GENERATION OF MULTIFREQUENCY/ULTRASHORT OPTICAL PULSES BASED ON TWO COLOR STIMULATED RAMAN EFFECT AND ITS APPLICATION TO ANALYTICAL CHEMISTRY

本论文首先研究了基于双色受激拉曼效应产生的多频/超短激光辐射，为了实现这一目标，需要利用变换限制的飞秒激光脉冲产生高阶转动拉曼谱线，并首次证实了利用变换限制的准分子激光（248 nm，120 fs）可以产生多条转动和振动谱线。我们还详细研究了激光偏振和氢气压力的影响。另一方面，当我们使用钛宝石激光器（800 nm，200- 1000 fs）作为泵浦光时，可以专门产生40多条高阶纯转动线。这一结果意味着理论上可以产生0.4 fs的激光脉冲。然而，当脉宽减小到200 fs时，出现了较强的自相位调制和自聚焦。因此，我们必须将脉冲宽度增加到800 fs以获得上述结果。为了避免这个问题，我们可能不得不使用种子束和/或低温仲氢来增强将来的旋转线。我们还讨论了影响转动谱线产生的各种效应，并试图系统地理解飞秒区的非线性现象。在本研究中，我们还发展了一种基于自相位调制的超短激光脉冲宽度测量方法。脉冲宽度的减小，从而峰值功率的增加，增加了光谱，然后这种效应被认为是用于测量激光脉冲宽度在飞秒政权。我们还开发了一种多色激光照明工程;标准具插入染料激光腔，也是一个Nd：YAG激光器作为泵浦光，产生高功率多色激光发射，以供实际应用。

In this study, we investigated multifrequency/ultrashort laser emission generated based on the two-color stimulated Raman effect that we originally found. In order to achieve this aim, high-order rotational Raman lines should be generated by using a transform-limited femtosecond laser pulse.We first confirmed that we could generate many rotational and vibrational lines by using a transform-limited excimer laser (248nm, 120fs). We also investigated the effects of laser polarization and hydrogen pressure in detail. On the other hand, more than 40 high-order pure rotational lines could be exclusively generated when we used a Ti : sapphire laser (800nm, 200-1000fs) as a pump beam. This result implies that a 0.4-fs laser pulse can, in theory, be generated. However, strong self phase modulation and self focusing occurred, when the pulse width was reduced to 200fs. Thus we had to increase the pulse width to 800fs to obtain the above result. In order to avoid this problem, we may have to use a seed beam and/or a low-temperature para-hydrogen to enhance the rotational lines in the future. We also discussed various effects affecting the generation of the rotational lines and tried to understand the nonlinear phenomena in the femtosecond regime systematically.In this study, we also develop a method for measurements of the pulse width of the ultrashort laser emission, which is based on self phase modulation. The decrease of the pulse width, hence the increase of the peak power, increased the spectral which and then this effect was concluded to be used for the measurements of the laser pulse width in the femtosecond regime.We also developed a multi-color laser for illumination works ; an etalon was inserted in the dye laser cavity and also a Nd : YAG laser was used as a pump beam for the generation of high-power multi-color laser emission for practical use.