Pub Date : 2025-02-21DOI: 10.1021/acsphotonics.4c02518
Huaqing Qiu, Mathias Prost, David Coenen, Tangla David Kongnyuy, Manuel Reza, Guillaume Croes, Maliheh Ramezani, Puvendren Subramaniam, Herman Oprins, Hao Hu, Joost Brouckaert, Roelof Jansen, Marcus Dahlem
Thermo-optic phase shifters are crucial components extensively utilized in large-scale photonic integrated circuits due to their simple design and well-established fabrication processes. The requirement for negligible insertion loss in low-power-consumption thermo-optic phase shifters is becoming increasingly critical, particularly in cascaded configurations employed in applications such as LiDAR, photonic computing, programmable photonics, and quantum photonics. To address this need, we present a comprehensive theory based on the fundamental coupled-mode theory for sharp-bent waveguides. We employ phase mismatch in a compact spiral waveguide to eliminate coupling loss and enhance the efficiency of thermo-optic phase shifters. Our approach successfully overcomes inherent trade-offs, demonstrating ultralow insertion loss in compact and power-efficient silicon-based phase shifters operating in the C-band. The proposed simplest-design device exhibits a record lowest measured insertion loss of 0.14 dB among all residual-heat-absorption-type phase shifters. Simultaneously, the power consumption and modulation bandwidth are measured to be 3.4 mW/π and 12.5 kHz, respectively. This methodology holds substantial promise for minimizing the insertion loss across various residual-heat-absorption-type thermo-optic phase shifters, which employ different materials and operate in diverse bands, such as the telecom and visible spectra. The experimental realization of the C-band silicon phase shifter on IMEC’s Si/SiN platform expresses its potential as a fundamental component for scalable mass production in extensive photonic circuit architectures.
{"title":"Ultralow Loss Design Methodology for Energy-Efficient Thermo-Optic Phase Shifters","authors":"Huaqing Qiu, Mathias Prost, David Coenen, Tangla David Kongnyuy, Manuel Reza, Guillaume Croes, Maliheh Ramezani, Puvendren Subramaniam, Herman Oprins, Hao Hu, Joost Brouckaert, Roelof Jansen, Marcus Dahlem","doi":"10.1021/acsphotonics.4c02518","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c02518","url":null,"abstract":"Thermo-optic phase shifters are crucial components extensively utilized in large-scale photonic integrated circuits due to their simple design and well-established fabrication processes. The requirement for negligible insertion loss in low-power-consumption thermo-optic phase shifters is becoming increasingly critical, particularly in cascaded configurations employed in applications such as LiDAR, photonic computing, programmable photonics, and quantum photonics. To address this need, we present a comprehensive theory based on the fundamental coupled-mode theory for sharp-bent waveguides. We employ phase mismatch in a compact spiral waveguide to eliminate coupling loss and enhance the efficiency of thermo-optic phase shifters. Our approach successfully overcomes inherent trade-offs, demonstrating ultralow insertion loss in compact and power-efficient silicon-based phase shifters operating in the C-band. The proposed simplest-design device exhibits a record lowest measured insertion loss of 0.14 dB among all residual-heat-absorption-type phase shifters. Simultaneously, the power consumption and modulation bandwidth are measured to be 3.4 mW/π and 12.5 kHz, respectively. This methodology holds substantial promise for minimizing the insertion loss across various residual-heat-absorption-type thermo-optic phase shifters, which employ different materials and operate in diverse bands, such as the telecom and visible spectra. The experimental realization of the C-band silicon phase shifter on IMEC’s Si/SiN platform expresses its potential as a fundamental component for scalable mass production in extensive photonic circuit architectures.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"13 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143470958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
One-shot spectral imaging has been a hot research topic recently, with primary challenges in the efficient fabrication techniques of encoded masks and high-speed, high-accuracy algorithms for real-time imaging. We introduce a real-time hyperspectral imager that leverages multilayer thin film microfilters and the Massively Parallel Network (MP-Net). Each curved microfilter uniquely modulates incident light across the underlying 3 × 3 CMOS pixels, thereby rendering each pixel an efficient spectral encoder. MP-Net, specially designed to address transmittance variability and manufacturing errors such as misalignment and nonuniformities in thin film deposition, greatly increase the robustness to fabrication errors. A spectral resolution of 2.19 nm is achieved for monochromatic spectra. Tested in varied environments on both static and moving objects, the imager demonstrates high-fidelity spatial-spectral data reconstruction capabilities with a maximum imaging frame rate exceeding 30 fps. This hyperspectral imager represents a significant advancement in real-time, high-resolution spectral imaging, offering a versatile solution for applications ranging from remote sensing to consumer electronics.
