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

Abstract

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 0.48 λ , 0.56 λ , and 0.76 λ 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.

Concept of photonic hook scalpel generated by shaped fiber tip with asymmetric radiation

“…Following to references, [ 21,22 ] the physics of the curved PH formation can be explained as follows. The refractive index of fiber and width of illumination determines the angle of refraction on an interface via the generalized Snell's law.…”

“…If the width of the illuminating beam is less than the fiber diameter, the components of the wave vector K ∥ do not cancel each other inside the fiber through the local destructive interference. [ 21,22 ] The wave vector K ∥ is relative to the symmetry of the fiber axis, which creates the curvature profile of the PH. On the other hand, the components of the wave vector K ⊥ determine the length of the PH along the propagation direction.…”

“…It has been shown that a PH in free space can also be obtained by asymmetric illumination of symmetric microparticle. [ 21,22 ] The PH is suitable for complex utilization such as super‐resolution imaging and optomechanical manipulation in curved trajectory. [ 23 ] The tip shape of optical fiber determines its function since it controls the light distribution pattern on a specific sample.…”

Optical trapping with structured light: a review

“…It is clear that optical tweezers will evolve as beam shaping technologies evolve, for example, tractor beams, [177][178][179][180][181][182]242 anomalous vortex beams, 243,244 partially coherent vortex beams, 245,246 grafted vortex beams, 247,248 and structured light with photonic and plasmonic structures. [249][250][251][252][253] There is no doubt that new developments in structured light beams will continuously boost the fields of optical manipulation. 254 Moreover, among the diverse optical trapping schemes discussed in this review, in our view, several topics have great potential to find exciting future applications, such as the optical trapping of metal particles [183][184][185][186][187][188][189] and chiral particles, 52,53 vacuum levitation, structured light in waveguides, [255][256][257][258][259] optical binding and other collective motions in structured light fields, 113,185,[260][261][262] quantum optomechanics, 30 and optical trapping for multidisciplinary applications.…”

Wavelength‐Scale Photonic Space Switch Proof‐Of‐Concept Based on Photonic Hook Effect

“…Basically, the most common method is to use an optically homogeneous dielectric microparticle with an asymmetric geometrical shape (or an asymmetry of the illuminating beam). For example, this can be a rectangular prism, [ 13,14,16 ] a circular cylinder [ 17 ] or an ellipsoid under side illumination, [ 18 ] an asymmetric planar lens in the form of an off‐axis Fresnel zone plate (FZP), [ 19 ] etc. Another way to obtain a curved photonic flux is to use the geometrically symmetric particles, but with a specially imposed asymmetry of the internal refractive indices.…”