Parametric Fluorescence | <<< | >>> | Feedback |
Definition: light emitted by a parametric amplifier without signal or input inputs
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 occurs essentially only in directions where phase matching occurs. Therefore, it normally carries only a small optical power. 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: optical parametric amplifiers, optical parametric oscillators, optical parametric generators, quantum noise
