Optical Scattering Research Articles

Computing Riemann zeros with light scattering

Finding hidden order within disorder is a common interest in material science, wave physics, and mathematics. The Riemann hypothesis, stating the locations of nontrivial zeros of the Riemann zeta function, tentatively characterizes statistical order in the seemingly random distribution of prime numbers. This famous conjecture has inspired various connections with different branches of physics, recently with non-Hermitian physics, quantum field theory, trapped-ion qubits, and hyperuniformity. Here we develop the computing platform for the Riemann zeta function by employing classical scattering of light. We show that the Riemann hypothesis suggests the landscape of semi-infinite optical scatterers for the perfect reflectionless condition under the Born approximation. To examine the validity of the scattering-based computation, we investigate the asymptotic behaviors of suppressed reflections with the increasing number of scatterers and the emergence of multiple scattering. The result provides another bridge between classical physics and the Riemann zeros, exhibiting the design of wave devices inspired by number theory. Published by the American Physical Society 2024

Microstructure evolution and springback behavior in single-pass roll bending of magnesium alloy plates

Microstructure evolution and springback behavior in single-pass roll bending of magnesium alloy plates

Study of hybrid nanoscatterer for enhancing light efficiency of quantum dot-converted light-emitting diodes

Study of hybrid nanoscatterer for enhancing light efficiency of quantum dot-converted light-emitting diodes

Buffer Layer Dependence of Defectivity in 200mm 4H-SiC Homoepitaxy

The effect of increasing Buffer Layer (BL) thickness on crystal defectivity has been investigated in 4° off-axis 4H-SiC homoepitaxy on 200mm substrates coming from different suppliers. The results, based on optical microscopy and scatter light methods, show a slight increase in morphological defects in the case of a thicker BL with respect to the standard thickness for both suppliers.

Measurements of the Optical Scattering Properties of Single Suspended Particles and Implications for Atmospheric Studies: A Review

Measurements of the Optical Scattering Properties of Single Suspended Particles and Implications for Atmospheric Studies: A Review

Low-Frequency Coherent Raman Imaging Robust to Optical Scattering.

We demonstrate low-frequency interferometric impulsive stimulated Raman scattering (ISRS) imaging with high robustness to distortions by optical scattering. ISRS is a pump-probe coherent Raman spectroscopy that can capture Raman vibrational spectra. Recording of ISRS spectra requires isolation of a probe pulse from the pump pulse. While this separation is simple in nonscattering specimens, such as liquids, scattering leads to significant pump pulse contamination and prevents the extraction of a Raman spectrum. We introduce a robust method for ISRS microscopy that works in complex scattering samples. High signal-to-noise ISRS spectra are obtained even when the pump and probe pulses pass through many scattering layers.

Corneal densitometry in Chinese adults with healthy corneas: associations with sex, age, ocular metrics, and optical characteristics

