Super-resolving interference without intensity-correlation measurement

The high-order intensity correlation function of N-photon interference with thermal light observed in a recent experiment [S. Oppel, T. Buttner, P. Kok, and J. von Zanthier, Phys. Rev. Lett. 109, 233603 (2012)] is analyzed. The terms in the expansion of the Nth-order correlation function are put into three groups. One group contributes a homogeneous background. Both of the other two contribute (N - 1)-fold super-resolving fringes. In principle they correspond to coherent and incoherent superpositions of classical optical fields, respectively. Therefore similar super-resolving fringes can be obtained without intensity-correlation measurements. We report the experimental results of the coherent and incoherent super-resolving diffraction fringes, which are observed directly in the intensity distribution. The N - 1 sources in both the coherent and incoherent cases are set in certain definite positions. In the coherent case, moreover, the phase difference between two adjacent source fields is pi. The fringe visibility is unity in the incoherent case, while it decreases as N increases in the incoherent case.