Second Harmonic Generation Control in 2D Layered Materials: Status and Outlook

TLDR

Second‑harmonic generation, a key nonlinear optical effect, has shifted toward integrated, miniaturized on‑chip photonic devices, but 2D layered materials—despite their large second‑order susceptibility, atomically thin structure, and perfect phase‑matching—suffer from weak SHG efficiency limited by nanoscale light–matter interaction lengths, prompting the development of tunable, efficient SHG strategies. This review surveys recent advances in achieving highly efficient and tunable SHG in 2D layered materials and outlines challenges and future directions for their practical on‑chip integration. The authors systematically review SHG modulation and enhancement strategies in 2DLMs, grouping them into symmetry‑breaking techniques and light–matter interaction enhancement approaches. They identify key challenges and propose future research pathways to extend and realize practical on‑chip nonlinear devices leveraging SHG modulation and enhancement in 2DLMs.

Abstract

Abstract Second harmonic generation (SHG) as an essential nonlinear optical effect, has gradually shifted its research trend toward the integration and miniaturization of photonic and optoelectronic on‐chip devices in recent years. 2D layered materials (2DLMs) open up a new research paradigm of nonlinear optics due to their large second‐order susceptibility, atomically thin structure, and perfect phase‐matching. However, 2DLMs are facing a bottleneck of weak SHG conversion efficiency limit caused by short light–matter interaction lengths at a nanoscale. Moreover, advances in integrated on‐chip SHG devices based on 2DLMs rely on the continuing development of novel strategies with tunable and efficient SHG responses. Here, this review provides a comprehensive overview of recent progress in exploring highly efficient and tunable SHG responses in 2DLMs. Various modulation and enhancement strategies for the SHG response of 2DLMs are extensively studied and systematically discussed, which can be classified into two categories: symmetry breaking and light‐matter interaction enhancement. Moreover, remaining challenges and outlooks toward further extending and realizing the practical applications of 2DLMs in nonlinear on‐chip integrated devices with SHG modulation and enhancement characteristics are discussed.