Unveiling the correlation between non‐diffracting tractor beam and its singularity in Poynting vector

Abstract

This paper investigates the singular optics of nonparaxial light beams in the near field when the light behaves as a tractor beam. New insights into the optical pulling force, which is usually represented by integrating the stress tensor at a black box enclosing the object, are interpreted by the optical singularity of the Poynting vector. The negative nonconservative pulling force originates from the transfer of the azimuthal Poynting vector to the longitudinal component partly owing to the presence of a scatterer. The separatrice pattern and singularity shifts of the Poynting vector unanimously exhibit a differentiable near‐field distribution in the presence of optical pulling force. A new method is established to calculate the near‐field optical force using the differential Poynting vector in the far field. The results obtained provide a clear physical interpretation of the light–matter interaction and manifest the significance of singular optics in manipulating objects.

Controlling Lateral Fano Interference Optical Force with Au–Ge2Sb2Te5 Hybrid Nanostructure

“…One can categorize the singular points of S as vortex, saddle, sink, focus, and node. 64,65 The flows of energy vary with distributions of singular points and thus change the force acting on the nanoparticles. The streamlines of S and distributions of near-field singularities in the x−z plane are illustrated in Figure 4 and ⟨S⟩ r are the constituents of ⟨S⟩ in polar coordinates.…”

Plasmonic properties and energy flow in rounded hexahedral and octahedral nanoparticles

“…Here the effective area is increased, while new critical points appear near its corners, revealing two vortices where streamlines converge. Again, this kind of pattern might be of particular interest not only for energy harvesting applications but also for applications exploiting optical forces on single scatterers [18]. This can be understood through the fact that the Maxwell stress tensor contains a Poynting vector component [18].…”

“…Again, this kind of pattern might be of particular interest not only for energy harvesting applications but also for applications exploiting optical forces on single scatterers [18]. This can be understood through the fact that the Maxwell stress tensor contains a Poynting vector component [18]. Therefore, any change in the Poynting field distribution may change the tensor distribution and hence the forces acting on the scatterer.…”

“…Analytical methods also have been used for analyzing other geometrical shapes, such as core-shell spheres [15] and circular cylinders [3,16]. Interestingly, novel particle functionalities and designs could be devised [3,17,18] by exploiting the near field setup and the Poynting streamline distribution.…”

Mode conversion enables optical pulling force in photonic crystal waveguides

“…43 Since an infinite number of modes are excited during the scattering in this case, it is very complicated to carry out the quantitative analysis of conversion. On the contrary, with several guiding modes in the waveguide, the conversion is clearly described, allowing us to make an apparent conclusion about the pulling character of the optical force.…”