Measurement of the refractive index of highly turbid media

Calhoun, William; Maeta, Hiroshi; Combs, Anthony W.; Bali, L. M.; Bali, Samir

doi:10.1364/ol.35.001224

Cited by 48 publications

(54 citation statements)

References 11 publications

(9 reference statements)

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“…All of these error estimations should be discussed quantitatively in the future. When the gases and aerosol particles in the atmosphere are considered as a whole, the AERI n eff can be written as follows (van de Hulst, 1957;Barrera et al, 2007;Calhoun et al, 2010):…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…The results showed that the imaginary parts of the AERISP were related to the turbulent transport process and the spatial distribution characteristics of aerosols. The atmospheric equivalent refractive index (AERI) depends on scattering and absorption of aerosol particles (Barrera et al, 2007;Calhoun et al, 2010;van de Hulst, 1957), and should be related to the mass concentration of aerosol particles. Therefore, similar to the fact that the temperature structure parameter can reflect the sensible heat flux, the imaginary part of the AERISP may reflect the aerosol mass flux.…”

Section: Introductionmentioning

confidence: 99%

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A new method for estimating aerosol mass flux in the urban surface layer using LAS technology

et al. 2016

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Abstract. Atmospheric aerosol greatly influences human health and the natural environment, as well as the weather and climate system. Therefore, atmospheric aerosol has attracted significant attention from society. Despite consistent research efforts, there are still uncertainties in understanding its effects due to poor knowledge about aerosol vertical transport caused by the limited measurement capabilities of aerosol mass vertical transport flux. In this paper, a new method for measuring atmospheric aerosol vertical transport flux is developed based on the similarity theory of surface layer, the theory of light propagation in a turbulent atmosphere, and the observations and studies of the atmospheric equivalent refractive index (AERI). The results show that aerosol mass flux can be linked to the real and imaginary parts of the atmospheric equivalent refractive index structure parameter (AERISP) and the ratio of aerosol mass concentration to the imaginary part of the AERI. The real and imaginary parts of the AERISP can be measured based on the lightpropagation theory. The ratio of the aerosol mass concentration to the imaginary part of the AERI can be measured based on the measurements of aerosol mass concentration and visibility. The observational results show that aerosol vertical transport flux varies diurnally and is related to the aerosol spatial distribution. The maximum aerosol flux during the experimental period in Hefei City was 0.017 mg m −2 s −1 , and the mean value was 0.004 mg m −2 s −1 . The new method offers an effective way to study aerosol vertical transport in complex environments.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A new method for estimating aerosol mass flux in the urban surface layer using LAS technology

et al. 2016

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“…It is noteworthy that, despite all the attention, a precise in situ determination of several important optical properties of intralipid emulsions, such as the particle size, refractive index, and attenuation coefficient (which is commonly expressed as the imaginary part of a complex refractive index [13][14][15][16][17][18][19][20][21] ), has continued to elude researchers. 28 The chief difficulty arises from the fact that intralipid emulsions, being highly turbid, have a large attenuation coefficient.…”

Section: Introductionmentioning

confidence: 99%

“…29 Other attempts to extract the complex refractive index by modeling the reflectance data either introduce extraneous fitting parameters (beyond the two parameters of interest, namely, the real and imaginary parts of the refractive index) resulting in overfitting of the data 19,20 or focus on only the critical angle region, which is just a small subset of the reflectance data. [14][15][16][17][18] . Both approaches have built-in arbitrariness causing wide variation in extracted values.…”

Section: Introductionmentioning

confidence: 99%

“…Our method employs a real-time sensitive measurement of total internal reflection (TIR) of a divergent laser beam from the sample surface, over the full range of incident angles, i.e., for reflectivity values going from unity in the TIR regime to nearly zero in the non-TIR regime where almost all the light is transmitted. We employ a new empirical model we introduced earlier 16,17,18 that incorporates angle-dependent penetration of the incident light into the medium during TIR. However, in contrast to Refs.…”

Section: Introductionmentioning

confidence: 99%

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Accuratein situmeasurement of complex refractive index and particle size in intralipid emulsions

et al. 2013

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Abstract. A first accurate measurement of the complex refractive index in an intralipid emulsion is demonstrated, and thereby the average scatterer particle size using standard Mie scattering calculations is extracted. Our method is based on measurement and modeling of the reflectance of a divergent laser beam from the sample surface. In the absence of any definitive reference data for the complex refractive index or particle size in highly turbid intralipid emulsions, we base our claim of accuracy on the fact that our work offers several critically important advantages over previously reported attempts. First, our measurements are in situ in the sense that they do not require any sample dilution, thus eliminating dilution errors. Second, our theoretical model does not employ any fitting parameters other than the two quantities we seek to determine, i.e., the real and imaginary parts of the refractive index, thus eliminating ambiguities arising from multiple extraneous fitting parameters. Third, we fit the entire reflectanceversus-incident-angle data curve instead of focusing on only the critical angle region, which is just a small subset of the data. Finally, despite our use of highly scattering opaque samples, our experiment uniquely satisfies a key assumption behind the Mie scattering formalism, namely, no multiple scattering occurs. Further proof of our method's validity is given by the fact that our measured particle size finds good agreement with the value obtained by dynamic light scattering. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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