Theoretical Research On Integrated Broadband Chaotic Light Source Based On Dual-Mode DFB Semiconductor Laser

Chaotic laser has great application value in chaotic secure communication,high-speed random number generation,and chaotic lidar because of its wide frequency spectrum,noise-like,large amplitude and other characteristics.The external cavity feedback semiconductor laser has become the main way to generate chaotic signals due to its simple structure,easy operation,low cost,and easy integration.However,on account of the limitation of the inherent relaxation oscillation of semiconductor lasers,most of the energy is concentrated near the relaxation oscillation frequency,the spectrum is not flat and the effective bandwidth is only a few GHz,which seriously reduces the rate of chaotic secure communication and key distribution.Existing methods to increase the bandwidth of chaotic signals will increase the complexity of the system structure,and bring tough challenges to chaos synchronization.Therefore,generating broadband chaotic signals through a simple optical feedback structure is of great significance for improving the rate of secure communication and key distribution.Aiming at the above problems,this thesis proposes the research of integrated broadband chaotic light source based on dual-mode distributed feedback(DM-DFB)laser.The high-frequency beat frequency component between the two modes and the low-frequency chaotic oscillation are coupled to each other to obtain a wide-band chaotic signal with a flat spectrum.The specific work and results are as follows:1.According to the Lang-Kobayashi equations,the rate equations of the optical feedback dual-mode laser are given,and the feasibility of the broadband chaotic laser generation is theoretically verified.In addition,the influence of internal parameters and external parameters on the bandwidth of chaos is analyzed,and the range of the parameters that produce broadband chaos is given.2.The optical feedback DM-DFB laser structure is designed through VPI software,and the specific parameters are given.The path of optical feedback DM-DFB laser into chaos under long and short external cavity and high and low bias current is analyzed.Under low bias current,there will be a bifurcation cascade phenomenon from steady state to repeated chaotic oscillation under short cavity conditions.The dynamic characteristics of the high bias current are the same as that of the traditional DFB laser.3.The parameter range of broadband chaos generated by optical feedback DM-DFB laser is analyzed in the case of long cavity.Focus on the analysis of optical feedback DM-DFB laser under the condition of shorter cavity length,the influence of different feedback level and different bias current on the chaotic signal bandwidth,and the 8I_th bias current and strong feedback,the chaotic signal with a bandwidth of 37.9 GHz is generated.The complexity of the chaotic signal is analyzed by permutation entropy.Finally,a broadband chaotic entropy source was used to generate a random number with a rate of 20 GS/s,and it passed the NIST SP 800-90B randomness test.