Abstract
Near-field localization by ultrashort femtosecond light pulses has been investigated using simple geometrical nanoapertures. The apertures employ circular, rhombic, and triangular shapes to localize the distribution of surface plasmon. To understand the geometrical effect on the localization, aperture length and period of the nanoapertures were varied. Aperture length was shown to affect the performance more than aperture period due mainly to intra-aperture coupling of near-fields. Triangular apertures provided the strongest spatial localization below 10 nm in size as well as the highest enhancement of field intensity by more than 7000 times compared to the incident light pulse. Use of ultrashort pulses was found to allow much stronger light localization than with continuous-wave light. The results can be used for super-localization sensing and imaging applications where spatially localized fields can break through the limits in achieving improved sensitivity and resolution.
Highlights
Near-field localization by ultrashort femtosecond light pulses has been investigated using simple geometrical nanoapertures
Field localization by pulsed light has been studied for applications that require very high light power that cannot be produced with continuous wave
The calculation was performed by varying light wavelengths and geometrical parameters such as period and size which can affect localized near-fields produced on the nanostructures
Summary
Near-field localization by ultrashort femtosecond light pulses has been investigated using simple geometrical nanoapertures. The localization proved to be useful for various biosensing applications such as surface-enhanced Raman spectroscopy[16] and SP resonance (SPR) biosensors in which colocalization of light fields and target molecular interactions can improve detection sensitivity significantly[17,18,19,20,21] All these approaches are limited to continuous wave operation of light source. Field localization by pulsed light has been studied for applications that require very high light power that cannot be produced with continuous wave Such a study employed tip-enhanced photoemission[22,23,24,25] and was conducted on 1D grating[26,27] and random structures[28], while ultrashort SP polariton (SPP) pulses have been observed on a 2D array of circular nanoholes[29]. Even for the nanostructures that we consider, emphasis has been placed upon the ‘simple’ nature from the perspective of implementation, i.e., aperture designs that may be mass-produced while exhibiting strongly localized field have been sought
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