| Since Yablonvitch and John proposed the concept of photonic crystal in 1987,photonic crystal has become a research hotspot.Its special properties,such as photonic band gap,photon localization,negative refraction and self-collimation effect,which can meet people's research needs.The photonic devices based on photonic crystal have the characteristics of small structure,simple material,low loss,high bandwidth,and are widely used in the field of optical communication and photon integration.In this paper,the free software package MPB and MEEP developed by MIT are used for numerical simulation.The MPB based on the plane wave expansion method(PWE)is used to calculate the dispersion relation,the band gap and the self-collimation of the photon frequency.The MEEP based on the finite difference time domain method(FDTD)is used to study the transmission relation and the field distribution diagram.Focusing on the special dispersion phenomenon in photonic crystals,an interference filter based on self-collimation effect is proposed and its properties are studied.The principal research contents and achievements are as below:1.In this paper,the filtering characteristics of Gires-Tournois filter,which is a new interference filter composed of a total reflector based on Michelson interference filter and an asymmetrical Fabry Perot cavity,are systematically studied.2.Based on the MPB,we have calculated the range of the self-collimation frequency of Gires-Tournois filter based on the photonic crystal.The beam splitter,partial reflector and total reflector are designed.3.Beam splitter is a kind of beam splitting function which is realized by enlarging or reducing the radius of perfect photonic crystal,or adding air channel.The principle of partial reflectors is to use two rows of line defects or air grooves to complete.The design of total reflectors is mainly to use the photonic band gap to achieve the function of total reflection.4.Two types of Gires-Tournois filters are designed.When the arm length difference is set to 0.5d(d is the cavity distance of asymmetric Fabry Perot cavity),the output port of Gires-Tournois filter can realize the transmission spectrum similar to rectangular wave.Through a lot of research,we find the crystal structures suitable for the TE polarization mode and the TM polarization mode respectively,both for the first and second band.5.With the increase of d,the number of periods of transmission spectrum increases in the range of self-collimation frequency.This filter can adjust the bandwidth of the output waveform by changing the asymmetric Fabry Perot cavity distance and arm length of the Gires-Tournois filter.For these properties,the new filter designed by us can be flexibly used in the integration of high optical communication.The innovation of this paper is: using the special dispersion property of photonic crystal the self-collimation effect of photonic crystal,a Gires-Tournois filter based on twodimensional photonic crystal hole/rod type is proposed and designed for the first time.The structure characteristics of the filter in the TE polarization mode and TM polarization mode,both for the first and the second band are studied systematically.The Gires-Tournois filter can achieve wide band-pass/band-stop function by setting appropriate parameters(arm length,hole/rod radius,dielectric constant,lattice structure,etc.).Because of its exquisite structure,low energy loss and simple simulation,it has a good application prospect in the future photonic highly integrated devices. |
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