Abstract
We report theoretical calculations of the mode fields of high index lead silicate and silicon nano fibers, and show that their strong longitudinal component enables efficient excitation of surface plasmons within a silver nanorod placed at the fiber tip. An excitation efficiency 1600 times higher than that of the standard single mode fibers has been achieved using a 350nm diameter silicon fiber at 1.1μm wavelength, while a factor of 640 times higher efficiency is achieved for a 400nm diameter lead silicate F2 glass fiber. The strong localized field emerging from the end of the rod serves as a nano-scale source with adjustable beam width, and such sources offer a new approach to high-resolution microscopy, particle manipulation and sensing.
Highlights
When a metallic tip is exposed to an electromagnetic wave, the collective oscillating electrons known as surface plasmon polaritons (SPPs) lead to electric and magnetic fields that are confined to the metallic surface
The metal tips are usually mounted to a metal-coated optical fiber probe on a shear-force-based scanning probe microscopy (SPM) for easy control of the position of the tip [1,4]
It has recently been recognised that the modes that propagate in the high index nanowires, or nanoscale core fibers, have significant electric field polarized along the propagation direction [11], and here we propose that this electric field can be used to excite SPPs of a metal particle located at the tip apex
Summary
When a metallic tip is exposed to an electromagnetic wave, the collective oscillating electrons known as surface plasmon polaritons (SPPs) lead to electric and magnetic fields that are confined to the metallic surface. Non-transparent samples can be studied via side illumination by a single mode fiber (SMF) that delivers transverse polarized light This transversely polarized light, delivered orthogonally to the tip, enables efficient excitation of SPPs at the tip apex of the metal particle attached to the fiber probe [9]. It has recently been recognised that the modes that propagate in the high index nanowires, or nanoscale core fibers, have significant electric field polarized along the propagation direction (the longitudinal direction) [11], and here we propose that this electric field can be used to excite SPPs of a metal particle located at the tip apex. The excitation of the SPPs at the end of the silver nanorods by the longitudinal field of these nanofibers is explored numerically
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