optics principles. These deviations encompass alterations in the reflection and refraction [...] Read more.
The study of a Gaussian laser beam interacting with an optical prism, both through reflection and transmission, provides a technical tool to examine deviations from the optical path as dictated by geometric optics principles. These deviations encompass alterations in the reflection and refraction angles, as predicted by the reflection and Snell laws, along with lateral displacements in the case of total internal reflection. The analysis of the angular distributions of both the reflected and transmitted beams allows us to understand the underlying causes of these deviations and displacements, and it aids in formulating analytic expressions that are capable of characterizing these optical phenomena. The study also extends to the examination of transverse symmetry breaking, which is a phenomenon observed in the laser beam as it traverses the oblique interface of the prism. It is essential to underscore that this analytical overview does not strive to function as an exhaustive literature review of these optical phenomena. Instead, its primary objective is to provide a comprehensive and self-referential treatment, as well as give universal analytical formulas intended to facilitate experimental validations or applications in various technological contexts. Full article
(This article belongs to the Special Issue Structured Light Beams: Science and Applications)
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9 pages, 249 KiB  
Article
Few ns Pulse Duration of Gain-Switched Ho:YAG Laser Pumped by an Active Q-Switched Tm:YLF Laser
by Shaul Avichai Golan, Rotem Nahear, Yechiel Bach and Salman Noach
Photonics 2024, 11(6), 572; https://doi.org/10.3390/photonics11060572 - 18 Jun 2024
Viewed by 213
Abstract
This paper describes a gain-switched Ho:YAG laser that emitted at 2089 nm, driven by an actively Q-switched Tm:YLF laser as the pumping source. The laser attained few ns short pulse durations with high energies at controlled repetition rates due to the active Q-switch [...] Read more.
This paper describes a gain-switched Ho:YAG laser that emitted at 2089 nm, driven by an actively Q-switched Tm:YLF laser as the pumping source. The laser attained few ns short pulse durations with high energies at controlled repetition rates due to the active Q-switch pump source. Using the gain-switch method, stable short pulse durations ranging from 3.5 to 7.2 ns, with an energy per pulse of 0.4 to 0.52 mJ, were achieved at repetition rates of up to 2.5 kHz. This design can have significant advantages in various fields, where accuracy in the repetition rate is essential and a passive Q-switch cannot be implemented due to its accuracy limitations, including sensing, LIDAR, medical procedures, and material processing. Full article
(This article belongs to the Special Issue Laser Technology and Applications)
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12 pages, 6701 KiB  
Article
Full Stokes Mid-Wavelength Infrared Polarization Photodetector Based on the Chiral Dielectric Metasurface
by Bo Cheng, Yuxiao Zou and Guofeng Song
Photonics 2024, 11(6), 571; https://doi.org/10.3390/photonics11060571 - 18 Jun 2024
Viewed by 269
Abstract
Conventional imaging techniques can only record the intensity of light while polarization imaging can record the polarization of light, thus obtaining a higher dimension of image information. We use the COMSOL software to numerically propose a circular polarization photodetector composed of the dislocated [...] Read more.
Conventional imaging techniques can only record the intensity of light while polarization imaging can record the polarization of light, thus obtaining a higher dimension of image information. We use the COMSOL software to numerically propose a circular polarization photodetector composed of the dislocated 2-hole Si chiral metasurfaces controlling the circular polarization lights and the HgCdTe (MCT) photodetector chip to detect the intensity of light signals. The chiral metasurfaces can be equated to a significant radiation source of the Z-type current density under the right circularly polarized incidence conditions, which explains the large circular dichroism (CD) of absorption of 95% in chiral photodetectors. In addition, the linear dichroism (LD) of the linear polarization pixel is 0.62, and the extinction ratio (ER) is 21 dB. The full Stokes pixel using the six-image-element technique can almost measure arbitrary polarization information of light at 4 μm operation wavelength. Our results highlight the potential of circular dichroic metasurfaces as photonic manipulation platforms for miniaturized polarization detectors. Full article
(This article belongs to the Special Issue Design and Applications of Polarized Optical System)
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8 pages, 3159 KiB  
Communication
High-Power GHz Burst-Mode All-Fiber Laser System with Sub 300 fs Pulse Duration
by Feng Li, Wei Zhao, Yuxi Fu, Jixin Xing, Wenlong Wen, Lei Wang, Qianglong Li, Xue Cao, Hualong Zhao and Yishan Wang
Photonics 2024, 11(6), 570; https://doi.org/10.3390/photonics11060570 - 18 Jun 2024
Viewed by 283
Abstract
An all-fiber low-repetition-rate SESAM mode-locked fiber oscillator combined with a dispersion-managed active fiber loop produces a flexible GHz burst-mode laser source. The high-power output is then produced by amplifying the GHz burst-mode laser source using an all-fiber chirped-pulse amplification system. Then, the laser [...] Read more.
