Multiple Ferroelectric‐Polarization‐Dependent Couplings and Stable Modulation of Nonlinear Light in 2D Material/Ferroelectric Van Der Waals Heterostructures

ABSTRACT Reliable, high‐density nonvolatile data storage requires new approaches to storage paradigms and readout mechanisms, underpinned by advanced multifunctional materials.​ Molecular ferroelectrics offer a promising pathway by leveraging reversible polarization switching and multidimensional optical properties. Herein, ultra‐smooth ferroelectric thin films of TMCM‐CdCl 3 were fabricated, with customizable 180° domains and ordered domain walls written via low voltage.​ Based on these designable ferroelectric domain patterns, diverse second‐harmonic generation (SHG) responses are observed at the engineered ferroelectric domain walls, and are tunable by the polarization of the incident light and the scanning depth. This phenomenon stems from the interplay between the nonlinear susceptibility tensors and axial polarization components in the diverse domain walls. Notably, we constructed the WS 2 /TMCM‐CdCl 3 van der Waals heterostructure and achieved multiple ferroelectric‐polarization‐dependent SHG modulation–effects absent in the isolated materials. Spectroscopy and theoretical analysis reveal that the SHG intensity reversal and polarization change arise from the interfacial coupling differences of the relative alignment of the ferroelectric polarization with the 2D material's polarity. Additionally, the system maintains near year‐long nonvolatile optical modulation and excellent environmental stability. These robust, multiple‐polarization‐dependent couplings and tunable behavior in nonlinear optics modulation could pave the way for nonvolatile optical memory and quantum photonic applications.