| Photonic crystals(PCs)are a kind of artificial microstructures that can control the propagation of electromagnetic waves.They have been one of the most important branches in condensed matter physics since they were proposed.Many optical and optoelectronic devices have been developed based on the excellent properties of photonic crystals,such as optical sensors,all-optical switches,photonic lasers,photonic antennas and etc.In Chapter 2,we theoretically study the topological-like phase transition in photonic crystals,which is controlled by the polarizations and incident angles of electromagnetic waves.We find that the reflection phase at the interface may change from ? to 0 or 0 to ? before and after Brewster angle.The ratio of effective refractive index related to incident angles will change from larger than 1 to less than 1,or vice versa.Furthermore,the photonic band gap characteristics of photonic crystals related to the topological-like properties of photonic crystals are studied.The transition of the band gap characteristics mainly comes from the topological-like phase transition.Moreover,it is found that this kind of topological-like transition mainly occurs on both sides of Brewster angle.Based on this property,it is possible to develop angle-controlled optical switch devices.On the other hand,using photonic microstructures composed of different photonic crystals,the interface states can be obtained,where the field intensity is strongly enhanced at the interface.In Chapter 3,we theoretically study the optical properties of photonic microstructures consisting of dielectric gratings and one-dimensional photonic crystals.It is found that the interface state can be realized in the photonic heterostructure composed of gratings and photonic crystals when they have different forbidden gaps.If the graphene is inserted at the interface between the gratings and photonic crystals,enhanced absorption can be obtained.Such structures are important for new absorption devices. |
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