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In this paper, we use computational methods to investigate the plasmonic properties of multi-layered dimers. These dimers are composed of layers of gold–silica–gold and gold–silica–silver, with shifts in their core and middle layers. This asymmetry breaks the geometrical symmetry, revealing plasmon resonances that are typically invisible in concentric geometries. This study explains the origin of these resonances using plasmon hybridization theory, highlighting the interaction between primitive and multipolar modes in the core and shell of the investigated proposed structure. These interactions improve the coupling of the higher order modes to light by inducing a dipole moment. The asymmetry is attributed to the uneven distribution of surface charges, leading to a transition from multipolar to dipolar characteristics in the higher order modes. Through visual examination of the dipolar component in surface charge distributions, we qualitatively establish the relative amplitudes of the modes. Our results demonstrate the red-shifting of resonant wavelengths with increased core offset, resulted in the enhanced absorption rather than scattering. This computational study provide a terse depth for the deeper understanding towards the plasmonic behavior in multilayered dimers with core and middle layer shifts, uncovering the underlying mechanisms of symmetry breaking. [ABSTRACT FROM AUTHOR]

We theoretically demonstrated a kind of plasmon coupled elliptical/crescent nanostructure to achieve a vast range of applications based on nanolaser or spaser with high intensity. To overcome the ohmic losses, the plasmon ellipse is composed of the gold film substrate with a gain media. A simple ellipse has been chosen from which a variety of dimer configurations have been formed by the symmetry alteration technique which is then tested for different light polarizations and gap variations. The proposed model supports localized surface plasmon resonance mode (LSPR). Moreover, the localized surface plasmon resonance (LSPR) property of the proposed nanostructure is numerically analysed by the finite-element method (FEM), and the results show that the electric field intensity (EFI) can be amplified to a large value by symmetry breaking in the elliptical nanostructure. Various plasmon modes can be excited by selecting the appropriate gain media. In addition to this, a compact tuneable multi-wavelength nanolaser (spaser) can be developed by using this model. [ABSTRACT FROM AUTHOR]