Fig. 3
From: Complementarity in single photon interference – the role of the mode function and vacuum fields
Three light patterns photographed with the EMCCD-camera behind the single signal photon Mach-Zehnder interferometer for illustration of the decrease of coherence while tilting one of the two measured TEM00 signal modes. Perfect alignment (left), with a slight horizontal angle between the beams (middle). Tilt of one of the beams results in a loss of fringe contrast and visibility (right)