Design And Performance Optimization Of All-optical Logic Gates Based On Photonic Crystals For Binary-Phase-Shift-Keyed Signals

The communication network will develop toward the all-optical network in the future. All-optical logic devices are key components in all-optical addressing identification, optical packet switching, photonic computation and other high speed and large capacity all-optical signal processing. The research and application of photonic crystal devices lay the foundation of the realization of large-scale integrated optics. Photonic crystal integrated material can build all optical logic devices which have low power consumption, high contrast, high transmission rate and are ease of integration. Adopting optical phase modulated signals in future high-speed and long-haul optical communication systems may increase the bandwidth efficiency and support longer transmission distance.Therefore, the research about all-optical logic devices in photonic crystal for optical phase modulated signals is of great significance. This project thesis first proposed several all-optical logic device structures in photonic crystal for optical phase modulated signals. The optimized design and performance Analysis of these all-optical logic devices have been studied in the meantime. The thesis mainly finished the following work.First part is about design all-optical XOR/XNOR logic gate for optical phase modulated signals and the application of genetic algorithm to optimize a all-optical XOR/XNOR logic gate. Writing a genetic algorithm coded by C++,the optimization of the triangular lattice all-optical XOR/XNOR logic gate in a two-dimensional photonic crystal for optical phase modulated signals was realized. Though iterative optimization, the optimal radius r1 of Si rods at both ends of the multimode waveguide were obtained. A square lattice all-optical XOR/XNOR logic gate in a two-dimensional photonic crystal for optical phase modulated signals is presented. Optimized design was also done to this square lattice all-optical XOR/XNOR logic gate.The simulation results calculated by MEEP indicated that in the C-band (1530-1565nm) the logic 1 to logic 0 logic-level contrast ratio of the square lattice all-optical XOR/XNOR logic gate is always more than 15dB.Second part is about optimized design and performance analysis of all-optical AND, NOR, NOT logic gates and half adder based on photonic crystal for optical phase modulated signals.According to the numerical results of proposed XOR/XNOR, this kind of logic gate converts the phase information of the input signals to amplitude at the outputs.By cascading two XOR/XNOR logic gates for optical phase modulated signals in parallel and an intensity modulation AND logic gate, using some ports as bias signal ports, all-optical AND, NOR, NOT logic gates and half adder for optical phase modulated signals can be realized. By optimizing the cascading parts a minimum operation power and good performances can be achieved. The results of simulation experiments revealed that the all-optical AND, NOR, NOT logic gate and half adder for optical phase modulated signals had good performances in the C-band (1530-1565nm). The logic-level contrast ratio for AND, NOR, NOT logic operation and half adder digital and carry outputs are not less than 22dB,11dB,17dB, lOdB and 13dB.