Multiple-scattering method applied to gyrotropic media

Focusing large spectral bandwidths through scattering media

Wavefront shaping is a powerful method to refocus light through a scattering medium. Its application to large spectral bandwidths or multiple wavelengths refocusing for nonlinear bio-imaging in-depth is however limited by spectral decorrelations. In this work, we demonstrate ways to access a large spectral memory of a refocus in thin scattering media and thick forward-scattering biological tissues. First, we show that the accessible spectral bandwidth through a scattering medium involves an axial spatio-spectral coupling, which can be minimized when working in a confocal geometry. Second, we s…

Strong asymmetry of forward scattering effect from dielectric cubic nanoantenna in lossless media

Dielectric photonics platform provides unique possibilities to control light scattering via utilizing high-index dielectric nanoantennas with peculiar optical signatures. Despite the intensively growing field of all-dielectric nanophotonics, it is still unclear how surrounding media affect scattering properties of a nanoantenna with complex multipole response. Here we report on light scattering by a silicon cubic nanoparticles embedded in lossless media, supporting optical resonant response. We show that significant changes in the scattering process are governed by the electro-magnetic multipo…

基于多重分形散射介质的高通量散斑光谱仪

High-throughput speckle spectrometers based on multifractal scattering media

该研究提出基于绝缘体上硅平台多重分形散射介质的集成散斑光谱仪，经数值与实验验证，其在不影响散斑相关函数光谱衰减的前提下提升了光通量与信噪比，性能优于传统均匀随机散射光谱仪，为片上集成应用提供新方案。

Deterministic and controllable photonic scattering media via direct laser writing

Photonic scattering materials, such as biological tissue and white paper, are made of randomly positioned nanoscale inhomogeneities in refractive index that lead to multiple scattering of light. Typically these materials, both naturally-occurring or man-made, are formed through self assembly of the scattering inhomogeneities, which imposes challenges in tailoring the disorder and hence the optical properties. Here, We report on the nanofabrication of photonic scattering media using direct laser writing with deterministic design. These deterministic scattering media consist of submicron thick p…

Optimal control of light propagation through multiple-scattering media in the presence of noise

We study the control of coherent light propagation through multiple-scattering media in the presence of measurement noise. In our experiments, we use a two-step optimization procedure to find the optimal incident wavefront. We conclude that the degree of optimal control of coherent light propagation through a multiple-scattering medium is only determined by the number of photoelectrons detected per single speckle spot. The prediction of our model agrees well with the experimental results. Our results offer opportunities for imaging applications through scattering media such as biological tissu…

Invariance property in scattering media and absorption

In this paper we deal with the influence on absorption of the diffusive media characteristics framing the problem in connection with the invariance property (IP) of the mean path length. We show that the IP is an important issue that regulates but not prevent the search of absorption maximization by scattering characteristics. We find that the scattering may increase the absorption or even be detrimental, depending on the geometry of the medium and the conditions of its illumination.

散射介质中的拓扑光子学

Topological photonics with scattering media

本文证明散射介质可借助电磁波横向性质与毛球定理实现拓扑暗态，并利用低成本激光结构化金纳米结构散射介质进行实验验证，为拓扑纳米光子学和无标记生物传感提供新途径。

Blind focusing through strongly scattering media using wavefront shaping with nonlinear feedback

Scattering prevents light from being focused in turbid media. The effect of scattering can be negated through wavefront shaping techniques when a localized form of feedback is available. Even in the absence of such a localized reporter, wavefront shaping can blindly form a single diffraction-limited focus when the feedback response is nonlinear. We developed and experimentally validated a model that accurately describes the statistics of this blind focusing process. We show that maximizing the nonlinear feedback signal does not always result in the formation of a focus. Using our model, we can…

Scattering Integral Equations for Diffusive Waves. Detection of Objects Buried in Diffusive Media in the Presence of Interfaces

This paper has been withdrawn by the authors until some changes are made.

