Study On Optical Trapping And Transport With Nanoantenna Array

Optical tweezers are frequently-used to trap or manipulate biological cells and colloidal material in biology laboratories. Due to the diffraction limit of light, it is difficult for traditional optical tweezers to trap and manipulate sub-wavelength sized particles. However, large optical gradient field generated by plasmonic metal structure could be used to realize trap of nano-sized particles. On the basis of the unique design of plasmonic metal structure, the nano-sized particles could be transferred stably in a specific range.In this paper a gold nanoantenna array structure with four different lengths antennas is designed to realize the stable transport of nano-sized particles. With different wavelengths of incident light, the antennas are resonant respectively. The work of this paper includes mainly two aspects as followed:Firstly, a gold nanoantenna array structure with four different lengths antennas is designed and the four antennas have different resonant wavelengths. Finite-element method is used to calculate optical responses of plasmonic structure. The property of optical coupling between four antennas make it suitable as a particle conveyor.Secondly, on the basis of existing plasmonic structure, a dielectric particle with 90nm diameter is applied to simulate the actual situation. The maxwell stress tensor method is used to calculate the optical force exerted on the nano-sized particle. Trajectory of the particle is described and the valid area of stable transport is demonstrated. The data of trapping potential verify the particle can overcome barrier from Brown motion.