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High-performance and ultra-wide bandwidth silicon TM polarizer with suppressed reflection utilizing a tailored contra-mode conversion Bragg grating

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OPTICS LETTERS 2024年第17期49卷 4995-4998页

作者： Wu, Shengbao Yu, Qianli Zhang, Lei Guo, Zhenzhao Xiao, Jinbiao Yao, X. Steve Hebei Univ Coll Phys Sci & Technol Photon Informat Innovat Ctr Hebei Prov Ctr Opt Sensing Innovat Baoding 071002 Peoples R China Southeast Univ Sch Elect Sci & Engn Natl Res Ctr Opt Sensing Commun Integrated Networ Nanjing 210096 Peoples R China

We present a compact TM polarizer with high polarization extinction ratio (PER), low loss, and suppressed reflection over an ultra-wide bandwidth on a 220nm silicon-on-insulator (SOI) platform. The device utilizes a contra-mode conversion Bragg grating (CMC-BG) with strong polarization dependence embedded in a multimode waveguide. Through a sophisticated grating design incorporating tailored chirping and apodization profiles to match modal properties, we have achieved, by simulation, a compact device footprint of 34.72x1.22 mu m(2) and an ultra-wide bandwidth of 346 nm with PER > 40 dB and an insertion loss (IL) < 1 dB, a 5-fold increase over our previous design. Particularly notable is the polarizer's ability to suppress reflection to <-15 dB across an extended bandwidth exceeding 450 nm. Experimental measurements confirm the excellent performance of the fabricated TM polarizer, with IL < 1.2 dB (0.5 dB) and PER > 30 dB over a bandwidth of 336 nm (268 nm). (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Chemical vapor deposition Effective refractive index Extinction ratios finite-difference time-domain method Polarization division multiplexing Transparent conducting oxides

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Terahertz polarization conversion and asymmetric transmission based on a liquid crystal integrated EIT metasurface

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OPTICS LETTERS 2024年第17期49卷 4891-4894页

作者： Xu, Shi-Tong Fan, Junxing Xue, Zhanqiang Li, Jiandi Wang, Ying-Hua Pan, Yue Cao, Hong-Zhong Ma, Ren-De Lu, Dan Zhang, Hui-Fang Cong, Longqing Qufu Normal Univ Sch Phys & Engn Shandong Prov Key Lab Laser Polarizat & Informat Qufu 273165 Shandong Peoples R China Southern Univ Sci & Technol Dept Elect & Elect Engn Shenzhen 518055 Peoples R China Univ Elect Sci & Technol China Shenzhen Inst Adv Study ShenSi Lab Shenzhen 518110 Peoples R China

We experimentally demonstrate a liquid crystal (LC)-integrated EIT metasurface for active THz polarization conversion and asymmetric transmission. By controlling the LC orientation under static magnetic field anchoring and an adjustable electric field, the device realizes the active control from the OFF state to theONstate, corresponding to the orthogonal polarization excitation modes of the EIT metasurface. Furthermore, based on the different polarization responses at forward and backward incidences, we achieve asymmetric transmission at the EIT peak and two nearby resonances, with its isolation actively manipulated by the external electric field. This study on dynamic polarization conversion and asymmetric transmission by a LC-integrated metasurface offers a promising route for active THz devices, applicable to THz communication, switching, and sensing systems. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： finite-difference time-domain method Fourier transforms Liquid crystals Numerical simulation Phase shift Ring resonators

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Optofluidic SERS based on Ag nanocubes with high sensitivity for detecting a prevalent water pollutant

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OPTICS LETTERS 2024年第10期49卷 2689-2692页

作者： Na, Ran Xing, Wang Yuan, Gan Jie, Zhang Chongqing Univ Key Lab Optoelect Technol & Syst Educ Minist China Chongqing 400044 Peoples R China

