Study On The Key Technology Of All-fiber Two-Photon Entanglement Source

Two-photon entangled source,as one of the core techniques of quantum communication systems,has caused a wide study of the academia.The current experiments show that the optical parameter process is an effective way to generate entangled photons,including the process of four-wave mixing which is based on the third-order nonlinear polarization effect of optical fibers and the spontaneous parametric down conversion which is based on nonlinearly polarized crystals.The entangled photons generated by spontaneous parametric down conversion are difficult to be coupled into the optical fiber with high efficiency,and the experimental device is troublesome,and the overall device is difficult to achieve integration and miniaturization.In this paper,four-wave mixing in an optical fiber is used to generate entangled photons.The key techniques studied include theoretical analysis and experimental research of pump sources,theoretical analysis and experimental research on the process of four-wave mixing in optical fibers,and the correlation characteristics and detection principle of photon pairs.The specific research content is as follows:1.The generation of correlated photons is achieved by using a four-wave mixing technique based on an optical fiber,highly nonlinear fibers and dispersion-shifted fibers are respectively pumped by a self-built pump source,and a four-wave mixing process occurs to generate correlated photons.2.A theoretical model of pulsed pump source is established,the basic structure of the passive mode-locked laser is discussed,the transmission characteristics in the optical fiber are analyzed in detail,the model of the passive mode-locked laser is simulated and analyzed,an NPR mode-locked laser with center wavelength of 1571 nm,half-wave bandwidth of 7.2 nm and frequency of 17.556 MHz is built.3.The dispersion effect and nonlinear effect in the fiber are analyzed,the classical theory of the four-wave mixing process in the fiber is discussed,a simulation model is established based on the four-wave mixing parameter gain and the influence of the relevant factors on the parameter gain is clarified,an experimental structure of a double-pumped source is constructed,the high-nonlinear fiber and dispersion-shifted fiber are pumped to obtain the four-wave mixing phenomenon,and correlated photons are generated.4.The four-wave mixing quantum theory basis is discussed,the two-photon state vector expression is obtained,the detection principle of the entangled photon pairs is clarified,the quality evaluation criteria of the entanglement source are established,the influence of self-phase modulation and spontaneous Raman scattering on the purity of the pump pulse is analyzed.