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3D optical Yagi-Uda nanoantenna array.

Dregely D, Taubert R, Dorfmüller J, Vogelgesang R, Kern K, Giessen H - Nat Commun (2011)

Bottom Line: We show that the concepts of radiofrequency antenna arrays can be applied to the optical regime proving superior directional properties compared with a single planar optical antenna, particularly for emission and reception into the third dimension.Measuring the optical properties of the structure reveals that impinging light on the array is efficiently absorbed on the subwavelength scale because of the high directivity.Moreover, we show in simulations that combining the array with suitable feeding circuits gives rise to the prospect of beam steering at optical wavelengths.

View Article: PubMed Central - PubMed

Affiliation: 4th Physics Institute and Research Center SCoPE, University of Stuttgart, D-70569 Stuttgart, Germany.

No MeSH data available.


Related in: MedlinePlus

Simulated spectra and experimental measurement of the optical Yagi–Uda array.(a) Numerical transmission and reflection spectra for forward and backward incidence on the antenna array as defined in the structure on the left. The white arrow indicates the polarization of the electric field vector along the axis of the rods. The blue curve shows the transmission spectrum, which is equal for both incidences. The red curve is the reflection spectrum for forward incidence and the green curve shows the reflection for backward incidence. (b) Experimental transmission (left) and reflection spectra (right) for forward incidence and backward incidence (right). The measured transmission is equal for both incidences, whereas the reflection spectra are different for forward and backward incidence.
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f3: Simulated spectra and experimental measurement of the optical Yagi–Uda array.(a) Numerical transmission and reflection spectra for forward and backward incidence on the antenna array as defined in the structure on the left. The white arrow indicates the polarization of the electric field vector along the axis of the rods. The blue curve shows the transmission spectrum, which is equal for both incidences. The red curve is the reflection spectrum for forward incidence and the green curve shows the reflection for backward incidence. (b) Experimental transmission (left) and reflection spectra (right) for forward incidence and backward incidence (right). The measured transmission is equal for both incidences, whereas the reflection spectra are different for forward and backward incidence.

Mentions: In Figure 3, we investigate the optical properties in transmission and reflection of the array. In our experimental setup, the array receives radiation from two opposite directions. As depicted in Figure 3a, we define the forward direction for incident light from the director side and the backward direction for incident light from the reflector side. The light is polarized along the axis of the nanorods. The spectra in Figure 3a show the calculated transmission and reflection of the Yagi–Uda antenna array. By reciprocity, the transmitted intensity from the forward direction is equal to the transmitted intensity from the backward direction (blue curve), whereas more light incident from the backward direction is reflected (green curve) than from the forward direction (red curve). A significant difference between the two reflection spectra occurs at 1.5 μm, at which the radiation pattern shows the highest asymmetry. Nearly no light incoming from the positive z-direction is reflected at this wavelength. This is due to the resonant behaviour of the single Yagi–Uda nanoantenna, which has been designed to have maximum directivity into the forward direction at this wavelength. The experimental results are plotted in Figure 3b. The solid blue curve in the left plot shows the transmission spectrum for forward incidence, and the dashed blue curve for backward incidence. Three resonances occur, which are red- and blue-shifted compared with the particle plasmon resonance of equivalent single nanorod arrays (Supplementary Fig. S1). Hence, the three layers couple to each other. As in the simulated spectra, the transmitted intensity is equal from both directions. In reflection (right plot in Fig. 3b), more light is reflected for backward incidence than for forward incidence, which clearly confirms the broken forward–backward symmetry of directivity. By changing the polarization along the y-direction perpendicular to the long axes of the rods, the structural symmetry is not broken along the z-direction and no pronounced differences in the reflection spectra for forward and backward directions occur (Supplementary Fig. S2). A significant dip in the reflection spectrum from forward direction occurs at λ=1.42 μm. We attribute the deviation of the resonance position to geometrical differences in the simulated and the fabricated structure. As the spacer layer is spin coated, the distance between the layers may slightly vary from the nominal 100 nm.


