Photonic nanojets with mesoscale high-index dielectric particles

Abstract

In this work, we demonstrate the ability of high-index dielectric particles immersed in air to generate photonic nanojets with extreme resolution (∼0.06λ0). Both 2D (cylindrical) and 3D (spherical) particles are analyzed, and their profile is truncated using the Weierstrass formulation for solid immersion lenses to produce a photonic nanojet at the output surface under plane wave illumination. Their focusing capability is evaluated in terms of the spatial resolution achieving subwavelength values of ∼0.14λ0 and ∼0.06λ0 for a truncated cylinder and sphere, respectively. The capability of the truncated sphere to enhance the backscattering produced by two small metallic spherical scatterers placed near the photonic nanojet is evaluated by using a scanning-probe microscopy configuration. The imaging capabilities of this technique are also analyzed by moving the metallic spheres in the transversal plane where the photonic nanojet is produced. The results presented here improve greatly the typical resolution of photonic nanojets generated with dielectric particles with a small index contrast. In addition, the high-index material allows using mesoscale particles, leading to a more compact setup. These results may find applications in areas such as microscopy, imaging, and sensing devices where a subwavelength resolution below the diffraction limit is needed.