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Comparative research on two surface conductivity models for the scattering of electromagnetic wave by the charged sphere
摘要： The surface conductivity model plays an important role in solving the electromagnetic scattering of microwave by the charged particle. We compared two models that can be used in the scattering of electromagnetic wave by the charged spherical particle. The results show that the extinction efficiency and the scattering efficiency calculated through these two models are much different in some cases, and which also affect by the particle size, refractive index, and its charged quantity. However, when the size parameter of particle is larger enough, the results from these two models became consistent with each other.
关键词： Charged spheres,Surface conductivity,Size parameters,Mie scattering,Scattering and extinction
更新于2025-09-23 15:23:52
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Analysis of Light Propagation on Physiological Properties of Neurons for Nanoscale Optogenetics
摘要： Miniaturization of implantable devices is an important challenge for future Brain-Computer Interface applications, and in particular for achieving precise neuron stimulation. For stimulation that utilizes light, i.e., optogenetics, the light propagation behavior and interaction at the nanoscale with elements within the neuron is an important factor that needs to be considered when designing the device. This paper analyses the effect of light behavior for a single neuron stimulation, and focuses on the impact from different cell shapes. Based on the Mie Scattering theory, the paper analyzes how the shape of the soma and the nucleus contributes to the focusing effect resulting in an intensity increase, which ensures that neurons can assist in transferring light through the tissue towards the target cells. At the same time, this intensity increase can in turn also stimulate neighboring cells leading to interference within the neural circuits. The paper also analyzes the ideal placements of the device with respect to the angle and position within the cortex that can enable axonal biophoton communications, which can contain light within the cell to avoid interference.
关键词： Optogenetics,Geometrical Optics Analysis,Nano Communications,Mie scattering
更新于2025-09-23 15:23:52
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Smartphone APP for Continuous Observation of Pollution Levels Due to Particulate Matter Measured by Laser Mie Scattering
摘要： The article is a work intended to meet the need for mobile monitoring of polluted air comprising of excessive fine particulate matter by a compact cellular phone application. The description is about the setting up of a laser scattering compact module with an Arduino like circuit board interface and the display on the handheld smart phone through Bluetooth while the person is on the move. Giving an introduction to the Mie Scattering method with a laser beam exposed to ambient (polluted) air through a miniature blower. With an introduction to the principles of Mie Scattering of laser beam, the work has resulted in a portable set-up which is worn by any one and the levels of particulate matter viewed on one’s smart phone through an ‘‘app’’ developed for this purpose.
关键词： Particulate matter,Mie Scattering of light,Pollution monitoring,MIT App. inventor,PM2.5 and PM10
更新于2025-09-23 15:21:01
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Nonlinear Optics in Dielectric Guided-Mode Resonant Structures and Resonant Metasurfaces
摘要： Nonlinear optics is an important area of photonics research for realizing active optical functionalities such as light emission, frequency conversion, and ultrafast optical switching for applications in optical communication, material processing, precision measurements, spectroscopic sensing and label-free biological imaging. An emerging topic in nonlinear optics research is to realize high efficiency optical functionalities in ultra-small, sub-wavelength length scale structures by leveraging interesting optical resonances in surface relief metasurfaces. Such artificial surfaces can be engineered to support high quality factor resonances for enhanced nonlinear optical interaction by leveraging interesting physical mechanisms. The aim of this review article is to give an overview of the emerging field of nonlinear optics in dielectric based sub-wavelength periodic structures to realize efficient harmonic generators, wavelength mixers, optical switches etc. Dielectric metasurfaces support the realization of high quality-factor resonances with electric field concentrated either inside or in the vicinity of the dielectric media, while at the same time operate at high optical intensities without damage. The periodic dielectric structures considered here are broadly classified into guided-mode resonant structures and resonant metasurfaces. The basic physical mechanisms behind guided-mode resonances, electromagnetically-induced transparency like resonances and bound-states in continuum resonances in periodic photonic structures are discussed. Various nonlinear optical processes studied in such structures with example implementations are also reviewed. Finally, some future directions of interest in terms of realizing large-area metasurfaces, techniques for enhancing the efficiency of the nonlinear processes, heterogenous integration, and extension to non-conventional wavelength ranges in the ultra-violet and infrared region are discussed.
