Self-biased Magnetic Photonic Crystals: Electromagnetic Properties And Its Applications

Because of their special band-structure and amazing electromagnetic properties, photonic crystals (PCs) have been intensively studied in the past years. Except for the Bragg gap caused by periodic structure, magnetic photonic crystals (MPCs) own other abnormal properties, such as the negative permeability, the surface magneto-plasmon, the negative refraction, the nonreciprocal properties induced by the broken time-reversal symmetry and so on. Based on those properties, deeper researches such as super-lens and photon quantum effect have been developed.However, the traditional MPCs made of soft magnets need the assistance of external magnetic field which causes difficulties in practical applications. To overcome the inconvenience, we proposed the self-biased MPCs (SMPCs) made of self-biased ferrites for the first time which also contributed to the miniaturization of microwave devices. In this letter, we studied the electromagnetic properties and applications of SMPCs.We presented that the material consists of self-biased Sr-ferrite rods only is the left-handed material (LHM). Band-structure calculation, Isofrequency map, Retrieved effective permittivity and permeability and negative refraction simulation theoretically proved the LHM. Clear negative refractions were observed in refraction experiments with samples of different wedge shapes and different lattices made from this material, and negative effective refractive index n=-1 is measured. Comparing with conventional LHMs, our LHM has the advantages of simpler structure, good impedance match with the air and lower transmission loss.We proposed a new bandpass filter based on SMPCs. The filter working at different frequencies and with different bandwidth could be realized by changing the radius and lattice constant of magnetic photonic crystals. Even reached was a small filter with high quality. Simulations and experiments fit well, showing the filter has low insertion loss, high band rejection, good shape factor and flat passband.Based on SMPCs., different waveguides of odd and even modes were designed and realized. Transmission were experimentally measured to verify the propagation of the waveguides. These waveguides were experimentally shown to be robust against various types of defects and obstacles. Meanwhile, we designed and realized a 90° turn waveguide and waveguides with different substrate and different lattice, showing the flexibility of SMPCs in one-way waveguide design.