An all-fiber low-repetition-rate SESAM mode-locked fiber oscillator combined with a dispersion-managed active fiber loop produces a flexible GHz burst-mode laser source. The high-power output is then produced by amplifying the GHz burst-mode laser source using an all-fiber chirped-pulse amplification system. Then, the laser is compressed using a grating pair compressor; a maximum amplified power of 97 W is obtained. This results in a compressed high power of 82.07 W with a power stability RMS of 0.09% and beam quality better than 1.2. Accurate dispersion control allows for the production of a high-quality pulse duration of 265 fs. Full article
(This article belongs to the Special Issue Advanced Lasers and Their Applications II)
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18 pages, 15772 KiB  
Article
Physics-Based Practical Speckle Noise Modeling for Optical Coherence Tomography Image Denoising
by Lei Yang, Di Wu, Wenteng Gao, Ronald X. Xu and Mingzhai Sun
Photonics 2024, 11(6), 569; https://doi.org/10.3390/photonics11060569 - 17 Jun 2024
Viewed by 336
Abstract
Optical coherence tomography (OCT) has been extensively utilized in the field of biomedical imaging due to its non-invasive nature and its ability to provide high-resolution, in-depth imaging of biological tissues. However, the use of low-coherence light can lead to unintended interference phenomena within [...] Read more.
Optical coherence tomography (OCT) has been extensively utilized in the field of biomedical imaging due to its non-invasive nature and its ability to provide high-resolution, in-depth imaging of biological tissues. However, the use of low-coherence light can lead to unintended interference phenomena within the sample, which inevitably introduces speckle noise into the imaging results. This type of noise often obscures key features in the image, thereby reducing the accuracy of medical diagnoses. Existing denoising algorithms, while removing noise, tend to also damage the structural details of the image, affecting the quality of diagnosis. To overcome this challenge, we have proposed a speckle noise (PSN) framework. The core of this framework is an innovative dual-module noise generator that can decompose the noise in OCT images into speckle noise and equipment noise, addressing each type independently. By integrating the physical properties of noise into the design of the noise generator and training it with unpaired data, we are able to synthesize realistic noise images that match clear images. These synthesized paired images are then used to train a denoiser to effectively denoise real OCT images. Our method has demonstrated its superiority in both private and public datasets, particularly in maintaining the integrity of the image structure. This study emphasizes the importance of considering the physical information of noise in denoising tasks, providing a new perspective and solution for enhancing OCT image denoising technology. Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
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14 pages, 3246 KiB  
Article
Nanosensor Based on the Circular Ring with External Rectangular Ring Structure
by Shuwen Chang, Shubin Yan, Yiru Su, Jin Wang, Yuhao Cao, Yi Zhang, Taiquan Wu and Yifeng Ren
Photonics 2024, 11(6), 568; https://doi.org/10.3390/photonics11060568 - 17 Jun 2024
Viewed by 241
Abstract
This paper presents a novel nanoscale refractive index sensor, which is produced by using a metal–insulator–metal (MIM) waveguide structure coupled with the circular ring with an external rectangular ring (CRERR) structure with the Fano resonance phenomenon. In this study, COMSOL software was used [...] Read more.
