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Intensity of the electric field in a tapered silica optical fiber, radius 500 nm, optical wavelength l 0 ¼ 1064 nm for the quasi-linearly polarized HE 11
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We investigate the manipulation of microscopic and nanoscopic particles using the evanescent optical field surrounding an optical fiber that is tapered to a micron-scale diameter, and propose that this scheme could be used to discriminate between, and thereby sort, metallic nanoparticles. First we show experimentally the concept of the transport of...
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... is imaginary, implying a rapidly decaying evanescent field. As an example we show in Fig. 3 the field distri- butions for a silica glass tapered fiber with parameters approximately those of the experiment in Section 2.2. The fiber is surrounded by water and has diameter a ¼ 1:0 mm, and is supporting a quasi-linearly (xÀ) polarized HE 11 mode. The normalized frequency of this tapered ...
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... the HE 11 mode initially polarized in the x-direction the dominant component remains the x-polarized field, shown in Fig. 3(a) but the amplitudes of the electric fields in the y-and z-directions become significant for large refractive index differences between the silica fiber and its surroundings (large fiber numerical aperture), shown in Fig. 3(b) and (c). Similar cross-polarized components are also observed in the case of high numerical aperture ...
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... the HE 11 mode initially polarized in the x-direction the dominant component remains the x-polarized field, shown in Fig. 3(a) but the amplitudes of the electric fields in the y-and z-directions become significant for large refractive index differences between the silica fiber and its surroundings (large fiber numerical aperture), shown in Fig. 3(b) and (c). Similar cross-polarized components are also observed in the case of high numerical aperture focusing, e.g. by a microscope objective lens [26]. Furthermore, the conditions for continuity of electric field components normal and tangential to the boundary lead to an enhancement of the evanescent electric mode; (a) field in ...
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... to the boundary lead to an enhancement of the evanescent electric mode; (a) field in the x-(dominant polarization) direction; (b) field in the y-(orthogonal transverse) direction; (c) field in the z-(propagation) direction; (d) total field. field along the x-axis, resulting in a net field distribution with pronounced lobes along 7 x, shown in Fig. 3(d). The evanescent field of this mode penetrates a significant dis- tance into the surroundings. For these exemplar parameters we calculate a penetration depth L ¼ ...
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Citations
... Optical nanofibers quickly became a new manipulation tool for particles [14,65]. However, for any in-depth study on particle dynamics, it is important to precisely control the position of the particle relative to the ONF. ...
Optical trapping has proven to be an efficient method to control particles, including biological cells, single biological macromolecules, colloidal microparticles, and nanoparticles. Multiple types of particles have been successfully trapped, leading to various applications of optical tweezers ranging from biomedical through physics to material sciences. However, precise manipulation of particles with complex composition or of sizes down to nanometer-scales can be difficult with conventional optical tweezers, and an alternative manipulation tool is desirable. Optical nanofibers, that is, fibers with a waist diameter smaller than the propagating wavelength of light, are ideal candidates for optical manipulation due to their large evanescent field that extends beyond the fiber surface. They have the added advantages of being easily connected to a fibered experimental setup, being simple to fabricate, and providing strong electric field confinement and intense magnitude of evanescent fields at the nanofiber’s surface. Many different particles have been trapped, rotated, transported, and assembled with such a system. This article reviews particle trapping using optical nanofibers and highlights some challenges and future potentials of this developing topic.
... Because the particle size is greater than the laser wavelength (d > ), this condition can be classified as the Mie scattering. The rationale is that Au-NP SPF can trap and manipulate microparticles owing to the optical gradient (F gr ) and scattering forces (F sc ) on metallic nanoparticles, revealing that these forces are enhanced at a trapping wavelength in the region of the nanoparticle surface plasmon polariton (SPP) [25] . ...
