Two-Photon Interference with the Type II Spontaneous Parametric Down-Conversion

The two-photon polarized entangled state is generated from the type II spontaneous parametric down-conversion pumped by a femtosecond pulse. The two-photon interference is observed in the Hong-Ou-Mandel interferometer. The high visibility of the interference is restored with narrow band interference filters placed in front of the detectors.