Pub Date : 2025-01-15DOI: 10.1016/j.optcom.2025.131522
Ming Zhang, Junyao Zhang, Yiwen Wu, Lin Yang, Baozhu Wang, Qi Han
In this study, a multifunctional terahertz (THz) metasurface based on vanadium dioxide (VO2) is proposed and demonstrated. Under the external stimulus of thermal, the proposed metasurface can achieve ultra-wideband absorption, perfect narrowband absorption and polarization selection by leveraging the phase transition characteristics of VO2. In its metal state, VO2 enables the metasurface to function as a THz broadband absorber with an absorption efficiency exceeding 90% across a broad frequency range, exhibiting minimal polarization sensitivity. Conversely, in its insulating state, the metasurface operates as a narrowband absorber. The asymmetric split ring structure exhibits near-perfect absorption (>99.7%) for TE-polarized waves at 8.663 THz and complete reflection for TM-polarized waves, enabling effective polarization selectivity with a polarization extinction ratio of 25.15 dB. Through the analysis of impedance, electric field and surface current distribution, the absorbing mechanism is explained in detail. Additionally, we considered the impact of structural parameters and incident angles on the performance. The innovation and high performance of this metasurface provide a broader idea and method for the design of THz detectors, and have important application prospects in the fields of THz detection, modulation, and optical switches.
{"title":"Multifunctional vanadium dioxide-based terahertz metasurface with ultra-wideband, narrowband switching and polarization selection","authors":"Ming Zhang, Junyao Zhang, Yiwen Wu, Lin Yang, Baozhu Wang, Qi Han","doi":"10.1016/j.optcom.2025.131522","DOIUrl":"10.1016/j.optcom.2025.131522","url":null,"abstract":"<div><div>In this study, a multifunctional terahertz (THz) metasurface based on vanadium dioxide (VO<sub>2</sub>) is proposed and demonstrated. Under the external stimulus of thermal, the proposed metasurface can achieve ultra-wideband absorption, perfect narrowband absorption and polarization selection by leveraging the phase transition characteristics of VO<sub>2</sub>. In its metal state, VO<sub>2</sub> enables the metasurface to function as a THz broadband absorber with an absorption efficiency exceeding 90% across a broad frequency range, exhibiting minimal polarization sensitivity. Conversely, in its insulating state, the metasurface operates as a narrowband absorber. The asymmetric split ring structure exhibits near-perfect absorption (>99.7%) for TE-polarized waves at 8.663 THz and complete reflection for TM-polarized waves, enabling effective polarization selectivity with a polarization extinction ratio of 25.15 dB. Through the analysis of impedance, electric field and surface current distribution, the absorbing mechanism is explained in detail. Additionally, we considered the impact of structural parameters and incident angles on the performance. The innovation and high performance of this metasurface provide a broader idea and method for the design of THz detectors, and have important application prospects in the fields of THz detection, modulation, and optical switches.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"579 ","pages":"Article 131522"},"PeriodicalIF":2.2,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143159012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-14DOI: 10.1016/j.optcom.2025.131492
Takuya Hirahara, Fan Wang, Tomoyoshi Ito, Tomoyoshi Shimobaba
Amplitude holograms are computationally efficient but generate unwanted conjugate and direct lights. This paper presents a deep neural network-based converter for amplitude to complex and phase-only hologram conversion. The proposed method uses real-to-real diffraction calculations, which are faster than conventional complex diffraction calculations, to generate 3D layer holograms. The deep neural network then predicts the imaginary hologram from the amplitude hologram. Compared to a conventional method based on the angular spectrum method, the proposed method accelerates the computation of a 3D layer hologram by approximately 1.4 times. The proposed method can accurately predict complex holographic images.
