Ultrafast Photonics

超快光子学是光子学的前沿课题之一，是由活跃的大学研究人员组成的合作研究组织。总结了典型成果：yamashita教授提出了一种利用非线性光学效应加宽光谱产生单周光脉冲的方案；ito教授利用准相位匹配技术，利用可见激光泵浦的参数振荡器产生高效的相干太赫兹辐射；针对多波长超长距离光纤跨洋传输系统，提出了采用四波混频中路频谱转换进行色散补偿的条件；T.Kamiya对基于半导体激光的飞秒脉冲源进行了改进，并提出了一种利用非线性光纤开关的全光信号转换方案。土家先生利用射频信号注入的方法发现了锁模半导体激光器的亚谐波同步，并讨论了其在毫波光子网络中的应用。F.Koyama改进了垂直腔半导体激光器（VCSELs）的特性，特别强调了偏振稳定。noda研究了通过子带间光跃迁控制半导体量子阱的带间跃迁。利用自由电子激光泵浦，证明了超快的光开关能力。kobayashi推广了通过控制频谱来控制时间波形的思想，并讨论了不同方法的优点。

Collaborative research on ultrafast photonics which is one of the leading edge topics of photonics is organized with active university researchers as members. Typical achievements are summarized : Prof.M.Yamashita proposed a scheme of generating monocycle optical pulse by broadening optical spectra using nonlinear optical effect ; Prof.H.Ito generated efficiently coherent THz radiation via parametric oscillator pumped by visible laser using quasi-phase matching techuique ; Prof.K.Kikuchi calrified the condition of dispersion compensation usng mid-way spectral conversion by four wave mixing for the case of ultra-long distance fiber-optic trans-oceanic transmission system with multiple wavelength ; T.Kamiya improved semicoductor-laser-based femtosecond pulse source and also proposed a new all optical signal conversion scheme using nonlinear fiber-optic switch. M.Tsuchiya discovered the subharmonic synchronization of mode-locked semiconductor laser by means of rf signal injection and discussed its application to milliwave photonic network. F.Koyama improved the characteristics of vertical cavity semiconductor lasers (VCSELs), with special emphasis on polarization stabilization. S.Noda investigated the control of interband transition in semiconductor quantum wells via intersubband optical transition. Using free electron laser pump, ultrafast optical switching capability was demonstrated. T.Kobayashi extended the idea of controlling temporal waveform by the control of spectrum and discussed the merits of different apporaches.