Ultra-short laser pulse formation by parametric Raman scattering

最近，基于受激拉曼散射产生超短激光脉冲的技术受到了特别的关注。然而，到目前为止产生的谱线总数比理论预测的要少。这种现象可以用强度相关的拉曼转换引起的激光光束衍射来解释。为了抑制衍射效应，增加谱线的数目，这些谱线具有相似的强度，采用了中空纤芯光纤。这种光纤就是该方案的相互作用区域，高频倍频激发的小斯托克斯位移介质。本论文的主要工作是增加谱线的数目，在每个谱线的强度相同的情况下，消除衍射效应。利用石英中空光纤的紫外双谐波激光器，在氚分子旋转拉曼跃迁(J=0&gt；2)的共振双色激发下，产生宽拉曼-多频光谱。产生了从230到290 nm的50条纯转动拉曼谱线(其中34条谱线的强度在最强谱线的10%以内)。拉曼光谱谱线的数目与理论预测相一致。

Recently, the technology behind ultra-short laser pulse generation, based on stimulated Raman scattering, has been receiving a special interest. However, the total number of spectral line generated so far was smaller than the theoretical prediction. This behavior was explained by the laser bean diffraction caused by the intensity dependent Raman conversion.In order to suppress the diffraction effect and increase the number of Raman spectral lines, where these spectral lines have similar intensities, a hollow core fiber was employed. This fiber is the interaction region of the scheme, the high-frequency bi-harmonic excitation of small Stokes shift media. The main of this work was to increase the number of spectral lines, where the intensity of each spectral line is the same, and remove the diffraction effect.Broad Raman-multi-frequency spectra were generated from the resonant two-color excitation of the deuterium molecule rotational Raman transition (J=0>2), using ultraviolet bi-harmonic lasers with a quartz hollow fiber. Fifty pure rotational Raman spectral lines (34 lines that have intensity within 10% of the strongest spectral line) from 230 to 290 nm were generated. This number of Raman spectral lines was agreed with theoretical prediction.