Experimental demonstration of a tunable photonic hook by a partially illuminated dielectric microcylinder

In this Letter, we report the experimental observations of a tunable curved photonic nanojet (photonic hook) generated by a 5 µm polydimethylsiloxane microcylinder deposited on a silicon substrate and illuminated by 405 nm laser beam. A moveable opaque aluminum-mask is mounted in front of the microcylinder implementing partial illumination and imparting spatial curvature to the photonic nanojet. Experimental results of main parameters (tilt angle, width, and intensity) of emerging photonic hooks exhibit close agreement with numerical predictions of the near-field optical structures. The experimentally measured full widths at half-maximum of photonic hooks are 0.48λ, 0.56λ, and 0.76λ for tilt angles of θ=0∘, 5.7°, and 20.1°, respectively. Photonic hooks possess great potential in complex manipulation such as super-resolution imaging, surface fabrication, and optomechanical manipulation along curved trajectories.