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Surface-enhanced optical absorption and induced heating in tapered silicon nanoprobes

JOURNAL OF OPTICAL TECHNOLOGY 2024年第5期91卷 316-322页

作者： Izbasarova, Elina a. Gazizov, Almaz r. Kharintsev, Sergey s. Kazan Fed Univ Kazan Russia Acad Sci Republ Tatarstan Inst Appl Res Kazan Russia

Subject of study. This study investigates the correlation between the heating temperature and the mesoscopic shape of the Si probe of an atomic force microscope subjected to medium-intensity laser irradiation (5 mW/cm2) in the presence of a rough metal substrate. Aim of study. This study aims to quantitatively assess the dependence of optical-field enhancement and induced heating of the tip of a tapered Si nanoprobe, under laser irradiation, on the radius of curvature and cone angle of the probe tip, the distance between the tip and substrate, and the surface roughness of an Au substrate. method. The localization of the electromagnetic field in the gap between a Si nanoantenna and a defect on the surface of an Au substrate was simulated using the finite-difference time-domain method. A thin Au coating (thickness up to 50 nm) on a glass substrate was used as a plasmonic surface. Owing to the excitation of surface plasmon resonance, such a coating enhances the absorption of light and increases the heating temperature of the Si optical antenna. Main results. The influence of the polarization angle of the incident laser radiation on the distribution of the electric field near the tip of the probe was examined. Only the component of the incident light field along the direction of the probe axis was enhanced near the tip of the Si cantilever. The influence of various parameters, including the radius of curvature, cone angle of the tip of the Si nanoantenna, distance between the probe and substrate, and surface roughness of the Au substrate, on the maximum temperature in the tip region of the Si probe was investigated. The probe temperature was found to decrease with decreasing cone angle of the probe, whereas the temperature of the cantilever tip decreased as the cone angle of the probe tip increased. The dependence of temperature on the radius of curvature of the Si nanoantenna tip in the presence of an Au substrate was evaluated. With an increase in the surface roughnes

关键词： Atomic force microscopy finite-difference time-domain method Localized surface plasmons Material properties Optical antennas Surface plasmon resonance

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Selective active resonance tuning for multi-mode nonlinear photonic cavities

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OPTICS EXPRESS 2024年第8期32卷 13396-13407页

作者： Logan, Alan D. Yama, Nicholas S. Fu, Kai-Mei C. Univ Washington Dept Phys Seattle WA 98195 USA Univ Washington Dept Elect & Comp Engn Seattle WA 98195 USA Phys Sci Div Pacific Northwest Natl Lab Richland WA 99352 USA

Resonant enhancement of nonlinear photonic processes is critical for the scalability of applications such as long-distance entanglement generation. To implement nonlinear resonant enhancement, multiple resonator modes must be individually tuned onto a precise set of process wavelengths, which requires multiple linearly -independent tuning methods. Using coupled auxiliary resonators to indirectly tune modes in a multi -resonant nonlinear cavity is particularly attractive because it allows the extension of a single physical tuning mechanism, such as thermal tuning, to provide the required independent controls. Here we model and simulate the performance and tradeoffs of a coupled -resonator tuning scheme which uses auxiliary resonators to tune specific modes of a multi -resonant nonlinear process. Our analysis determines the tuning bandwidth for steady-state mode field intensity can significantly exceed the inter -cavity coupling rate g if the total quality factor of the auxiliary resonator is higher than the multi -mode main resonator. Consequently, over -coupling a nonlinear resonator mode to improve the maximum efficiency of a frequency conversion process will simultaneously expand the auxiliary resonator tuning bandwidth for that mode, indicating a natural compatibility with this tuning scheme. We apply the model to an existing small -diameter triply -resonant ring resonator design and find that a tuning bandwidth of 136 GHz approximate to 1.1 nm can be attained for a mode in the telecom band while limiting excess scattering losses to a quality factor of 10 6 . Such range would span the distribution of inhomogeneously broadened quantum emitter ensembles as well as resonator fabrication variations, indicating the potential for the auxiliary resonators to enable not only low -loss telecom conversion but also the generation of indistinguishable photons in a quantum network. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Coupled mode theory Coupled resonators finite-difference time-domain method Optical resonators Resonant modes Ring resonators

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Transverse manipulation of an electron beam by circularly polarized Laguerre-Gaussian modes

