Comparison of Photonic Nanojets Produced by Dielectric Prism and Cylinder

Using the finite element method implemented in the COMSOL Multiphysics software package, we studied numerically the dependence of the focal spot parameters on the incident radiation, which was a wave with a waist width of 80 μm and wavelengths of 3 μm, 4 μm, and 5 μm focused by prisms with a triangular and spherical profile. In particular, it was shown that a prism always forms a focal spot with smaller sizes. Moreover, the use of a prism leads to a smaller dependence of the focal spot width on the wavelength of the focused light.