☆ 4.6 Article

The Effect of the Core on the Absorption in a Hybrid Semiconductor Quantum Dot-Metal Nanoshell System

APPLIED SCIENCES-BASEL (2023)

Journal

APPLIED SCIENCES-BASEL

Volume 13, Issue 2, Pages -

Publisher

MDPI

DOI: 10.3390/app13021160

Keywords

absorption spectrum; exciton lifetime; gain without inversion; hybrid nanostructure; metal nanoshell; semiconductor quantum dot

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Abstract

In this study, we investigated the optical absorption in a hybrid structure consisting of a metal nanoshell and a semiconductor quantum dot interacting with a linearly polarized probe electromagnetic field. By deriving the equations of motion and analytical expressions for the linear susceptibility, we found that by engineering the thickness of the metal nanoshell, the material of the dielectric core, and the interparticle distance, an optimum response can be achieved. Two distinct types of hybrid exciton states were identified, showing different spectral characteristics and exciton lifetimes depending on the strength of the exciton-plasmon coupling.

We examine the optical absorption in a hybrid structure composed of a metal nanoshell and a semiconductor quantum dot, while interacting with a linearly polarized probe electromagnetic field. First, we derive the equations of motion, in the rotating wave approximation. Then we procced to the derivation of analytical expressions for the linear susceptibility of the metal nanoshell and the semiconductor quantum dot. The imaginary part of the susceptibility expresses the absorption coefficient. We find that by properly engineering the thickness of the metal nanoshell, the material of the dielectric core and the interparticle distance, we may achieve an optimum response. We identify the emergence of two distinct types of hybrid exciton states. One of them emerges in the strong exciton-plasmon coupling regime for low values of the dielectric constant and the radius of the dielectric core. This type of hybrid exciton exhibits an amplified gain without population inversion and a quenched absorption resonance accompanied by a suppressed exciton lifetime. The second type of hybrid exciton emerges in the weak exciton-plasmon coupling regime and presents the opposite spectral characteristics. Here, the exciton lifetime presents a substantial increase, especially for small interparticle distances, in which case the semiconductor quantum dot and the metal nanoshell are strongly coupled with one another.

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Linear optical response of a quantum dot-metal nanoshell hybrid system

Alexandros Kontakos, Emmanuel Paspalakis, Spyridon G. Kosionis

Summary: We investigate the linear optical response in a hybrid nanostructure composed of a semiconductor quantum dot located in proximity to a core-shell metal nanoparticle. Using the density matrix approach, we derive analytical expressions for the linear optical susceptibility of the two components of the nanostructure, which are dependent on the geometrical characteristics of the metal nanoshell, on the material of both the dielectric environment and the dielectric core, as well as on the polarization direction of the incident electric field and the distance separating the two nanoparticles. The nanosystem under investigation shows significant gain without population inversion in the semiconductor quantum dot.

PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES (2023)