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OPTICS EXPRESS 2024年第26期32卷 46213-46224页

作者： Lan, Yung-chiang Lin, Ming-chieh Natl Cheng Kung Univ Dept Photon Tainan 70101 Taiwan Natl Cheng Kung Univ Meta nanoPhoton Ctr Tainan 70101 Taiwan Hanyang Univ Dept Elect & Biomed Engn Multidisciplinary Computat Lab Seoul 04763 South Korea

This study investigates the modulation of the azimuthal velocity of electrons in an electron beam using circularly polarized Laguer re-Gaussian (LG) modes. The finite-difference time-domain particle-in-cell (FDTD-PIC) method is employed for this purpose. After obtaining the orbital and spin angular momenta of the LG mode, the distribution of the electrons' azimuthal velocity (i.e., the distribution of angular momentum) exhibits 3D spiral patterns. The number of strands in these spirals corresponds to the sum of the quantum numbers associated with the orbital and spin angular momenta of the LG mode. Furthermore, these spiral patterns rotate in the same direction as the LG mode and move along with it. In contrast, the electrons in the beam undergo a gyromotion along their forward direction (without the application of an external magnetic field in this study). The rotation direction of the electrons is primarily determined by the sign of their initial azimuthal velocity after acquiring angular momenta from the LG mode. Additionally, all electrons share the same gyrofrequency, which is much lower than the LG mode's frequency. This gyrofrequency can be manipulated by the frequency, electric field strength, and beam waist size of the LG mode. Moreover, increasing the electric field strength allows a larger-current electron beam to be confined within the LG mode. The gyromotion and confinement effects of electrons are primarily due to the transverse ponderomotive force generated by the LG mode. It is demonstrated that the manipulation of an electron beam can be realized by using circularly polarized LG modes. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： Cylindrical lenses finite-difference time-domain method Phase plates Ring resonators Spiral phase Whispering gallery modes

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Superconducting nanowire single-photon detector with polarization insensitivity, ultrafast response, and high efficiency

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OPTICS EXPRESS 2024年第9期32卷 15537-15545页

作者： Gu, Min Zhang, Shangkun Wang, Xianghao Wang, Wencong Liu, Dongmei Wu, Xianqiu South China Normal Univ Guangdong Basic Res Ctr Excellence Struct & Fundam Key Lab Atom & Subatom Struct & Quantum Control Minist EducSch Phys Guangzhou 510006 Peoples R China South China Normal Univ Guangdong Prov Key Lab Quantum Engn & Quantum Mat Guangdong Hong Kong Joint Lab Quantum Matter Guangzhou 510006 Guangdong Peoples R China Quantum Sci Ctr Guangdong Hong Kong Macao Greater Shenzhen 518000 Peoples R China

This study proposed what we believe to be a novel method for fabricating superconducting nanowire single-photon detectors (SNSPDs) with high efficiency, polarization insensitivity, and ultrafast response. To achieve these properties in niobium nitride (NbN) SNSPDs, the periodic four-split rings (PFSR) were positioned above the nanowires. This design uses the localized surface plasmon resonance to enhance the electric field around nanowires. For an incident light with a wavelength of 1550 nm, the PFSR-SNSPD structure achieved a polarization extinction ratio of 1.0064 and absorptions of 88.94% and 88.37% under TE and TM polarizations, respectively. The nanowire length was reduced by 85% using a meandering nanowire arrangement with a fill factor of 0.074.

关键词： Extinction ratios finite-difference time-domain method Localized surface plasmon resonance Quantum key distribution Ring resonators Superconducting nanowire single photon detectors

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Multi-objective scintillator shape optimization for increased photodetector light collection

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2024年第9期41卷 2014-2032页

作者： Reales, G. Van Keulen, F. Aragon, A. M. Goosen, J. F. L. Bornheim, A. Delft Univ Technol Fac Mech Engn Mekelweg 2 NL-2628CD Delft Netherlands CALTECH Pasadena CA 91125 USA

