Abstract

One of the fundamental areas of laser physics, which for a long time has attracted a strong interest, is the interaction of ultra-short laser pulses with nonlinear active media. Recently, this interest has been stimulated by the fast progress in the development of techniques for generation of femtosecond laser pulses [1]. An important theoretical question in connection with this application is the discovery of solitary wave pulse structures and the concomitant analysis of their stability. A number of physical parameters, possibly obtaining in the experiment, caused a different points of view on this problem. In ref.[2] the Ginzburg-Landau equation was considered to describe additive pulse mode-locking structures and the stability of stationary pulses was investigated. This equation is the generalization of the nonlinear Shrödinger (NLS) and describes laser pulse propagation in an active medium with group velocity (GVD), gain dispersion, Kerr nonlinearity of the refractive index, and intensity dependent losses. Another extended version of the NLS equation was considered in ref.[3,4]. This equation describes a medium with broad band gain, GVD, Kerr nonlinearity, and nonlinear saturable amplification. A new dissipative optical soliton was discovered in ref.[4]. The dissipative optical solitons have a stationary intensity profile and a permanently shifting frequency, because their existence is made possible by a balance between GVD and nonlinear saturable gain. Moreover, these solitons can become trapped at the zero-dispersion point due to the self-frequency shift, if this point where the maximum of the group velocity is reached is located inside the gain band [5]. Obviously, both effects can be considered together and new solitary wave structures having the features of both additive pulse mode-locking structures and dissipative optical solitons can be obtained. However before doing this it is useful to investigate the influence of another factors on the dissipative optical solitons.

© 1995 Optical Society of America