A self-similarity approximation model for three-wave resonant interaction in transient backward stimulated Raman scattering (BSRS) was derived. Interestingly, as its asymptotic solution, the train of solitary backward Raman pulse train is possibly formed. This result can be considered as an increment of “single” solitons observed previously. | Communications in Physics, Vol. 25, No. 3 (2015), pp. 275-282 DOI: APPEARANCE OF AN ENSEMBLE SOLITARY PULSE TRAIN IN TRANSIENT BACKWARD STIMULATED RAMAN SCATTERING NGUYEN MANH THANG Academy of Military Science and Technology, Hanoi, Vietnam E-mail: thangnm@ Received 25 August 2015 Accepted for publication 29 September 2015 Abstract. A self-similarity approximation model for three-wave resonant interaction in transient backward stimulated Raman scattering (BSRS) was derived. Interestingly, as its asymptotic solution, the train of solitary backward Raman pulse train is possibly formed. This result can be considered as an increment of “single” solitons observed previously. Keywords: solito ns, backward Raman scattering, self-similarity. I. INTRODUCTION Optical solitons is one of the most intriguing subjects in nonlinear optic interactions. Normally, it can be divided into two main branches. The first one results from an exact cancellation between self-phase modulation and group velocity dispersion [1]. This type has been widely studied in both theory and experiment in dispersive media [2–5]. Another one is determined by the balance between energy exchange rates of dispersionless waves of different velocities in threewave resonant interaction [6, 7]. This structure is ubiquitous in various branches of science as plasma solitons [8–10], optical parametric solitons [11–13], stimulated backward Brillouin scattering [14, 15], solitons in forward stimulated Raman scattering (FSRS) [16–18]. Soliton in backward stimulated Raman scattering (BSRS) was theoretically predicted in 1969 [19] and observed recently in gas filled hollow-core photonic bandgap fibres (HC-PBG) [20]. In this paper, we take advantage of a self-similarity approximation solution analogous to that of transient FSRS to order to consider the transient BSRS interaction problem. The finding solution results in an appearance of the solitary backward Raman pulse train moving