Inorganic scintillators often use exotic, expensive materials to increase their light yield. Although material chemistry is a valid way to increase the light collection, these methods are expensive and limited to the material properties. As such, alternative methods such as the use of specific reflective coatings and crystal optical shapes are critical for the scintillator crystal design procedure. In this paper, we explore the modeling of a scintillator and silicon-photomultiplier (SiPM) assembly detector using GEANT4. GEANT4, an open-source software for particle-matter interaction based on ray-tracing, allows the modeling of a scintillator-based detector while offering methods to simplify and study the computational requirements for a precise calculation of the light collection. These studies incorporate two different geometries compatible with the barrel timing layer (BTL) particle detector that is being built for the compact muon solenoid (CME) experiment at CERN. Furthermore, the geometry of our model is parameterized using splines for smoother results and meshed using GMSH to perform genetic numerical optimization of the crystal shape through genetic algorithms, in particular non-dominated sorting genetic algorithm II (NGSAII). Using NSGA-II, we provide a series of optimized scintillator geometries and study the trade-offs of multiple possible objective functions including the light output, light collection, light collection per energy deposited, and track path length. The converged Pareto results according to the hypervolume indicator are compared to the original simplified design, and a recommendation towards the use of the light collection per energy deposition and track path length is given based on the results. The results provide increases in this objective of up to 18% for a constant volume for a geometry compatible with the current design of the BTL detector. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artifi

关键词： 3D printing finite-difference time-domain method Genetic algorithms Material properties Optical coatings Radiation detectors

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Ab initio simulation of imaging of wavelength-sized objects and estimation of resolution

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APPLIED OPTICS 2024年第5期63卷 1282-1291页

作者： Maslov, A. V. Erykalin, A. A. Univ Nizhny Novgorod Dept Radiophys Nizhnii Novgorod 603022 Russia

Image characterization in microscopy, in particular, the estimation of its resolution, requires detailed knowledge of its relation to the object. For objects with sizes comparable to or smaller than the operating wavelength, such a relation can be obtained only by considering electromagnetic scattering described by the Maxwell equations. Here we follow precisely the steps involved in the image formation in microscopy with broad angle illumination-starting from the Maxwell equations to find the scattered far fields for each plane wave, projecting them into a sensor array, and finally assembling the incoherent image by adding all coherent contributions. We consider a classical object-a narrow slit in an absorbing screen, which is taken as a very thin chromium film deposited on a glass substrate. The inapplicability of the Kirchhoff approximation for such a slit is addressed, and the calculated image is subsequently analyzed to evaluate its intrinsic resolution using a point spread function. The difference in image intensities defined using the Poynting vector and the electric field intensity is also discussed. (c) 2024 Optica Publishing Group

关键词： Cylindrical lenses Electromagnetic scattering finite element method finite-difference time-domain method Imaging systems Total internal reflection

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Mask correction method for surface plasmon lithography

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APPLIED OPTICS 2024年第2期63卷 499-505页

作者： Ma, Le Zhang, Libin He, Jianfang Ding, Huwen Wei, Yayi Chinese Acad Sci EDA Ctr Inst Microelect Beijing 100029 Peoples R China Univ Chinese Acad Sci Sch Integrated Circuits 19A Yuquan Rd Beijing 100049 Peoples R China

Surface plasmon lithography (SPL) has emerged as an innovative approach to nano-fabrication, offering an alternative to traditional patterning methods. To enhance its pattern fidelity in manufacturing, it is essential to incorporate mask correction to reduce critical dimension (CD) errors between the intended target features and the photoresist image. Traditionally, the aerial image of SPL has been modeled and simulated using methods such as finite difference time domain (FDTD) or rigorous coupled wave analysis (RCWA). These models have allowed us to obtain aerial images of the mask patterns. However, relying solely on the aerial image proves insufficient for meeting the rigorous manufacturing standards for mask correction. In our research, we propose a comprehensive model that combines the optical model, employing the FDTD method, and the resist model, tailored to the specific surface plasmon lithography process. Test patterns were meticulously designed with a target CD of 130 nm, and the model was applied to simulate these test patterns, producing the after-development image (ADI) under predefined process conditions. Following a thorough analysis and data processing of the test patterns and ADI data, we established rule tables for the correction of both 1D line patterns and line end patterns. The simulation results unequivocally demonstrate the improved CD error performance achieved by the post-corrected patterns. (c) 2024 Optica Publishing Group

关键词： Extreme ultraviolet lithography finite-difference time-domain method Imaging systems Lithography Optical systems Rigorous coupled wave analysis

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Numerical simulation of split ring resonator near-fields and antiferromagnetic magnon hybridization

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OPTICAL MATERIALS EXPRESS 2024年第3期14卷 687-695页

