Properties Of Optical Propagation Of Magneto-photonic Crystals With Composite Magnetic Materials

Photonic crystals are artificial materials in which the media are arranged as periodic components,photonic crystals containing magnetic materials are called magneto-photonic crystals.Under the action of external magnetic field,photonic crystals with single magnetic defect layer or multiple magnetic defect layers can enhance magneto-optical effects significantly,which can be used in the areas of magneto-optical isolators and magnetic field sensors widely.The ion-doped YIG films with strong magneto-optical effects are chosen as the magnetic layers of magneto-photonic crystals generally,which are benefit to realize the miniaturization of optical devices.However,the temperature of growing the YIG film is so high that incompatible with existing semiconductor integration technology,therefore,it is difficult to fabricate integrated optical devices by using the YIG film in practice.According to above problems,a way of optimizing the properties the magnetic materials is presented,that is using the sol-gel process to fabricate composite magnetic materials by Si O₂/Ti O₂matrix doped with magnetic nanoparticles Co Fe₂O₄with a certain volume fraction,the composite magnetic materials serve as the magnetic layers of one-dimensional magneto-photonic crystals not only have strong magneto-optical effects,but also can avoid the problems of excessive temperature and difficulty of the growth in the actual process.Because of the absorption of magnetic nanoparticles Co Fe₂O₄for the light wave,the transmittance and reflectivity of the light will reduce,in order to offset the loss of light wave and improve the performance of magneto-photonic crystals,we propose to use a gain medium to achieve loss compensation.In fact,the volume fraction of magnetic nanoparticles and the direction of external magnetic field both affect the performance of magneto-photonic crystals.On the basis of the different doping concentration and the direction of the external magnetic field,the transmission-type and reflection-type one-dimensional magneto-photonic crystals with composite magnetic materials are designed and used in magnetic field sensors and magneto-optical isolators.The 4 by 4 transfer matrices method is used to calculates the sensitivity of the magnetic field sensors and the optical properties of magneto-optical isolators.The results of calculations show that by adding composite magnetic materials and gain media to one-dimensional magneto-photonic crystals can enhance the magneto-optical effects of the magneto-optical isolators significantly,the transmission spectra and reflection spectra of the optical isolators can be improved,as well as the sensitivity of the magnetic field sensors can be improved simultaneously,which plays an important role in the optical field.