{"title":"Converting amplitude holograms into complex and phase-only holograms using deep neural network-based converters","authors":"Takuya Hirahara, Fan Wang, Tomoyoshi Ito, Tomoyoshi Shimobaba","doi":"10.1016/j.optcom.2025.131492","DOIUrl":"10.1016/j.optcom.2025.131492","url":null,"abstract":"<div><div>Amplitude holograms are computationally efficient but generate unwanted conjugate and direct lights. This paper presents a deep neural network-based converter for amplitude to complex and phase-only hologram conversion. The proposed method uses real-to-real diffraction calculations, which are faster than conventional complex diffraction calculations, to generate 3D layer holograms. The deep neural network then predicts the imaginary hologram from the amplitude hologram. Compared to a conventional method based on the angular spectrum method, the proposed method accelerates the computation of a 3D layer hologram by approximately 1.4 times. The proposed method can accurately predict complex holographic images.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"578 ","pages":"Article 131492"},"PeriodicalIF":2.2,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-14DOI: 10.1016/j.optcom.2025.131519
Zhenzhao Xu , Yu Hou , Zhidong Wen , Feng Li , Song Yue , Kunpeng Zhang , Zichen Zhang
This paper presents an investigation into the acquisition performance of inter-satellite optical communication systems between low Earth orbit and geostationary orbit satellites, specifically addressing the challenges posed by platform vibration and asymmetric initial pointing errors. The study begins with a brief overview of conventional spiral scan (CSS), highlighting the limitations of the CSS in handling asymmetric error conditions. A novel rhombus spiral scan (RSS) method is then proposed, which optimizes the scanning process by prioritizing regions of high probability density, improving both acquisition probability and acquisition time. The theoretical foundations of the RSS method are developed, followed by a comparative analysis using Monte Carlo simulations and experimental validation. Special focus is given to the impact of asymmetric initial pointing errors and vibration, demonstrating that under practical conditions, the RSS method achieves a 7% improvement in acquisition probability and a 14.9% reduction in acquisition time compared to CSS. Finally, the advantages of the RSS method for enhancing acquisition performance in real-world inter-satellite optical communication systems are discussed.
{"title":"Acquisition performance for inter-satellite optical communication between low earth orbit and geostationary orbit satellites with vibration and asymmetric initial pointing errors","authors":"Zhenzhao Xu , Yu Hou , Zhidong Wen , Feng Li , Song Yue , Kunpeng Zhang , Zichen Zhang","doi":"10.1016/j.optcom.2025.131519","DOIUrl":"10.1016/j.optcom.2025.131519","url":null,"abstract":"<div><div>This paper presents an investigation into the acquisition performance of inter-satellite optical communication systems between low Earth orbit and geostationary orbit satellites, specifically addressing the challenges posed by platform vibration and asymmetric initial pointing errors. The study begins with a brief overview of conventional spiral scan (CSS), highlighting the limitations of the CSS in handling asymmetric error conditions. A novel rhombus spiral scan (RSS) method is then proposed, which optimizes the scanning process by prioritizing regions of high probability density, improving both acquisition probability and acquisition time. The theoretical foundations of the RSS method are developed, followed by a comparative analysis using Monte Carlo simulations and experimental validation. Special focus is given to the impact of asymmetric initial pointing errors and vibration, demonstrating that under practical conditions, the RSS method achieves a 7% improvement in acquisition probability and a 14.9% reduction in acquisition time compared to CSS. Finally, the advantages of the RSS method for enhancing acquisition performance in real-world inter-satellite optical communication systems are discussed.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"579 ","pages":"Article 131519"},"PeriodicalIF":2.2,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143159943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-13DOI: 10.1016/j.optcom.2025.131518
Quan Zheng , Jinyan Wang , Xi Chen , Huidong Xiao , Yu Liu , Qi Li , Shijie Li
We presented an ultra-violet laser at 193 nm by sum-frequency generation of an 705 nm Raman laser and 266 nm laser. The 705 nm laser is generated by the 5th-order-cascade Raman of the SrWO4 crystal. The maximum average output power of 35 mW at 193 nm was obtained at 5 kHz with the pulse width 9.76 ns. It sets a new precedent for obtaining all-solid-state 193-nm lasers.
