The Research Of Optical Properties And Application Based On Phyllotaxy Structure Photonic Quasicrystals

In recent years, optical device with graded-index materials get more and moreattention，but its continuous structure get trouble in actually manufacturing. Effectivemedia theory using discrete same medium with different duty ratio can simulate acontinuous different media solve the problem of actual manufacturing, which makephotonic crystal applied in every aspect of photonics technology. Photonic crystal withperiodicity can be used for many kinds of optical device. By adjusting the duty of theperiodic structure of photonic crystals, which can realize different refractive indexdistribution and very high flexibility. But the periodic structure of photonic crystals isanisotropic, result in photonic crystals in simulating rotation symmetry device islimited. As a result, people design photonic quasicrystal based on device the discretestructure to simulate the rotation symmetry device. Because of the photonic crystal canhave a higher rotational symmetry, such as the8-fold,10-fold,12-fold photonicquasicrystal. And my research adopt with phyllotaxy structure photonic quasicrystal tosimulate the rotational symmetry of photonics device, such as Luneburg lens andoptical black hole, phyllotaxy structure has high rotational symmetry, and thus hasexcellent isotropy, thus it can be expected to get better performance of photonics devicewith rotational symmetry.This thesis explored numerically the optical properties of Luneburg lens andoptical black hole which constructed with phyllotaxy structure photonic quasicrystal,and compare the simulated results with that of the devices formed withtwo-dimensional square photonic crystal. The finite difference time domain (FDTD)method was adopted to perform the numerical simulation. FDTD numerical simulationshows phyllotaxy structure Luneburg lens with137.6degrees achieved the bestresolution ratio (resolution ratio is defined as the ratio between full width of halfmaximum of the focal point and the Rayleigh diffraction limit) with the incidentwavelength of512.2nm with TE polarized mode, and its value is0.7029. Theresolution ratio of phyllotaxy structure Luneburg lens with golden angle is0.8265withincident wavelength of508.2nm in comparison with the0.8828resolution ratioachieved with square photonic crystal Luneburg lens at407.8nmwavelength. Simulation results also show the intensity of the focal point will decreasewith the higher resolution ratio. When concerned the maximum focusing intensity，the ratio of phyllotaxy structure Luneburg lens with golden angle is0.9501, which is betterthan the other two structures and exceed the diffraction limit. For the optical blackhole，absorption rate of the phyllotaxy structure optical black hole is96.72%, which islarger than89.71%(absorption rate of square photonic crystal optical black hole). Andthe symmetry of phyllotaxy structure optical black hole is better than square photoniccrystal optical black hole. Simulation results verified that gradient refractive indexphotonics device with phyllotaxy structure showed better isotropy, required lessnumber of discrete dielectric rods with larger minimum radius. Therefore, phyllotaxyshowed advantages in practical applications to fabricate the gradient refractive indexphotonic devices.