This paper presents a novel nanoscale refractive index sensor, which is produced by using a metal–insulator–metal (MIM) waveguide structure coupled with the circular ring with an external rectangular ring (CRERR) structure with the Fano resonance phenomenon. In this study, COMSOL software was used to model and simulate the structure, paired with an analysis of the output spectra to detail the effect of constructional factors on the output Fano curve as measured from a finite element method. After a series of studies, it was shown that an external rectangular ring is the linchpin of the unsymmetrical Fano resonance, while the circular ring’s radius strongly influences the transducer’s capability to achieve a maximum for 3180 nm/RIU sensitivity and a FOM of 54.8. The sensor is capable of achieving sensitivities of 0.495 nm/mgdL−1 and 0.6375 nm/mgdL−1 when detecting the concentration of the electrolyte sodium and potassium ions in human blood and is expected to play an important role in human health monitoring. Full article
(This article belongs to the Special Issue New Perspectives in Optical Design)
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12 pages, 2673 KiB  
Article
A Study on the Irradiance Scintillation Characteristics of Monochromatic LED-Based Visible Light Communication Systems in Weak-to-Strong Turbulence
by Yao Ji, Wensheng Chen, Danning Wang and Chen Cheng
Photonics 2024, 11(6), 567; https://doi.org/10.3390/photonics11060567 - 17 Jun 2024
Viewed by 323
Abstract
Atmospheric turbulence causes transmitted light to fade randomly, which results in irradiance scintillation fluctuations in the received signal and significantly affects the quality of wireless optical communication systems. In this paper, we investigate the propagation characteristics of a monochromatic light-emitting diode (LED) light [...] Read more.
Atmospheric turbulence causes transmitted light to fade randomly, which results in irradiance scintillation fluctuations in the received signal and significantly affects the quality of wireless optical communication systems. In this paper, we investigate the propagation characteristics of a monochromatic light-emitting diode (LED) light beam through weak-to-strong turbulence. Considering the spatial incoherence of a monochromatic LED light source, the emitted light field of a monochromatic LED light source is represented by a random field multiplied by a deterministic field that follows a Gaussian distribution. Then, based on the extended-Rytov theory, a closed expression for the irradiance scintillation index under weak-to-strong turbulence is derived. In addition, the expression for the fading probability governed by the Gamma–Gamma model is given. Finally, the effects of near-earth atmospheric refractive index structural parameters, signal propagation distances, and working light wavelengths on propagation characteristics of the LED-based VLC system are simulated and compared with those of the laser-based one. The results theoretically confirm that laser light sources are more susceptible to atmospheric turbulence along the propagation path than monochromatic LED light sources. The investigation in this paper can provide theoretical support for the design of visible light communication systems in practical applications. Full article
(This article belongs to the Special Issue Optical Light Propagation and Communication Through Turbulent Medium)
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10 pages, 1738 KiB  
Article
An Effective Model for Capturing the Role of Excitonic Interactions in the Wave-Packet Dynamics of DNA Nucleobases
by Tong Guan, Ajay Jha, Pan-Pan Zhang and Hong-Guang Duan
Photonics 2024, 11(6), 566; https://doi.org/10.3390/photonics11060566 - 17 Jun 2024
Viewed by 245
Abstract
Investigating exciton dynamics within DNA nucleobases is essential for comprehensively understanding how inherent photostability mechanisms function at the molecular level, particularly in the context of life’s resilience to solar radiation. In this paper, we introduce a mathematical model that effectively simulates the photoexcitation [...] Read more.
Investigating exciton dynamics within DNA nucleobases is essential for comprehensively understanding how inherent photostability mechanisms function at the molecular level, particularly in the context of life’s resilience to solar radiation. In this paper, we introduce a mathematical model that effectively simulates the photoexcitation and deactivation dynamics of nucleobases within an ultrafast timeframe, particularly focusing on wave-packet dynamics under conditions of strong nonadiabatic coupling. Employing the hierarchy equation of motion, we simulate two-dimensional electronic spectra (2DES) and calibrate our model by comparing it with experimentally obtained spectra. This study also explores the effects of base stacking on the photo-deactivation dynamics in DNA. Our results demonstrate that, while strong excitonic interactions between nucleobases are present, they have a minimal impact on the deactivation dynamics of the wave packet in the electronic excited states. We further observe that the longevity of electronic excited states increases with additional base stacking and pairing, a phenomenon accurately depicted by our excitonic model. This model enables a detailed examination of the wave packet’s motion on electronic excited states and its rapid transition to the ground state. Additionally, using this model, we studied base stacks in DNA hairpins to effectively capture the primary exciton dynamics at a reasonable computational scale. Overall, this work provides a valuable framework for studying exciton dynamics from single nucleobases to complex structures such as DNA hairpins. Full article
(This article belongs to the Special Issue Ultrafast Optics and Applications)
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13 pages, 12033 KiB  
Article
Ytterbium-Doped Double-Clad Fiber with High Uniformity of Concentration Distribution and Suppressed Photodarkening
by Yongqing Yi, Yize Shen, Pengcheng Geng, Rong Pan, Shijie Xu and Ruifang Luo
Photonics 2024, 11(6), 565; https://doi.org/10.3390/photonics11060565 - 17 Jun 2024
Viewed by 339
Abstract
Photodarkening (PD) effect in ytterbium-doped fiber (YDF) has a significant impact on the high-power operational stability of fiber lasers, which seriously hinders the power scaling. In this paper, the relationship between ytterbium ions uniformity and the photodarkening effect in the YDF was investigated, [...] Read more.
