ROUND-TRIP MODEL OF QUADRATIC CAVITY SOLITON TRAPPING

摘要

In recent years a considerable interest has been focused on theoretical and experimental studies of spatial dissipative structures in nonlinear optical resonators. Cavity soliton (CS) can be created and destroyed by localised pulses of light, and can thus be used to store images or information. The ability to control and manipulate CS has been proposed in the pioneering paper for the case of two-level medium. The problem of stationary soliton solution has been numerically and analytically investigated mostly in the case of the semiconductor optical resonators and cubic nonlinear cavity. Note that the quadratic non- inearity provides a wide range of new opportunities. For instance, the threshold of pattern formation in a degenerate OPO was considered. Some authors concentrate their attention on the CS interaction. The problem of soliton stability in OPO is discussed in. The most complicated case of SHG configuration with driving fieid corresponding to the fundamental frequency (FF) was studied in. It was found that the quadratic CS can appear due to modulation instability of the steady-state solution. It should be emphasized that trapping dynamics of CS is not investigated sufficiently. The authors of all papers mentioned above used the mean-field approach valid for the case of negligibly small variations of harmonic parameters in a round-trip time. However, to study spatial quadratic solitons dynamics in a long cavity with essential losses and detunings, it is necessary to develop more adequate theory than the mean-field model. For instance, it is important in the case of ring cavity considered in. In this paper we study intracavity quadratic solitons by means of numerical modelling based on the round-trip approach. In the frameworks of this model the bulk medium equations for forward and backward waves are used. In the case of stationary plane wave solution we compare the results obtained for both round-trip and mean-field models. A domain of cavity fines where the mean-field approach is valid was numerically investigated. Trapping time has been shown to decrease due to the inclination of seeded beam. The critical angle depending on the seeded beam width was obtained.