Photonic Crystal 180° Ring-Shaped Hybrid: From Microwave to Optics

In this letter, a 180° ring-shaped hybrid based on the photonic crystal structure (PCS) is presented. The ring hybrid is designed for the operation wavelength of 1550 nm. Initially, a 180° hybrid is a design based on conventional microwave procedures. Different wave behavior inside the structure in THz and microwave frequency band has caused the wave propagation in this structure to change especially in terms of phase. By analyzing the field distribution within a structure, the rod arrangement is modified. In proposed structure, the phase difference between the output ports is greatly improved (about 90°). Also, by reducing the leakage and improving the matching, the output power of the ports tends to half power. Moreover, 32 nm wavelength shift is improved. The proposed structure's reflectance value is less than 20 dB at the desired wavelength. The power splitting ratio between the two output ports is improved up to -3.7 dB and the power of the isolated port is less than -20 dB. This work has been analyzed using the FDTD method.