Research On Flexible Coupling Structure Of SoS Double Layer Waveguide Port

With the rapid development of optical communication and optical network technology,the requirements for the size and integration level of photonic integrated chips(PIC)become increasingly higher.Based on three-dimensional integration technology,the multi-layer waveguides can provide additional on-chip space to improve chip integration.But the tight interval between different layers brings great obstacles to the interconnection of multilayer waveguides with optical communication devices such as optical fibers and lasers.It's worthwhile to explore a suitable method to achieve the efficient coupling between multilayer optical waveguides and standard single-mode fibers.In this thesis,a polymer flexible coupling structure is proposed for the two-layer Silica-on-Silicon(SoS)waveguide previously developed by our research group.And the polymer flexible coupling structure is optimally designed and fabricated experimentally.Firstly,the recent developments of multi-layer waveguides technology and multi-layer waveguides on-chip coupling schemes are summarized,and two new flexible waveguides preparation technology are discussed to find a suitable preparation method for multilayer coupling structures.Secondly,a flexible coupling structure for SoS double-layer waveguide port is proposed,and a three-dimensional longitudinal step approximation method modal is established for analyzing large-angle curved waveguides.In addition,the end face of SoS double-layer waveguide chip is characterized by scanning electron microscopy(SEM)to abtain the structural parameters of the SoS double-layer waveguide.Afterwards,a mode analysis of the measured SoS double-layer waveguide is investigated to obtain the single-mode transmission conditions at 1310 nm and 1550 nm.The effects of waveguide width,unetched waveguide layer and double-layer waveguide lateral offset on the transmission mode are also analyzed.Then,two kinds of S-curved conical waveguides with different shapes are analyzed by three-dimensional mode field overlap integration and three-dimensional longitudinal step approximation method.The optimal structure parameters such as input and output diameter,length,bending radius and curved shape are obtained.The performance of the flexible coupling structure is given according to simulation.Finally,the flexible waveguide preparation platform base on micro-needle direct writing method is built.And the diameter of flexible waveguides under different preparation conditions are investigated,then the flexible coupling structure based on SoS double-layer waveguide port is successfully fabricated.Lastly,we test the device performance such as the light spot image,insertion loss and polarization dependent loss,and compare them with theoretical results.