Pub Date : 2024-07-25DOI: 10.1088/2040-8986/ad645a
Miguel A Porras
Advances in the generation and the application of spatiotemporal optical vortices (STOV) are proceeding fast, but fundamental aspects of their nature remain obscure. Bliokh (2023 Phys. Rev. A 107 L031501) (PRA) and Porras (2023 Prog. Electromagn. Res.177 95) (PIER) provide contradictory results on the transverse orbital angular momentum (OAM) carried by STOVs. We show that the results by Porras in PIER and by Bliokh in PRA refer to different STOVs and are all correct. In PIER, STOVs are elliptical at given cross section and time, or in space-time, but not in three-dimensional space. In PRA, STOVs are elliptical in space but not in space-time. This is evidenced from two dual, equivalent theories on the transverse OAM where a wave packet is seen in space-time evolving with propagation distance or in space evolving in time, that account for all values of the total, intrinsic and extrinsic OAM in PIERS and PRA. However, the intrinsic OAM with respect to the photon wave function center in PRA is not generally conserved, which advocates for the energy center in PIER as the STOV center. We argue that STOVs are generated in experiments to purportedly have elliptical symmetry in space-time. The values provided in PIER should then be taken as the reference for elliptical STOVs, and the theory therein to evaluate the transverse OAM of other wave packets. Hancock et al (2021 Phys. Rev. Lett.127 193901; 2024 Phys. Rev. X 14 011031) erroneously attribute the transverse OAM of elliptical STOVs in space to the elliptical STOVs in space-time that they consider theoretically and can generate in their experiments.
{"title":"Clarification of the transverse orbital angular momentum of spatiotemporal optical vortices","authors":"Miguel A Porras","doi":"10.1088/2040-8986/ad645a","DOIUrl":"https://doi.org/10.1088/2040-8986/ad645a","url":null,"abstract":"Advances in the generation and the application of spatiotemporal optical vortices (STOV) are proceeding fast, but fundamental aspects of their nature remain obscure. Bliokh (2023 Phys. Rev. A 107 L031501) (PRA) and Porras (2023 Prog. Electromagn. Res.177 95) (PIER) provide contradictory results on the transverse orbital angular momentum (OAM) carried by STOVs. We show that the results by Porras in PIER and by Bliokh in PRA refer to different STOVs and are all correct. In PIER, STOVs are elliptical at given cross section and time, or in space-time, but not in three-dimensional space. In PRA, STOVs are elliptical in space but not in space-time. This is evidenced from two dual, equivalent theories on the transverse OAM where a wave packet is seen in space-time evolving with propagation distance or in space evolving in time, that account for all values of the total, intrinsic and extrinsic OAM in PIERS and PRA. However, the intrinsic OAM with respect to the photon wave function center in PRA is not generally conserved, which advocates for the energy center in PIER as the STOV center. We argue that STOVs are generated in experiments to purportedly have elliptical symmetry in space-time. The values provided in PIER should then be taken as the reference for elliptical STOVs, and the theory therein to evaluate the transverse OAM of other wave packets. Hancock et al (2021 Phys. Rev. Lett.127 193901; 2024 Phys. Rev. X 14 011031) erroneously attribute the transverse OAM of elliptical STOVs in space to the elliptical STOVs in space-time that they consider theoretically and can generate in their experiments.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"26 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141779831","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}
Terahertz metasurface sensors attract extensive attention for excellent characterisics. However, most existing sensing schemes overlooked the polarization state of electromagnetic waves. Here, we propose a plasmonic metasurface sensor based on the elliptical polarization state of reflected EM wave, which can be used for the sensing of influenza A virus. The sensor achieves the conversion from linear polarization to circular polarization within 1–3 THz. By analysing the electromagnetic field distributions of the resonances at 1.43 THz and 2.16 THz, it can be concluded that the polarization conversion originates from the magnetic dipole. Besides, the sensor can characterize the changes in the complex refractive index of the test sample based on the elliptical polarization state of the reflected wave. The electromagnetic response of the metasurface sensor shows an excellent linear relationship between the rotating direction angle of polarization ellipse and the extinction coefficient (k) of the complex RI of the analyte. Furthermore, we also demonstrate the feasibility of detecting three subtypes of Influenza A viruses (H1N1, H5N2, and H9N2) at 1.39 THz though the elliptical polarization state. This sensing approach does not rely on high-precision broadband scanning, providing an alternative perspective for THz biosensing.