Simultaneously improving multiple imaging parameters with scattering media

Traditional optical imaging systems can provide high-quality imaging with complicated and expensive optical design by eliminating aberrations. With the help of optical memory effect (ME), not independently improving single imaging parameter, but simultaneously improving several imaging parameters by adding scattering media to the imaging systems was demonstrated firstly. As an example, in a simple single-lens imaging system, except the depth-of-field (DOF) was improved greatly, spherical aberration, coma aberration and chromatic aberration were eliminated simultaneously by placing a scattering…

Tracking and imaging of dynamic objects in scattering media by time-reversed adapted-perturbation (TRAP) optical focusing

The ability to steer light propagation inside scattering media has long been sought-after due to its potential widespread applications. To form optical foci inside scattering media, the only feasible strategy is to guide photons by using either implanted or virtual guide stars. However, all of these guide stars must be introduced extrinsically, either invasively or by physical contact, limiting the scope of their application. Here, we focus light inside scattering media by employing intrinsic dynamics as guide stars. By time-reversing the perturbed component of the scattered light adaptively, …

Light repolarization by scattering media

The polarization of a coherent depolarized incident light beam passing through a disordered medium is investigated. The local polarization of the scattered far field and the probability density function are calculated and show an excellent agreement with experiment. It is demonstrated that complex media may confer high degree of polarization (0.75 DOP average) to the incident unpolarized light.

Depolarizing power and polarization entropy of light scattering media: experiment and theory

We experimentally investigate the depolarizing power and the polarization entropy of a broad class of scattering optical media. By means of polarization tomography, these quantities are derived from an effective Mueller matrix, which is introduced through a formal description of the multi-mode detection scheme we use, as recently proposed by Aiello and Woerdman (arXiv:quant-ph/0407234). This proposal emphasized an intriguing universality in the polarization aspects of classical as well as quantum light scattering; in this contribution we demonstrate experimentally that this universality is obe…

Analytic evaluation of diffuse fluence error in multi-layer scattering media with discontinuous refractive index

A simple analytic method of estimating the error involved in using an approximate boundary condition for diffuse radiation in two adjoining scattering media with differing refractive index is presented. The method is based on asymptotic planar fluences and enables the relative error to be readily evaluated without recourse to Monte Carlo simulation. Three examples of its application are considered: (1) evaluating the error in calculating the diffuse fluences at a boundary between two media with differing refractive index and dissimilar scattering properties (2) the dependence of the relative e…

Manipulating the transmission matrix of scattering media for nonlinear imaging beyond the memory effect

The measurement of the Transmission Matrix (TM) of a scattering medium is of great interest for imaging. It can be acquired directly by interferometry using an internal reference wavefront. Unfortunately, internal reference fields are scattered by the medium which results in a speckle that makes the TM measurement heterogeneous across the output field of view. We demonstrate how to correct for this effect using the intrinsic properties of the TM. For thin scattering media, we exploit the memory effect of the medium and the reference speckle to create a corrected TM. For highly scattering media…

Recovering the spectral and spatial information of an object behind a scattering media

Light passing through scattering media will be strongly scattered and diffused into complex speckle pattern, which contains almost all the spatial information and spectral information of the objects. Although various methods have been proposed to recover the spatial information of the hidden objects, it is still a challenge to simultaneously obtain their spectral information. Here, we present an effective approach to realize spectral imaging through scattering media by combining the spectra retrieval and the speckle-correlation. Compared to the traditional imaging spectrometer, our approach is…

Increasing the imaging capabilities of multimode fibers by exploiting the properties of highly scattering media

We present a novel design that exploits the focusing properties of scattering media to increase the resolution and the working distance of multimode fiber based imaging devices. Placing a highly scattering medium in front of the distal tip of the multimode fiber enables the formation of smaller sized foci at increased working distances away from the fiber tip. We perform a parametric study of the effect of the working distance and the separation between the fiber and the scattering medium on the focus size. We experimentally demonstrate submicron focused spots as far away as 800μm with 532nm l…

Dynamics of Atom-Mediated Photon-Photon Scattering I: Theory

The mediated photon-photon interaction due to the resonant Kerr nonlinearity in an inhomogeneously broadened atomic vapor is considered. The time-scale for photon-photon scattering is computed and found to be determined by the inhomogeneous broadening and the magnitude of the momentum transfer. This time can be shorter than the atomic relaxation time. Effects of atom statistics are included and the special case of small-angle scattering is considered. In the latter case the time-scale of the nonlinear response remains fast, even though the linear response slows as the inverse of the momentum t…

Photon echoes in strongly scattering media: a diagrammatic approach

We study photon echo generation in disordered media with the help of multiple scattering theory based on diagrammatic approach and numerical simulations. We show that a strong correlation exists between the driving fields at the origin of the echo and the echo beam. Opening the way to a better understanding of non-linear wave propagation in complex materials, this work supports recent experimental results with applications to the measurement of the optical dipole lifetime $T_2$ in powders.

