Circular dichroism (CD) spectroscopy is an important technique for detecting and identifying chiral molecules in the fields of chemistry, biology, and other life sciences. Artificial plasmonic nanostructures exhibit considerable CD effects, but the preparation of 3D and multilayer chiral structures that exhibit large CD signals is usually difficult. Strong CD effects and simple fabrication processes are necessary. In this study, double-layer complementary nanostructures (DLCNs) that can generate prominent CD signals are prepared with a simple experimental method. Numerical calculations show that the physical mechanism underlying the CD effect is the coupling between localized surface plasmon resonances excited in complementary nanostructures and surface plasmon polaritons excited on a metal nanofilm under left-circularly polarized and right-circularly polarized light illuminations. The CD effect can be tuned by changing the parameter of the DLCN array. Results provide a way to generate CD effects with spatially complementary nanostructures and may provide an avenue for the chiral manipulation of light. These chiral nanostructures can be fabricated through simple methods, have considerable CD signals, and provide insights into the chiral optical response, providing novel tools for the design of chiral optoelectronic devices.

Circular dichroism (CD) demonstrates broad application prospects in enantioselective catalysis, chiral separation, and ultrasensitive detection. Increasing the CD intensity of easily fabricated plasmonic nanostructures will promote the application of these artificial nanostructures. A chiral plasmonic system that consists of two unaligned nanorods and a metal film is proposed in this study to achieve a large CD effect. Indirect coupling of a nanorod–film–nanorod in the proposed chiral plasmonic system generates a larger CD intensity compared to the direct coupling of a nanorod–nanorod. In addition, the effects of structural parameters on the CD effect of the proposed system are numerically investigated. Results showed that the indirect coupling is strongly dependent on the separation between the nanorod and the metal film. The results of this study can provide an effective strategy to enhance the CD effect of plasmonic chiral systems.

Circular dichroism (CD) is widely used in enantiomer identification, photodetection, and circular polarization devices. Improving the CD signal of easily prepared 3D chiral nanostructures by designing templates remains a challenge in this field. Herein, double-layer nanostructures, which can be prepared with one-time electron beam lithography (EBL) combined with electron beam deposition, are theoretically and experimentally shown to exhibit a CD effect. Theoretical results show that the double-layer nanostructures form strong local electromagnetic fields between the layers due to near-field coupling and that the relative positions of the different parts that break the symmetry of the nanostructures lead to differences in distorted magnetic fields and transmission under circularly polarized light (CPL) excitation, thereby producing CD effects. In addition, modifications in arm positions change the asymmetry of the structure, resulting in large CD effects due to amplified left and right CPL transmission differences. Furthermore, the CD effect can be tuned remarkably by changing the VO 2 state to regulate the near-field coupling. These results provide a way to obtain CD effects by using identical nanostructures in the upper and bottom layers and manipulating near-field coupling. Such chiral devices have potential applications in chiral recognition, remote temperature readout, and advanced control of chemical reactions.

In this paper, modulation of light–matter interactions by a magnetic field is used to generate circular dichroism (CD) from an achiral plasmonic nanostructure. Theoretical investigations show an increase in light absorption by the nanostructure in the presence of a magnetic field. The achiral nanostructure exhibits CD in external magnetic field parallel to circularly polarized light (CPL) incidence. The CD emergence is caused by modulation of electron motion to reduced/enhanced frequencies under CPL incidence. Compared to previous studies, in this paper the mechanism of CD emergence, and the physical reasoning behind the change in CD due to change in magnetic field direction and intensity, are explained. CD intensity increases with increasing magnetic field intensity, while CD sign changes on magnetic field direction reversal. Varying structural parameters significantly influences CD intensity. This study can be helpful in magneto-optics and in magneto-chiral applications.

Chiral structures have a wide range of applications, such as biometric identification, chemical analysis, and chiral sensing. The simple fabrication process of chiral nanostructures that can produce a significant circular dichroism (CD) effect remains a challenge. Here, a three-dimensional (3D) cantilever-shaped nanostructure, which inherits the chiral advantages of 3D nanostructures and simplicity of 2D nanostructures, is proposed. The nanostructure can be prepared by the combination of one-time electron beam lithography and oblique-angle deposition and consists of a thin metal film with periodic holes such that two hanging arms were attached to the edges of holes. The length of the cantilever and the height difference between the two arms can be adjusted by controlling the tilt angle of beam current during the deposition processes. Numerical calculations showed that the enhancement of CD signal was achieved by plasmon distortion on the metal film by the lower hanging part of the cantilever structure. Furthermore, signals can be actively adjusted using a temperature-sensitive polydimethylsiloxane (PDMS) material. The angle between the lower cantilever and the top metal film was regulated by the change in PDMS volume with temperature. The results provide a new way to fabricating 3D nanostructures and a new mechanism to enhance the CD signal. The proposed nanostructure may have potential applications, such as in ultra-sensitive detection and remote temperature readout, and is expected to be an ultra-compact detection tool for nanoscale structural and functional information.