{"title":"Terahertz polarization sensing for influenza A virus based on plasmonic metasurface","authors":"Hai Liu, Xiaolin Wang, Cong Chen, Hongzhong Cui, Futao Cui, Yaowei Dai, Peng Gao, Senhao Duan, Zongyang Gao and Tong Zhou","doi":"10.1088/2040-8986/ad6168","DOIUrl":"https://doi.org/10.1088/2040-8986/ad6168","url":null,"abstract":"Terahertz metasurface sensors attract extensive attention for excellent characterisics. However, most existing sensing schemes overlooked the polarization state of electromagnetic waves. Here, we propose a plasmonic metasurface sensor based on the elliptical polarization state of reflected EM wave, which can be used for the sensing of influenza A virus. The sensor achieves the conversion from linear polarization to circular polarization within 1–3 THz. By analysing the electromagnetic field distributions of the resonances at 1.43 THz and 2.16 THz, it can be concluded that the polarization conversion originates from the magnetic dipole. Besides, the sensor can characterize the changes in the complex refractive index of the test sample based on the elliptical polarization state of the reflected wave. The electromagnetic response of the metasurface sensor shows an excellent linear relationship between the rotating direction angle of polarization ellipse and the extinction coefficient (k) of the complex RI of the analyte. Furthermore, we also demonstrate the feasibility of detecting three subtypes of Influenza A viruses (H1N1, H5N2, and H9N2) at 1.39 THz though the elliptical polarization state. This sensing approach does not rely on high-precision broadband scanning, providing an alternative perspective for THz biosensing.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"23 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141779830","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 : 2024-07-17DOI: 10.1088/2040-8986/ad5f9c
Bo-Sture K Skagerstam and Per K Rekdal
In the present paper we construct a properly defined quantum state expressed in terms of elliptic Jacobi theta functions for the self-adjoint observables angular position θ and the corresponding angular momentum operator in units of . The quantum uncertainties Δθ and ΔL for the state are well-defined and are shown to give a lower value of the uncertainty product in contrast to the so called minimal uncertainty states as discussed in Franke-Arnold et al (2004 New J. Phys.6 103-1-8). The mean value of the state is not required to be an integer. In the case of any half-integer mean value the state constructed exhibits a remarkable critical behavior with upper and lower bounds and .
在本文中，我们构建了一个定义明确的量子态，用椭圆雅各比 Theta 函数来表示自相关观测量角位置 θ 和相应的角动量算子（单位：θ）。 该态的量子不确定度 Δθ 和 ΔL 定义明确，并证明与 Franke-Arnold 等（2004 New J. Phys.6，103-1-8）中讨论的所谓最小不确定度态相比，该态的不确定度乘积值较低。状态的平均值并不需要是整数。在任何半整数均值的情况下，所构造的状态都会表现出显著的临界行为，具有上下限和 。
{"title":"On quantum states for angular position and angular momentum of light","authors":"Bo-Sture K Skagerstam and Per K Rekdal","doi":"10.1088/2040-8986/ad5f9c","DOIUrl":"https://doi.org/10.1088/2040-8986/ad5f9c","url":null,"abstract":"In the present paper we construct a properly defined quantum state expressed in terms of elliptic Jacobi theta functions for the self-adjoint observables angular position θ and the corresponding angular momentum operator in units of . The quantum uncertainties Δθ and ΔL for the state are well-defined and are shown to give a lower value of the uncertainty product in contrast to the so called minimal uncertainty states as discussed in Franke-Arnold et al (2004 New J. Phys.6 103-1-8). The mean value of the state is not required to be an integer. In the case of any half-integer mean value the state constructed exhibits a remarkable critical behavior with upper and lower bounds and .","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"20 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141745176","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 : 2024-07-16DOI: 10.1088/2040-8986/ad261f
Erik Agrell, Magnus Karlsson, Francesco Poletti, Shu Namiki, Xi (Vivian) Chen, Leslie A Rusch, Benjamin Puttnam, Polina Bayvel, Laurent Schmalen, Zhenning Tao, Frank R Kschischang, Alex Alvarado, Biswanath Mukherjee, Ramon Casellas, Xiang Zhou, Dora van Veen, Georg Mohs, Elaine Wong, Antonio Mecozzi, Mohamed-Slim Alouini, Eleni Diamanti and Murat Uysal
The Covid-19 pandemic showed forcefully the fundamental importance broadband data communication and the internet has in our society. Optical communications forms the undisputable backbone of this critical infrastructure, and it is supported by an interdisciplinary research community striving to improve and develop it further. Since the first ‘Roadmap of optical communications’ was published in 2016, the field has seen significant progress in all areas, and time is ripe for an update of the research status. The optical communications area has become increasingly diverse, covering research in fundamental physics and materials science, high-speed electronics and photonics, signal processing and coding, and communication systems and networks. This roadmap describes state-of-the-art and future outlooks in the optical communications field. The article is divided into 20 sections on selected areas, each written by a leading expert in that area. The sections are thematically grouped into four parts with 4–6 sections each, covering, respectively, hardware, algorithms, networks and systems. Each section describes the current status, the future challenges, and development needed to meet said challenges in their area. As a whole, this roadmap provides a comprehensive and unprecedented overview of the contemporary optical communications research, and should be essential reading for researchers at any level active in this field.
