Abstract

Three-wave interaction of phase modulated pulses is of considerable interest in femtosecond nonlinear optics and devices. We concentrate our attention on the phenomenon of the reversal of chirp in real time and chirp enhancement due to three-wave interaction. The reversal of the chirp of light signals by four-wave parametric interaction has been earlier discussed in theoretical works /1,2/, where it was supposed to use the phase conjugation of spectral components for the compensation of phase distortions introduced by the dispersion of group velocities. The main demand for the realization of the chirp reversal is$\Delta \text{ν}\ll 1/{\text{τ}}_{ℛ}$, where ${\text{τ}}_{ℛ}$ —response time of the nonlinear interaction in the medium, Δν —frequency deviation. It is obvious, that the predominant contribution of the slow components in the third order nonlinearity limits the frequency band of chirp reversal in the isotropic media. On the other hand, three-wave parametric processes are caused by electronic nonlinearity, the response time of which is nearly a femtosecond. Thus, using χ⁽²⁾ the phase conjugation of spectral components of extremely wide optical range is possible /3/. It is needed to emphasize that broad spectral bandwidth of parametric amplification realized in a number of crystals (CDA, KDP, ect.) solve the problem of amplification of weak phase modulated picosecond signal (e. g. coming from optical fibers) for 5—6 orders and enable to obtain two phase conjugated light pulses with opposite chirps. The reversal of the chirp by parametric amplification allows to use in pulse compressors both the media with the negative as well as positive group velocities dispersion and achieve femtosecond pulses with power exceeding gigawatts. Furthemore, the phase conjugated pulses with the linear chirp open new possibilities in four-photon-phase spectroscopy, dynamic holography of space-time events, as well as in systems of optical data processing (e. g. for the formation of correlation signals).

© 1986 Optical Society of America