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T. Umakoshi and P. Verma
shape and size of plasmonic materials to tune the plasmon resonance wavelength
depending on experimental requirements. In this sense, once a tapered plasmonic
structure is fabricated, any wavelengths of light can be used with the same structure. Furthermore, multiple wavelengths can be applied at the same time to the same
tapered structure, which enables the generation of a broadband near-field light [83].
The generation of broadband near-field light confined at the tip apex was experimentally demonstrated through the process of plasmon nanofocusing on a fabricated
taped silver structure, where entire visible range of light was confined at the apex at
the same time through broadband plasmon nanofocusing (Fig. 13) [84]. Further, tipenhanced CARS imaging was also demonstrated through plasmon nanofocusing,
in which multiple wavelengths are involved for CARS process with a broadband
femto-second pulsed laser [85].
Fig. 12 a Schematic of plasmon nanofocusing excited on a tapered metallic structure. b Schematic
of excitation of LSPR and near-field light in the case of the normal TERS configuration. Direct
illumination of the incident light to the apex creates background scattering.
Fig. 13 a SEM image of a tapered silver structure with a single slit as the plasmon coupler,
fabricated on a cantilever tip. b Optical images of broadband plasmon nanofocusing, observed
through several band-pass filters at different wavelengths. Reproduced from Ref. [81] in accordance
with the Creative Commons Attribution (CC BY) license
T. Umakoshi and P. Verma
shape and size of plasmonic materials to tune the plasmon resonance wavelength
depending on experimental requirements. In this sense, once a tapered plasmonic
structure is fabricated, any wavelengths of light can be used with the same structure. Furthermore, multiple wavelengths can be applied at the same time to the same
tapered structure, which enables the generation of a broadband near-field light [83].
The generation of broadband near-field light confined at the tip apex was experimentally demonstrated through the process of plasmon nanofocusing on a fabricated
taped silver structure, where entire visible range of light was confined at the apex at
the same time through broadband plasmon nanofocusing (Fig. 13) [84]. Further, tipenhanced CARS imaging was also demonstrated through plasmon nanofocusing,
in which multiple wavelengths are involved for CARS process with a broadband
femto-second pulsed laser [85].
Fig. 12 a Schematic of plasmon nanofocusing excited on a tapered metallic structure. b Schematic
of excitation of LSPR and near-field light in the case of the normal TERS configuration. Direct
illumination of the incident light to the apex creates background scattering.
Fig. 13 a SEM image of a tapered silver structure with a single slit as the plasmon coupler,
fabricated on a cantilever tip. b Optical images of broadband plasmon nanofocusing, observed
through several band-pass filters at different wavelengths. Reproduced from Ref. [81] in accordance
with the Creative Commons Attribution (CC BY) license