Generation of ultrashort pulses in unexplored time regions and their measurement

（可见光到近红外光谱范围）我们开发了一种非共线光参量放大（NOPA）技术来产生超短可见脉冲。这些脉冲使我们能够观察和分析频率高达3000 cm^<-1>的各种实时分子振动的超快动力学。超短脉冲具有宽带频谱，因此可以在激光脉冲的整个宽带频谱中观察到实时分子振动的超快动力学，从而给出了超快动力学对探针光子能量的依赖，并阐明了其详细动力学。我们开发了一种多路（128 ch）双锁相放大器与光谱仪相结合，用于观测超短脉冲整个宽带频谱的信号。多通道锁相放大器可以同时测量所有128个探头波长，测量时间比以前缩短了128倍。快速测量，使信号的信噪比提高10倍以上，或在良好的信噪比下测量信号连续变化的参数。利用超短可见脉冲和多通道锁相放大器，我们可以在宽频带内以较好的时间分辨率观察样品的实时信号，从而可以实时解析分子振动。（真空紫外光谱范围）我们开发了一种新颖的技术，利用排列分子的高次谐波产生（HHG）在真空紫外区产生超短光脉冲。首先，我们成功地利用随时间变化的极化脉冲对排列的I_2分子中的多光子电离过程进行了最优控制。这意味着我们已经开发出最先进的技术来控制隧道电离，这是HHG的第一步。其次，我们在相同实验条件下同时观察离子产率和谐波信号的新技术，使我们第一次清楚地观察到电子德布罗意波在重组过程中的量子干涉，即从排列的CO_2分子中产生HHG的第三步。第三，我们将极化门技术应用于非绝热排列N_2分子的HHG。与我们的预期相反，我们发现当分子轴垂直于椭圆偏振的长轴时，每个谐波的光谱宽度趋于更宽。理论计算表明，我们的观测结果具有时变极化脉冲的特征。这意味着分子取向可以作为一个重要的控制参数，除了载波包络相位，当我们产生具有极化门控的少周期脉冲的阿秒脉冲。少

(Visible to near infrared spectral range)We have developed a technique of non-collinear optical parametric amplification (NOPA) to generate ultrashort visible pulses. The pulses enable us to observe and analyze ultrafast dynamics of various real-time molecular vibrations whose frequencies are up to 3000 cm^<-1>. The ultrashort pulses have broadband spectrum, therefore the ultrafast dynamics of the real-time molecular vibrations can be observed in the entire broadband spectrum of the laser pulses, which gives the dependence of the ultrafast dynamics on the probe photon energy and clarifies its detailed dynamics. We have developed a multi (128 ch) double lock-in amplifier combined with spectrometer to observe the signal in the entire broadband spectrum of the ultrashort pulses. The multi channel lock-in amplifier can simultaneously measure all of the 128 probe wavelengths, which makes the measurement time 128 times shorter than before. The quick measurement enables to increase the signal … More to noise (S/N) ratio increased more than 10 times or measure the signal continuously changing parameters in good S/N ratio. Using the ultrashort visible pulses and the multi channel lock-in amplifier, we could observe the real-time signal of the sample in broadband with a fine time resolution, which can resolve the real-time molecular vibration.(Vacuum ultraviolet spectral range)We have developed an original technique to generate ultrashort light pulses in the VUV region by using high-order harmonic generation (HHG) from aligned molecules. First, we have succeeded in the optimal control of multiphoton ionization processes in aligned I_2 molecules with time-dependent polarization pulses. This means that we have developed the most advanced technique to control tunnel ionization which is the first step of HHG. Second, our novel technique to observe both ion yields and harmonic signals under the same experimental conditions enabled us to observe the first clear evidence of quantum interference of electron de Broglie waves in the recombination process, i.e., the third step of HHG from aligned CO_2 molecules. Third, we applied the polarization gate technique to HHG from non-adiabatically aligned N_2 molecules. Contrary to our expectations based on ellipticity dependence of HHG from aligned molecules, we have found that the spectral width of each harmonic tends to be broader when the molecular axis is perpendicular to the major axis of elliptical polarization. Theoretical calculations show that our observations are characteristic of time-dependent polarization pulses. This means that molecular alignment can be used as an important control parameter in addition to the carrier envelope phase when we generate attosecond pulses with polarization gated few-cycle pulses. Less