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Circular dichroism (CD) spectroscopy, which measures the differential absorption of circularly polarized light with opposite handedness, is an important technique to detect and identify chiral molecules in chemistry, biology and life sciences. However, CD signals are normally very small due to the intrinsically weak chirality of molecules. Here we theoretically investigate the generation of chiral hotspots in silicon nanocube dimers for CD enhancement. Up to 15-fold enhancement of the global optical chirality is obtained in the dimer gap, which boosts the CD signal by one order of magnitude without reducing the dissymmetry factor. This chiral hotspot originates from the simultaneous enhancement of magnetic and electric fields and their proper spatial overlap. Our findings could lead to integrated devices for CD spectroscopy, enantioselective sensing, sorting and synthesis.
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Chiral optical properties of metasurfaces comprised of chiral media: effects of geometric and material chirality
We deconvolute the distinct and sometimes competing effects of geometric and material chirality in metastructures created from materials that are intrinsically chiral. We find that overlapping Mie-like resonances in nanodisk arrays leads to 6-fold CD enhancement compared to a uniform film. Furthermore, making the medium chiral does not necessarily increase CD; enhancement depends on the magnitude of the Pasteur parameter and its real and imaginary components. Finally, to demonstrate how geometric and material chirality can be combined, we design a geometrically chiral meta-atom out of chiral media and observe over 9-fold enhancement in both CD andg-factor compared to a metasurface comprised of achiral material.
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- Award ID(s):
- 2102835
- PAR ID:
- 10557090
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 32
- Issue:
- 25
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 45075
- Size(s):
- Article No. 45075
- Sponsoring Org:
- National Science Foundation
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