Generation of short THz pulses due to modulation instability in waveguides with SrTiO3 paraelectric

It is investigated the modulation instability of transversely bounded long THz pulses in waveguides on the base of the paraelectric SrTiO
₃
at the temperatures 77 K. The cubic nonlinearity and the frequency dispersion correspond to existence of envelope solitons and the modulation instability of long input pulses, whereas in the transverse direction the instability is absent. There exists a possibility to generate the regular sequences of short THz pulses due to the modulation instability in the waveguides with SrTiO
₃
. The focusing of input long pulses reduces the threshold of modulation instability at relatively low frequencies. At higher frequencies near the soft mode frequency the regular sequence of pulses can be generated in the waveguides with optimum widths.