Second harmonic generation as an optical tool in the characterization of artificial chirality in self-organized plasmonic nanostructures
A. Belardini1, M. Centini1, G. Leahu1, A. Benedetti1, E. Fazio1, M. Bertolotti1, C. Sibilia1, Joseph W. Haus2, Andrew Sarangan2
- Sapienza Università di Roma,Via A. Scarpa 14, I-00161 Roma, ITALY.
- Department of Electrical and Computer Engineering, University of Dayton, Dayton, Ohio, USA.
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keywords: second harmonic generation, artificial chirality, self assembled nanostructures, circular dichroism.
Chiral systems (systems that present a lack of mirror symmetry) are usually present in nature such as in proteins, sugars, DNA, so that chirality become a very much studied property due to its potential applications in different areas, as analytical chemistry, crystallography, molecular biology. Moreover, artificial chiral materials may find application in nanophotonics for polarization control devices.
In particular, self-assembled approach gives the possibility to prepare large area nanostructured samples that show the so-called planar or two-dimensional chirality and also samples that presents extrinsic chirality. In the latter case the arising of chiral behaviour is due to proper alignment of achiral elements with respect to the measurement setup. This phenomenon was originally discovered and studied in the linear optics regime, but non-linear optical characterisation techniques in particular the second harmonic generation (SHG) show a dramatic enhance of the visibility of this phenomenon.
Here a discussion about symmetry breaking in artificial chiral metamaterials is presented, while the experimental evidence was given by second order nonlinear optical measurements on different self-organised plasmonic samples.
The measurements were performed by using circular polarised laser excitation at the wavelength of 800nm and by observing the second harmonic response at the wavelength of 400nm in different polarization states.
