Measurement Of Polarization In LiNbO₃ Waveguides

Quantum communication has been rapidly developed in recent years because of the absolute security of the transmitted information.The interrelation and mutual influence between polarization-entangled photon pairs makes it play a significant role in quantum computing and communication.Therefore,polarization-entangled photons are realized.The generation,manipulation and measurement of pairs are of great significance in quantum communication.This paper focuses on the measurement of the polarization state of light,whereas the measurement of light polarization was previously performed in free space,but with large errors and high losses.In recent years,the polarization state of light can be measured by writing a femtosecond laser into glass.The non-adjustable glass makes the processing more cumbersome.The innovation of this dissertation is to design a method for measuring the polarization state of light in a LiNbO3 waveguide chip by only controlling the voltage.This method integrates polarization rotation and polarization splitting into the LiNbO3 waveguide to realize the polarization state of light.measuring.The obvious advantage of using this method of measuring the polarization state of light is that only one control factor is easy to adjust,the loss is small in the confined space,and the integrated volume is small,so it has high application value in quantum communication.In order to achieve accurate measurement of the polarization state of light,it is necessary to constantly optimize the design parameters of polarization rotation and polarization beam splitting to achieve the highest extinction ratio.First,the propagation of the light field in the waveguide is analyzed by numerical simulation.The parameters for the polarization splitting to achieve the ideal extinction ratio are designed,and then the outer waveguides are processed by Ti diffusion to process the waveguide.Taking into account the process accuracy,multiple sets of samples are measured experimentally,each set.The coupling length of the sample,waveguide width(Ti strip width),and waveguide spacing(Ti strip edge spacing)are all different.The experimental results are analyzed and the coupling length of the first samples,the polarization beam splitter length,and the buffer layer Si O2 width The design parameters were optimized.After optimization,the 30-d B TE polarization spectroscopic extinction ratio was measured,and the polarization rotation extinction ratio reached 20 d B or more.Theoretical studies and experiments verify the feasibility of integrating polarization rotation and polarization splitting to measure polarization state of LiNbO3 waveguides,and can be used to measure the polarization state of light in quantum communication.