Study On Femto-Second Pulse Propagation And Supercontinuum Generation In Tapered Fibers

Up to now, researches on nonlinear effects of ultra-short laser pulse propagation in fibers and supercontinuum generation have become an important branch of nonlinear fiber optics. Supercontinuum is very useful in the field of spectroscopy, optical-metrica, biomedicine and modern optical communication.In this paper we introduced the history of the supercontinuum and the recent results about it and demonstrated the advantages of using tapered fibers for supercontinuum generation.In this paper we discussed the relevant effects when the pulses propagate in tapered fibers and how the supercontinuum generated. We also discussed the influence of dispersions, including Grouped Velocity Dispersion (GVD) and Third Order Dispersion (TOD), and the nonlinear effects, including Self Phase Modulation (SPM), Self Steeping (SS), and Stimulated Raman Scattering (SRS) on the supercontinuum generation. The dispersion characteristics is an important factor when the supercontinuum generated, so this paper discussed the dispersion of the tapered fiber deeply. The influence of some factors on the supercontinuum generation was demonstrated, such as the peak power of the pulses, the length of the fiber and so on. Finally, we gave the numerical simulation results of the supercontinuum under the all effects during the ultrashort pulses propagating in the tapered fiber.The experimental system was introduced, including the ultrashort pulse generation system, the isolator system, the coupling system and the spectra measurement system in details.The experiment results are shown by using tapered fibers and photonic crystal fibers when changing the experiment parameters, such as pulse power, pulse central wavelength and the length of the fiber. Compared the theoretical analysis with the experimental results, the contribution of the SRS effect to the generation of supercontinuum is discussed in details and gave some good results.