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arXiv · 2503.08052

Phase-matching of high harmonic generation in twisted solids

Chenjun Ma·Chen Huang·Yilong You·Huazhan Liu·Zhitong Ding·Mingchao Ding·Jin Zhang·Guixin Li·Zhipei Sun·Shiwei Wu·Chaojie Ma·Enge Wang·Hao Hong·Kaihui Liu
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Abstract

High harmonic generation (HHG) in solids could enable attosecond and ultraviolet light sources with high compactness, great controllability and rich functions. However, the HHG process is accompanied by a quite large wavevector mismatch that is uncompensated by any traditional phase-matching method, directly limiting its energy conversion efficiency. Here, we propose an effective strategy for phase-matching of HHG with arbitrary harmonic orders in solids. Two flakes of solids with an interlayer twist induce a nonlinear optical phase that depends on the crystal symmetry, twist angle and harmonic order, which can be accurately designed to compensate for the phase mismatch in HHG. Guided by the twist-phase-matching theory, we achieved a record-high conversion efficiency of $~1.5\times10^{-5}$ for the fifth HHG in twisted hexagonal boron nitride crystals with a total thickness of only 1 ${\mu}m$. Our work establishes a foundation for developing ultrashort-wavelength and ultrafast-pulse laser sources in compact solid-state tabletop systems for fundamental and applied sciences.

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Chenjun Ma, Chen Huang, Yilong You, Huazhan Liu, Zhitong Ding, Mingchao Ding, Jin Zhang, Guixin Li, Zhipei Sun, Shiwei Wu, Chaojie Ma, Enge Wang, Hao Hong, Kaihui Liu. 2025-03-11. Phase-matching of high harmonic generation in twisted solids. https://arxiv.org/abs/2503.08052

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