Subwavelength beam manipulation via multiple-metal slits coupled by disk-shaped nanocavity

• Published in: Chinese physics B 2014-03, Vol.23 (3), p.320-325, Article 034213
• Main Author: 郑改革 徐林华 裴世鑫 陈云云
• Format: Article
• Language: English
• Subjects: Angles (geometry); Beams (radiation); Dynamical systems; Focusing; Joining; Nanostructure; Plasmonics; Slits; 亚波长; 光束整形; 多金属; 微腔; 狭缝; 盘形; 耦合; 表面等离子体激元
• ISSN: 1674-1056; 2058-3834; 1741-4199
• DOI: 10.1088/1674-1056/23/3/034213

A novel plasmonic structure consisting of three nano-scaled slits coupled by nano-disk-shaped nanocavities is pro- posed to produce subwavelength focusing and beam bending at optical frequencies. The incident light passes through the metal slits in the form of surface plasmon polaritons （SPPs） ,and then scatters into radiation fields. Numerical simulations using finite-difference time-domain （FDTD） method show that the transmitted fields through the design example can gener- ate light focusing and deflection by altering the refractive index of the coupled nanocavity. The simulation results indicate that the focal spot is beyond the diffraction limit. Light impinges on the surface at an angle to the optical axis will add an extra planar phase front that interferes with the asymmetric phase front of the plasmonic lens, leading to a larger bending angle off the axial direction. The advantages of the proposed plasmonic lens are smaller device size and ease of fabrication. Such geometries offer the potential to be controlled by using nano-positior!i0g systems for applications in dynamic beam shaping and scanning on the nanoscale.