Photodarkening (PD) effect in ytterbium-doped fiber (YDF) has a significant impact on the high-power operational stability of fiber lasers, which seriously hinders the power scaling. In this paper, the relationship between ytterbium ions uniformity and the photodarkening effect in the YDF was investigated, and the fabrication process allowing improving the ytterbium ions uniformity in the core of preforms for suppressing the photodarkening effect was developed. The Modified Chemical Vapor Deposition (MCVD) method combined with Chelate Vapor Deposition (CVD) technology was adopted for multi-layer fiber core deposition, and an all-gas-phase technical process was proposed to improve the ytterbium ions uniformity in the Al/P co-doped glass matrix. The 25/400 μm YDFs obtained by this technology achieved stable 3.5 kW laser output power for 8 h with suppressed PD and nonlinear effects. Full article
(This article belongs to the Special Issue The Emerging Science and Applications of Fiber Laser Technology)
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25 pages, 13354 KiB  
Article
Design of a Continuous-Zoom 2D/3D Microscope with High Zoom Ratio and Full Field of View
by Yangshen Gong, Fei Li, Jiebo Huang, Jiaying He, Feihong Yu and Tingyu Zhao
Photonics 2024, 11(6), 564; https://doi.org/10.3390/photonics11060564 - 16 Jun 2024
Viewed by 475
Abstract
A four-group mechanically compensated continuous-zoom microscope is proposed and designed based on the theory of continuous zoom. The system addresses the limitations of traditional continuous-zoom microscopes, including a small zoom ratio, a short working distance, and the loss of details during 2D–3D switching. [...] Read more.
A four-group mechanically compensated continuous-zoom microscope is proposed and designed based on the theory of continuous zoom. The system addresses the limitations of traditional continuous-zoom microscopes, including a small zoom ratio, a short working distance, and the loss of details during 2D–3D switching. The system has a magnification of 0.6×~6.0× under two-dimensional observation, adapts to two-third-inch sensors, has a working distance of 130 mm, and adds a 360-degree rotatable beamsplitter for three-dimensional full-field-of-view observation. The magnification, numerical aperture, and sensor dimensions remain unchanged under both two-dimensional and three-dimensional observation. The design results demonstrate that the system is capable of achieving a high zoom ratio of 10× while maintaining a high level of imaging quality in both two-dimensional and three-dimensional modes. The MTF curves for each magnification are in close proximity to the diffraction limit, the spot diagrams are smaller than the airy disk range, and the zoom cam curves are smooth with no inflection points. Furthermore, the system negates the visual discrepancies and loss of detail that arise when switching observation modes due to alterations in system magnification and numerical aperture, thereby broadening the scope of applications for continuous-zoom microscopes. Full article
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12 pages, 4617 KiB  
Article
Generating Optical Vortex Array Laser Beams of Superimposing Hermite–Gaussian Beams with a Dual–Phase Modulation Digital Laser System
by Ly Ly Nguyen Thi, Ko-Fan Tsai and Shu-Chun Chu
Photonics 2024, 11(6), 563; https://doi.org/10.3390/photonics11060563 - 15 Jun 2024
Viewed by 369
Abstract
This study presents an efficient and practical intra-cavity approach for selectively generating vortex array laser beams employing a dual-phase modulation digital laser system, which has not yet been completed in single-phase modulation digital laser. The stable optical vortex array laser beams were formed [...] Read more.
