Photonic bands, superchirality, and inverse design of a chiral minimal metasurface

Year: 2019

Authors: Zanotto S., Mazzamuto G., Riboli F., Biasiol G., La Rocca G. C., Tredicucci A., Pitanti A.

Autors Affiliation: Istituto Nanoscienze – CNR and Laboratorio NEST; Istituto Nazionale di Ottica INO – CNR Sesto Fiorentino; European Laboratory for Non Linear Spectroscopy; Istituto Officina dei Materiali CNR, Laboratorio TASC: Scuola Normale Superiore and CNISM

Abstract: Photonic band structures are a typical fingerprint of periodic optical structures, and are usually observed in spectroscopic quantities such as transmission, reflection, and absorption. Here we show that the chiro-optical response of a metasurface constituted by a lattice of non-centrosymmetric, L-shaped holes in a dielectric slab shows a band structure, where intrinsic and extrinsic chirality effects are clearly recognized and connected to localized and delocalized resonances. Superchiral near-fields can be excited in correspondence to these resonances, and anomalous behaviors as a function of the incidence polarization occur. Moreover, we have introduced a singular value decomposition (SVD) approach to show that the above mentioned effects are connected to specific fingerprints of the SVD spectra. Finally, by means of an inverse design technique we have demonstrated that the metasurface based on an L-shaped hole array is a minimal one. Indeed, its unit cell geometry depends on the smallest number of parameters needed to implement arbitrary transmission matrices compliant with the general symmetries for 2d-chiral structures. These observations enable more powerful wave operations in a lossless photonic environment.

Journal/Review: NANOPHOTONICS

Volume: 8 (12)      Pages from: 2291  to: 2301

More Information: We like to acknowledge Alberto Bordin, who participated in an early stage of the project, Stefano Luin (Scuola Normale Superiore, Pisa) for the support on data fitting, Francesca Bontempi (Scuola Superiore Sant?Anna, Pisa) for ellipsometric measurements of the dielectric thin film, Sara Nocentini and Lorenzo Pattelli (LENS, Firenze) for their useful discussions and precious support for the spectroscopic measurements. This work was in part supported by the European Commission through the project PHENOMEN (H2020-EU-713450).
KeyWords: metasurface, polarization, chirality, inverse design, superchirality, photonic bands
DOI: 10.1515/nanoph-2019-0321

Citations: 16
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