Gear-like rotatable optical trapping with radial carpet beams

Jamal Bayat,Faegheh Hajizadeh,Saifollah Rasouli,Ali Mohammad Khazaei

doi:10.1038/s41598-020-68695-8

Jamal Bayat, Faegheh Hajizadeh + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-68695-8

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Abstract

Optical tweezers have become a powerful tool in the fields of biology, soft condensed matter physics, and nanotechnology. Here, we report the use of recently introduced radial carpet beams (RCBs) in the optical tweezers setup to trap multiple particles. An RCB is produced by diffraction of a plane or Gaussian beam from an amplitude radial grating. Because of the radial symmetry of the grating, all the diffraction orders are propagated along the optical axis and are used for trapping. Based on the number of grating spokes, the produced RCB has a definite number of high-intensity spots on the transverse plane located over a circular ring. These high-intensity spots of the beam provide multi-traps when it passes through an objective lens and have enough gradient force to trap polystyrene and silica particles. Moreover, the diffracted light from the grating has this property to transfer the angular momentum. We show that the multi-trapped birefringent particles could rotate in their own traps when polarization of the trapping RCB to be circular. In addition, the orbital rotation of the particles is simply executable by manually rotating the grating in its plane around the optical axis.

Highlights

Optical tweezers have become a powerful tool in the fields of biology, soft condensed matter physics, and nanotechnology
One half of the Nobel Prize in Physics 2018 has been awarded to Arthur Ashkin for his invention of ’optical tweezers’ that is widely used in manipulating micro- to nanoparticles, atoms, molecules, and biological cells
The diffraction of a plane wave from radial amplitude and/or phase gratings reveals a complete set of radial beams so called “Combined half-integer Bessel-like beams” where in some special cases they named “radial carpet beams (RCB)”[23]

Summary

Introduction

Optical tweezers have become a powerful tool in the fields of biology, soft condensed matter physics, and nanotechnology. We report the use of recently introduced radial carpet beams (RCBs) in the optical tweezers setup to trap multiple particles. A general alternative to generate multiple-beam optical tweezers is to use Spatial Light Modulators (SLM) such as Digital Micro Devices (DMD) and Liquid crystal SLM to modify the laser wavefrom[20]. They significantly expand the potentials of multiple trapping by a single beam even for single neutral atoms[21], generating large numbers of the traps typically result in low diffraction efficiency and unwanted diffraction o rders[22]. By rotating the radial grating, the resulted multiple traps rotate around the optical axis, simultaneously

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