A 1×4 LiNbO<sub>3</sub> electro-optic switch is proposed based on Mach-Zehnder interference structure. The optical switch is composed of three 1×2 MZI switch units, each of which includes Y branch, interference arm and directional coupler. The phase difference of the light propagating on two interference arms is generated through the loaded bias voltage, and the switching between the two output ports of the MZI switch unit can be realized. The parameters of Y branch and directional coupler of optical switch are designed and optimized, and the performance of the whole device is simulated. The total length of the device is 5.8cm and the insertion loss is 0.54dB. The extinction ratio bandwidth larger than 20dB reaches 100nm, and the maximum extinction ratio at the wavelength of 1550nm is 33dB. The function of optical switch with four-channel gating is realized. The proposed optical switch is expected to be used in the fields of optical interconnection and optical signal monitoring on high-speed integrated chips.
Integrated array optical switch puts forward higher requirements for switch time and switch voltage. In order to achieve lower switch voltage and shorter switch time, the theoretical model of coplanar waveguides (CPW) electrode is established for Lithium niobate (LiNbO<sub>3</sub>) optical switch, and a novel structure with thickening buffer layer between electrodes is proposed in this paper. Then the modulation bandwidth and electro-optic overlap integral are qualitatively analyzed and optimized by finite element method (FEM). The simulation results show that the electro-optic overlap integral increases gradually with the raising of buffer layer thickness between electrodes. The switch voltage of the optical switch is about 5.7V, which is lower than the traditional electrode structure. The switch time is about 0.48ns. This new structure contributes to reducing the half-wave voltage of the modulator and can be potentially used in the field of electro-optic modulation.