{"title":"Real-time Hyperspectral Imager with High Spatial-Spectral Resolution Enabled by Massively Parallel Neural Network","authors":"Junren Wen, Haiqi Gao, Weiming Shi, Shuaibo Feng, Lingyun Hao, Yujie Liu, Liang Xu, Yuchuan Shao, Yueguang Zhang, Weidong Shen, Chenying Yang","doi":"10.1021/acsphotonics.4c02003","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c02003","url":null,"abstract":"One-shot spectral imaging has been a hot research topic recently, with primary challenges in the efficient fabrication techniques of encoded masks and high-speed, high-accuracy algorithms for real-time imaging. We introduce a real-time hyperspectral imager that leverages multilayer thin film microfilters and the Massively Parallel Network (MP-Net). Each curved microfilter uniquely modulates incident light across the underlying 3 × 3 CMOS pixels, thereby rendering each pixel an efficient spectral encoder. MP-Net, specially designed to address transmittance variability and manufacturing errors such as misalignment and nonuniformities in thin film deposition, greatly increase the robustness to fabrication errors. A spectral resolution of 2.19 nm is achieved for monochromatic spectra. Tested in varied environments on both static and moving objects, the imager demonstrates high-fidelity spatial-spectral data reconstruction capabilities with a maximum imaging frame rate exceeding 30 fps. This hyperspectral imager represents a significant advancement in real-time, high-resolution spectral imaging, offering a versatile solution for applications ranging from remote sensing to consumer electronics.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"58 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143470957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Due to the absence of known polynomial-time algorithms, NP-complete (NPC) problems, such as the subset sum problem (SSP), pose a significant challenge for electronic computers. Optical approaches, known for their inherent parallelism, low latency, and reduced power consumption, present a promising alternative. However, existing diffractive networks (DNNs) are limited to achieving only polynomial-level parallelism. In this work, we introduce an SSP solver that achieves exponential parallelism, allowing the SSP problem to be solved within polynomial time (volume). By using beam splitting in a synthetic polarization dimension to maintain a single localized optical spot and encoding spatial frequencies onto this spot, the solutions can be successfully searched in parallel. Moreover, unlike other spatial optical computing systems that require substantial thickness due to overlapping nonlocality (ONL), our system can remain remarkably thin. This thinness enables the addition of more layers without increasing the overall size, facilitating efficient 3D stacking. We have conducted a proof-of-principle experimental demonstration and discussed the advantages of our method over other state-of-the-art solutions. This work lays a strong foundation for the exploration of novel paradigms to fully utilize the parallelism of optical computing.
{"title":"Photonic NP-Complete Problem Solver Enabled by Local Spatial Frequency Encoding","authors":"Xueyi Jiang, Shiji Zhang, Bo Wu, Hailong Zhou, Zhichao Ruan, Jianji Dong, Xinliang Zhang","doi":"10.1021/acsphotonics.4c01795","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c01795","url":null,"abstract":"Due to the absence of known polynomial-time algorithms, NP-complete (NPC) problems, such as the subset sum problem (SSP), pose a significant challenge for electronic computers. Optical approaches, known for their inherent parallelism, low latency, and reduced power consumption, present a promising alternative. However, existing diffractive networks (DNNs) are limited to achieving only polynomial-level parallelism. In this work, we introduce an SSP solver that achieves exponential parallelism, allowing the SSP problem to be solved within polynomial time (volume). By using beam splitting in a synthetic polarization dimension to maintain a single localized optical spot and encoding spatial frequencies onto this spot, the solutions can be successfully searched in parallel. Moreover, unlike other spatial optical computing systems that require substantial thickness due to overlapping nonlocality (ONL), our system can remain remarkably thin. This thinness enables the addition of more layers without increasing the overall size, facilitating efficient 3D stacking. We have conducted a proof-of-principle experimental demonstration and discussed the advantages of our method over other state-of-the-art solutions. This work lays a strong foundation for the exploration of novel paradigms to fully utilize the parallelism of optical computing.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"25 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143452121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-02-19DOI: 10.1021/acsphotonics.4c02361
Yuzhuo Pei, Chuang Wang, Jing Qin, Ye Tong, Ran Wei, Yishi Weng, Feng Liu, Wei Quan, Zhen Chai, Yuning Zhang