This study presents an efficient and practical intra-cavity approach for selectively generating vortex array laser beams employing a dual-phase modulation digital laser system, which has not yet been completed in single-phase modulation digital laser. The stable optical vortex array laser beams were formed by superimposing cavity Hermite–Gaussian (HG) eigenmodes. In particular, when the selected cavity HG modes shared the same Gouy phase, the resulting optical vortex beam could preserve its light field pattern, thereby maintaining the optical vortex properties in the near and far fields. Numerical results demonstrated that employing dual-phase modulation could establish optimal boundary conditions for the selection of HG modes within the cavity, successfully generating various vortex array laser beams. The experimental validation of the proposed method confirmed the ability to select optical vortex array lasers solely by controlling the loaded phase of the dual-phase modulation digital laser. These results demonstrate the ability of digital lasers to generate and dynamically control optical vortex array lasers. Full article
(This article belongs to the Special Issue Optical Vortex Laser)
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18 pages, 2319 KiB  
Article
Propagation of a Partially Coherent Bessel–Gaussian Beam in a Uniform Medium and Turbulent Atmosphere
by Igor Lukin and Vladimir Lukin
Photonics 2024, 11(6), 562; https://doi.org/10.3390/photonics11060562 - 14 Jun 2024
Viewed by 379
Abstract
In this paper, the coherent properties of partially coherent Bessel–Gaussian optical beams propagating through a uniform medium (free space) or a turbulent atmosphere are examined theoretically. The consideration is based on the analytical solution of the equation for the transverse second-order mutual coherence [...] Read more.
In this paper, the coherent properties of partially coherent Bessel–Gaussian optical beams propagating through a uniform medium (free space) or a turbulent atmosphere are examined theoretically. The consideration is based on the analytical solution of the equation for the transverse second-order mutual coherence function of the field of partially coherent optical radiation in a turbulent atmosphere. For the partially coherent Bessel–Gaussian beam, the second-order mutual coherence function of the source field is taken as a Gaussian–Schell model. In this approximation, we analyze the behavior of the coherence degree and the integral coherence scale of these beams as a function of the propagation pathlength, propagation conditions, and beam parameters, such as the radius of the Gauss factor of the beam, parameter of the Bessel factor of the beam, topological charge, and correlation width of the source field of partially coherent radiation. It was found that, as a partially coherent vortex Bessel–Gaussian beam propagates through a turbulent atmosphere, there appear not two (as might be expected: one due to atmospheric turbulence and another due to the partial coherence of the source field), but only one ring dislocation of the coherence degree (due to the simultaneous effect of both these factors on the optical radiation). In addition, it is shown that the dislocation of the coherence degree that significantly affects the beam coherence level is formed only for beams, for which the coherence width of the source field is larger than the diameter of the first Fresnel zone. Full article
(This article belongs to the Special Issue Recent Advances in Diffractive Optics)
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14 pages, 10209 KiB  
Article
Generalized-Mode Averaging Technique for Wrapped Phase
by Zhan Tang, Fengwei Liu and Yongqian Wu
Photonics 2024, 11(6), 561; https://doi.org/10.3390/photonics11060561 - 14 Jun 2024
Viewed by 298
Abstract
In this paper, a generalized-mode phase averaging technique is proposed to suppress air turbulence and random noise in optical shop testing. This approach eliminates the need to repeatedly unwrap and thus greatly improves processing efficiency. By removing the random tilt component of the [...] Read more.
In this paper, a generalized-mode phase averaging technique is proposed to suppress air turbulence and random noise in optical shop testing. This approach eliminates the need to repeatedly unwrap and thus greatly improves processing efficiency. By removing the random tilt component of the wrapped phase, a set of wrapped phases that are corrupted by random vibrations can be unified into the same mode, some of which obey a circular distribution. Therefore, the circular mean technique can be used for wrapped phase averaging; only one unwrapping process is required for a set of wrapped phases. A criterion based on maximum likelihood estimation is proposed to determine scenarios for the use of this method. The effects of noise and air disturbances on this method are discussed. Finally, the effectiveness of the method is demonstrated by simulations and experiments. Full article
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9 pages, 2039 KiB  
Article
Modulated Short-Time Fourier-Transform-Based Nonstationary Signal Decomposition for Dual-Comb Ranging Systems
by Ningning Han, Chao Wang, Zhiyang Wu, Xiaoyu Zhai, Yongzhen Pei, Haonan Shi and Xiaobo Li
Photonics 2024, 11(6), 560; https://doi.org/10.3390/photonics11060560 - 14 Jun 2024
Viewed by 344
Abstract
Analyzing and breaking down nonstationary signals into their primary components is significant in various optical applications. In this work, we design a direct, localized, and mathematically rigorous method for nonstationary signals by employing a modulated short-time Fourier transform (MSTFT) that can be implemented [...] Read more.