To enhance the integration and practical applicability of the Raman detection system, silver nanocubes (Ag NCs) were synthesized using a polyol method. A liquid-liquid interface approach was employed to transfer a monolayer of Ag NCs "film" onto a SiO 2 substrate, resulting in the fabrication of a highly sensitive and uniform surface -enhanced Raman scattering (SERS) substrate denoted as "Ag NCs@SiO 2 ." The electromagnetic field distribution of various dimers on the Ag NCs@SiO 2 was analyzed using finite difference time domain (FDTD) software. The results reveal that the electromagnetic enhancement effect is most pronounced in cube -cube dimers, indicating that Ag NCs exhibit superior localized surface plasmon resonance (LSPR) response due to their well-defined geometric regularity and sharp geo- metric angles. For Rhodamine 6G (R6G) probe molecules, the Ag NCs@SiO 2 shows ultrahigh sensitivity, with a limit of detection (LOD) of 10 -12 mol/L, and the enhancement factor (EF) can reach 1.4 x 10 10 . The relative standard devi- ation (RSD) at the main characteristic peaks is below 10%, demonstrating good consistency in substrate performance. In addition, the Ag NCs@SiO 2 modified with hexanethiol exhibits high sensitivity, uniformity, and repeatability in detecting for pyrene, with the LOD of 10 -8 mol/L and a min- imum RSD of 6.09% at the main characteristic peak, and effective recognition capabilities for pyrene and anthracene in mixed solutions. Finally, chemisorption and physisorption strategies were prepared in optofluidic channels and exper- imentally compared, enabling real-time detection of the pyrene solution. This method can achieve a rapid detection and precise differentiation of polycyclic aromatic hydrocar- bons in a water pollutant. (c) 2024 Optica Publishing Group

关键词： finite-difference time-domain method Localized surface plasmon resonance Metal nanoparticles Raman scattering Refractive index Scanning electron microscopy

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Deep-learning empowered unique and rapid optimization of meta-absorbers for solar thermophotovoltaics

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OPTICAL MATERIALS EXPRESS 2024年第4期14卷 1025-1038页

作者： Noureen, Sadia Ijaz, Sumbel Javed, Isma Cabrera, Humberto Zennaro, Marco Zubair, Muhammad Mehmood, Muhammad Qasim Massoud, Yehia Informat Technol Univ Punjab ITU Dept Elect Engn Lahore 54000 Pakistan Abdus Salam Int Ctr Theoret Phys Sci Technol & Innovat Unit MLAB I-34151 Trieste Italy Abdus Salam Int Ctr Theoret Phys Sci Technol & Innovat Unit I-34151 Trieste Italy King Abdullah Univ Sci & Technol KAUST Innovat Technol Labs ITL Thuwal Saudi Arabia

Optical nano -structure designs usually employ computationally expensive and timeintensive electromagnetic (EM) simulations that call for resorting to modern-day data -oriented methods, making design robust and quicker. A unique dataset and hybrid image processing model combining a CNN with gated recurrent units is presented to foresee the EM absorption response of photonic nano -structures. An inverse model is also discussed to predict the optimum geometry and dimensions of meta -absorbers. Mean -squared error of the order of 10 - 3 and an accuracy of 99% is achieved for trained models, and the average prediction time for the DL models is around 98% faster than that of simulations. This idea strengthens the proposition that efficient DL -based solutions can substitute the traditional methods for designing nano -optical structures. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Extinction coefficients finite-difference time-domain method Inverse design Neural networks Numerical simulation Optical imaging

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Improving the Light Harvest of Plasmonic Based Organic Solar Cells by Utilizing Dielectric Core-Shells

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PLASMONICS 2024年 1-13页

作者： Mulat, Simenew A. Hone, Fekadu G. Bekri, Nika Tegegne, Newayemedhin A. Addis Ababa Univ Dept Phys Addis Ababa 1176 Ethiopia Addis Ababa Sci & Technol Univ Dept Math Phys & Stat Addis Ababa 16417 Ethiopia Addis Ababa Sci & Technol Univ Sustainable Energy Ctr Excellence Addis Ababa 16417 Ethiopia Addis Ababa Sci & Technol Univ Nanotechnol Ctr Excellence Addis Ababa 16417 Ethiopia

