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Structural Design And Performance Study Of Optical Communication Devices Based On Photonic Crystals

Posted on:2018-05-28Degree:DoctorType:Dissertation
Country:ChinaCandidate:W LiuFull Text:PDF
GTID:1318330515972375Subject:Information and Communication Engineering
Abstract/Summary:PDF Full Text Request
With the rapid development of society,optical communication plays a more and more important role.Thereupon,photoelectron crystals,which is a kind of micro/nano device,appeared.This kind of devices can manipulate photons,just as semiconductor devices manipulate elecrton.The advantages of the device are low loss,small size and easy to be integrated.The thesis is focus on the problems about the designing of optical communication devices based on photonic crystal(PC).The main content is composed of four parts which are the lens for coupling in the optical communication system,the waveguide for the transmission module,the power splitter and the filter.The first part is the design of graded photonic crystal(GPC)lens,for solving the problems of difficulties and high complex in designing of the circular symmetric lens.(1)GPC Lunburg lens with silicon dioxide is designed,based on square lattice photonic crystal.After comparing the features of the two mode lens,the best design of the lens is given.By making the gradient in the direction of one dimensional,a kind of flat lens is designed on TM type lens with better convergence effect.The numerical aperture and the PC layers of the lens are optimized through the calculation of the convergence power with different incident conditions and different size.The fault tolerance of lens is discussed,and it is concluded that both lenses are good structural stability.(2)On the basis of Sunflower quasi-periodic photonic crystal(QPC),the gradient Lunburg and flat lens working in the visible band are designed.The beat-length of flat lens caculated by the study of focus features has high coherence with the one caculated by the study of focus features has high coherence with the one calculated by refractive index distribution relationship.(3)Based on silicon substrate,different types of lens working in the infrared band are designed by changing the refractive index distribution.According to the convergent effect,the PC layers are optimized.It provides a theoretical guidance for a simple experiment.Double focusing effect was found in the study.(4)Structure Sunflower lens with 5layers was made by the method of the electron beam etching.The second part,aiming at the troubles that big bend wave guide is not smooth,great loss and difficult to realize arbitrary bending,the design on Sunflower QPC waveguide is carried out:(1)Four channel beam splitter of "A" and "C" type are designed.By comparing them,it is concluded that "C" type four channel beam splitter has better splitting performance.The influence of different locations of defects in four channel splitter on effect of splitting is analysised.(2)Three big bend waveguides with different bending degrees is designed.By comparing their transmittance of comparison,little bend loss was found with the increase of the structural bending degree.(3)Fan-type gradient waveguide structure is designed.The structure is optimized to match three communication wavelengths.After extending the fan-shaped structure to "U" type structure,the waves was found transmitting along the waveguide structure with low loss.In the third part,multi-channel PC filter with multi-wavelength is designed based on two dimensional square lattice PC structure,giving a solution for the problems of multi-channel filter such as the high complex structure,downloading message in single wavelength,the mutual interference among channels.The filter is composed of the waveguide,the reflection wall,multimode cavity and output port.Every port can download three different wavelength.The transmission rate of all channels are more than 90% in the band of 1500 nm to 1600 nm.The size of the filter is only 17 ?m x 27?m.The design of the whole structure will reduce the filter size significantly.It is suitable for multiplexing and demultiplexing in WDM system.There will be a good application prospects in the light path intergration.In the fourth part,the analysis of the super lens effect in different quasi-periodic structure photonic crystal.The study provides an approach for the replacement of positive refractive lens.It was found that the former negative refractive lens focusing effect is superior to the latter,and the structure in low refractive index material(such as polymer materials)can also produce negative refraction convergence effect.
Keywords/Search Tags:Quasi-periodic photonic crystals, Graded photonic crystals, Lunburg lens, Flat lens, Visible light communications, Infrared light communications, big-bend Waveguide, Beam splitter, filter, Negative refraction, Super lens
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