Design And Application Of Electoroptic Modulator Based On Coplanar Waveguide

With the improvement of the measured electric field frequency,the electro-optic external modulation method is applied to the test system for electric field test.As the key of external modulation,the electro-optic modulator has faster conversion speed,so the electro-optic modulator is more widely used in the test system.The most typical electro-optic modulator is applied to the high-speed photodetector test system.With the improvement of the bandwidth of high-speed photodetector,higher requirements are putting forward for its test.The photoelectric detector test system based on electro-optic sampling principle converts the electrical signal changing with time into optical signal,and the electro-optic modulator is one of the important components of the photodetector test system.The system has higher requirements for the structural parameters and performance of the electro-optic modulator.In the design of electro-optic modulators,coplanar waveguide structure which is less physically limited and easier to manufacture.In addition,the refractive index of the electro-optic crystal in coplanar waveguide and the path of light passing through the substrate of coplanar.Based on the analysis of the research status of electro-optic modulators based on coplanar waveguide,the coplanar waveguide with complex boundary shape is analyzed by conformal mapping,and the expressions of its characteristic impedance and dielectric constant are derived.The relationship between coplanar waveguide structure and characteristic impedance is studied,and the relationship between structure parameters and characteristic impedance is obtained,which is modeled in electromagnetic simulation software the influence of this parameter structure on the characteristic impedance and transmission parameters is analyzed.The electro-optic modulator is applied to the photodetector test system.Based on the electro-optic sampling principle,the overall design of the test system is analyzed,and the design scheme of the sampling optical path and excitation optical path of the test system is given.The measurement and control program of the high-speed photodetector test system based on virtual instrument technology is designed and implemented,including the data communication subsystem,the stepping motor motion subsystem,the control system and the control system data acquisition subsystem,data storage subsystem,and human-computer interaction interface subsystem.Each modules cooperate with each other,and finally realizes the test of high-speed photodetector.The experimental result shows that the electro-optic modulator based on coplanar waveguide meets the requirements of the photodetector test system.The numerical analysis and simulation test are carried out before processing,compared with the real test data of coplanar waveguide.It is proved that the transmission data of the designed coplanar waveguide simulation model is in good agreement with the measured data,and the simulation test results provide the basis for the real test to ensure the transmission characteristics of coplanar waveguide,the reference basis should be provided.When it is applied to the photoelectric detector test system,the system runs stably and has good reliability.It provides a new idea for the structure optimization of electro-optic modulator and the realization of photodetector test system.