1 March 2000 Interferometric measurement of diffusion coefficients through a scanning laser beam
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Optical Engineering, 39(3), (2000). doi:10.1117/1.602422
A new interferometric setup for the determination of the concentration distribution in a diffusion experiment is proposed. The method is applied to the determination of the diffusion coefficient D in a binary saline solution. A thin laser beam scans the diffusion cell along the concentration gradient, which is assumed to be one-dimensional. This beam interferes with the reference beam in a Mach-Zehnder interferometer, and the variation of intensity is recorded by means of photomultiplier tube, digitized, and stored in a computer for further analysis. The phase of the intensity function, modulo 2?, is determined by applying the Fourier-transform method. Assuming linear dependence of the refraction index on the concentration, the unwrapped phase gives a curve similar to the theoretical concentration distribution function. The value of the diffusion coefficient D is obtained by means of an iterative process, comparing experimental and theoretical curves until the best fit is achieved between them, by adjusting the parameter D.
Elvio Alanis, Graciela Romero, Carlos C. Martinez, "Interferometric measurement of diffusion coefficients through a scanning laser beam," Optical Engineering 39(3), (1 March 2000). http://dx.doi.org/10.1117/1.602422



Phase measurement

Fringe analysis


Refractive index

Fourier transforms

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