Ultraweak magnetic field measurement, as one of the quantum precision measurement techniques, holds important significance in the forefront of explorations in physics and advanced medical technologies. The atomic magnetometer, serving as a typical instrument for measuring extremely weak magnetic fields, utilizes the Larmor precession frequency of electrons in alkali metal atoms to quantify magnetic field magnitudes at subfemtotesla levels. Additionally, atomic magnetometers boast advantages such as high sensitivity, miniaturization and high spatial resolution. Hence, arrays of atomic magnetometer sensors have become a reliable solution for measuring ultraweak magnetic fields in spatial dimensions. This paper proposes an ultracompact and highly sensitive atomic magnetometer array integrated structure via a highly stable polarization volume grating (PVG)-based waveguide structure for beam splitting. Instead of the traditional four polarizing beam splitters and polarizors, the structure integrates parallel beam splitting and polarization conversion functions using PVGs, which are then incorporated into an ultracompact atomic magnetometer array. This integration enables high sensitivity magnetic field measurements in four channels. The light separated by the structure exhibits power fluctuations along a single polarization axis below 0.2% during a 30 min period. The overall volume of the proposed integrated structure is approximately 0.6 cm3, representing at least an order of magnitude reduction compared to other spatial optical atomic magnetometer array structures. The final validation demonstrates the system can measure magnetic fields on the order of femtotesla, with an average sensitivity of 16.1 fT/Hz1/2. This approach holds significant potential for applications in quantum precision sensing, high resolution medical imaging, and biological science exploration.
{"title":"Ultracompact and Highly Sensitive Atomic Magnetometer Array via a Polarization Volume Grating-Based Waveguide Structure","authors":"Yuzhuo Pei, Chuang Wang, Jing Qin, Ye Tong, Ran Wei, Yishi Weng, Feng Liu, Wei Quan, Zhen Chai, Yuning Zhang","doi":"10.1021/acsphotonics.4c02361","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c02361","url":null,"abstract":"Ultraweak magnetic field measurement, as one of the quantum precision measurement techniques, holds important significance in the forefront of explorations in physics and advanced medical technologies. The atomic magnetometer, serving as a typical instrument for measuring extremely weak magnetic fields, utilizes the Larmor precession frequency of electrons in alkali metal atoms to quantify magnetic field magnitudes at subfemtotesla levels. Additionally, atomic magnetometers boast advantages such as high sensitivity, miniaturization and high spatial resolution. Hence, arrays of atomic magnetometer sensors have become a reliable solution for measuring ultraweak magnetic fields in spatial dimensions. This paper proposes an ultracompact and highly sensitive atomic magnetometer array integrated structure via a highly stable polarization volume grating (PVG)-based waveguide structure for beam splitting. Instead of the traditional four polarizing beam splitters and polarizors, the structure integrates parallel beam splitting and polarization conversion functions using PVGs, which are then incorporated into an ultracompact atomic magnetometer array. This integration enables high sensitivity magnetic field measurements in four channels. The light separated by the structure exhibits power fluctuations along a single polarization axis below 0.2% during a 30 min period. The overall volume of the proposed integrated structure is approximately 0.6 cm<sup>3</sup>, representing at least an order of magnitude reduction compared to other spatial optical atomic magnetometer array structures. The final validation demonstrates the system can measure magnetic fields on the order of femtotesla, with an average sensitivity of 16.1 fT/Hz<sup>1/2</sup>. This approach holds significant potential for applications in quantum precision sensing, high resolution medical imaging, and biological science exploration.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"22 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143452124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
Single color centers in wide bandgap materials show great potential for various quantum applications. However, most of the well-known single color centers are in diamond and silicon carbide, which are difficult to use for fabricating photonic structures. Thus, it is essential to find new single defects in materials that are compatible with well-established, industrial-scale nano- or microfabrication of photonic structures. Here, we report a method to generate stable single-photon emitters in silica. The spectra of these single-photon emitters show a strong zero-phonon line, and the Debye–Waller factors (FDW) were measured up to 0.74. The power-dependent photon autocorrelation results demonstrate a strong bunching effect at high excitation power, and the results can be described by a standard three-level system model. The photoluminescence (PL) emission polarization, saturation intensity, and stability of these single-photon emitters are also investigated.
