Tunable Optical Properties Of Magnetic Fluids Photonic Crystal Slab And Its Application

Magnetic fluid is a new type of magnetic nano-materials.It has fluidity of liquid and magnetism,and its refractive index has tunable characteristic.The tunable nature of the magnetic fluid facilitates the fabrication of novel optical devices such as magnetic field sensors,tunable optical buffers,etc.It is well-known that light with a frequency lying within the photonic band gap can be guided or spatially localized by the photonic crystal?PC?structure with certain line or point defects.Utilizing this mechanism,the photonic crystal device has the characteristic that the conventional device does not have.Due to its small size,it is the ideal choice for integrated device in the future.In this paper,we shall firstly briefly state the introduction of magnetic fluid and photonic crystal.The second chapter reviews relevant research related to the electromagnetic theory of light and numerical calculation.What's more,Section 2.2briefly states the basic idea of plane wave expansion method,finite-difference time-domain method and finite element method.The third chapter devoted to the basic aspects of two different types of photonic crystal slabs.And the details of line defects and point defects are given.In the fourth chapter,a kind of W1 line-defect waveguide based on alternative-row-elliptical-hole photonic crystal with triangular lattice is proposed for compact.The elliptical air-holes are infiltrated with magnetic fluids to realize the on-line tunable slow light.The plane-wave expansion method is employed to investigate the slow light properties numerically.The ultralow dispersion criterion is employed to evaluate the slow light performance.Through varying the major and minor axes of the elliptical air-holes,the optimized structure with high performance of slow light is obtained.The average group index decreases from 13.70 to 13.31 and the normalized delay bandwidth product increases from 0.524 to 0.544 when the magnetic field factor?_||changes from0 to 1.The corresponding wavelength bandwidth??centering at?₀=1550 nm varies from 59.26 to 63.33 nm.In the fifth chapter,a kind of photonic crystal magnetic field sensor is proposed and investigated numerically.The shoulder-coupled resonant cavity is introduced in the photonic crystal,which is infiltrated with magnetic fluid.Through monitoring the shift of resonant wavelength,the magnetic field sensing is realized.According to the designed infiltration schemes,both the magnetic field sensitivity and full width at half maximum increase with the number of infiltrated air holes.The figure of merit of the structure is defined to evaluate the sensing performance comprehensively.The best structure corresponding to the optimal infiltration scheme with eight air holes infiltrated with magnetic fluid is obtained.