Generation Of Supercontinuum In Special Fiber And Its Application In Cross-band Femtosecond Pulse Laser

Multi-wavelength synchronous coherent ultrashort pulse lasers are widely used in ultrafast science fields such as time-resolved pump detection spectroscopy,nonlinear microscopy,optical parametric amplification,and coherent pulse synthesis.The natural characteristics of the gain medium in the conventional laser limit the output wavelength span of the laser.If multiple lasers are used,the synchronization system is often very complicated,expensive or requires strict matching of the cavity length,and the sensitivity to the environment,and poor stability brings many practicalities inconvenient.This thesis studies the cross-band multi-wavelength synchronous pulsed laser.It is proposed for the first time to use supercontinuum technology to broaden the spectrum and realize the leap of the gain band.The lasers with different doping components and different gain bands are organically constructed in a single cavity to realize the synchronization and coherence of the pulsed laser and to overcome the inherent limitation of cross-band operating which traditional rare earth doped fiber lasers have.This paper mainly studies two aspects,the generation of supercontinuum of tapered fiber and the design of cross-band dual-wavelength femtosecond pulse laser.The specific work of the paper is as follows:(1)We analyzed the dispersion and nonlinear characteristics of the tapered fiber and established the numerical model of the femtosecond pulse propagation.By simulating the formation of the supercontinuum in the tapered fiber,we studied the supercontinuum generation in different regime,the influence of the relative distance between the pump center wavelength and the zero dispersion wavelength on the generation of supercontinuum.Finally,we designed the tapered fiber for the mutual conversion of pulses between 1 ?m and 1.5?m.(2)For the first time,we proposed a method of increasing the wavelength interval of Mamyshev pulse regeneration by supercontinuum broadening to realize a single-cavity cross-band dual-wavelength synchronous pulsed laser.Synchronous cross-band femtosecond pulse output in the 1?m and 1.5?m was successfully implemented in a single ring oscillator containing the process of pulse self-similar amplification,compression and supercontinuum generation by numerical simulation.(3)The stability characteristics and device parameters of the cross-band pulsed laser are analyzed and optimized by the energy transfer function.Then we concluded the guiding law of laser design.The characteristics of noise and startup of the laser were analyzed.