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Parametric Fluorescence

Definition: emission of light by a parametric amplifier without signal or input inputs

German: parametrische Fluoreszenz

Categories: nonlinear optics, quantum optics


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An optical parametric amplifier emits some light even if there is no signal and idler input. This phenomenon is called parametric fluorescence. It is a quantum effect. In a semiclassical model, it can be attributed to vacuum fluctuations (vacuum noise) of the optical field which enters the open input port(s) of the device. In the case of a non-degenerate parametric amplifier, vacuum noise in the signal and idler ports have similar effects.

Parametric fluorescence is similar to the spontaneous emission in a laser amplifier, but is based on parametric amplification, and it occurs essentially only in directions where phase matching occurs. Therefore, it normally carries only a small optical power, except in some cases with intense pulsed pumping and correspondingly large parametric gain. There may, however, also be some off-axis parametric fluorescence which is non-collinearly phase-matched. The center wavelength will then depend on the propagation direction.

Parametric fluorescence can be useful for the alignment of a non-collinear parametric amplifier, since it shows the direction where phase matching and thus the maximum parametric gain occurs.

See also: superfluorescence, optical parametric amplifiers, optical parametric oscillators, optical parametric generators, quantum noise

Questions and Comments from Users


What is parametric superfluorescence? This term is used in the user's manual of my NOPA (TOPAS-White) and is used in the context of the ring of light surrounding pump beam after the nonlinear crystal. Is this different from parametric fluorescence?

The author's answer:

I think that the term (which is also occasionally found in the literature) is somewhat inappropriate, since superfluorescence is normally understood to be a quantum-optical phenomenon of collective emission, which is not that closely related to what happens in these optical parametric amplifiers. Presumably, “super” has been added in order to emphasize that the parametric fluorescence is getting stronger due to parametric amplification – just like luminescence becomes superluminescence.

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