Bubbles, drops and solid particles recognition from real or virtual photonic jets reconstructed by digital in-line holography

The image of the photonic jet (also called caustic) formed by a large, transparent and spherical particle, reconstructed by digital in-line holography (DIH), is shown to be similar to the Airy pattern observed at the focus of a diffraction-limited lens. The analysis of this image, real or virtual depending on whether the particle relative refractive index is above or below one, allows characterizing the particle composition via its refractive index. Experiments clearly demonstrate the value of this method for the simultaneous 3D characterization and differentiation of the dynamics, size and composition of gas, liquid and solid particles in multiphase flows.