The plasmonic properties of nanoparticles (NPs) such as silver (Ag) can be improved by utilizing core-shell materials in order to improve photon harvest in organic solar cells (OSCs). In this work, we utilized four dielectric materials, namely TiO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_2$$\end{document}, SnO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_2$$\end{document}, ZnO, and SiO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_2$$\end{document}, to improve the near-field and far-field enhancement in addition to pushing the LSPR of Ag NPs to the visible region. The plasmon-assisted photon harvesting in P3HT:PCBM-based inverted organic solar cell (OSC) devices was investigated using a 70 nm silver nanosphere (Ag NS) coated with dielectrics. This study employed a 3D finite-difference time-domain (FDTD) method for the analysis. The results show that the PCE of P3HT:PCBM could be enhanced by more than 26% when the NPs were embedded in the active layer due to the synergistic effect of near-field and far-field enhancement, with TiO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_2$$\end{document} that has a higher dielectric constant compared to others and bare Ag NPs. Furthermore, it was observed that backscattering as the dominant scatte

关键词： Plasmonic organic solar cells Dielectric coating finite-difference time-domain method Local surface plasmon resonances effect

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Computational simulation of multi-wavelength light-field thermometry based on a chromatic meta-lens

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OPTICS LETTERS 2024年第4期49卷 961-964页

作者： He, Yulun Shi, Shengxian Yao, Chunhui Zhao, Zhou Chen, Mu Ku Qi, Fei Shanghai Jiao Tong Univ Sch Mech Engn Shanghai 200240 Peoples R China City Univ Hong Kong Dept Elect Engn Hong Kong Peoples R China City Univ Hong Kong Ctr Biosyst Neurosci & Nanotechnol Hong Kong Peoples R China City Univ Hong Kong State Key Lab Terahertz & Millimeter Waves Hong Kong Peoples R China

This Letter proposes a light -field meta -lens multiwavelength thermometry (MMT) system that is capable of modulating a full -spectrum incident radiation into four separate wavelength beams. The chromatic meta -lens is designed using finite -difference time -domain (FDTD) software to function as a filter, ensuring its ability to separate four wavelengths. The chromatic meta -lens is positioned on the back focus plane of the main lens to replace the microlens used in traditional light -field systems and simplify the overall system. After detecting the acquired wavelengths and intensities of the image on photodiodes, a raw multispectral image can be decoupled and processed using the Chameleon swarm algorithm (CSA). Four full -spectrum incident radiations corresponding to four temperature characteristic curves are detected. The high accuracy of the reverse temperature calculation enables the measurement of surface high -temperature distribution with precision. (c) 2024 Optica Publishing Group

关键词： Computer simulation finite-difference time-domain method Microlens arrays Multispectral imaging Optical systems Surface measurements

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Impacts of p-GaN layer thickness on the photoelectric and thermal performance of AlGaN-based deep-UV LEDs

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OPTICS EXPRESS 2023年第22期31卷 36547-36556页

作者： Li, Saijun Shen, Meng-Chun Lai, Shouqiang Dai, Yurong Chen, Jinlan Zheng, Lijie Zhu, Lihong Chen, Guolong Lin, Su-Hui Peng, Kang-Wei Chen, Zhong Wu, Tingzhu Xiamen Univ Fujian Engn Res Ctr Solid State Lighting Dept Elect Sci Xiamen 361005 Peoples R China Xiamen Univ Dept Elect Sci Natl Integrated Circuit Ind & Educ Integrat Innova Xiamen 361005 Peoples R China

The effects of different p-GaN layer thickness on the photoelectric and thermal properties of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were investigated. The results revealed that appropriate thinning of the p-GaN layer enhances the photoelectric performance and thermal stability of DUV-LEDs, reducing current crowding effects that affect the external quantum efficiency and chip heat dissipation. The ABC +f (n) model was used to analyse the EQE, which helped in identifying the different physical mechanisms for DUV-LEDs with different p-GaN layer thickness. Moreover, the finite difference time domain simulation results revealed that the light-extraction efficiency of the DUV-LEDs exhibits a trend similar to that of damped vibration as the thickness of the p-GaN layer increases. The AlGaN-based DUV-LED with a p-GaN layer thickness of 20 nm exhibited the best photoelectric characteristics and thermal stability.

