Research on Circular Dichroism of Double L-shaped Metal Block Composite Structure
Abstract
The rapid development of surface plasmon photonics has promoted the application of optical chirality, expanding chirality research from traditional chiral molecules to artificial chiral nanostructures. Chirality refers to the characteristic that a substance does not have a coincidence with its mirror structure. The unique optical properties of chiral micro nano structures under circularly polarized light excitation have attracted increasing attention. Due to its different absorption of left-handed circularly polarized light and right-handed circularly polarized light, it can produce Circular Dichroism (CD) effect, which has a wide range of applications in life sciences, biochemistry, and medical diagnosis. Single planar nanostructures with simple structures often only produce weak CD signals, while three-dimensional chiral nanostructures, although having stronger CD effects compared to two-dimensional structures, have the disadvantage of being difficult to prepare. Therefore, the study of planar nanostructures that can generate significant CD responses has become particularly important. This article designs a double L-shaped metal block combination nanostructure by combining simple planar nanostructures to increase circular dichroism signals. By placing two L-shaped metal blocks close to each other, a CD enhancement effect is generated, and its inherent mechanism is the strong coupling effect between dipole resonances. A single L-shaped metal block can generate dipole oscillation modes. After combining them, a strong coupling effect between dipole resonances can be achieved, which adjusts the surface plasmon resonance characteristics and excites local field enhancement in the gaps of the composite structure. This field enhancement effect produces different responses to left-handed circularly polarized light and right-handed circularly polarized light excitation, thus forming a significant CD enhancement effect compared to a single L-shaped metal block structure.
