Ultrafast laser sources in the far ultraviolet (100–300 nm) have been the subject of intense experimental efforts for several decades, driven primarily by the requirements of advanced experiments in ultrafast science. Resonant dispersive wave emission from high-energy laser pulses undergoing soliton self-compression in a gas-filled hollow capillary fiber promises to meet several of these requirements for the first time, most importantly by combining wide-ranging wavelength tuneability with the generation of extremely short pulses. In this Perspective, we give an overview of this approach to ultrafast far-ultraviolet sources, including its historical origin and underlying physical mechanism, the state of the art and current challenges, and our view of potential applications both within and beyond ultrafast science.
{"title":"HISOL: High-energy soliton dynamics enable ultrafast far-ultraviolet laser sources","authors":"Christian Brahms, John C. Travers","doi":"10.1063/5.0206108","DOIUrl":"https://doi.org/10.1063/5.0206108","url":null,"abstract":"Ultrafast laser sources in the far ultraviolet (100–300 nm) have been the subject of intense experimental efforts for several decades, driven primarily by the requirements of advanced experiments in ultrafast science. Resonant dispersive wave emission from high-energy laser pulses undergoing soliton self-compression in a gas-filled hollow capillary fiber promises to meet several of these requirements for the first time, most importantly by combining wide-ranging wavelength tuneability with the generation of extremely short pulses. In this Perspective, we give an overview of this approach to ultrafast far-ultraviolet sources, including its historical origin and underlying physical mechanism, the state of the art and current challenges, and our view of potential applications both within and beyond ultrafast science.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"23 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939684","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}
V. A. Ribenek, P. A. Itrin, D. A. Korobko, A. A. Fotiadi
Passive harmonic mode-locking of a soliton fiber laser locked to optoacoustic resonance (OAR) in the cavity fiber ensures high-frequency laser operation, high pulse stability, and low timing jitter. However, the pulse repetition rate (PRR) of such lasers is limited to ∼1 GHz for standard fibers due to the available acoustic modes. Here, we address these limitations by demonstrating a soliton fiber laser built from standard fiber components and subjected to double harmonic mode-locking (DHML). As an example, the laser adjusted to operate at the 15th harmonic of its cavity matching the OAR at ∼199 MHz could be driven to operate at a high harmonic of this particular OAR frequency, thus reaching ∼12 GHz. This breakthrough is made possible through controllable optoacoustic interactions in a short, 50 cm segment of unjacketed cavity fiber. We propose that the precise alignment of the laser cavity harmonic and fiber acoustic modes leads to a long-lived narrow-band acoustic vibration. This vibration sets the pace for the pulses circulating in the cavity by suppressing modes that do not conform to the Vernier principle. The surviving modes, equally spaced by the OAR frequency, in cooperation with the gain depletion and recovery mechanism, facilitate the formation of stable high-frequency pulse sequences, enabling DHML. In this process, the OAR rather than the laser cavity defines the elementary step for laser PRR tuning. Throughout the entire PRR tuning range, the soliton fiber laser exhibits enhanced stability, demonstrating supermode suppression levels better than ∼40 dB and picosecond pulse timing jitter.
