Based on the signal and idler photon pairs produced in a piece of high nonlinear fiber by a pulsed pump, we characterize the heralded single photon source from both the theoretical and experimental aspects. In the theory model, started from the derived expression of Bogoliubov transformation for a broadband pulsed pump, the second-order intensity correlation function
gc(2)(0), heralding efficiency
H, indistinguishability and brightness of the heralded single photons as a function of source parameters are analyzed and discussed. In the experiments, using several kinds of combinations of the source parameters, the values of
gc(2)(0) and
H are measured and compared. The experimental results are consistent with the theoretical predictions. The investigations are useful for optimizing the parameters and for developing a single photon source suitable for quantum information processing.
In this paper, the noise performances of 1.5 microm correlated photon pair generation based on spontaneous four wave-mixing in three types of fibers, i.e., dispersion shifted fiber, traditional highly nonlinear fiber and highly nonlinear microstructure fiber are investigated experimentally. Result of the comparison shows that highly nonlinear microstructure fiber has the lowest Raman noise photon generation rate among the three types of fibers while correlated photon pair generation rate is the same. Theoretical analysis indicates that the noise performance is determined by the nonlinear index and Raman response of the material in fiber core. The Raman response rises with increasing doping level, while, for the nonlinear index, the impact of doping level is weak. As a result, highly nonlinear microstructure fiber with pure silica core has the best noise performance and great potential in practical sources of correlated photon pairs and heralded single photons.
Based on the theory of third-order nonlinear Kerr effect in optical fiber, we experimentally demonstrate the generation of photon pairs by exploiting spontaneous four-wave mixing. The photon pairs are produced by pumping a fiber Sagnac loop and a piece of straight fiber with a pulsed laser, respectively. By comparing the experimental results, we analyze how to optimize the experimental parameters to obtain entangled photon pairs with high purity. Our results are useful for developing the all-fiber source of photon pairs and single photon source, which are well suited for quantum communication.