BackgroundStandardized corneal densitometry (CD) values in large samples of healthy Chinese individuals are scarce. Therefore, we aimed to determine the standard CD values using a Scheimpflug camera in healthy corneas, investigate the correlations of sex, age, and ocular parameters with corneal density, and explore the impact of corneal density on the forward scattering and optical quality of the eye.MethodsThis retrospective observational study involved 990 healthy Chinese individuals, including 494 males and 496 females (mean age: 23.88 ± 6.90 years). The CD values at various depths and radial areas of 0–12 mm were measured using a Scheimpflug camera. Densitometric measurements were expressed in standardized grayscale units (GSU). The optical scatter index (OSI), modulation transfer function cutoff values (MTFcutoff), and Strehl’s ratio (SR) were also determined using an optical quality analysis system.ResultsThe average CD within a 12 mm diameter area was 16.26 ± 1.35 GSU. The highest and lowest optical densities at different depths were observed in the anterior (21.41 ± 2.16 GSU) and posterior (12.00 ± 1.01 GSU) layers, respectively (P < 0.001). Similarly, the maximum and minimum optical densities at different radial areas were observed in the 10–12 mm (14.09 ± 0.93 GSU) and 2–6 mm (25.93 ± 4.77 GSU) circles, respectively (P < 0.001). There was no significant difference in the average CD within a 12 mm diameter area between males and females (P > 0.05). However, upon adjusting for age, central corneal thickness (CCT), corneal curvature, white-to-white (WTW) corneal diameter, and axial length, females exhibited a greater average CD within the 12 mm diameter and in the 6–10 mm and 10–12 mm circles than males. Age-related changes in CD were evident, except in the 2–6 mm circle. CCT, corneal curvature, WTW corneal diameter, and partial depth correlated with CD in the radial area, and CD in different areas correlated with the OSI, MTFcutoff, and SR (P < 0.05).ConclusionsThis study provides the normative CD measurement data of Chinese adults with healthy corneas, emphasizing the significance of sex, age, CCT, corneal curvature, and WTW corneal diameter in CD evaluation. Notably, elevated CD can lead to increased forward scattering within the eye, thereby affecting the optical quality.

Finite-element assembly approach of optical quantum walk networks

We present a finite-element approach for computing the aggregate scattering matrix of a network of linear coherent scatterers. These might be optical scatterers or more general scattering coins studied in quantum walk theory. While techniques exist for two-dimensional lattices of feed-forward scatterers, the present approach is applicable to any network configuration of any collection of scatterers. Unlike traditional finite-element methods in optics, this method does not directly solve Maxwell’s equations; instead it is used to assemble and solve a linear, coupled scattering problem that emerges after Maxwell’s equations are abstracted within the scattering matrix method. With this approach, a global unitary is assembled corresponding to one time step of the quantum walk on the network. After applying the relevant boundary conditions to this global matrix, the problem becomes non-unitary and possesses a steady-state solution that is the output scattering state. We provide an algorithm to obtain this steady-state solution exactly using a matrix inversion, yielding the scattering state without requiring a direct calculation of the eigenspectrum. The approach is then numerically validated on a coupled-cavity interferometer example that possesses a known, closed-form solution. Finally, the method is shown to be a generalization of the Redheffer star product, which describes scatterers on one-dimensional lattices (2-regular graphs) and is often applied to the design of thin-film optics, making the current approach an invaluable tool for the design and validation of high-dimensional phase-reprogrammable optical devices and study of quantum walks on arbitrary graphs.

Time-gated imaging through dense fog via physics-driven Swin transformer

Imaging through the fog is valuable for many areas, such as autonomous driving and cosmic exploration. However, due to the influence of strong backscattering and diffuse reflection generated by the dense fog on the temporal-spatial correlations of photons returning from the target object, the reconstruction quality of most existing methods is significantly reduced under dense fog conditions. In this study, we describe the optical scatter imaging process and propose a physics-driven Swin Transformer method utilizing Time-of-Flight (ToF) and Deep Learning principles to mitigate scattering effects and reconstruct targets in conditions of heterogeneous dense fog. The results suggest that, despite the exponential decrease in the number of ballistic photons as the optical thickness of fog increases, the Physics-Driven Swin Transformer method demonstrates satisfactory performance in imaging targets obscured by dense fog. Importantly, this article highlights that even in dense fog imaging experiments with optical thickness reaching up to 3.0, which exceeds previous studies, commonly utilized quantitative evaluation metrics like PSNR and SSIM indicate that our method is cutting-edge in imaging through dense fog.

A Comprehensive Survey on Optical Scattering Communications: Current Research, New Trends, and Future Vision

A Comprehensive Survey on Optical Scattering Communications: Current Research, New Trends, and Future Vision

Optical Scattering Properties of Particles and Group Particles with Core-Shell Structure

Optical Scattering Properties of Particles and Group Particles with Core-Shell Structure

Restoration of Binocular Images Degraded by Optical Scattering through Estimation of Atmospheric Coefficients.

