Fig. 1: Illustration of the setup and typical experimental results for the movement trajectory of the trapped nonlinear particle.
From: Nonlinearity-induced nanoparticle circumgyration at sub-diffraction scale
a Schematic of nonlinear nanoparticle (e.g., gold (Au), silver (Ag)) trapped by a circularly polarized Gaussian laser beam. b Image of the scattering light from the nonlinear gold nanoparticle (GNP) shows that the GNP was trapped in a ring shape potential well, when the incident beam was switched from continuous mode to femtosecond mode. c, d Successive frames of a movie recording, which show the rotation of a GNP trapped by a circularly polarized femtosecond laser with right handedness and left handedness, respectively. Images were taken by a CMOS camera at 1500 frames/s; green lines and arrows indicate the direction of GNP motion. Red arrows indicate the direction of handedness of circular polarization. The length of the white scale bars in all figures is 0.5 μm. e 2-D trajectory projection of an orbiting particle in the transverse plane recorded by front-side-view imaging system. f The intensity of the scattering light from the rotation particle is measured by the photomultiplier tube (PMT). g The Fourier transformation of the scattering intensity signal shows the rotation frequency. In Fig. 1b–g, the mean power P of trapping laser beam is about 630 mW, NA value of the trapping lens is 0.65.
