Design And Fabrication Of Polymer Waveguide Grating

"The emergence of fiber grating force people to reconsider each design of optical communication system, ... ... in the future, optical communication system without fiber grating will be as unbelievable as a traditional optical system without lens." This words vividly describe that in the future, fiber grating will play a vital role in the field of optical communications. Preparation of the Fiber Grating is confined by the choice of material, technology and other constraints to the further development. However, waveguide grating has overcome the shortcomings in these areas , and would be likely to replace the fiber grating in the future.This paper study the design and preparation of polymer LPWG(long-period waveguide grating ). It propose a new type of structure model of waveguide grating which reduce process steps and difficulty of the technique, and improved the success rate of the device. Through the introduction of planar waveguide, strip waveguides, mode coupling, grating, this paper puts forward methods for the design and analysis of a long-period polymer waveguide grating. Through the discussion of structure and performance parameters of the devices, I master some aspects of the changes that affect the characteristics of LPWG, and thus lay a theoretical foundation for the preparation of the following devices. This paper confirms the design parameters of the waveguide grating, and use semiconductor technology in preparation and testing of the device. The main work of papers summarized as follows:The first part illustrates the feasibility of waveguide grating, mainly from the making technics, selection of the material, and etc, through the comparison of the fiber grating and waveguide grating,then states the advantage of waveguide grating. This paper introduces some studies of the waveguide grating both at home and abroad.The second part describes related theories about the three-layer slab waveguide and channel waveguide in details. First, using wave optics theory, this paper derives wave equation and Helmholtz equation, TE, TM mode electromagnetic field components and boundary conditions and the eigen equation from the Maxwell's equations; and then, from the ray optics theory as a starting point, this paper explains reflection, refraction law, total reflection phase shift, guided mode and the space radiation mode and the substrate radiation mode.Later, this paper discusses the channel waveguide with three-layer slab waveguide theory. It mainly introduces the establishment of the structural model of the channel waveguide, using similar method as Marcatili method. Based on this method, this paper analyses the characteristics of the channel waveguide mode, and then come to its electric field distribution and its characteristic equation.The third section describes the mode coupling theory of the optical waveguide. Coupled mode equation is derived from the Maxwell's equations. Then, taking double-waveguide directional coupler as an example, this paper explains the phenomenon of power conversion when the mode coupling occurs, and then gives the z curve of the transmission of power changing with the waveguide length and the transmission of power belongs to the waveguide 1 and waveguide 2 in dual-waveguide directional coupler. Finally, this paper describes pattern orthogonality and normalization, and gives the conditions for the pattern of orthogonal normalized.The fourth section describes research and design of the theory of the long-period waveguide grating, which is the foundation for and an essential part of the design and preparation of LPWG. At the same time, key of this paper. This chapter mainly consists of two parts:(1) According to the grating theory and the mode coupling theory, this paper summarizes a phase-matching conditions, mode coupling coefficient of expression, coupled with the power transfer rate, in order to lay the groundwork for the next step parameters.(2) This section designs the model of the long-period channel waveguide grating, and analyses its parameters of structure, properties and so on. It derives distribution situation of the mode field, mainly using similar Marcatili method of the channel waveguide, and then find out the calculatioin methods of coupling coefficient between each mode using grating coupled-mode theory. By the confirmation of LPWG coupling coefficients, structural parameters, the transmission of energy, etc., this paper establishes a LPWG theory model.In the fifth part, We discusse the results of long-period waveguide grating parameters, which is the most important part in the designing of waveguide grating. We take 1.55μm as the resonance wavelength, and through the analysis of each parameter of LPWG, we discusse its impact on the grating modulation and ultimately determine the parameters of each structure characteristic.The structural parametersinclude the width and thickness of LPWG waveguide core, the width and thickness of upper cladding layer, grating height, grating period, the transmission power and so on. Through the analysis of these parameters we can obtain a long-period waveguide grating for a specific wavelength attenuation. Based on the discussion of these structural parameters, we can find out the variation of the characteristics of LPWG. Then, We can adjust meet the needs of our different designs. After the final discussion, we have identified the parameters of long-period channel waveguide grating, which is fabricated on the SiO2/Si substrate, and takes polymer PMMA doped with different materials as the core and cladding material (the refractive index, is 1.495 and 1.483 @ 1550nm respectively), and resonance wavelength of long-period channel waveguide grating is 1550nm.The last part mainly introduces the preparation and testing of long-period waveguide grating, which is the final stage in the completion of the entire device. In this part, we first introduce the selection of the prepared materials, and illustrate its advantages; later, based on existing conditions, we develop the preparation process and begin the preparation.Then, we test the qualities of the devices which is complete, and briefly describe the testing system. Thus, this paper have completed the whole making process of the polymer long-period channel waveguide grating, from the designation and preparation to the final testing.