{"title":"Roadmap on optical communications","authors":"Erik Agrell, Magnus Karlsson, Francesco Poletti, Shu Namiki, Xi (Vivian) Chen, Leslie A Rusch, Benjamin Puttnam, Polina Bayvel, Laurent Schmalen, Zhenning Tao, Frank R Kschischang, Alex Alvarado, Biswanath Mukherjee, Ramon Casellas, Xiang Zhou, Dora van Veen, Georg Mohs, Elaine Wong, Antonio Mecozzi, Mohamed-Slim Alouini, Eleni Diamanti and Murat Uysal","doi":"10.1088/2040-8986/ad261f","DOIUrl":"https://doi.org/10.1088/2040-8986/ad261f","url":null,"abstract":"The Covid-19 pandemic showed forcefully the fundamental importance broadband data communication and the internet has in our society. Optical communications forms the undisputable backbone of this critical infrastructure, and it is supported by an interdisciplinary research community striving to improve and develop it further. Since the first ‘Roadmap of optical communications’ was published in 2016, the field has seen significant progress in all areas, and time is ripe for an update of the research status. The optical communications area has become increasingly diverse, covering research in fundamental physics and materials science, high-speed electronics and photonics, signal processing and coding, and communication systems and networks. This roadmap describes state-of-the-art and future outlooks in the optical communications field. The article is divided into 20 sections on selected areas, each written by a leading expert in that area. The sections are thematically grouped into four parts with 4–6 sections each, covering, respectively, hardware, algorithms, networks and systems. Each section describes the current status, the future challenges, and development needed to meet said challenges in their area. As a whole, this roadmap provides a comprehensive and unprecedented overview of the contemporary optical communications research, and should be essential reading for researchers at any level active in this field.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"39 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141721835","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 : 2024-07-10DOI: 10.1088/2040-8986/ad5d02
Julio Aurelio Sarabia-Alonso and Rubén Ramos-García
Since Nobel Laureate Arthur Ashkin first introduced the trapping and manipulation of microparticles using light, numerous studies have explored this technique not only for dielectric/metallic particles but also for organic matter. This advancement has significantly expanded the landscape of non-contact and non-invasive micromanipulation at the nanometric scale. However, micromanipulation of particles with a refractive index smaller than the host medium, np< nm, proves challenging with Gaussian beams. To overcome this obstacle, a force known as thermocapillary, or the Marangoni force, has emerged as a straightforward trapping mechanism for bubbles in liquids. The Marangoni force results from the surface tension of bubbles, induced either thermally or chemically—by creating a temperature gradient or adding surfactants, respectively. The surface tension gradient on the liquid host induces tangential stress on the bubble wall, causing the bubble to move toward the region of lower surface tension, where it faces less opposing force. When the Marangoni force is generated by a laser beam’s temperature gradient, it becomes an exceptionally effective mechanism for the steady-state trapping and three-dimensional manipulation of bubbles, even with low optical power lasers. This force produces both longitudinal and transversal forces, resembling optical forces, creating a three-dimensional potential well capable of handling bubbles with radii of tens to hundreds of microns. This work provides guidance and demonstrates, both experimentally and theoretically, the step-by-step process of quasi-steady-state trapping and three-dimensional manipulation of bubbles through optothermal effects. The bubbles in question are tens of microns in size, significantly larger than those that optical tweezers can trap/manipulate. Furthermore, the study emphasizes the crucial role of the Marangoni force in this process, outlining its various advantages.