{"title":"Development of a compact 193-nm all-solid-state laser at 5 kHz","authors":"Quan Zheng , Jinyan Wang , Xi Chen , Huidong Xiao , Yu Liu , Qi Li , Shijie Li","doi":"10.1016/j.optcom.2025.131518","DOIUrl":"10.1016/j.optcom.2025.131518","url":null,"abstract":"<div><div>We presented an ultra-violet laser at 193 nm by sum-frequency generation of an 705 nm Raman laser and 266 nm laser. The 705 nm laser is generated by the 5th-order-cascade Raman of the SrWO4 crystal. The maximum average output power of 35 mW at 193 nm was obtained at 5 kHz with the pulse width 9.76 ns. It sets a new precedent for obtaining all-solid-state 193-nm lasers.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"578 ","pages":"Article 131518"},"PeriodicalIF":2.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143172086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-13DOI: 10.1016/j.optcom.2025.131513
Fu Yang , Yan Ning , Bowen Deng , Jiaqi Zhou , Qing Ye , Wei Long
Fast, real-time, high-precision distance measurement is of great significance for satellite formation flying, large-scale equipment manufacturing, and gravitational wave detection. These applications require ranging precision in the micrometer level for large-scale ranging. The dual comb ranging (DCR) technique reaches high precision range measurement by using a pair of optical frequency combs with a slight pulse repetition rate difference, which ensures asynchronous optical sampling. The stability of the pulse repetition rate, carrier envelope offset frequency, and mutual coherence of the two combs are the key issues to keep the high range precision. However, the complex locking units makes the DCR ranging system complicated, which limits its application significantly. To address this problem, we propose a free-running DCR high-precision ranging system. Software self-correction algorithm replaces the complicated hardware control system. The software signal processing algorithm utilizes mutual ambiguity processing, cross-correlation and repetition rate correction. The signal processing effect is also compared with the direct envelope peaks extraction algorithm. The feasibility of the system is verified both from simulation and experiment. The range precision can achieve 3.63 um in a single measurement when the target distance is about 1 m, the laser repetition frequency is about 100 MHz, and the frequency difference of the two combs is about 774 Hz. The precision can further drop below 700 nm with 90 times averaging. This work shows prospect that the free-running DCR system can be used in the field application.
{"title":"Investigation of a high precision ranging system based on free-running dual comb ranging","authors":"Fu Yang , Yan Ning , Bowen Deng , Jiaqi Zhou , Qing Ye , Wei Long","doi":"10.1016/j.optcom.2025.131513","DOIUrl":"10.1016/j.optcom.2025.131513","url":null,"abstract":"<div><div>Fast, real-time, high-precision distance measurement is of great significance for satellite formation flying, large-scale equipment manufacturing, and gravitational wave detection. These applications require ranging precision in the micrometer level for large-scale ranging. The dual comb ranging (DCR) technique reaches high precision range measurement by using a pair of optical frequency combs with a slight pulse repetition rate difference, which ensures asynchronous optical sampling. The stability of the pulse repetition rate, carrier envelope offset frequency, and mutual coherence of the two combs are the key issues to keep the high range precision. However, the complex locking units makes the DCR ranging system complicated, which limits its application significantly. To address this problem, we propose a free-running DCR high-precision ranging system. Software self-correction algorithm replaces the complicated hardware control system. The software signal processing algorithm utilizes mutual ambiguity processing, cross-correlation and repetition rate correction. The signal processing effect is also compared with the direct envelope peaks extraction algorithm. The feasibility of the system is verified both from simulation and experiment. The range precision can achieve 3.63 um in a single measurement when the target distance is about 1 m, the laser repetition frequency is about 100 MHz, and the frequency difference of the two combs is about 774 Hz. The precision can further drop below 700 nm with 90 times averaging. This work shows prospect that the free-running DCR system can be used in the field application.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"578 ","pages":"Article 131513"},"PeriodicalIF":2.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-13DOI: 10.1016/j.optcom.2025.131514
Xiaochao Cao , Zekai Xu , Shuguang Li
Ultrashort pulsed beams carrying intrinsic orbital angular momentum (OAM) have crucial applications in a variety of research fields. Based on the analytical expression of the vectorially polarized single-cycle vortex beams (VPSCVB) derived from the electric dipole radiation theory, we calculated the average intrinsic OAM carried per photon in an annular pulsed beam. Our results show the OAM will decrease dramatically as the pulse width go into single-cycle condition. This restriction can be attributed to the interaction between the spatiotemporal coupling and OAM. The changes in both polarization states and average OAM of VPSCVB with propagation distance reveals the conversion of angular momentum. Finally, we discuss the evolution properties of the pulse-front curvature (PFC) angles of VPSCVB.
