Mode conversion enables optical pulling force in photonic crystal waveguides

We propose a robust scheme to achieve optical pulling force using the guiding modes supported in a hollow core double-mode photonic crystal waveguide instead of the structured optical beams in free space investigated earlier. The waveguide under consideration supports both the 0th order mode with a larger forward momentum and the 1st order mode with a smaller forward momentum. When the 1st order mode is launched, the scattering by the object inside the waveguide results in the conversion from the 1st order mode to the 0th order mode, thus creating the optical pulling force according to the conservation of linear momentum. We present the quantitative agreement between the results derived from the mode conversion analysis and those from rigorous simulation using the finite-difference in the time-domain numerical method. Importantly, the optical pulling scheme presented here is robust and broadband with naturally occurred lateral equilibriums and has a long manipulation range. Flexibilities of the current configuration make it valuable for the optical force tailoring and optical manipulation operation, especially in microfluidic channel systems

Momentum-topology-induced optical pulling force

We report an ingenious mechanism to obtain robust optical pulling force by a single plane wave via engineering the topology of light momentum in the background. The underlying physics is found to be the topological transition of the light momentum from a usual convex shape to a starlike concave shape in the carefully designed background, such as a photonic crystal structure. The principle and results reported here shed insightful concepts concerning optical pulling, and pave the way for a new class of advanced optical manipulation technique, with potential applications of drug delivery and cell sorting.Ministry of Education (MOE)Published versionThis work was supported by National Natural Science Foundation of China (Grants No. 11874134 and No. 11704088). We thank the HPC Studio at Physics Department of Harbin Institute of Technology for access to computing resources through [email protected]. C-W.Q acknowledges the support from the Ministry of Education, Singapore (Grant No. R-263-000-D11-114). M. N-V. acknowledges support from Ministerio de Ciencia, Innovacion y Universidades of Spain through Grants No. FIS2014-55563-REDC, No. FIS2015-69295-C3-1-P, and No. PGC2018-095777-B-C21