AI 中文总结
研究旨在探索用于片上非线性光子学应用的材料，通过自催化气-液-固生长合成非中心对称γ相GaS纳米带，其有强SHG，集成到SiN波导上实现高效片上SHG等，确立其为可用于片上光子集成的非线性材料。
AI 中文摘要
范德华半导体中的二阶非线性光学过程为紧凑型、可集成光子转换平台提供了一条引人注目的途径。在III-VI范德华半导体中，GaS因其宽带隙抑制近红外激光激发下的双光子吸收而特别有吸引力。然而，块状GaS通常以中心对称的β相结晶，这消除了二阶非线性并严重限制了其在非线性光子学中的应用。在此，我们证明通过自催化气-液-固生长合成的GaS纳米带主要以非中心对称的γ相堆叠结晶。这种行为源于Ga催化剂界面处的边缘选择性生长动力学，它稳定了γ相并实现了确定性的面内偶极矩排列。GaS纳米带表现出强烈的二次谐波产生（SHG），其强度与广泛使用的非线性光学材料GaSe相当。此外，我们将纳米带集成到SiN波导上，并展示了高效的片上SHG和和频产生。这些结果确立了γ-GaS纳米带作为一种适用于片上光子集成的可转移一维非线性材料，并表明它们在非线性光学应用中的强大潜力。
英文摘要
Second-order nonlinear optical processes in van der Waals (vdW) semiconductors offer a compelling route toward compact, integrable photon-conversion platforms. Among III-VI vdW semiconductors, GaS is particularly attractive owing to its wide bandgap suppressing two-photon absorption under near-infrared laser excitation. However, bulk GaS typically crystallizes in the centrosymmetric $β$ phase, which eliminates second-order nonlinearity and severely limits its application in nonlinear photonics. Here, we demonstrate that GaS nanobelts synthesized via self-catalyzed vapor-liquid-solid growth predominantly crystallize in non-centrosymmetric $γ$-phase stacking. This behavior originates from edge-selective growth kinetics at the Ga catalyst interface, which stabilizes the $γ$ phase and enables deterministic in-plane dipole moment alignment. The GaS nanobelts exhibit strong second-harmonic generation (SHG) with intensities comparable to those of GaSe, a widely used nonlinear optical material. Furthermore, we integrate the nanobelts onto SiN waveguides and demonstrate efficient on-chip SHG and sum-frequency generation. These results establish $γ$-GaS nanobelts as a transferable one-dimensional nonlinear materials well suited for on-chip photonic integration and indicate their strong potential for nonlinear optical applications.
