Inclusion of the tunneling phase shift for interferometric particle imaging for bubble sizing

Abstract

The interferometric particle imaging technique makes use of the angular oscillations of the scattered light in the forward direction for droplet or bubble sizing. The out-of-focus image consists of fringes, the spacing of which reflects the interference between the surface-reflected light and the twofold-refracted light. Total internal reflection occurs when the incident light hits the bubble at a large incident angle. The tunneling phase shift is not included in the geometric optics approximation, which leads to a deviation from Mie theory. In this work, we modified the formula for describing the fringe spacing by including the tunneling phase shift of total internal reflection. Numerical analysis and experiments showed that the modification is effective for the measurement of bubbles smaller than 60μm.