| Human society is entering into an information age powered by rapidlyevolving technologies in areas of microelectronics, optoelectronics, computingand communication. However, due to the rapid increase of information,continuous requests have been made for the increase of speed, Signalpropagation and switching speeds in the electronic domain are communicationrevolution based on photonics, which is known to telecommuincations havetaken place in the last sveral years with the advent of optical dense wavelengthdivision multiplexing (DWDM). DWDM has become the leading enabler for anall-optical network. The continuing development of fiber-based communicationsnetworks to accommodate future demands will eventually depend on theavailability of cheap, reliable, and robust integrated optical waveguide devicesfor routing, switching, and detection. In the area of materials, polymer hasattracted much more attention because they offer rapid processibility,cost-effectiveness, high yields, high performance, such as lower optical loss andsmaller birefringence compared to silica, power-efficient thermal actuation dueto a larger thermo-optic coefficient than in silica, and compactness owing to alarge refractive index contrast.Among different techniques to enlarge the speed and capacity for the currentfiber network, arrayed waveguide grating (AWG) multiplexer is very promising.AWG can offer some basic function including multiplexing/demultiplexing,optical add/drop mutiplexing (OADM) and optical interconnection. Also, itpossesses some advantages, such as easy optical integrating, narrow wavelengthspacing, much more signal channels and low crosstalk. Recently, considerableattention and great efforts have been focused on the development of polymerAWG, because of their excellent particular features, such as easy fabrication, lowpropagation loss, small birefringence, and easy control of the refractive index. Atpresent, many developed countries have put abundant researchers and moneyinto the study of these devices, and have made great progress.Due to complexity of the designing work, AWG designers encounter muchdifficulty and inconvenience. Difficulty in AWG designing is greatly lowered bycomputer simulation and by using software to analysing and design AWG.,which is a new way to design AWG.Beam Propagation Method (BPM) is one of the most effective methods insoloving field ditribution in optical waveguide. Brief introduction to BPM iscontaind in paper, as well as Effective Index Method (EIM) and Weighted IndexMethod (WIM) both based on BPM. WIM is widely used in solving opticalditribution in waveguide of all kinds of cross cross section, while EIM is moreeffective and conventinet for the condition that boundary condition of modeprofile is well matched both in upper cladding and lower claddingAWG computer aided design and analysis is the core of paper. Basicsimulations of important parameters relevant to AWG are carried out byWDM_Phasar software based on BPM such as crosstalk, diffraction loss. Andthen designs for 9-channel AWG and 32-channel AWG are finished by optimzingAWG parameters with the following designing experiences drawn from basicsimulation. Performance of AWG is improved with diffraction loss less than 2dB,crosstalk below -45dB:1,Under the condition that the arrayed waveguide separation d 2 keepsconstant and that d1 and d 2 are set between 6μm and 40μm, crosstalk of AWGis linear function of I/O waveguide separation d1 .2,Under the condition that the I/O waveguide separation d1 keepsconstant and that d1 and d 2 are set between 6μm and 40μm, crosstalk of AWGis irrelevant to arrayed waveguide separation d 2.3,Under the condition that the arrayed waveguide separation d 2 keepsconstant and that d1 and d 2 are set between 6μm and 40μm, diffraction loss ofAWG keeps invariable.4,Under the condition that the I/O waveguide separation d1 keeps constantand that d1 and d 2 are set between 6μm and 40μm, diffraction loss of AWGincreases with the increase of arrayed waveguide separation d 25,Under the condition that the arrayed waveguide separation d 2 keepsconstant and that d1 and d 2 are set between 6μm and 40μm, diffraction loss ofAWG doesn't vary with changes of free propagation length f and I/O waveguideseparation d1 .6,Equation d1 = d 2 is not optimum choice for AWG.. Generally speaking,when the value of d1 × d 2 keeps invariable, AWG performance can beimproved by setting d1 > d 2 with crosstalk and diffraction loss of AWGdecreasing. That is, insert loss of device decreases naturally.By analysing characteristics of polymer used in AWG fabrication,fluorinated polyimide is chosen as material for AWG. And synthesis offluorinated polyimide and thermal analysis are detailedly investigated in paper,as well as its structure indicating.Etching mask deposition is crucial to AWG fabrication, for it affects directlyquality of core-layer waveguide. Metal is frequently used as etching maskagainst gas etching. Aluminum is used as etching mask in experiment. Andprocessing of aluminum steaming on polymer surface is systematicallyinvestigated in the paper, together affect induced by aluminum. Due to existentaluminum in polymer, radication loss in device increases. Aluminumconcentration must be lowered to eliminate the disadvantage that device lossincreases. The disadvantage can be eliminated by technique optimization inexperiment.Ethcing is critical to successful fabrication of AWG. Reactive Ion Etching,which is characterized by high selectivity, higt etching rate, controllability andhigh uniformity, is chosen to etch optical waveguide. In RIE ion bombarding willproduce fluctuating structure liking saw-shaped slope in waveguide sidewall. Itincreases radiation loss of device. The relation between etching rate, sidewallroughness and RF power and Oxygen rate is deeply investigated byimplementing careful research on RIE. And the best etching condition is given asfor fluorinated polyimide in paper to decrease device loss. |
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