Microoptomechanical pumps assembled and driven by holographic optical vortex arrays

Abstract

Beams of light with helical wavefronts can be focused into ring-like optical traps known as optical vortices. The orbital angular momentum carried by photons in helical modes can be transferred to trapped mesoscopic objects and thereby coupled to a surrounding fluid. We demonstrate that arrays of optical vortices created with the holographic optical tweezer technique can assemble colloidal spheres into dynamically reconfigurable microoptomechanical pumps assembled by optical gradient forces and actuated by photon orbital angular momentum.

Fraunhofer diffraction of a Laguerre–Gaussian laser beam by fork-shaped grating

“…The resulting fluid flows can be reconfigured dynamically by changing the topological charges, intensities and positions of the optical vortices in an array, which could be potentially useful for microfluids and lab-on-a-chip applications [28]. …”

Optical vortices in fiber

“…Allen and coworkers [9] demonstrated in 1992 that commonly encountered LaguerreGaussian beams with helical phase given by e iLφ , where L is topological charge and φ is the azimuthal angle, carry OAM of L•ħ per photon, and this has spurred widespread interest across a range of scientific and technological disciplines. These beams have been applied to optical tweezers [10,11], atom manipulation [1,12], nano-scale microscopy [13], as well as communications. Several classical [14] and quantum [15] communications experiments have exploited the inherent orthogonality of OAM modes in free-space by multiplexing information in this additional degree of freedom, thereby increasing the capacity of free-space communications links.…”

“…These two states are either horizontal, vertical, or their linear combinations, as depicted in this figure, or, equivalently, left, or right circular (or their linear combinations -elliptical), which may also be denoted by the spin angular momentum (SAM) that each photon in the beam can carry, given by S = ± 1, representing a SAM of ± 1ħ per photon. For the first higher order solutions designated as LP 11 modes in the scalar approximation, there exist four modal solutions -TE 01 , even 21 HE , odd 21 HE and TM 01 (see Figure 3B or 3D). The two HE 21 modes are strictly degenerate, and have an n eff distinct from the TE 01 and TM 01 modes.…”

Transfer of Orbital Angular Momentum from an Optical Vortex Beam to a Nanoparticle

“…2,2009 axial trapping due to a reduced on-axis backscattered optical component [23] and the creation of optical pumps [24]. In the next section we describe a new type of optical trap that assists confinement of nanoparticles in the dark vortex core and describe the transfer of OAM in such an experimental system.…”