Ultra-short laser pulse formation by parametric Raman scattering

最近，基于受激拉曼散射的超短激光脉冲产生技术受到了特别的关注。然而，到目前为止产生的谱线总数小于理论预测。为了抑制衍射效应，增加强度相近的拉曼谱线数目，采用了空芯光纤作为拉曼光纤的传输线，并对空芯光纤的拉曼光谱进行了分析。该光纤是该方案的相互作用区域，对小斯托克斯频移介质进行高频双谐激发。本工作的主要内容是增加谱线数目，使谱线强度相同，并消除衍射效应，利用石英中空光纤紫外双谐波激光器，从氘分子转动拉曼跃迁（J=0>2）的共振双色激发中产生宽拉曼多频光谱。在230 ~ 290 nm范围内产生了50条纯旋转拉曼谱线（34条强度在最强谱线的10%以内的谱线）。这一数量的拉曼光谱线与理论预测一致。

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.