We study the generation of a self-chirped optical pulse in a free-electron laser (FEL) oscillator. In a high-gain FEL oscillator, the frequency chirp is induced in the slippage region as a result of superradiant FEL resonance, and this time-frequency correlation evolves continuously into a few-cycle regime, if the optical cavity length is perfectly synchronized to the electron bunch interval. Numerical simulations based on the slowly evolving wave approximation and experimental results are presented.
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http://dx.doi.org/10.1103/PhysRevLett.91.024801 | DOI Listing |
J Synchrotron Radiat
January 2025
LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
Time-domain modeling of the thermal deformation of crystal optics can help define acceptable operational ranges across the pulse-energy repetition-rate phase space. In this paper, we have studied the transient thermal deformation of a water-cooled diamond crystal for a cavity-based X-ray free-electron laser (CBXFEL), either an X-ray free-electron laser oscillator (XFELO) or a regenerative amplifier X-ray free-electron laser (RAFEL), by numerical simulations including finite-element analysis and advanced data processing. Pulse-by-pulse transient thermal deformation of a 50 µm-thick diamond crystal has been performed with X-ray pulse repetition rates between 50 kHz and 1 MHz.
View Article and Find Full Text PDFiScience
December 2024
Kansai Institute for Photon Science, National Institutes for Quantum Science and Technology, Kizugawa, Kyoto 619-0215, Japan.
Microbunching caused by free-electron laser (FEL) interactions in an electron bunch deforms the overall bunch shape. Recent reports indicate the timing of the electron bunch overlapping with the FEL micropulse affects deformation in resonator-type FELs. The electron bunch shape is expected to change with the FEL micropulse energy because the FEL micropulse energy is enhanced within the electron beam macropulse; however, this has not yet been investigated.
View Article and Find Full Text PDFJ Chem Phys
March 2024
Department of Chemistry, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan.
Wave packet interferometry with vacuum ultraviolet light has been used to probe a complex region of the electronic spectrum of molecular nitrogen, N2. Wave packets of Rydberg and valence states were excited by using double pulses of vacuum ultraviolet (VUV), free-electron-laser (FEL) light. These wave packets were composed of contributions from multiple electronic states with a moderate principal quantum number (n ∼ 4-9) and a range of vibrational and rotational quantum numbers.
View Article and Find Full Text PDFWith wavelength tunability, free-electron lasers (FELs) are well-suited for generating orbital angular momentum (OAM) beams in a wide photon energy range. We report here the first experimental demonstration of OAM beam generation using an oscillator FEL with the tens of picosecond pulse duration. Lasing around 458 nm, we have produced the four lowest orders of superposed Laguerre-Gaussian beams using a very long FEL resonator of 53.
View Article and Find Full Text PDFSci Rep
December 2023
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230029, China.
The generation of intense coherent radiation pulses in the far-infrared and terahertz regimes is of considerable interest to the free-electron laser (FEL) radiation user community. At long wavelengths, the diffraction effect can be quite severe, therefore, an optical waveguide is required to confine the radiation field. However, it will also bring about some new phenomena, and the most noteworthy one is the spectral gap phenomenon: at some particular wavelengths, regardless of electron beam adjustments, the coupling efficiency and output power of waveguide FEL oscillators drop significantly.
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