{"title":"Optothermal generation, steady-state trapping, and 3D manipulation of bubbles: an experimental and theoretical analysis of the Marangoni effect","authors":"Julio Aurelio Sarabia-Alonso and Rubén Ramos-García","doi":"10.1088/2040-8986/ad5d02","DOIUrl":"https://doi.org/10.1088/2040-8986/ad5d02","url":null,"abstract":"Since Nobel Laureate Arthur Ashkin first introduced the trapping and manipulation of microparticles using light, numerous studies have explored this technique not only for dielectric/metallic particles but also for organic matter. This advancement has significantly expanded the landscape of non-contact and non-invasive micromanipulation at the nanometric scale. However, micromanipulation of particles with a refractive index smaller than the host medium, np< nm, proves challenging with Gaussian beams. To overcome this obstacle, a force known as thermocapillary, or the Marangoni force, has emerged as a straightforward trapping mechanism for bubbles in liquids. The Marangoni force results from the surface tension of bubbles, induced either thermally or chemically—by creating a temperature gradient or adding surfactants, respectively. The surface tension gradient on the liquid host induces tangential stress on the bubble wall, causing the bubble to move toward the region of lower surface tension, where it faces less opposing force. When the Marangoni force is generated by a laser beam’s temperature gradient, it becomes an exceptionally effective mechanism for the steady-state trapping and three-dimensional manipulation of bubbles, even with low optical power lasers. This force produces both longitudinal and transversal forces, resembling optical forces, creating a three-dimensional potential well capable of handling bubbles with radii of tens to hundreds of microns. This work provides guidance and demonstrates, both experimentally and theoretically, the step-by-step process of quasi-steady-state trapping and three-dimensional manipulation of bubbles through optothermal effects. The bubbles in question are tens of microns in size, significantly larger than those that optical tweezers can trap/manipulate. Furthermore, the study emphasizes the crucial role of the Marangoni force in this process, outlining its various advantages.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"54 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588082","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 : 2024-07-09DOI: 10.1088/2040-8986/ad5d04
Mikhail A Vorontsov, Svetlana L Lachinova, Ernst Polnau
The impact of the laser beacon size on the performance of an ideal phase-conjugation-type adaptive optics (AO) system is analyzed using wave-optics-based numerical simulation. The analysis includes wavefront aberration sensing and closed-loop control for laser beam propagation both in vacuum and in distributed (volume) atmospheric turbulence with the beacon beam scattering off a flat extended target with Lambertian surface roughness. For mitigation of the impact of target-induced speckle effects on the performance of AO systems, speckle-average wavefront sensing and control approaches are introduced and analyzed. The results demonstrate that proposed speckle-average phase conjugation control algorithms enable partial mitigation of turbulence-induced aberrations in presence of strong speckle modulations.
{"title":"Analysis of speckle-beacon size impact on wavefront sensing and closed-loop control in deep turbulence conditions","authors":"Mikhail A Vorontsov, Svetlana L Lachinova, Ernst Polnau","doi":"10.1088/2040-8986/ad5d04","DOIUrl":"https://doi.org/10.1088/2040-8986/ad5d04","url":null,"abstract":"The impact of the laser beacon size on the performance of an ideal phase-conjugation-type adaptive optics (AO) system is analyzed using wave-optics-based numerical simulation. The analysis includes wavefront aberration sensing and closed-loop control for laser beam propagation both in vacuum and in distributed (volume) atmospheric turbulence with the beacon beam scattering off a flat extended target with Lambertian surface roughness. For mitigation of the impact of target-induced speckle effects on the performance of AO systems, speckle-average wavefront sensing and control approaches are introduced and analyzed. The results demonstrate that proposed speckle-average phase conjugation control algorithms enable partial mitigation of turbulence-induced aberrations in presence of strong speckle modulations.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"26 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570183","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 : 2024-07-09DOI: 10.1088/2040-8986/ad5d03
Pengsen Wang, Kai Guo, Zhongyi Guo
Integration and miniaturization of multi-channel single-pixel imaging systems have become a developing trend. However, it is challenging to meet such development needs solely relying on traditional optical devices. One feasible solution is the utilization of metasurfaces with multiplexing functionality. Here, we propose and validate an all-dielectric, anisotropic metasurface that provides a random mask with polarization multiplexing for single pixel imaging. The design ensures each mask contains 50% target information, allowing adaptive correlated imaging of different targets without needing to redesign the masks. By optimizing the metasurface, we enhance computational efficiency by preventing correlation between different polarization channels and mask patterns. We also adjust the parameters of the compressed sensing algorithm to accommodate various sampling rates, ensuring high-quality image reconstruction. Additionally, the whole system is simulated by the angular spectrum transmission and compressed sensing reconstruction algorithm, providing image reconstruction results for metasurfaces of different sizes, demonstrating the feasibility of the proposed approach. It is noteworthy that the designed metasurface works for single-wavelength operation and could be extended to multispectral imaging by introducing achromatic metasurface technology. The proposed method could miniaturize the optical devices and reduce light loss.
