High Frequency (>lOGHz) Bragg-Diffraction-Type Electro-optic Deflectors Using Slant Periodic Domain Inversion.

本研究的目的是通过改进我们发明和研究的行波相位光栅器件的衍射类型，从拉曼-纳特型到布拉格型，来开发一种光学高频（>10 GHz）移相器。基于窄宽度倾斜周期畴反转技术，我们的电光（EO）晶体的器件操作已经实现了质的改进。这种新型移频器类似于声光移频器，可用于光微波接口、光波分复用通信以及科学和工业测量。我们采用20μm畴反转技术，在LiTaO_3电光晶体上设计并制作了一种新型的移频器。实验上首次证实了这种布喇格衍射型移频器的工作频率为16 GHz，转换效率为82%。此外，我们还提出了一种利用周期畴反转中反转区宽度横向变化的超快电光偏转器和平光频率梳发生器。设计并制作了两种新器件。实验结果表明，该偏转器具有亚皮秒（<1 ps）的偏转速度和32个可分辨的光斑，梳状波发生器可以产生最宽的平坦边带（0.8THz-3dB带宽）。

The purpose of this study is to develop an optical high frequency (>10 GHz) shifter by improving the diffraction type of the traveling phase grating device, which was invented and has been studied by us, from the Raman-Nath type to the Bragg type. The qualitative improvement on our device operation has been achieved based on the narrow-width slant periodic domain inversion technique to an electrooptic (EO) crystal. The target devices will be useful for an optical microwave interface, optical WDM communication, and scientific and industrial measurements.The new frequency shifter is similar to an acoustooptic (AO) frequency shifter. However, it is possible to operate in the higher frequency range (>10GHz), where conventional AO device never operates.We designed and fabricated new frequency shifter by applying 20μm domain inversion technique to LiTaO_3 electro-optic crystal. The operation of the Bragg diffraction type frequency shifter with 16GHz frequency shift arid 82% conversion efficiency was experimentally confirmed for the first time. This result is to be published on IEEE Photonics Technology Letters.In addition, we proposed anew kind of ultrafast electrooptic deflector and flat-optical frequency comb generator utilizing transversal variation of the widths of reversed areas in periodic domain inversion. Both of new devices were designed and fabricated. It was confirmed experimentally that the new deflector has subpicosecond (<1ps) deflection speed and 32 resolvable spots and new comb generator can generate the widest flat sidebands (0.8THz -3 dB bandwidth) as an external phase modulation method.