Analyzing and breaking down nonstationary signals into their primary components is significant in various optical applications. In this work, we design a direct, localized, and mathematically rigorous method for nonstationary signals by employing a modulated short-time Fourier transform (MSTFT) that can be implemented efficiently using fast Fourier transform, subsequently isolating energy-concentrated sets through an approximate threshold process, allowing us to directly retrieve instantaneous frequencies and signal components by determining the maximum frequency within each set. MSTFT provides a new insight into the time-frequency analysis in multicomponent signal separation and can be extended to other time-frequency transforms. Beyond the analysis of the synthetic, we also perform real dual-comb ranging signals under turbid water, and the results show an approximate 1.5 dB improvement in peak signal-to-noise ratio, further demonstrating the effectiveness of our method in challenging conditions. Full article
(This article belongs to the Special Issue Optical Technology for Challenging Conditions：Methods and Applications)
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10 pages, 3284 KiB  
Article
Simulation Study on Tunable Terahertz Bandpass Filter Based on Metal–Silicon–Metal Metasurface
by Wenjun Liu and Jitao Li
Photonics 2024, 11(6), 559; https://doi.org/10.3390/photonics11060559 - 13 Jun 2024
Viewed by 364
Abstract
Metasurface devices have demonstrated powerful electromagnetic wave manipulation capabilities. By adjusting the shape and size parameters of the metasurface microstructure, we can control the resonance between spatial electromagnetic waves and the metasurface, which will trigger wave scattering at a specific frequency. By utilizing [...] Read more.
Metasurface devices have demonstrated powerful electromagnetic wave manipulation capabilities. By adjusting the shape and size parameters of the metasurface microstructure, we can control the resonance between spatial electromagnetic waves and the metasurface, which will trigger wave scattering at a specific frequency. By utilizing these characteristics, we design a metasurface device with a bandpass filtering function and a unit cell of the metasurface consisting of a double-layer pinwheel-shaped metal structure and high resistance silicon substrate (forming metal–silicon–metal configuration). A bandpass filter operating in the terahertz band has been implemented, which achieves a 36 GHz filtering bandwidth when the transmission amplitude decreases by 3 dB and remains effective in a wave incidence angle of 20°. This work uses an equivalent RC resonance circuit to explain the formation of bandpass filtering. In addition, the photosensitive properties of silicon enable the filtering function of the device to have on/off tuned characteristics under light excitation, which enhances the dynamic controllability of the filter. The designed device may have application prospects in 6G space communication. Full article
(This article belongs to the Special Issue Metamaterials for Terahertz Photonics: Enabling Novel Techniques)
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10 pages, 2436 KiB  
Article
Time–Frequency and Spectrum Analyses of All-Solid-State Self-Mode-Locked Burst Pulse Lasers
by Mengmeng Xu, Miao Hu, Zerong Li, Jinxiu Wang, Jiaxin Fu, Shaokun Wang, Yingying Ji, Haozhen Li, Meihua Bi, Xuefang Zhou, Sunqiang Pan and Chong Liu
Photonics 2024, 11(6), 558; https://doi.org/10.3390/photonics11060558 - 13 Jun 2024
Viewed by 311
Abstract
The theoretical and experimental characteristics of all-solid-state self-mode-locked burst pulse lasers are investigated in this study. The time–frequency and spectrum analyses of the lasers incorporating Fabry–Pérot (F-P) structures are presented, along with the development of the corresponding theoretical model. Self-mode-locked burst pulse lasers [...] Read more.
