近日，美国哥伦比亚大学的P. James Schuck&Julius Mildenberger及其研究小组与意大利米兰理工大学的Giulio Cerullo等人合作并取得一项新进展。他们对周期极化层状半导体中的准相位匹配上转换和下转换进行了研究。相关研究成果已于2025年1月13日在国际知名学术期刊《自然—光子学》上发表。
该研究团队实现了一种周期性极化的范德华半导体（3R-MoS2）。由于其具有较大的非线性，研究人员在3.4微米（即3个极化周期）的微观厚度下，在相关的通信波长处实现了0.03%的宏观频率转换效率，这比具有相似性能的当前系统薄了10至100倍。由于内在腔效应，厚度依赖的准相位匹配二次谐波信号超过了通常的二次增强50%。
此外，研究人员还通过准相位匹配的自发参量下转换在通信波长处宽带生成光子对，显示出的最大符合-偶然计数比为638±75。这项工作开辟了利用微观范德华晶体进行相位匹配非线性光学这一全新且未探索的领域，为需要简单、超紧凑技术的应用解锁了可能性，例如用于集成量子电路和传感的片上纠缠光子对源。
据悉，非线性光学是经典光和量子光产生的核心。周期性极化技术的发明彻底改变了非线性光学及其商业应用，使在铌酸锂等晶体中实现稳健的准相位匹配成为可能。然而，要达到有用的频率转换效率，需要宏观的尺寸，这限制了技术的进一步发展和集成。
附：英文原文
Title: Quasi-phase-matched up- and down-conversion in periodically poled layered semiconductors
Author: Trovatello, Chiara, Ferrante, Carino, Yang, Birui, Bajo, Josip, Braun, Benjamin, Peng, Zhi Hao, Xu, Xinyi, Jenke, Philipp K., Ye, Andrew, Delor, Milan, Basov, D. N., Park, Jiwoong, Walther, Philip, Dean, Cory R., Rozema, Lee A., Marini, Andrea, Cerullo, Giulio, Schuck, P. James
Issue&Volume: 2025-01-13
Abstract: Nonlinear optics lies at the heart of classical and quantum light generation. The invention of periodic poling revolutionized nonlinear optics and its commercial applications by enabling robust quasi-phase-matching in crystals such as lithium niobate. However, reaching useful frequency conversion efficiencies requires macroscopic dimensions, limiting further technology development and integration. Here we realize a periodically poled van der Waals semiconductor (3R-MoS2). Owing to its large nonlinearity, we achieve a macroscopic frequency conversion efficiency of 0.03% at the relevant telecom wavelength over a microscopic thickness of 3.4μm (that is, 3 poling periods), 10–100× thinner than current systems with similar performances. Due to intrinsic cavity effects, the thickness-dependent quasi-phase-matched second harmonic signal surpasses the usual quadratic enhancement by 50%. Further, we report the broadband generation of photon pairs at telecom wavelength via quasi-phase-matched spontaneous parametric down-conversion, showing a maximum coincidence-to-accidental ratio of 638±75. This work opens the new and unexplored field of phase-matched nonlinear optics with microscopic van der Waals crystals, unlocking applications that require simple, ultra-compact technologies such as on-chip entangled photon-pair sources for integrated quantum circuitry and sensing.
DOI: 10.1038/s41566-024-01602-z
Source: https://www.nature.com/articles/s41566-024-01602-z