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Triple-helical nanowires by tomographic rotatory growth for chiral photonics.

Esposito M, Tasco V, Todisco F, Cuscunà M, Benedetti A, Sanvitto D, Passaseo A - Nat Commun (2015)

Bottom Line: Complex intertwined three dimensional structures such as multiple-helical nanowires could overcome these limitations, allowing the achievement of several chiro-optical effects combining chirality and isotropy.These three dimensional nanostructures show up to 37% of circular dichroism in a broad range (500-1,000 nm), with a high signal-to-noise ratio (up to 24 dB).Optical activity of up to 8° only due to the circular birefringence is also shown, tracing the way towards chiral photonic devices that can be integrated in optical nanocircuits to modulate the visible light polarization.

View Article: PubMed Central - PubMed

Affiliation: National Nanotechnology Laboratory-NNL, CNR-IMIP, VIA Arnesano, 73100 Lecce Italy.

ABSTRACT
Three dimensional helical chiral metamaterials resulted in effective manipulation of circularly polarized light in the visible infrared for advanced nanophotonics. Their potentialities are severely limited by the lack of full rotational symmetry preventing broadband operation, high signal-to-noise ratio and inducing high optical activity sensitivity to structure orientation. Complex intertwined three dimensional structures such as multiple-helical nanowires could overcome these limitations, allowing the achievement of several chiro-optical effects combining chirality and isotropy. Here we report three dimensional triple-helical nanowires, engineered by the innovative tomographic rotatory growth, on the basis of focused ion beam-induced deposition. These three dimensional nanostructures show up to 37% of circular dichroism in a broad range (500-1,000 nm), with a high signal-to-noise ratio (up to 24 dB). Optical activity of up to 8° only due to the circular birefringence is also shown, tracing the way towards chiral photonic devices that can be integrated in optical nanocircuits to modulate the visible light polarization.

No MeSH data available.


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Circular dichroism and S/N ratio(a) Schematic representation to indicate the handedness of incident and transmitted circular polarization in the experimental measurements.(b) Measured transmission spectra (T++, T+− and T−−, T−+) for RCP and LCP incident light, respectively.(c) Measured (solid line) and simulated (dashed line) circular dichroism (CD=(T++ − T−−)/(T+++ T−−)) with peak value of 37% and broadband in the visible range. The simulated curve, obtained by varying the Pt content with dielectric function described by the Drude model, is calculated by considering an effective Pt content of 40%, as expected for FIBID technique33. (d) Measured S/N ratio, defined as I++/I+− (I−−/I−+).
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Figure 3: Circular dichroism and S/N ratio(a) Schematic representation to indicate the handedness of incident and transmitted circular polarization in the experimental measurements.(b) Measured transmission spectra (T++, T+− and T−−, T−+) for RCP and LCP incident light, respectively.(c) Measured (solid line) and simulated (dashed line) circular dichroism (CD=(T++ − T−−)/(T+++ T−−)) with peak value of 37% and broadband in the visible range. The simulated curve, obtained by varying the Pt content with dielectric function described by the Drude model, is calculated by considering an effective Pt content of 40%, as expected for FIBID technique33. (d) Measured S/N ratio, defined as I++/I+− (I−−/I−+).

Mentions: The measured normal-incidence transmittance and conversion spectra (figure 3b) of the square THN array (shown in figure 1b) demonstrate a circular dichroism (CD) up to 37% (figure 3c, solid line) with a broadband covering the wavelength range from 500 nm to 1000 nm, in good agreement with the simulated circular dichroism (figure 3c, dashed line). Reflection measurements performed for both LCP and RCP incident light reported in Supplementary Figure 1 show very low values of reflection intensity allowing to assert that the losses in the transmission spectra are mainly related to the absorption mechanism that appears to be different for the two circular polarizations29. In figure 3d we report the spectrum of the S/N ratio, resulting ≥10 dB in the whole measured range, with maximum values of 24 dB reached between 500 and 600 nm and two times larger than previously reported in SHNs25, 30 .


