Abstract
Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength gold disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. The experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures.
Highlights
Electromagnetic (EM) radiation has long been found to exert optical pressure on objects
In the dynamic mode (DM-Atomic force microscopy (AFM)), an external oscillatory force is applied and information about the cantilever oscillation is monitored in addition to the static deflection[20,26]
As a sensitive force apparatus, dynamic mode atomic force microscopy (DM-AFM) can measure optical forces with a minimal amount of laser power and reduces unwanted effects associated with high laser power, such as nonlinear optical effects and strong photo-thermal effects
Summary
Dongshi Guan[1], Zhi Hong Hang[2], Zsolt Marcet[1,3], Hui Liu[4], I. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. We report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. On the experimental side, continuing efforts have been made to identify accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range[15,16,17,18]. We report a new application of DM-AFM in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity at near-infrared wavelength (λ = 1550 nm). A good agreement is found between the experimental results and numerical simulations
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