关键词： harmonic generation,guided-mode resonance,four-wave mixing,Mie scattering,optical resonances,nonlinear optics,sub-wavelength gratings,Fano resonances,optical switching
更新于2025-09-23 15:19:57
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Mass Accommodation Coefficients of Water on Organics from Complementary Photoacoustic and Light Scattering Measurements on Laser-Trapped Droplets
摘要： The mass accommodation coefficient, αM, describes the liquid?vapor evaporation and condensation kinetics at interface. In spite of numerous experimental efforts, reliable values of αM are still not available for many substances. Here, we present a novel experimental technique, photothermal single-particle spectroscopy (PSPS), that allows for a robust retrieval of mass accommodation coefficients from three simultaneous independent measurements. PSPS combines resonant photoacoustic absorption spectroscopy with modulated Mie scattering measurements on single particles. We study the mass transport of water on organic aerosol droplets that are optically trapped using counter-propagating tweezers. We find the mass accommodation coefficient of water on a pure model organic that is fully miscible with water to be 0.021 at 296 K and to decrease by more than an order of magnitude when the temperature increases to 309 K. The experimentally observed temperature dependence of αM shows an Arrhenius behavior. Furthermore, the water content of the droplets is found to have a profound effect on αM is observed at low water concentrations, while at elevated water concentrations, we observe a 5-fold increase in αM. The technique presented in this work has the potential to become a reliable method for the retrieval of αM values at liquid?vapor interfaces, which are essential for accurate global climate and pharmaceutical aerosol inhalation modeling, to mention but a few.
关键词： temperature dependence,photoacoustic absorption spectroscopy,optical trapping,water transport,organic aerosol droplets,modulated Mie scattering,mass accommodation coefficient,Arrhenius behavior,PSPS,photothermal single-particle spectroscopy
更新于2025-09-23 15:19:57
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Mechanism of stimulated Mie scattering: Light-induced redistribution of self-assembled nanospheres of two-photon absorbing chromophore
摘要： We report the observation of backward stimulated Mie scattering (SMS) due to light-field induced spatial redistribution of self-assembled nanospheres of a two-photon resonant organic chromophore in water, pumped by ～10-ns laser pulses of ～816-nm wavelength. The pump-energy threshold for generating backward stimulated scattering in such a system is remarkably lower than that in pure water. The gain of backscattering originates from an induced Bragg grating that reflects partial energy from the pump beam into the backward Mie scattering beam. Based on the experimental fact that the time-delay of the SMS pulse onset depends on both the pump level and the viscosity of the solvent, a physical model of SMS generation is proposed. Our experimental results have shown that the major contribution to the formation of an induced Bragg grating is spatial redistribution of nanoparticles suspended in the liquid. These nanoparticles are driven by a force that is proportional to the intensity gradient of the standing-wave field resulting from interference between the forward pump beam and the backward Mie scattering beam. When the nanoparticle motion is frozen in a gel-like medium, no SMS is observed, which experimentally supports the validity of the proposed physical model.
关键词： two-photon absorbing chromophore,stimulated Mie scattering,nanospheres,light-induced redistribution,Bragg grating
更新于2025-09-19 17:13:59
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Mass Producible Low-Loss Broadband Optical Waveguides in Eagle2000 by Femtosecond Laser Writing
摘要： Optical waveguides were fabricated in alkaline earth boro-aluminosilicate glass, by femtosecond laser direct writing, with varying pulse energy and scan velocity. A spectral characterization, from 500 nm to 1700 nm, was made in order to determine their losses and understand its dependence on the processing parameters. Three major loss mechanisms were identified. At longer wavelengths, loss is mainly due to weak coupling. On the other hand, the behavior at shorter wavelengths is governed by propagation loss due to Rayleigh scattering, which was shown to be practically eliminated (<0.05 dB· cm?1· μm4) at higher scan velocities. Bulk absorption was also found to have an influence in the propagation losses at higher wavelengths. The combination of intermediate pulse energies (between 125-250 nJ) and high scan velocities (above 6 cm/s) allowed the fabrication of optical waveguides offering low losses across the entire range of wavelengths tested, facilitating applications that require larger wavelength working bands. Furthermore, since optimal fabrication conditions are achieved at higher scanning velocities, mass production with reduced fabrication times can be achieved.
