Electric Field-Enhanced Nonlinear Optical Responses in n = 2 Ruddlesden–Popper Phase Perovskites

Abstract

In this work, we investigate nonlinear optical rectification (NOR), second-harmonic generation (SHG), and third-harmonic generation (THG) in an n = 2 Ruddlesden–Popper phase hybrid perovskite (RPP-HP) quantum well (QW) under the effect of an external electric field (F) applied along the confinement direction. These nonlinear optical (NLO) properties are analyzed using the compact density matrix formalism. The electronic subband structure, comprising discrete energy levels and associated wave functions, is computed by numerically solving the one-dimensional time-independent Schrödinger equation using the finite element method (FEM) within the framework of the effective mass approximation (EMA). Our results reveal a pronounced field dependence of the NLO response. The intensities of NOR, SHG, and THG increase markedly with rising F, driven by enhanced intersubband transition probabilities and asymmetry-induced nonlinearities. Moreover, the resonant peaks of these NLO processes exhibit noticeable blue shifts as the electric field increases, indicating stronger quantum confinement and larger intersubband separations. Notably, the observed behavior closely parallels that of conventional III–V semiconductor QWs such as GaAs. However, unlike III–V systems, RPP-HPs combine excellent nonlinear optical activity with the advantages of solution processability and low fabrication cost, making them a highly promising material platform for next-generation tunable optoelectronic and photonic devices.