Transmission Properties Of 1-D Magnetic Photonic Crystals Under External Magnetic Field Modulation

The combination of magneto-optical effect and magnetic photonic crystal is a new hotspot in photonic crystal research.Affected by the external magnetic field,the permeability of magnetic photonic crystal is a tensor with imaginary non-diagonal elements,then,the time reversal of the system is broken,and the unidirectional transmission for electromagnetic wave can be realized.In addition,these tensor elements will change with the variation of the external bias magnetic field intensity,and the photonic band structure will change as well,which contribute to tunable characteristics.In this paper,the transmission properties of one-dimensional photonic crystal are studied and various photonic devices with different functions are designed based on the characteristics of the photonic crystal using the transfer matrix method.In this paper,we firstly have designed four kinds of one-dimensional photonic crystals with periodic structures including air layer defects.By comparing their transmission spectra that are calculated respectively,it is verified that the non-reciprocal transmission can only be achieved when the system’s time inversion symmetry and spatial inversion symmetry are broken simultaneously,and the more serious the symmetry breaking,the bigger interval between the transmission peaks corresponding to the forward and backward directions is.Then,on the basis of this,we continue to study the influence of the thickness of the defect layer and the incident angle on the non-reciprocal transmission.It is found that adjusting the defect’s thickness and the incident angle will lead to high transmittance and large extinction ratio,which can be used in non-reciprocal devices such as optical isolator.In addition,we give in this paper a new approach to achieve the complete one-way transmission.The forward transmission band will be reshaped into a single peak while a wide bandgap will appear in backward incidence through the serial connection of two non-parallel magneto-photonic crystals.A major innovation in this paper is generating a complete one-way transmission in such wide bandgap.Next,we propose a magnetic micro-cavity system composed of negative dielectric constant material and magnetic material(YIG).A multi-channeled filter that bases on the effect of photon tunneling through the coupled cavity resonators is designed,of which the transmission mechanism and properties can be investigated by the tight-binding model and the transfer matrix method.The multiple channels of the filter correspond to the discrete resonant peaks split from the single resonant mode under the coupling of cavities.At the same time,we also analyzed the dependence of the filter characteristics on incident angle and the thickness of the negative dielectric constant material.It is found that optimal filter performance can be reached when the structure parameters are set appropriately.Furthermore,combining the tunable properties of magnetic materials,the positions of filter channels are found to be controllable when we adjust the intensity of the external bias magnetic field.