Lloyd Mirror Laser Interferometer for Diffusion Layer Studies

Abstract

A Lloyd mirror laser interferometer is described which determines the refractive index gradient in a diffusion layer. The interference fringe movement is detected by an array of n-p-n planar silicon photodevices the output of which is recorded by oscillographs. Various modes of measurement are discussed which are suitable for transparent or opaque electrodes. The presently used measuring mode is based on the determination of the reflected ray's optical path length change at various angles of incidence. The refractive index gradient is obtained by an iterative solution of the derived equation for the optical path length change on a digital computer. The time dependence of the fringe movement during electrodeposition from CuSO4 solutions is discussed in addition to the effect of incidence angle and cathode displacement. The use of this interferometer is not limited to electrochemical processes and it can be used for the study of refractive index gradients in heat and other mass transfer boundary layers at solids.

Interferometric Study of the Concentration Change at High Cathodic Current Densities

“…The change of the refractive index at the cathode/solution interface, • during the current flow is obtained by multiplying the refractive index gradient with the diffusion layer thickness (2,3). The change of the refractive index at the cathode/solution interface, • during the current flow is obtained by multiplying the refractive index gradient with the diffusion layer thickness (2,3).…”

“…The experimental setup was described separately in detail (2). Figure 1 shows schematically the electrolysis cell and the Lloyd mirror laser interferometer.…”

“…Figure 1 shows schematically the electrolysis cell and the Lloyd mirror laser interferometer. The interference fringes move past the detectors after the current addition because the optical path length of the reflected beam changes in the developing diffusion layer (2,7). The interference fringes move past the detectors after the current addition because the optical path length of the reflected beam changes in the developing diffusion layer (2,7).…”

“…The optical path length change of the reflected ray was measured as a function of time, incidence angle, and electrode displacement (2). The optical path length change of the reflected ray was measured as a function of time, incidence angle, and electrode displacement (2).…”

“…The optical path length change of the reflected ray was measured as a function of time, incidence angle, and electrode displacement (2). The change of refractive index is obtained by multiplying the refractive index gradient with the diffusion layer thickness (2,3). The change of refractive index is obtained by multiplying the refractive index gradient with the diffusion layer thickness (2,3).…”