Interference fringes controlled by noninterfering photons

Interference phenomena play a fundamental role in physics, and interferometric techniques have helped advance science and technology significantly. In this Letter, we observe spatial fringes in the interference of two beams, which are controlled by a third beam through the phenomenon of induced coherence without induced emission. We show that the interference pattern depends on the alignment of this third beam in an analogous way, as fringes created in a traditional division of amplitude interferometer depend on the relative alignment of the two interfering beams. We demonstrate that the pattern is characterized by an equivalent wavelength, which corresponds to a combination of the wavelengths of the involved light beams. Our results open up the possibility of developing new techniques, such as wavefront sensing and holography at wavelengths for which no suitable single-photon cameras are available. (C) 2017 Optical Society of America