Experimental determination of the effective refractive index in strongly scattering media

Rivas, Jaime Gómez; Dau, D.; Imhof, Arnout; Sprik, R.; Bret, Boris P. J.; Johnson, Patrick; Hijmans, T.W.; Lagendijk, Ad

doi:10.1016/s0030-4018(03)01348-8

Cited by 26 publications

(8 citation statements)

References 9 publications

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“…The transport velocity in the lowfrequency range of Fig. 4(c) lies close to the phase velocity v ph /c 0 = (0.69 ± 0.07) estimated using the effective refractive index of porous GaP [18]. The quantitative agreement between v E and v ph indicates that internal resonances do not play a role in the macroporous GaP network, in contrast to for example TiO 2 materials in which a strong reduction v E has been reported [13].…”

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confidence: 73%

Method for broadband spectroscopy of light transport through opaque scattering media

Muskens

Lagendijk

2009

Opt. Lett.

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We present a new broadband technique for the measurement of diffuse light transport through opaque scattering media. Using the spectral correlations introduced by a scattering medium onto a white-light supercontinuum spectrum, the diffusion constant of light is determined over a wide spectral range in the visible and near infrared. Independent broadband measurements of both the transport mean free path and the diffusion constant are used to calculate the spectral dependence of the energy velocity in a porous GaP slab. Broadband correlation spectroscopy is found to be an excellent tool for the characterization of random scattering media.Quantitative information on light transport in disordered media is of importance in many medical, chemical, and physical applications [1,2]. Scattering plays a crucial role in the performance of novel nanophotonic structures such as photonic crystals, waveguides, and metamaterials [3][4][5]. Access to the spectral variation of light scattering properties is indispensable when studying different scattering regimes, effects of resonances or band structure [6], or eventually the transition to Anderson localization [7]. Until recently, many light transport experiments were limited by the use of single-wavelength or narrowband tunable lasers, hampering the interpretation of results. Recent developments in spatially coherent, broadband light sources allow for new experiments yielding unprecedented access to interference phenomena in random media [8].Static light transport is characterized by a mean free path , which can be obtained from total transmission and enhanced backscattering experiments. Dynamic measurements, like time-resolved transmission of short optical pulses, give access to the diffusion constant D and to the transport velocity v E [6,9,10]. Access to the dynamic transport parameters can also be gained through frequency correlations of light transmitted through the material, as first demonstrated by Genack et al [11,12]. Further experiments have revealed both short-range and long-range correlations [13,14], in close agreement with theory [15].Here, we introduce a novel broadband method for measurement of dynamic transport parameters over a wide spectral range in the visible and infrared combining a supercontinuum white-light source and a Fourier transform (FTIR) spectrometer. A schematic overview of the experimental setup is shown in Fig. 1. The supercontinuum light source (Fianium SC-450) produces a 2-mm wide, collimated beam of 2 W optical power in a spectrum spanning the visible and infrared from 450 nm up to 1800 nm wavelength. The transmission of light through a slab of thickness L reduces the intensity roughly by a factor /L times the fraction of solid angle used for detection, resulting in efficiencies as low as 10 −6 for single speckle measurements on optically thick samples. In order to maximize the available optical power in a single speckle spot behind the scattering medium, the beam was focused to a spot of approximately 5 µm in diameter onto the sample using a...

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confidence: 73%

Method for broadband spectroscopy of light transport through opaque scattering media

Muskens

Lagendijk

2009

Opt. Lett.

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“…The suspension is contained in a fused silica capillary tube, with internal dimensions 100 × 2 × 0.2 mm 3 . To characterize the mean free path of this sample, we performed an enhanced-backscatter cone experiment [15] and an escape function experiment [16]. We found a transport mean free path of 0.46 ± 0.1 µm at λ = 633 nm.…”

Section: Apparatus and Samplesmentioning

confidence: 99%

Intrinsic intensity fluctuations in random lasers

2006

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“…The determination of the effective refractive index in strongly scattering media is studied in a recent article [27] where the scattered light transmitted through a porous GaP sample does not show interferences. The analysis shows that the transport of light is well described by the diffusion approximation, provided it takes place in a non-localized regime that is without interferences.…”

Section: Preparation and Structure Of The Samplesmentioning

confidence: 99%

Optical properties of ordered mesoporous layers of silica

2006

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Mesoporous layers of silica are of interest for many optical applications, including the creation of devices ranging from optical sensors to laser sources with promising characteristics. Their optical characterization goes through the interpretation of measurements. We propose to give experimental results of reflectance and scattering measurements concerning mesoporous layers of silica deposited onto silicium substrates. This work shows that their interpretation in terms of optical indices or dielectric function have to be taken with care since scattering is present, and thereby the Kramers -Kronig relations appear not to be fulfilled.

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Experimental determination of the effective refractive index in strongly scattering media

Cited by 26 publications

References 9 publications

Method for broadband spectroscopy of light transport through opaque scattering media

Method for broadband spectroscopy of light transport through opaque scattering media

Intrinsic intensity fluctuations in random lasers

Optical properties of ordered mesoporous layers of silica

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