Blink speckle spectroscopy of scattering media

Zimnyakov, Dmitry A.; Vilensky, Maxim A.

doi:10.1364/ol.31.000429

Cited by 9 publications

(3 citation statements)

References 6 publications

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“…Therefore, several research studies have been concerned with the statistical properties of the speckle patterns [1][2][3][4][5][6]. The speckle contrast of monochromatic and quasi-monochromatic light has been studied by [7][8][9][10][11][12][13][14][15][16]. The effect of the spectral light broadening on the visibility of the interference fringes obtained in the transmission from a surface of regular roughness, in the form of cross-grating, has been presented by [17,18].…”

Section: Introductionmentioning

confidence: 99%

New analytical expression for speckle contrast of spectral light broadening

El‐Nicklawy¹,

Abd-Rabou²,

Elmahdy³

2017

J. Opt.

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A new analytical expression for the average speckle contrast is derived for surfaces of random roughness at reflection. Rayleigh and Simpson phase probability density distributions of non-zero phase mean value are assumed for the roughness of the surface. The behavior of a speckle contrast with a roughness root mean square of phase deviation is presented. The effect of the spectral light profile, its spectral width, the density of the scatterers of the rough surface and the average time delay between the interfering beams are taken into consideration.

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Section: Introductionmentioning

confidence: 99%

New analytical expression for speckle contrast of spectral light broadening

El‐Nicklawy¹,

Abd-Rabou²,

Elmahdy³

2017

J. Opt.

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“…In Ref. [27] it was shown that when probing multiply scattering randomly inhomogeneous media with partially coherent light and recording the scattered radiation with a detector whose response time is considerably longer than the coherence time of the probing radiation, a criterion for significant impact of coherence on the statistical properties of the scattered light spatiotemporal fluctuations is the ratio | s| /l c . Here | s| is the mean absolute value of the difference of propagation path lengths of the scattered field partial components in the probed medium, l c is the coherence length of the probing radiation.…”

Section: Speckle Correlation Monitoring Of Scf Synthesized Polylactid...mentioning

confidence: 99%

Optical diffusion diagnostics of evolving polymer foams

Alonova M.V.,

Volchkov S.S.,

Zimnyakov D.A.

et al. 2023

Technical Physics

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Various approaches to the optical diagnostics of evolving polymer foams formed as a result of a decrease in the external pressure according to a given scenario in the "polymer-supercritical fluid" systems are considered.Formed polymer foams are considered as a material platform for the creation of scaffolds for biomedical applications. Diagnostics of the current state of the foam was carried out by statistical analysis of the spatiotemporal fluctuations of the probe laser radiation,multiple scattered in the volume of the evolving foam, or by analyzing the fluorescent response during foaming of the "polymer-fluorophore" mixture, pumped by laser radiation in the absorption band of the fluorophore. A relationship has been established between the average lifetime of dynamic speckles in scattered laser light and a generalized parameter characterizing the foam expansion dynamics. It was also found that the waveguide effect in the walls of the formed pores has a significant influence on the fluorescent response of the evolving foam, leading to an increase in the characteristic dwell time of fluorescence radiation in the walls and, accordingly, to an increase in the contribution of the induced component to the fluorescent response. Keywords: fluorescent response, speckle correlometry, polylactide, foaming, supercritical carbon dioxide.

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“…Another way to obtain a controllable speckle blur in the course of the scattering media probing with a tunable laser light is application of the binary modulation of laser light frequency together with a long-exposure recording of time-varying speckles. In particular, this approach can be realized using a semiconductor laser with a diffraction grating as an external tunable element of the laser cavity; the binary modulation of the light frequency is achieved due to repeatable sequences of the mode hops under a condition of periodic changes in the grating tilt with respect to the beam axis [27].…”

Section: Introductionmentioning

confidence: 99%

Band-Limited Reference-Free Speckle Spectroscopy: Probing the Fluorescent Media in the Vicinity of the Noise-Defined Threshold

et al. 2020

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A method of reference-free speckle spectroscopy based on the statistical analysis of intensity spatial fluctuations of the spectrally-selected multiple-scattered fluorescence radiation is examined in the case of the finite-band spectral selection of fluorescence light emitted by the laser-pumped random medium, and detection conditions far from the ideal case. Intensity fluctuations are recorded during point-to-point scanning of the surface of a random multiple-scattering medium, which is characterized by the dependences of the second- and third-order statistical moments of intensity on the wavelength of detected spectrally selected light. In turn, the statistical moments of intensity fluctuations are determined by the average propagation path of fluorescent radiation in the medium. This makes it possible to analyze the features of the light-medium interactions at a scale of the order of the transport mean free path of radiation propagation in the medium. Depending on the spectral selection conditions, the method is applicable for characterizing micro- or nano-structured fluorescent layers with thicknesses from tens of micrometers to several millimeters. In the examined case, the finite-band spectral selection results in the values of coherence length of the detected fluorescence radiation compared with the ensemble-averaged absolute value of the path-length difference between the stochastically interfering and spectrally selected partial contributions to the fluorescence field. In addition, non-ideal detection conditions (usage of a multimode optical fiber in the light-collecting unit) cause additional strong damping of the detected speckle intensity fluctuations. These factors lead to a remarkable suppression of spatial fluctuations of the fluorescence intensity in the course of spatially- and spectrally-resolved surface scanning of the laser-pumped probed random medium. Nevertheless, with appropriate procedures of the intrinsic noise reduction and data correction, the obtained spectral dependencies of the normalized third-order statistical moment of the band-limited fluorescence intensity clearly indicate the fluorescence propagation features in the probed multiple-scattering random media (such as a strong influence of the scattering strength and multiple self-absorption–re-emission events on the average propagation path of light in the medium).The possibilities of noise reduction and data correction in the case of applying the band-limited reference-free spectroscopic instrumentation with low spectral and spatial resolution are illustrated by the experimental results obtained using the Rhodamine-6G-doped and continuous wave (CW)-laser-pumped layers of the densely packed titania and silica particles.

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Blink speckle spectroscopy of scattering media

Cited by 9 publications

References 6 publications

New analytical expression for speckle contrast of spectral light broadening

New analytical expression for speckle contrast of spectral light broadening

Optical diffusion diagnostics of evolving polymer foams

Band-Limited Reference-Free Speckle Spectroscopy: Probing the Fluorescent Media in the Vicinity of the Noise-Defined Threshold

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