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

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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.