Collimating Emission From Photonic Crystal Basedon The Quasi-Zero-Effective-Index

Photonic crystal structure is a new type of artificial material, and its special properties can be used to realize the design of optical waveguide. The light collimating emission is one of the important applications of photonic crystals. In this thesis, the transmission of light wave at the frequency near the edge of the band gap in a two-dimensional square lattice photonic crystal is studied by using the plane wave expansion method(PWM) and finite difference in time domain(FDTD) method.Firstly, we select the corresponding incident light frequency based on photonic crystal band structure. It is found that, directional emission from two-dimensional photonic crystal can be realized if the effe ctive refractive index is near zero. Moreover, the direction of the emitting beam does not depend on the orientation of the crystal lattice but relies on the direction of the crystal surface, which is quite different from the self-collimation phenomenon in photonic crystal.Second ly, based on the numerical simulation of the structure parameters of photonic crystals we use the single variable factor method to analyze their effect. These parameters include the numbers of the transverse and longitudinal grid layers, the width and frequency of incident light-source. We analyze the influences from the variation of each parameter on the light emission. What’s more, we explore the variety law of the collimation property due to the parameters changes, and analyze the periodic light field distribution in crystals, and relative reasons.Thirdly, by means of choosing a different structure system of two-dimensional photonic crystal, we find that for the corresponding quasi- zero-effective-index the beam has a good collimating transmission. Therefore, this method is universal for the two-dimensional square lattice air-hole system, the two-dimensional triangular lattice dielectric-column system and two-dimensional triangular lattice air-hole system.Finally, we make a simple description on the defects and shortcomings in the study process, and give further elaboration and expectation on the application of photonic crystals based on the collimating method.