Coherent manipulation of second-harmonic generation via terahertz-field mediated phonon-polariton in zinc oxide.

Fang, Yifei; Hao, Jiajing; Sang, Jianhua; Gao, Jixing; Song, Liwei; Tian, Ye; Li, Ruxin · Nat Commun · 2025

basic_science · Level V

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Abstract

The coherent control of phonon polaritons (PhPs) in holds transformative potential for nonlinear photonics. We demonstrate terahertz-driven excitation of low-frequency PhPs in zinc oxide (ZnO) crystals, with their nonlinear dynamics resolved via time-resolved second harmonic generation (SHG) spectroscopy. By achieving phase matching via nine sequential reflections within a millimeter-scale crystal, we observe sustained SHG oscillations with 3-4 THz modulation frequencies, achieving optimal extinction ratios of ~18 dB that persist for 90 picoseconds-a temporal span directly governed by polariton propagation dynamics. This work establishes a dual-functionality platform enabling spectral-temporal resolved mapping of quasiparticle interaction dynamics while simultaneously advancing polariton-engineered nonlinear optical modulators through symmetry-broken frequency conversion architectures.