The Coupling Effect Of Unidirectional Edge Mode In Two Dimensional Magneto-optical Photonic Crystals

Recently, the one way edge mode based on magneto-optical(MO) photonic crystals(PCs) have drawn much attention of numerous scientific workers in both fundamental research and applications, due to their inherent novel phenomena. In the case with an external dc magnetic field applied onto the MO-PC, strong gyroelectric or gyromagnetic anisotropy can be induced in the MO-PCs, which breaks the time-reversal symmetry of the PC, and then surface mode that propagates in only one-way direction could be supported at the edge of MO-PC. This paper will further investigate the physical properties of one-way electromagnetic edge mode of PC on the base of previous studies. Up to now, studies have focused mostly on single one-way edge mode of Photonics, and the coupling of the one-way edge have received less attention, which will appear some interesting phenomenon, such as slow light waveguide, one-way air waveguide and micro cavity modes etc. The main elements of summarized as following:A new type of slow light waveguide was designed, which consist of two magneto optical photonic crystals(MOPhCs) by some coupling distance. The one-way edge mode will be generated at the edge of MOPhCs with the external dc magnetic filed, if the same direction magnetic filed applied into the two MOPhCs, the direction of two MOPhCs one-way edge modes are opposite. Given a proper interval of the two edges, two unidirectional edge modes with opposite group velocity directions can be coupled. The coupling leads to a wide flat band in which the group velocity is near to zero at the interval is 1.5a. The advantage of slow waveguide in the research is that the position of the flat band and the group velocity can be adjusted by the external magnetic field.Based on the coupling effect of one-way edge mode, an unidirectional air waveguide has been designed. The unidirectional edge modes in two-dimensional magneto-optical photonic crystals have a unique feature because they are robust to against imperfections or disruptions along the edge, but they can hardly form an optical beam. In order to obtain a unidirectional air waveguide, we have studied the coupling effect of two unidirectional edge modes basing on band calculations and numerical simulations. With a waveguide width of 1.5a an ideal unidirectional air waveguide is achieved. The unidirectional air waveguide has great performance because of its broad working bandwidth, high extinction ratio, single-mode feature and air waveguide configuration. It has an advantage over the unidirectional edge waveguide because it can focus the wave energy and form a one-way beam.Magneto-optical storage system based on the coupling of the one-way edge modes and micro cavity modes. Optical storage system is the key role for the future all-optical communications and computer. Through numerical study, we design a new kind of magneto-optical storage system based on the coupling of one-way edge modes of magneto- optical photonic crystals and micro-cavity modes. A close field circulation loop is achieved from the one-way edge modes. By designing a magnetic cavity and another edge waveguide, we can not only takeout the signal from the loop but also write the signal into the loop. Through controlling the magnetic field on the cavity, we can dynamically achieve the operation of reading and writing of electromagnetic signals.