Research On Silicon-based Waveguide Special Type Grating Coupler And Its Design

Integrated optics have been booming since the 21 st century.The grating coupler for silicon have become the important researching field while the development of the photonic integrated circuit(PIC),especially silicon photonics.Grating coupler can be the I/O ports for PIC,not only providing external source for PIC but also outputing the lighting.What is more,grating coupler can be the I/O ports for independent polarization and Wavelength Division Multiplexing/Demultiplexing and so on.So grating coupler is one of the important device for PIC and the means of Optical Interconnects.Photo-communication on chip is gradually paid more attention by reseachers with the report of the high-speed detection with monolithic silicon photodiodes at mid-infrared wavelength.So the research of large bandwidth grating coupler will be boost the development of photo-communication on chip at mid-infrared wavelength.In our work,the two dimension sub-wavelength chirp grating coupler has been designed at 2 ?m wavelength scope so that the large bandwidth coupling have been achieved at mid-infrared.The linear chirp grating has been designed along the propagation of light and the apodized grating has been designed along the verticality propagation of light.This structure improves not only the bandwidth at 2 ?m wavelength scope but also the coupling efficiency.During the research of the grating structure we discover that there is not a n universal and esay way designing the complex functional grating structure such as polarization independent coupler other than designing the complex and unfamiliar structure.In our work the universal method has been estabished to design the complex functional grating structure.This method is an inverse design based on unlinear computing searching algorithm.The designer only need confirm the device performance objectives,convergence domain to automatic optimizing special type grating coupler by computer without considering the structure researching.The ultrahigh effective perfectly vertical grating coupler and polarization independent grating coupler have been designed.The feasibility of this design method by verifying the results of grating couplers has been demonstrated.It will offer a new thought that researching and designing grating coupler even other silicon photonics devices.