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Relativistic single-cycle tunable infrared pulses generated from a tailored plasma density structure


The availability of intense, ultrashort coherent radiation sources in the infrared region of the spectrum is enabling the generation of attosecond X-ray pulses via high-harmonic generation, pump–probe experiments in the ‘molecular fingerprint’ region and opening up the area of relativistic infrared nonlinear optics of plasmas. These applications would benefit from multi-millijoule single-cycle pulses in the mid- to long-wavelength infrared region. Here, we present a new scheme capable of producing tunable relativistically intense, single-cycle infrared pulses from 5 to 14 μm with a 1.7% conversion efficiency based on a photon frequency downshifting scheme that uses a tailored plasma density structure. The carrier-envelope phase of the long-wavelength infrared pulse is locked to that of the drive laser to within a few per cent. Such a versatile tunable infrared source may meet the demands of many cutting-edge applications in strong-field physics and greatly promote their development.

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Fig. 1: Illustration of photon frequency downconversion in a nonlinear plasma wake using a 3D particle-in-cell simulation showing cut-away views of wakes.
Fig. 2: The structure and output of the LWIR source.
Fig. 3: Photon frequency downconversion in a tailored plasma structure.
Fig. 4: Parameter dependence of the LWIR pulse on the plasma falling edge scale length and the drive pulse CEP.
Fig. 5: Effect of variation of plasma density on output parameters of the LWIR pulse in the converter module.

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This work was supported by the National Natural Science Foundation of China (NSFC) Grants No. 11425521, No. 11535006, No. 11475101 and No. 11775125, the National Basic Research Program of China No. 2013CBA01501, the Thousand Young Talents Program, the Air Force Office of Scientific Research (AFOSR) under award number FA9550-16-1-0139 DEF, the Office of Naval Research (ONR) Multidisciplinary University Research Initiative (MURI) (4-442521-JC-22891), the US Department of Energy grant DE-SC001006 and the Ministry of Science and Technology of Taiwan under Grant No. MOST-105-2112-M-001-005-M3. The simulations were performed on Sunway TaihuLight.

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Z.N., C.-H.P. and W.L. proposed the concept. Z.N. developed the theoretical model and carried out the simulations. Z.N., C.J., W.L. and C.-H.P. wrote the paper. All authors contributed extensively to the work presented in this paper.

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Correspondence to Chih-Hao Pai or Wei Lu.

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Nie, Z., Pai, CH., Hua, J. et al. Relativistic single-cycle tunable infrared pulses generated from a tailored plasma density structure. Nature Photon 12, 489–494 (2018).

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