Complete measurement of single-photon and two-photon joint spectral properties of entangled photon pairs generated via type-I spontaneous parametric down-conversion under different phase- matching conditions are reported. A theoretical model is also developed to explain the observed two- photon joint spectra.
We report the complete measurement of the spectral properties of entangled photon pairs generated via frequency-degenerate type-I spontaneous parametric down-conversion pumped by a cw laser in both the collinear and the noncollinear regimes. The measurement includes the single-photon spectra as well as the two-photon joint spectra. Our results reveal interesting yet subtle differences between the collinear and the noncollinear regimes of frequency-degenerate type-I spontaneous parametric down-conversion. The single-photon and two-photon spectral measurements are in good agreement with the numerical simulation taking into account the tuning curve and the experimental geometry.
Spectral properties of entangled photons generated via type-I frequency-nondegenerate spontaneous parametric down-conversion are studied theoretically and experimentally. For monochromatic pumping, the joint spectral intensity function for the photon pair is found to be symmetric even though each photon has a different central wavelength. The single-photon (first-order) interference shows the familiar triangular interferogram, usually associated with the cw-pumped frequency-degenerate type-II spontaneous parametric down-conversion. For broadband (ultrafast) pumping, on the other hand, the joint spectral intensity function is shown to be asymmetric, similar to the case of ultrafast-pumped frequency-degenerate type-II spontaneous parametric down-conversion. The spectral studies reported here are expected to play an important role in developing ultrabright two-color entangled photon sources.