Research On Y-shape Power Splitters Based On Broadband And All-direction Super-collimation Effect Of Two-Dimensional Photonic Crystals

Photonic crystals(PCs) are periodic dielectric materials which can be used to control light propagation on wavelength scale and compared to “optical semiconductor”. Based on the special properties of PCS, people researched and developed various function devices, such as light switches,light couplers, wavelength division multiplexers, filters and splitters.In this thesis, by combination of theoretical analysis and numerical stimulations, we analysis the equi-frequency lines of the second band surface of ideal two-dimensional photonic crystal, which can be used to explain the existence of self-collimation effect. Then we present two-dimensional elliptical photonic crystal structures, and study the broadband all-angle self-collimation dispersion properties and their applications in power splitters. Firstly, we calculate its dispersion relation by the Plane Wave Expand Method. The calculated results show that there exist straight-like equi-frequency lines spanning over the whole First Brillouin Zone within a relative broad band for TE polarization. These straight-like equi-frequency lines are used to realize broadband all-angle super-collimation transmission. Meanwhile, we research the properties of self-collimation transmission and the relationship between all-angle super-collimation transmission and structure parameter, find out that self-collimation transmission should meet the condition vgx≠ 0,vgy≈ 0, bandwidth also increase with the increase of La. When ρ is near 2.1, bandwidth is biggest. Considering the craft, we choose La=0.9a and ρ=2.1. Based on the above results, one kind of Y-shape power splitter is designed. Finite-difference Time-domain(FDTD) simulations reveal that this Y-shape splitter has good performance for both two-dimensional point source and Gaussian source. The splitters based on broadband and all-angle supercollimation effect have advantages of compacting, large bandwidth,needless of exact coupling and easy integration etc, which holding great potential in photonic devices integration and directional coupling.