Аннотации:
© 2019 American Physical Society. The spectrum of a cw field the phase of which experiences a periodic sawtooth modulation is analyzed. Two types of the sawtooth phase modulation are considered. One is created by combining many harmonics of the fundamental frequency. The second is produced by an electro-optic modulator fed by the relaxation oscillator, which generates a voltage slowly rising during charging of the energy storage device and dropping fast due to discharge by a short circuit. It is proposed to filter out the main spectral component of the sawtooth phase-modulated field. This filtering produces short pulses from the phase-modulated cw field. The duty cycle of this train is equal to the modulation period, while duration of the pulses depends on the rate of the phase drop. In the case of harmonics, this duration is 4N+2 shorter than the period of the fundamental frequency, where N is the number of the harmonics. In the case of the charge and discharge, duration of the pulses is close to TD/2, where TD is a drop time of the phase in the discharge period. Depending on the modulation frequency, the proposed method is capable to produce pulses with duration ranging from nanoseconds to a fraction of a picosecond.
