Fig. 1. Experimental setup. The area framed by the dashed line is the heralded single photon source, while the area framed by the dotted line is the measurement system for characterizing the source. G, diffraction grating; SMF, single mode fiber; DM, dichroic mirror; M, mirror; Fs, long-pass filters of signal photons; Fi, bandpass filters of idler photons; CWDM, coarse wavelength division multiplexer; SPD, single photon detector; BS, 50/50 beam splitter.

Fig. 2. (a), (b) Measured single channel counting rates in the heralding and heralded channels Nt and Ns, as a function of average pump power Pa. The solid curves in (a) and (b) are the fitting polynomial with the dashed and dot-dashed lines, respectively, representing the linear and quadratic terms. (c) Two-fold coincidence and accidental coincidence counting rates N12 and Nac. (d) Coincidence-to-accidental ratio (CAR) as a function of Pa. The solid and hollow symbols denote results with and without subtracting the dark counts of SPDs. In (a), (b), and (c), the dark counts of SPDs are subtracted.

Fig. 3. (a) Measured counting rate of true coincidence Nc. (b) Measured three-fold coincidence N123. (c) Measured second-order correlation function g(2)(0).