Nonlinear dynamics of semiconductor lasers for microwave photonics applications

Semiconductor lasers are high-speed devices that can be modulated at microwave frequencies. They are also intrinsically nonlinear devices because of the fundamental dependence of the optical gain on the electron and photon densities. By introducing proper perturbations to an ordinary semiconductor laser, a variety of high-speed nonlinear dynamics can be obtained. While these dynamics are often avoided or neglected in practical applications, the goal of this dissertation is to examine the feasibility of taming these dynamics for microwave photonics applications. Two types of perturbation schemes are considered: the optical injection scheme and the optoelectronic feedback scheme. In the optical injection scheme, the laser generally exhibits oscillatory dynamics, which include the period-one and period-two oscillation states. The period-one oscillation is a state obtained by exciting the instabilities of the injected laser so that it undergoes periodic motion at a single frequency. The laser thus emits an optical carrier with a single-cycle microwave modulation. This state is applied for tunable photonic microwave generation. The microwave frequency generated can exceed the original modulation bandwidth of the laser. The photonic microwave is also analyzed for radio-over-fiber (RoF) transmission. The effect of chromatic dispersion-induced power penalty is reduced by the single sideband (SSB) property of the period-one state. Communication using frequency modulation (FM) is also demonstrated by optically controlling the microwave frequency. In addition, the period-two state is investigated using the optical injection scheme. The period-two state is a state where the laser oscillates at twice the period of the period-one state. The period-two state is obtained from the period-one state through a nonlinear dynamical period-doubling bifurcation, which generates the half-frequency from the original fundamental microwave frequency. Microwave frequency division and multiplication are demonstrated through microwave injection locking. Besides optical injection, the optoelectronic feedback scheme is also investigated. The laser is operated under the frequency locking state, where a microwave frequency comb is generated on the optical carrier. The stability is improved by adding an external microwave injection in obtaining a precise frequency comb. The overall results of this dissertation illustrate that the laser dynamics can be properly controlled for a variety of microwave photonics applications.