A binocular vision-based approach for the restoration of images captured in a scattering medium is presented. The scene depth is computed by triangulation using stereo matching. Next, the atmospheric parameters of the medium are determined with an introduced estimator based on the Monte Carlo method. Finally, image restoration is performed using an atmospheric optics model. The proposed approach effectively suppresses optical scattering effects without introducing noticeable artifacts in processed images. The accuracy of the proposed approach in the estimation of atmospheric parameters and image restoration is evaluated using synthetic hazy images constructed from a well-known database. The practical viability of our approach is also confirmed through a real experiment for depth estimation, atmospheric parameter estimation, and image restoration in a scattering medium. The results highlight the applicability of our approach in computer vision applications in challenging atmospheric conditions.

All-a-glow: spectral characteristics confirm widespread fluorescence for mammals.

Mammalian fluorescence has been reported from numerous species of monotreme, marsupial and placental mammal. However, it is unknown how widespread this phenomenon is among mammals, it is unclear for many species if these observations of 'glowing' are true fluorescence and the biological function of fluorescence remains undetermined. We examined a wide range of mammal species held in a museum collection for the presence of apparent fluorescence using UV light, and then analysed a subset of preserved and non-preserved specimens by fluorescent spectroscopy at three different excitation wavelengths to assess whether the observations were fluorescence or optical scatter, and the impact of specimen preservation. We also evaluated if fluorescence was related to biological traits. We found that fluorescence is widespread in mammalian taxa; we identified examples of the phenomena among 125 species representing all 27 living mammalian orders and 79 families. For a number of model species, there was no evidence of a corresponding shift in the emission spectra when the wavelength of excitation was shifted, suggesting that observations of 'glowing' mammals were indeed fluorescence. Preservation method impacted the intensity of fluorescence. Fluorescence was most common and most intense among nocturnal species and those with terrestrial, arboreal and fossorial habits, with more of their body being more fluorescent. It remains unclear if fluorescence has any specific biological role for mammals. It appears to be a ubiquitous property of unpigmented fur and skin but may function to make these areas appear brighter and therefore enhance visual signalling, especially for nocturnal species.

Photoacoustic tomography as a method to estimate the optical fluence distribution in turbid media.

Currently, there are no non-invasive experimental methods available for measuring optical fluence distributions in tissue. We present photoacoustic tomography (PAT) as a method to approximate the relative optical fluence distribution in a homogeneous optically scattering medium. Three-dimensional photoacoustic images were captured with a near-full view PAT scanner in phantoms with known optical absorption and scatter properties. Resultant 3D PAT images were compared to the expected optical fluence distributions from Monte Carlo simulations and diffusion theory using volumetric and shape analysis. Volumetric analysis of PAT images compared well with the optical fluence distributions from simulation. Dice similarity coefficients ranged from 51 to 82%. The reduced scattering coefficient estimated from PAT images compared well to estimates from simulations for values below 0.5 mm-1. Near full-view PAT has been found to be useful for estimating the optical fluence distribution in an optically scattering medium. Further development is needed to extend the measurement range.

Aerosol Optical Properties of Extreme Global Wildfires and Estimated Radiative Forcing With GCOM‐C SGLI

