Design and experimental verification of a novel anisotropic photonic crystal band edge device

Abstract

We have been studying a novel ID anisotropic photonic crystal structure which can be designed to have a strong resonant effect, a very low group velocity over a specific bandwidth. The structure requires two anisotropic layers and one isotropic layer per period and was first introduced by Figotin and Vitebskiy. By the careful design of the parameters of the structure, we can find a special band edge point which has fourth order degeneracy, and is called degenerate band edge (D.B.E). It was predicted that in the case of a transmission resonance in the vicinity of the D.B.E, the resonant field intensity increases as N 4 , where N is the total number of periods, while in the case of a regular band edge, the field intensity is proportional to N 2 . By making a comparison among different anisotropic materials, we have found that the giant resonant effects in the vicinity of the D.B.E also need a large anisotropy of the materials. However, materials with the required anisotropy at optical wavelengths are difficult to find and so we use equivalent form-birefringence layer to replace the anisotropic layer in our photonic crystal structure design. In order to verify our design, we make a real device for use at microwave frequencies using a rapid-prototyping tool. Our measurement results show that using form-birefringence to design this novel device is feasible and can push this novel photonic crystal structure to a lot of potential applications.