{"title":"Double harmonic mode-locking in soliton fiber ring laser acquired through the resonant optoacoustic coupling","authors":"V. A. Ribenek, P. A. Itrin, D. A. Korobko, A. A. Fotiadi","doi":"10.1063/5.0195623","DOIUrl":"https://doi.org/10.1063/5.0195623","url":null,"abstract":"Passive harmonic mode-locking of a soliton fiber laser locked to optoacoustic resonance (OAR) in the cavity fiber ensures high-frequency laser operation, high pulse stability, and low timing jitter. However, the pulse repetition rate (PRR) of such lasers is limited to ∼1 GHz for standard fibers due to the available acoustic modes. Here, we address these limitations by demonstrating a soliton fiber laser built from standard fiber components and subjected to double harmonic mode-locking (DHML). As an example, the laser adjusted to operate at the 15th harmonic of its cavity matching the OAR at ∼199 MHz could be driven to operate at a high harmonic of this particular OAR frequency, thus reaching ∼12 GHz. This breakthrough is made possible through controllable optoacoustic interactions in a short, 50 cm segment of unjacketed cavity fiber. We propose that the precise alignment of the laser cavity harmonic and fiber acoustic modes leads to a long-lived narrow-band acoustic vibration. This vibration sets the pace for the pulses circulating in the cavity by suppressing modes that do not conform to the Vernier principle. The surviving modes, equally spaced by the OAR frequency, in cooperation with the gain depletion and recovery mechanism, facilitate the formation of stable high-frequency pulse sequences, enabling DHML. In this process, the OAR rather than the laser cavity defines the elementary step for laser PRR tuning. Throughout the entire PRR tuning range, the soliton fiber laser exhibits enhanced stability, demonstrating supermode suppression levels better than ∼40 dB and picosecond pulse timing jitter.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"191 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939499","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}
Matrix inversion is a fundamental and widely utilized linear algebraic operation but computationally expensive in digital-clock-based platforms. Optical computing is a new computing paradigm with high speed and energy efficiency, and the computation can be realized through light propagation. However, there is a scarcity of experimentally implemented matrix inverters that exhibit both high integration density and the capability to perform complex-valued operations in existing optical systems. For the first time, we experimentally demonstrated an iterative all-optical chip-scale processor to perform the computation of complex-valued matrix inversion using the Richardson method. Our chip-scale processor achieves an iteration speed of 10 GHz, which can facilitate ultra-fast matrix inversion with the assistance of high-speed Mach–Zehnder interferometer modulators. The convergence can be attained within 20 iterations, yielding an accuracy of 90%. The proposed chip-scale all-optical complex-valued matrix inverter represents a distinctive innovation in the field of all-optical recursive systems, offering significant potential for solving computationally intensive mathematical problems.
{"title":"Chip-scale all-optical complex-valued matrix inverter","authors":"Xinyu Liu, Junwei Cheng, Hailong Zhou, Jianji Dong, Xinliang Zhang","doi":"10.1063/5.0200149","DOIUrl":"https://doi.org/10.1063/5.0200149","url":null,"abstract":"Matrix inversion is a fundamental and widely utilized linear algebraic operation but computationally expensive in digital-clock-based platforms. Optical computing is a new computing paradigm with high speed and energy efficiency, and the computation can be realized through light propagation. However, there is a scarcity of experimentally implemented matrix inverters that exhibit both high integration density and the capability to perform complex-valued operations in existing optical systems. For the first time, we experimentally demonstrated an iterative all-optical chip-scale processor to perform the computation of complex-valued matrix inversion using the Richardson method. Our chip-scale processor achieves an iteration speed of 10 GHz, which can facilitate ultra-fast matrix inversion with the assistance of high-speed Mach–Zehnder interferometer modulators. The convergence can be attained within 20 iterations, yielding an accuracy of 90%. The proposed chip-scale all-optical complex-valued matrix inverter represents a distinctive innovation in the field of all-optical recursive systems, offering significant potential for solving computationally intensive mathematical problems.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"2 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939414","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}
Abdelrahman Z. Al-Attili, Daniel Burt, Tasmiat Rahman, Zuo Li, Naoki Higashitarumizu, Frederic Y. Gardes, Yasuhiko Ishikawa, Shinichi Saito
Various excitation-induced loss mechanisms have been identified during the development of direct-gap semiconductor lasers. Recently, indirect-gap laser sources, particularly germanium (Ge) or GeSn based, have emerged due to silicon industry compatibility. Tensile strain is crucial for optical gain or low-threshold room-temperature operation in such media. This study investigates an excitation-induced optical loss mechanism of mechanical origin in Ge-based micro-cavities with all-around stressor layers, a popular platform for strain-engineered laser sources. Using Raman spectroscopy, photoluminescence, and simulations, we find that excitation lowers the optical gain by altering the strain profile. Heating causes Ge micro-cavities to expand within a constraining stressor layer, inducing compressive strain, which is explained by the mismatch in thermal expansion coefficients.
