1×7 optical splitters in a silicon photonic crystal

In this paper, we report 1×7 optical splitters (OSs) with different splitting ratios in a rod-type silicon photonic crystal. Each OS is based on cascaded self-collimation ring resonators (CSCRRs) which consist of eight beam splitters formed by varying the radii of the rod. Light beams propagate in the CSCRR employing self-collimation effect. The theoretical transmission spectra at different outputs are analyzed with multiple-beam interference theory. With eight beam splitters properly selected, self-collimation light beams can come out from seven output ports with different light-intensity ratios. The transmission spectra at output ports are investigated by using finite-difference time-domain (FDTD) method. The simulated results agree well with the theoretical predictions. As self-collimation beams can propagate without defect waveguides and can intercross without disturbance loss, this CSCRR is very compact and low-cost to produce. For the operating wavelength 1550nm, its size is just 13μm×18μm. The proposed OSs may have potential applications in photonic integrated circuits.