Laser Pulse Induced Second- and Third-Harmonic Generation of Gold Nanorods with Real-Time Time-Dependent Density Functional Tight Binding (RT-TDDFTB) Method

TL;DR

This paper uses the RT-TDDFTB method to analyze how laser pulses induce second- and third-harmonic generation in gold nanorods, revealing the effects of laser parameters and nanorod configurations on nonlinear optical responses.

Contribution

It introduces a systematic computational approach to study harmonic generation in gold nanorods, emphasizing the role of symmetry breaking and nanorod length variations.

Findings

Symmetry disruption enhances second-harmonic generation.

Nanorod length influences plasmon energies and harmonic responses.

Laser parameters significantly affect nonlinear optical signals.

Abstract

In this study, we investigate second- and third-harmonic generation processes in Au nanorod systems using the real-time time-dependent density functional tight binding method. Our study focuses on the computation of nonlinear signals based on the time dependent dipole response induced by linearly polarized laser pulses interacting with nanoparticles. We systematically explore the influence of various laser parameters, including pump intensity, duration, frequency, and polarization directions, on harmonic generation. We demonstrate all the results using Au nanorod dimer systems arranged in end-to-end configurations, and disrupting the spatial symmetry of regular single nanorod systems is crucial for second-harmonic generation processes. Furthermore, we study the impact of nanorod lengths, which lead to variable plasmon energies, on harmonic generation, and estimates of polarizabilities and hyper-polarizabilities are provided.