Pub Date : 2023-12-25DOI: 10.3390/photonics11010015
Zhonghua Yang, Wenbo Luo, Yu Sun
We present a high-efficiency silicon grating coupler design based on a left–right mirror-symmetric grating and a metal mirror. The coupler achieves nearly perfect 90-degree vertical coupling. When two SOI chips are placed face to face with a vertical working distance of 50 μm, the chip-to-chip interlayer coupling efficiency reaches as high as 96%. When the vertical working distance ranges from 45 μm to 55 μm, the coupling loss remains below 1 dB. We also verified the effectiveness of our designed vertical coupler through 3D FDTD full-model simulation. The results demonstrate that our proposed vertical coupling structure represents a high-efficiency solution for 3D optical interconnects. The integration of multiple photonic chips in a 3D package with vertical optical and electrical interconnects is also feasible in the foreseeable future.
我们介绍了一种基于左右镜面对称光栅和金属镜的高效硅光栅耦合器设计。该耦合器实现了近乎完美的 90 度垂直耦合。当两个 SOI 芯片面对面放置，垂直工作距离为 50 μm 时，芯片到芯片的层间耦合效率高达 96%。当垂直工作距离为 45 μm 至 55 μm 时，耦合损耗保持在 1 dB 以下。我们还通过三维 FDTD 全模型仿真验证了所设计的垂直耦合器的有效性。结果表明，我们提出的垂直耦合结构是三维光互连的高效解决方案。在可预见的未来，将多个光子芯片集成到带有垂直光电互连的三维封装中也是可行的。
{"title":"Computational Study of the Coupling Performances for a Long-Distance Vertical Grating Coupler","authors":"Zhonghua Yang, Wenbo Luo, Yu Sun","doi":"10.3390/photonics11010015","DOIUrl":"https://doi.org/10.3390/photonics11010015","url":null,"abstract":"We present a high-efficiency silicon grating coupler design based on a left–right mirror-symmetric grating and a metal mirror. The coupler achieves nearly perfect 90-degree vertical coupling. When two SOI chips are placed face to face with a vertical working distance of 50 μm, the chip-to-chip interlayer coupling efficiency reaches as high as 96%. When the vertical working distance ranges from 45 μm to 55 μm, the coupling loss remains below 1 dB. We also verified the effectiveness of our designed vertical coupler through 3D FDTD full-model simulation. The results demonstrate that our proposed vertical coupling structure represents a high-efficiency solution for 3D optical interconnects. The integration of multiple photonic chips in a 3D package with vertical optical and electrical interconnects is also feasible in the foreseeable future.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"10 10","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139158198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-12-25DOI: 10.3390/photonics11010012
Alexey Kadochkin, Andrey Savitskiy, D. Korobko, E. Kitsyuk
A numerical optimization technique of a three-dimensional (3D) SERS substrate with finite element analysis is proposed. Using the optical reciprocity theorem, we have shown that instead of the well-known local field enhancement criterion, it is more correct to use the Purcell factor as an objective function that determines the quality of the SERS substrate. This allows us to take into account the detail inhomogeneity of local fields in an arbitrary three-dimensional structure containing multiple emitters. We have theoretically shown that employment of a 3D CNT structure as a nanoparticle substrate instead of a nanoparticle monolayer allows one to achieve the enhancement of the SERS signal.
{"title":"Numerical Optimization Technique of Multilayer SERS Substrates","authors":"Alexey Kadochkin, Andrey Savitskiy, D. Korobko, E. Kitsyuk","doi":"10.3390/photonics11010012","DOIUrl":"https://doi.org/10.3390/photonics11010012","url":null,"abstract":"A numerical optimization technique of a three-dimensional (3D) SERS substrate with finite element analysis is proposed. Using the optical reciprocity theorem, we have shown that instead of the well-known local field enhancement criterion, it is more correct to use the Purcell factor as an objective function that determines the quality of the SERS substrate. This allows us to take into account the detail inhomogeneity of local fields in an arbitrary three-dimensional structure containing multiple emitters. We have theoretically shown that employment of a 3D CNT structure as a nanoparticle substrate instead of a nanoparticle monolayer allows one to achieve the enhancement of the SERS signal.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"20 2","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139157553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-12-25DOI: 10.3390/photonics11010014
A. Reddy, Vasu Dev, Vishwa Pal, R. Ganeev
We present the results of improving resolution in the imaging of two closely spaced point sources with an optical system under the influence of apodization and different types of aberrations. In particular, we consider the effect of coma and astigmatism, which are well-known aberrations that can deteriorate the resolution of an optical imaging system. Furthermore, a parabolic apodizer was included in an optical system to improve its imaging capabilities. We found that the two-point imaging performance of an optical system with a parabolic apodizer strongly depends on the coherence conditions of incident light. Furthermore, to analyze the efficiency of the parabolic apodizer, we compared the results of two-point imaging obtained with apodized and unapodized optical systems for distances between the two-point sources, less than or equal to the diffraction limit of an optical system. Moreover, the results of imaging the USAF chart with a parabolic apodizer are presented to show the apodizer’s efficacy in single-object imaging. Our results can be applied to the imaging of closely moving structures in microscopy, resolving dense spectral lines in spectroscopy experiments, and developing systems useful for resolving the images of closely associated far-distance objects in astronomical observations.
