Study On Dynamic Characteristics Of Random Laser Based On Random Distributed Grating Array

Fiber-optic random laser is one of the most important research hotspots in the random laser field in recent years.It attracts the attention of many researchers with the advantages of high pumping efficiency,high directionality,and low manufacturing cost.Fiber random lasers based on randomly distributed grating arrays(RD-FBG)as coherent random feedback lasers.The random lasing mode generated in RD-FBG is a difficult and hot topic in current research.Many researchers have done a lot of experiments,theories and applications on it,and in addition,the modulation response characteristics of such lasers(like Domain dynamics and frequency-domain resonance modes)are also issues worthy of further study.This is of great significance for regulating the operating characteristics of such lasers and expanding their application fields.In this thesis,RD-FBG is used to construct a fiber-optic random laser.The periodic modulation signal is introduced by the electro-optical modulator(EOM)to study the random lasing mode.The electro-optical effect is used to adjust the cavity loss,and the random lasing mode is used to analyze the periodic modulation.Response characteristics of the signal,analysis of random laser cavity mode selection and stability of the feasibility.First,we studied 20 FBG-structured RD-FBGs.Experiments have found that the introduction of EOM helps to suppress the instability of the output time domain and facilitates the generation of periodic time-domain pulses when the frequency of the modulation signal(sinusoidal waveform)is in the range of 50-200 MHz.When continuously changing,a significant modulation response output can be obtained over a wide frequency range.Subsequently,we compared the single-frequency signal modulation response characteristics of a random laser fed by a single FBG-backed conventional laser,five FBG-constructed RD-FBG,and twenty FBG-constructed RD-FBG random lasers.The existence of resonance modes includes:one is the low-frequency oscillation mode within the entire large ring cavity laser,the other is the high-frequency oscillation localization mode existing in the RD-FBG.At the same time,the effects of these different resonance mechanisms under the above three feedback conditions are analyzed.Finally,we replaced single-frequency signal modulation with dual-frequency signal modulation.In order to facilitate the data collection,we have set up an instrument automatic control and data acquisition system based on Labview environment to realize the continuous automatic frequency conversion output of the modulated signal.Based on this,the modulation effect of the dual-frequency signal on the proposed random laser is studied.The final experimental results show that although the intensity of the time-domain waveforms of the 20 FBG lasers at the resonant frequency is less than that of a single FBG,its modulation bandwidth is wider than that of a single FBG;the dual-signal modulation can simultaneously The two different modes start to vibrate,but also disperse the photon energy whose cavity population number is reversed.Only when the frequency of the two signals is in a multiple relationship,and the frequency is exactly the cavity resonance frequency,there can be higher modulation.