Scattering invariant modes of light in complex media

Random scattering of light in disordered media is an intriguing phenomenon of fundamental relevance to various applications. While techniques such as wavefront shaping and transmission matrix measurements have enabled remarkable progress for advanced imaging concepts, the most successful strategy to obtain clear images through a disordered medium remains the filtering of ballistic light. Ballistic photons with a scattering-free propagation are, however, exponentially rare and no method so far can increase their proportion. To address these limitations, we introduce and experimentally implement…

利用光学记忆效应进行散射介质成像：教程

Imaging through scattering media by exploiting the optical memory effect: a tutorial

本教程介绍如何利用光的多重散射相关性知识，实现通过强散射层的非侵入式成像，并重点讲解实验运行的实际细节。

Detection of the tagged or untagged photons in acousto-optic imaging of thick highly scattering media by photorefractive adaptive holography

We propose an original adaptive wavefront holographic setup based on the photorefractive effect (PR), to make real-time measurements of acousto-optic signals in thick scattering media, with a high flux collection at high rates for breast tumor detection. We describe here our present state of art and understanding on the problem of breast imaging with PR detection of the acousto-optic signal.

通过散射介质对非相干物体的三维全息成像

Three-dimensional holographic imaging of incoherent objects through scattering media

针对光散射影响显微成像的挑战，提出利用虚拟介质复制散射效应并通过数值传播非相干场进行补偿的方法，实现了对隐藏物体的精确三维重建。

色散介质之间时空界面的散射

Scattering at Space-Time Interfaces between Dispersive Media

本文提出色散介质间移动界面的广义频率跃迁理论，揭示色散重塑时空散射景观，导出非线性频率关系及闭式散射系数。

散射介质内部层析光学成像的全波模拟

Full-wave simulations of tomographic optical imaging inside scattering media

针对散射介质内部成像缺乏真实结构难以评估的问题，本文提出全波模拟方法，提供真实结构并便于比较多种成像方案，可识别伪影并建立统一标准。

Transmission matrix approaches for non-linear fluorescence excitation through multiple scattering media

Several matrix approaches were developed to control light propagation through multiple scattering media under illumination of ultrashort pulses of light. These matrices can be recorded either with spectral or temporal resolution. Thanks to wavefront shaping, temporal and spatial refocusing have been demonstrated. In this work, we study how these different methods can be exploited to enhance a two-photon excitation fluorescence process. We first compare the different techniques on micrometer-size isolated fluorescent beads. We then demonstrate point-scanning imaging of such fluorescent microbea…

A realistic phase screen model for forward multiple-scattering media

Existing random phase screen (RPS) models for forward multiple-scattering media fail to incorporate ballistic light. In this letter, we redesign the angular spectrum of the screen by means of Monte-Carlo simulation based on an assumption that a single screen should represent all the scattering events a photon experiences between two adjacent screens. Three examples demonstrate that the proposed model exhibits more realistic optical properties than conventional RPS models in terms of attenuation of ballistic light, evolution of beam profile and angular memory effect. The proposed model also pro…

三维多重散射介质中的镜对称性

Mirror Symmetry in three-dimensional Multiple-Scattering Media

研究了平面波沿对称平面照射时三维多重散射介质中镜对称平面的影响，通过样品与三维建模定量比较，观察到偏振相关的强度偏差，推导了解析表达式，其应用可用于防伪。

Energy-leaky modes in partially measured scattering matrices of disordered media

We investigate energy-leaky modes induced by incomplete measurements of the scattering matrices of complex media. Due to the limited numerical apertures of an optical system, it is experimentally challenging to access theoretically predicted perfect transmission channels in the diffusive regime. By conducting numerical simulations on scattering matrices, we demonstrate that leaky modes contributed from uncollected transmission in the TM provides an energy transmission that is more enhanced than that predicted by measurement. On the other hand, a leaky mode originating from the uncollected refl…

