Paper detail

Material Independent Long Distance Pulling, Trapping, and Rotation of Fully Immersed Multiple Objects with a Single Optical Set-up

Optical pulling with tractor beams is so far highly dependent on (i) the property of embedding background or the particle itself , (ii) the number of the particles and/or (iii) the manual ramping of beam phase. A necessary theoretical solution of these problems is proposed here. This article demonstrates a novel active tractor beam for multiple fully immersed objects with its additional abilities of yielding a controlled rotation and a desired 3D trapping. Continuous and stable long distance levitation, controlled rotation and 3D trapping are demonstrated with a single optical set-up by using two coaxial, or even non-coaxial, superimposed non-diffracting higher order Bessel beams of reverse helical nature and different frequencies. The superimposed beam has periodic intensity variations both along and around the beam-axis because of the difference in longitudinal wave-vectors and beam orders, respectively. The difference in frequencies of two laser beams makes the intensity pattern move along and around the beam-axis in a continuous way without manual ramping of phase, which allows for either linear motion (forward or backward) or angular movement (clockwise or anticlockwise) of fully immersed multiple particles. As a major contribution, the condition for increasing the target binding regions is also proposed to manipulate multiple immersed objects of different sizes and shapes.