关键词： finite-difference time-domain method Light extraction Light sources Quantum efficiency Thin films Ultraviolet light emitting diodes

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Optical properties estimation of photonic crystal fiber using Gaussian process regression

OPTICS CONTINUUM

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OPTICS CONTINUUM 2024年第8期3卷 1369-1388页

作者： Kaium, S. K. Md Abdul Mollah, Md Aslam Rajshahi Univ Engn & Technol Dept Elect & Telecommun Engn Rajshahi 6204 Bangladesh

In contrast to typical optical fiber, photonic crystal fiber (PCF) exhibits a variety of unique optical properties as a result of its flexible cladding distribution. Nonetheless, assessing PCF optical characteristics becomes difficult when structural parameters fluctuate. This issue is a serious impediment to fully understanding and leveraging PCF's potential for diverse optical applications. Furthermore, the variety in structural factors makes it difficult to ensure PCF's consistent and reliable performance in practical optical systems. Artificial neural networks (ANN) are widely used to forecast the optical parameters of PCF. However, ANNs have issues when dealing with local minima. In contrast, solutions obtained from support vector machines regressions (SVM/SVR), Gaussian process regressions (GPR), and k-nearest neighbors regression (KNNR) are globally unique and avoid the dangers of slipping into local minimum values. Major properties such as effective refractive index (neff), n eff ), confinement loss (alpha c) alpha c ) and dispersion (D) D ) of photonic crystal fiber (PCF) were predicted using SVM/SVR, GPR, KNNR, random forest regression (RFR), gradient boosting regression (GBR), and ANN. To evaluate the performance of various regression algorithms, we created a database of 2912 samples including the X and Y directions. In terms of prediction accuracy and stability, SVM and GPR outperform other approaches.

关键词： Effective refractive index finite-difference time-domain method Hollow core fibers Inverse design Optical systems Tilted fiber Bragg gratings

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High-sensitivity complex refractive index sensing using Fano resonance based on a side-coupled slotted photonic crystal nanobeam cavity

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APPLIED OPTICS 2025年第14期64卷 4106-4113页

作者： Huang, Ji-Wei Li, Bo-Xun Deng, Chao-Sheng Xiangtan Univ Sch Phys & Optoelect Xiangtan 411105 Peoples R China

We propose an optical sensor comprising a straight waveguide integrated with a partial transmitting element and a side-coupled slotted photonic crystal nanobeam cavity (SPCNC) for complex refractive index sensing (CRI) in gaseous environments. The coherent interaction between the continuous state in the waveguide and the discrete state in the SPCNC generates a sharp and asymmetric Fano resonance lineshape in the transmission spectrum. Through systematic structural optimization and rigorous three-dimensional finite-difference time-domain simulations, the proposed sensor achieves exceptional sensitivities of 518 nm/RIU for the real refractive index and 16750 RIU-1 for the imaginary refractive index in CRI sensing. Furthermore, the impact of fabrication disorder on the sensing performance is investigated and evaluated. The proposed sensor demonstrates significant potential for applications in multi-parameter sensing and multi-component mixture detection. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Fano resonance finite-difference time-domain method Photonic crystal cavities Plasmon waveguides Ring resonators Waveguide modes

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Sensitivity enhancement of the LSPR-based tapered optical fiber biosensor by variation of nanoparticle arrangement

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2023年第11期40卷 2968-2978页

作者： Borjikhani, Parisa Zibaii, Mohammad Ismail Granpayeh, Nosrat Khajeh Nasir Toosi Univ Technol Fac Elect Engn Ctr Excellence Electromagnet Opt Commun Lab Tehran Iran Shahid Beheshti Univ Laser & Plasma Res Inst Tehran Iran

A tapered optical fiber sensor with four arrangements of gold nanoparticles (Au NPs) on its waist is simulated and the fiber transmittance by changing the analyte refractive index (RI) is obtained. The method is a combination of the finite-difference time-domain method and the finite element method. The effect of NPs on top of each other and dimers is investigated, which is the first step in studying the aggregation of NPs in the cluster NP model. In addition, the effects of fiber diameter, NP diameter, and fiber length are examined. It is shown that by variation of NP arrangement, the amplitude sensitivity increases from 1.5 per refractive index unit (RIU-1) to 4.53 RIU-1 and the wavelength sensitivity increases from 58.24 to 116.74 nm/RIU. The dimensions of the structures and the ranges of analyte RIs are in the field of practical biosensors, to be close to reality and to be effective in diagnosing diseases. (c) 2023 Optica Publishing Group

关键词： Fiber optic sensors finite element method finite-difference time-domain method Long period fiber gratings Tapered fibers Tilted fiber Bragg gratings

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