{"title":"Stable Single Photon Emitters with Large Debye–Waller Factor in Silica","authors":"Yu-Chen Chen, Shih-Chu Lin, Jyh-Pin Chou, Ya-Ching Tsai, Chiao-Tzu Huang, Chien-Ju Lee, Wen-Hao Chang","doi":"10.1021/acsphotonics.4c02001","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c02001","url":null,"abstract":"Single color centers in wide bandgap materials show great potential for various quantum applications. However, most of the well-known single color centers are in diamond and silicon carbide, which are difficult to use for fabricating photonic structures. Thus, it is essential to find new single defects in materials that are compatible with well-established, industrial-scale nano- or microfabrication of photonic structures. Here, we report a method to generate stable single-photon emitters in silica. The spectra of these single-photon emitters show a strong zero-phonon line, and the Debye–Waller factors (<i>F</i><sub><i>DW</i></sub>) were measured up to 0.74. The power-dependent photon autocorrelation results demonstrate a strong bunching effect at high excitation power, and the results can be described by a standard three-level system model. The photoluminescence (PL) emission polarization, saturation intensity, and stability of these single-photon emitters are also investigated.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"50 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143452122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-02-19DOI: 10.1021/acsphotonics.5c00027
Romain Quidant
As 2025 begins, this is a fitting time for <i>ACS Photonics</i> to celebrate its achievements in 2024 and outline some key updates for the year ahead. This past year has been a period of significant growth for the journal, marked by a substantial increase in submissions. The editorial team extends its sincere gratitude to all our contributors for their continued trust in <i>ACS Photonics</i>. This surge in submissions underscores the journal’s position at the forefront of photonics research, encompassing an ever-widening range of topics. Absorbing this substantial growth would not be possible without the dedication of our reviewer pool, who ensure timely and expert assessments. We warmly thank them for their unvaluable contribution. We would like to express our deepest appreciation to Professor Jelena Vuckovic from Stanford University for her invaluable editorial contributions to <i>ACS Photonics</i> over the past 7 years. It has been an absolute pleasure to collaborate with Jelena. We will deeply miss her exceptional professionalism and warm personality. We wholeheartedly wish her the very best in her new role as Lead Editor of <i>Physical Review Applied</i> at APS. Departures always present opportunities for new beginnings, and we are thrilled to warmly welcome Professor Arka Majumdar from the University of Washington as our newest Associate Editor. Professor Majumdar will be overseeing submissions in the critical areas of integrated optics, AI for photonics and photonics for AI, and quantum photonics. We are delighted to have him join our editorial team. The close of this year also coincides with the renewal of our Editorial Advisory Board (EAB). This distinguished panel, comprising leading experts from across the globe in diverse fields of photonics, provides invaluable guidance and support to the editorial team. We extend our sincere thanks to all outgoing EAB members and warmly welcome our new appointees. Recognizing the vital contributions of the next generation of researchers, <i>ACS Photonics</i> is proud to announce the establishment of an Early Career Advisory Board (ECAB). Composed of six exceptional early career researchers representing the United States, Spain, and China, this board boasts a 1:1 gender ratio and will play a crucial role in shaping the future direction of the journal. Following the recent launch of the new Photonics Roadmap manuscript type, we have published this year our first Roadmap for optical metasurfaces, which, not only highlights the field’s significant achievements but also outlines emerging and future directions that will steer future scientific and technological advancements. A second Roadmap, dedicated to 2D materials for photonics, is currently in preparation. Finally, Professor Letian Dou, Charles Davidson Associate Professor of Chemical Engineering and Chemistry at Purdue University, has been named the recipient of the 2025 ACS Photonics Young Investigator Award. This prestigious award honors the outst