AbstractTo understand the climate impact of the wildfires, it is essential to monitor the aerosol emissions from biomass burning and to estimate their optical properties and radiative forcing. This study analyzed wildfires in Brazil, Angola, Australia, California, Siberia, and South‐east Asia that occurred after 2018 using data obtained with the Second‐generation GLobal Imager (SGLI) onboard Global Change Observation Mission—Climate which is a polar‐orbit satellite launched by JAXA on 23 December 2017. We showed the SGLI‐based 4‐year variation of the aerosol optical properties, Aerosol Optical Thickness, Ångström Exponent (AE), and Single Scattering Albedo (SSA) for each region complemented with other satellite‐ and ground‐based data. From the SSA and AE relationship analyses, we confirmed that their optical properties depend on the relative humidity and type of burned vegetation, which is consistent with the previous studies. Moreover, we estimated the net incoming radiation at the top of the atmosphere during the intense fire periods to understand the impact of the direct effect of biomass burning aerosols on radiative forcing. The estimates show a significant negative radiative forcing (i.e., a cooling effect) over the ocean (−78 and −96 Wm−2in Australia and California, respectively). In contrast, small values are observed over land (∼−10 Wm−2for all six regions). Therefore, taking the regional characteristics of the optical properties and surface reflectance into account is necessary to estimate the effect on radiative forcing and future impacts of a short‐lived climate forcer from wildfires.

Retracted: Application Effect Analysis of the Mie Scattering Theory Based on Big Data Analysis Technology in the Optical Scattering Direction

Retracted: Application Effect Analysis of the Mie Scattering Theory Based on Big Data Analysis Technology in the Optical Scattering Direction

A comparison of atmospheric aerosol absorption properties from the MERRA-2 reanalysis with AERONET

A comparison of atmospheric aerosol absorption properties from the MERRA-2 reanalysis with AERONET

Mathematical model of radiation scattering on a quasi – periodic structure in an optical fiber

The paper considers a quasi – periodic microheterogeneity structure formed under the effect of optical fiber melting, which can be used as a sensitive element for an optical sensor based on a Fabry – Perot interferometer or an optical radiation scatterer with improved flexibility and strength parameters. Mathematical modeling of the process of transmission and reflection of radiation on the microcavities of the intrafiber structure will make it possible to predict the characteristics of the developed sensors. The simulation was carried out in the COMSOL Multyphysics simulation package. A section of a single – mode SMF-28e fiber with microinhomogeneities located in the core, the dimensions of which were measured in the course of an empirical study, is considered. To solve the problem, a system of equations was compiled that describes the propagation of a plane electromagnetic wave in matter. The results obtained showed that the calculated reflection spectrum qualitatively coincides with the measured value, but does not describe it with high accuracy. This may be due to the fact that the model does not take into account intermode interference in the fiber, and does not have an introduced melt zone around microcavities, since such a melt zone has a complex refractive index distribution and composition

Investigation of the Effect of γ-Irradiation on the Optical Properties of Lithium Niobate by Optical Absorption and Raman Scattering Methods

The paper presents the results of studies of the effect of γ-irradiation on the photorefractive properties of lithium niobate (LiNbO3), using optical absorption and Raman spectroscopy of Raman scattering. It is shown that with γ-irradiation, the optical density of the lithium niobate crystal increases, i.e. the shift of the optical absorption edge towards long waves, with an increase in the irradiation dose, the refractive index increases, in the interval 1300 ÷ 1600 cm–1 with γ-irradiation at a frequency of 1375 cm–1, peaks appear due to centers of significant changes in Raman scattering frequencies.

Broadband Microwave Photonic Frequency Measurement Based on Optical Spectrum Manipulation and Stimulated Brillouin Scattering

In this article, a broadband frequency measurement system based on optical spectrum manipulation and stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated, which can implement wide-range and high-resolution frequency measurement, and generate corresponding broadband interference signals in some frequency bands, that is, it has versatility. Since the frequency range of the pump light to excite SBS is expanded based on the optical spectrum manipulation and high resolution is ensured by the narrow scattering spectrum of SBS, high-resolution spectrum measurement covering a wide frequency band is finally implemented. In addition, the double sideband pump light can be used as the source of electronic interference signal. In the experiments, the frequency measurement range of the proposed system is tested to be 0.03–44 GHz, and the resolution is up to 3 MHz. Furthermore, the frequency measurement and electronic interference sharing the same work band can be carried out in the ranges of 6.3367–7.8367 GHz and 20.36–22.16 GHz.