Transverse spinning of a sphere in a plasmonic field

Abstract

We evaluate optical forces and torques induced by a surface plasmon to a sphere of arbitrary size, i.e. beyond the point-like dipolar limit. Through a multipolar decomposition of the plasmonic field, we demonstrate that the induced torque is purely transverse to the plasmon propagation direction. Our approach removes the inherent ambiguities of the dipolar regime with respect to rotations and emphasizes the crucial role played by dissipation in the onset of the plasmonic torque. We also give realistic estimates of such plasmon-induced spinning of gold spheres immersed in water or air.

Spin angular momentum of surface modes from the perspective of optical power flow

“…As was discussed already in several literatures, the SAM can manifest itself in the mechanical action on probe objects [6,22] or microparticles [8,10]. In these cases, however, its measurement is somewhat complicated because of the additional mechanical action via the orbital AM of the surface mode.…”

“…The AM of a surface-mode light is, however, a transverse one, i.e., its direction is normal to the propagating direction of the light. This unique feature has made it a topic of interest for the last few years [6][7][8][9][10][11][12]. Our group investigated the origin of this AM and showed that its spin component results from the rotation of the electric field comprising the surface mode [7,11].…”

Magnetic and Electric Transverse Spin Density of Spatially Confined Light

“…In nature, such polarization states occur when electromagnetic waves experience strong lateral confinement since the appearance of transverse spin is intimately linked to the presence of longitudinal field components [1][2][3]. Typical optical systems exhibiting a TSD are waveguide modes [4][5][6][7], surface plasmon polaritons [8][9][10], near fields of nanostructures [11], whispering gallery modes [12], interfering plane waves [13], and tightly focused beams [14][15][16].…”

“…Thus, the TSD constitutes the foundation for novel quantum information processing concepts at the nanoscale [5,7]. Further potential applications of the TSD can be found in particle manipulation experiments in optical tweezers [10,13,14] and sensing, for example, of magnetically induced circular dichroism [24,25]. This interest in the TSD also led to the development of highly sensitive techniques, capable of measuring the TSD in propagating and evanescent waves [15,26].…”

Origin of the Abraham spin angular momentum of surface modes

“…Spin angular momentum (SAM) carried by surface waves has been a topic of interest in the literature [1][2][3][4][5][6][7][8][9]. Contrary to the SAM of a circularly polarized light, which is parallel to the propagation axis, the SAM of a surface wave is a transverse one in the sense that its direction is normal to the propagating direction of the wave.…”