Polarization effect on focal length of photonic nanojet

A theoretical study has been performed on effect of polarization state of incident plane wave on performance of photonic nanojet (PNJ) generated by a sphere or an ellipsoid or an elliptical cylinder scatterer, among which the sphere has a higher while the ellipsoid and elliptical cylinder have a relatively low geometric symmetry. The study shows that the polarization state of incident wave affects mainly full width at half maximum of the PNJ in case of the sphere scatterer, whilst influences mainly the focal length in case that the scatterer is an ellipsoid or elliptical cylinder. Further study focuses on the effect on the focal length of the PNJ generated by either an ellipsoid or an elliptical cylinder scatterer, and the influences of type, geometric size and orientation of scatterer on the effect. The results show that the effect prefers to take place for a scatterer with a lower symmetry, and the type, geometric size and orientation of scatterer all can influence the effect. There exists a maximum effect at a certain symmetry and the maximum effect depends on the type, geometric size and orientation of scatterer. In the case of the elliptical cylinder, the focal length of PNJ generated can increase by as much as two times as the polarization state is changed.