| Budget Amount *help |
¥6,700,000 (Direct Cost: ¥6,700,000)
Fiscal Year 1988: ¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1987: ¥3,900,000 (Direct Cost: ¥3,900,000)
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| Research Abstract |
We have developed new optical pulse generation / synthesis systems, which make it possible to control electrically optical signals in the picosecond to subpicosecond range without the limitation of the bandwidth of an electrooptic modulator. First, phase modulation with the very high modulation index is employed to produce wide optical sidebands spread over terahertz region. Then, the amplitudes and phases of sideband-components are individually controlled in the frequency space so as to from objective temporal pulse shapes. Theoretical discussions and fundamental experiments have been carried out. As results, usefulness of our synthesis systems in the picosecond range have been confirmed.
In the first research year, we developed new electrooptic phase modulators using a microstrip resonator, and achieved a modulation index of 10 rad. (sideband spread -- 640 GHz). With a pair of gratings, this modulated "CW light" was directly compressed into "a few picosecond pulses". Moreover, we deve
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loped a simple optical synthesizer using a Fabry-Perot interference filter as a sideband selector, and succeeded in generating picosecond optical pulses with 10-75GHz repetition rate.
In the 1988 year, our research proceeded to a novel optical synthesizer, which makes it possible to generate arbitrarily-shaped optical pulses. The synthesizer is composed of a spatial sideband-separator with a grating and a Fourier transform lens, a spatial sideband-controller using a spatial filter or a modulator array, and a sideband-multiplexer (just the reverse of the separator). With spatial masks to select appropriate sidebands, variously shaped pulses were obtained in the 10 ps range as predicted by the theoretical calculation. With a parabolic phase sifter (lens), we succeeded in the picosecond pulse compression. Moreover, the preliminary experiment using a liquid crystal optical shutter array was carried out to realize programmable control of picosecond pulse shapes. The possibility of a optical binary word generator with the terabit/s rates also discussed.
In conclusion, we have succeeded in developing novel type of ultrafast pulse generation / synthesis methods which are purely electrooptical and applicable to any CW/pulsed laser. Further development of this study should make it possible to realize even a femtosecond electrooptic systems. Less
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