{"title":"New Year Editorial","authors":"Romain Quidant","doi":"10.1021/acsphotonics.5c00027","DOIUrl":"https://doi.org/10.1021/acsphotonics.5c00027","url":null,"abstract":"As 2025 begins, this is a fitting time for <i>ACS Photonics</i> to celebrate its achievements in 2024 and outline some key updates for the year ahead. This past year has been a period of significant growth for the journal, marked by a substantial increase in submissions. The editorial team extends its sincere gratitude to all our contributors for their continued trust in <i>ACS Photonics</i>. This surge in submissions underscores the journal’s position at the forefront of photonics research, encompassing an ever-widening range of topics. Absorbing this substantial growth would not be possible without the dedication of our reviewer pool, who ensure timely and expert assessments. We warmly thank them for their unvaluable contribution. We would like to express our deepest appreciation to Professor Jelena Vuckovic from Stanford University for her invaluable editorial contributions to <i>ACS Photonics</i> over the past 7 years. It has been an absolute pleasure to collaborate with Jelena. We will deeply miss her exceptional professionalism and warm personality. We wholeheartedly wish her the very best in her new role as Lead Editor of <i>Physical Review Applied</i> at APS. Departures always present opportunities for new beginnings, and we are thrilled to warmly welcome Professor Arka Majumdar from the University of Washington as our newest Associate Editor. Professor Majumdar will be overseeing submissions in the critical areas of integrated optics, AI for photonics and photonics for AI, and quantum photonics. We are delighted to have him join our editorial team. The close of this year also coincides with the renewal of our Editorial Advisory Board (EAB). This distinguished panel, comprising leading experts from across the globe in diverse fields of photonics, provides invaluable guidance and support to the editorial team. We extend our sincere thanks to all outgoing EAB members and warmly welcome our new appointees. Recognizing the vital contributions of the next generation of researchers, <i>ACS Photonics</i> is proud to announce the establishment of an Early Career Advisory Board (ECAB). Composed of six exceptional early career researchers representing the United States, Spain, and China, this board boasts a 1:1 gender ratio and will play a crucial role in shaping the future direction of the journal. Following the recent launch of the new Photonics Roadmap manuscript type, we have published this year our first Roadmap for optical metasurfaces, which, not only highlights the field’s significant achievements but also outlines emerging and future directions that will steer future scientific and technological advancements. A second Roadmap, dedicated to 2D materials for photonics, is currently in preparation. Finally, Professor Letian Dou, Charles Davidson Associate Professor of Chemical Engineering and Chemistry at Purdue University, has been named the recipient of the 2025 ACS Photonics Young Investigator Award. This prestigious award honors the outst","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"29 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-02-19DOI: 10.1021/acsphotonics.4c02194
Iridanos Loulas, Evangelos Almpanis, Minas Kouroublakis, Kosmas L. Tsakmakidis, Carsten Rockstuhl, Grigorios P. Zouros
We develop a full-wave electromagnetic (EM) theory for calculating the multipole decomposition in two-dimensional (2-D) structures consisting of isolated, arbitrarily shaped, inhomogeneous, anisotropic cylinders or a collection of such. To derive the multipole decomposition, we first solve the scattering problem by expanding the scattered electric field in divergenceless cylindrical vector wave functions (CVWFs) with unknown expansion coefficients that characterize the multipole response. These expansion coefficients are then expressed via contour integrals of the vectorial components of the scattered electric field evaluated via an electric field volume integral equation (EFVIE). The kernels of the EFVIE are the products of the tensorial 2-D Green’s function (GF) expansion and the equivalent 2-D volumetric electric and magnetic current densities. We validate the theory using the commercial finite element solver COMSOL Multiphysics. In the validation, we compute the multipole decomposition of the fields scattered from various 2-D structures and compare the results with alternative formulations. Finally, we demonstrate the applicability of the theory to study an emerging photonics application on oligomer-based highly directional switching using active media. This analysis addresses a critical gap in the current literature, where multipole theories exist primarily for three-dimensional (3-D) particles of isotropic materials. Our work enhances the understanding and utilization of the optical properties of 2-D, inhomogeneous, and anisotropic cylindrical structures, contributing to advancements in photonic and meta-optics technologies.
