Generation and Dynamics of Optical Dissipative Soliton

Abstract

Optical fi ber based laser has emerged as a big contender in industrial as well as experimental laser. Their performance can be improved by employing the concept of soliton. This thesis presents theoretical investigations on the generation, stability and interaction of optical dissipative solitons in semiconductor doped fiber laser cavity under the influence of various higher order nonlinear and dispersive effects. The soliton conditions are established and the roles of the dispersive as well as nonlinear effects on the dissipative solitons are found using a variational method based analytical approach. The analytically results are veri fied by split-step Fourier method based numerical approach. Phase controlled and temporal separation controlled soliton switching are investigated through interaction of two dissipative solitons. Optical dissipative soliton is generated in a lossy fiber with cubic-quintic nonlinearity, multi-photon absorption and gain dispersion. Rayleigh's dissipative function in conjugation with variational method is used to analytically solve the governing complex cubic-quintic Ginzburg-Landau equation and validated numerically. Impacts of two photon and three photon absorptions that arise due to positive imaginary parts of third and fifth order susceptibility respectively are found to be detrimental on the pulse as well as soliton. The negative imaginary part of fifth order susceptibility may lead to three photon emission, which provides an alternative gain mechanism for the stable dissipative solitons, provided that it is not too strong, to avoid the onset of the blowup. Real fibers may feature a variety of imperfection like shape variation, inhomogeneous refractive index and dopant concentration, bending effects etc. These effects are random in nature and manifest themselves through random variations of the group velocity dispersion. Dissipative solitons are generated in such random dispersive optical fiber laser cavity with cubic-quintic nonlinearity, multi-photon absorption and gain dispersion. They also remain stable under the action of perturbation in the form of the random dispersion as well as noise. The dissipative solitons generated in both random and non-random environment are bistable, with two different pulses, low- and high-amplitude ones, found for a given width. In the presence of the nonlinear gain,the low-amplitude dissipative soliton is stable, while its high-amplitude counterpart is subject to the blowup instability. Interactions between the dissipative solitons lead to fusion of high-amplitude solitons into breathers, and periodic merger-splitting sequences for low-amplitude ones. Relative-phase-controlled switching is obtained by the interaction of two dissipative solitons. Dispersion management, a technique for soliton stabilization is used for generation of dissipative soliton in a fiber laser cavity with cubic-quintic nonlinearity, multiphoton absorption and gain dispersion. Each of the anomalous and normal fiber segments of the dispersion map is having some random dispersion fluctuation. The dispersion-managed dissipative breather solitons are robust against certain level of noise. Soliton switching between low to high speed regime is achieved by varying the temporal separation as well as relative phase between the dispersion-managed dissipative solitons. Due to the ultrashort duration, dissipative solitons in ber laser cavities are subject to higher order dispersion and nonlinear perturbations, particularly, third order dispersion and intrapulse Raman scattering. Stable dissipative solitons are generated in such systems. Roles of the perturbations on dissipative solitons are shown in a doped fi ber cavity with cubic-quintic nonlinearity, multi-photon absorption and gain dispersion. The results reported in the thesis suggest new experiments on dissipative soliton fi ber laser and dispersion-managed dissipative soliton laser, all-optical switching devices, all-optical data processing and all-optical delay lines.