Investigation On The Nonlinear Dynamics Of A Weak-Resonant-Cavity Fabry-Perot Laser Diode Subject To Optical Injection

In recent years,with people's increasing requirements for communication capacity and communication security,the combination of wavelength division multiplexing(WDM)technology and chaotic secure communication technology has become an inevitable trend for the development of future secure communication.It can not only greatly increase the capacity of chaotic secure communication,but also facilitate the transplantation of chaotic secure communication technology into existing optical fiber communication systems to improve the security of the system.Therefore,the search for chaotic light sources that meet the requirements of WDM chaotic secure communication systems has become the key to promoting the development of large-capacity,high-security secure communication technologies.The weak resonant cavity Fabry-Perot laser(WRC-FPLD)has attracted great attention as a multimode semiconductor laser with excellent performance.Compared with the traditional Fabry-Perot laser(FPLD),the front face of the WRC-FPLD is coated with an anti-reflection coating,so the front face of the WRC-FPLD has a low reflectivity(approximately 1% ~ 10%).The front-end surface reflectivity of a conventional FPLD is generally 30%.The lower front-end surface reflectivity allows the WRC-FPLD to have a wider gain spectrum and also enables external injected light energy to be efficiently injected into the laser,while an approximately total-reflective back-end design avoids unnecessary power consumption.In addition,the length of the WRC-FPLD cavity is about 600 ?m,while that of the conventional FPLD is about 250 ?m,and the longer cavity length effectively reduces the longitudinal mode spacing.If WRC-FPLD is used as a light source in a WDM system,more channels can be provided and dense wavelength division multiplexing can be achieved.The current research also confirms that if a suitable external disturbance is introduced,the WRC-FPLD can achieve chaotic output,and the center wavelength of the chaotic signal can be tuned in a wide range,the chaos bandwidth can be controlled,and has the potential as a chaotic wave source for WDM chaotic communication.Therefore,researching the nonlinear dynamic characteristics of WRC-FPLD under external disturbances is of great significance for realizing optical chaos secure communication based on WDM technology.Based on this,the nonlinear dynamic properties of light-injected WRC-FPLD are studied experimentally,focusing on the evolutionary path of nonlinear dynamics of different modes of WRC-FPLD under external light injection in this paper.At the same time,according to the time series,power spectrum,and spectrum of “-3 mode”,“0 mode”,and “13 mode” of the three longitudinal modes measured under the external light injection in the experiment,and the nonlinear dynamical states of the modes are determined,and then the influences of external light injection on the dynamical states have been analyzed.The experimental results show that under the condition of external light injection,the three longitudinal modes of “-3 mode”,“0 mode” and “13 mode” of WRC-FPLD all of them can exhibit very rich nonlinear dynamic characteristics such as four-wave mixing(FWM),single-period(P1),quasi-periodic(QP),chaotic state(C),and stable light injection locked state(S&IL)during the experiment of changing the intensity of light injection and frequency detuning.In this process,we also observed the dynamic evolution path of the WRC-FPLD under external light injection conditions,after the quasi-periodic bifurcation to enter the chaotic state.In addition,we also plot the mappings of the dynamical states of different modes of the WRC-FPLD in the parameter space of injection strength and frequency detuning,and the light injection intensity range is 0 ?W ~ 450 ?W,and the frequency detuning range is-16 GHz ~ 16 GHz.For the different modes in WRC-FPLD,the distribution of dynamic states is also different.The results show that the chaos(C)region can be observed in both the positive frequency detuning and the negative frequency detuning region of the "0 mode" and "13 mode" of the WRC-FPLD.However,the "-3 mode" of the WRC-FPLD does not observe the chaotic state(C)in the negative frequency detuning area;the "0 mode" of the WRC-FPLD shows two separate stable light injection locked states(S&IL)areas.However,in the "-3 mode" and "13 mode" of WRC-FPLD,there is only a stable light injection locked state(S&IL)area.