A Silica Core-Shell Cylinder Photonic Nanojet with Cylindrical Pores

A tunable photonic nanojet structure is proposed based on a silica core-shell microcylinder with cylindrical pores. The exact solution of electromagnetic wave scattering from silica core-shell microcylinder was done using the boundary value problem. The effects of porosity, core diameter, shell thicknesses, and type of incident light polarization on the main parameters of photonic nanojet were studied. The results show that with the porosity increasing the photonic nanojet length, focal length, and full with at half maximum of photonic nanojet are increased. However, energy enhancement in the focal spot is decreased by increasing porosity. Furthermore, in many structural conditions, the focal length for TE polarized light is larger or equal to the TM polarization case. The proper photonic nanojet for particular applications is accessible by tuning the geometrical and physical parameters of the porous silica core-shell microcylinder.