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Tunable circular dichroism (CD) is widely used in biology signal detection and chemical analysis. Researchers usually tune CD by changing the chirality and symmetry of nanostructures either directly or indirectly. Changes to a planar nanostructure's chirality are resisted by its structural reciprocity, which also constrains its CD tuning. However, the distribution of finite non‐radiative (ohmic) losses on a planar nanostructure will not be constrained by the reciprocity of structure. Here, a nanostructure is designed to tune the intensity of energy losses rather than change the chirality and symmetry of the whole structure. The results show that not only are the position and intensity of CD affected, but also the sign of the CD signal changes. These methods and results can help in utilizing the new approach to tune the modes and sign of a CD signal. [ABSTRACT FROM AUTHOR]

Graphene bilayered split rings (BSRs) are proposed to generate tunable circular dichroism (CD). BSRs with traditional materials do not elicit the CD effect because of C symmetry. By contrast, BSRs with graphene can achieve the CD effect by varying the Fermi energy of each part of the split rings. The CD signal can be reversed from positive to negative or vice versa by exchanging the Fermi energy. CD effects can also be tuned by varying the Fermi energies of the different parts. This phenomenon indicates that the chirality of BSRs gradually change as the Fermi energy varies. This concept provides a method to change chirality and dynamically vary the CD effect without rebuilding the structures. [ABSTRACT FROM AUTHOR]

Asymmetric transmission (AT) reflects the conversion efficiency of a chiral nanostructure for circularly polarized light and is widely used in polarization and optoelectronic devices. In this study, a new mechanism is proposed to generate AT when a planar chiral nanostructure is illuminated under left‐handed circularly polarized (LCP) and right‐handed circularly polarized (RCP) light illumination. The new mechanism can be achieved by breaking the symmetry of the designed planar chiral nanostructure which give rise to a new transmittance peak and dip at a particular wavelength under RCP and LCP light illumination, respectively. The proposed new mechanism is also capable of actively tuning the generated resonant modes. Besides this, when graphene strips are added to the designed planar chiral nanostructure, similar results are obtained as that from breaking the symmetry of the planar chiral nanostructure. In this case, the generated AT could also be actively tuned by varying the Fermi energies of graphene strips. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Chiral plasmonic nanostructures (CPNs) are fabricated by glancing angle deposition method using EB evaporator. • The proposed system consists of Ag nanorod coupled with an Ag nanosurface, separated by an in-between SiO 2 layer. • CPNs exhibit LSPR and strong chiroptical responses in visible to near-infrared region. • The generated CD is easily tunable by changing the width of the nanosurface coupled with the nanorod. • An apparent enhancement and redshift of CD spectra is observed when the width of the nanosurface increases. Abstract Artificially engineered chiral plasmonic nanostructures (CPNs) have attracted considerable attention and have been widely studied in the recent decades because of their distinguishing optical properties. Researchers have focused on noble metal nanostructures, because of their strong chiroptical response in visible and near-infrared regions. In this study, a system of a nanorod coupled with a nanosurface, which were both made of silver, was proposed. Glancing angle deposition (GLAD) method was used to fabricate CPNs. The fabricated CPNs generated a strong circular dichroism (CD) signal under visible and near-infrared light illumination. A high peak was observed at approximately 600 nm, and an increasing trend of the CD intensity with a redshift was confirmed when the area of the nanosurface was increased. The generated CD could be tuned easily by changing the area of the nanosurface with an active control of the vapor deposition angle (glancing angle of the substrate) in the GLAD method. [ABSTRACT FROM AUTHOR]