Wavelength Switchable Chaos Synchronization Based On Two Asymmetrical Mutually Coupled Weak-Resonant-Cavity Fabry-Perot Laser Diodes

Chaos synchronization of nonlinear coupled systems is widely used in electronic circuits,laser physics,secure communication,fluid mechanics,biochemistry and other fields.Chaos synchronization has become one of the hot research topics in nonlinear field at home and abroad in recent years.At present,the chaos synchronization based on semiconductor laser mainly focuses on the chaos output of single mode laser and its application in key distribution,chaotic secure communication and other fields.However,the rapid development of modern society has put forward higher requirements for the speed and capacity of communication systems.The multi-mode laser under external disturbance can provide multi-channel chaos carrier output and realize wavelength division multiplexing chaotic secure communication,so it has great application value in the future high speed and large capacity chaotic communication system.Weak resonator Fabry-Perot laser（WRC-FPLD）has long cavity length（600μm）and low front reflectance（1%～10%）,and has more oscillation modes in the specified wavelength range.Obviously,it is of great significance to explore the chaos signal generation and chaos synchronization of WRC-FPLD under different external disturbances and its application in wavelength division multiplexing chaotic secure communication.This thesis presents a high performance chaos synchronization scheme based on asymmetric mutual coupling WRC-FPLDs.The asymmetric mutual coupling structure can be realized by adjusting the coupling strength of two injection paths in the system respectively.Based on the rate equation of multimode lasers,we numerically investigate the effects of coupling strength,frequency detuning and internal parameter mismatch chaos on time delay characteristics（TDS）,effective bandwidth（EBW）and system synchronization characteristics.The results show that the output modes of WRC-FPLD can work in chaotic state by adjusting the coupling strength.In addition,in a large parameter space range of coupling strength and frequency detuning,the delay characteristics of chaos are kept at a small value（below 0.1）.Under certain coupling strength,appropriate positive frequency detuning is more conducive to the improvement of bandwidth.In the simulated parameter range,the bandwidth of chaos carrier can reach20 GHz.When the coupling strength of one path is fixed,the synchronization coefficient of the system increases with the increase of the coupling strength of the other path.Finally,the injection lock is reached and the synchronization coefficient remains at a high level.For fixed coupling strength,proper negative frequency detuning is helpful to improve synchronization quality,and the system can still maintain high quality chaos synchronization when the frequency detuning range is-15 GHz～12 GHz.In addition,several typical internal parameters（α,g,γ_e）are within the mismatch range of±15%,and the synchronization coefficient of the system can remain above 0.9.On this basis,we demonstrate the wavelength switchable chaos synchronization of the system,and investigate the effects of coupling strength and frequency detuning on the chaos generation and chaos synchronization characteristics of the system.The experimental results show that WRC-FPLD can simultaneously output up to 50longitudinal modes with an interval of 0.57 nm under the threshold current condition.By using the asymmetric mutual coupling structure,by changing the central wavelength of the tunable filter and the injection conditions of the two paths,different modes of WRC-FPLD can realize chaos output.With the increase of injection strength,the effective bandwidth of single channel laser chaos signal increases gradually,up to 10 GHz.Under certain conditions of asymmetric injection strength and frequency detuning,the corresponding modes of two mutually coupled WRC-FPLDs can achieve high quality laggard chaos synchronization,and the maximum correlation number C_max can reach more than 0.90.Compared with positive frequency detuning,proper negative frequency detuning is more beneficial to improve the quality of chaos synchronization when injection strength is constant.The experimental results are basically consistent with the theoretical simulation results.