Abstract
Light confinement to sub-wavelength spot sizes is proposed and realized in tapered optical fibers. To achieve high transmission efficiencies, light propagating along the taper is combined with the excitation of surface plasmon polaritons (SPP) at its tip.
Highlights
Light confinement is limited by diffraction and the ultimate spot size _x is related to of the vacuum wavelength λ0 and to the refractive index n of the medium where light propagates[1]: In classical optics, sub-wavelength confinement has been achieved by using two highrefractive index slabs separated by a sub-wavelength gap in air [2]
Since the field in the gap is the evanescent tail of the mode in the high refractive index medium, a considerable fraction of the power is located outside the gap
Au has been deposited on the sample to generate and confine surface plasmon polaritons (SPP), it has a beneficial effect on the focused ion beam (FIB) milling: the conductive gold layer avoids the charge accumulation on the sample which can deflect the ion beam and considerably deteriorate the overall resolution
Summary
Light confinement is limited by diffraction and the ultimate spot size _x is related to of the vacuum wavelength λ0 and to the refractive index n of the medium where light propagates[1]: In classical optics, sub-wavelength confinement has been achieved by using two highrefractive index slabs separated by a sub-wavelength gap in air [2]. Optical fiber tapers confine adiabatically light to the diffraction limit and provide an extremely regular field distribution within a relatively small area. The taper tip is nanostructured to efficiently excite SPP and confine light to sub-wavelength dimensions.
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