Controlling the properties of Photonic Jets

In this paper, we discuss the important controllable parameters and dependent parameters in a Photonic Jet formed from plane wave illumination of a micron sized sphere in free space. We use a numerical Finite Element Method (FEM) to vary the diameter of an infinite cylinder and study the resulting properties of the Photonic Jet. These results are compared with the analytical model of Mie theory and experimental results. We show that there is an important oscillation in the focal intensity of the jet as a function of cylinder diameter. This "ripple effect" is predicted by Mie theory and is a result of the modal structure of the sphere. This suggests an optimum sphere size to increase the intensity in the Photonic Jet. We show also that the FWHM oscillates around a value of 0.43X₀. Thus one can optimise the diameter of a cylinder or sphere to create a Photonic Jet with both high intensity and small FWHM.