{"title":"The Effect of a Parabolic Apodizer on Improving the Imaging of Optical Systems with Coma and Astigmatism Aberrations","authors":"A. Reddy, Vasu Dev, Vishwa Pal, R. Ganeev","doi":"10.3390/photonics11010014","DOIUrl":"https://doi.org/10.3390/photonics11010014","url":null,"abstract":"We present the results of improving resolution in the imaging of two closely spaced point sources with an optical system under the influence of apodization and different types of aberrations. In particular, we consider the effect of coma and astigmatism, which are well-known aberrations that can deteriorate the resolution of an optical imaging system. Furthermore, a parabolic apodizer was included in an optical system to improve its imaging capabilities. We found that the two-point imaging performance of an optical system with a parabolic apodizer strongly depends on the coherence conditions of incident light. Furthermore, to analyze the efficiency of the parabolic apodizer, we compared the results of two-point imaging obtained with apodized and unapodized optical systems for distances between the two-point sources, less than or equal to the diffraction limit of an optical system. Moreover, the results of imaging the USAF chart with a parabolic apodizer are presented to show the apodizer’s efficacy in single-object imaging. Our results can be applied to the imaging of closely moving structures in microscopy, resolving dense spectral lines in spectroscopy experiments, and developing systems useful for resolving the images of closely associated far-distance objects in astronomical observations.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"25 9","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139157408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-12-23DOI: 10.3390/photonics11010010
M. Komlenok, Vitali Kononenko, Andrey P. Bolshakov, Nikolay D. Kurochitskiy, D. Pasternak, Alexander A. Ushakov, Vitaly Konov
Conductive graphitized grooves on the dielectric surface of diamond have been created by KrF excimer laser radiation. The advantages of such a circuit board in high-field applications is rather limited because the crystal surface has a relatively low electrical breakdown threshold. To increase the electrical strength, a method of encapsulating surface conductive graphitized structures by chemical vapor deposition of an epitaxial diamond layer has been proposed and realized. The quality of the growth diamond is proved by Raman spectroscopy. A comparative study of the electrical resistivity of graphitized wires and the breakdown fields between them before and after diamond growth was carried out. The proposed technique is crucial for diamond-based high-field electro-optical devices, such as THz photoconductive emitters.
{"title":"CVD Encapsulation of Laser-Graphitized Electrodes in Diamond Electro-Optical Devices","authors":"M. Komlenok, Vitali Kononenko, Andrey P. Bolshakov, Nikolay D. Kurochitskiy, D. Pasternak, Alexander A. Ushakov, Vitaly Konov","doi":"10.3390/photonics11010010","DOIUrl":"https://doi.org/10.3390/photonics11010010","url":null,"abstract":"Conductive graphitized grooves on the dielectric surface of diamond have been created by KrF excimer laser radiation. The advantages of such a circuit board in high-field applications is rather limited because the crystal surface has a relatively low electrical breakdown threshold. To increase the electrical strength, a method of encapsulating surface conductive graphitized structures by chemical vapor deposition of an epitaxial diamond layer has been proposed and realized. The quality of the growth diamond is proved by Raman spectroscopy. A comparative study of the electrical resistivity of graphitized wires and the breakdown fields between them before and after diamond growth was carried out. The proposed technique is crucial for diamond-based high-field electro-optical devices, such as THz photoconductive emitters.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"13 3","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139161379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
CO gas is not only lethal but also a significant forecasting indicator for the spontaneous combustion of coal mines. It is imperative that monitoring modules for CO gas that work well in the coal mine environment are available. A feasible solution is the detection of CO by using monitoring modules based on tunable diode laser absorption spectroscopy (TDLAS) over a mid-infrared waveband near 4.6 μm. However, in most cases, the mid-infrared TDLAS-based CO monitoring module tends to introduce severe interference fringe noise into the TDLAS spectral backgrounds which is difficult to filter out using traditional spectral filtering methods, reducing the detection performance of the module. In order to filter out the noise and improve the stability of the module in complex coal mine environments, this work proposed an algorithm based on support vector regression (SVR) to extract the TDLAS spectral backgrounds. Spectral analysis indicates that the TDLAS spectral background can be predicted over the entire scanning spectrum range by using this algorithm, and the noise in the spectral background can be effectively