Fine features of optical potential well induced by nonlinearity

Abstract

Particles trapped by optical tweezers, behaving as mechanical oscillators in an optomechanical system, have found tremendous applications in various disciplines and are still arousing research interest in frontier and fundamental physics. These optically trapped oscillators provide compact particle confinement and strong oscillator stiffness. But these features are limited by the size of the focused light spot of a laser beam, which is typically restricted by the optical diffraction limit. Here, we propose to build an optical potential well with fine features assisted by the nonlinearity of the particle material, which is independent of the optical diffraction limit. We show that the potential well shape can have super-oscillation-like features and a Fano-resonance-like phenomenon, and the width of the optical trap is far below the diffraction limit. A particle with nonlinearity trapped by an ordinary optical beam provides a new platform with a sub-diffraction potential well and can have applications in high-accuracy optical manipulation and high-precision metrology.

Nonlinearity-induced nanoparticle circumgyration at sub-diffraction scale

“…Compared to the previous methods that formed an orbit, such as schemes with nanofabrication or a laser beam with a particular phase structure, the method we proposed here is much simpler by applying a circularly polarized femtosecond Gaussian laser beam. Previous results have shown that a pair of point-like potential wells could be formed for nonlinear particles when the linearly-polarized femtosecond laser power exceeds a transition power 35 – 37 . By rotating the linear polarization of the laser, such potential-well pair could be rotated accordingly, thus resulting in subsequent circular movement of the trapped particle within the well.…”

Recent Progress on Optical Micro/Nanomanipulations: Structured Forces, Structured Particles, and Synergetic Applications

“…Another experiment, however, showed that the distance between the potential minima was determined by the distribution of the longitude electromagnetic field of the focused beam . Further investigations are still needed with these systems for optical manipulation involving the nonlinearity. ,, Apart from the particle nonlinearity, a particle with linear permittivity locating in the nonlinear surrounding medium can also show the exotic pulling force . Therefore, more efforts considering the degree of freedom of nonlinearity are of necessary for optical manipulation in some physical scenarios.…”

Nano-particle transport and the prediction of a valid area to be trapped based on a plasmonic antenna array

“…Optical tweezers have found tremendous application in various areas, including colloidal sciences, chemistry, and biophysics since their invention several decades ago. [1][2][3][4][5] However, high numerical aperture and large incident intensity are required to get enough optical force when nanoparticles need to be manipulated. This also may damage the biological cell or specimen due to the heat generated by large incident power.…”