Polarization Analyzer Based On Lithium Niobate Waveguide

Optical signal is another important information propagation carrier in addition to electrical signals,it plays an important role in quantum communication and quantum computing.Compared with traditional communication methods and computing methods,quantum communication and quantum computing have their own outstanding advantages,such as security,high efficiency and so on.Therefore,the generation and measurement analysis techniques of polarization entangled photon pairs are very important,and it is necessary to focus on them to promote the development of quantum communication and quantum computing technologies.In this paper,a method for analyzing the polarization state of light by using lithium（Ti）diffused lithium niobate（LiNbO₃）waveguide is proposed.The polarization rotation and polarization filter components are integrated on the same piece of lithium niobate substrate.Adjusting the applied voltage enables measurement and control of the polarization state.In addition to this,the original measurement method has been improved.The polarization rotating portion uses the electro-optical effect of the lithium niobate crystal to add three electrodes in the y direction of the x-cut,z-propagating Ti-diffused lithium niobate crystal,and then deforms the refractive index ellipsoid by applying a voltage thereon,The optical axis of the lithium acid crystal rotates,thereby changing the polarization state of the input light,and completing the control of the polarization state of the input light.The polarizer portion is designed using the spatial surface plasma effect.Transverse Magnetic（TM）mode and metal surface plasma oscillations are coupled to each other to produce a surface plasmon mode that is confined to a very small area near the interface between the waveguide and the metal,thus retaining only the transverse electricity（Transverse Electric）,abbreviated TE)mode.This part of the device structure is quite simple and has a fairly high degree of integration.Compared with the traditional method of measuring the polarization state of light,the lithium niobate waveguide has obvious advantages.Compared with the transmission in free space,the loss caused by the adjustment of the optical path and the internal loss of the waveguide are relatively small,The polarization state is analyzed with high integration,small volume and high reliability.