Grating-Assisted Contra-Directional Coupler Based On Silicon And Phase Change Material Hybrid Integration

Silicon photonics integration has gained wide attention because of its advantages such as compatibility with complementary metal-oxide-semiconductor(CMOS)processes,and has become priority research field for major research institutions and even national strategic deployment.However,the free-carrier dispersion effect of silicon is relatively weak,and the active waveguide is usually long,leading to high power consumption and large footprint of silicon photonic integrated circuits.The introduction of phase change materials can greatly change the effective refractive index of waveguides with a small size.As an important device in the field of optical communications,the optical switch realizes the function of optical path selection by changing the phase of the waveguide.Combining phase change materials with silicon photonic devices can improve the performance of the optical switches in terms of device size and power consumption.This thesis studies a grating-assisted contra-directional coupler.Phase change material is put on top of a silicon waveguide to form the grating.This thesis first introduces the phase change mechanism of phase change materials,and then focuses on the theoretical basis of grating-assisted contra-directional couplers,including coupled mode theory,coupled mode equations,and numerical solutions of coupled mode equations.Next,the basic principle of the grating-assisted contra-directional coupler is introduced,and the parameters that affect the Bragg wavelength are also briefly analyzed.Finally,the combination of phase change material and grating-assisted contra-directional coupler is used for software simulation,and the device design parameters are studied to explore their influence on the device performance.Finally,this thesis presents the manufacturing process of the phase-change material based grating-assisted contra-directional coupler and measurement of the device.The phase change material is based on the chalcogenide material Ge₂Sb₂Te₅(GST),which possess the merits of stable constitute and easy fabrication.To induce phase change,GST is heated up in a hotplate.The experimental results show that the insertion loss of the device is less than 5 dB and the extinction ratio is greater than 15 dB in the operating wavelength range of 2.2 nm.Because of the non-volatile nature of the phase change material GST,there is no need for static power consumption to maintain these two states.