Chiral Nanophotonics by Martin Schäferling

Author:Martin Schäferling
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

(4.34)

Here, is the electric field amplitude of the incident light. Note that this incident field can be arbitrarily polarized because the polarization does not affect the amplitude.

For all incident polarizations , the same normalization is performed. Therefore, does not denote the enhancement of OC compared to the incident light. Instead, the light field that is used for the normalization is assumed to be perfectly circular, which leads to the highest OC possible in a plane wave. Therewith, any value above unity describes a near-field pattern that has higher OC than possible for a plane wave with the same intensity and frequency as the incident light. The normalization is necessary to compare different nanostructures that are illuminated at different frequencies because OC is frequency-dependent. The sign of denotes the handedness of the chiral near-fields .

The resulting three-dimensional data is then plotted for analysis. A general overview over the shapes of regions with enhanced chiral near-fields is obtained via three-dimensional OC maps obtained by volume rendering. A detailed description of this plotting technique is given in Appendix C. Note that these maps are not optimal to obtain quantitative insights. Quantitative analysis is performed using two-dimensional slice plots.

Of course, the chiral near-fields should be as strong as possible, but this is not sufficient. There are additional requirements for chiral plasmonic near-field sources to be of use for enantiomer discrimination .

It is difficult to place one single chiral molecule in one chiral hot-spot in the experiment. Instead, a whole area is covered with the chiral analyte. Therefore, one has to look for a continuous region with uniform handedness where the averaged OC density is as high as possible. These regions should be located such that they are easily accessible by the chiral analyte. Regions with opposite OC should be hard to access because they diminish the expected signal.

For fabrication purposes , the dimensions and geometry of the structure must be chosen such that it can be fabricated by modern nanostructuring techniques. Of course, simple and cheap large-area fabrication would be preferable.

Fig. 4.4Plasmonic nanostructures and incident light are grouped by their chiral symmetry. Together, they build chiral plasmonic near-field sources whose properties are analyzed in the next chapters

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.