Amorphous Silicon Thermal Light Can Be Tuned Thin Film Filter

Tunable optical filter is one of the key components of the wavelength routing technology in the next generation optical networks. It also could be used for wavelength routing control and configuration, Demultiplexing, optical channel dynamic selection and some other aspects. Thermo-optical tunable thin film filter has some advantages, such as flexible designing, simple mechanism and wide tuning range, and it could offer moderately high tuning speeds provided that only microscopic thermal masses are heated. The research in this paper is mainly about the structural designing of the tunable thin film filter and the processing of amorphous silicon membrane depositing by PECVD.At first, three Fabry-Perot filter structures are designed and described using smith method and phase analysis results, and three kinds of spectral response characteristic are achieved such as narrowband channel response, flat top response and multi-channel narrowband response. The thickness sensitivity and tolerance are calculated by import the film thickness error. The three common F-P filter structures'tolerance characteristics are discussed respectively. The thickness control strategy is established after the monitoring curves are analyzed. In the research of the tune ability, the matching conditions of the thickness are proposed. The three common F-P filter structures'tune ability is described after import the thermo-optic coefficient and thermal expansion coefficient of each layer. At last, the thermal field distridution of two electrodes are simulated respectively, and the tuning characteristic of double rectangular electrodes and anaular electode structure are compared and analyzed.The formation mechanism and the internal structure of the amorphous silicon thin film deposited by PECVD are researched. The sample's surface morphology is observed and the optical parametric is tested. The testing results of samples at the different processing parameter are analyzed using the formation mechanism theory. The results show that, amorphous silicon structures have great flexibility under different processing parameters. The bonding energy and micro-defects are the major factors that affect the film refractive index and film quality. The bonding process and the formation of defects are mainly determined by the releasing of hydrogen, the diffusion mechanism, the etching effect, and the number, energy and composition of the surface reaction elements. In process parameters, the RF power and pressure affect the number, energy and composition of the basic elements, the substrate temperature effect the surface diffusion and atomic bonding.