Research On Theory Of Quantum-Dot Semiconductor Optical Amplifiers And The Applications In Signal Processing

The rapid growth of communication requirements in modern society makes the development of ultra-fast optical communication systems becomes the frontier of optical communication. Supported by the National High Technology Research and Development Program of China (Grant No.2009AA03Z405), the research works presented in this doctoral thesis focus on the basic theory and the applications in signal processing of quantum-dot semiconductor optical amplifiers (QD-SOAs), providing support to the key technology in ultra-fast optical communication systems. The main contents and innovative ideas are listed below:1A simplified model and a spectral model have been established and improved, for taking research on the basic theory and simulating of the applications of QD-SOAs. The traditional numerical calculating methods have been improved, leading to more accurate numerical results, and accelerated the calculating speed rapidly.2The steady state properties of QD-SOAs have been studied. Close-form solutions of the local gain and local refractive index have been given out, making possible the quantitative characterization of the steady state properties of QD-SOAs. The potential effect leading by extrinsic parameters, including inputted signal and injected currents, and intrinsic parameters, including the density of quantum dots (QDs), the inhomogeneous broadening and the spontaneous emission lifetime, has been studied basic on numerical results and close-form results. Additionally, A theoretical scheme for manufacturing QD-SOAs with flat gain spectrum has been presented.3The dynamic properties of QD-SOAs have been studied. Basic on the studying of general characters, the asynchronize of the gain dynamic and phase dynamic has been proved by numerical results and explained by physical theory. The close-form solutions of local gain dynamic, including transient response and time-delay characteristics, have been established by combining the theoretical analysis and numerical analysis, making possible the quantitative characterization of the dynamic properties of QD-SOAs. The qualitative analysis of the impact to the dynamic properties by extrinsic parameters and intrinsic parameters has been given out, and the quantitative analysis has proved that the speed of gain recovery is inversely proportional with the spontaneous emission lifetime.4The applications of QD-SOAs in ultra-fast optical switch have been studied. Compared with Bulk-SOA, which is treated as a typical traditional optical amplifier, QD-SOAs’advantages and properties in optical switches based on MZI or Sagnac ring have been analyzed. The optical switch based on QD-SOAs have been proved to be potential in ultra-fast (>100Gbit/s or even Tbit/s) optical commutation system. The optical switch base on QD-SOAs have been improved by replacing the traditional control pulses to two square signals or a square signal and an pulse signal, making the switch performance better. The properties of symmetric MZI optical amplifiers have also been analyzed by considering the couplers with different ration. The simulations and analysis indicate that optical signals transmit in opposite directions in Sagnac ring based on QD-SOAs shows different impact on the switch, comparing with on bulk-SOAs.5Ultra-fast optical wavelength conversion based on cross gain modulation (XGM) in QD-SOAs have been studied. Basic rules for choosing parameters of signals have been summarized by combing the steady state properties and dynamic properties of QD-SOAs. The power and wavelength of signals proved to be important to the extinction ratio of output signal, leading to some additional rules in corresponding applications.