关键词： femtosecond laser direct writing,Rayleigh scattering,propagation loss,Coupling loss,Mie scattering,integrated optics,low-loss broadband optical waveguides,mass production
更新于2025-09-12 10:27:22
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Self-Catalytic-Grown SnOx Nanocones for Light Outcoupling Enhancement in Organic Light-Emitting Diodes
摘要： Light extraction in organic light-emitting diodes (OLEDs) was improved by applying SnOx nanocones grown via thermal annealing in a low-O2 atmosphere. SnOx was easily fabricated through thermal processing after Sn deposition. The diameter of the SnOx nanocones was controlled by changing the deposition thickness of Sn. The SnOx nanocones induced strong Mie scattering, which reduced the total internal reflection in the glass substrate. Consequently, the OLED with SnOx nanocones exhibited a 23% increase in the external quantum efficiency compared with a reference device.
关键词： Mie scattering,SnOx nanostructure,light extraction,organic light-emitting diodes (OLEDs),FDTD simulation
更新于2025-09-11 14:15:04
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Exploring the applicability and limitations of selected optical scattering instruments for PM mass measurement
摘要： Two optical scattering instruments for particle mass measurement, the Thermo Personal Data RAM (PDR-1500) and the TSI Environmental DustTrak DRX (Model 8543) were evaluated by (1) using poly- and mono-disperse test aerosol in the laboratory, and (2) sampling ambient aerosol. The responses of these optical scattering instruments to different particle characteristics (size, composition, concentration) were compared with responses from reference instruments. A Mie scattering calculation was used to explain the dependence of the optical instruments’ response to aerosol size and composition. Concurrently, the detection efficiency of one Alphasense Optical Particle Counter (OPC-N2) was evaluated in the laboratory as well. The relationship between aerosol mass concentration and optical scattering was determined to be strongly dependent on aerosol size and to a lesser extent on aerosol composition (as reflected in the refractive indices of the materials tested) based on ambient measurements. This confirms that there is no simple way to use optical scattering instruments over a wide range of conditions without adjustments based on knowledge of aerosol size and composition. In particular, a test period measuring ambient aerosol with optical scattering instruments and a mass based method (an Aerodyne Aerosol Mass Spectrometer) determined that roughly two thirds of the variance (R2 = 0.64) of the optical to mass signal ratio is explained by the aerosol mass median diameter alone. These observations and calculations help evaluate the applicability and limitations of these optical scattering instruments, and provide guidance to designing suitable applications for each instrument by considering aerosol sources and aerosol size.
关键词： aerosol composition,optical scattering instruments,aerosol size,PM mass measurement,Mie scattering calculation
更新于2025-09-09 09:28:46
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Resonances in small scatterers with impedance boundary
摘要： With analytical (generalized Mie scattering) and numerical (integral-equation-based) considerations we show the existence of strong resonances in the scattering response of small spheres with a lossless impedance boundary. With increasing size, these multipolar resonances are damped and shifted with respect to the magnitude of the surface impedance. The electric-type resonances are inductive and the magnetic ones capacitive. Interestingly, these subwavelength resonances resemble plasmonic resonances in small negative-permittivity scatterers but occur in two families unlike the only-electric multipoles in the plasmonic case. The fundamental dipolar mode is also analyzed from the point of view of surface currents and the effect of the change of the shape into a nonspherical geometry. For dissipative impedance scatterers, maximum absorption is shown to result in the matched-impedance case.
关键词： scattering,Mie scattering,resonances,subwavelength,impedance boundary
更新于2025-09-09 09:28:46