Silicon Optical Filter With Multiple Semi-rings

The basic function of the optical filter is to select the desired wavelength signal from a large number of wavelength signals.The optical filter acts as an important role in the optical communication and optoelectronic devices or systems.It is widely used in wavelength selection,noise removal of optical amplifier,gain equalization of optical signals,multiplexing /demultiplexing of optical signals,frequency stabilization,channel selection of WDM,upper and lower voice paths,etc.With rapid development of all-optical networks,the optical filter confronts more and more requirements and has a broad application prospect.Improving the filtering performance of optical filters and adapting them flexibly to different application requirements are the leading issues.Here a silicon optical filter with multiple semi-rings is proposed.It utilizes the interference between multiple semi-ring waveguides to realize the filtering function.The proposed optical filter possesses a simple structure,small volume,good filter performance and integration.Only changing the amount and spacing distance of semi-rings,this optical filter can flexibly adjust the filtering properties so as to meet different application demands.The main research contents of this paper are as follows.Based on the investigation about optical filters(including the structural,operating principle,their advantages and disadvantages and applications)and related theory,a silicon optical filter with multiple semi-rings is proposed.The structural,working principle and manufacturing process of the proposed optical filter are given.The filtering theory is also deduced.Furthermore,based on the rectangle waveguide and the ridge waveguide structures,the filtering characteristics of the optical filter are studied by ‘FDTD Solutions' software simulation.The main factors affecting the filter performance(the amount of semi-rings,the semi-ring spacing distances and the coupling waveguide lengths)are explored,and the structure parameters are optimized.The work can provide theoretical guidance for the preparation of optical filters.After optimization,the proposed optical filter with rectangular waveguide has a 3d B bandwidth of 2.52 nm,a free spectral range of 11.33 nm,a fineness of 4.50,insertion loss of-0.24 d B,and extinction ratio of 13.53 d B.Finally,the silicon optical filter with multiple semi-rings is compared with a based Mach-Zehnder interferometer optical filter with the traditional structure.The researching results show that the silicon optical filter with multiple semi-rings has a narrower 3d B bandwidth which is 0.44 times that of the traditional Mach-Zehnder interference optical filter.Its free spectral range is approximative to that of the traditional Mach-Zehnder interference optical filter.Its fineness is higher and is 2.28 times that of the traditional Mach-Zehnder interference optical filter.Therefore,the silicon optical filter with multiple semi-rings has better filtering performance than the Mach-Zehnder interference optical filter with the traditional structure.The silicon optical filter with multiple semi-rings has a simple and compact structure,and shows a good filtering performance.Also,only changing the amount and spacing distance of semi-rings,it can flexibly adjust its properties to meet different application requirements.Therefore,the proposed optical filter has a good prospect and practical application value in the optical communication and optoelectronic devices or systems.The research work in this paper can provide a new idea and methods for seeking high performance and miniaturization optical filters in the future.