Ultracompact ultrafast-switching-speed all-optical 4 × 2 encoder based on photonic crystal

A novel two-dimensional photonic-crystal-based all-optical encoder was designed, tested, and optimized. The structure is built on a linear square-lattice photonic crystal platform. An ultracompact, simple design occupying an area of only 128.52 μm 2 is constructed, 50 % smaller than the smallest design known to date. Ultrafast switching speed with the lowest known delay time is achieved. The proposed design consists of one ring resonator with cylindrical silicon rods suspended in air. No auxiliary or bias input is required for its operation. The proposed platform is not sensitive to the applied input phase shift. Finite-difference time-domain and plane-wave expansion methods were used to analyze the structure and optimize the radius of the rods at 1.525 µm, with radius of the inner rods of 0.19 a , for successful operation, resulting in ultrafast switching speed of 10 THz and shorter delay time reaching 0.1 ps. This maximum switching speed is two times faster than recent literature reports. The contrast ratio is calculated to reach an acceptable record of 7.1138 dB. The trade-off between the switching speed and contrast ratio was also examined.