Research And Simulation Of GaN Micro-nano Gratings For Active Photonic Integration

In this dissertation,the active integration and regulation of GaN photonic device based on micro / nano gratings in the 430nm-470 nm GaN-based In GaN quantum well active band are discussed.With the rapid development of silicon-based integrated photonics,the design of active integrated gallium nitride waveguide grating filters is necessary to promote the development of optical communications and related optical fields.Firstly,for the uniform waveguide Bragg grating structure,grating coupling assisted active integration of GaN membrane waveguide and In GaN/GaN MQWs active layers based on GaN-on-silicon LED platform is proposed based on the theoretical methods such as slab waveguide theory and coupled mode theory,etc in this dissertation.A Finite Element Method(FEM)simulation based on COMSOL Multiphysics is performed to optimize the grating parameters.The main contents include:Determine the structure and size of the rectangular waveguide;study the influence of related structural parameters on the coupling performance of the grating;explore the influence of the incident light angle on the coupling performance of the waveguide grating.Secondly,combined with high-efficiency active integrated GaN waveguide gratings,a band stop filter is designed based on the Finite Difference Time Domain method(FDTD)simulation.The effect of related grating parameters including grating period,duty ratio,etch depth,and waveguide thickness on the filtering characteristics is studied,and the central wavelength of the waveguide Bragg grating is tunable.Further,in order to improve the wavelength control characteristics,the following optimization design is proposed: using grating period and duty cycle combined modulation.The waveguide grating filter finally designed has the advantages of narrow bandwidth and high density.Combined with the excellent thermo-optical characteristics of GaN materials,a tunable filter with a filtering wavelength matching the refractive index of GaN waveguides in the range of 430nm-470 nm is realized.Compared with the traditional thermo-optical device structure,this structure improves the wavelength tuning sensitivity,realizes a wide range of wavelength tuning,and the 3d B filter bandwidth is 1nm.Finally,a band-pass filter is implemented using two optimized band-stop filters.The filter has a passband range of 40 nm and an amplitude greater than 0.75,and can achieve different passband sizes by changing the grating period.