Research On The Coupling Effect Of Surface Wave In Photonic Crystal And Micro Cavity

The surface mode of photonic crystal is a kind of surface wave formed at the interface between the photonic crystal and the media. It can be used to implement the surface resonator and the surface waveguide of the photonic crystal. It also has high value today when the photonic components gradually replace the electronic components to become the mainstream of the communication devices. In this paper, we use the transfer matrix method and the plane wave expansion method to study the surface wave of one-dimensional photonic crystal and two-dimensional photonic crystal respectively. We also set micro cavity defect in this system and achieve the energy coupling transmission through micro cavity resonance. By this study we can design the photonic devices with different kinds of functions.A coupled system of semi-infinite one-dimensional photonic crystal coated with metal and magnetic films is proposed in this study. We can obtain the hybrid states of surface plasmon–polaritons, magnetic defect mode and optical Tamm state from the system. The electromagnetic waves of the hybrid states are confined at the boundary between the metal layer and the magneto-optical surface defect of a semi-infinite one-dimensional photonic crystal. We can consider the magneto-optical material layer as a micro cavity, and an intense resonance effect generates in the micro cavity can lead to total transmission. By using the Bloch theorem of periodic structure and the transfer matrix method we can research the character of the system. It is obviously that tunable nonreciprocal propagation can be achieved from the hybrid states through changing the thickness of magneto-optical material layer.Then this paper researches the one-way edge mode based on the two-dimensional magneto-optical photonic crystal. Edge mode is the surface wave confined at the boundary of magneto-optical photonic crystal. If we make the photonic crystal designed under the magnetic field, time reversal symmetry of the system will be broken. and the group velocity of electromagnetic wave will point to the same directions, after that an unidirectional edge mode is obtained. In this study, we designed a close field circulation loop that is based on the one-way edge mode of magneto-optical photonic crystals. We also devise a cavity beside the loop in advance. The electromagnetic signals will be stored in the single close circulation loop. Then we devise another similar close field circulation loop and merge the two loops into one part. Because of the coupling of micro cavity, the electromagnetic signals can be extracted from the former loop and written into the later loop latter. On the contrary, the signals also can be read from the latter loop and written into the former loop. We can not only achieve the function of the reading and writing operations between the two loops when they are combined, but also achieve the function of signal store when they are divided into two parts. From this we design the separable read-write storage based on the magneto-optical photonic crystals.This study also research the unidirectional air waveguide which is produced by the coupling of two edge modes of magneto-optical photonic crystals with the group velocity pointing to the same direction. If we devise a magnetic cavity between the two parallel unidirectional air waveguides, the electromagnetic signals from one unidirectional air waveguide will be coupled into another unidirectional air waveguide. If we replace one unidirectional air waveguide with a close field circulation loop made by unidirectional air waveguide. We can not only take out the signal from the loop but also write the signal into the loop through controlling the magnetic field on the cavity. Similarly, the signal can be stored in the single loop. Thus we can dynamically achieve the function of read-write and storage of electromagnetic signals. If we devise a close field circulation loop based on the unidirectional edge waveguide between the two parallel unidirectional air waveguides, and set a micro cavity between the loop and the two unidirectional air waveguides on both sides of the loop respectively. Subsequently the function of long-distance coupling transmission of electromagnetic signal comes true. It is also feasible for us that we can extend the distance of coupling transmission of electromagnetic signal by increasing the number of loops or Stretching the length of the loop along the abscissa direction.