Polarization Entangled State Light Source Based On Nonlinear Optic Waveguide

In recent years,research on quantum science information science is flourishing,and optical-based quantum information processing requires high-quality entangled light sources.The integrated optical waveguide separates the optical path from the complex linear optical path,integrating functions,miniaturizing the optical device,and making the light wave easier to control.This paper is to design an optical waveguide chip that integrates the generation of polarization entangled light source and the separation of photon pairs,which can realize integrated,high stability,high photon generation efficiency and high entanglement polarization entangled light source.Firstly,based on the principle of nonlinear optics,the advantages and disadvantages of entangled light sources are compared in different ways,and the spontaneous parametric down-conversion of second-order nonlinear effects used in this paper is derived to generate photon pairs.This paper introduces the two-photon spectroscopy theory for analyzing spontaneous parameter down-conversion analysis and the numerical methods used for simulation analysis of optical waveguides,including effective refractive index method and beam propagation method.These theoretical analyses will provide guidance for the simulation analysis design and experiments of optical waveguide devices.Then,the waveguide structure is designed,which is a Y-branch portion,a periodically-polarized lithium niobate portion and a 3dB coupler portion,which can realize the generation of an on-chip light source and the separation of photon pairs.Based on the effective refractive index method,the single-mode conditions of the ridge waveguide propagation are determined.The structural parameters and effective refractive index of the ridge waveguide are determined,and the polarization period of the periodically-polarized lithium niobate is determined.The characteristics of two-photon are analyzed by two-photon joint spectroscopy theory.The bandwidth of the pump light and the influence of the length of the PPLN waveguide on the two-photon characteristics are compared to determine the proper pumping light and the length of the polarization periodic waveguide.At the same time,the propagation of the light field in the waveguide is simulated by the beam propagation method,and the Y-branch and 3dB coupler are designed and simulated to determine the design parameters of the two devices.The SPDC source designed in this paper has high quantum interference visibility,and the designed 3 dB coupler can separate photon pairs.Finally,the experimental optical path is set up,and the experimental measurement of the periodic polarization lithium niobate waveguide initial sample and the 3 dB coupler waveguide initial sample is carried out.This experiment is the preliminary preparation for testing the integrated waveguide in the future.Through experiments,the phase matching wavelength of the type I spontaneous parametric down-conversion ridged waveguide is 783.23 nm,and the CAR of the photon pair generated by the sample waveguide reaches the maximum at the pump power of 351 ?W,which is 48.97.At this time,the photon pair is generated.The efficiency is pair/pump photon.It has a higher photon pair generation efficiency.For the 3 dB coupler,the reflectivity of the TE and TM modes is 51.4%,52.7%,close to 50:50,and the probability that the photon pair is separated from the A and B ports of the beam splitter is 0.998318.The optical waveguide designed in this paper can provide guidance and reference for future experiments.