Creating stable trapping force and switchable optical torque with tunable phase of light

Abstract

Light-induced rotation of microscopic objects is of general interest as the objects may serve as micromotors. Such rotation can be driven by the angular momentum of light or recoil forces arising from special light-matter interactions. However, in the absence of intensity gradient, simultaneously controlling the position and switching the rotation direction is challenging. Here, we report stable optical trapping and switchable optical rotation of nanoparticle (NP)–assembled micromotors with programmed phase of light. We imprint customized phase gradients into a circularly polarized flat-top (i.e., no intensity gradient) laser beam to trap and assemble metal NPs into reconfigurable clusters. Modulating the phase gradients allows direction-switchable and magnitude-tunable optical torque in the same cluster under fixed laser wavelength and handedness. This work provides a valuable method to achieve reversible optical torque in micro/nanomotors, and new insights for optical trapping and manipulation using the phase gradient of a spatially extended light field.

Analysis of the magneto-thermoelastic vibrations of rotating Euler–Bernoulli nanobeams using the nonlocal elasticity model

“…Current density (J), induced magnetic field (h), and the strength of electric field (E) are all variables in Eqs. ( 9) and (10). Also, H is the total magnetic field, and the magnetic field permeability is denoted by μ 0 .…”

“…Hoshina et al [9] presented a method that can rotate nanoobjects and switch the direction in which they are rotating in both macroscopic and nanoscopic regions. Nan et al [10] demonstrated a worldwide method for the out-ofplane rotation of various objects, including spherical symmetry and isotropic things, by use of an arbitrary low-energy laser. Within the nonlocal thermoelasticity concept framework, Abouelregal [11] et al demonstrated the effect that heat transfer has on the dynamics of a spinning nanobeam.…”

Optothermal rotation of micro-/nano-objects

“…[9][10][11] The light-powered rotation, termed optical rotation, holds significant application potential in nano-torque sensing, [12][13][14] nanosurgery, 15,16 micro/nanofluidic systems, 17,18 and so on. To achieve optical rotation, dynamic intensity profile, 19,20 nonlinear polarization, 12,21,22 optical angular momenta, 23,24 or radiation pressure 25 is typically utilized to produce asymmetric light-matter interactions for the generation of optical torques. In addition, sophisticated designs are also required on the rotating targets, which typically possess on-demand geometry, optical birefringence, or specific compositions.…”

Analysis of the magneto-thermoelastic vibrations of rotating Euler- Bernoulli nanobeams using the nonlocal elasticity model

“…Hoshina et al [9] present a method that can rotate nanoobjects and switch the direction in which they are rotating in both macroscopic and nanoscopic regions. Nan et al [10] demonstrated a worldwide method for the out-of-plane rotation of various objects, including spherical symmetry and isotropic things, by use of an arbitrary low-energy laser. Within the nonlocal thermoelasticity concept framework, Abouelregal [11] et al demonstrated the effect that heat transfer has on the dynamics of a spinning nanobeam.…”