Electro-optical sampling-based performance characterization of optoelectronic devices,due to its higher temporal resolution,is widely used for pulse parameter testing of high-speed photodetectors. As the core component of the electro-optical sampling system,the wafer slide is the key carrier of the electro-optical interaction. Currently,the slide is primarily fabricated using a wet etching process. Wet etching is to achieve the purpose of etching through a chemical reaction between the chemical etching liquid and the material required to be etched on the wafer,which requires a high grasp of the etching time,and the problems of over-etching and uneven etching will inevitably occur when the coplanar electrode pattern with high precision is manufactured. Gallium arsenide (GaAs) chips (after surface polishing) will be naturally oxidized in the air at room temperature,and the natural oxide layer on the surface of the wafer mainly contains Ga₂O₃,As₂O₃,As₂O₅ and other compounds. During the wet etching process,these oxides are easy to react with corrosive liquids such as TiW and Ni to produce loose precipitates attached to the surface of the wafer. The device surface appearance and coplanar electrode adhesion are affected. The Ni layer used for wet etching is used as a hard mask for etching Au material. The stress of the Ni layer is large,and the process of etching Ni will also cause the thin linewidth Au conductor film which has a small bonding area with the GaAs substrate to fall off. As a result,the wafer formation rate is low,which seriously affects the electric-optical field interaction efficiency and reduces the accuracy of electro-optical sampling information.To solve the above problems,a coplanar waveguide structure with limited floor thickness and limited medium thickness is designed in this paper. GaAs material is used as the slide substrate. The material has a very small static birefringence effect and is not sensitive to temperature change,so it is a single crystal with good optical properties. In addition,the ideal characteristic parameters of the coplanar waveguide electrode are obtained according to the conformal conversion theory. By analyzing the effects of different signal electrode widths,different electrode gaps and different electrode spacing ratios on the characteristic impedance under the same substrate thickness,the optimal solutions of each parameter are obtained,and a mathematical model of the wafer slide electrode structure is established. By setting the middle electrode width,electrode spacing,simulation frequency and other conditions,different electrode lengths were inserted into the high-frequency electromagnetic structure simulation software to simulate the transmission characteristics and reflection characteristics curves. The simulation results show that the electrode length has little influence on the reflection characteristic coefficient,and the transmission characteristic coefficient of the coplanar waveguide changes with the frequency,and as the electrode length increases,the transmission characteristic coefficient of the coplanar waveguide changes with the frequency. The roll down of the transmission characteristic coefficient gradually increases,thus the optimal solution of the electrode length is obtained.At the same time,combined with the actual processing technology of wafer slide electrode and the actual testing requirements of optoelectronic devices,the electrode length is processed into multiple structures such as 2 mm,4 mm and 6 mm. On the other hand,by combining the photoresist mask pattern plating and ion beam etching,the problems of coplanar electrode shedding and pattern plating are solved,and the wafer slide with a bright surface and clear electrode pattern is obtained. Finally,we use a vector network analyzer to verify the electrode transmission characteristics of the prepared slide. The experimental results show that the slide has good transmission characteristics and improves the transmission efficiency of high-speed optical signals. It can be used for on-chip sampling information detection of 120 GHz high-speed photoelectric devices,which is expected to greatly improve the test accuracy in on-chip sampling information detection. It is of great significance to the detection technology of high-speed optoelectronic devices.