Nonlinear modulation on optical trapping in a plasmonic bowtie structure

Surface plasmon optical tweezers based on micro- and nano-structures are capable of capturing particles in a very small spatial scale and have been widely used in many front research fields. In general, distribution of optical forces and potential wells exerted on the particles can be modulated by controlling the geometric parameters of the structures. However, these fabricated structures are irreversible once processed, which greatly limits its application in dynamic manipulation. The plasmonic field in these structures can be enhanced with orders of magnitude compared to the excitation light, offering a possibility to stimulate nonlinear responses as a new degree of freedom for dynamic modulation. Here, we theoretically demonstrate that the optical force and potential well can be modulated on account of the nonlinear Kerr effect of a gold bowtie structure under a pulsed laser with high peak power. The results verify that the trapping states, including the position, width, and depth of the potential well, can be dynamically modulated by changing intensity of the incident laser. It provides an effective approach for stable trapping and dynamic controlling of particles on nanostructure-based plasmonic trapping platforms and thus has great application potential in many fields, such as enhanced Raman detection, super-resolution imaging, and optical sensing. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

By controlling the geometric parameters of micro- and nano-structures and using pulsed lasers with high peak power, optical forces and potential wells in surface plasmon optical tweezers based on gold bowtie structures can be dynamically modulated, offering a new approach for stable trapping and dynamic control of particles.