On the optical theorem and optimal extinction, scattering and absorption in lossy media

This paper reformulates and extends some recent analytical results concerning a new optical theorem and the associated physical bounds on absorption in lossy media. The analysis is valid for any linear scatterer (such as an antenna), consisting of arbitrary materials (bianisotropic, etc.) and arbitrary geometries, as long as the scatterer is circumscribed by a spherical volume embedded in a lossy background medium. The corresponding formulas are here reformulated and extended to encompass magnetic as well as dielectric background media. Explicit derivations, formulas and discussions are also g…

Focusing and Compression of Ultrashort Pulses through Scattering Media

Light scattering in inhomogeneous media induces wavefront distortions which pose an inherent limitation in many optical applications. Examples range from microscopy and nanosurgery to astronomy. In recent years, ongoing efforts have made the correction of spatial distortions possible by wavefront shaping techniques. However, when ultrashort pulses are employed scattering induces temporal distortions which hinder their use in nonlinear processes such as in multiphoton microscopy and quantum control experiments. Here we show that correction of both spatial and temporal distortions can be attaine…

Focusing polychromatic light through strongly scattering media

We demonstrate feedback-optimized focusing of spatially coherent polychromatic light after transmission through strongly scattering media, and describe the relationship between optimized focus intensity and initial far-field speckle contrast. Optimization is performed using a MEMS spatial light modulator with camera-based or spectrometer-based feedback. We observe that the spectral bandwidth of the optimized focus depends on characteristics of the feedback signal. We interpret this dependence as a modification in the number of spectral modes transmitted by the sample, and introduce a simple mo…

动态散射介质中的强度相关合成波长成像

Intensity-Correlation Synthetic Wavelength Imaging in Dynamic Scattering Media

针对动态散射介质成像因散斑退相关导致常规方法失效的挑战，提出基于二阶相关和合成波长全息的成像方法，利用短曝光强度图像在无相位稳定性要求下实现高分辨率重建，对复杂环境生物医学成像具有重要意义。

Real-time full-field imaging through scattering media by all-optical feedback

Full-field imaging through scattering media is fraught with many challenges. Despite many achievements in recent years, current imaging methods are too slow to deal with fast dynamics that occur for example in biomedical imaging. Here we present an ultra-fast all-optical method, where the object to be imaged and the scattering medium (diffuser) are inserted into a highly multimode self-imaging laser cavity. We show that the intra-cavity laser light from the object is mainly focused onto specific regions of the scattering medium where the phase variations are low. Thus, round trip loss within t…

Exploring the origin of stronger survival of polarized vortex beams through scattering media

Laguerre-Gaussian (LG) beams carrying orbital angular momentum (OAM) have shown promise in deep tissue imaging, medical diagnostics, and optical communication due to their robust propagation properties through scattering media. However, an exact model that provides a mechanism for the enhanced scattering properties of LG beams over Gaussian beams has not been established till date. Here, we examine this issue by studying the propagation of polarized vortex beams transmitted through tissue-like turbid scattering media. We demonstrate that the intensity profile has a much more profound effect on…

A model for full-field optical coherence tomography in scattering media

We develop a model of full-field optical coherence tomography (FF-OCT) that includes a description of partial temporal and spatial coherence, together with a mean-field scattering theory going beyond the Born approximation. Based on explicit expressions of the FF-OCT signal, we discuss essential features of FF-OCT imaging, such as the influence of partial coherence on the optical transfer function, and on the decay of the signal with depth that is captured by the model. We derive the conditions under which the spatially averaged signal exhibits a pure exponential decay with depth, providing a …

Enhanced stability of the focus obtained by wavefront optimization in dynamical scattering media

Focusing scattered light using wavefront shaping provides interesting perspectives to image deep in opaque samples, as e.g. in nonlinear fluorescence microscopy. Applying these technics to in vivo imaging remains challenging due to the short decorrelation time of the speckle in depth, as focusing and imaging has to be achieved within the order of the decorrelation time. In this paper, we experimentally study the focus lifetime after focusing through dynamical scattering media, when iterative wavefront optimization and speckle decorrelation occur over the same timescale. We show experimental si…