{"title":"Limitations of intrinsic orbital angular momentum carried by the vectorially polarized single-cycle vortex beams","authors":"Xiaochao Cao , Zekai Xu , Shuguang Li","doi":"10.1016/j.optcom.2025.131514","DOIUrl":"10.1016/j.optcom.2025.131514","url":null,"abstract":"<div><div>Ultrashort pulsed beams carrying intrinsic orbital angular momentum (OAM) have crucial applications in a variety of research fields. Based on the analytical expression of the vectorially polarized single-cycle vortex beams (VPSCVB) derived from the electric dipole radiation theory, we calculated the average intrinsic OAM carried per photon in an annular pulsed beam. Our results show the OAM will decrease dramatically as the pulse width go into single-cycle condition. This restriction can be attributed to the interaction between the spatiotemporal coupling and OAM. The changes in both polarization states and average OAM of VPSCVB with propagation distance reveals the conversion of angular momentum. Finally, we discuss the evolution properties of the pulse-front curvature (PFC) angles of VPSCVB.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"579 ","pages":"Article 131514"},"PeriodicalIF":2.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143159733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-13DOI: 10.1016/j.optcom.2025.131516
Jin Jiang , Yiqun Wei , Yutao Yue , Hongmin Chen , Fenghe Yang , Jishi Cui
This paper presents a novel lateral incidence Ge-on-Si photodetector designed to utilize laterally incident light, achieving a uniform light field distribution within the germanium absorption region. The LI-PD features a germanium layer whose length is greater in the direction perpendicular to the incident light than in the parallel direction. Additionally, residual light is reabsorbed through reflection from the DBR, and the electrode design has been optimized to minimize light absorption. Despite a relatively small active region, the photodetector demonstrates a saturated photocurrent of 9.79 mA and a bandwidth of 22.62 GHz at an incident light power of 20 mW, compared to 7.23 mA and 9.39 GHz in conventional photodetectors. Moreover, at low optical power (0.5 mW), when the frequency exceeds 11.25 GHz, the responsivity of this device surpasses that of traditional structures.
{"title":"Lateral incidence Ge-on-Si photodetector with high saturation characteristics","authors":"Jin Jiang , Yiqun Wei , Yutao Yue , Hongmin Chen , Fenghe Yang , Jishi Cui","doi":"10.1016/j.optcom.2025.131516","DOIUrl":"10.1016/j.optcom.2025.131516","url":null,"abstract":"<div><div>This paper presents a novel lateral incidence Ge-on-Si photodetector designed to utilize laterally incident light, achieving a uniform light field distribution within the germanium absorption region. The LI-PD features a germanium layer whose length is greater in the direction perpendicular to the incident light than in the parallel direction. Additionally, residual light is reabsorbed through reflection from the DBR, and the electrode design has been optimized to minimize light absorption. Despite a relatively small active region, the photodetector demonstrates a saturated photocurrent of 9.79 mA and a bandwidth of 22.62 GHz at an incident light power of 20 mW, compared to 7.23 mA and 9.39 GHz in conventional photodetectors. Moreover, at low optical power (0.5 mW), when the frequency exceeds 11.25 GHz, the responsivity of this device surpasses that of traditional structures.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"578 ","pages":"Article 131516"},"PeriodicalIF":2.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Free Space Optical (FSO) communication is considered effective and efficient for high-speed wireless data transmission, particularly in urban environments. However, the quality of service (QoS) in FSO links is highly susceptible to environmental factors such as atmospheric turbulence, rain, fog, and dust storms, which are common in South Africa. The current demands for high-capacity free-space optical (FSO) communications, in terms of transmission capacity, latency, and reliability, are driven by rapid advancements in communication technology and the massive utilization of data. However, FSO communications are significantly affected by adverse weather conditions such as fog, rain, snow, smoke, dust, and drizzle, all of which impact the Quality of Service (QoS) provided by these systems. This article aims to optimize the QoS using ensemble learning models such as Random Forest (RF), AdaBoost Regressor (ABR), Stacking Regressor (SR), Gradient Boosting Regressor (GBR), and Multilayer Neural Network (MLNN). To achieve this goal, meteorological data, including visibility, wind speed, and altitude, were obtained from the archives of the South African Weather Service over a period of ten years (2010–2019) at four locations: Polokwane, Kimberley, Bloemfontein, and George. We estimated the data rate, received power, fog-induced attenuation, bit error rate (BER), and power penalty using the collected and processed data. For an optical attenuation of approximately 1 dB/km at a wavelength of 1550 nm across the study locations—Polokwane, Kimberley, Bloemfontein, and George—the transmitted power of the FSO link is capable of supporting data rates of 1.62 × 101⁴, 7.68 × 1012, 2.80 × 1012, and 2.90 × 101³ bps, respectively. At the same wavelength (1550 nm) and a visibility of 1 km, the values of the attenuation factor across Polokwane, Kimberley, Bloemfontein, and George are 2.13, 2.13, 2.13, and 2.13 dB/km, respectively. Furthermore, for attenuation of 1 dB/km, the BER values across the study locations—Polokwane, Kimberley, Bloemfontein, and George—are 6.743 × 10⁻1³, 6.730 × 10⁻1³, 6.750 × 10⁻1³, and 6.755 × 10⁻1³, respectively. The RMSE and R-squared values of the SR model across all the study locations, Polokwane, Kimberley, Bloemfontein, and George, are 0.0073 and 0.9951, 0.0065 and 0.9998, 0.0060 and 0.9941, and 0.0032 and 0.9906, respectively. The result showed that using ensemble learning techniques in transmission modeling can significantly enhance service quality and meet customer service level agreements. Regardless of the linked climate vicissitude along the transmission connection, the outcomes demonstrated that the ensemble method was successful in efficiently optimizing the signal-to-noise ratio, which in turn enhanced the QoS at the point of reception.
