Abstract
When an ultrathin silver nanowire with a diameter less than 100 nm is placed on a photonic band gap structure, surface plasmons can be excited and propagate along two side-walls of the silver nanowire. Although the diameter of the silver nanowire is far below the diffraction limit, two bright lines can be clearly observed at the image plane by a standard wide-field optical microscope. Simulations suggest that the two bright lines in the far-field are caused by the unique phase distribution of plasmons on the two side-walls of the silver nanowire. Combining with the sensing ability of surface plasmons to its environment, the configuration reported in this work is capable of functioning as a sensing platform to monitor environmental changes in the near-field region of this ultrathin nanowire.
Highlights
Surface plasmons (SPs) can confine light into subwavelength spatial dimensions, which makes them promising for use in nanophotonic devices [1, 2]
Our previous work demonstrated ultrathin Ag NWs (90 nm) placed on a photonic band gap (PBG) structure could have a plasmonic leaky mode with the plasmons propagating along the two side-walls of the Ag NWs [14]
If an ultrathin Ag NW is placed on a glass substrate, the plasmonic leaky mode disappears and the SPs cannot propagate along the two side-walls of this Ag NW for light in the visible regime due to the electric field mostly dissipating into the glass substrate [17]
Summary
Surface plasmons (SPs) can confine light into subwavelength spatial dimensions, which makes them promising for use in nanophotonic devices [1, 2]. The electric field localized at the two side-walls of Ag NWs is a leaky mode, which can couple to photons in the substrate and be directly imaged in the far-field. Our previous work demonstrated ultrathin Ag NWs (90 nm) placed on a photonic band gap (PBG) structure could have a plasmonic leaky mode with the plasmons propagating along the two side-walls of the Ag NWs [14]. Their distance in the near-field is far below the diffraction limit, two bright lines were observed at the image plane in the far-field by a standard wide-field optical microscope. Because of the sensitivity of plasmonic field to the local environment, this configuration can work as a sensing platform to monitor the environmental changes in the near-field region of ultrathin Ag NWs
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