filtered out when calculating the absorbance spectrum based on the Lambert–Beer law. Compared to extracting spectral backgrounds using the traditional least square polynomial fit, the obtained correlation coefficients between regression models of spectral backgrounds and corresponding training point datasets were increased from below 0.998 to above 0.999. The peak-to-peak value of the obtained N2 absorbance spectrum was suppressed below 0.022 from nearly 0.045. The signal-to-noise ratio of the obtained 25 ppm CO absorbance spectrum was increased to 13.35 from 6.95. A CO monitoring module polluted by dust was used to conduct experiments to further test the SVR-based algorithm. The experiment results showed that after programming the SVR-based algorithm to the module, the estimated limit of detection of the module was reduced to 5.46 ppm from 29.08 ppm, and all the absolute measuring errors of the standard CO gases with different low concentrations were reduced to less than 4 ppm from a majority of the errors of more than 10 ppm, compared to least square polynomial fit. The CO monitoring module could still maintain the performance of high-precision quantitative detection when using the SVR-based algorithm even if it had been polluted severely. So, the CO monitoring module has good adaptability to harsh field environments, and its operation stability can be effectively improved by using the algorithm proposed in this work.
{"title":"Stability Improvement of the TDLAS-Based CO Monitoring Module in a Coal Mine by Using a Spectral Denoising Algorithm Based on SVR","authors":"Yin Wang, Lianqing Li, Haoran Li, Feng Hu, Pengbo Qian","doi":"10.3390/photonics11010011","DOIUrl":"https://doi.org/10.3390/photonics11010011","url":null,"abstract":"CO gas is not only lethal but also a significant forecasting indicator for the spontaneous combustion of coal mines. It is imperative that monitoring modules for CO gas that work well in the coal mine environment are available. A feasible solution is the detection of CO by using monitoring modules based on tunable diode laser absorption spectroscopy (TDLAS) over a mid-infrared waveband near 4.6 μm. However, in most cases, the mid-infrared TDLAS-based CO monitoring module tends to introduce severe interference fringe noise into the TDLAS spectral backgrounds which is difficult to filter out using traditional spectral filtering methods, reducing the detection performance of the module. In order to filter out the noise and improve the stability of the module in complex coal mine environments, this work proposed an algorithm based on support vector regression (SVR) to extract the TDLAS spectral backgrounds. Spectral analysis indicates that the TDLAS spectral background can be predicted over the entire scanning spectrum range by using this algorithm, and the noise in the spectral background can be effectively filtered out when calculating the absorbance spectrum based on the Lambert–Beer law. Compared to extracting spectral backgrounds using the traditional least square polynomial fit, the obtained correlation coefficients between regression models of spectral backgrounds and corresponding training point datasets were increased from below 0.998 to above 0.999. The peak-to-peak value of the obtained N2 absorbance spectrum was suppressed below 0.022 from nearly 0.045. The signal-to-noise ratio of the obtained 25 ppm CO absorbance spectrum was increased to 13.35 from 6.95. A CO monitoring module polluted by dust was used to conduct experiments to further test the SVR-based algorithm. The experiment results showed that after programming the SVR-based algorithm to the module, the estimated limit of detection of the module was reduced to 5.46 ppm from 29.08 ppm, and all the absolute measuring errors of the standard CO gases with different low concentrations were reduced to less than 4 ppm from a majority of the errors of more than 10 ppm, compared to least square polynomial fit. The CO monitoring module could still maintain the performance of high-precision quantitative detection when using the SVR-based algorithm even if it had been polluted severely. So, the CO monitoring module has good adaptability to harsh field environments, and its operation stability can be effectively improved by using the algorithm proposed in this work.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"93 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139163239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-12-22DOI: 10.3390/photonics11010008
Pin-Wen Cheng, Yu-Hsin Hsu, H. Liang, Kai-Feng Huang, Yung-Fu Chen
The critical pump power for achieving passively continuous-wave mode-locking in a solid-state laser is analytically derived from the spatially dependent rate equations and the criterion for the intracavity pulse energy. A prompt way is proposed to straightforwardly design the cavity for passively mode-locked solid-state lasers. Complete experiments are performed to demonstrate the proposed cavity design and, simultaneously, to verify the theoretical model for the critical pump powers. It is interestingly observed that even though a larger modulation depth causes a higher critical pump power, it can generate a shorter pulse width in return.