Triple-helical nanowires by tomographic rotatory growth for chiral photonics.

Esposito M, Tasco V, Todisco F, Cuscunà M, Benedetti A, Sanvitto D, Passaseo A - Nat Commun (2015)

Circular dichroism and S/N ratio(a) Schematic representation to indicate the handedness of incident and transmitted circular polarization in the experimental measurements.(b) Measured transmission spectra (T++, T+− and T−−, T−+) for RCP and LCP incident light, respectively.(c) Measured (solid line) and simulated (dashed line) circular dichroism (CD=(T++ − T−−)/(T+++ T−−)) with peak value of 37% and broadband in the visible range. The simulated curve, obtained by varying the Pt content with dielectric function described by the Drude model, is calculated by considering an effective Pt content of 40%, as expected for FIBID technique33. (d) Measured S/N ratio, defined as I++/I+− (I−−/I−+).
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Related In: Results  -  Collection

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Figure 3: Circular dichroism and S/N ratio(a) Schematic representation to indicate the handedness of incident and transmitted circular polarization in the experimental measurements.(b) Measured transmission spectra (T++, T+− and T−−, T−+) for RCP and LCP incident light, respectively.(c) Measured (solid line) and simulated (dashed line) circular dichroism (CD=(T++ − T−−)/(T+++ T−−)) with peak value of 37% and broadband in the visible range. The simulated curve, obtained by varying the Pt content with dielectric function described by the Drude model, is calculated by considering an effective Pt content of 40%, as expected for FIBID technique33. (d) Measured S/N ratio, defined as I++/I+− (I−−/I−+).
Mentions: The measured normal-incidence transmittance and conversion spectra (figure 3b) of the square THN array (shown in figure 1b) demonstrate a circular dichroism (CD) up to 37% (figure 3c, solid line) with a broadband covering the wavelength range from 500 nm to 1000 nm, in good agreement with the simulated circular dichroism (figure 3c, dashed line). Reflection measurements performed for both LCP and RCP incident light reported in Supplementary Figure 1 show very low values of reflection intensity allowing to assert that the losses in the transmission spectra are mainly related to the absorption mechanism that appears to be different for the two circular polarizations29. In figure 3d we report the spectrum of the S/N ratio, resulting ≥10 dB in the whole measured range, with maximum values of 24 dB reached between 500 and 600 nm and two times larger than previously reported in SHNs25, 30 .

Bottom Line: Complex intertwined three dimensional structures such as multiple-helical nanowires could overcome these limitations, allowing the achievement of several chiro-optical effects combining chirality and isotropy.These three dimensional nanostructures show up to 37% of circular dichroism in a broad range (500-1,000 nm), with a high signal-to-noise ratio (up to 24 dB).Optical activity of up to 8° only due to the circular birefringence is also shown, tracing the way towards chiral photonic devices that can be integrated in optical nanocircuits to modulate the visible light polarization.

View Article: PubMed Central - PubMed

Affiliation: National Nanotechnology Laboratory-NNL, CNR-IMIP, VIA Arnesano, 73100 Lecce Italy.

ABSTRACT
Three dimensional helical chiral metamaterials resulted in effective manipulation of circularly polarized light in the visible infrared for advanced nanophotonics. Their potentialities are severely limited by the lack of full rotational symmetry preventing broadband operation, high signal-to-noise ratio and inducing high optical activity sensitivity to structure orientation. Complex intertwined three dimensional structures such as multiple-helical nanowires could overcome these limitations, allowing the achievement of several chiro-optical effects combining chirality and isotropy. Here we report three dimensional triple-helical nanowires, engineered by the innovative tomographic rotatory growth, on the basis of focused ion beam-induced deposition. These three dimensional nanostructures show up to 37% of circular dichroism in a broad range (500-1,000 nm), with a high signal-to-noise ratio (up to 24 dB). Optical activity of up to 8° only due to the circular birefringence is also shown, tracing the way towards chiral photonic devices that can be integrated in optical nanocircuits to modulate the visible light polarization.

No MeSH data available.


Related in: MedlinePlus