在开发直接间隙半导体激光器的过程中，人们发现了各种激发引起的损耗机制。最近，由于硅工业的兼容性，出现了间接间隙激光源，特别是基于锗（Ge）或硒（GeSn）的激光源。拉伸应变对于此类介质的光学增益或低阈值室温操作至关重要。本研究调查了具有全方位应力层的 Ge 基微腔中的机械源激发诱导光学损耗机制，该微腔是应变工程激光源的常用平台。利用拉曼光谱、光致发光和模拟，我们发现激励通过改变应变曲线来降低光学增益。加热会使 Ge 微腔在约束应力层内膨胀，从而产生压缩应变，这可以用热膨胀系数的不匹配来解释。
{"title":"Mechanically induced optical loss mechanism due to thermal expansion coefficient mismatch in micro-cavities with all-around stressor layers","authors":"Abdelrahman Z. Al-Attili, Daniel Burt, Tasmiat Rahman, Zuo Li, Naoki Higashitarumizu, Frederic Y. Gardes, Yasuhiko Ishikawa, Shinichi Saito","doi":"10.1063/5.0203305","DOIUrl":"https://doi.org/10.1063/5.0203305","url":null,"abstract":"Various excitation-induced loss mechanisms have been identified during the development of direct-gap semiconductor lasers. Recently, indirect-gap laser sources, particularly germanium (Ge) or GeSn based, have emerged due to silicon industry compatibility. Tensile strain is crucial for optical gain or low-threshold room-temperature operation in such media. This study investigates an excitation-induced optical loss mechanism of mechanical origin in Ge-based micro-cavities with all-around stressor layers, a popular platform for strain-engineered laser sources. Using Raman spectroscopy, photoluminescence, and simulations, we find that excitation lowers the optical gain by altering the strain profile. Heating causes Ge micro-cavities to expand within a constraining stressor layer, inducing compressive strain, which is explained by the mismatch in thermal expansion coefficients.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"67 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939412","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}
M. R. M. Atalla, C. Lemieux-Leduc, S. Assali, S. Koelling, P. Daoust, O. Moutanabbir
There is an increasing need for silicon-compatible high-bandwidth extended-short wave infrared (e-SWIR) photodetectors (PDs) to implement cost-effective and scalable optoelectronic devices. These systems are quintessential to address several technological bottlenecks in detection and ranging, surveillance, ultrafast spectroscopy, and imaging. In fact, current e-SWIR high-bandwidth PDs are predominantly made of III–V compound semiconductors and thus are costly and suffer a limited integration on silicon besides a low responsivity at wavelengths exceeding 2.3 μm. To circumvent these challenges, Ge1−xSnx semiconductors have been proposed as building blocks for silicon-integrated high-speed e-SWIR devices. Herein, this study demonstrates vertical all-GeSn PIN PDs consisting of p-Ge0.92Sn0.08/i-Ge0.91Sn0.09/n-Ge0.89Sn0.11 and p-Ge0.91Sn0.09/i-Ge0.88Sn0.12/n-Ge0.87Sn0.13 heterostructures grown on silicon following a step-graded temperature-controlled epitaxy protocol. The performance of these PDs was investigated as a function of the device diameter in the 10–30 μm range. The developed PD devices yield a high bandwidth of 12.4 GHz at a bias of 5 V for a device diameter of 10 μm. Moreover, these devices show a high responsivity of 0.24 A/W, a low noise, and a 2.8 μm cutoff wavelength, thus covering the whole e-SWIR range.
