Characterization of Liquid-Core/Liquid-Cladding Optical Waveguides of a Sodium Chloride Solution/Water System by Computational Fluid Dynamics

Abstract

A stable liquid/liquid optical waveguide (LLW) was formed using a sheath flow, where a 15% sodium chloride (NaCl) solution functioned as the core solution and water functioned as the cladding solution (15% NaCl/water LLW). The LLW was at least 200 mm in length. The concentration distributions of the liquid core and liquid cladding solutions in the LLW system were predicted by computational fluid dynamics (CFD) to validate the characteristics of the waveguide. The broadening of the region of the fluorescence of Rhodamine B excited by the guided light and the increase in the critical angle of the guided light with the increase in the contact time of the core and the cladding solutions were well explained by CFD calculations. However, no substantial leakage of the guided light was observed despite the considerably large change in the refractive index profile of the LLW; thus, a narrower and longer waveguide was realized.

Development of Tetrahydrofuran/Water Optical Waveguide and Its Application to the Observation of Extraction Behavior of l-Anilino-8-naphtalene Sulfonate at the Tetrahydrofuran/Water Interface

“…To describe the mixing of the core and cladding liquids, a three-dimensional Navier-Stokes equation and a convection-diffusion equation based on Fick's law with laminar flow under steady state were chosen. The basic way of CFD simulation was almost the same as that described in our previous paper, 13 except that the different software (STAR CD © ) was used. The diffusion coefficient of THF-water mixture in water is known to change considerably, depending on its concentration in the range from ca.…”

“…[6][7][8] Besides those waveguides, liquid/liquid optical waveguides (LLWs), which have a liquid-core/liquid-cladding structure, have firstly been proposed by our group. [9][10][11][12][13] LLWs have been formed with sheath flow of liquids from concentric glass capillaries into an outer glass capillary. Both immiscible solvent systems (e.g., toluene/water, diethyl ether/water) and miscible solvent systems (e.g., tetrahydrofuran (THF)/water, sodium chloride solution/water) can be used to form the LLWs.…”

“…We have been trying to use these LLWs as new tools for studying the liquid/liquid interfaces. [10][11][12][13] The concept of LLW, on the other hand, has recently been extended to the microchip fields, and it has become one of the key elements in the new field of "optofluidics," where it is applied to manipulate light in micro-chips, e.g., as an optical switch and an evanescent coupler. [14][15][16][17][18][19][20][21] Chemical reactions and mass-transfer phenomena at the liquid/liquid interface have attracted much attention of researchers of various fields, such as separation chemistry, organic syntheses and biology.…”

A Liquid-core Liquid-cladding Optical Waveguide Based on Thermal Gradients across the Laminar Flow of Water in Capillary Tubing

“…Recently, liquid-core/liquid-cladding optical waveguides (LLWs), whose concept was firstly introduced by us, [1][2][3][4] have widely been studied as a key element of optofluidics. [5][6][7][8][9][10][11][12] LLWs are usually built using two kinds of miscible liquids that have different refractive indices such as 50% ethanol/water, 5% NaCl aqueous solution/water and etc.…”