Surface Modes Properties And Displacement Sensing Properties Of Two-dimension Photonic Crystals

First of all, the band gap features of big hole structure two-dimensional photoniccrystals is studied, and the results show that2D photonic crystals with square lattice holestructure attains maximal band gap width as the diameter of holes is1.13times the period ofthe lattice. Band gap map of the big hole structure is with great relation to the refractive indexof hole and medium. There is no band gap when the difference of refractive index betweenhole and medium is not big enough. When the refractive index of medium is invariable, thelarger the refractive index of hole is, the smaller the band gap width will be. When therefractive index of hole is invariable, the band gap emerges as the refractive index of mediumincreases to big enough; the band gap width will increase obviously till to the maximum, thendecreases tardily. And then the results are compared with the features of normaltwo-dimensional photonic crystals. The comparison shows that these two features are exactlysimilar.Secondly, the surface modes of two-dimensional photonic crystals is investigated. Themethod is achieved by calculating the band modes by Plane Wave Expansion method andintegrating the modes, and then the surface modes are obtained. The method is used to studythe relations between the surface modes features and the size of surface medium for columnmedium square lattice, column medium triangle lattice, square medium square lattice andsquare medium triangle lattice. The results show that the surface modes curves of same latticestructure decline gradually as the size of surface medium increases. The square latticephotonic crystals obtain greater size of surface medium to acquire surface modes and lessrange of surface mode frequency. The light transmits restrictedly through the surface only ifthe wavelength of input light is during the frequency range which includes surface modes.Otherwise, the light will transmit into the air or the photonic crystal, and the energy of lightwhich transmits along the surface medium will decay rapidly. And the calculating result is inaccord with the phenomenon that the light transmits.Finally, the features of displacement sensoring properties of super lattice structuretwo-dimensional photonic crystals is studied. The super lattice structure two-dimensionalphotonic crystals are separated into two parts which are fixed on two bases, respectively. Theband gap feature of photonic crystals will change as displacement occurs between these two parts. The change of band gap feature, which is result of displacement between two parts, iscalculating by plane wave expansion method. And the theoretical results of displacementsensor are obtained. The result shows that: the greater the diameter of move-medium is, themore obviously the change of bang gap is during the displacement. The optimal diameter ofmove-medium is0.3μm, and then the super lattice structure two-dimensional photoniccrystals are formed. When the move-medium is located on the center of fixed-mediumlattice, there are two obvious and wide band gaps whose center wavelengths are1.37μm and2.11μm. The wavelengths of input lights are set by these twowavelengths above, and then the output lights are detected. The changes of thetransmission spectra of these two wavelengths are found to be similar. Both of themwill form a peak of wave, but the input light whose wavelength is1.37μm obtains anobvious phenomenon.