Research On Mode Field Coupling And Alignment Methods Of Array Waveguide Devices

Arrayed waveguide devices (AWD) have become the core of the integrated optoelectronic device, supporting the rapid development of optical fiber communication in the21st century. Packaging of AWDs is an essential manufacuring process to acquire their complete optical functions, in which the devices bonded firmly together with some kind of epoxy after a prcecise mode field coupling of the waveguide chip with the input&output fiber arrays on a flexible movement platform with6degrees of freedom in full space. On one hand, the coupling is an optical alignment with submicron-level positioning accuracy, whole space and multichannel. Insufficiency of the alignment accuracy of any channel will result in the fall of AWD’s signal transmission or conversion function, and even make the whole device a waste; on the other hand, the junction intensity and the stress distribution of AWD inevitably cause the micrometric displacement on coupling interface in a complicated enviroment, and then degrate the reliability of the devices. Packaging of AWD, which is the key technology to fabricate AWD and become a technical bottleneck to hinder the developing of integrated optoelectronic devices, is a blend of multiple theories and the21st cutting-edge technologies that involve guided wave optics, integrated optics, control science, microfabrication and materials science.This paper developed some research focusing on mode field coupling theory, space gesture detection, pose alignment technology, multi-channel mode field coupling technology and accuracy analysis of the alignment of arrayed waveguide devices. The main research contents as well as the corresponding results are listed as follows:(1) Based on electromagnetism wave equation and weak guide conditions, this paper discussed the error distribution of some kinds of mode field distributions and the mode field coupling loss caused by spatial deviation according to fundamental mode conditions of fiber and rectangular waveguide, and then analyzed the discipline of mode field coupling loss under the combined action of wavelength and those spatial deviation, therefore this paper proposed a new wavelength correlation model of mode field coupling. Studies of mode field coupling loss and simulation experiments by the finite difference beam propagation were made effectviely and their results indicated that spatial deviation (such as axial deviation, axial clearance and axial decline) are some of the most important causes to induce mode field coupling loss, and meanwhile wavelength alter the amount of coupling loss as well. (2) The spatial pose movements between the coupling components are the precondition for AWD’s coupling and packaging. Based on kinematics of mechanism D-H equation, this paper presented the spatial pose transformation equation of6-DOF platform after making search of relationships and regularities between the pose of the terminal fixture and those independent movement mechanisms, and also proposed a rotary control equation as well as a D-H condition which limit the deviation of terminal coordinate and acquire concentric rotation. The novel model of a rotary control and its conclusion will provide theoretical guidance for the spatial pose alignment of mode field coupling and the optimization of the6-DOF platform.(3) After analysis of the spatial geometrical relationship between2D vector and3D vector, this paper presented a reconstruction model for3D system with binocular orthogonal image system and two kinds of line detection algorithms with polar angle detection error less than0.01degree; based on the feedback of pose detection, this paper presented a closed-loop control method for the pose alignment with angle alignment error less than0.1degree; and based on the coordinate matrix transformation and the spatial geometry, the paper studied the accuracy of3D pose detection caused by line detection error and three-dimensional reconstruction error, and then built an error model of3D pose detection, which drew a conclusion that the error of3D pose detection is similar to that of2D line when the error of3D reconstruction is small enough.(4) The multichannel coupling in the coupling plane is the key to reduce axial deviation and achieve multichannel accurate alignment. Based on the simplification of coupling loss function and geometric deviation of the multichannel coupling, this paper proposed a kind of single-channel mode field coupling algorithm on model fitting methods and a kind of multiple channels equalization algorithm according to the coupling extremum of dual channels, which achieved single-channel coupling loss less than0.15dB and deviation of mode field coupling loss of2channels less than0.15dB respectively, and this paper also discussed the error distribution of the multichannel coupling loss caused by the manufacturing error, single-channel alignment error and the angle error of dual channels equalization and then built a theoretical model to analysize them. Theoretical analysis and numerical calculation showed that three kinds of the errors affect the multichannel mode field coupling losses simultaneously with the same effects.