Development of Ultrafast Electrooptic Lens Modulator and Application to Ultrashort Optical Pulse Generation.

本文主要研究了适用于超短光脉冲产生的透镜调制器。主要研究结果如下：1）建立了高质量的畴反转技术：2）确定了透镜的相位调制功能，并优化了其设计：设计了畴反转形状，使其既能获得精确的透镜效应，又能利用LiTaO_3电光晶体实现高效的相位调制。根据上述结果制造了透镜调制器，并确认其作为高质量透镜调制器的操作。此外，我们还成功地开发了具有偏转功能的透镜偏转器。透镜调制器和透镜偏转器的驱动频率在10- 20 GHz（目前世界上最高的驱动频率）。3）超短光脉冲产生实验：利用透镜相位调制器，结合衍射光栅和狭缝，在无背景光的情况下，成功地产生了重复频率为16 GHz的500 fs超短光脉冲。此外，我们还利用透镜和狭缝的共同作用，成功地获得了2 ps的无回波脉冲序列。4）提出了一种用单模光纤代替狭缝来降低背景光的新方法。该方法利用了光纤的群速度色散特性，不需要衍射光栅。5）可应用于法布里-珀罗调制器的低插入损耗透镜调制器的研制尚未完成。

Here, we concentrated our research on the lens modulator which is applicable to the ultra-short light pulse generation. Main results of the research are shown as follows ;1) Establishment of domain inversion technology with high quality :2) Confirmation of the function of lens phase modulation and optimization of its design :The domain-inversion shapes are designed so as to obtain accurate lens effect as well as highly effective phase modulation by using LiTaO_3 electrooptic crystal. The lens modulator was produced based on the above results and confirmed its operation as a good quality lens modulator. Besides this, we succeeded in the development of the lens deflector which accompanies with the deflection function. Driving frequency of the lens modulator and the lens deflector are in the range of 10-20GHz (at present highest speed in the world).3) Experiments of ultra-short optical pulse generation :We succeeded in the generation of 500fs optical pulses with 16GHz repetition without the background light from the CW argon laser by using the lens phase modulator together with diffraction grating and a slit. Moreover, we succeeded in obtaining the 2ps pulse train without return pulses using the deflector with the effect of the lens together with the slit.4) We proposed a new method to decrease the background light by using the single mode optical fiber instead of the slit. In this method we don't need the diffraction grating because the group velocity dispersion of the fiber is utilized. Studies shown in 2)-4) have all been done at the first time in the world.5) The development of the lens modulator of the low insertion loss which could be applied to the Fabry-Perot modulator was not completed.