Si Photonic Crystal Nanocavity Electro-optic Modulator with wavy PN Junctions

摘要

A new type of photonic crystal electro-optic modulator with wavy PN junction has been designed. The proposed device is mainly composed of photonic crystal line defect waveguide and triangular of lattice circular air holes are applied in Si photonic crystal slab. SiO_2 is used as substrate material with a thickness of 2 μm, reverse bias voltage is added to the upper and lower sides of the photonic crystal slab. According to the plasma dispersion effect, when the reverse bias voltage is applied on both sides of the photonic crystal, the refractive index of the doped silicon-based slab will change by introducing wavy PN junction in the center of the waveguide. After that, the transmittance of light is changed, achieving the purpose of modulation. Finite-difference time-domain (FDTD) method is used to calculate the steady-state field intensity distribution and mode field distribution. The results show that when applied voltage is 1.2 V, it has a refractive index difference of 0.0025 compared with the voltage of 0 V, the narrow bandwidth on-off modulation of transverse electric (TE) mode at 1550.68 nm can be realized. The extinction ratio of the device is as high as 30.8 dB, the insertion loss is 0.5 dB, the Q value is 14097. Besides, the modulation rate is as high as 7 GHz.