Ultrafast All-Optical Modulation in 2D Hybrid Perovskites

TLDR

Two‑dimensional Ruddlesden‑Popper perovskites exhibit large nonlinear optical properties driven by strong excitonic effects in their multiple quantum wells. In this work, nondegenerate pump‑probe spectroscopy between 600‑1000 nm is employed to investigate how nonlinear effects influence the ultrafast dynamics of 2D RPP thin flakes. When the excitation is resonant with the excitonic absorption, the ultrafast nonlinear response is suppressed because linear absorption generates long‑lived free carriers. The results demonstrate that sub‑bandgap excitation of ~100 nm thick 2D RPP sheets produces ~2 % reflectivity modulation within 20 fs via Kerr effect and two‑photon absorption, outperforming metasurfaces by ~5× and indicating their potential as nanoscale all‑optical modulators for ultrafast information processing, optical data transmission, and high‑performance computing.

Abstract

Two-dimensional (2D) hybrid organic-inorganic Ruddlesden-Popper perovskites (RPPs) have been recently shown to exhibit large nonlinear optical properties due to the strong excitonic effects present in their multiple quantum wells. In this work, we use nondegenerate pump-probe spectroscopy in the 600-1000 nm wavelength range to study the influence of nonlinear effects on the ultrafast dynamics of 2D RPP thin flakes. We find that, under sub-bandgap excitation, ∼100 nm thick perovskite sheets allow up to ∼2% reflectivity modulation within a 20 fs period, due to the nonlinear optical Kerr effect and two-photon absorption, surpassing by a factor of ∼5 the reported nonlinear performance of photonic metasurfaces and single nanoantennas. When the excitation is resonant with the excitonic absorption, the ultrafast nature of the nonlinear response is lost due to the presence of linear absorption creating long-lived free carriers. Our results suggest that 2D RPPs are potential nanoscale all-optical modulators in the visible/near-infrared waveband for applications such as ultrafast information processing, optical data transmission, and high-performance computing.