Study on Generation oand Control of ultrashort Optical Pulses by Electrooptic Modulation.

本研究致力于开发具有高可控性的电光超短光脉冲产生方法。取得的主要成果如下：1）利用周期域反转方案设计和改进了高调制指数的电光相位调制器/偏转器。我们成功开发了尺寸紧凑的周期域反转波导型准速度匹配电光调制器。与体型相位调制相比，高效相位调制已得到实验证实。2)提出一种新型QVM光学相位调制器，具有透镜调制功能，并将其应用于电光啁啾压缩方法，以产生无基座飞秒光脉冲。普通正弦相位调制产生两种类型的频率啁啾；向上鸣叫和向下鸣叫。因此，存在如下问题：虽然通过利用群延迟色散的线性调频压缩方法从线性调频部分之一获得了短光脉冲，但是其他线性调频部分仍然作为背景光而残留。我们的新型调制器具有透镜调制功能和相位调制功能。由于调制光束分别针对向上啁啾和向下啁啾的情况聚焦到不同的点，因此我们可以通过针孔轻松消除不需要的啁啾部分。使用该调制器，我们成功地从连续波氩激光器中生成无基座520fs脉冲。3）提出并设计了新型法布里-珀罗电光调制器，并配有用于飞秒脉冲生成的透镜调制。 （日本专利正在申请中，H10-258293，CLEG '99 即将推出）。

This study has been pursued to develop electro-optical ultrashort optical pulse generation method with high controllability. A main results obtained are as follows ;1) Design and improvement of an electrooptic phase modulator/deflector with high-modulation index using periodic domain inversion scheme.We succeeded in development of compact size waveguide-type quasi-velocity-matching electrooptic modulator with periodic domain inversion. Highly-efficient phase modulation as compared with a bulk-type one has been experimentally confirmed.2) Proposal of a novel QVM optical phase-modulator featuring lens modulation and its application to the electrooptic chirping compression method for pedestal free femtosecond optical pulse generation.Ordinary sinusoidal phase modulation generates both types of the frequency chirping ; up-chirping and down chirping. There was, therefore, a problem that although short optical pulses are obtained from one of chirping part by chirping compression method with the group delay dispersion, other chirping part still remains as background light. Our new modulator has lens modulation function as well as phase modulation function. Since modulated light beam is focused into the different point for the case of up-chirping and down-chirping, respectively, we can easily eliminate the undesirable chirping part by a pinhole. Using this modulator we succeeded in generation of pedestal free 520fs pulses from a cw Ar laser.3) Proposal and design of novel Fabry-Perot electrooptic modulator accompanied with lens modulation for femtosecond pulse generation. (Jpn Patent pending, H10-258293, CLEG '99 to be presented).