{"title":"Optimized quality of service prediction in FSO links over South Africa using ensemble learning","authors":"S.O. Adebusola , P.A. Owolawi , J.S. Ojo , P.S. Maswikaneng","doi":"10.1016/j.optcom.2025.131509","DOIUrl":"10.1016/j.optcom.2025.131509","url":null,"abstract":"<div><div>Free Space Optical (FSO) communication is considered effective and efficient for high-speed wireless data transmission, particularly in urban environments. However, the quality of service (QoS) in FSO links is highly susceptible to environmental factors such as atmospheric turbulence, rain, fog, and dust storms, which are common in South Africa. The current demands for high-capacity free-space optical (FSO) communications, in terms of transmission capacity, latency, and reliability, are driven by rapid advancements in communication technology and the massive utilization of data. However, FSO communications are significantly affected by adverse weather conditions such as fog, rain, snow, smoke, dust, and drizzle, all of which impact the Quality of Service (QoS) provided by these systems. This article aims to optimize the QoS using ensemble learning models such as Random Forest (RF), AdaBoost Regressor (ABR), Stacking Regressor (SR), Gradient Boosting Regressor (GBR), and Multilayer Neural Network (MLNN). To achieve this goal, meteorological data, including visibility, wind speed, and altitude, were obtained from the archives of the South African Weather Service over a period of ten years (2010–2019) at four locations: Polokwane, Kimberley, Bloemfontein, and George. We estimated the data rate, received power, fog-induced attenuation, bit error rate (BER), and power penalty using the collected and processed data. For an optical attenuation of approximately 1 dB/km at a wavelength of 1550 nm across the study locations—Polokwane, Kimberley, Bloemfontein, and George—the transmitted power of the FSO link is capable of supporting data rates of 1.62 × 10<sup>1</sup>⁴, 7.68 × 10<sup>12</sup>, 2.80 × 10<sup>12</sup>, and 2.90 × 10<sup>1</sup>³ bps, respectively. At the same wavelength (1550 nm) and a visibility of 1 km, the values of the attenuation factor across Polokwane, Kimberley, Bloemfontein, and George are 2.13, 2.13, 2.13, and 2.13 dB/km, respectively. Furthermore, for attenuation of 1 dB/km, the BER values across the study locations—Polokwane, Kimberley, Bloemfontein, and George—are 6.743 × 10⁻<sup>1</sup>³, 6.730 × 10⁻<sup>1</sup>³, 6.750 × 10⁻<sup>1</sup>³, and 6.755 × 10⁻<sup>1</sup>³, respectively. The RMSE and R-squared values of the SR model across all the study locations, Polokwane, Kimberley, Bloemfontein, and George, are 0.0073 and 0.9951, 0.0065 and 0.9998, 0.0060 and 0.9941, and 0.0032 and 0.9906, respectively. The result showed that using ensemble learning techniques in transmission modeling can significantly enhance service quality and meet customer service level agreements. Regardless of the linked climate vicissitude along the transmission connection, the outcomes demonstrated that the ensemble method was successful in efficiently optimizing the signal-to-noise ratio, which in turn enhanced the QoS at the point of reception.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"579 ","pages":"Article 131509"},"PeriodicalIF":2.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143159939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-13DOI: 10.1016/j.optcom.2025.131515
Sami Labidi , Justin B. Maughan , Kurt Ehlers , Prakash Gautam , Christopher M. Sorensen , Hans Moosmüller
We explore Mie scattering by a homogeneous, spherical particle of radius much smaller than the wavelength of light and a complex refractive index. When the medium refractive index is a real number equal to the real part of the particle refractive index, the effective particle refractive index is of the form In this case, scattering is caused solely by the imaginary part of the particle refractive index, resembling Rayleigh scattering at small values and perfect conductor scattering at large values of . We employ a Mie computer program to simulate the scattering in this case; we plot the results and see that as increases, the scattering of s-polarized light becomes more anisotropic, the backscattering intensity brightens while the forward scattering intensity dims. To explain our results theoretically, we explore how the Mie equations reduce for constraints of size parameter and a refractive index of the form though our analysis holds for arbitrary so long as We find that such small particles may be described by a dipole with appropriate electric and magnetic dipole moments. Simple equations are given describing the scattering by these particles. Finally, we supplement our results with diagrams visualizing why we see the pattern found.
