Generation & Optimization Of Laser Pulse In Disordered Fiber Structure

As a one-dimensional lateral disordered structure,a randomly distributed Bragg grating array is a good platform for studying low-dimensional disordered systems.Based on the random fiber laser with disordered structure,the mode competition and photon localization effects are worth discussing.The output characteristics of random lasers built on this basis,especially the pulse output and mode control,are urgently needed research directions.Under the above background,this paper studies a random fiber laser based on a disordered structure.The saturable absorption effect is used to solve the instability of the output mode,and the pulsed output of the laser is realized.Two kinds of methods are proposed to adjust output mode innovatively provides a flexible method for regulating the output of the random laser mode,and has potential application markets in optical imaging,information encoding,optical communication,and sensing.main tasks as follows:First,the coupled-mode theory and the transmission matrix method are used to numerically analyze the randomly distributed Bragg grating array;the pulse transmission characteristics in the fiber are obtained by solving the nonlinear Schrodinger equation,and the numerical model of the ring fiber laser is established;the disordered time window is added to the numerical model And discuss the impact of introducing different degrees of disorder on the pulse transmission characteristics.The theoretical analysis results show the mode competition and photon localization effect in the randomly distributed Bragg grating array.The simulation results are consistent with the subsequent experimental results.Secondly,an experimental platform of ring random fiber laser based on disordered structure was built,and the disordered output signal was obtained to verify the simulation results.A saturable absorber is introduced into the ring cavity,and the saturable absorption effect is used to stabilize the resonance mode in the cavity,and a pulse output with a repetition frequency of 5.897 MHz and a pulse width of 1.4 ns is realized.After that,two methods were used to regulate the intracavity mode.The first is to use the nonlinear polarization rotation effect,by adjusting the polarization in the cavity,to achieve three kinds of selectable repetitive frequency pulse output,and explore the effect of the pump power on the output mode,comparing the modulation produced under different pump power Q pulse and mode-locked pulse;the second method is to use a 980 nm laser to control the illumination of the random grating array.By changing the local gain of the disordered structure,the resonance mode in the cavity is changed,and 9 pulses with different repetition frequencies are realized Output.The two methods provide flexible and dynamic control methods for controlling the pulse mode and time-domain characteristics in the disordered structure,expanding the application space of random lasers as all-optical adjustable pulse light sources.