Research Of One-dimensional Photonic Crystals Band Gap Based On Dirac Semimetal

Terahertz wave generally refers to electromagnetic wave with frequency between 0.1 and 10 THz,which is between microwave and infrared.Because of its special position in electromagnetic spectrum,terahertz wave has both photonic and electronic characteristics,so it has a wide application prospect in security detection,sensing detection,communication and medical treatment,medical imaging and so on.Photonic crystals are synthetic periodic array materials,which are composed of periodic dielectric materials arranged alternately.Due to the periodic change of dielectric constant in photonic crystals,electromagnetic wave will generate periodic potential field inside photonic crystals.When it passes through photonic crystals,due to Bragg scattering,electromagnetic wave is periodically modulated by photonic crystals,which makes some wavelength electromagnetic waves pass through photonic crystals differently,thus photonic forbidden in the transmission spectrum of photonic crystals.Band,photonic crystal band gap.The bigger the refractive index difference of the dielectric materials of periodic photonic crystals is,the stronger the Bragg scattering is,and the easier the photonic crystal band gap will appear.The band gap structure of photonic crystals can control the photon motion just as semiconductor controls the electron motion,so the periodic structure of photonic crystals can control the transmission of electromagnetic wave.Three-dimensional(3D)Dirac semi-metal(hereinafter referred to as Dirac semi-metal),also known as 3D graphene,has all the good properties of graphene,but compared with graphene,it is not susceptible to external dielectric interference,has a higher carrier mobility,and because it is a block,easy to prepare and stable performance,it has a unique feature in the study of THz functional devices.Special advantage.In this paper,we will study the transmission characteristics of one-dimensional photonic crystals with different structures of Dirac semimetal.The main contents of this paper are as follows:(1)The transmission spectra of one-dimensional photonic crystals consisting of Dirac semimetal and silica dielectrics are studied by using the transfer matrix method.It is found that there are two photonic crystal band gaps in the transmission spectra in a certain frequency range,one in the low frequency range is the first band gap,and the other in the high frequency range is the second band gap.It is found that the bandgap of photonic crystals strongly depends on the Fermi level of Dirac semi-metal and the thickness ratio of the two dielectric layers.Then the effects of the Fermi level of Dirac semi-metal,the incident angle of electromagnetic wave and the lattice constant of photonic crystals on the two bandgap of photonic crystals are analyzed in detail.It is found that the first low-frequency band gap does not change with the change of lattice constant and incident angle of electromagnetic wave,but is sensitive to Fermi level of Dirac semi-metal.The band gap of omnidirectional photonic crystal broadens with the increase of Fermi level.Compared with the first band gap,the second band gap will move to low frequency with the increase of the lattice constant,and more band gaps will appear in the same frequency range.The second band gap is also sensitive to the Dirac semi-metal Fermi level and the incident angle of electromagnetic wave.With the increase of the incident angle of Fermi level and electromagnetic wave,the upper and lower frequencies of the second photonic crystal band gap are also sensitive.The boundary moves to higher frequencies.In summary,the tunability of the bandgap of the first photonic crystal is achieved by adjusting the Fermi level of the Dirac semimetal.(2)The transmission spectra of photonic crystal band gap and photonic crystal heterostructure band gap based on Dirac semi-metal are calculated by using transfer matrix method.The band gap of one-dimensional photonic crystal is broadened by constructing photonic crystal heterostructure.By analyzing the band gaps of single photonic crystal and heterostructured photonic crystal,it is found that the band gaps of heterostructured photonic crystal broaden obviously in the same frequency range.Then,the effects of different Fermi levels,different incident angles and polarization waves on the broadened photonic band gaps are analyzed.At the same time,the dielectric constant of Dirac semi-metal will change with the change of Fermi level.Based on this characteristic,the bandgap of broadened photonic crystal can be adjusted.Based on the above characteristics,Dirac semi-metal has potential application prospects in tunable photonic crystal devices.