Fano Resonance In 2D Photonic Crystal And The Applications

Fano resonances,originating from the interference between a discrete localized state and a continuum,are prevailing phenomena in diverse physical systems.Besides the interacting quantum systems,Fano resonances are widely popular in photonic crystals,electromagnetic metamaterials,plasmonic nanostructures and so on.Compared with Lorentzian resonance which is spectrally symmetrical,Fano resonance demonstrates asymmetrical line shape and the sharp change of reflection or transmission is more beneficial to achieve high-performance optical devices.Therefore,Fano resonance can be exploited in optical switches,filters,optical sensors etc.The dissertation mainly consists of the following parts:1. In this paper,two Fano resonance structures based on square lattice photonic crystal and triangular lattice photonic crystal are designed.The Fano resonance is realized by a photonic crystal cavity side-coupled with a partially transmitting element implemented by etching one blockade in the photonic crystal waveguide.The photonic crystal cavities of two Fano resonance structures are both composed of three dielectric rods.Exploiting the cavity which consists of three dielectric rods is aimed to reduce the scattering loss of the cavity and enhance the quality factor and the extinction ratio.Due to the amplitude of the continuum contribution can be controlled by placing a partially transmitting element in the photonic crystal waveguide and the coupling distance decide the interference effect between the cavity and the partially transmitting element.Therefore,by optimizing the structure parameters,the Fano resonance structure consists of the square lattice of dielectric columns,with extinction ratio of 62d B and the peak loss of 0.32d B and the Fano resonance structure consists of the triangular lattice of dielectric columns,with the extinction ratio of 62d B and the peak loss of 1.2d B.2. For the pressure sensing application,the Fano sensors with square lattice Ga As rods and triangular lattice Ga As rods are studied.The pressure is applied from 0GPa to 2GPa and sensitivities of two Fano sensors are 9.15nm/GPa and 12nm/GPa,respectively.3. For the refractive index sensing application,the Fano sensors with square lattice Si rods and triangular lattice Si rods are also studied.The refractive index changed from 1 to 1.01.Sensitivities of two Fano sensors are both 800nm/RIU,and the FOM*are 2800 and 2900,respectively.4. For the all-optical switch application,the all-optical switches based on the square lattice of dielectric columns and the triangular lattice of dielectric columns with nonlinear coefficient 9?10^{-1 7}m²/W are presented.The extinction ratio,the peak loss and the threshold power level for the square lattice of dielectric columns are 61d B,0.29d B,420W/?m²,respectively.Moreover,The extinction ratio,the peak loss and the threshold power level for the triangular lattice of dielectric columns are 40d B,1.4d B,41W/?m²,respectively.To reduce threshold power level for all-optical switch,graphene material with nonlinear coefficient10^{-1 5}m²/W is used and cavity is optimized.The threshold power level for the square lattice of dielectric columns is 0.3W/?m²Furthermore,the rise and fall times of the switch are obtained by 0.3ps and 0.6ps.