Design And Optimization Of PLZT Waveguide Electro-optic Modulator And Its Travelling Wave Electrode System

As a key device in the high capacity optical fiber transmission system and high speed photoelectric information processing system,high-speed electro-optic modulator has become a hot research topic at home and abroad.At present,we urgently need to develop a small-size high speed electro-optic modulator.This article selects the PLZT(Pb_1-xLa_x(Zr_yTi_1-y)_1-x/4O₃)ferroelectric ceramics film materials as the research object,focusing on PLZT electro-optic modulator and its travelling-wave electrodes system design and preparation,and its working characteristic is tested.PLZT ferroelectric ceramics is a relatively new type of transparent material,having large electro-optic coefficient,high refractive index,good pervious to light,with which electro-optic devices have small half-wave voltage,low power consumption,polarization insensitivity,etc.At the same time,PLZT waveguides can be prepared in either direction,and this feature enables it to be flexibly integrated into the substrate.In this paper,PLZT materials ridge type optical waveguide structure is designed,by using effective index method to calculate the effective refractive index of the medium,the parameters not only has a reference value to optical waveguide design,but also has impact on the electrode system wave velocity matching and characteristic impedance matching.Using the Mach-Zehnder?M-Z?interferometer structure as the modulator electro-optic interaction zone,the optical waveguide performance parameters are calculated and optimized by using the beam propagation method.The simulation results show that the modulation depth can reach more than 90%when the optical waveguide ridge is 0.6um and the length of modulation arm is 10mm.The electrode structure is the key factor affecting the electro-optic modulator.Based on the basic theory of microwave transmission line,the electrode system of the PLZT electro-optic modulator is designed and simulated by using HFSS.Using coplanar waveguide?CPW?electrode structure,the influence of the gold electrode thickness and width,electrode spacing,buffer layer thickness on wave velocity matching and characteristic impedance matching are study,and the relationship between them was used to optimize design of electrode size.Interaction area,transition area and interface area are divided to three block to be designed,and combining the S parameters,the interaction length,transition area chamfering radius,interface area linear distance are also optimize designed.Then we get a 3dB bandwidth is about 10 GHz,the overall size is not more than 1 cm² CPW travelling-wave electrode system.Finally,the modulator was prepared by ultraviolet lithography,plasma reaction etching,electroplating,cutting,polishing and other technological processes.The test platform was built by using the optical wave test system,vector network analyzer and spectrometer,and the performance test was carried out for the sample prepared by the modulator,and the experimental results were analyzed.Built test platform by using optical wave test system,vector network analyzer and spectrometer.The test results show that the on-chip loss is 10.83dB,the half-wave voltage is about 24V,and the bandwidth is 2GHz.The experimental results are basically consistent with the simulation results.