Generation Of High Power Ultra-short Pulse Train Induced By Intensity-modulated Continuous Wave

In recent years, the application of ultra-short pulse train comes into people’s notice, at the same time the high-power ultra-short pulse train becomes more important in many areas, especially in applications of optical communications. However, limited average power and low-energy utilization limit the application of ultra-short pulse train. The average power of pulsed laser depends on the single pulse’s energy and repetition rate. As under restrictions of non-linear effects, light damage and other factors that make it is difficult to improve single pulse peak power. So increase the ultra-short pulse train repetition rate is an effective way to achieve high average power ultra-short pulse train. In this paper, we study the generation of ultra-short pulse train as well as how initial parameters affect the final output, and we have achieved the following main results:First of all, we studied the temporal structure of a supercontinuum generated under pulsed and CW pumping, analyzed the different pulse train generation method, and got the following conclusions:For Long pulse and continuous wave pumping in the anomalous dispersion region, the main factor of supercontinuum’s formation is the amplification of perturbation by modulation of instability. Because the randomness of the noise, the pulse sequence structure which has random soliton parameters can be generated, however intensity-modulated continuous wave can overcome the impact of noise, and generate the regular short pulse sequence structure.But the short pulse pumping in the anomalous dispersion region produces the regular temporal structure of short pulse sequence which repetition rate is equal to pumping frequency because of soliton fission effect. Finally for the pulse pumping in the normal dispersion region, the regular temporal structure of short pulse sequence also can be generated.Secondly, we focus on analysis of amplitude-modulated continuous wave model, for the initial, We analysis and research the intensity-modulated continuous wave’s frequency domain figure and temporal domain figure, numerical simulated the producing of ultra-short pulse train and comb-like spectrum, Then make a quantitative analysis of the high power ultra-short pulse sequence’s generation. The input parameters were studied, such as pump power, modulation depth, modulation frequency, and optical fiber parameters, including nonlinear coefficient, group velocity dispersion coefficient.High power ultra-short pulse train output characteristics were studied. In order to comprehensively consider how various parameters affect on the pumping efficiency, introduced the normalized modulation frequency. The results show that:choose a fiber with small nonlinear coefficient and large group velocity dispersion, an appropriate increase in modulation frequency and modulation depth, can ensure the high average power output, at the same time to obtain a relatively high pumping efficiency, while the smaller pump power is convenient to energy extraction.The whole process of quantification analysis helps us tor understand how did each input parameter impact on the output characteristics, the normalized modulation frequency we introduced will help us to know the relationship between each parameter and pumping efficiency, and how do we select the appropriate pumping conditions to achieve high efficiency pumping, high-power ultra-short pulse train. The study of high-power ultra-short pulse train’s generation has a certain theoretical significance.