{"title":"Prompt Analysis and Design for Passively Mode-Locked Solid-State Lasers with Semiconductor Saturable Absorbers","authors":"Pin-Wen Cheng, Yu-Hsin Hsu, H. Liang, Kai-Feng Huang, Yung-Fu Chen","doi":"10.3390/photonics11010008","DOIUrl":"https://doi.org/10.3390/photonics11010008","url":null,"abstract":"The critical pump power for achieving passively continuous-wave mode-locking in a solid-state laser is analytically derived from the spatially dependent rate equations and the criterion for the intracavity pulse energy. A prompt way is proposed to straightforwardly design the cavity for passively mode-locked solid-state lasers. Complete experiments are performed to demonstrate the proposed cavity design and, simultaneously, to verify the theoretical model for the critical pump powers. It is interestingly observed that even though a larger modulation depth causes a higher critical pump power, it can generate a shorter pulse width in return.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"77 6","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138945568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-12-22DOI: 10.3390/photonics11010009
Gan Chen, Bingwei Liu, Ping Lu, Yan Peng
Ochratoxin A (OTA), which is highly toxic and carcinogenic, is easily produced in cereal crops, dry herbs, and other foods under improper storage. Traditional detection methods, including high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA), can detect OTA accurately, but there are many problems such as long period, high cost, and poor reproducibility. Therefore, developing a rapid, non-destructive, and highly sensitive method for OTA detection is essential. In this paper, we used a surface plasmon resonance (SPR) biosensor combined with terahertz (THz) spectroscopy to quantify OTA. As a result, the concentration range of OTA in acetonitrile solution was up to 0–20 pg/μL, with a detection limit of 1 pg/μL, which can meet the requirements for OTA detection in most foods. Further, we applied this method to black tea, and the detection limit was up to 1 pg/mg, which is 500 times higher than UV spectrophotometry, and completely meets the EU regulations. This study shows that the combination of terahertz spectroscopy and an SPR biosensor is a promising approach to achieve a simple, rapid, and low-cost method for trace substance quantification in foods and drugs.
{"title":"Rapid Determination of Ochratoxin A in Black Tea Using Terahertz Ultrasensitive Biosensor","authors":"Gan Chen, Bingwei Liu, Ping Lu, Yan Peng","doi":"10.3390/photonics11010009","DOIUrl":"https://doi.org/10.3390/photonics11010009","url":null,"abstract":"Ochratoxin A (OTA), which is highly toxic and carcinogenic, is easily produced in cereal crops, dry herbs, and other foods under improper storage. Traditional detection methods, including high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA), can detect OTA accurately, but there are many problems such as long period, high cost, and poor reproducibility. Therefore, developing a rapid, non-destructive, and highly sensitive method for OTA detection is essential. In this paper, we used a surface plasmon resonance (SPR) biosensor combined with terahertz (THz) spectroscopy to quantify OTA. As a result, the concentration range of OTA in acetonitrile solution was up to 0–20 pg/μL, with a detection limit of 1 pg/μL, which can meet the requirements for OTA detection in most foods. Further, we applied this method to black tea, and the detection limit was up to 1 pg/mg, which is 500 times higher than UV spectrophotometry, and completely meets the EU regulations. This study shows that the combination of terahertz spectroscopy and an SPR biosensor is a promising approach to achieve a simple, rapid, and low-cost method for trace substance quantification in foods and drugs.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"7 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138947470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
This paper introduces an innovative approach to integral volumetric imaging employing time and polarization multiplexing techniques to present volumetric three-dimensional images. Traditional integral volumetric imaging systems with a coarse lens array often face moiré pattern issues stemming from layered panel structures. In response, our proposed system utilizes a combination of time and polarization multiplexing to achieve two focal planes using a single display panel.
