Photonic Nanojets in Optical Tweezers

TL;DR

This paper explores the generation and control of photonic nanojets using optical tweezers, demonstrating a novel double-beam setup to enable on/off switching of nanojets for enhanced applications.

Contribution

It introduces a new method employing double optical tweezers with collinear beams to precisely control photonic nanojets, overcoming previous limitations in stable nanojet formation.

Findings

Nanojets generated with focused beams differ from traditional plane wave methods.

Double optical tweezers enable on/off switching of nanojets.

The setup improves potential applications in ultramicroscopy and intracellular studies.

Abstract

Photonic nanojets have been brought into attention ten years ago for potential application in ultramicroscopy, because of its sub-wavelength resolution that can enhance detection and interaction with matter. For these novel applications under development, the optical trapping of a sphere acts as an ideal framework to employ photonic nanojets. In the present study, we generated nanojets by using a highly focused incident beam, in contrast to traditional plane waves. The method inherits the advantage of optical trapping, especially for intracellular applications, with the microsphere in equilibrium on the beam propagation axis and positioned arbitrarily in space. Moreover, owing to optical scattering forces, when the sphere is in equilibrium, its center shifts with respect to the focal point of the incident beam. However, when the system is in stable equilibrium with a configuration involving optical tweezers, photonic nanojets cannot be formed. To overcome this issue, we employed double optical tweezers in an unorthodox configuration involving two collinear and co-propagating beams, the precise positioning of which would turn on/off the photonic nanojets, thereby improving the applicability of photonic nanojets.