This study demonstrates a method for microparticle optical trapping of silica gel using a stable Q-switched fiber laser (QFL) pulse. Gold nanoparticle (Au-NP) were fabricated as saturable absorbers on a side-polished optical fiber (SPF) to achieve stable QFL pulses of frequencies 25.81 kHz. Silica gel microparticles with a radius of 300-400 μm produced a dissimilar attractive trapping force based on the viscous drag exerted on the light field of the QFL. Shifts were observed at wavelengths of 1533.8-1541.0 nm and frequencies of 25.81-28.87 kHz. The validity of the numerical model is proven and the proposed model can be applied to examine the behavior of surface plasmon polaritons (SPP) modes in microparticle optical trapping. These findings confirm that the proposed system facilitates absorption microparticle trapping at the 1540 nm wavelength region.
... On the other hand, solid state quantum emitters in nanocrystals are often utilised in colloidal form. The manipulation of nano-sized particles in liquid environments using immsersed nanowaveguides is proceeding apace from its initial foundations [7,8], with a number of advances in selectivity [9][10][11], use of higher order modes and particle binding [12,13], angular momentum [14], and manipulation of novel particles [10,15] achieved in the past few years. In particular, the potential for counterpropagating modes to halt particles moving along a waveguide has been noted before [9,16], although only in the context of creating a region where no axial force is present. ...
We investigate numerically and experimentally the properties of a two color optical fiber taper trap, for which the evanescent field of the modes in the fiber taper give rise to a three-dimensional trapping potential. Experimentally, we use the technique to confine colloidal nanoparticles near the surface of an optical fiber taper, and show that the trapping position of the particles is adjustable by controlling the relative power of two modes in the fiber. We also demonstrate a proof of principle application by trapping quantum dots together with gold nanoparticles in a configuration where the trapping fields double as the excitation field for the quantum dots. This scheme will allow the positioning of quantum emitters in order to adjust coupling to resonators combined with the fiber taper.
... As a result, this evanescent field has little or no contact with the material that surrounds the cladding. To address this, claddingfree optical fiber and tapered optical fiber [78][79][80][81][82] have been introduced for sensing applications, and they can be extremely sensitive to the index change of the analyte in the surrounding medium. However, due to its low mechanical strength and figures of merits, the utilization of cladding removed optical fiber suffers. ...
This paper introduces a review of the use of gold nanoparticles (AuNPs) in the fabrication of optical fiber biosensors based on localized surface Plasmon resonance (LSPR) and Evanescent field absorption. The AuNPs have special properties, such as high surface/volume ratio, and intense light scattering/absorption, and stable structure. The main advantage of AuNPs in the application of the biosensor in the detection signal increasing, for especially low concentration analyses. Moreover, we illustrate some of the previous works in this field in the period from 2001-2021, which used optical fiber and AuNPs as a base in the development of various biosensors and all exhibited differently limits of detection, sensitivity, and good performances to its target detection.
... One aspect of optical manipulation showing promise in this area is the use of counterpropagating optical fields, which allows sophisticated particle control including optical pulling type effects and the use of optical nonlinearity to achieve size sensitive optically induced forces. 15,16 On the other hand, a separate research avenue for the manipulation of nano-size particles of many types makes use of nanostructures including nanowaveguides [17][18][19][20][21] and plasmonic nanostructures. 22,23 In particular, a very recent combination of nanowaveguide techniques with the above-mentioned counter-propagating field method, has led to remarkable selective control of nanodiamonds near to an optical nanofiber conditional on the number of NV centers they contain. ...
... We refer to this trap configuration as a two color taper trap and note that it is distinct from two color trapping at constant nanofiber radius which has been extensively considered, both for atomic systems 25 and for nanoparticles. 19,26 We will calculate the potential for an explicit example below. ...
We demonstrate size selective optical trapping and transport for metal nanoparticles near a nanowaveguide. Using a two-wavelength, counter-propagating mode configuration inside an optical nanofiber, we show that 100 nm diameter and 150 nm diameter gold nanospheres (GNSs) are trapped near the nanofiber center at different optical pow- ers. Conversely, when one nanofiber species is trapped the other may be transported, leading to a sieve like effect. We find good correspondence between our experimental results and numerical simulations of the system.
