With the development of optical interconnection and high-speed optical communication, electro-optic modulators have become a research hotspot. Silicon insulator materials have the advantages of compatibility with the complementary metal oxide semiconductor process, high integration, low power consumption and high temperature resistance. There are many electro-optical modulators based on silicon materials. Electro-optic modulators with high modulation rate, small size and easy integration have been studied. The study about electro-optic modulators is of great significance. Therefore, we design a electro-optic modulator with reflective wall based on one-dimensional photonic crystal nanowire cavity. It has a high extinction ratio, large modulation bandwidth and modulation rate. The device has a compact and simple structure and is easy to cascade other silicon photonic devices. The cascade of silicon photonic devices has huge application prospects in the development of integrated optical devices and high-speed and large-capacity communication systems.
This paper proposes a download type electro-optic modulator with reflective wall based on silicon-on-insulator (SOI) one-dimensional photonic crystal nanowire cavity. The main line waveguide, one-dimensional photonic crystal nanowire cavity and download type waveguide are used to form a download type structure with reflective wall. The duty cycle of the nanowire cavity decreases linearly from the center of the waveguide to the two ends, and the doping at both sides of the modulator is introduced to form PN junctions. The finite difference time domain( FDTD) model in the optical simulation software Lumerical is used for simulation analysis. According to the free carrier dispersion effect in the silicon material, when the modulation voltage applied at both ends of the electro-optic modulator changes, the dielectric constant of the nanowire cavity material also changes. The refractive index of the nanowire cavity produces a slight difference, so that the resonant frequency of the cavity changes, that is, the central wavelength of the electro-optic modulator shifts. That is, corresponding to the wavelength of 1550.01 nm, the addition or non-addition of the modulation voltage is equivalent to the "off" state or "on" state of the modulator.
Based on the SOI one-dimensional photonic crystal nanowire cavity (PCNC), an electro-optic modulator with reflective wall is proposed. The incident light is coupled into the one-dimensional photonic crystal nanowire cavity after passing through the main line waveguide, and then coupled again to output through the download type waveguide. The adjustments of the position and number of reflective circular holes in the main line waveguide and the download type waveguide are beneficial to improve the overall transmittance of the device. The nanowire cavity adopts a cylindrical tapered aperture, which makes the beam better confined in the cavity. At the same time, doping is introduced on both sides of the nanowire cavity to form a PN junction, and a low bias voltage is applied to adjust the resonant wavelength of the nanowire cavity, so as to realize the "on" and "off" modulation of the optical signal at the working wavelength. The 3D-FDTD is used to analyze the optical characteristics and electrical performance of the modulator. The results show that the electro-optic modulator can modulate the optical signal with the wavelength of 1550.01 nm, and the transmittance under the "off" and "on" states are 0.0037 and 96.34%, respectively (Fig.14). The modulation voltage is only 1.2 V, the insertion loss is 0.2 dB, the extinction ratio is 24 dB and the size is only 54 μm2. The modulation frequency is 8.7 GHz and the modulation bandwidth can reach 122 GHz, which show that the proposed device can be applied in integrated photonic devices and high-speed optical communications field. In addition, after comparing the performances of the photonic crystal electro-optic modulators (Table 1), one knows that the device proposed here has excellent performances.
This paper proposes a download type electro-optic modulator with reflective wall based on SOI one-dimensional photonic crystal nanowire cavity. The main line waveguide, download type waveguide and one-dimensional photonic crystal nanowire cavity are used to form a download type structure with reflective wall. The doping method is introduced to form PN junctions at both sides of the modulator. Under the action of the modulation voltage, the refractive index of the silicon in the nanowire cavity changes, which causes the migration of defect modes in the nanowire cavity, and the "on" and "off" state modulations of the electro-optic modulator are realized. The electro-optical modulation is simulated and analyzed by the 3D-FDTD model in the Lumerical commercial simulation software. The simulation results show that compared with other electro-optical modulators based on nanowire cavity, the proposed electro-optical modulator has higher extinction ratio, higher modulation bandwidth, higher modulation rate, compact and simple structure, and being easy to cascade other silicon photonic devices. The proposed electro-optical modulator has huge application potential in the development of integrated optical devices and high-speed and large-capacity communication systems.
