Electrode Design Of Lithium Niobate Modulator

With the development of the Internet of things,5g network and other communication fields,the transmission rate of communication system is required to be higher and higher.However,with the increasing scale of semiconductor chip integration,the power consumption of electronic integrated chip is also increasing.At the same time,due to the existence of quantum effect,it will not be able to meet the growth requirements of data processing rate and transmission rate.The speed of information transmission using light wave is very fast,and taking light as the carrier of information can obtain higher information capacity and larger bandwidth.Therefore,photonic integrated circuits(PIC)is the key technology to promote the development of modern optical communication network.Lithium niobate modulator has been widely used in business because of its high bandwidth,high extinction ratio and high modulation efficiency.However,due to the small refractive index difference between its cladding and core,its optical mode size is large,which is not convenient for integration with silicon-based optical devices.While the thin-film lithium niobate modulator has the above advantages,its size is smaller,which is suitable for integration with silicon-based optical devices.Generally,the microwave signal of Lithium Niobate Thin Film modulator modulates the light wave phase through the uniform coplanar waveguide(CPW)traveling wave electrode.In order to obtain a lower half wave voltage,it is necessary to increase the length of the modulation region.However,due to the existence of microwave loss and rate mismatch,this method will reduce the bandwidth.Therefore,in order to improve the performance of the modulator,it is particularly important to use the electrode design to improve the microwave transmission characteristics.In this paper,Lithium Niobate Thin Film modulator is a sampling module applied in optical ADC chip.In order to improve the performance of Lithium Niobate Thin Film modulator and realize the coupling with silicon-based devices,the main contents and innovations of this paper are as follows:1.By studying the model of Lithium Niobate Thin Film modulator,the expression of half wave voltage is obtained.Through this relationship,combined with the results of microwave transmission,light field and electric field distribution,the characteristics of half wave voltage in the full frequency band can be analyzed to guide the optimization of modulator electrode.2.In order to realize the integration of lithium niobate thin film devices and silicon devices,the coupling of light from silicon wave to lithium niobate thin film is designed,and the coupling efficiency of different types of lithium niobate thin films is analyzed.3.In order to reduce the microwave transmission loss,the T-shaped track is added into the electrode gap,and the electrode is designed in a piecewise staggered way.Compared with the general uniform coplanar waveguide electrode,the microwave loss is lower.Finally,the lithium niobate thin film modulator realizes the performance of DC half wave voltage of 1.59v and 40GHz half wave voltage of 2V under the modulation length of 2cm.It is expected that the 3dB bandwidth can reach 60GHz.