Brillouin scattering in condensed matter

Dil, Jan G.

doi:10.1088/0034-4885/45/3/002

Cited by 155 publications

(77 citation statements)

References 142 publications

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“…4. To distinguish these fluctuations from traveling waves on the mirror surface, previously measured in light scattering at non-specular directions [9,10], the spectra were measured using differences in the light power fluctuations at two close locations, separated by 77 µm. Surface waves with longer wavelengths will be correlated and eliminated in this differential measurement.…”

Section: Experimental Results and Analysismentioning

confidence: 99%

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Observation of reflectance fluctuations in metals

Mitsui¹,

Aoki²

2017

Phys. Rev. A

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Through the study of the power spectra of a monochromatic light beam reflected by metallic mirrors, fluctuations in their reflectance is observed. The power spectra were obtained down to a factor 10 −6 below the Standard Quantum Limit, with a dynamic range of 10 5 in the frequency and power, using methods we developed. The properties of the spectra are investigated and their dependence on the material is analyzed. The physics underlying the phenomenon is also discussed. These fluctuations provide a new window into the degrees of freedom responsible for the reflection process in metals.

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Section: Experimental Results and Analysismentioning

confidence: 99%

“…Second, it needs to be established that the observed signal is not caused by the light causing changes to the mirror itself, such as damaging its surface. Third, the cause of the observed phenomenon needs to be distinguished from other possible sources of fluctuation, such as surface waves of the material [9,10].…”

Section: Figmentioning

confidence: 99%

Observation of reflectance fluctuations in metals

Mitsui¹,

Aoki²

2017

Phys. Rev. A

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“…The Brillouin frequency shift ν B for an isotropic material can be expressed as 2 where is the acoustic velocity, E the elastic modulus (Young's modulus for solids and bulk modulus for liquids), ρ the density, n the refractive index, λ the optical wavelength and θ the scattering angle (Fig. 1a).…”

Section: Methods Brillouin Signal and Viscoelastic Modulusmentioning

confidence: 99%

Confocal Brillouin microscopy for three-dimensional mechanical imaging

2007

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Acoustically induced inelastic light scattering, first reported in 1922 by Brillouin 1 , allows noncontact, direct readout of the viscoelastic properties of a material and has widely been investigated for material characterization 2 , structural monitoring 3 and environmental sensing 4 . Extending the Brillouin technique from point sampling spectroscopy to imaging modality 5 would open up new possibilities for mechanical imaging, but has been challenging because rapid spectrum acquisition is required. Here, we demonstrate a confocal Brillouin microscope based on a fully parallel spectrometer-a virtually imaged phased array-that improves the detection efficiency by nearly 100-fold over previous approaches. Using the system, we show the first cross-sectional Brillouin imaging based on elastic properties as the contrast mechanism and monitor fast dynamic changes in elastic modulus during polymer crosslinking. Furthermore, we report the first in situ biomechanical measurement of the crystalline lens in a mouse eye. These results suggest multiple applications of Brillouin microscopy in biomedical and biomaterial science.The mechanical properties of biological tissues and biomaterials are closely related to their functional abilities 6 , and thus play significant roles in many areas of medicine. For example, coronary arteries hardened by calcification can cause heart problems, mechanically weakened bones resulting from osteoporosis represent a serious orthopaedic concern, and the stiffness of the extra-cellular matrix influences drug delivery and cell motility 7 . As such, the ability to measure mechanical properties non-invasively in vivo at the microscopic (cellular) scale would have a wide range of biomedical applications, as well as uses in material science and engineering 8,9 .Conventional mechanical tests, such as dynamic mechanical analysis and rheometry, require mechanical forces to be applied to samples through contact and, although accurate and comprehensive, they are therefore not well suited to in situ high-resolution measurements. Miniaturized mechanical methods have become increasingly sophisticated 10 , but they are still limited to surface measurement. Elastography is a promising technique used to extract mechanical information from structural deformation images 11 ; however, sensitivity to the assumed stress distribution and physiological motion limit spatial resolution and measurement precision. Acoustic techniques, such as ultrasound and acoustic microscopy, are non-invasive and can offer microscopic resolution. However, these techniques tend to be effective only for Spontaneous Brillouin scattering is an inelastic scattering process arising from inherent density fluctuations, or acoustic phonons, in the medium (Fig. 1a). Brillouin spectroscopy measures spectral changes upon scattering, providing direct information on the phonon's properties that are closely related to the viscoelastic properties of the medium (see Methods). Previously, Brillouin spectroscopy has been used successfully to me...

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“…The frequency of this oscillation depends on the angle between the propagation directions of the probe light and that of the coherent acoustic waves. It is precisely equal to the shift * omatsuda@eng.hokudai.ac.jp † Vitali.Goussev@univ-lemans.fr in frequency of the scattered light that would be caused by thermal phonons propagating in the same direction as the CAP and could be resolved using optical spectrometers in classic frequency-domain BS (FDBS) experiments [14][15][16][17]. That is why PAI is also often called time-domain Brillouin scattering (TDBS).…”

Section: Introductionmentioning

confidence: 99%

Time-domain Brillouin scattering assisted by diffraction gratings

et al. 2018

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Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.

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Brillouin scattering in condensed matter

Cited by 155 publications

References 142 publications

Observation of reflectance fluctuations in metals

Observation of reflectance fluctuations in metals

Confocal Brillouin microscopy for three-dimensional mechanical imaging

Time-domain Brillouin scattering assisted by diffraction gratings

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