Theoretical And Experimental Study Of The Generation Of Correlated Photon Pairs From Photonic Crystal Fiber With A Pulsed Pump

Correlated photon pairs from the spontaneous parametric emission in nonlinear media have been a crucial resource for quantum information processing. The high-nonlinear photonic crystal fiber is regarded as an ideal χ(3) nonlinear medium for generating photon pairs, because of its controllable dispersion and endless single-mode propagation. This thesis presents the theoretical and experimental studies of the generation of photon pairs with high purity and specified spectral properties via the spontaneous four wave mixing, which is realized by pumping the photonic crystal fiber with pulse train from a mode-locked laser. The main content of this thesis includes four major parts:1. Generation of photon pairs with high purity and large detuning characteristic. The obtained signal and idler photon pairs have narrowband spectra, and the frequency detuning between the pump and the signal (idler) photons is about75THz. Since the Raman scattering photons are almost eliminated completely, the purity of the photon pairs is enormously improved. When the generation rate of the collected signal photons is0.009per pulse, the ratio between the true coincidence and the accidental coincidence is about102, which is close to the theoretical limit.2. By analyzing the joint spectral function and the second order intensity correlation function g(2), the influences of various factors on the spectral properties of photon pairs are comprehensively studied, and the means of generating frequency de-correlated photon pairs are discussed as well. Based on the theoretical discussions, the frequency approximately de-correlated photon pairs are obtained experimentally. For the situation of applying no narrowband filter, the maximum g(2) of the individual signal photons can be achieved is1.78±0.02.3. Based on the frequency approximately de-correlated photon pairs, a heralded single photon source with low noise and approximate single-mode characteristics is demonstrated. Considering the transmission loss, the heralding efficiency of the source can reach86%. When the generation rate of the heralding (idler) photons is about0.002per pulse, the measured intensity correlation g(2) of the heralded (signal) photons is0.012±0.004, which is suppressed by a factor of more than80relative to the classical Poissonian light limit. 4. The influence of the structural inhomogeneity of the photonic crystal fiber onthe photon pair spectrum is studied. By analyzing a theoretical model, it is revealedthat the coherent superposition of the spectral overlapped photon pairs emerging fromdifferent place of the inhomogeneous fiber will result in a modulated and broadenedphoton pair spectrum. The experimentally measured signal photon spectra areconsistent with the theoretical analysis, showing the photon pair spectra measurementcan be used as a dependable and noninvasive way to test the homogeneity of theoptical fibers.