Enhanced optical near field from a bowtie aperture

Jin, Eric X.; Xu, Xianfan

doi:10.1063/1.2194013

Cited by 116 publications

(83 citation statements)

References 23 publications

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“…Nanoscale apertures in thin noble-metal films, with dimensions comparable to the light wavelength, can form plasmonic nano-resonators (PNRs) and such structures can concentrate an incident light field into a small volume which overcomes the diffraction limit with orders-of-magnitude intensity enhancement. So far, the transmission properties of plasmonic slot nano-resonators (PSNRs) have been studied under plane-wave excitation directed perpendicularly to the plane of the resonator [1,2].In this paper, we theoretically study a strongly-coupled 3D PSNR by embedding a slot nano-cavity in a plasmonic cylindrical waveguide formed by a thin-gold-film coated microfiber using 3D Finite Element Method. Light is launched from one end of the microfiber with 1 µm diameter and 30 nm gold layer and the various resonances can be identified simply monitoring the transmitted and reflected light.…”

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Plasmonic slot nano-resonators in gold-coated microfibers

Ding

Brambilla

Zervas

2013

2013 Conference on Lasers &Amp; Electro-Optics Europe &Amp; International Quantum Electronics Conference CLEO EUROPE/IQEC

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In recent years, research in plasmonics and related devices has attracted considerable interest. Nanoscale apertures in thin noble-metal films, with dimensions comparable to the light wavelength, can form plasmonic nano-resonators (PNRs) and such structures can concentrate an incident light field into a small volume which overcomes the diffraction limit with orders-of-magnitude intensity enhancement. So far, the transmission properties of plasmonic slot nano-resonators (PSNRs) have been studied under plane-wave excitation directed perpendicularly to the plane of the resonator [1,2].In this paper, we theoretically study a strongly-coupled 3D PSNR by embedding a slot nano-cavity in a plasmonic cylindrical waveguide formed by a thin-gold-film coated microfiber using 3D Finite Element Method. Light is launched from one end of the microfiber with 1 µm diameter and 30 nm gold layer and the various resonances can be identified simply monitoring the transmitted and reflected light. Fig. 1 (a) shows the top-view of the bow-tie nano-cavity and Fig. 1 (b) shows the transmissivity and the reflectivity of the composite structure with the bow-tie PSNR geometry with L=400 nm, D=200 nm, and d=34.4 nm. Three main resonances were identified: the resonance at λ=880 nm corresponds to a second-order resonance, with two intensity maxima along the length of the bow-tie PSNR. The resonances at λ= 1524 nm and 2050 nm correspond to first-order PSNR resonances, with only one intensity maximum along the bow-tie length. Fig. 1 (c) shows the total electric field modulus at several wavelengths corresponding to the major (λ=880 nm, 1524 nm and 2050 nm) resonances, at which the electric field is highly localized and centered at the bow-tie waist. Shown are also some minor (λ=820 nm, 970 nm, 1040 nm, 1170 nm and 1260 nm) resonances, whose corresponding electric field distributions are gradually shifting off-center and their peak values decrease. Different bow-tie PSNRs with different waist and different edge width, multiple cascaded bow-tie PSNR, and rectangular PSNR were numerically investigated. A single resonator shows enhancement factor in excess of 9×10 5 , which we believe is the biggest enhancement factor calculated in all types of nano-resonators so far. Wavelength shift rates were found to be strongly dependent on the nature of the associated resonance and the plasmonic waveguide characteristics. It was observed that resonances lying closer to the plasmonic waveguide fundamental mode cut-off are much more sensitive on the PSNR dimensions. In addition to higher wavelengthshift sensitivities, the longer-wavelength resonances showed also the largest intensity enhancement factors. Using multiple cascaded PSNR structures results in even higher intensity enhancement factors (in excess of one million) in multiple spots. The combination of these features implies that designs that are based on longerwavelength resonances are the most promising candidates for advanced applications such as SERS, optical filtering, spectroscopy and bio-sensing.

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Plasmonic slot nano-resonators in gold-coated microfibers

Ding

Brambilla

Zervas

2013

2013 Conference on Lasers &Amp; Electro-Optics Europe &Amp; International Quantum Electronics Conference CLEO EUROPE/IQEC

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“…The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.The double-nanohole structure has been shown to give a strong local field enhancement 5,6 . Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force.…”

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“…The double-nanohole structure has been shown to give a strong local field enhancement 5,6 . Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force.…”

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Optical Trapping of Nanoparticles

Bergeron

Zehtabi-Oskuie

Ghaffari

et al. 2013

JoVE

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Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam 1 . The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles 1 . In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec 1 , which has serious implications for biological matter 2,3 .A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime 4 . In a nonperturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.The double-nanohole structure has been shown to give a strong local field enhancement 5,6 . Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres 7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins 8 . In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres. Video LinkThe video component of this article can be found at https://www.jove.com/video/4424/ ProtocolThe principle of the SIBA trapping technique is illustrated in Figure 1. Figure 2 is a schematic of the experimental setup.

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“…[6][7][8] Earlier studies have been focused on bowtie optical antennas with different shapes of metal patches and apertures. [9][10][11][12][13][14][15][16][17][18][19][20] Recently, rectangular metal bar optical antenna arrays have been investigated due to the easy tuning of the resonance wavelength and near-field spatial distributions through modifying antenna bar length, array period, and substrate. [21][22][23][24][25][26][27] A diabolo antenna is a variation of a rectangular metal bar antenna with reduced waist width.…”

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Resonance spectra of diabolo optical antenna arrays

et al. 2015

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A complete set of diabolo optical antenna arrays with different waist widths and periods was fabricated on a sapphire substrate by using a standard e-beam lithography and lift-off process. Fabricated diabolo optical antenna arrays were characterized by measuring the transmittance and reflectance with a microscope-coupled FTIR spectrometer. It was found experimentally that reducing the waist width significantly shifts the resonance to longer wavelength and narrowing the waist of the antennas is more effective than increasing the period of the array for tuning the resonance wavelength. Also it is found that the magnetic field enhancement near the antenna waist is correlated to the shift of the resonance wavelength.

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Enhanced optical near field from a bowtie aperture

Cited by 116 publications

References 23 publications

Plasmonic slot nano-resonators in gold-coated microfibers

Plasmonic slot nano-resonators in gold-coated microfibers

Optical Trapping of Nanoparticles

Resonance spectra of diabolo optical antenna arrays

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