{"title":"Extended short-wave infrared high-speed all-GeSn PIN photodetectors on silicon","authors":"M. R. M. Atalla, C. Lemieux-Leduc, S. Assali, S. Koelling, P. Daoust, O. Moutanabbir","doi":"10.1063/5.0197018","DOIUrl":"https://doi.org/10.1063/5.0197018","url":null,"abstract":"There is an increasing need for silicon-compatible high-bandwidth extended-short wave infrared (e-SWIR) photodetectors (PDs) to implement cost-effective and scalable optoelectronic devices. These systems are quintessential to address several technological bottlenecks in detection and ranging, surveillance, ultrafast spectroscopy, and imaging. In fact, current e-SWIR high-bandwidth PDs are predominantly made of III–V compound semiconductors and thus are costly and suffer a limited integration on silicon besides a low responsivity at wavelengths exceeding 2.3 μm. To circumvent these challenges, Ge1−xSnx semiconductors have been proposed as building blocks for silicon-integrated high-speed e-SWIR devices. Herein, this study demonstrates vertical all-GeSn PIN PDs consisting of p-Ge0.92Sn0.08/i-Ge0.91Sn0.09/n-Ge0.89Sn0.11 and p-Ge0.91Sn0.09/i-Ge0.88Sn0.12/n-Ge0.87Sn0.13 heterostructures grown on silicon following a step-graded temperature-controlled epitaxy protocol. The performance of these PDs was investigated as a function of the device diameter in the 10–30 μm range. The developed PD devices yield a high bandwidth of 12.4 GHz at a bias of 5 V for a device diameter of 10 μm. Moreover, these devices show a high responsivity of 0.24 A/W, a low noise, and a 2.8 μm cutoff wavelength, thus covering the whole e-SWIR range.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"34 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939418","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}
Optical diffraction tomography can be performed with low phototoxicity and photobleaching to analyze 3D cells and tissues. It is desired to develop high throughput and powerful data processing capabilities. We propose high bandwidth holographic microscopy (HBHM). Based on the analyticity of complex amplitudes, the unified holographic multiplexing transfer function is established. A high bandwidth scattering field is achieved via the k-space optical origami of two 2D wavefronts from one interferogram. Scanning illumination modulates the high-horizontal and axial k-space to endow synthetic-aperture from 2D high space-bandwidth product (SBP) scattering fields. The bright-field counterpart SBP of a single scattering field from HBHM is 14.6 megapixels, while the number of pixels is only 13.7 megapixels. It achieves an eight-fold SBP enhancement under the same number of pixels and diffraction limit. The HBHM paves the way toward the performance of high throughput, large-scale, and non-invasive histopathology, cell biology, and industrial inspection.
光学衍射断层扫描可以在低光毒性和光漂白的情况下分析三维细胞和组织。我们希望开发高通量和强大的数据处理能力。我们提出了高带宽全息显微技术（HBHM）。基于复振幅的可分析性，建立了统一的全息复用传递函数。通过一个干涉图的两个二维波面的 k 空间光学折纸，实现了高带宽散射场。扫描照明调制高水平和轴向 k 空间，赋予二维高空间带宽乘积（SBP）散射场合成孔径。HBHM 单个散射场的明场对应 SBP 为 1460 万像素，而像素数仅为 1370 万像素。在相同的像素数和衍射极限下，它实现了八倍的 SBP 增强。HBHM 为实现高通量、大规模和无创组织病理学、细胞生物学和工业检测铺平了道路。
{"title":"k-space holographic multiplexing for synthetic aperture diffraction tomography","authors":"Zhengzhong Huang, Liangcai Cao","doi":"10.1063/5.0203117","DOIUrl":"https://doi.org/10.1063/5.0203117","url":null,"abstract":"Optical diffraction tomography can be performed with low phototoxicity and photobleaching to analyze 3D cells and tissues. It is desired to develop high throughput and powerful data processing capabilities. We propose high bandwidth holographic microscopy (HBHM). Based on the analyticity of complex amplitudes, the unified holographic multiplexing transfer function is established. A high bandwidth scattering field is achieved via the k-space optical origami of two 2D wavefronts from one interferogram. Scanning illumination modulates the high-horizontal and axial k-space to endow synthetic-aperture from 2D high space-bandwidth product (SBP) scattering fields. The bright-field counterpart SBP of a single scattering field from HBHM is 14.6 megapixels, while the number of pixels is only 13.7 megapixels. It achieves an eight-fold SBP enhancement under the same number of pixels and diffraction limit. The HBHM paves the way toward the performance of high throughput, large-scale, and non-invasive histopathology, cell biology, and industrial inspection.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"65 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939408","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}
Synthetic gauge fields introduce an unconventional degree of freedom for studying many fundamental phenomena in different branches of physics. Here, we propose a scheme to use staggered synthetic gauge fields for control of the non-Hermitian skin effect (NHSE). A modified Su–Schrieffer–Heeger model is employed, where two dimer chains with non-reciprocal coupling phases are coupled, exhibiting non-trivial point-gap topology and the NHSE. In contrast to previous studies, the skin modes in our model are solely determined by the coupling phase terms associated with the staggered synthetic gauge fields. By manipulating such gauge fields, we can achieve maneuvering of skin modes as well as the bipolar NHSE. As a typical example, we set up a domain wall by imposing different synthetic gauge fields on two sides of the wall, thereby demonstrating flexible control of the non-Hermitian skin modes at the domain wall. Our scheme opens a new avenue for the creation and manipulation of NHSE by synthetic gauge fields, which may find applications in beam shaping and non-Hermitian topological devices.
