Comparison of intensity distribution of photonic nanojet according to Gaussian beam and radially polarization beam incidence.

A photonic nanojet (PNJ) is a fine light beam generated from a dielectric microsphere or microcylinder illuminated by a laser and has been applied to nanometer scale measurement and machining. In this study, we attempt to control the PNJ intensity distribution flexibly by adjusting the intensity distribution of two incident laser beams: a Gaussian beam and a radially polarized beam. Then, finite-difference time-domain simulations demonstrated that a large PNJ beam diameter (1.08 λ) could be obtained by Gaussian beam with a small beam radius, whereas a small PNJ beam diameter (0.34 λ) could be obtained by radially polarized beam. Moreover, PNJ with isotropic intensity distribution can be obtained as well as a small PNJ beam diameter by a radially polarized beam incidence to a microsphere. • Incident intensity distribution can control photonic nanojet intensity distribution. • Focusing characteristics of microsphere depend on the incident position of light. • Larger PNJ beam diameter can be obtained by Gaussian beam incidence. • Smaller PNJ beam diameter can be obtained by radially polarized beam incidence. [ABSTRACT FROM AUTHOR]