We theoretically investigate linear and nonlinear optical absorption coefficients (OACs) and refractive index changes (RICs) of two quantum wires (QWs) separated by a quantum-sized metal nanoparticle (MNP) using a density matrix method and dielectric quantum theory. The exciton-plasmon coupling and the dipole-dipole interaction (DDI) between the two QWs are taken into account. We find that the magnitudes of the linear and nonlinear OACs (RICs) from the QWs are enhanced by one order of magnitude, in contrast to the case without a MNP, due to the exciton-plasmon coupling and the DDI between the two QWs. The quantum size effect in a MNP induces a pronounced enhancement in the magnitudes of the linear and nonlinear OACs (RICs) with the increase of the MNP radius. Furthermore, the optical responses can be further strengthened via increasing the MNP radius or decreasing the radius and gap of the QWs, owing to the enhanced exciton-plasmon coupling and the DDI between the two QWs. Moreover, the magnitudes of the total OACs (RICs) are reduced by increasing the optical intensity, along with a splitting effect of the OACs under strong optical intensity. Our results provide the possibility of designing the hybrid nanostructures with large nonlinearity for applications in nano-devices such as optical switches and amplifiers.

中文翻译：

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半导体双量子线耦合到量子尺寸的金属纳米粒子的非线性光学性质

我们使用密度矩阵方法和介电量子理论从理论上研究了被量子尺寸的金属纳米粒子（MNP）隔开的两条量子线（QW）的线性和非线性光学吸收系数（OAC）和折射率变化（RIC）。考虑了两个量子阱之间的激子-等离子体激元耦合和偶极-偶极相互作用（DDI）。我们发现，由于两个QW之间的激子-等离子体激元耦合和DDI，与没有MNP的情况相比，来自QW的线性和非线性OAC（RIC）的幅度提高了一个数量级。MNP中的量子尺寸效应会随着MNP半径的增加而引起线性和非线性OAC（RIC）幅度的显着增强。此外，由于两个QW之间的激子-等离子体激元耦合和DDI增强，可以通过增加MNP半径或减小QW的半径和间隙来进一步增强光学响应。此外，通过增加光强度来降低总OAC（RIC）的大小，以及在强光强度下OAC的分裂效果。我们的结果为设计具有大非线性度的混合纳米结构提供了可能性，以用于光开关和放大器等纳米器件中。