{"title":"Electromagnetic Multipole Theory for Two-Dimensional Photonics","authors":"Iridanos Loulas, Evangelos Almpanis, Minas Kouroublakis, Kosmas L. Tsakmakidis, Carsten Rockstuhl, Grigorios P. Zouros","doi":"10.1021/acsphotonics.4c02194","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c02194","url":null,"abstract":"We develop a full-wave electromagnetic (EM) theory for calculating the multipole decomposition in two-dimensional (2-D) structures consisting of isolated, arbitrarily shaped, inhomogeneous, anisotropic cylinders or a collection of such. To derive the multipole decomposition, we first solve the scattering problem by expanding the scattered electric field in divergenceless cylindrical vector wave functions (CVWFs) with unknown expansion coefficients that characterize the multipole response. These expansion coefficients are then expressed via contour integrals of the vectorial components of the scattered electric field evaluated via an electric field volume integral equation (EFVIE). The kernels of the EFVIE are the products of the tensorial 2-D Green’s function (GF) expansion and the equivalent 2-D volumetric electric and magnetic current densities. We validate the theory using the commercial finite element solver COMSOL Multiphysics. In the validation, we compute the multipole decomposition of the fields scattered from various 2-D structures and compare the results with alternative formulations. Finally, we demonstrate the applicability of the theory to study an emerging photonics application on oligomer-based highly directional switching using active media. This analysis addresses a critical gap in the current literature, where multipole theories exist primarily for three-dimensional (3-D) particles of isotropic materials. Our work enhances the understanding and utilization of the optical properties of 2-D, inhomogeneous, and anisotropic cylindrical structures, contributing to advancements in photonic and meta-optics technologies.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"14 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-02-18DOI: 10.1021/acsphotonics.4c02257
Andrey Krayev, Eleonora Isotta, Lauren Hoang, Jerry A. Yang, Kathryn Neilson, Minyuan Wang, Noah Haughn, Eric Pop, Andrew Mannix, Oluwaseyi Balogun, Chih-Feng Wang
In this work, we present a systematic study of the dependence of the gap-mode tip-enhanced Raman scattering (TERS) response of the mono- and bilayer WS2 and MoS2 on silver as a function of the excitation laser energy in a broad spectral range from 473 to 830 nm. For this purpose, we collected consecutive TERS maps of the same area in the sample containing mono- and bilayer regions with the same TERS probe with 6 different excitation lasers. To decrease the number of collected TERS maps, we used for the first time, to the best of our knowledge, concurrent excitation and collection with two lasers simultaneously. We found that the E2g/A1g peak intensity ratio for the bilayer WS2@Ag and the ratio of the A′/A1g peak intensity of the out-of-plane mode for the mono- and the bilayer change in a significantly nonmonotonous way as the excitation laser energy is swept from 1.58 to 2.62 eV. The former ratio increases at energies corresponding to A and B excitons (∼2.0 and 2.4 eV, respectively) in bilayer WS2. The absolute intensity of the A′ peak in the monolayer, and correspondingly the A′/A1g ratio, is surprisingly high at lower excitation energies but dips dramatically at the energy corresponding to the A exciton, being restored partially in between A and B excitons, but still showing the descending trend as the excitation laser energy increases. A somewhat similar picture was observed in mono- and bilayers of MoS2@Ag, though the existing set of excitation lasers did not match the excitonic profile of this material as nicely as for the case of WS2. We attribute the observed behavior to the presence of intermediate (Fano resonance) or strong (Rabi splitting) coupling between the excitons in transition metal dichalcogenides (TMDs) and the plasmons in the tip–substrate nanocavity. This is akin to the so-called “Fano” (Rabi) transparency experimentally observed in far-field scattering from TMDs between two plasmonic metals. The possibility of the formation of intermediate/strong coupling between the excitonic resonances in TMDs and the nanocavity reevaluates the role of various resonances in gap-mode TERS, and should become an important factor to be considered by TERS practitioners during experiment planning. Finally, based on the observed phenomena and their explanation, we propose the “ideal” substrate for efficient TERS and tip-enhanced photoluminescence (TEPL) measurements.
