Tailoring ‘photonic hook’ from Janus dielectric microbar

Abstract

A new type of curved subwavelength light beam, a photonic hook (PH), emerging from the diffraction of a light wave at a mesoscale dielectric object with broken internal symmetry (Janus particle), was recently reported. For efficient and technically simpler generation of PHs, we propose a new type of asymmetric Janus microparticles, the orthogonal microbars, composed from materials with different refractive indices. Based on the numerical simulations by means of the finite elements method, we investigate the physical mechanism of PH formation by analyzing the field intensity distribution and the energy fluxes near such particles. The influence of dielectric substrate is also studied for the first time. We show that by changing the refractive index contrast between two parts of Janus bar the shape and curvature of the PHs can be efficiently controlled. The criteria of PH quality for complex characterizing the photonic hook curvature is introduced and discussed as well.