Femtosecond Optical Pulse Generation Using Laser Diodes

本研究的目的是研制一种响应飞秒光脉冲的高度非线性器件，并寻找一种光脉冲单环化的方法来突破目前最短的脉冲。本文的研究成果总结如下：1.研究成果。通过对掺Ge和掺Er：Ge的石英光纤中飞秒光脉冲的非线性传输实验，首次计算了它们的非线性折射率和响应时间。其非线性折射率是石英光纤的数倍，响应时间在几飞秒的范围内。利用外差探测技术搭建了一台高灵敏度的飞秒时分干涉仪。利用该干涉仪，我们测量了高掺铅二氧化硅光纤中的非线性折射率，其大小约为二氧化硅光纤的十倍。飞秒光脉冲在有机晶体芯…中非线性传输的数值计算增加了响应时间为30fS的光纤。通过计算发现，延迟响应对脉冲压缩的影响可以通过三阶相位调整来补偿。利用时分干涉仪，首次高精度地测量了二硫化碳非线性折射率变化的两个分量(平行和垂直)。我们根据衰减时间常数将每个分量分解为三个贡献。提出了一种基于短光纤中三个同步飞秒脉冲互感位相调制产生超宽带光脉冲(宽度为550 THz)的方法。这些具有等距载波频率和恒定载波相位差的脉冲是从基波、二次谐波和二次谐波脉冲泵浦的参数波中获得的。计算机分析表明，利用空间位相调制器可以补偿光纤输出端合成波的啁啾，并产生1.76个周期的脉冲。较少

The purpose of our study is to develop a highly-nonlinear device responding to femtosecond optical pulses and to find a method for optical pulse monocyclization to break through the present shortest pulse. Results of our study are summarized as follows.1. From the femtosecond optical pulse nonlinear propagation experimetnt in germanium oxide or erbium : germanium oxide doped silica fibers, we first evaluated their nonlinear refractive indices and response times. The nonlinear refractive indices are several times larger than that of a silica fiber and the response times are in a range of a few femtoseconds.2. We built up a highly sensitive femtosecond time-division interferometer using a heterodyne detection technique. With this interferometer, we evaluated the nonlinear refractive index in a highly lead oxide doped silica fiber to be about ten times larger than that of a silica fiber.3. Numerical calculation of femtosecond optical pulse nonlinear propagation in an organic crystal-cored … More fiber whose response time is 30 fs was performed. From this calculation, it was found that the influence of the delayd response on pulse compression can be compensated for by the third-order phase adjustment.4. Using a time-division interferometer, we first measured two (parallel and perpendicular) components of nonlinear-refractive-index change in carbon disulfide with high accuracy. We decomposed each component into three contributions based on decay time constants.5. An approach for generation of an ultrabroad-band optical pulse (550 THz width) is proposed, which is based on mutual induced phase modulation of three synchronized femtosecond pulses in a short fiber. These pulses having equidistant carrier frequencies and constant carrier-phase differences are obtained from the fundamental, the second-harmonic and the second-harmonic-pulse pumped parametric waves. Computer analysis shows that chirp of the composite wave at the fiber output can be compensated for by a spatial phase modulator and a 1.76-cycle pulse is generated. Less