Generation Of Broadband Chaos In The Circular-side Hexagonal Resonator Microlaser With Optical Feedback

Recently,semiconductor lasers with external disturbances have attracted widespread attention because of their complex nonlinear dynamics.Among them,the semiconductor laser subjected to optical feedback is the widely used light source systems due to its simple configuration and easy integration.Chaotic laser possesses significant application prospects in the fields of secure communications,high-rate random number generation,key distribution and so on.However,for conventional semiconductor lasers,limited by the relaxation oscillation frequency,the chaotic signal has the problems of low frequency energy ratio and poor spectrum flatness.The commonly used electronic devices are low-pass devices,which leads to the low energy utilization of chaotic laser in practical applications.The configuration complexity of chaotic light source that increases the chaotic bandwidth is also greatly added,making chaos synchronization a tough challenge.Therefore,it is of greatly importance to generate wide-band and flat-spectrum laser chaos by simple optical feedback configuration for synchronization-based applications,such as chaos secure communication and chaos-based physical key distribution.In this thesis,we propose a method to generate broadband chaos in a circular-side hexagonal resonator(CSHR)microlaser to with optical feedback.The CSHR microlaser with the characteristics of small mode volume,high quality factor and low threshold can solve the limitation of the relaxation oscillation frequency on the bandwidth.By studying the dynamic characteristics of the CSHR microlaser,the parameter of laser chaos with wide-band flat power spectrum proved.The specific work and results are as follows:1.Based on the Lang Kobayashi equation,the theoretical model of the optical feedback CSHR microlaser is established.The dynamic characteristics of optical feedback microlaser from a short cavity to a long cavity are analyzed theoretically.Under the low bias current,the microcavity laser exhibits regular pulse package and low frequency fluctuation similar to the traditional semiconductor laser.Under the high bias current,special high frequency regular pulse package and periodic oscillation package appeared.2.Focusing on the theoretical study of the chaotic characteristics of the circular-side hexagonal microlaser under the long cavity optical feedback,the bandwidth and flatness of the chaotic power spectrum under different bias current and feedback level are analyzed.The results show that at high bias current,the low-frequency energy of the spectrum of CSHR microlaser is compensated,the relaxation oscillation is suppressed,and the chaos bandwidth is obviously increased.When the resonance peak of the modulation response is less than 3 d B,a broadband flat chaotic signal with a bandwidth of more than 14 GHz and a flatness of less than 5 d B has been generated.In addition,it is found that a laser with the wideband flat modulation response curve is expected to produce the wideband chaotic laser with the simplest optical feedback structure.