Temperature-Dependent Nonlinear Optical Properties in Polar Quantum Dot Nanostructures

Karpagam B and Mathan Kumar K

Published on: 2025-06-28

Abstract

Quantum dots (QDs) or silicon nanocrystals (NCs) are of significant interest in many emerging domains; They are utilized in biomedical imaging contrast agents, photovoltaic devices and optoelectronics due to their luminous qualities, low toxicity good solubility and high mobility. The change of photoluminescent characteristics with temperature is a significant QD attribute that is directly related to sensing. Fluorescent intensity significantly increases with decreasing temperature. Three other metrics that could be used to quantify temperature are the change in intensity, the peak wavelength shift, and a change in fluorescence lifetime. These temperature-dependent changes in photoluminescence raise the prospect of creating fiber-optic temperature sensors based on QD fluorescence when combined with optical fiber technology.

They are utilized in biomedical imaging contrast agents, photovoltaic devices and optoelectronics due to their luminous qualities, low toxicity good solubility and high mobility. The temperature dependent optical properties of exciton confined in a strained Zn_1-xCd_xSe/ZnSe polar quantum dot are investigated assuming a spherically confinement potential. The electronic properties are obtained using variational formulism whereas optical properties are found using transfer matrix method. The strain effect contributed from the spontaneous and piezoelectric polarization is included in the Hamiltonian. The oscillator strengths of the exciton are obtained with the reduction of size of the quantum dot in the presence of temperature. The temperature depended oscillator strengths, the linear and third-order nonlinear optical absorption coefficients and the refractive index changes as a function of incident photon energy are investigated.

Keywords

Quantum dots; Optical properties; Piezoelectric polarization; Oscillator strength

Introduction

It is now feasible to create semiconductor nanostructures of different sizes thanks to the recent, quick advancements in contemporary technology, including electron lithography, metal organic chemical vapor deposition, and molecular beam epitaxy [1, 2]. Certain quantum effects arise in these semiconductor nanostructures because of the geometric confinement that limits the mobility of charges. Among these nanostructures, quantum dots (QDs) have attracted a lot of attention because of their many uses. Among all low dimensional semiconductors, quantum dots confining the charge carriers in all the dimensions to a nanometre scale will show exotic behaviour, specifically, they exhibit novel electronic and optical properties, such as ultra narrow spectral line width, which are different from their bulk materials. The efficient optical devices including infrared photo detectors, quantum dot lasers and single electron transistors can be fabricated with controllable process. So, one can engineer the electronic structure with the desired shape and size and tailor the spectrum to produce required photonic devices [3]. The polar semiconducting nano-heterostructures materials are given attention since they possess strong built-in electric field induced by the spontaneous and piezo electric polarizations whereas non-polar heterostructures will have negligible polaronic effects because of the low iconicity of atomic bonds. The results show that the electrical, optical and transport properties of quantum dots are sensitive to the geometrical size and the external perturbations.

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