1×5 optical splitter for TE modes in air-hole photonic crystal based on self-collimation effect

We propose a novel 1×5 optical splitter (OS) for TE modes based on self-collimation effect in an air-hole silicon photonic crystal. The OS consists of two cascaded resonators which is formed with eight beam splitters. The theoretical transmission spectra of the OS is derived with multiple-beam interference theory. From our analysis of transmission spectra, it is found that the transmission spectra at five drop ports will reach the maximum values while the transmission spectra at two through ports reach zero for resonant frequencies. By scanning the radius of a beam splitter, the relationship between the radius and the reflectivity is obtained. Therefore, by changing the radii of the air-hole in eight beam splitters, we can manipulate the output light-intensity ratio at five drop ports to meet requirement. Theoretically, when reflectivity of beam splitters R 1 =2/11, R 2 =8/11, R 3 =5/8, R 4 =2/5, R 5 =7/12, R 6 =6/7, R 7 =1/2, R 8 =2/3, the light intensity ratio at five drop ports is 1:1:1:1:1. When R 1 =2/7, R 2 =6/7, R 3 =1/2, R 4 =2/3, R 5 =1/7, R 6 =6/7, R 7 =2/3, R 8 =1/4, the light intensity ratio at five drop ports is 2:2:1:2:3. By means of finite-difference time-domain (FDTD) simulations, the numerical transmission spectra of OS can be figured out. The simulation results are consistent with the theoretical results. Considering micro processing technology of silicon materials is already available, this OS can be used in the photonic integrated circuits because of its small size, whole-silicon material and low insertion loss.