{"title":"Control of non-Hermitian skin effect by staggered synthetic gauge fields","authors":"Huiyan Tang, Ziteng Wang, Liqin Tang, Daohong Song, Zhigang Chen, Hrvoje Buljan","doi":"10.1063/5.0196844","DOIUrl":"https://doi.org/10.1063/5.0196844","url":null,"abstract":"Synthetic gauge fields introduce an unconventional degree of freedom for studying many fundamental phenomena in different branches of physics. Here, we propose a scheme to use staggered synthetic gauge fields for control of the non-Hermitian skin effect (NHSE). A modified Su–Schrieffer–Heeger model is employed, where two dimer chains with non-reciprocal coupling phases are coupled, exhibiting non-trivial point-gap topology and the NHSE. In contrast to previous studies, the skin modes in our model are solely determined by the coupling phase terms associated with the staggered synthetic gauge fields. By manipulating such gauge fields, we can achieve maneuvering of skin modes as well as the bipolar NHSE. As a typical example, we set up a domain wall by imposing different synthetic gauge fields on two sides of the wall, thereby demonstrating flexible control of the non-Hermitian skin modes at the domain wall. Our scheme opens a new avenue for the creation and manipulation of NHSE by synthetic gauge fields, which may find applications in beam shaping and non-Hermitian topological devices.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"23 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939681","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}
Ali Zeineddine, Moein Shayegannia, Nazir P. Kherani, Joel Y. Y. Loh
Plasmonic graded nano-gratings enable rainbow trapping of multiple resonant modes over a wide wavelength spectrum, useful for multi-channel Surface Enhanced Raman Spectroscopy (SERS) of molecular species. However, rectangular nano-gratings have limitations in achieving efficient rainbow trapping and localizing a wide spectrum of plasmonic modes due to their stepwise geometry, which induces high dissipation of surface plasmon polaritons into the substrate. An alternative platform of graded triangular nano-gratings enables increased localization and more efficient adiabatic transformation between neighboring grooves. Varying groove angles, depths, and periods in the tapered geometry allow for smooth adjustment of the surface plasmon polariton propagation constant, reducing losses and maximizing nano-focusing inside the groove tips. To overcome the limitation of low aspect ratio in wet-etching silicon, we employed a multi-step process of reactive ion etching of a SiO2 barrier layer to generate aperture width, followed by anisotropic wet-etching. The resulting graded triangular nano-gratings showed excellent SERS enhancement along three laser wavelength excitations. The enhancement factors of 638 and 785 nm wavelengths are 8.5 × 109 and 9 × 108, respectively, for the detection of 1 µM Rhodamine 6G. In addition, graded triangular nano-gratings show similar enhancement factors for other species, specifically the lipid DPEE-PEG, at the 532 nm laser excitation wavelength with an excellent SERS enhancement factor of 1.5 × 109. Owing to the ability of the graded triangular gratings to elicit pronounced SERS responses across three distinct laser excitations, they unequivocally qualify as “rainbow trapping” structures. Wider apertures, lower ohmic losses, and the ability to tune the groove angle beyond conventional etching methods bode well for graded triangular gratings as a superior platform for miniature sensors.
