2025/04/24 by Xiaoyu Bu, Song, Xinru, Xiaohui Zhao +7
Physics and Astronomy · #Advanced Fiber Laser Technologies #Atomic Physics (physics.atom-ph) #FOS: Physical sciences #Laser-Matter Interactions and Applications #Quantum optics and atomic interactions
paper · pdf · doi:10.48550/arxiv.2504.17335
openalex publication_date 2025/04/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We theoretically investigate high-order harmonic generation (HHG) and its ellipticity in gapped graphene, driven by a femtosecond short-pulse laser at various orientation angles, employing the two-band density-matrix equations within the tight-binding approximation. The orientation-dependent harmonic spectra exhibit pronounced enhancement of specific harmonics, which we attribute to the caustic effect. Using the recombination trajectory model, we reveal that the orientation dependence of these enhanced harmonics originates from the distinct band structures encountered by electrons ionized from the two inequivalent \textrmK points. Moreover, we focus on the ellipticity of the enhanced harmonics at specific angles and demonstrate that it primarily depends on the phase difference between the parallel and perpendicular components, which can be accurately predicted by our recombination trajectory model. Based on these insights, we propose a two-color (fundamental plus second-harmonic) field scheme to generate isolated elliptically polarized attosecond pulses (IEAPs) in gapped graphene. Our findings may provide a promising pathway toward the generation of IEAPs in gapped graphene or transition metal dichalcogenides.