Modelling and nanofabrication of chiral dielectric metasurfaces

Year: 2023

Authors: Fagiani L., Gandolfi M., Carletti L., De Angelis C., Osmond J., Bollani M.

Autors Affiliation: Politecn Milan, Dept Phys, Piazza Leonardo Da Vinci 32, I-20133 Milan, Italy; Univ Brescia, Dept Informat Engn, Via Branze 38, I-25123 Brescia, Italy; INO CNR, Via Branze 45, I-25123 Brescia, Italy; CNIT, Viale GP Uberi 181-A, I-43124 Parma, Italy; Barcelona Inst Sci & Technol, ICFO Inst Ciencies Foton, Barcelona 08860, Spain; CNR IFN, LNESS Lab, Via Anzani 42, I-22100 Como, Italy.

Abstract: Polarization control through all-dielectric metasurfaces holds great potential in different fields, such as telecommunications, biochemistry and holography. Asymmetric chiral metasurfaces supporting quasi-bound states in the continuum may prove very useful for controlling and manipulating the polarization state of light. A crucial quantity for characterizing the optical chirality is the circular dichroism (CD). In this work we analyse how the CD and quality factor of the optical mode can be strongly influenced by a nanofabrication error. Modelling the nanofabrication uncertainties on the gaps of the chiral metasurface, the imperfections of the etchings process or the modification of the asymmetry factor, we found that the proper engineering of the gap between the nanostructures of the unit cell is the most important parameter to achieve a high-quality factor and enhanced optical dichroism. An optimization of the nanofabrication processes, such as dose factor, dwell time and plasma etching demonstrates that, for a writing field of 100 & mu;m2, it is possible to obtain morphologically precise chiral metasurfaces, with fabrication uncertainties lower than those that would limit Q factor and chirality property.

Journal/Review: MICRO AND NANO ENGINEERING

Volume: 19      Pages from: 100187-1  to: 100187-5

More Information: We acknowledge funding from the Russian Science Foundation grant n ’ 22-12-00204 and the Ministero dell’Istruzione, dell’Universita e della Ricerca (grant n ’ 2017MP7F8F) . M. G. acknowledges financial support by European Union FESR o FSE, PON Ricerca e Innovazione 2014-2020-DM 1062/2021.
KeyWords: Chiral metasurface; Circular dichroism; Dielectric metasurface; Quality factor; EBL; Third-harmonic generation
DOI: 10.1016/j.mne.2023.100187

Citations: 7
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