{"title":"All-dielectric metasurface for polarization-multiplexed single-pixel imaging","authors":"Pengsen Wang, Kai Guo, Zhongyi Guo","doi":"10.1088/2040-8986/ad5d03","DOIUrl":"https://doi.org/10.1088/2040-8986/ad5d03","url":null,"abstract":"Integration and miniaturization of multi-channel single-pixel imaging systems have become a developing trend. However, it is challenging to meet such development needs solely relying on traditional optical devices. One feasible solution is the utilization of metasurfaces with multiplexing functionality. Here, we propose and validate an all-dielectric, anisotropic metasurface that provides a random mask with polarization multiplexing for single pixel imaging. The design ensures each mask contains 50% target information, allowing adaptive correlated imaging of different targets without needing to redesign the masks. By optimizing the metasurface, we enhance computational efficiency by preventing correlation between different polarization channels and mask patterns. We also adjust the parameters of the compressed sensing algorithm to accommodate various sampling rates, ensuring high-quality image reconstruction. Additionally, the whole system is simulated by the angular spectrum transmission and compressed sensing reconstruction algorithm, providing image reconstruction results for metasurfaces of different sizes, demonstrating the feasibility of the proposed approach. It is noteworthy that the designed metasurface works for single-wavelength operation and could be extended to multispectral imaging by introducing achromatic metasurface technology. The proposed method could miniaturize the optical devices and reduce light loss.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"16 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570181","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 : 2024-07-09DOI: 10.1088/2040-8986/ad5f40
Kayn A Forbes
It has recently been established that a linearly-polarized optical vortex possesses spin angular momentum density in the direction of propagation (longitudinal spin) under tight-focusing. The helicity of light has long been associated with longitudinal spin angular momentum. Here we show that the longitudinal spin density of linearly-polarized vortices is anomalous because it has no associated helicity. It was also recently determined that the polarization-independent helicity of tightly-focused optical vortices is associated with their transverse spin momentum density. The key finding of this work is the fact that, in general, longitudinal spin can not necessarily be associated with helicity, and transverse spin is in general not associated with a zero helicity, and such extraordinary behaviour manifests most clearly for optical vortices under non-paraxial conditions.
{"title":"On the orbit-induced spin density of tightly focused optical vortex beams: ellipticity and helicity","authors":"Kayn A Forbes","doi":"10.1088/2040-8986/ad5f40","DOIUrl":"https://doi.org/10.1088/2040-8986/ad5f40","url":null,"abstract":"It has recently been established that a linearly-polarized optical vortex possesses spin angular momentum density in the direction of propagation (longitudinal spin) under tight-focusing. The helicity of light has long been associated with longitudinal spin angular momentum. Here we show that the longitudinal spin density of linearly-polarized vortices is anomalous because it has no associated helicity. It was also recently determined that the polarization-independent helicity of tightly-focused optical vortices is associated with their transverse spin momentum density. The key finding of this work is the fact that, in general, longitudinal spin can not necessarily be associated with helicity, and transverse spin is in general not associated with a zero helicity, and such extraordinary behaviour manifests most clearly for optical vortices under non-paraxial conditions.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"32 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570182","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 : 2024-07-03DOI: 10.1088/2040-8986/ad5c7d
Juan M Merlo and Madeleine H Carhart
In this work we present the study of in-plane radiation patterns generated by particles with dimensions larger than the excitation wavelength. We studied the in-plane radiation of Au structures focusing on two cases: particles and triangular crystals. We found that the radiation patterns were produced by the scattering of the excitation field at the bottom edges of the studied structures. In addition, we found the in-plane radiation decay exponentially due to the refractive index contrast between the substrate and superstate. Furthermore, we proved that in-plane radiation patterns originating from different structures can interact and generate interesting geometries. Finally, in addition to our experimental studies, we show numerically calculated simulations which agreed with our experimental results and thus confirmed our findings.