{"title":"Exploiting graded triangular gratings for optimal nano-focusing: A novel approach to enhance SERS efficiency","authors":"Ali Zeineddine, Moein Shayegannia, Nazir P. Kherani, Joel Y. Y. Loh","doi":"10.1063/5.0195141","DOIUrl":"https://doi.org/10.1063/5.0195141","url":null,"abstract":"Plasmonic graded nano-gratings enable rainbow trapping of multiple resonant modes over a wide wavelength spectrum, useful for multi-channel Surface Enhanced Raman Spectroscopy (SERS) of molecular species. However, rectangular nano-gratings have limitations in achieving efficient rainbow trapping and localizing a wide spectrum of plasmonic modes due to their stepwise geometry, which induces high dissipation of surface plasmon polaritons into the substrate. An alternative platform of graded triangular nano-gratings enables increased localization and more efficient adiabatic transformation between neighboring grooves. Varying groove angles, depths, and periods in the tapered geometry allow for smooth adjustment of the surface plasmon polariton propagation constant, reducing losses and maximizing nano-focusing inside the groove tips. To overcome the limitation of low aspect ratio in wet-etching silicon, we employed a multi-step process of reactive ion etching of a SiO2 barrier layer to generate aperture width, followed by anisotropic wet-etching. The resulting graded triangular nano-gratings showed excellent SERS enhancement along three laser wavelength excitations. The enhancement factors of 638 and 785 nm wavelengths are 8.5 × 109 and 9 × 108, respectively, for the detection of 1 µM Rhodamine 6G. In addition, graded triangular nano-gratings show similar enhancement factors for other species, specifically the lipid DPEE-PEG, at the 532 nm laser excitation wavelength with an excellent SERS enhancement factor of 1.5 × 109. Owing to the ability of the graded triangular gratings to elicit pronounced SERS responses across three distinct laser excitations, they unequivocally qualify as “rainbow trapping” structures. Wider apertures, lower ohmic losses, and the ability to tune the groove angle beyond conventional etching methods bode well for graded triangular gratings as a superior platform for miniature sensors.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"65 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800219","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}
Junjian Lu, Tian Sang, Chui Pian, Siyuan Ouyang, Ze Jing
Flexible control of intrinsic chiroptical responses within compact nanostructures is crucial for flat optics, topological photonics, and chiroptics. However, previous approaches require complicated patterns with both in-plane and out-of-plane mirror symmetry breaking to achieve intrinsic chirality, and their chiroptical responses cannot be dynamically controlled as well. Herein, we demonstrated that near-perfect intrinsic circular dichroism (CD) can be achieved within a lithography-free structure consisting of the twisted bilayer α-MoO3 separated by a vanadium dioxide (VO2) film. By twisting the bilayer α-MoO3, dual-band intrinsic chiroptical responses can be realized due to the excitations of the hyperbolic phonon polaritons modes in the mid-infrared. It is the spin-selected average electric-field enhancement instead of the chiral absorption that is responsible for the intrinsic CD of the device. In addition, the chiroptical responses are insensitive to the variation of the thickness of the structure as well as the incident angle, and high contrast CD can be dynamically tuned by varying the volume fraction of VO2.
{"title":"Tailoring intrinsic chiroptical responses via twisted bilayer α-MoO3 separated by a VO2 film","authors":"Junjian Lu, Tian Sang, Chui Pian, Siyuan Ouyang, Ze Jing","doi":"10.1063/5.0197081","DOIUrl":"https://doi.org/10.1063/5.0197081","url":null,"abstract":"Flexible control of intrinsic chiroptical responses within compact nanostructures is crucial for flat optics, topological photonics, and chiroptics. However, previous approaches require complicated patterns with both in-plane and out-of-plane mirror symmetry breaking to achieve intrinsic chirality, and their chiroptical responses cannot be dynamically controlled as well. Herein, we demonstrated that near-perfect intrinsic circular dichroism (CD) can be achieved within a lithography-free structure consisting of the twisted bilayer α-MoO3 separated by a vanadium dioxide (VO2) film. By twisting the bilayer α-MoO3, dual-band intrinsic chiroptical responses can be realized due to the excitations of the hyperbolic phonon polaritons modes in the mid-infrared. It is the spin-selected average electric-field enhancement instead of the chiral absorption that is responsible for the intrinsic CD of the device. In addition, the chiroptical responses are insensitive to the variation of the thickness of the structure as well as the incident angle, and high contrast CD can be dynamically tuned by varying the volume fraction of VO2.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"36 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800253","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}
Peyman Parsa, Prasoon Kumar Shandilya, David P. Lake, Matthew E. Mitchell, Paul E. Barclay
The amplitude of self-oscillating mechanical resonators in cavity optomechanical systems is typically limited by nonlinearities arising from the cavity’s finite optical bandwidth. We propose and demonstrate a feedback technique for increasing this limit. By modulating the cavity input field with a signal derived from its output intensity, we increase the amplitude of a self-oscillating GHz frequency mechanical resonator by 22% (an increase in coherent phonon number of 50%), limited only by the achievable optomechanical cooperativity of the system. This technique will advance applications dependent on high dynamic mechanical stress, such as coherent spin-phonon coupling, as well as the implementation of sensors based on self-oscillating resonators.
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