A three-dimensional particle in a potential field

S. A. Gavrilyuk, I. V. Krasnov, Sergey P. Polyutov

Explicit expressions are derived for the rectified radiative forces (RRFs) related to the action of a weak interfering optical field of an arbitrary three-dimensional (3D) configuration upon resonance particles featuring the J =0 → J =1 quantum transition. It is shown that, in contrast to the case of a monochromatic field, there are simple 3D biharmonic field configurations for which the ratio of the vortex and potential RRF components can be controlled by adjusting frequencies and polarizations of the interfering light waves. This modification of the RRF structure gives rise to qualitatively different types of both vortex and potential light-induced particle motions that may lead to a 3D spatial localization (confinement) of these particles within the cells of an effective optical lattice with a period significantly greater than the light wavelength. In particular, the particles may perform a stable rotational motion along closed trajectories inside the elementary cells.

‎Louis Marchildon

Yoshihiko Arita, Michaël Mazilu, Mingzhou Chen +4 more

We demonstrate the transfer of orbital angular momentum to optically levitated microparticles in vacuum [1]. We prepare two-dimensional and three-dimensional optical potentials. In the former case the microparticle is placed within a Laguerre-Gaussian beam and orbits the annular beam profile with increasing angular velocity as the air drag coefficient is reduced. We explore the particle dynamics as a function of the topological charge of the levitating beam. Our results reveal that there is a fundamental limit to the orbital angular momentum that may be transferred to a trapped particle, dependent upon the beam parameters and inertial forces present. This effect was predicted theoretically [2] and can be understood considering the underlying dynamics arising from the link between the magnitude of the azimuthal index and the beam radius [3]. Whilst a Laguerre-Gaussian beam scales in size with azimuthal index `, recently we have created a “perfect” vortex beam whose radial intensity profile and radius are both independent of topological charge [4, 5]. As the Fourier transform of a perfect vortex yields a Bessel beam. Imaging a perfect vortex, with its subsequent propagation thus realises a complex three dimensional optical field. In this scenario we load individual silica microparticles into this field and observe their trajectories. The optical gradient and scattering forces interplay with the inertial and gravitational forces acting on the trapped particle, including the rotational degrees of freedom. As a result the trapped microparticle exhibits a complex three dimensional motion that includes a periodic orbital motion between the Bessel and the perfect vortex beam. We are able to determine the three dimensional optical potential in situ by tracking the particle. This first demonstration of trapping microparticles within a complex three dimensional optical potential in vacuum opens up new possibilities for fundamental studies of many-body dynamics, mesoscopic entanglement [6, 7], and optical binding [8, 9].

D. Baye, M. Dufour, Benjamin Fuks E

Marija Drndić, C. S. Lee, Robert M. Westervelt

Three-dimensional (3D) microelectromagnets were developed to control particle motion in electromagnetic-field landscapes in vacuum near a chip. Multiple layers of micrometer-scale conductors separated by transparent insulators create particle containers with deep, symmetric, and time-dependent potentials, suitable for integration in quantum circuits. Single and coupled multiple 3D traps, integrated 3D traps with a mirror, 3D guides for neutral particles with spin, and traps for electrons in vacuum are described.