... Due to their small footprint, ease of alignment, and integration with existing optical setups, trapping experiments with optical fibers are one specific platform that has seen strong progress in recent years. Different fiber configurations have been developed including tapered optical fibers [7][8][9][10][11][12], structured optical fibers [13][14][15], single fibre tips [16,17], tapered fiber tips [18][19][20][21][22], and lensed fiber tips [23,24]. ...
We demonstrate optical trapping of rare earth-doped NaYF4:Er/Yb nanorods of high aspect ratio (length 1.47 μm and diameter 140 nm) using a quasi Bessel beam (QBB) generated by positive axicon optical fiber tips. Propulsion or trapping of the nanorods is demonstrated using either single or dual fiber nano-tip geometries. The optical force exerted on the trapped nanorods, their velocities, and their positions have been analyzed. We determine the trap stiffness for a single nanorod to be 0.12 pN/μm (0.003 pN/μm) by power spectrum analysis and 0.13 pN/μm (0.015 pN/μm) by Boltzmann statistics in the direction perpendicular to (along) the fiber axes for an average optical power of 34 mW. The experiments illustrate the advantage of using a QBB for multiple nanorod trapping over a large distance of up to 30 μm.
... The use of a prism to form a condition for TIR is an alternative to other approaches associated with the use of waveguides, fluorescence technology or microspheres [19][20][21][22]. The availability of this optical element determining the simplicity of achieving the necessary conditions for total internal reflection facilitates the evanescent wave creation. ...
The idea of the proposed paper is a demonstration of the evanescent wave effect on nano-objects of inorganic and organic (in particular, formed blood elements) origin localized in a biological medium, in the direction perpendicular to the direction of the Pointing vector action. On the one hand, this opens up (illustrates) new possibilities in the optical control of the direction of motion and speed of the studied nanoobjects in a layer of biological fluid. On the other hand, the very choice of objects of this type suggests the possible prospects for their use in biology, medicine, pharmacology, and precision chemistry. So, in particular, gold nanoparticles, being non-toxic to the body, are able to penetrate through the cell biomembranes, accumulate in them, thereby contributing to the diagnosis of the cell state with subsequent optical exposure to them, up to destruction in case of cancer pathologies. The role of red blood cells (RBS) in the body is generally unique and controlling their motion contributes to the complex saturation of tissues with oxygen. The choice of just the evanescent wave is explained by the need for near-surface manipulation of optical energy flows, which is especially important in the situation of studying biological complexes and structures. Exclusive manifestation of the evanescent wave action became possible under specially selected experimental condition of evanescent wave exitation. A total internal reflection was realized at the interface between the prism and a biological medium by a linearly polarized wave with the azimuth of polarization of ±45°. The result of such an excitation mechanism was a complex distribution of the optical flow density, which is accompanied by a change in the energy density both in the longitudinal direction coinciding with the direction of the wave vector and in the transverse direction perpendicular to the wave vector. The paper summarizes the latest theoretically and experimentally obtained results illustrating the rectilinear and rotational motion of investigated objects in a biological environment.
... This transport was achieved for moderate laser powers compared to liposome trapping using conventional optical tweezer techniques, 18 with trapping and transport observed down to 6 mW optical power for the two thinnest nanofibre samples. Our results extend numerous recent studies where thin optical fibres have been used to trap and propel micro and nanoparticles 22,23 to the regime of comoposite, low index bio-nanoparticles. ...
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... Le piégeage stable et efficace des nano-particules uniques reste un défit majeur. Pour le réaliser, il est généralement nécessaire d'utiliser un faisceau laser très focalisé, en utilisant des guides d'ondes[135][136][137][138], ou des configurations de piégeages exploitant les ondesévanescentes[139][140][141][142] augmentant fortement les forces optiques mises en jeu. ...
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... On the contrary, WGMs have a significant longitudinal component; hence, their optical fields experience the anisotropy of the elasto-optic effect intrinsically. In the last years, researchers have demonstrated a number of fiber devices in which the longitudinal components of the electromagnetic modes are significant, such as microfibers [35] and microstructured optical fibers with a high air-filling fraction [36]. For these cases, the measurement and characterization of the anisotropy of the elasto-optic effect and its Pockels coefficients are of high interest. ...