3D optical Yagi-Uda nanoantenna array.

Dregely D, Taubert R, Dorfmüller J, Vogelgesang R, Kern K, Giessen H - Nat Commun (2011)

Simulated spectra and experimental measurement of the optical Yagi–Uda array.(a) Numerical transmission and reflection spectra for forward and backward incidence on the antenna array as defined in the structure on the left. The white arrow indicates the polarization of the electric field vector along the axis of the rods. The blue curve shows the transmission spectrum, which is equal for both incidences. The red curve is the reflection spectrum for forward incidence and the green curve shows the reflection for backward incidence. (b) Experimental transmission (left) and reflection spectra (right) for forward incidence and backward incidence (right). The measured transmission is equal for both incidences, whereas the reflection spectra are different for forward and backward incidence.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104549&req=5

f3: Simulated spectra and experimental measurement of the optical Yagi–Uda array.(a) Numerical transmission and reflection spectra for forward and backward incidence on the antenna array as defined in the structure on the left. The white arrow indicates the polarization of the electric field vector along the axis of the rods. The blue curve shows the transmission spectrum, which is equal for both incidences. The red curve is the reflection spectrum for forward incidence and the green curve shows the reflection for backward incidence. (b) Experimental transmission (left) and reflection spectra (right) for forward incidence and backward incidence (right). The measured transmission is equal for both incidences, whereas the reflection spectra are different for forward and backward incidence.
Mentions: In Figure 3, we investigate the optical properties in transmission and reflection of the array. In our experimental setup, the array receives radiation from two opposite directions. As depicted in Figure 3a, we define the forward direction for incident light from the director side and the backward direction for incident light from the reflector side. The light is polarized along the axis of the nanorods. The spectra in Figure 3a show the calculated transmission and reflection of the Yagi–Uda antenna array. By reciprocity, the transmitted intensity from the forward direction is equal to the transmitted intensity from the backward direction (blue curve), whereas more light incident from the backward direction is reflected (green curve) than from the forward direction (red curve). A significant difference between the two reflection spectra occurs at 1.5 μm, at which the radiation pattern shows the highest asymmetry. Nearly no light incoming from the positive z-direction is reflected at this wavelength. This is due to the resonant behaviour of the single Yagi–Uda nanoantenna, which has been designed to have maximum directivity into the forward direction at this wavelength. The experimental results are plotted in Figure 3b. The solid blue curve in the left plot shows the transmission spectrum for forward incidence, and the dashed blue curve for backward incidence. Three resonances occur, which are red- and blue-shifted compared with the particle plasmon resonance of equivalent single nanorod arrays (Supplementary Fig. S1). Hence, the three layers couple to each other. As in the simulated spectra, the transmitted intensity is equal from both directions. In reflection (right plot in Fig. 3b), more light is reflected for backward incidence than for forward incidence, which clearly confirms the broken forward–backward symmetry of directivity. By changing the polarization along the y-direction perpendicular to the long axes of the rods, the structural symmetry is not broken along the z-direction and no pronounced differences in the reflection spectra for forward and backward directions occur (Supplementary Fig. S2). A significant dip in the reflection spectrum from forward direction occurs at λ=1.42 μm. We attribute the deviation of the resonance position to geometrical differences in the simulated and the fabricated structure. As the spacer layer is spin coated, the distance between the layers may slightly vary from the nominal 100 nm.

Bottom Line: We show that the concepts of radiofrequency antenna arrays can be applied to the optical regime proving superior directional properties compared with a single planar optical antenna, particularly for emission and reception into the third dimension.Measuring the optical properties of the structure reveals that impinging light on the array is efficiently absorbed on the subwavelength scale because of the high directivity.Moreover, we show in simulations that combining the array with suitable feeding circuits gives rise to the prospect of beam steering at optical wavelengths.

View Article: PubMed Central - PubMed

Affiliation: 4th Physics Institute and Research Center SCoPE, University of Stuttgart, D-70569 Stuttgart, Germany.

No MeSH data available.


Related in: MedlinePlus