Abstract

Here we show the fabrication and characterization of a novel class of biomimetic photonic chiral composites inspired by a recent finding in butterfly wing-scales. These three-dimensional networks have cubic symmetry, are fully interconnected, have robust mechanical strength and possess chirality which can be controlled through the composition of multiple chiral networks, providing an excellent platform for developing novel chiral materials. Using direct laser writing we have fabricated different types of chiral composites that can be engineered to form novel photonic devices. We experimentally show strong circular dichroism and compare with numerical simulations to illustrate the high quality of these three-dimensional photonic structures.

© 2011 OSA

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Figures (6)

Fig. 1
Fig. 1

Chiral composites derived from biomimetic designs. (a) Photograph of Callophrys rubi. (b) SEM image of the chiral srs-network found within the Callophrys rubi. (c) The gyroid minimal surface and its two complementary left handed (LHD) & right-handed (RHD) chiral srs-networks. (d) LHD srs-network. (e) RHD srs-network. (f) Achiral composite consisting of RHD and LHD srs-networks. (g) Chiral composite consisting of two RHD srs-networks. (h) A multifunctional photonic device, designed from a combination of chiral composites.

Fig. 2
Fig. 2

Images and transmission spectra of the chiral srs-network. (a) The pyramid-like design of the chiral srs-network from the side view and (b) top view. (c) SEM image of the microstructure possessing a pyramid-like shape to enhance the mechanical strength; the scale bar is 10 μm. (d) A close up view of the same structure showing excellent replication of the srs-network topology. The scale bar is 1 μm and a blue arrow shows the direction of the RHD 4-screw axis. (e) Experimentally measured transmission spectra of RCP (blue) and LCP (red) light at normal incidence.

Fig. 3
Fig. 3

Views of the chiral gyroid srs-network along [111]. (a) SEM image of the chiral gyroid srs-network. (b) A close up view showing the asymmetry induced by the aspherical focusing conditions of the DLW method. The scale bars are 10 μm (a) and 1 um (b). (c) View of the underlying srs network model.

Fig. 4
Fig. 4

SEM images and transmission spectra of the photonic chiral composites consisting of two srs networks. (a) The achiral composite with blue and red arrows to illustrate the opposite chirality of the two srs-networks, the scale bar is 1 μm. (b) Experimentally measured transmission spectra of RCP (blue) and LCP (red) light through the achiral composite. (c) The chiral composite. Blue arrows illustrate the same chirality of the two srs-networks, the scale bar is 1 μm. (d) Experimentally measured transmission spectra of RCP (blue) and LCP (red) light through the chiral composite. (e) SEM image of a multifunctional chiral microstructure, consisting of LHD and RHD srs-networks partially overlapping to form three distinct regions, the scale bar is 20 μm.

Fig. 5
Fig. 5

Simulated transmission spectra for RCP (blue) and LCP (red) light along [100]. The unit cell size is 3 μm and the filling fraction of a single network was approximately 15%. (a) Chiral single RHD srs-network. (b) Achiral composite consisting of a RHD and a LHD srs-network. (c) Chiral composite consisting of 2 RHD srs-networks.

Fig. 6
Fig. 6

Simulated polarisation conversion spectra for RCP (blue) and LCP (red) light incidence along [100]. The unit cell size is 3 μm and the filling fraction of a single network was approximately 15%. (a) Chiral srs-network. (b) Achiral composite consisting of a RHD and a LHD srs-network. (c) Chiral composite consisting of 2 RHD srs-networks, with broken cubic symmetry causing significant polarisation conversion.

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