High order harmonics from relativistic electron spikes

相対論的電子スパイクからの高次高調波

Pirozhkov, A. S.; 神門 正城; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; 河内 哲哉; 匂坂 明人; Koga, J. K.; 森 道昭; 川瀬 啓悟*; 亀島 敬*; 福田 祐仁; Chen, L.-M.*; 大東 出*; 小倉 浩一; 林 由紀雄; 小瀧 秀行; 桐山 博光; 岡田 大; 今園 孝志; 近藤 公伯; 木村 豊秋*; 田島 俊樹*; 大道 博行; Bulanov, S. V.; 西森 信行; 加藤 義章* ; Gallegos, P.*; Green, J.*; Foster, P.*; Brenner, C.*; Symes, D. R.*; Rajeev, P.*; Neely, D.*; Ahmed, H.*; Dromey, B.*; Borghesi, M.*; Ragozin, E. N.*; Coury, M.*; McKenna, P.*

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; Koga, J. K.; Mori, Michiaki; Kawase, Keigo*; Kameshima, Takashi*; Fukuda, Yuji; Chen, L.-M.*; Daito, Izuru*; Ogura, Koichi; Hayashi, Yukio; Kotaki, Hideyuki; Kiriyama, Hiromitsu; Okada, Hajime; Imazono, Takashi; Kondo, Kiminori; Kimura, Toyoaki*; Tajima, Toshiki*; Daido, Hiroyuki; Bulanov, S. V.; Nishimori, Nobuyuki; Kato, Yoshiaki*; Gallegos, P.*; Green, J.*; Foster, P.*; Brenner, C.*; Symes, D. R.*; Rajeev, P.*; Neely, D.*; Ahmed, H.*; Dromey, B.*; Borghesi, M.*; Ragozin, E. N.*; Coury, M.*; McKenna, P.*

We provide a description of experiments performed with the J-KAREN and Astra Gemini lasers where we discovered a new regime of relativistic high-order harmonic generation by multi-terawatt femtosecond lasers in gas targets. The results were explained using particle-in-cell simulations and catastrophe theory. Our work paves the way towards a bright coherent X-ray source based on compact lasers and accessible, repetitive, and debris-free gas jet targets. Such a source will be crucial for fundamental research and numerous applications requiring pumping, probing, imaging of microscopic objects and for attosecond science.