Direct determination of diffusion properties of random media from speckle contrast

Curry, Nathan; Bondareff, Pierre; Leclercq, Mathieu; Hulst, N.F. van; Sapienza, Riccardo; Gigan, Sylvain; Grésillon, S.

doi:10.1364/ol.36.003332

Cited by 44 publications

(45 citation statements)

References 30 publications

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“…Temporally, photons exit a scattering medium at different times, giving rise to a broadened pulse at its output [7,19]. Temporal spreading of the original pulse is characterized by a confinement time τ m [20] related to the Thouless time [21]. Equivalently, from a spectral point of view, the scattering medium responds differently for distinct spectral components of an ultrashort pulse, with a spectral correlation bandwidth ∆ω m ∝ 1/τ m , giving rise to a very complex spatio-temporal speckle pattern [22][23][24][25].…”

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Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix

et al. 2016

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We report broadband characterization of the propagation of light through a multiply scattering medium by means of its Multi-Spectral Transmission Matrix. Using a single spatial light modulator, our approach enables the full control of both spatial and spectral properties of an ultrashort pulse transmitted through the medium. We demonstrate spatiotemporal focusing of the pulse at any arbitrary position and time with any desired spectral shape. Our approach opens new perspectives for fundamental studies of light-matter interaction in disordered media, and has potential applications in sensing, coherent control and imaging.Propagation of coherent light through a scattering medium produces a speckle pattern at the output [1], due to light scrambling by multiple scattering events [2]. The phase and amplitude information of the light are spatially mixed, thus limiting resolution, depth and contrast of most optical imaging techniques. Ultrashort pulses, generated by broadband modelocked lasers, are very useful for multiphotonic imaging and non-linear physics [3][4][5]. In the temporal domain, an ultrashort pulse is temporally broadened during propagation in a scattering medium, due to the long dwell time within it [6,7], which therefore limits its range of applications.However, this scattering process is linear and deterministic. Therefore, one can control the input wavefront to design the output field. In this respect, spatial light modulators (SLMs) offer more than a million degrees of freedom to control the propagation of coherent light. These systems have played an important role in the development of wavefront shaping techniques to manipulate light in complex media. Iterative optimization algorithm [8][9][10] and phase conjugation methods [11,12] have been proposed to focus light at a given output position, an essential ingredient for imaging. An alternative method for light control is the optical transmission matrix (TM). The TM is a linear operator that links the input field (SLM) to the output field (CCD camera) [1,13]. The measurement of the TM allows imaging through [15] or inside a scattering medium [16], and potentially access mesoscopic properties of the system [17].The possibility of shaping the pulse in time is also essential for coherent control [18]. Temporally, photons exit a scattering medium at different times, giving rise to a broadened pulse at its output [7,19]. Temporal spreading of the original pulse is characterized by a confinement time τ m [20] related to the Thouless time [21]. Equivalently, from a spectral point of view, the scattering medium responds differently for distinct spectral components of an ultrashort pulse, with a spectral correlation bandwidth ∆ω m ∝ 1/τ m , giving rise to a very complex spatio-temporal speckle pattern [22][23][24][25]. With a single SLM, one can manipulate spatial degrees of freedom to adjust the delay between different optical paths. Therefore spatial and temporal distortions can be both compensated using wavefront shaping techniques. This approach allows th...

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Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix

et al. 2016

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“…The speckle spectral correlation of the medium is characterized by its spectral bandwidth δλ m . Therefore, the number of independent spectral channels for the pulse, or number of spectral degrees of freedom, is defined as N λ = ∆λ/δλ m 1/C 2 0 [5,17]. In the temporal domain, correspondingly, a speckle grain is characterized by a temporally lengthened structure, with a temporal correlation δt, related to the bandwidth of the source [9,18].…”

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“…Transmitted light results in a speckle intensity pattern with low contrast C 0 < 1. This low contrast results from the incoherent summation of various uncorrelated speckles corresponding to different spectral components of the input pulse [17]. The speckle spectral correlation of the medium is characterized by its spectral bandwidth δλ m .…”

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Temporal recompression through a scattering medium via a broadband transmission matrix

