Investigation On The Nonlinear Dynamical States Of DFB Semiconductor Lasers Subject To Dual-beam Optical Injection

With the development of optical fiber communication systems, distributed feedback semiconductor laser (DFB-SLs) has become one of the main sources of the long distance fiber communication due to its unique advantages. The related research of DFB-SLs has cause extensive concern. Especially, it can exhibit rich nonlinear dynamical behaviors including stable locking, one-period, period doubling and chaotic behavior subject to optical injection. So the research on the nonlinear characteristics of DFB-SLs under optical injection has become the focus in recent years. However, the early studies on the nonlinear dynamical behaviors of DFB-SLs subject to optical injection mainly focus on the single beam injection, the research on the nonlinear dynamical behaviors of DFB-SLs subject to dual-beam optical injection remain relatively scarce. Recently, though it has made some progress in the theoretical study of the nonlinear dynamics subject to dual-beam optical injection, the corresponding experimental observation remain relatively scarce in recent years.In this paper, the nonlinear dynamic behaviors of DFB-SLs subject to dual-beam optical injection are experimentally investigated. The results show that the outputs of a DFB-SL subject to dual-beam optical injection display much rich and more complex nonlinear dynamical behaviors compared with that of a DFB-SL subject to single-beam injection. By fixing the oscillated wavelengths of two injection optical beams and continuously changing injection strengths of two injection optical beams, the output optical spectra and power spectra of the DFB-SL under different injection strengths of dual-beam optical injection have been measured. On the basis of the optical spectra and power spectra, some typical dynamical states have been determined under three cases categorized as scenarios A, B and C. In Scenario A, the dynamic state of DFB-SLs is rich, including period one, period two, period three, period four and chaotic; in Scenario B, it mainly display nearly degenerate four-wave mixing (NDFWM); while in Scenario C, simultaneous injection of two beams allows the two dynamics to coexist and mix nonlinearly. Finally, we give the distribution map of the dynamical states of DFB-SL in the parameter space of two injection strengths,and the regions for scenarios A, B and C have been indicated.