The theoretical and experimental characteristics of all-solid-state self-mode-locked burst pulse lasers are investigated in this study. The time–frequency and spectrum analyses of the lasers incorporating Fabry–Pérot (F-P) structures are presented, along with the development of the corresponding theoretical model. Self-mode-locked burst pulse lasers are experimentally constructed to reduce intracavity losses using the front and rear end surfaces of the gain media to form F-P structures. When the laser cavity length is 600 mm and the gain media lengths are 5, 6, and 10 mm, each burst pulse produced contains 56, 47, and 28 subpulses, respectively, with the same burst pulse width of 2 ns. The burst pulse train with beam quality M2 = 1.37 and an average output power of 0.23 W is obtained when the gain medium length is 5 mm and the pump power is 4.5 W. The corresponding burst pulse repetition frequency is 0.25 GHz and the subpulse repetition frequency is 13.66 GHz. The time–frequency spectral analyses of the laser signals provide a good representation of laser spectral information that even the currently available highest-resolution spectrometers cannot resolve. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
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12 pages, 9879 KiB  
Article
Study on the Imaging Interference of a Vortex-Light-Modulated Gaussian Beam
by Yanghe Liu, Yuanhe Tang, Jian Zhou, Cunxia Li, Ningju Hui, Yishan Zhang and Yanlong Wang
Photonics 2024, 11(6), 557; https://doi.org/10.3390/photonics11060557 - 13 Jun 2024
Viewed by 348
Abstract
Combined with vortex light and airglow, some different physical phenomena are presented in this paper. Based on the ground-based airglow imaging interferometer (GBAII) made by our group, a liquid crystal on silicon (LCoS) device on one arm of a wide-angle Michelson interferometer (MI) [...] Read more.
Combined with vortex light and airglow, some different physical phenomena are presented in this paper. Based on the ground-based airglow imaging interferometer (GBAII) made by our group, a liquid crystal on silicon (LCoS) device on one arm of a wide-angle Michelson interferometer (MI) of the GBAII is replaced by the reflector mirror to become the GBAII-LCoS system. LCoS generates a vortex phase to convert a Gaussian profile airglow into a vortex light pattern. After the Gaussian profile vortex light equation is obtained by combining the Gaussian profile airglow with the Laguerre–Gauss light, three different physical phenomena are obtained: the simulated Gaussian vortex airglow beam exhibits a hollow phenomenon with the introduction of the vortex phase, and as the topological charge (TC) l increases, the hollow range also increases; after adding the vortex factor, the interference fringe intensity can be ‘broadened’ with the optical path difference (OPD) and TC l increases, which match the field broadening technology for solid wide-angle MI; the ‘Four-point algorithm’ wind measurement for the upper atmosphere based on the vortex airglow is derived, which is different from the usual expressions. Some experimental results are presented: We obtained the influence modes of vortex light interference and a polarization angle from 335° to 245°. We also obtained a series of interference images that verifies the rotation of the vortex light, onto which is loaded a set of superimposed vortex phase images with TC l = 3 into LCoS in turn, and the interference image is rotated under the condition of the polarization angle of 245°. The controlled vortex interference image for different TC and grayscale values are completed. Full article
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17 pages, 4307 KiB  
Article
High-Dynamic-Range Absorption Spectroscopy by Generating a Wide Path-Length Distribution with Scatterers
by Ayaka Mori, Kyohei Yamashita and Eiji Tokunaga
Photonics 2024, 11(6), 556; https://doi.org/10.3390/photonics11060556 - 13 Jun 2024
Viewed by 466
Abstract
In absorption spectroscopy, it is challenging to detect absorption peaks with significant differences in their intensity in a single measurement. We enable high-dynamic-range measurements by dispersing scatterers within a sample to create a broad distribution of path lengths (PLs). The sample is placed [...] Read more.
