Investigation of the role of indistinguishability in photon bunching and stimulated emission

Photon bunching effect and stimulated emission of single photons is investigated and observed in the parametric amplification process. It is found that the two-photon interference is responsible for the photon bunching effect and stimulated emission, which is discussed in the temporal degree of freedom and in the presence of photon losses. Moreover, the direct measurement of the indistinguishability of two signal photons without any filtering is accomplished via the correlation between the two idler photons from two cascaded parametric down-conversion processes. This result shows that photon indistinguishability plays an essential role in stimulated emission.