Generation And Application Of Broadband Complex Laser Chaotic Signal Based On Micro-ring Filter

In recent years,laser chaotic signal has been widely studied and developed in applications such as secure and confidential communication,high-speed random number generation,lidar,and optical time-domain interferometers due to their large bandwidth and good physical randomness.Among them,the external cavity feedback semiconductor laser has become a commonly used light source for generating laser chaotic signals due to its simple structure,easy implementation,easy module integration,and rich nonlinear dynamic characteristics when additional degrees of freedom are introduced.However,indepth research has also exposed the shortcomings of the laser itself: on the one hand,due to the relaxation oscillations caused by external optical feedback of the semiconductor laser,the spectrum of the output laser chaotic signal is uneven and the bandwidth is limited;on the other hand,since external optical feedback is a linear feedback,the output laser chaos signal implies periodicity,and this periodicity can be extracted by the autocorrelation function,delayed mutual information,and permutation entropy.The existence of these two shortcomings of laser chaotic signals severely limits its application in various fields,for example,in secure and confidential communication applications,its security is reduced and its communication rate is limited;in high-speed random number generation applications,the randomness and extraction rate of random numbers are reduced;in lidar applications,the recognition resolution and accuracy are reduced;in optical time domain interferometer applications,the measurement accuracy is reduced.Therefore,it is of great research significance to implement time delay signature suppression and bandwidth enhancement techniques for laser chaotic signals.Aiming at the shortcomings of conventional external cavity feedback semiconductor lasers,this paper uses micro-ring resonators with non-linear filtering characteristics to replace mirrors,the semiconductor laser and three types of representative structures: single-ring resonator,parallel-coupled double ring resonator,and parallel-coupled triple ring resonator are selected to form an external cavity feedback semiconductor laser,and the effects of the laser of pump current,feedback intensity,feedback delay and controllable parameters of the micro-ring resonator on the time delay signature and bandwidth of the output chaotic signal are studied in detail.The research results show that the external cavity feedback semiconductor laser based on micro-ring filtering can achieve complete suppression of time delay signature and enhancement of effective bandwidth of the laser chaotic signal in a wide range of parameter space.In addition,an external cavity feedback semiconductor laser based on a parallel coupled three-ring resonator is used as the source of random number physical entropy,and the application of the output laser chaotic signal to high-speed random number generation is studied and analyzed.The post-processing methods of single-bit random number extraction and multi-bit random number extraction achieve 3Gbit / s real-time random number generation and 200 Gbit / s offline random number generation,respectively,and all of them passed 15 tests of NIST,which verified the feasibility of this laser chaotic system for generating high-speed random numbers.