Study On Supercontinuum Generation In Nonlinear Fibers

Tapered fibers are highly nonlinear fibers with special shapes. Ultra-short laser pulses traveling in the tapered fibers will be limited to a very small volume, followed by a large intensity. The strong interaction between laser and fiber brings about complex nonlinear effects, then the laser's spectrum is broadened, and supercontinuum (SC) is obtained. Although tapered fibers are easy to fabricate for their relatively simple shapes, they are much of significance in fundamental and applied research. This thesis is mainly focused on the tapered fibers and supercontinuum generation.The main contents of this thesis are as follows:(1) We briefly reviewed the advances in supercontinuum generation. The principles of SC generation inside the tapered fibers are introduced. The Nonlinear Schr?dinger equation (NLSE) is numerically solved. The process SC generation is simulated. The effects of dispersion, self phase modulation, self steeping, and stimulated Raman scattering on SC generation are discussed.(2) The dispersions of the tapered fibers with different fiber parameters were discussed using numerical simulation method, especially the effects of the core diameters of the tapered fibers. The effective refractive index of the taped fibers with different structures and their effects on the dispersion are calculated numerically. The influences of different nonlinear effects on the SC generation were also simulated.(3) We fabricate several tapered fibers of different parameters, and setup the coupling system for laser and tapered fiber, and generate SC with them successfully. We have characteristic of SC under different experimental parameters are analyzed. The experimental result is compared to the theoretical, and the mechanics of the SC generation is interpreted more deeply.