Research On Optical Waveguide Micro-ring Modulator Based On SOI Material

With the rapid development of global communication network technology,optical interconnection has gradually become an ideal communication method to replace the traditional electrical interconnection because of its advantages of wide band,low loss and anti-interference.Optical modulator as one of the core components of optical communication system,directly affects the quality of the entire communication system.Due to the rapid development of silicon-based optoelectronics in recent years and the compatibility of micro-fabrication technology of silicon-based optoelectronic devices with CMOS technology,it has great application value and significance for the research of high-speed silicon-based electro-optic modulator.Silicon on insulator(SOI)material has good waveguide characteristics because of its large refractive index difference.The combination of SOI small-section waveguide and micro-ring resonator structure can be applied to small size,high performance silicon-based electro-optical modulator.In order to improve the light transmission rate in the ridge waveguide,firstly the single-mode condition of the ridge waveguide was determined by theory analysis and software simulation.The transmission matrix method was used to analyze and formulate the propagation characteristics and the characteristic parameters of the micro-ring resonator.We concluded the relationship between performance parameters of the micro-ring resonator with its critical structure dimension.After comparing and analyzing the common electrical structure of the silicon-based electro-optic modulator,it is determined that the inverse biased PN depletion structure with the fastest modulation speed was adopted in this paper.Then we designed layout of the silicon-based micro-ring electro-optic modulator,including the grating coupler,micro-ring resonator with different parameters,matching resistance,lumped electrode and etc.An on-chip 50? matching resistance was designed firstly by theoretical calculation and then by sample experiment in order to reduce microwave reflections.Sivalco was used to simulate the key processes and extract the parameters.The process flow of micro-ring modulator,the principle and operation of key process were also introduced.Finally,a PN depletion type silicon-based micro-ring electro-optic modulator was fabricated.The transmission characteristics of the micro-ring resonator were tested by the optical vertical coupling platform,and the characteristic parameters of each device were obtained.The experimental results showed that the relationship between the characteristic parameters of the micro-ring resonator and the structure dimension of micro-ring were consistent with the theoretical analysis results.Then we tested the static characteristics of the modulator,which was mainly to check whether the PN junction and the matching resistor of device is working,verifying the red shift from blue shift of modulator under different bias voltages.The experimental results showed that the modulator has an extinction ratio of 16.5d B and a quality factor of 12090 at wavelength of 1550 nm with a micro-ring radius of 10?m and a micro-ring and straight waveguide gap of 300 nm.The micro-ring resonator has good transmission characteristics.The modulator was tested for dynamic characteristics and the maximum modulation rate was measured at 30Gbit/s.