Study On The Nonlinear Dynamic Behaviors Of Semiconductor Lasers

With the development of optical communication, semiconductor lasers become indispensable in long distance communication and information processing. However, due to a combination of intrinsic material related properties leading to relaxation oscillation and self-phase modulation, these lasers are very sensitive to external perturbations, and easily yield nonlinear dynamic output. It has been attended that the nonlinear dynamical characteristics of semiconductor lasers may be used in many applied fields, and have caused extensive studies. Additionally, semiconductor lasers used as a nonlinear dynamic system to investigate some inherent characteristics of lasers have gradually received considerable attention.It has been proved experimentally and theoretically that external perturbations such as external optical injection, optical feedback, current modulation and electro-optical feedback, can result in the output of semiconductor lasers to become unstable and yield oscillation or chaotic output. Prior to other methods, the external optical injection allows one to perturb the laser with an independent optical field so that the quantity of perturbation is easy to control. As an effective method to investigate the nonlinear dynamics of semiconductor lasers, external optical injection has attracted considerable attention in recent years.In this paper, the nonlinear dynamic characteristics of the distributed feedback semiconductor lasers (DFB-SL) under external optical injection have been investigated experimentally. Various nonlinear dynamic phenomena, such as stable injection locking, periodic oscillations, deterministic chaos, four-wave mixing and many other complex instabilities, are systemically observed by changing the injection optical field, and the nonlinear dynamics characteristics are mapped as a function of the power of the optical injection and the detuning frequency between the injection frequency and free-running frequency of the unperturbed DFB-SL. Experimental results show DFB-SL under external optical injection is very sensitive to external perturbation and can exhibit various nonlinear dynamical characteristics. The complex dynamics is always related to the multi-periodic dynamics. When the laser operates in the complex dynamic state, its power spectrum is continuous spectrum. By varying the parameters of injection light, it is possible to obtain various nonlinear dynamic outputs, and this is greatly valuable in investigation and application of the nonlinear dynamics of semiconductor lasers.The nonlinear dynamics of a vertical-cavity surface-emitting laser(VCSEL) with external optical injection are also studied numerically in this paper. Two situations that the polarization of the injection light is parallel or orthogonal with the solitary VCSEL output light are considered. The simulation results show the VCSEL exhibits periodic oscillations, deterministic chaos and many other complex instabilities under optical injection. However, the same injection parameters have different effects on the output of the VCSEL under parallel or orthogonal optical injection. By adjusting the injection strength or frequency detuning properly, the laser can be controlled to work at a given state, and the polarization of the VCSEL output light also can be controlled.