Broad-Band Chiral Reflectors based on Nano-Structured Biological Materials

In this work we study the reflection of circularly polarised light from a nano-structured biological material found in the exocuticle of scarabus beetles. This material is made of a stack of ultra-thin (~5 nm) uniaxial layers arranged in a left-handed helicoidal stack, which resonantly reflects circularly polarized light. A chirp in the layer thickness combined with a finite absorption coefficient produce a broad smooth reflectance spectrum. By comparing model calculations and electron microscopy with measured spectra we can explain our observations and quantify most relevant structural parameters.

Authors:

• D.J. Brink
• N.G. van der Berg
• L.C. Prinsloo
• A. Botha

Keywords:

• Chiral reflectors
• circularly polarised light
• helicoidal structures
• nano photonics.

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