{"title":"In-plane radiation pattern generated by large particles in dielectric substrates","authors":"Juan M Merlo and Madeleine H Carhart","doi":"10.1088/2040-8986/ad5c7d","DOIUrl":"https://doi.org/10.1088/2040-8986/ad5c7d","url":null,"abstract":"In this work we present the study of in-plane radiation patterns generated by particles with dimensions larger than the excitation wavelength. We studied the in-plane radiation of Au structures focusing on two cases: particles and triangular crystals. We found that the radiation patterns were produced by the scattering of the excitation field at the bottom edges of the studied structures. In addition, we found the in-plane radiation decay exponentially due to the refractive index contrast between the substrate and superstate. Furthermore, we proved that in-plane radiation patterns originating from different structures can interact and generate interesting geometries. Finally, in addition to our experimental studies, we show numerically calculated simulations which agreed with our experimental results and thus confirmed our findings.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"26 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141551134","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 : 2024-07-03DOI: 10.1088/2040-8986/ad5b73
Varnam Sherawat, Renuka Bokolia and Ravindra Kumar Sinha
The present study elucidates a photonic crystal (PhC)-based pressure sensor exploiting the change in refractive index with pressure and the corresponding structural deformation of the dielectric material. The stress-sensitive refractive indices of the constituent materials of the PhC have been considered to study the effect of applied pressure on the photonic bandgap (PBG) characteristics of the structure. The designed pressure sensor, proposed using a two-dimensional hexagonal lattice arrangement of air holes in a dielectric slab, operates in the high-pressure range of 1–6 GPa. A comparative study of the PBG characteristics with the application of high pressure has been reported for three semiconducting materials—GaAs, Ge and Si, used for the dielectric slab in the proposed structure. GaAs is found to exhibit the highest sensitivity to pressure variations and shows more pronounced shifting of the midgap wavelength with pressure in comparison to Ge and Si. The largest PBG is seen in the Ge-based structure, closely followed by the GaAs and Si-based structures. The proposed structure is suitable for high-pressure sensing applications.
本研究阐明了一种基于光子晶体（PhC）的压力传感器，它利用了折射率随压力的变化以及介电材料相应的结构变形。研究考虑了光子晶体组成材料的应力敏感折射率，以研究施加压力对结构的光子带隙（PBG）特性的影响。所设计的压力传感器是利用电介质板中气孔的二维六边形晶格排列设计的，可在 1-6 GPa 的高压范围内工作。报告对拟议结构中用于电介质板的三种半导体材料--砷化镓、锗和硅进行了高压应用下 PBG 特性的比较研究。研究发现，与 Ge 和 Si 相比，GaAs 对压力变化的敏感度最高，中隙波长随压力的变化也更为明显。基于 Ge 的结构具有最大的 PBG，紧随其后的是基于 GaAs 和 Si 的结构。所提出的结构适用于高压传感应用。
{"title":"Pressure-dependent bandgap characteristics in photonic crystals with sensing applications","authors":"Varnam Sherawat, Renuka Bokolia and Ravindra Kumar Sinha","doi":"10.1088/2040-8986/ad5b73","DOIUrl":"https://doi.org/10.1088/2040-8986/ad5b73","url":null,"abstract":"The present study elucidates a photonic crystal (PhC)-based pressure sensor exploiting the change in refractive index with pressure and the corresponding structural deformation of the dielectric material. The stress-sensitive refractive indices of the constituent materials of the PhC have been considered to study the effect of applied pressure on the photonic bandgap (PBG) characteristics of the structure. The designed pressure sensor, proposed using a two-dimensional hexagonal lattice arrangement of air holes in a dielectric slab, operates in the high-pressure range of 1–6 GPa. A comparative study of the PBG characteristics with the application of high pressure has been reported for three semiconducting materials—GaAs, Ge and Si, used for the dielectric slab in the proposed structure. GaAs is found to exhibit the highest sensitivity to pressure variations and shows more pronounced shifting of the midgap wavelength with pressure in comparison to Ge and Si. The largest PBG is seen in the Ge-based structure, closely followed by the GaAs and Si-based structures. The proposed structure is suitable for high-pressure sensing applications.","PeriodicalId":16775,"journal":{"name":"Journal of Optics","volume":"47 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141551133","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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