Design And Parameters Optimization Of PIN Photodetector Equivalent Models

These research work of this dissertation was supported by Basic Research on Integrated Optoelectronic Devices and Microstructure Optical Fibers with Structure and Technology Innovations for Future Advanced Optical Communications(No.2003CB314900), Co-Constructed Project of Beijing Education Committee (No.XK100130437) and program for Changjiang Scholars and Innovative Research Team in University (No.IRT0609) , MOE, China.With the rapid development of WDM optical communication and increasing requirement of bandwidths, fiber communication will be evolved to the new generation with intelligent, integrated, low cost and high reliability. Compared with the discrete optoelectronic devices, the optoelectronic integrated circuits (OEIC) have the advantages of smaller dimension, lower parasitic, lower cost, better performance and higher reliability. OEIC have already become extremely attractive domain as the fundamental research subject in the area of optical communications and optoelectronics.Photodetector is the key device of optical signal conversion in optical fiber communication and photoelectric detection system, which is an important component of optoelectronic integrated circuits receiver. The analysis of its response characteristics and output characteristics is helpful for OEIC CAD. Establishing the unified equivalent circuit model, which can be used to analyze signal response characteristics, is the premise to get the accurate predict of these properties. The author focused on the design and parameters optimization of PIN phtodetector model. Research results, as listed below, have been achieved. 1. The fabricating and testing for InP-based PIN photodetectors were implemented. Current-voltage characteristics were good, dark current was smaller, photocurrent was larger, and the measured S-parameter model met the basic needs.2. Researching on photodetector nonlinearity was carried out, through theoretical analysis and experiment, it is manifested that the energy of the optical pulse caused an increase of the wide frequency bandwidth when the optical power was larger than 0.5mw.3. The small signal circuit models of PIN photodetector were given. Using direct extraction method, all the PIN photodetector parameters were extracted. Using these parameters, the circuit models of PIN photodetector were obtained. The simulated results of model are quite corresponded with the measured results of devices, Which proved that the parameter and model are comparatively accurate.4. Improved genetic algorithm was applied to the PIN photodetector parameters extraction, as a result of improved genetic algorithm is a global optimization algorithm, compared to the existing algorithms, the extent of convergence and the cycle's times were not dependent on the initial value, the error of optimization value was smaller.