Alloharmonics in Burst Intensification by Singularity Emitting Radiation

K. Ogura; M. S. Pirozhkova; A. Sagisaka; T. Zh. Esirkepov; A. Ya. Faenov; T. A. Pikuz; H. Kotaki; Y. Hayashi; Y. Fukuda; J. K. Koga; S. V. Bulanov; H. Daido; N. Hasegawa; M. Ishino; M. Nishikino; M. Koike; T. Kawachi; H. Kiriyama; M. Kando; D. Neely; A. S. Pirozhkov

arXiv · 2506.23548

Alloharmonics in Burst Intensification by Singularity Emitting Radiation

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Abstract

Burst Intensification by Singularity Emitting Radiation (BISER) in underdense relativistic laser plasma is a bright source of coherent extreme ultraviolet (XUV) and x-ray radiation. In contrast to all harmonic generation mechanisms, high-resolution experimental BISER spectra in the XUV region contain spectral fringes with separation much finer (down to 0.12 eV) than the initial driving laser frequency (~1.5 eV). We show that these fringe separations result from two main factors: laser frequency downshift (redshift) due to the quasi-adiabatic energy loss to the plasma waves, and spectral interference of different harmonic orders from different emission moments, i.e. alloharmonics [Pirozhkova et al., arXiv:2306.01018]

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K. Ogura, M. S. Pirozhkova, A. Sagisaka, T. Zh. Esirkepov, A. Ya. Faenov, T. A. Pikuz, H. Kotaki, Y. Hayashi, Y. Fukuda, J. K. Koga, S. V. Bulanov, H. Daido, N. Hasegawa, M. Ishino, M. Nishikino, M. Koike, T. Kawachi, H. Kiriyama, M. Kando, D. Neely, A. S. Pirozhkov. 2025-06-30. Alloharmonics in Burst Intensification by Singularity Emitting Radiation. https://arxiv.org/abs/2506.23548

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