Graphene Nanoribbon Plasmonic Conveyor Belt Network for Optical Trapping and Transportation of Nanoparticles

Optical tweezers based on metallic plasmonic structures can achieve stable trapping of objects with deep subwavelength dimensions. However, due to the lack of real-time tunability of metallic plasmonic structures, manipulating trapped objects is challenging and usually requires sophisticated tuning of the excitation light source, which limits the application scope of such plasmonic tweezers. Here, we propose the operation principle and analyze the performance of a two-dimensional (2D) network of plasmonic conveyor belts employing electrically tunable graphene plasmonic structures, which can simultaneously and independently trap and transport multiple nanoparticles to arbitrary target locations within the network. Transportation of nanoparticles is achieved by dynamically reconfiguring the carrier density distribution in a graphene nanoribbon based network structure using an array of back-gates, without a need for any change to the excitation light source. Our numerical analyses show that relatively large optical forces can be induced on nanoparticles with tens of nm characteristic dimensions at a moderate excitation source intensity (e.g., 1 mW/μm2), and the corresponding trapping potential energy exceeds 10 kBT at room temperature, which guarantees stable trapping during nanoparticle manipulation. Suitable designs of the junction structures in the network are developed, and effective schemes for all-directional routing of nanoparticles at these junctions are proposed and quantitatively analyzed. Such graphene-based plasmonic conveyor belt networks have high design flexibility and system scalability and, therefore, may find a wide range of applications in different areas such as lab-on-a-chip, assembling complex nanostructures and devices, studying many-body physics, and advancing quantum information technologies.