作者： Heligman, Daniel M. Potts, Alex M. Aguilar, R. Valdes Ohio State Univ Dept Phys Columbus OH 43210 USA Univ Calif Santa Barbara Santa Barbara CA USA

We report on the results of finite difference time domain (FDTD) simulations of the terahertz response of a split ring resonator (SRR) metamaterial coupled to a hypothetical antiferromagnetic material (AFM) characterized by a magnon resonance. We find a hybridization of the SRR's local magnetic field and the magnon, which manifests as an avoided crossing in the far-field transmission spectrum. We show that the strong light-matter coupling can be modelled via a two coupled oscillator model. We further evaluate the SRR-AFM coupling strength by varying the physical separation with a dielectric spacer between them. We find strong coupling for spacers thinner than 3 mu m, suggesting far-field transmission measurements of metamaterial near-fields to be a versatile platform to investigate magnetic excitations of quantum materials.

关键词： finite-difference time-domain method Negative refraction Numerical simulation Ring resonators Terahertz time-domain spectroscopy Transmission measurement

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Optical properties of nanoparticles in blood : considering blood absorption

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APPLIED OPTICS 2024年第35期63卷 8959-8964页

作者： Cheng, Ning Li, Xingcai Wang, Juan Ma, Xin Lanzhou Univ Coll Civil Engn & Mech Key Lab Mech Disaster & Environm Western China Minist Educ China Lanzhou 730000 Peoples R China Ningxia Univ Sch Phys Yinchuan 750021 Peoples R China Ningxia Univ Xinhua Coll Yinchuan 750021 Peoples R China Ningxia Univ Sch Elect & Elect Engn Yinchuan 750021 Peoples R China

Nanomedicine is emerging as a crucial avenue for exploring new therapeutic and diagnostic techniques in the medical field. Effective monitoring of the dispersion concentration of nanoparticles using optical methods is an extremely important topic in this area. However, existing research has not recognized that the light absorption of blood can lead to significant errors in related optical measurements. This paper, considering the absorption properties of the background medium, meticulously discusses the variations in the single-scattering characteristics of nanoparticles in plasma and whole blood, and analyzes the influence of parameters such as incident wavelength, particle size, refractive index, and background medium refractive index. The results indicate that neglecting the light absorption of the background medium may lead to differences of up to approximately 50% in the results, but this is also influenced by parameters such as incident wavelength, particle size, and refractive index. Furthermore, there are still significant differences in the variations of the single-scattering properties of nanoparticles with identical characteristics in plasma and whole blood. These results indicate the importance of in-depth research into calibration techniques for optical instruments in monitoring nanoparticles in the blood, and further enhance the development of nanoparticle monitoring technology in nanomedicine. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Electromagnetic scattering finite-difference time-domain method Mie scattering Multiple scattering Optical properties Scattering theory

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Compact inverse-designed tilted waveguide crossing

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OPTICS LETTERS 2025年第6期50卷 1889-1892页

作者： Zhang, Xiaoyan Xie, Wu Leong, Chewping Gao, Feng ASTAR ISCE2 Singapore 627833 Singapore Adv Micro Foundry Pte Ltd Singapore 117685 Singapore Pengcheng Lab Shenzhen 518063 Guangdong Peoples R China

Waveguide crossings are key components for increasing integration density and routing flexibility. We propose a novel, to the best of our knowledge, compact, tilted silicon waveguide crossing designed using inverse design methods, specifically optimized to minimize both insertion loss and crosstalk. Through adjoint optimization algorithms and finite-difference time-domain simulations, we achieve a significant reduction in crosstalk from -46 dB at 90 degrees to -54 dB at 86 degrees, with a remarkably low insertion loss of -0.14 dB at 1310 nm. The footprint is further minimized to only 8 x 8 mu m2, setting what we believe to be a new benchmark in terms of both size and performance compared to existing silicon waveguide crossings. The impact of the tilt angle on performance is thoroughly analyzed through both simulations and experimental validation. This device highlights the potential of inverse design to deliver optimized overall performance while maintaining an ultra-compact footprint. Fabricated on a commercial foundry, with its low loss, low crosstalk, and small size, our waveguide crossing is ideally suited for high-density photonic integrated circuits, offering promising applications in data centers and quantum photonics. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

关键词： Bend loss Coupling efficiency finite-difference time-domain method Inverse design Optical computing Photonics

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