{"title":"Excitation Laser Energy Dependence of the Gap-Mode TERS Spectra of WS2 and MoS2 on Silver","authors":"Andrey Krayev, Eleonora Isotta, Lauren Hoang, Jerry A. Yang, Kathryn Neilson, Minyuan Wang, Noah Haughn, Eric Pop, Andrew Mannix, Oluwaseyi Balogun, Chih-Feng Wang","doi":"10.1021/acsphotonics.4c02257","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c02257","url":null,"abstract":"In this work, we present a systematic study of the dependence of the gap-mode tip-enhanced Raman scattering (TERS) response of the mono- and bilayer WS<sub>2</sub> and MoS<sub>2</sub> on silver as a function of the excitation laser energy in a broad spectral range from 473 to 830 nm. For this purpose, we collected consecutive TERS maps of the same area in the sample containing mono- and bilayer regions with the same TERS probe with 6 different excitation lasers. To decrease the number of collected TERS maps, we used for the first time, to the best of our knowledge, concurrent excitation and collection with two lasers simultaneously. We found that the E<sub>2g</sub>/A<sub>1g</sub> peak intensity ratio for the bilayer WS<sub>2</sub>@Ag and the ratio of the A′/A<sub>1g</sub> peak intensity of the out-of-plane mode for the mono- and the bilayer change in a significantly nonmonotonous way as the excitation laser energy is swept from 1.58 to 2.62 eV. The former ratio increases at energies corresponding to A and B excitons (∼2.0 and 2.4 eV, respectively) in bilayer WS<sub>2</sub>. The absolute intensity of the A′ peak in the monolayer, and correspondingly the A′/A<sub>1g</sub> ratio, is surprisingly high at lower excitation energies but dips dramatically at the energy corresponding to the A exciton, being restored partially in between A and B excitons, but still showing the descending trend as the excitation laser energy increases. A somewhat similar picture was observed in mono- and bilayers of MoS<sub>2</sub>@Ag, though the existing set of excitation lasers did not match the excitonic profile of this material as nicely as for the case of WS<sub>2</sub>. We attribute the observed behavior to the presence of intermediate (Fano resonance) or strong (Rabi splitting) coupling between the excitons in transition metal dichalcogenides (TMDs) and the plasmons in the tip–substrate nanocavity. This is akin to the so-called “Fano” (Rabi) transparency experimentally observed in far-field scattering from TMDs between two plasmonic metals. The possibility of the formation of intermediate/strong coupling between the excitonic resonances in TMDs and the nanocavity reevaluates the role of various resonances in gap-mode TERS, and should become an important factor to be considered by TERS practitioners during experiment planning. Finally, based on the observed phenomena and their explanation, we propose the “ideal” substrate for efficient TERS and tip-enhanced photoluminescence (TEPL) measurements.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"16 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-02-18DOI: 10.1021/acsphotonics.4c01962
Michael Davino, Tobias Saule, Nora G. Helming, Carlos A. Trallero-Herrero
Strong-field physics has been at the forefront of scientific research for multiple decades, mainly focusing on atoms and molecules, and only recently becoming focused on nanoparticles and solids. Recent developments in nanotechnology pushed this research to more complex systems, where the distinction of ionization regimes via the Keldysh parameter is insufficient. Here we report on pulse duration-dependent strong-field ionization of dielectric nanoparticles at low intensities. We find that despite the inverse relation to field intensity, increasing the pulse duration results in an increased photoelectron cutoff energy. This cutoff energy enhancement is seen both in absolute energy (units of eV) and when represented in terms of the ponderomotive potential. Further, our findings implicate nonsequential ionization as being the dominant underlying mechanism to this observation. In this new regime of strong field science, the intuitive approach of higher peak intensity yielding a higher photoelectron cutoff no longer applies. Furthermore, comparable results are found for ionization by circularly polarized fields, indicating that recollision is not significantly suppressed in nanoparticles as it is in atoms and molecules.
{"title":"Extreme Pulse Duration Scaling of Strong Field Ionization of Nanoparticles","authors":"Michael Davino, Tobias Saule, Nora G. Helming, Carlos A. Trallero-Herrero","doi":"10.1021/acsphotonics.4c01962","DOIUrl":"https://doi.org/10.1021/acsphotonics.4c01962","url":null,"abstract":"Strong-field physics has been at the forefront of scientific research for multiple decades, mainly focusing on atoms and molecules, and only recently becoming focused on nanoparticles and solids. Recent developments in nanotechnology pushed this research to more complex systems, where the distinction of ionization regimes via the Keldysh parameter is insufficient. Here we report on pulse duration-dependent strong-field ionization of dielectric nanoparticles at low intensities. We find that despite the inverse relation to field intensity, increasing the pulse duration results in an increased photoelectron cutoff energy. This cutoff energy enhancement is seen both in absolute energy (units of eV) and when represented in terms of the ponderomotive potential. Further, our findings implicate nonsequential ionization as being the dominant underlying mechanism to this observation. In this new regime of strong field science, the intuitive approach of higher peak intensity yielding a higher photoelectron cutoff no longer applies. Furthermore, comparable results are found for ionization by circularly polarized fields, indicating that recollision is not significantly suppressed in nanoparticles as it is in atoms and molecules.","PeriodicalId":23,"journal":{"name":"ACS Photonics","volume":"64 1","pages":""},"PeriodicalIF":7.0,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：