Tapered nanofiber trapping of high-refractive-index nanoparticles

Swaim, Jon D.; Knittel, Joachim; Bowen, Warwick P.

doi:10.1063/1.4829659

Cited by 15 publications

(14 citation statements)

References 24 publications

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“…3f (Supplementary Information VI). Unlike previous experiments 14,15 which used a combination of repulsive electrostatic forces and attractive optical forces to trap larger particle near the nanofibre, we demonstrate theoretically and experimentally that optical attraction is negligible for our smaller particles (Supplementary Information VIII).…”

Section: Detection and Trapping Of Single Nanoparticlesmentioning

confidence: 78%

“…6 Probability distribution and trapping potential calculations When a particle is scattering probe light close to the nanofibre more light will be collected than when the particle is further from the fibre, thereby modulating the amplitude of the recorded signal field. This relation between the particle position and the amplitude of the signal has the same shape as the optical field and decays approximately exponentially following the relation r = −k −1 log( n det ) where r is the position of the particle relative to the fibre , k = 2πn m /λ is the wave number, and λ = 780nm is the wavelength of the light 14 . The position of the nanoparticle can then be calculated from the amplitude relative to the position with the highest amplitude.…”

Section: Power Spectral Density Of Trapped Particlesmentioning

confidence: 99%

“…In conventional nanofibre traps, a combination of attractive optical gradient force and repulsive electrostatic forces are used together to trap the particle next to the fibre 14 . Similar to optical tweezers, particles diffusing in the evanescent field around the fibre will be polarised and then attracted toward the centre of the fibre following the gradient of the light intensity.…”

Section: Attractive Forcesmentioning

confidence: 99%

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Evanescent single-molecule biosensing with quantum-limited precision

et al. 2017

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Sensors that are able to detect and track single unlabelled biomolecules are an important tool both to understand biomolecular dynamics and interactions at nanoscale, and for medical diagnostics operating at their ultimate detection limits. Recently, exceptional sensitivity has been achieved using the strongly enhanced evanescent fields provided by optical microcavities and nano-sized plasmonic resonators. However, at high field intensities photodamage to the biological specimen becomes increasingly problematic. Here, we introduce an optical nanofibre based evanescent biosensor that operates at the fundamental precision limit introduced by quantisation of light. This allows a four order-of-magnitude reduction in optical intensity whilst maintaining state-of-the-art sensitivity. It enables quantum noise limited tracking of single biomolecules as small as 3.5 nm, and surface-molecule interactions to be monitored over extended periods. By achieving quantum noise limited precision, our approach provides a pathway towards quantum-enhanced single-molecule biosensors. IntroductionEvanescent optical biosensors that operate label-free and can resolve single molecules have applications ranging from clinical diagnostics 1 , to environmental monitoring 2, 3 and the detection and manipulation of viruses 4 , proteins and antibodies [5][6][7] . Further, they offer the prospect to provide new insights into motor molecule dynamics and biophysically important conformational changes as they occur in the natural state, unmodified by the presence of fluorescent markers or nanoparticle labels 5 . Recently, the reach of evanescent techniques has been extended to single proteins with Stokes radii of a few nanometers 1,6 by concentrating the optical field using resonant structures such as optical microcavities 2, 4, 5 and plasmonic resonators 1,6,7 . These advances illustrate a near-universal feature of precision opti- cal biosensors -that increased light intensities are required to detect smaller molecules or improve spatiotemporal resolution. This increases the photodamage experienced by the specimen, which can have broad consequences on viability 8 , function 9 , structure 10 and growth 11 . It is therefore desirable to develop alternative biosensing approaches that improve sensitivity without exposing the specimen to higher optical intensities.Here we demonstrate an optical nanofibre-based approach to evanescent detection and tracking of unlabelled biomolecules that utilises a combination of heterodyne interferometry and dark field illumination. This greatly suppresses technical noise due to background scatter, vibrations and laser fluctuations that has limited previous experiments 12,13 , allowing operation at the quantum noise limit to sensitivity introduced by the quantisation of light. The increased information that is extracted per scattered photon enables state-of-the-art sensitivity to be achieved with optical intensities four orders of magnitude lower than has been possible previously 1,6 . Using the biosensor, we detect nan...

