Abstract
Beyond the investigations on high-order harmonics generation (HHG) from gaseous media, people have experimentally proved the HHG from solid state in 2011 [1]. Such a highly nonlinear nonperturbative phenomenon in solid-state paves a new way to obtain extreme ultraviolet (EUV) coherent light sources and investigate the ultrafast electronic dynamics in condensed phase [2]. Here, in our experiment, we have observed a special phenomenon in HHG: the spectral interference of high harmonics. Our experiment results show that this interference is relevant to the propagation effect, the carrier-envelope phase (CEP) of ultrashort driving pulses, and the sample thickness. Combining with the simulation based on two-band semiclassical model [3] and the semiconductor Bloch equations [4], the CEP dependence on the emergence of this interference is partially explained. In addition, using the spectral broadening method, we succeeded in obtaining ~ 20 fs laser pulses from ~ 240 fs long input laser pulses. We are hopeful that these short laser pulses would allow us to explore dynamical processes in condensed matter in higher fidelity.
Reference:
[1] Ghimire Shambhu, et al. Observation of high-order harmonic generation in a bulk crystal. Nat Phys., 7:138–141 (2011).
[2] Chao Yu, et al. High order harmonic generation in solids: a review on recent numerical methods. Adv. Phys. X, 1562982, Vol 4 (2019).
[3] M. W. Feise, and D. S. Citrin. Semiclassical theory of terahertz multiple-harmonic generation in semiconductor superlattices. Appl. Phys. Lett., 75, 3536 (1999).
[4] Tran Trung Luu, et al. High-order harmonic generation in solids: A unifying approach. Phys. Rev. B, 94, 115164 (2016).
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