Characterization of photonic nanojets formed by dielectric microfibers

Dielectric microelements with cylindrical and spherical shapes can form an intense sharply focused optical beam, termed "photonic nanojet". Novel optical devices based on photonic nanojet effect can possibly be used in a broad range of biomedical and photonics applications, including super-resolution microscopy, laser tissue surgery, optical endoscopy and spectroscopy, photo-patterning of thin films, and photovoltaics. The use of photonic nanojets in such devices requires meticulous tuning of several parameters of the focusing element and the light source. In this work, we investigated the multifactorial parameterization of photonic nanojets using finite difference time domain (FDTD) simulations. Input parameters that are investigated include index of refraction (1.2-2.2) and diameter (5-50 μm) of the microfiber. In each simulation, the focusing element was illuminated with a plane wave. For each parameter set, the characteristic parameters of the nanojets, such as lateral resolution, back focal length, and the maximum electric field amplification were calculated. Our results showed that optimal values of electric field amplification, back focal length, and lateral resolution do not occur under the same initial parameterization and tend to trade-off with one another. Detailed results from our investigation will provide insight for future tailoring of nanojet properties of microelements in design of novel optical devices for nanophotonics applications.