{"title":"Coarse Integral Volumetric Imaging Display with Time and Polarization Multiplexing","authors":"Garimagai Borjigin, Yuqiang Ding, John Semmen, Hosna Tajvidi Safa, Hideki Kakeya, Shin-Tson Wu","doi":"10.3390/photonics11010007","DOIUrl":"https://doi.org/10.3390/photonics11010007","url":null,"abstract":"This paper introduces an innovative approach to integral volumetric imaging employing time and polarization multiplexing techniques to present volumetric three-dimensional images. Traditional integral volumetric imaging systems with a coarse lens array often face moiré pattern issues stemming from layered panel structures. In response, our proposed system utilizes a combination of time and polarization multiplexing to achieve two focal planes using a single display panel.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"18 2","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138951195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-12-21DOI: 10.3390/photonics11010004
Na Chen, Yang Jiang, Xiao Lan, Yuejiao Zi, Jing Xu, Jiahui Li, Qiong Zhang, Jinjian Feng
Due to carrier dynamics, the modulated light field from a directly modulated laser (DML) has an intensity envelope with a certain frequency chirp. When the chirp is linearly mapped into intensity by a frequency discriminator such as an optical filter with a linear edge, the optical field presents a new signal determined by the multiplication operation between the envelope function and the chirp function. Under a triangular drive signal, this process can contribute dark, bright and frequency-doubled bright parabolic waveforms by properly adjusting the filter window. This method is verified by both a theoretical analysis and experimental demonstrations. It not only provides a low-cost and simple scheme to generate parabola signals, but also a new method for arbitrary waveform generation.
{"title":"A Parabolic Waveform Generator Based on the Chirp Characteristics of a Directly Modulated Laser","authors":"Na Chen, Yang Jiang, Xiao Lan, Yuejiao Zi, Jing Xu, Jiahui Li, Qiong Zhang, Jinjian Feng","doi":"10.3390/photonics11010004","DOIUrl":"https://doi.org/10.3390/photonics11010004","url":null,"abstract":"Due to carrier dynamics, the modulated light field from a directly modulated laser (DML) has an intensity envelope with a certain frequency chirp. When the chirp is linearly mapped into intensity by a frequency discriminator such as an optical filter with a linear edge, the optical field presents a new signal determined by the multiplication operation between the envelope function and the chirp function. Under a triangular drive signal, this process can contribute dark, bright and frequency-doubled bright parabolic waveforms by properly adjusting the filter window. This method is verified by both a theoretical analysis and experimental demonstrations. It not only provides a low-cost and simple scheme to generate parabola signals, but also a new method for arbitrary waveform generation.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"24 8","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139166155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-12-21DOI: 10.3390/photonics11010005
D. Hevisov, Dominik Reitzle, A. Liemert, A. Kienle
In this work, we introduce a novel variance reduction approach utilising the integral formulation of the radiative transfer equation to calculate the radiance in a planar symmetric slab geometry. Due to its integral nature, our method offers a fundamental advantage over well-established variance reduction methods such as the local estimate technique. As opposed to the local estimate procedure, photons add to the overall radiance not only at specific points of interaction but also throughout each consecutive path element; hence, our variance reduction approach can be thought of as an integral local estimate method. This facilitates a substantial enhancement in statistical efficiency, especially in scenarios where only a small number of scattering events or a high attenuation along the detection paths is to be anticipated. To evaluate the overall performance of the integral approach, we incorporated it into a self-developed GPU-accelerated Monte Carlo software, together with a conventional local estimate implementation adapted to slab geometry for a comprehensive comparison.
{"title":"An Integral-Equation-Based Variance Reduction Method for Accelerated Monte Carlo Simulations","authors":"D. Hevisov, Dominik Reitzle, A. Liemert, A. Kienle","doi":"10.3390/photonics11010005","DOIUrl":"https://doi.org/10.3390/photonics11010005","url":null,"abstract":"In this work, we introduce a novel variance reduction approach utilising the integral formulation of the radiative transfer equation to calculate the radiance in a planar symmetric slab geometry. Due to its integral nature, our method offers a fundamental advantage over well-established variance reduction methods such as the local estimate technique. As opposed to the local estimate procedure, photons add to the overall radiance not only at specific points of interaction but also throughout each consecutive path element; hence, our variance reduction approach can be thought of as an integral local estimate method. This facilitates a substantial enhancement in statistical efficiency, especially in scenarios where only a small number of scattering events or a high attenuation along the detection paths is to be anticipated. To evaluate the overall performance of the integral approach, we incorporated it into a self-developed GPU-accelerated Monte Carlo software, together with a conventional local estimate implementation adapted to slab geometry for a comprehensive comparison.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"61 12","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138950585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
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