Determination of refractive properties of fluids for dual-wavelength interferometry

Abstract

Methods to calculate the refractive properties of solutions at different wavelengths are described by using experimental data at just two wavelengths. The properties are the refractive index and its gradients with temperature and concentration. Cauchy's equation is used to determine the refractive indices. The gradients versus temperature and concentration are then determined by using the Murphy-Alpert and the Lorentz-Lorenz equation, respectively. Finally, the particular case of a triglycine sulfate aqueous solution is considered as an example. The approach should provide the desired information for fringe analysis when dual-wavelength holographic or other interferometry is used for solving heat and mass transfer problems in fluids during crystal-growth experiments.

Imaging techniques for mapping solution parameters, growth rate, and surface features during the growth of crystals from solution

“…More recently, Mehta and Vikram et al have reported the applicability of this technique for determining the temperature and concentration fields inside liquids [313,562]. The principle of dual-wavelength interferometry (and holography) has been described in reports by Vikram et al [564], and is described below. The optical schematic of the two-wavelength interferometry is shown in Fig.…”

“…Extending the above discussion to the dual-wavelength interferometry, we get two independent equations corresponding to the two source wavelengths, l 1 and l 2 , which are then solved to get the separate values for thermal and concentration variations as [564] DC ¼…”

“…In the absence of experimental values, a suitable analytical methodology has been put forth by Vikram et al [563,565] for determining the needed data. The refractive index is obtained using the two-constant Cauchy equation.…”

“…Dual-wavelength interferometry: the applicability of dual-wavelength holographic interferometry for studying triglycine sulfate crystal growth has been discussed by Vikram et al [563,564]. In addition, they have separately studied different aspects of the multiplewavelength holographic interferometry, such as the impact of the fringe order accuracy [565], beam intensity ratio requirements [566] and the fringe contrast and phase effects [567].…”

“…In addition, they have separately studied different aspects of the multiplewavelength holographic interferometry, such as the impact of the fringe order accuracy [565], beam intensity ratio requirements [566] and the fringe contrast and phase effects [567]. Trolinger et al [515] developed a compact crystal growth system that has several optical diagnostics including dual-wavelength interferometry for monitoring crystal growth under microgravity conditions aboard a NASA space mission.…”