Optical trapping using transverse electromagnetic(TEM)-like mode in a coaxial nanowaveguide

Optical traps have emerged as powerful tools for immobilizing and manipulating small particles in three dimensions. Fiber-based optical traps(FOTs) significantly simplify optical setup by creating trapping centers with single or multiple pieces of optical fibers. In addition, they inherit the flexibility and robustness of fiber-optic systems.However, trapping 10-nm-diameter nanoparticles(NPs)using FOTs remains challenging. In this study, we model a coaxial waveguide that works in the optical regime and supports a transverse electromagnetic(TEM)-like mode for NP trapping. Single NPs at waveguide front-end break the symmetry of TEM-like guided mode and lead to high transmission efficiency at far-field, thereby strongly altering light momentum and inducing a large-scale back-action on the particle. We demonstrate, via finitedifference time-domain(FDTD) simulations, that this FOT allows for trapping single 10-nm-diameter NPs at low power.