Spatiotemporal Coherence and Interference Properties of Spontaneous Parametric Downconverted Twin Photons.

Bahaa E. A. Saleh, Adel Joobeur

А. А. Малыгин, Alexander N. Penin, Alexander V. Sergienko

X. Y. Zou, L. J. Wang, L. Mandeļ

Although induced coherence is generally associated with induced or stimulated emission, in the process of spontaneous parametric downconversion of light induced coherence can be generated on its own. This is demonstrated in an experiment in which the signal beams from two coherently pumped downconverters come together and interfere whenever the idler beam from the first downconverter (DC1) passes through and is aligned with the second downconverter (DC2). Misaligning the idlers, or blocking the first idler, makes the interference disappear. More generally, the degree of coherence can be controlled by varying the amplitude of the idler from DC1 that reaches DC2. The interpretation of this nonclassical interference is discussed in terms of the interpretation of the wave function or state vector of the emitted photon.

Holger Friedrich Hofmann, Takafumi Ono

We show that the interference between photon pairs emitted by spontaneous parametric downconversion and coherent laser light generates a class of N-photon phase squeezed states characterized by a single squeezing parameter given by N times the ratio of the downconversion amplitude and the squared coherent amplitude.

Preston Alexander, Scott Baldwin, S. Blane McCracken +1 more

Stefan Lerch, André Stefanov

We experimentally investigate the properties of light generated by the sequential processes of spontaneous parametric downconversion followed by upconversion. By interfering the upconverted photons with the original pump light, we show that the processes preserve the coherence of the light. Moreover, we observe interferences with doubled phase sensitivity when changing the phase of the downconverted entangled light, although its coherence length is several orders of magnitude shorter than the one of the pump light. Finally the statistics of the upconverted light is expected to be super-poissonian and we experimentally observe superbunching.