Mounaix¹,

Aguiar²,

Gigan³

2017

Optica

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The transmission matrix is a unique tool to control light through a scattering medium. A monochromatic transmission matrix does not allow temporal control of broadband light. Conversely, measuring multiple transmission matrices with spectral resolution allows fine temporal control when a pulse is temporally broadened upon multiple scattering, but requires very long measurement time. Here, we show that a single linear operator, measured for a broadband pulse with a co-propagating reference, naturally allows for spatial focusing, and interestingly generates a two-fold temporal recompression at the focus, compared with the natural temporal broadening. This is particularly relevant for non-linear imaging techniques in biological tissues.When monochromatic coherent light propagates in a medium with high refractive index inhomogeneities, it quickly develops into a speckle. Despite the complex structure of speckle patterns, each speckle grain has a deterministic relation to the input fields [1]. Over the last decade, wavefront shaping has turned to be an efficient tool to control monochromatic light through highly scattering systems [2], notably by exploiting the transmission matrix [3].Under illumination with a source of large bandwidth, each spectral component can generate a different speckle pattern [4]. Therefore one needs to adjust these additional spectral/temporal degrees of freedom to temporally control the output pulse [5]. This can be achieved using methods such as nonlinear optical processes [6,7], time-gating [8,9], and frequency-resolved measurements [10,11]. However, these methods underly either low signal-to-noise measurements (non-linear processes), or stability issues as they require lengthy acquisition procedures [12] and the need of external reference.An alternative approach is to use self-referencing signals, at the expense of lacking control on spectral degrees of freedom. Recently, "broadband wavefront shaping" experiments reported outcomes disparate from what is expected from monochromatic wavefront shaping, such as a decrease in the independent spectral degrees of freedom [13,14], and recovery of pure polarization states [15]. Notably, these results could have an impact on biomedical imaging [16]. Nonetheless, the exact temporal properties of the obtained output pulse via broadband wavefront shaping remain elusive. In this letter, we report the first characterization of the so-called broadband transmission matrix of a scattering medium. We exploit it for focusing purposes, and we analyze and interpret its temporal behavior. Unexpectedly, the characterized average pulse length is shorter than the pulse propagating without shaping. Figure 1a illustrates and summarizes propagation of broadband light (ultrashort pulse of duration δt, spectral width ∆λ) through an optically thick scattering medium. Transmitted light results in a speckle intensity pattern with low contrast C 0 < 1. This low contrast results from the incoherent summation of various uncorrelated speckles corresponding to different spect...

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“…A 3nm band around 810nm is selected using a narrowband filter. Since the dwell time in the medium is short for reflection, the speckle contrast of the reflected light is close to unity [24], thus ensuring that light propagation can be considered as quasi-monochromatic. This is in contrast with a transmission experiment where narrower medium bandwidth and pulse broadening can be observed [25].…”

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Nonclassical light manipulation in a multiple-scattering medium

et al. 2014

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We demonstrate the control of entanglement of a single photon between several spatial modes propagating through a strongly scattering medium. Measurement of the scattering matrix allows the wavefront of the photon to be shaped to compensate the distortions induced by multiple scattering events. The photon can thus be directed coherently to a single or multi-mode output. Using this approach we show how entanglement across different modes can be manipulated despite the enormous wavefront disturbance caused by the scattering medium. PACS numbers:Random walks describe the evolution of a system on a discrete graph where the direction of each new step is decided by tossing a coin. This simple idea describes several important physical phenomena, from localization of electrons in solids to reptation of proteins in liquids. Further, it has diverse applications in computer science and network analysis. Quantum random walks (QRW) refer to coherent superpositions of different trajectories of a quantum system. QRW have deep implications for quantum computing [1][2][3], including the possibility of universal computing [4,5].Photonics has proven a versatile architecture for the implementation of quantum walks. Further, the wavelike character is easily accessible in ambient conditions, and the high degree of coherence and lack of interaction between photons in a linear optical system enable complex graphs to be implemented in the laboratory [6][7][8]. Demonstrations range from multiparticle [9], and multidimensional walks [11], to analogues of Anderson localisation in condensed matter systems [12,13], to the implementation of the boson sampling problem [14][15][16][17]. Waveguide structures such as those employed in the aforementioned implementations have accessed up to 20 modes [18].Disordered multiply scattering media, such as a thick layer of densily packed dielectric particles, that scatters light in a complex manner, are highly multimode converters for light. They have been investigated in the context of quantum optics and quantum information, both theoretically [26,27,32] and experimentally [28,30,31]. Thanks to the linearity of the elastic scattering processes, coherence is maintained during multiple scattering but the modes become highly complex, creating a so-called speckle pattern. Recently, wavefront shaping has appeared as a powerful technique to control light propagation through such media [33,34], including the ability to guide light, focus and image. Through direct characterization of the scattering matrix (SM) of a material, one can link input to output modes of the scattering medium [22].In this work, we explore the possibility for using such multiple-scattering media for quantum information processing, allowing access to a highly multimode system, well beyond what is possible using waveguides. A crucial point is to demonstrate the control of the quantum light travelling through and out of the medium. Recently, an iterative optimization algorithm was used to control the wavefront of a single photon and deliver ...

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Direct determination of diffusion properties of random media from speckle contrast

Cited by 44 publications

References 30 publications

Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix

Spatiotemporal Coherent Control of Light through a Multiple Scattering Medium with the Multispectral Transmission Matrix

Temporal recompression through a scattering medium via a broadband transmission matrix

Nonclassical light manipulation in a multiple-scattering medium

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