Use of phase-locking in four-wave Raman mixing for generating ultrashort optical pulses

Abstract
The intensities of high-order rotational Raman lines are calculated by computer simulation in the approximation of time-independent plane-wave pumping based on the currently accepted model used in studies of four-wave Raman mixing (FWRM). When the phases of the rotational lines are assumed to be slightly random, the intensities are drastically decreased. Such reduction in intensity becomes more serious with increasing phase distortion, indicating that the emission lines generated by FWRM requiring phase matching are coherently phased. In other words, phase matching is equivalent to phase locking or mode locking in FWRM. These results suggest that FWRM has potential for use in generating ultrashort optical pulses shorter than 1 fs.