Study On Modulator Of Single Crystal Lithi?m Niobite Films

Most commercial electro-optic modulators are of bulk structures with large size and low integration,resulting in high half wave voltage and high power loss.However,thin film devices have the advantages of miniaturization,low power consumption and cost-effective,which can meet the long-term performance requirements.Taking single crystal LiNbO₃ thin film electro-optic modulator as the research object,this paper optimize structure of the optical splitter of M-Z electro-optic modulator firstly.Secondly,the M-Z electro-optic modulator based on LiNbO₃ thin film is simulated and optimized,in order to reduce Half-wave voltage.The main research achievements are as follows.1.LiNbO₃ optical waveguide mode simulationThe mode of waveguide of the M-Z electro-optic modulator is single-mode,in this paper,the software finite element is used to simulate the mode of single crystal LiNbO₃thin film ridge waveguide mode,and thus determine the single-mode transmission size of single crystal LiNbO₃ thin film ridge waveguide with the film thickness of 450 nm,among which the light wave wavelength is 1550 nm.Results show that under the condition of 1?m ridge width,compared with the etching depth of 150 nm,when the etching depth is350 nm,the optical field of transmitting E^x₁₁(quasi-TE)mode in the ridge waveguide is more stable,the mode radius is smaller and the optical power is more concentrated.Therefore,the etching depth of single mode transmission ridge optical waveguide is 350nm.2.Research on simulation modeling of LiNbO₃ optical splitterIn order to reduce the transmission loss of optical splitter and improve the device integration,the performance of Y type,double circular-arc type,cosine type and rising anti-sinusoidal optical splitter based on single crystal LiNbO₃ thin film is studied by finite element simulation software under different structural conditions,results show that cosine optical splitter has obvious advantages in realizing lower integration and lower optical transmission loss.When G is 15?m and L is 20?m,cosine optical splitter can achieve lower transmission loss and higher integration density,according to the simulation results,the mask layout of the optical splitter is drawn.3.Research on simulation modeling of the M-Z electro-optic modulatorThrough the comprehensive simulation and optimization of the electrode parameters of M-Z electro-optic modulator,the matching of the microwave velocity and the optical wave velocity of the electro-optic modulator is completed,as well as the matching of the characteristic impedance of the traveling wave electrode with 50?,and then realize a smaller half wave voltage of the modulator,among which the microwave frequency is 20GHz and the electrode length is 1 cm.The last indicate that when the thickness of buffer layer is 2.2?m,electrode thickness is 2.5?m,electrode spacing is 4?m and the source electrode width is 16?m,the effective refractive-index of microwave is 1.7955,which can well match the effective refractive index of light wave 1.7994,the characteristic impedance of electrode is 47.955?and the half wave voltage of modulator is 4.35 V.Besides,according to the simulation design,this paper proposes a method which is easy to realize velocity matching of microwave and lightwave,that is,adding two cavities and a central cavity in the buried layer.The height of the three cavities is not higher than the thickness of the buried layer and the width is not less than the corresponding electrode width above,which makes it easier for the electro-optic modulator to realize the velocity matching of microwave and lightwave in a higher electric bandwidth,and thus the communication speed is faster without increasing the half wave voltage.4.Optical test of optical splitterOptical tests are carried out on four kinds of optical splitter,which are Y-type,double circular-arc type,cosine type and rising anti-sinusoidal type.Comparing the insertion loss of the test splitter with the transmission loss of the simulation data,the cosine optical splitter has a better structure.When G is 15?m and L is 20?m,cosine optical splitter can achieve lower transmission loss and higher integration density,and thus the simulation data are verified to be basically correct.