In absorption spectroscopy, it is challenging to detect absorption peaks with significant differences in their intensity in a single measurement. We enable high-dynamic-range measurements by dispersing scatterers within a sample to create a broad distribution of path lengths (PLs). The sample is placed within an integrating sphere (IS) to capture all scattered light of various PLs. To address the complexities of PLs inside the IS and the sample, we performed a ray-tracing simulation using the Monte Carlo (MC) method, which estimates the measured absorbance A and PL distribution from the sample’s absorption coefficient µa and scattering properties at each wavelength λ. This method was validated using dye solutions with two absorption peaks whose intensity ratio is 95:1, employing polystyrene microspheres (PSs) as scatterers. The results confirmed that both peak shapes were delineated in a single measurement without flattening the high absorption peak. Although the measured peak shapes A(λ) did not align with the actual peak shapes µa(λ), MC enabled the reproduction of µa(λ) from A(λ). Furthermore, the analysis of the PL distribution by MC shows that adding scatterers broadens the distribution and shifts it toward shorter PLs as absorption increases, effectively adjusting it to µa. Full article
(This article belongs to the Special Issue Photonics: 10th Anniversary)
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17 pages, 8273 KiB  
Article
High-Repetition-Rate 2.3–2.7 µm Acousto-Optically Tuned Narrow-Line Laser System Comprising Two Master Oscillators and Power Amplifiers Based on Polycrystalline Cr2+:ZnSe with the 2.1 µm Ho3+:YAG Pulsed Pumping
by Oleg Antipov, Ilya Eranov, Stanislav Balabanov, Anton Dobryinin, Yuri Getmanovskiy, Valeriy Sharkov and Nikolay Yudin
Photonics 2024, 11(6), 555; https://doi.org/10.3390/photonics11060555 - 12 Jun 2024
Viewed by 357
Abstract
High-average-power narrow-linewidth tunable solid-state lasers in the wavelength region between 2 and 3 μm are attractive light sources for many applications. This paper reports a narrow-linewidth widely tunable laser system based on the polycrystalline Cr2+:ZnSe elements pumped by repetitively pulsed 2.1 [...] Read more.
High-average-power narrow-linewidth tunable solid-state lasers in the wavelength region between 2 and 3 μm are attractive light sources for many applications. This paper reports a narrow-linewidth widely tunable laser system based on the polycrystalline Cr2+:ZnSe elements pumped by repetitively pulsed 2.1 µm Ho3+:YAG laser operating at a pulse rate of tens of kilohertz. An advanced procedure of ZnSe element doping and surface improvement was applied to increase the laser-induced damage threshold, which resulted in an increase in the output power of the Cr2+:ZnSe laser system. The high-average-power laser system comprised double master oscillators and power amplifiers: Ho3+:YAG and Cr2+:ZnSe laser oscillators, and Ho3+:YAG and Cr2+:ZnSe power amplifiers. The output wavelength was widely tuned within 2.3–2.7 µm by means of an acousto-optical tunable filter inside a Cr2+:ZnSe master oscillator cavity. The narrow-linewidth operation at the pulse repetition rate of 20–40 kHz in a high-quality beam with an average output power of up to 9.7 W was demonstrated. Full article
(This article belongs to the Special Issue Advanced Solid-State and Fiber Mid-IR Lasers: Novel Materils, Components, Systems and Applications)
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11 pages, 7758 KiB  
Communication
Design of Channel Drop Filters Based on Photonic Crystal with a Dielectric Column with Large Radius inside Ring Resonator
by Ailing Zhang, Xiangyu Yang and Junfeng Wang
Photonics 2024, 11(6), 554; https://doi.org/10.3390/photonics11060554 - 12 Jun 2024
Viewed by 307
Abstract
Photonic crystal channel drop filters (CDFs) play a vital role in optical communication owing to their ability to drop the desired channel. However, it remains challenging to achieve high-efficiency CDFs. Here, we demonstrate a highly efficient three-channel CDF with both high transmission and [...] Read more.
Photonic crystal channel drop filters (CDFs) play a vital role in optical communication owing to their ability to drop the desired channel. However, it remains challenging to achieve high-efficiency CDFs. Here, we demonstrate a highly efficient three-channel CDF with both high transmission and high quality (Q) factor based on a novel ring resonator that is in the middle of two waveguides. A dielectric column with a large radius replaces the homogeneously distributed dielectric columns inside the ring cavity to modulate the coupling ratio with a straight waveguide, thereby enhancing the transmission and Q factor. The transmission and Q factor of the single-cavity filter are 99.7% and 12,798.4, respectively. The mean value of the three-channel filter based on the basic unit can reach up to 94.6% and 10,617, respectively, and a crosstalk between −30.16 and −50.61 dB is obtained. The proposed CDFs provide efficient filter capability, which reveals great potential in integrated optoelectronics and optical communication. Full article
(This article belongs to the Section Optoelectronics and Optical Materials)
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