Higher order microfibre modes for dielectric particle trapping and propulsion

Abstract

Optical manipulation in the vicinity of optical micro- and nanofibres has shown potential across several fields in recent years, including microparticle control, and cold atom probing and trapping. To date, most work has focussed on the propagation of the fundamental mode through the fibre. However, along the maximum mode intensity axis, higher order modes have a longer evanescent field extension and larger field amplitude at the fibre waist compared to the fundamental mode, opening up new possibilities for optical manipulation and particle trapping. We demonstrate a microfibre/optical tweezers compact system for trapping and propelling dielectric particles based on the excitation of the first group of higher order modes at the fibre waist. Speed enhancement of polystyrene particle propulsion was observed for the higher order modes compared to the fundamental mode for particles ranging from 1 μm to 5 μm in diameter. The optical propelling velocity of a single, 3 μm polystyrene particle was found to be 8 times faster under the higher order mode than the fundamental mode field for a waist power of 25 mW. Experimental data are supported by theoretical calculations. This work can be extended to trapping and manipulation of laser-cooled atoms with potential for quantum networks.

Optical Nanofiber Integrated into Optical Tweezers for In Situ Fiber Probing and Optical Binding Studies

“…Besides providing the effective sensing volume of a single ONF for a given particle size, the separation-transmission dependence could be useful for profiling electromagnetic fields that have complex profiles, e.g., for higher order modes propagating in an ONF [27,34]. We also show that the observed, unexpected transmission dependence at small separations cannot be directly explained by the simplistic model we employed, which relies on the field overlap integral, and this clearly requires further investigation.…”

“…The evanescent field structures of non-uniform fiber elements [36] and complex evanescent fields under counter propagating light [22] and higher mode propagation [27,34,37] may also be investigated using this system.…”

“…This allows particles to be selectively trapped, individually or in arrays, and site-specifically introduced to the nanofiber surface. Previously, we showed that addressing nanofibers in a more structured and site-specific way offers many advantages, including facilitating the study of interparticle or particle plus evanescent field interactions [26,27].…”

Propulsion of particles using ultrathin optical fibers

“…Recent proposals have shown that higher order fiber modes (HOMs) can be used to trap atoms [5], making the use of HOMs in MNFs of interest. Due to the improvements in higher order mode MNF fabrication methods [6], some initial experimental studies on (i) the interactions between atoms and HOMs [7] and (ii) the interaction between microparticles and HOMs [8] have been reported. These works exploit the important advantages of HOMs, such as longer evanescent field extension, three dimensional field arrangements and larger mode cut off diameter of the fiber compared to that which can be obtained using the fundamental mode.…”

Optical Nanofibers

“…When a process of mode-conversion happens the differential change in momentum is compensated by a momentum transfer to the nearby atom. Based on this effect, recent papers have explored the possibility of using higher-order modes to control center-of-mass motion of trapped atoms Ebongue et al (2016) and trapped microparticles Maimaiti et al (2015) along the nanofiber.…”