Investigation On Large Band-gap Photonic Crystals And Their Applications

Photonic crystal is a new kind of artificial electromagnetic materials first proposed in late 1980 s. Nowadays it still attracts great interests among the international scientific society. With the rapid development of electronic information technology, the feature size of integrated circuit chip has reached the limit of classical physics. As electrons being the carriers of integrated circuits, when the size of the chip becomes smaller, the thermal effect caused by coulomb force between electrons will be largely enhanced, which will greatly reduces the performance of integrated circuit and increases the energy loss, and causes various kinds of problems such as slow transit speed of information. The appearance of photonic crystals paves a new way for the study of different structures about the information transmission. And the research of integrated photonic crystal waveguide can effectively solve the problems mentioned above.Due to the unique and advanced optical properties, photonic crystal waveguides increasingly become the hot research area worldwide. However, most previous researches on photonic crystal waveguides only focused on TE waves or TM waves, on both TE and TM waves. While in fact the signal modes in a waveguide are diversified, so the waveguide of two-dimensional photonic crystal with an absolute band gap will be more advanced to the single mode waveguide. It can also guide different polarized waves.To design a photonic crystal waveguide that can guide different polarized waves at the same time, the absolute band gap of photonic crystals should be studied. The photonic crystal with large absolute band gap has the advantage to limit the propagation of electromagnetic waves in a wide frequency range. In this paper, we put forward several new photonic crystal structures. They all have a large absolute band gap. A square-lattice photonic crystal structure was proposed based on circular-ring cylinders and thin cross plates. The calculation process and the influence of operating parameters on the absolute band gaps were presented. It is demonstrated through plane-wave expansion method combined with cut-and-try method that the maximum relative absolute photonic band gap(APBG) reaches 19.026%, which is 10.181% and 712.0359% higher than that in a Ph C made of solid cylinder and connecting veins and that in a Ph C made of dielectric rings, respectively. Moreover, there exist optimum values for the outer radius of the circular-ring cylinders, the relative ring thickness, and the thickness of the cross plates. Furthermore, the influence of the thickness of the cross plates on the relative APBG is quite sensitive.On the basis of the above proposed structure, in this paper, a variety of polarization beam splitters based on photonic crystal waveguides have been proposed, including TE polarization beam splitter, TM polarization beam splitter, T shaped polarization beam splitter for TE waves and TM waves, and the TE/TM optical bridge. With this design, TE waves and TM waves can be separated effectively. In the photonic crystal waveguide, TE and TM waves can be transmitted simultaneously and don’t influence each other. This design is small in size and efficient, which is conducive to the photonic integration.