Alessandra Di Gaspare,Sara Ghayeb Zamharir,Craig Knox,Ahmet Yagmur,Satoshi Sasaki,Mohammed Salih,Lianhe Li,Edmund H Linfield,Joshua Freeman,Miriam S Vitiello
{"title":"Second and third harmonic generation in topological insulator-based van der Waals metamaterials.","authors":"Alessandra Di Gaspare,Sara Ghayeb Zamharir,Craig Knox,Ahmet Yagmur,Satoshi Sasaki,Mohammed Salih,Lianhe Li,Edmund H Linfield,Joshua Freeman,Miriam S Vitiello","doi":"10.1038/s41377-025-01847-5","DOIUrl":null,"url":null,"abstract":"High-order harmonic generation (HHG) in solids-the frequency up-conversion of an optical signal-is governed by symmetries. At terahertz (THz) frequencies, HHG is a key technology to access high-frequency spectral windows that are usually difficult to cover using conventional solid-state laser technologies. This effect has been recently exploited in graphene, where HHG has been demonstrated, albeit only at odd multiples of the driving frequency owing to its inherent centro-symmetry. In topological insulators (TIs), the combination of spin-orbit interaction and time-reversal symmetry create an insulating bulk state with an inverted band order, inseparably connected with conducting surface states. TIs have been predicted to support unconventional high harmonic generation from the bulk and topological surface, which are usually difficult to distinguish. However, no experimental results have been reported, so far. Here, we exploit the strong optical field amplification provided by an array of single or double split ring resonators, with embedded Bi2Se3 or (InxBi(1-x))2Se3/Bi2Se3 Van der Waals heterostructures, to achieve up-conversion in the 6.4 (even)-9.7 (odd) THz frequency range. This results from bulk centro-symmetry (odd states) and symmetry breaking in the topological surface states (odd and even).","PeriodicalId":18069,"journal":{"name":"Light-Science & Applications","volume":"18 1","pages":"337"},"PeriodicalIF":23.4000,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Light-Science & Applications","FirstCategoryId":"1089","ListUrlMain":"https://doi.org/10.1038/s41377-025-01847-5","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"OPTICS","Score":null,"Total":0}
引用次数: 0
Abstract
High-order harmonic generation (HHG) in solids-the frequency up-conversion of an optical signal-is governed by symmetries. At terahertz (THz) frequencies, HHG is a key technology to access high-frequency spectral windows that are usually difficult to cover using conventional solid-state laser technologies. This effect has been recently exploited in graphene, where HHG has been demonstrated, albeit only at odd multiples of the driving frequency owing to its inherent centro-symmetry. In topological insulators (TIs), the combination of spin-orbit interaction and time-reversal symmetry create an insulating bulk state with an inverted band order, inseparably connected with conducting surface states. TIs have been predicted to support unconventional high harmonic generation from the bulk and topological surface, which are usually difficult to distinguish. However, no experimental results have been reported, so far. Here, we exploit the strong optical field amplification provided by an array of single or double split ring resonators, with embedded Bi2Se3 or (InxBi(1-x))2Se3/Bi2Se3 Van der Waals heterostructures, to achieve up-conversion in the 6.4 (even)-9.7 (odd) THz frequency range. This results from bulk centro-symmetry (odd states) and symmetry breaking in the topological surface states (odd and even).
固体中的高次谐波产生(HHG)——光信号的频率上转换——是由对称性控制的。在太赫兹(THz)频率下,HHG是一项关键技术,可以进入传统固态激光技术通常难以覆盖的高频光谱窗口。这种效应最近在石墨烯中得到了利用,HHG在石墨烯中得到了证明,尽管由于其固有的中心对称性,只有驱动频率的奇数倍。在拓扑绝缘体(TIs)中,自旋轨道相互作用和时间反转对称性的结合产生了具有倒带序的绝缘体态,与导电表面态不可分割地联系在一起。它已经被预测支持从体和拓扑表面非常规高谐波产生,这通常难以区分。然而,到目前为止,还没有实验结果的报道。在这里,我们利用嵌入Bi2Se3或(InxBi(1-x))2Se3/Bi2Se3 Van der Waals异质结构的单或双分裂环谐振器阵列提供的强光场放大,在6.4(偶数)-9.7(奇数)太赫兹频率范围内实现上转换。这是由于体中心对称(奇态)和拓扑表面态(奇偶态)的对称性破缺。