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Section: Detection and Trapping Of Single Nanoparticlesmentioning

confidence: 78%

Section: Power Spectral Density Of Trapped Particlesmentioning

confidence: 99%

Section: Attractive Forcesmentioning

confidence: 99%

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Evanescent single-molecule biosensing with quantum-limited precision

et al. 2017

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“…In recent years, so-called tapered optical fibers (TOFs) have received growing attention [3], both as optical components, e.g., for coupling light into microand nano-optical components, for sensing, as well as for the controlled coupling of light and matter at or near the TOF surface [4][5][6][7]. Beyond their optical properties, which have been extensively studied in the past, it is important to understand and control the mechanical properties of these devices for many of these applications.…”

mentioning

confidence: 99%

Experimental stress–strain analysis of tapered silica optical fibers with nanofiber waist

Holleis

Hoinkes

Wuttke

et al. 2014

Applied Physics Letters

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We experimentally determine tensile force-elongation diagrams of tapered optical fibers with a nanofiber waist. The tapered optical fibers are produced from standard silica optical fibers using a heat and pull process. Both, the force-elongation data and scanning electron microscope images of the rupture points indicate a brittle material. Despite the small waist radii of only a few hundred nanometers, our experimental data can be fully explained by a nonlinear stress-strain model that relies on material properties of macroscopic silica optical fibers. This is an important asset when it comes to designing miniaturized optical elements as one can rely on the well-founded material characteristics of standard optical fibers. Based on this understanding, we demonstrate a simple and non-destructive technique that allows us to determine the waist radius of the tapered optical fiber. We find excellent agreement with independent scanning electron microscope measurements of the waist radius.Glass fibers are among the most versatile inventions of the last century with applications reaching from fiberreinforced materials as used in construction [1] to optical data transmission in global telecommunication networks [2]. In recent years, so-called tapered optical fibers (TOFs) have received growing attention [3], both as optical components, e.g., for coupling light into microand nano-optical components, for sensing, as well as for the controlled coupling of light and matter at or near the TOF surface [4][5][6][7]. Beyond their optical properties, which have been extensively studied in the past, it is important to understand and control the mechanical properties of these devices for many of these applications.Here, we study the mechanical response of silica TOFs with a nanofiber waist when exposed to tensile stress. Qualitatively, we observe a brittle stress-strain behavior and no constriction of the two fiber ends when the fiber has been ruptured apart. Previous studies on the mechanical properties of such ultra-thin silica structures are divided over the importance of size effects in the nanoscopic domain, e.g., suggesting a decrease or an increase of Young's modulus compared to bulk values [8][9][10][11]. In our study, even for the smallest investigated waist radius of only 160 nm, the recorded stress-strain diagrams match those of macroscopic optical fibers [12][13][14]. As a consequence, in the parameter range considered here, it is justified to assume the well-studied mechanical properties of standard optical fibers when designing nano-optical elements. Based on this understanding, we provide a practical, non-destructive in-situ method to determine the TOF waist radius. The results obtained in this way are in very good agreement with independent radius measurements using a scanning electron microscope.The TOFs we study in our experiments are produced from commercial optical fibers (SM800, Fibercore) using a heat and pull process [15,16]. A schematic of such a cylindrically symmetric TOF is shown in Fig. 1(a). The TOF con...

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“…Based on the microfiber structure, both active and passive devices have been proposed and demonstrated, such as lasers [13], sensors [14], resonators [15] and optical tweezers [16]. In addition the increased mode field diameter in the tapered region can result in the extinction of the fuse effect and shows significant potential for the optical network to protect the active equipment from damage caused by the fuse effect [17].…”

Section: Introductionmentioning

confidence: 99%

Optical microfiber-loaded surface plasmonic TE-pass polarizer

Farrell

Semenova

et al. 2016

Optics & Laser Technology

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Abstract:We propose a novel optical microfiber-loaded plasmonic TE-pass polarizer consisting of an optical microfiber placed on top of a silver substrate and demonstrate its performance both numerically by using the finite element method (FEM) and experimentally. The simulation results show that the loss in the fundamental TE mode is relatively low while at the same time the fundamental TM mode suffers from a large metal dissipation loss induced by excitation of the microfiberloaded surface plasmonic mode. The microfiber was fabricated using the standard microheater brushing-tapering technique. The measured extinction ratio over the range of the C-band wavelengths is greater than 20 dB for the polarizer with a microfiber diameter of 4 µm, which agrees well with the simulation results.

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Tapered nanofiber trapping of high-refractive-index nanoparticles

Cited by 15 publications

References 24 publications

Evanescent single-molecule biosensing with quantum-limited precision

Evanescent single-molecule biosensing with quantum-limited precision

Experimental stress–strain analysis of tapered silica optical fibers with nanofiber waist

Optical microfiber-loaded surface plasmonic TE-pass polarizer

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