Time-resolved imaging of near-fields in THz antennas and direct quantitative measurement of field enhancements

Werley, Christopher A.; Fan, Kebin; Strikwerda, Andrew C.; Teo, Stephanie M.; Zhang, Xin; Averitt, R. D.; Nelson, Keith A.

doi:10.1364/oe.20.008551

Cited by 53 publications

(43 citation statements)

References 36 publications

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“…The spatial selectivity was achieved by attaching the sample under test to a metallic screen with a sub-wavelength aperture (as small as 10 lm) 15 or by placing the sample on an electro-optic crystal directly. 16,17 The spatial resolution in the latter case is of the order of several tens of lm, determined by the electro-optics crystal thickness. 16,17 Here we investigate the interaction of Z-TSWs with sub-wavelength size dielectric particles placed between a THz planar antenna and a metallic plane.…”

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confidence: 99%

“…16,17 The spatial resolution in the latter case is of the order of several tens of lm, determined by the electro-optics crystal thickness. 16,17 Here we investigate the interaction of Z-TSWs with sub-wavelength size dielectric particles placed between a THz planar antenna and a metallic plane. We demonstrate that near-field mapping of the surface field enables direct detection of the particles.…”

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confidence: 99%

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Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Navarro‐Cía

Natrella

Dominec

et al. 2013

Applied Physics Letters

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Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations.

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confidence: 99%

mentioning

confidence: 99%

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Navarro‐Cía

Natrella

Dominec

et al. 2013

Applied Physics Letters

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“…To study the effects in the strong-field limit, the strength of the terahertz field can be locally enhanced exploiting near-field effects in meta-materials [3,[15][16][17][18][19][20], which typically consist of micrometer-sized metallic structures deposited on the sample surface. However, since the area of the sample is often significantly smaller than the area of metallic structures in meta-materials, the reflectivity in the visible or near-infrared frequency range of the probe is dominated by the latter.…”

Section: Introductionmentioning

confidence: 99%

Anti-reflection coating design for metallic terahertz meta-materials

Pancaldi¹,

Freeman²,

Heinrich³

et al. 2018

Opt. Express

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Abstract:We demonstrate a silicon-based, single-layer anti-reflection coating that suppresses the reflectivity of metals at near-infrared frequencies, enabling optical probing of nano-scale structures embedded in highly reflective surroundings. Our design does not affect the interaction of terahertz radiation with metallic structures that can be used to achieve terahertz near-field enhancement. We have verified the functionality of the design by calculating and measuring the reflectivity of both infrared and terahertz radiation from a silicon/gold double layer as a function of the silicon thickness. We have also fabricated the unit cell of a terahertz meta-material, a dipole antenna comprising two 20-nm thick extended gold plates separated by a 2 µm gap, where the terahertz field is locally enhanced. We used the time-domain finite element method to demonstrate that such near-field enhancement is preserved in the presence of the anti-reflection coating. Finally, we performed magneto-optical Kerr effect measurements on a single 3-nm thick, 1-µm wide magnetic wire placed in the gap of such a dipole antenna. The wire only occupies 2% of the area probed by the laser beam, but its magneto-optical response can be clearly detected. Our design paves the way for ultrafast time-resolved studies, using table-top femtosecond near-infrared lasers, of dynamics in nano-structures driven by strong terahertz radiation.

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“…The relation between the near-field response of a structure and its far-field spectrum has been the subject of several studies that have consistently reported a small yet distinct shift between the near-and far-field resonant frequencies [16][17][18][19][20]. The origin of this shift is ascribed to the intrinsic damping of the structure and has been modeled using the damped-driven oscillator model [19].…”

Section: Introductionmentioning

confidence: 99%

Large near-to-far field spectral shifts for terahertz resonances

et al. 2016

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We have performed far-field extinction measurements and near electric field measurements on gold bowtie antennas resonant at THz frequencies. These measurements show a very large shift between the resonant frequencies of the near-field and the far-field spectra. We use the established damped-driven harmonic oscillator model for resonators to model the far-field response of the antennas from the near-field spectrum and show that there is a large discrepancy between the predicted and measured far-field response. We were able to explain this discrepancy by improving the oscillator model with a Fano model. This large shift makes the prediction of the near-field response of resonant structures at THz frequencies very imprecise, provided that only information of the far-field response is available and establishes the necessity of measuring near fields for a correct and accurate characterization of these structures.

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Time-resolved imaging of near-fields in THz antennas and direct quantitative measurement of field enhancements

Cited by 53 publications

References 36 publications

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Anti-reflection coating design for metallic terahertz meta-materials

Large near-to-far field spectral shifts for terahertz resonances

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