Characterising Conical Refraction Optical Tweezers
Abstract
Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focussing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focussing on the trap stiffness and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot but benefit from rotational control.
Cite
@article{arxiv.1408.6987,
title = {Characterising Conical Refraction Optical Tweezers},
author = {Craig McDonald and Craig McDougall and Edik Rafailov and David McGloin},
journal= {arXiv preprint arXiv:1408.6987},
year = {2014}
}