Shiner A D, Trallero-Herrero C, Kajumba N, Bandulet H-C, Comtois D, Légaré F, Giguère M, Kieffer J-C, Corkum P B, Villeneuve D M
National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.
Phys Rev Lett. 2009 Aug 14;103(7):073902. doi: 10.1103/PhysRevLett.103.073902.
Using longer wavelength laser drivers for high harmonic generation is desirable because the highest extreme ultraviolet frequency scales as the square of the wavelength. Recent numerical studies predict that high harmonic efficiency falls dramatically with increasing wavelength, with a very unfavorable lambda(-(5-6)) scaling. We performed an experimental study of the high harmonic yield over a wavelength range of 800-1850 nm. A thin gas jet was employed to minimize phase matching effects, and the laser intensity and focal spot size were kept constant as the wavelength was changed. Ion yield was simultaneously measured so that the total number of emitting atoms was known. We found that the scaling at constant laser intensity is lambda(-6.3+/-1.1) in Xe and lambda(-6.5+/-1.1) in Kr over the wavelength range of 800-1850 nm, somewhat worse than the theoretical predictions.
使用更长波长的激光驱动器来产生高次谐波是可取的，因为最高的极紫外频率与波长的平方成正比。最近的数值研究预测，随着波长增加，高次谐波效率会急剧下降，具有非常不利的λ^(-(5 - 6)) 标度关系。我们对800 - 1850 nm波长范围内的高次谐波产率进行了实验研究。采用薄气体射流来最小化相位匹配效应，并且在改变波长时保持激光强度和焦点尺寸不变。同时测量离子产率，以便知道发射原子的总数。我们发现，在800 - 1850 nm波长范围内，在恒定激光强度下，Xe中的标度关系为λ^(-6.3±1.1)，Kr中的标度关系为λ^(-6.5±1.1)，这比理论预测略差。
