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Title: Characterization of non-Gaussian mid-infrared free-electron laser beams by the knife-edge method
Authors: Qin, Yu
Nakajima, Takashi
Zen, Heishun  kyouindb  KAKEN_id  orcid (unconfirmed)
Wang, Xiaolong
Kii, Toshiteru
Ohgaki, Hideaki  kyouindb  KAKEN_id  orcid (unconfirmed)
Author's alias: 中嶋, 隆
Keywords: Free-electron laser
Non-Gaussian beam
Knife-edge method
M2 measurement
Issue Date: Sep-2014
Publisher: Elsevier B.V.
Journal title: Infrared Physics & Technology
Volume: 66
Start page: 146
End page: 151
Abstract: We report the characterization of mid-infrared free-electron laser (FEL) beams at the wavelength of 11 μm by the knife-edge method. From the knife-edge data we find that the FEL beam has a non-Gaussian shape. To represent the non-Gaussian beam shape we employ two methods: fitting the knife-edge data to some analytical functions with a few free parameters and numerical smoothing of the knife-edge data. Both methods work equally well. Using those data we can reconstruct the two-dimensional (2D) beam profiles at different positions around the focus by assuming that the 2D intensity distribution function is separable in x (horizontal) and y (vertical) directions. Using the 2D beam profiles at different positions around the focus, we find that the beam propagation factor (M2 factor) is ∼1.1 in both x and y directions. As a cross-check, we also carry out the burn pattern experiment to find that the behavior of the focused FEL beam along the propagation is consistent with the results obtained by the knife-edge method.
Rights: © 2014 Elsevier B.V.
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
DOI(Published Version): 10.1016/j.infrared.2014.05.021
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