Magnetically tunable two-dimensional photonic crystal by self-assembling in magnetite magnetic fluid

Abstract

Under applied magnetic field, phase separation happens in the magnetic fluid and then periodic structures are formed. These periodic structures are actually photonic crystal and made of magnetic materials. The magnetic-field-sensitive property of the constitute materials provides the possibility of tunability for the band gap of the photonic crystal. The model of the two-dimensional photonic crystal is established according to the experimental experience about the structure formation in the magnetite magnetic fluid in the literature. The standard plane-wave expansion method is employed to calculate the band structures of the photonic crystal. Simulation results indicate that the forbidden bands onlv exist in the case of TE waves (electrical field is along the length of the columns) under relatively high magnetic fields and no forbidden bands happen for low magnetic fields. For the TM waves (magnetic field is along the length of the columns), no forbidden bands are resulted in the whole range of the m agnetic fields. Moreover, the mid frequencies of the band gaps of the TE waves shift to lower values at higher magnetic fields. While the widths of the band gaps increase with the magnetic fields. The theoretical results presented in this work propose a different way and system for fabricating tunable two-dimensional photonic crystal. Nonetheless, further experiments are required to optimize the correlative parameters of the tunable photonic crystal and confirm these conclusions. And then the involved tunable photonic devices may be exploited.