Remote optical sensing on the nanometer scale with a bowtie aperture nano-antenna on a fiber tip of scanning near-field optical microscopy

Abstract

Plasmonic nano-antennas have proven the outstanding ability of sensing chemical and physical processes down to the nanometer scale. Sensing is usually achieved within the highly confined optical fields generated resonantly by the nano-antennas, i.e. in contact to the nanostructures. In this paper, we demonstrate the sensing capability of nano-antennas to their larger scale environment, well beyond their plasmonic confinement volume, leading to the concept of "remote" (non contact) sensing on the nanometer scale. On the basis of a bowtie-aperture nano-antenna (BNA) integrated at the apex of a SNOM fiber tip, we introduce an ultra-compact, moveable and background-free optical nanosensor for the remote sensing of a silicon surface (up to distance of 300 nm). Sensitivity of the BNA to its large scale environment is high enough to expect the monitoring and control of the spacing between the nano-antenna and a silicon surface with sub-nanometer accuracy. This work paves the way towards a new class of nanopositionning technique, based on nano-antenna resonance monitoring, that are alternative to nanomechanical and optical interference-based devices.

Tunable potential well for plasmonic trapping of metallic particles by bowtie nano-apertures

“…S2 on line shows the different groups of wavelength dependent potential well depth with difference bowtie nano-aperture sizes. Incident wavelength for deepest potential well evidently increases when enlarging the aperture size, which accords to the previous works 20 .…”

“…It has been proved by the previous work that the great localized and enhanced e-field exists in the center of bowtie dimmers, enabling to generate enough e-field gradients to trap nanoparticles within nanoscales. The plasmon resonance modes in metallic nano-apertures, proved as Fabry-Pérot-like interfering of TE 10 mode propagation wave, strongly depend on the aperture geometry 20 . Through modifying apertures sizes or shapes, the wavelength for plasmonic trapping can be flexibly tuned.…”

“…In this paper, the plasmonic trapping forces and the shape of the trapping potential wells depending on the wavelength of incident beams are investigated based on the finite element method (FEM). Bowtie nanoaperture, an effective structure for plasmonic trapping proved by previous works 19 20 , is applied to trap metallic nanoparticles within nanoscales. Prominent tunabilities of potential well, such as depth, width and stiffness at potential well bottom, were checked.…”

Optical Manipulation of nanoparticles by simultaneous electric and magnetic field enhancement within diabolo nanoantenna

“…5 and show that the resonance properties (both resonance wavelength and enhancement factors) of the DA are affected by the presence of the substrate. This phenomenon was already pointed out for another kind of nano-antennas, such as a bowtie nano-antenna 11 or the bowtie nano-aperture antenna ( BNA ) for which the resonance properties were examined as a function of the antenna-to-substrate distance 24 , 25 . In the latter cases, a shift as large as Δ λ = 500 nm of the resonance wavelength of a BNA occurs when the latter moves up over 10 nm from the substrate interface.…”

Recent Developments in Micro-Structured Fiber Optic Sensors

“…3D optical trapping of 0.5 µ m latex beads was successfully conducted, which demonstrates that the device has promising applications such as biological and chemical probing and trapping. Similar structures could be found in several following works [216,217]. To overcome the fragility of the fiber taper-based optical trapping devices, a more robust structure was proposed by Gordon et al by engraving double nanohole aperture at the cleaved fiber end through FIB milling as shown in Figure 15c [218].…”