{"title":"Dipole-like scattering by Rayleigh-sized particles with medium-matched real and general imaginary part of the refractive index","authors":"Sami Labidi , Justin B. Maughan , Kurt Ehlers , Prakash Gautam , Christopher M. Sorensen , Hans Moosmüller","doi":"10.1016/j.optcom.2025.131515","DOIUrl":"10.1016/j.optcom.2025.131515","url":null,"abstract":"<div><div>We explore Mie scattering by a homogeneous, spherical particle of radius much smaller than the wavelength of light and a complex refractive index. When the medium refractive index is a real number equal to the real part of the particle refractive index, the effective particle refractive index is of the form <span><math><mrow><mn>1</mn><mo>+</mo><mi>i</mi><mi>κ</mi><mtext>.</mtext></mrow></math></span> In this case, scattering is caused solely by the imaginary part <span><math><mrow><mi>κ</mi></mrow></math></span> of the particle refractive index, resembling Rayleigh scattering at small values and perfect conductor scattering at large values of <span><math><mrow><mi>κ</mi></mrow></math></span>. We employ a Mie computer program to simulate the scattering in this case; we plot the results and see that as <span><math><mrow><mi>κ</mi></mrow></math></span> increases, the scattering of s-polarized light becomes more anisotropic, the backscattering intensity brightens while the forward scattering intensity dims. To explain our results theoretically, we explore how the Mie equations reduce for constraints of size parameter <span><math><mrow><mi>x</mi><mo>≪</mo><mn>1</mn></mrow></math></span> and a refractive index of the form <span><math><mrow><mi>m</mi><mo>=</mo><mn>1</mn><mo>+</mo><mi>i</mi><mi>κ</mi><mtext>,</mtext></mrow></math></span> though our analysis holds for arbitrary <span><math><mrow><mi>m</mi></mrow></math></span> so long as <span><math><mrow><mi>R</mi><mi>e</mi><mrow><mo>(</mo><mrow><mi>m</mi><mi>x</mi></mrow><mo>)</mo></mrow><mo>≪</mo><mn>1</mn><mtext>.</mtext></mrow></math></span> We find that such small particles may be described by a dipole with appropriate electric and magnetic dipole moments. Simple equations are given describing the scattering by these particles. Finally, we supplement our results with diagrams visualizing why we see the pattern found.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"578 ","pages":"Article 131515"},"PeriodicalIF":2.2,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-11DOI: 10.1016/j.optcom.2025.131512
Zhenkai Fan, Juntao Lin, Xiuqing Zhang, Junhao Meng, Jiaming Liu
A highly sensitive surface plasmon resonance based photonic crystal fiber (SPR-PCF) refractive index sensor is designed, and a layer of gold (Au) film is coated inside the C-groove etched at the periphery of the optical fiber to excite the surface plasmon resonance, and its performance is analyzed numerically by the finite element method (FEM). To investigate the effect of titanium dioxide (TiO2) coating on the performance of the SPR-PCF sensor, a layer of TiO2 with a thickness of 10 nm is added on top of the Au layer. The effects of the Au film and TiO2 coating thickness, structure, and other parameters on the sensitivity and stability of the sensor are investigated. The simulation results show that the sensitivity of the sensor is significantly improved by the addition of the TiO2 coating, with an average sensitivity of 10500 nm/RIU. The average refractive index sensitivity of the sensor is increased by 184% compared with that of a single layer of Au film, and the maximum sensitivity is increased from 6000 to 29000 nm/RIU. This study not only helps to optimize the design of the refractive index sensors for SPR-PCF but also provides an opportunity to develop new types of refractive index sensors for SPR-PCF.
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