Development of an Efficient Ultrashort Optical Pulse Generator Using Modified Fabry-Perot Modulator

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We proposed a modified FP modulator and confirmed the operation. The modified FP modulator is simply formed by adding a mirror to an ordinary FP modulator at the input end. Two mirrors at the input end of the modulator forms a FP filter which is tuned to pass a input light frequency and to reflect sideband frequencies generated by the internal phase modulation.First, we developed an efficient electrooptic phase modulator at a high frequency with quasi-velocity-matching by domain inversion of an electrooptic crystal. We made an electrooptic phase modulator of an LiTaO_3 crystal at 16.25 GHz. An experiment of deep microwave modulation was carried out with the modulator. As the result, a wide FM light of almost 3 THz width was generated. The modulation efficiency was 1.6 rad/ROO<W> which is ten times greater than the efficiency of ordinary bulk modulators.Next, a modified FP modulator with a bulk electrooptic phase modulator was constructed and tested. As the result of the operation, ultr … More ashort pulses of less than 1 ps was generated. The output power of the modulator was 15 times larger than the output power of the ordinary FP modulator which is removed one input mirror from the modified FP modulator. The most important operation of the modulator was confirmed by this experiment.The pulse shape and the output power and their dependence on optical biases on the experiment was well agree with theoretical ones. To stabilize the optical biases of the cavity, we made feedback systems after a digital control method and a Pound-Drever method. The experimental result shows that the stabilizing system is necessary for practical operation and that the optical biases can be well stabilized by an ordinary electronic system.The modified FP modulator is not only a pulse generator but also a wide sideband generator. The ultimate limit of the pulse width or the sideband width is depend on the dispersion in the modulator It extends for a few tenth femtosecond and for a few tenth terahertz. This research clearly show the usefulness of the modulator in various fields. Less