Abstract
The force-field generated by a near-field optical trap is analyzed. A C-shaped engraving on a gold film is considered as the trap. By separating out the conservative component and the solenoidal component of the force-field using Helmholtz-Hodge decomposition, it was found that the force is non-conservative. Conventional method of calculating the optical potential from the force-field is shown to be inaccurate when the trapping force is not purely conservative. An alternative method is presented to accurately estimate the potential. The positional statistics of a trapped nanoparticle in this non-conservative field is calculated. A model is proposed that relates the position distribution to the conservative component of the force. The model is found to be consistent with numerical and experimental results. In order to show the generality of the approach, the same analysis is repeated for a plasmonic trap consisting of a gold nanopillar. Similar consistency is observed for this structure as well.
Highlights
Trapping of micron and submicron sized particles have received significant attention in several branches of science including biotechnology[1,2,3], physics[4], and chemistry[5]
Such setups are known as optical tweezers where particles become trapped near the focus point of the laser beam due to the gradient forces[7,8,9]
We will mainly focuse on a plasmonic trap consisting of a C-shaped engraving (CSE) on a gold film
Summary
Trapping of micron and submicron sized particles have received significant attention in several branches of science including biotechnology[1,2,3], physics[4], and chemistry[5]. It is well known that the position of a particle trapped in a potential well created by a conservative force-field follows a Boltzmann distribution[9]. A detailed analysis on how the trapping potential for a non-conservative force-field can be calculated and used to characterize the position distribution of a trapped nanoparticle has not appeared in the literature.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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.
