Abstract
The optical force on a non-spherical particle subjected to a loosely focused laser beam was calculated using the dynamic ray tracing method. Ellipsoidal particles with different aspect ratios, inclination angles, and positions were modeled, and the effects of these parameters on the optical force were examined. The vertical component of the optical force parallel to the laser beam axis decreased as the aspect ratio decreased, whereas the ellipsoid with a small aspect ratio and a large inclination angle experienced a large vertical optical force. The ellipsoids were pulled toward or repelled away from the laser beam axis, depending on the inclination angle, and they experienced a torque near the focal point. The behavior of the ellipsoids in a viscous fluid was examined by analyzing a dynamic simulation based on the penalty immersed boundary method. As the ellipsoids levitated along the direction of the laser beam propagation, they moved horizontally with rotation. Except for the ellipsoid with a small aspect ratio and a zero inclination angle near the focal point, the ellipsoids rotated until the major axis aligned with the laser beam axis.
Highlights
Optical forces induced by laser beams have been used to manipulate particles or biological cells under a picoNewton-scale force exerted by a laser beam on a micro-sized object capable of moving or trapping the object [1,2,3]
The optical forces on ellipsoidal particles subjected to a Gaussian-distributed laser beam were calculated using the dynamic ray tracing (DRT) method
The optical force was induced by interactions between a transparent object and the laser beam; the effects of the shapes and the inclination angles on the optical force were examined in detail
Summary
Optical forces induced by laser beams have been used to manipulate particles or biological cells under a picoNewton-scale force exerted by a laser beam on a micro-sized object capable of moving or trapping the object [1,2,3]. A loosely focused laser beam, such as are used for optical particle separation, i.e. OC and COPS, illuminates a cross-sectional area wider than the object size; until an equilibrium state is reached, the object undergoes horizontal movement with rotation in a wider region because the optical force and torque change continuously during rotation. Non-spherical particle behavior depends on the object shape, inclination angle, and position, even with fixed laser beam properties, and these parameters can significantly affect the performance of the particle or cell separator. The optical force on a non-spherical particle subject to a loosely focused Gaussian distributed laser beam was calculated using the DRT method. The behaviors of the Received Jul 2012; revised Sep 2012; accepted 25 Sep 2012; published 5 Oct 2012 8 October 2012 / Vol 20, No 21 / OPTICS EXPRESS 24070 ellipsoids during levitation under the optical force were analyzed based on numerical simulations
Sign-in/Register to view highlights & summary 
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
