Coherent and ultrashort soft x-ray pulses from echo-enabled harmonic cascade free-electron lasers

Feng, Chao; Liu, Tao; Chen, Si; Zhou, Kaixiong; Zhang, Kaiqing; Zheng, Qiwen; Gu, Donghong; Wang, Zhen; Jiang, Zenggong; Li, Xuan; Wang, Baoliang; Wang, Xingtao; Zhang, Wenyan; Feng, Liqiang; Li, Chunlei; Lan, Ting; Li, Bin; Zhang, Meng; Deng, Haixiao; Xiang, Dao; Liu, Bo; Zhao, Zhentang

doi:10.1364/optica.466064

Cited by 13 publications

(15 citation statements)

References 53 publications

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“…The relatively temporal jitter between the laser pulses and the electron beam is only tens of femtoseconds at FEL facilities, e.g. ~50 fs rms at SXFEL [38]. The stable comb-like structure without obviously shot-to-shot variations had been experimental demonstrated at FERMI [44], indicating that convenient optimization methods will be feasible for the tuning of the proposed scheme.…”

Section: Simulationmentioning

confidence: 92%

Optical beat notes assisted attosecond soft X-ray pulse generation in high-gain free electron lasers

Wang

Feng²

2023

High Pow Laser Sci Eng

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Attosecond soft x-ray pulses are of great importance for the study of ultrafast electronic phenomena. In this paper, a feasible method is proposed to generate isolated fully coherent attosecond soft x-ray free electron laser via optical frequency beating. Two optical lasers with the opposite frequency chirp are used to induce a gradient frequency energy modulation, which helps to generate a gradually varied spacing electron pulse train. Subsequently, the undulator sections with electron beam delay lines are used to amplify the target ultrashort radiation. Numerical start-to-end simulations have been performed and the results demonstrate that an isolated soft x-ray pulse with the peak power of 330 GW and pulse length of 620 as can be achieved by the proposed technique.

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Section: Simulationmentioning

confidence: 92%

Optical beat notes assisted attosecond soft X-ray pulse generation in high-gain free electron lasers

Wang

Feng²

2023

High Pow Laser Sci Eng

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“…The duration of the FEL pulse from the first stage is about 85 fs (FWHM) for the 0-fs time delay case, and around 58 fs (FWHM) for the 60-fs and 133-fs delay cases, as shown in Figure 4D. The FEL pulse durations from RAD2 will further be shortened due to the pulse shortening effect [49][50][51]. The final pulse duration for the 0-fs time delay is about 57 fs (FWHM), for the 60-fs time delay is about 41 fs (FWHM), and for the 133-fs time delay is about 25 fs (FWHM), as shown in Figure 4E.…”

Section: Experiments At the Soft X-ray Freeelectron Laser Test Facilitymentioning

confidence: 94%

“…The results of the experiments are shown in Figures 4D,E. We have reconstructed the normalized FEL radiation profiles with the relative time delay 0 fs, 60 fs, and 133 fs [48,49]. The power profiles shown in Figure 4D correspond to the first-stage EEHG, while Figure 4E corresponds to the second-stage HGHG.…”

Section: Experiments At the Soft X-ray Freeelectron Laser Test Facilitymentioning

confidence: 99%

Few-femtosecond X-ray pulse generation and pulse duration control in a seeded free-electron laser

Fan

Zheng²,

Feng³

et al. 2023

Front. Phys.

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With the development of ultrafast science, free-electron lasers (FELs) with ultrashort pulses have become a state-of-the-art tool in ultrafast phenomena studies. In an externally seeded FEL, the output pulse duration is usually determined both by the seed laser pulse duration and FEL amplification process, which can hardly reach the timescale of a few femtoseconds. In this study, through a simple method of changing the relative time delay and correspondingly the pulse energy of the two seed lasers employed in a seeded FEL, we demonstrated the possibility of generating few-femtosecond soft X-ray pulses and controlling the final FEL pulse durations. Based on theoretical calculations and practical experiments, we conducted a detailed study on the capabilities and limitations to this method with the parameters of the Shanghai Soft X-ray FEL Facility. Start-to-end simulations indicate that we can achieve ultrashort soft X-ray FEL pulses with the pulse duration down to 5.2 fs, and the final pulse durations can also be controlled in terms of relative time delays.

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“…The SXFEL-UF is aimed at generating soft X-ray pulses toward the water window around 2.3 to 4.4 nm, which contains the SASE and the seeding beamlines. 49,50 The baseline design initially considers the single-stage EEHG and the cascaded EEHG-HGHG configurations. A 266-nm seed laser with a peak power of several hundred megawatts and a repetition rate of 10 Hz is adopted.…”

Section: Toward High Repetition Ratesmentioning

confidence: 99%

High-repetition-rate seeded free-electron laser enhanced by self-modulation

2023

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The spectroscopic methods for the ultrafast electronic and structural dynamics of materials require fully coherent extreme ultraviolet and soft X-ray radiation with high-average brightness. Seeded free-electron lasers (FELs) are ideal sources for delivering fully coherent soft X-ray pulses. However, due to state-of-theart laser system limitations, it is challenging to meet the ultraviolet seed laser's requirements of sufficient energy modulation and high repetition rates simultaneously. The self-modulation scheme has been proposed and recently demonstrated in a seeded FEL to relax the seed laser requirements. Using numerical simulations, we show that the required seed laser intensity in the self-modulation is ~3 orders of magnitude lower than that in the standard high-gain harmonic generation (HGHG). The harmonic self-modulation can launch a singlestage HGHG FEL lasing at the 30th harmonic of the seed laser. Moreover, the proof-of-principle experimental results confirm that the harmonic self-modulation can still amplify the laser-induced energy modulation. These achievements reveal that the self-modulation can not only remarkably reduce the requirements of the seed laser but also improve the harmonic upconversion efficiency, which paves the way for realizing high-repetitionrate and fully coherent soft X-ray FELs.

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Coherent and ultrashort soft x-ray pulses from echo-enabled harmonic cascade free-electron lasers

Cited by 13 publications

References 53 publications

Optical beat notes assisted attosecond soft X-ray pulse generation in high-gain free electron lasers

Optical beat notes assisted attosecond soft X-ray pulse generation in high-gain free electron lasers

Few-femtosecond X-ray pulse generation and pulse duration control in a seeded free-electron laser

High-repetition-rate seeded free-electron laser enhanced by self-modulation

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