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Strong near field enhancement in THz nano-antenna arrays.

Feuillet-Palma C, Todorov Y, Vasanelli A, Sirtori C - Sci Rep (2013)

Bottom Line: In the microwave domain, for many years this task has been successfully performed by antennas, built from metals that can be considered almost perfect at these frequencies.In this work we experimentally study the light coupling properties of dense arrays of subwavelength THz antenna microcavities.This effect is quantitatively described by an analytical model that can be applied for the optimization of any nanoantenna array.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire "Matériaux et Phénomènes Quantiques", Sorbonne Paris Cité, Université Paris Diderot, CNRS-UMR 7162, FR-75013 Paris, France.

ABSTRACT
A key issue in modern photonics is the ability to concentrate light into very small volumes, thus enhancing its interaction with quantum objects of sizes much smaller than the wavelength. In the microwave domain, for many years this task has been successfully performed by antennas, built from metals that can be considered almost perfect at these frequencies. Antenna-like concepts have been recently extended into the THz and up to the visible, however metal losses increase and limit their performances. In this work we experimentally study the light coupling properties of dense arrays of subwavelength THz antenna microcavities. We demonstrate that the combination of array layout with subwavelength electromagnetic confinement allows for 10(4)-fold enhancement of the electromagnetic energy density inside the cavities, despite the low quality factor of a single element. This effect is quantitatively described by an analytical model that can be applied for the optimization of any nanoantenna array.

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Analysis of the reflectivity data.(a) The light extraction efficiencies of the samples, defined as the ratio Q/Qrad. (b) Ratio between the electromagnetic energy densities of the microcavity field and the field of the incoming plane wave. The short-dashed lines are extrapolation of the data for vanishing filling factors. The long-dashed line indicates the ratio Aeff/Σ (right axis). The shaded area corresponds to the single antenna limit, Aeff/Σ ≤ 1. In both (a) and (b) the error bars are estimated from those of C and Q reported in Fig. 3.
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f4: Analysis of the reflectivity data.(a) The light extraction efficiencies of the samples, defined as the ratio Q/Qrad. (b) Ratio between the electromagnetic energy densities of the microcavity field and the field of the incoming plane wave. The short-dashed lines are extrapolation of the data for vanishing filling factors. The long-dashed line indicates the ratio Aeff/Σ (right axis). The shaded area corresponds to the single antenna limit, Aeff/Σ ≤ 1. In both (a) and (b) the error bars are estimated from those of C and Q reported in Fig. 3.

Mentions: Having validated our theoretical model through comparison with measurements, we can now provide quantitative estimation of the parameters relevant to the emission and absorption of radiation. These parameters are the light extraction efficiency defined as Q/Qrad1, and the ratio between the energy densities of the electromagnetic field inside the microcavity and that of the incoming field (Eq.(4)). They are plotted respectively in Figures 4(a) and 4(b).


Strong near field enhancement in THz nano-antenna arrays.

Feuillet-Palma C, Todorov Y, Vasanelli A, Sirtori C - Sci Rep (2013)

Analysis of the reflectivity data.(a) The light extraction efficiencies of the samples, defined as the ratio Q/Qrad. (b) Ratio between the electromagnetic energy densities of the microcavity field and the field of the incoming plane wave. The short-dashed lines are extrapolation of the data for vanishing filling factors. The long-dashed line indicates the ratio Aeff/Σ (right axis). The shaded area corresponds to the single antenna limit, Aeff/Σ ≤ 1. In both (a) and (b) the error bars are estimated from those of C and Q reported in Fig. 3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3584925&req=5

f4: Analysis of the reflectivity data.(a) The light extraction efficiencies of the samples, defined as the ratio Q/Qrad. (b) Ratio between the electromagnetic energy densities of the microcavity field and the field of the incoming plane wave. The short-dashed lines are extrapolation of the data for vanishing filling factors. The long-dashed line indicates the ratio Aeff/Σ (right axis). The shaded area corresponds to the single antenna limit, Aeff/Σ ≤ 1. In both (a) and (b) the error bars are estimated from those of C and Q reported in Fig. 3.
Mentions: Having validated our theoretical model through comparison with measurements, we can now provide quantitative estimation of the parameters relevant to the emission and absorption of radiation. These parameters are the light extraction efficiency defined as Q/Qrad1, and the ratio between the energy densities of the electromagnetic field inside the microcavity and that of the incoming field (Eq.(4)). They are plotted respectively in Figures 4(a) and 4(b).

Bottom Line: In the microwave domain, for many years this task has been successfully performed by antennas, built from metals that can be considered almost perfect at these frequencies.In this work we experimentally study the light coupling properties of dense arrays of subwavelength THz antenna microcavities.This effect is quantitatively described by an analytical model that can be applied for the optimization of any nanoantenna array.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire "Matériaux et Phénomènes Quantiques", Sorbonne Paris Cité, Université Paris Diderot, CNRS-UMR 7162, FR-75013 Paris, France.

ABSTRACT
A key issue in modern photonics is the ability to concentrate light into very small volumes, thus enhancing its interaction with quantum objects of sizes much smaller than the wavelength. In the microwave domain, for many years this task has been successfully performed by antennas, built from metals that can be considered almost perfect at these frequencies. Antenna-like concepts have been recently extended into the THz and up to the visible, however metal losses increase and limit their performances. In this work we experimentally study the light coupling properties of dense arrays of subwavelength THz antenna microcavities. We demonstrate that the combination of array layout with subwavelength electromagnetic confinement allows for 10(4)-fold enhancement of the electromagnetic energy density inside the cavities, despite the low quality factor of a single element. This effect is quantitatively described by an analytical model that can be applied for the optimization of any nanoantenna array.

Show MeSH
Related in: MedlinePlus