Looking through walls and around corners with incoherent light: Wide-field real-time imaging through scattering media

Imaging with optical resolution through highly scattering media is a long sought-after goal with important applications in deep tissue imaging. Although being the focus of numerous works, this goal was considered impractical until recently. Adaptive-optics techniques which are effective in correcting weak wavefront aberrations, were deemed inadequate for turbid samples, where complex speckle patterns arise and light is scattered to a large number of modes that greatly exceeds the number of degrees of control. This conception changed after the demonstration of focusing coherent light through tu…

Light scattering in pseudo-passive media with uniformly balanced gain and loss

We introduce a class of metamaterials with uniformly balanced gain and loss associated with complex permittivity and permeability constants. The refractive index of such a balanced pseudo-passive metamaterial is real. An unbounded uniform pseudo-passive medium has transport characteristics similar to those of its truly passive and lossless counterpart with the same real refractive index. However, bounded pseudo-passive samples show some unexpected scattering features which can be further emphasized by including such elements in a photonic structure.

通过波前整形在多重散射介质中创建高对比度图案

Creating high-contrast patterns in multiple-scattering media via wavefront shaping

针对波前整形中长程关联降低目标对比度的问题，通过引入对比度算符与差分算符并利用其本征态操控非局域强度关联，在强散射介质中实现了高对比度图案创建与目标能量递送。

时间周期光子介质中用于波前整形的伪幺正Floquet散射矩阵

Pseudounitary Floquet scattering matrix for wave-front shaping in time-periodic photonic media

本文提出用满足伪幺正关系的静态Floquet散射矩阵描述有限时间周期介质的散射特性，并将Wigner-Smith波前整形方法推广到Floquet系统，实现时空最优光脉冲用于时变介质的光学微操控。

无损耗 Drude 介质中不可移除异常点的时间散射

Temporal Scattering at Irremovable Exceptional Points in Lossless Drude Media

本文研究了无损耗Drude介质中的时间散射，发现与静态极化电荷相关的零频率平带形成异常线，在光子时间界面激发非传播静态场，导致振幅随时间线性增加的静态模式等独特特征，且不违反总能量守恒，呈现了与无色散和Lorentz色散介质截然不同的新物理图景。

Deterministic light focusing in space and time through multiple scattering media with a Time-Resolved Transmission Matrix approach

We report a method to characterize the propagation of an ultrashort pulse of light through a multiple scattering medium by measuring its time-resolved transmission matrix. This method is based on the use of a spatial light modulator together with a coherent time-gated detection of the transmitted speckle field. Using this matrix, we demonstrate the focusing of the scattered pulse at any arbitrary position in space and time after the medium. Our approach opens new perspectives for both fundamental studies and applications in imaging and coherent control in disordered media.

Stimulated Brillouin Scattering in layered media: nanoscale enhancement of silicon

We report a theoretical study of Stimulated Brillouin Scattering (SBS) in general anisotropic media, incorporating the effects of both acoustic strain and local rotation in all calculations. We apply our general theoretical framework to compute the SBS gain for layered media with periodic length scales smaller than all optical and acoustic wavelengths, where such composites behave like homogeneous anisotropic media. We theoretically predict that a layered medium comprising nanometre-thin layers of silicon and As$_2$S$_3$ glass possesses a bulk SBS gain of $1.28 \times 10^{-9} \, \mathrm{W}^{-1…

散射介质中光通过多重超声波的频率移动

Frequency shifting of light via multiple ultrasound waves in scattering media

本文推导并验证了散射介质中光与超声相互作用产生频率移动的分析模型，该模型支持高超声压力及多频率分量，并提供了优化超声特性以提升光频移效率的见解，助力超声光学断层扫描等光子诊断技术。

Hidden Black: Coherent Enhancement of Absorption in Strongly-scattering Media

We show that a weakly absorbing, strongly scattering (white) medium can be made very strongly absorbing at any frequency within its strong-scattering bandwidth by optimizing the input electromagnetic field. For uniform absorption, results from random matrix theory imply that the reflectivity of the medium can be suppressed by a factor ~(l_a/lN^2), where N is the number of incident channels and l,l_a are the elastic and absorption mean free paths respectively. It is thus possible to increase absorption from a few percent to > 99%. For a localized weak absorber buried in a non-absorbing scatteri…

