Highly Compact Circulators in Square-Lattice Photonic Crystal Waveguides

Abstract

We propose, demonstrate and investigate highly compact circulators with ultra-low insertion loss in square-lattice- square-rod-photonic-crystal waveguides. Only a single magneto- optical square rod is required to be inserted into the cross center of waveguides, making the structure very compact and ultra efficient. The square rods around the center defect rod are replaced by several right-angled-triangle rods, reducing the insertion loss further and promoting the isolations as well. By choosing a linear-dispersion region and considering the mode patterns in the square magneto-optical rod, the operating mechanism of the circulator is analyzed. By applying the finite-element method together with the Nelder-Mead optimization method, an extremely low insertion loss of 0.02 dB for the transmitted wave and ultra high isolation of 46 dB∼48 dB for the isolated port are obtained. The idea presented can be applied to build circulators in different wavebands, e.g., microwave or Tera-Hertz.

Polarization-Independent Circulator Based on Composite Rod of Ferrite and Plasma in Photonic Crystal Structure

“…Circulators are a kind of nonreciprocal device that play an important role in optics and photonics. They can be used for protecting useful signals from harmful reflections, reducing the unwanted wave interferences; they can also be used for extracting feedback signals for detectors or monitors [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”

“…These works operated in TE polarization. Furthermore, several kinds of novel low-symmetry circulators were investigated by Jin and Dmitriev [ 20 , 21 ]. A very low splitting factor was used in their design, making their circulators feasible for the microwave or terahertz region.…”