Control of light transmission through opaque scattering media in space and time

We report the first experimental demonstration of combined spatial and temporal control of light trajectories through opaque media. This control is achieved by solely manipulating spatial degrees of freedom of the incident wavefront. As an application, we demonstrate that the present approach is capable to form bandwidth-limited ultrashort pulses from the otherwise randomly transmitted light with a controllable interaction time of the pulses with the medium. Our approach provides a new tool for fundamental studies of light propagation in complex media and has potential for applications for coh…

Electromagnetic Scattering by Bianisotropic Spheres

Electromagnetic fields in bulk bianisotropic media can be represented using plane waves whose k-vectors can be found using the index of refraction operator method and belong to the Fresnel wave surfaces that fall into one of the 5 hyperbolic classes that are used as the taxonomy of bianisotropic media [Durach et al., Appl. Sci., Opt. Comm. (2020), PIER (2022)]. It has been demonstrated that, alternatively, the linear combinations of vector spherical harmonics can be used as a set of solutions of vector Helmholtz equation in gyroelectric, gyromagnetic, and gyrotropic anisotropic media to develo…

Effect of Dependent Scattering on Light Absorption in Highly Scattering Random Media

The approximate nature of radiative transfer equation (RTE) leads to a bunch of considerations on the effect of "dependent scattering" in random media, especially particulate media composed of discrete scatterers, in the last a few decades, which usually indicates those deviations RTE (combined with ISA) lead to from experimental and exact numerical results due to electromagnetic wave interference. Here we theoretically and numerically demonstrate the effect of dependent scattering on absorption in disordered media consisting of highly scattering scatterers. By making comparison between the in…

Ghost imaging in scattering media

Ghost imaging with thermal light in scattering media is investigated. We demonstrated both theoretically and experimentally for the first time that the image with high quality can still be obtained in the scattering media by ghost imaging. The scattering effect on the qualities of the images obtained when the object is illuminated directly by the thermal light and ghost imaging is analyzed theoretically. Its potential applications are also discussed.

Numerical study of the degree of light scattering strength versus fractal dimension in optical fractal disordered media: Applications in strong to weak disordered media

Optical scattering strength of fractal optical disordered media with varying fractal dimension is reported. The diffusion limited aggregation (DLA) technique is used to generate fractal samples in 2D and 3D, and fractal dimensions are calculated using the box-counting method. The degree of structural disorder of these samples are calculated using their light localization strength, using the inverse participation ratio (IPR) analyses of the optical eigenfunctions. Results show non-monotonous behavior of the disorder-induced scattering strength with the fractal dimension, attributed to the compe…

Imaging through scattering media via spatial-temporal encoded pattern illumination

Optical imaging through scattering media is a long-standing challenge. Although many approaches have been developed to focus light or image objects through scattering media, they are either invasive, restricted to stationary or slowly-moving media, or require high-resolution cameras and complex algorithms to retrieve the images. Here we introduce a computational imaging technique that can overcome these restrictions by exploiting spatial-temporal encoded patterns (STEP). We present non-invasive imaging through scattering media with a single-pixel photodetector. We show that the method is insen…

二维随机半无限强散射介质中电磁波反射的数值模拟

Numerical simulation of the electromagnetic wave reflection from 2D random semi-infinite strongly scattering media

本文通过结合傅里叶模态法与超胞方法，数值模拟二维随机半无限强散射介质中的电磁波反射，验证了两种方法在求解复杂介质麦克斯韦方程组系综平均解时的收敛性与一致性。

Circular polarization memory in polydisperse scattering media

We investigate the survival of circularly polarized light in random scattering media. The surprising persistence of this form of polarization has a known dependence on the size and refractive index of scattering particles, however a general description regarding polydisperse media is lacking. Through analysis of Mie theory, we present a means of calculating the magnitude of circular polarization memory in complex media, with total generality in the distribution of particle sizes and refractive indices. Quantification of this memory effect enables an alternate pathway towards recovering particl…