Talk:Optical parametric amplifier

The article does not clarify the connection between nonlinear optics and parametric amplification, e.g. what type/order of nonlinearity is exploited. Some diagrams would be very helpful to the non-expert. There should be a clearer border between the the physical process and experimental/technical implementations. Nonetheless the article states nice details about what problems can occour in real-world implementations. Dwkdwk 12:51, 6 February 2007 (UTC)[reply]

Which is the "signal" and which is the "idler"?[edit]

The sentence "Light with ordinary and extraordinary polarizations are generated; the ordinary light is called the signal and the extraordinary light is called the idler." is wrong, therefore I have deleted it. --Ahellwig (talk) 18:32, 3 August 2010 (UTC)[reply]

Personally I've heard two definitions:

The lower-frequency one is the "idler" and the higher-frequency one is the "signal".
The one that is an external input is the "signal" and the other is the "idler".

I'm not sure how common/uncommon each of these is. --Steve (talk) 22:04, 29 September 2010 (UTC)[reply]

I agree with Ahellwig that the definitions in terms of polarisation were wrong. The polarisation is simply dictated by the type of phase matching used in amplification. I have only ever heard signal defined as the beam with an external input, as it is this which is being amplified. This is the definition used in the following standard textbooks:

A. Weiner, Ultrafast Optics (Wiley Series in Pure and Applied Optics) (Wiley, 2009), ISBN 0471415391, pp
R. W. Boyd, Nonlinear Optics (2003), 2nd ed., ISBN 0121216829

--MarseHole (talk) 20:41, 18 May 2014 (UTC)[reply]

There is no actual difference between the signal and idler in an SPDC process. They are indistinguishable. The typical convention is just to assign one as the signal and one as the idler arbitrarily. This of course requires that when you solve the conservation of energy and conservation of momentum equations that you find ω_input = ω_signal + ω_idler and E_input = E_signal + E_idler. In the ideal case, the signal and idler will be identical beams with flipped angles. (+/- 3 degrees for 405nm pump in BBO). I'll spend some more time reading up on the most recent descriptions in the literature and make sure what I'm saying matches the hegemony.
- DavidJonBloom (talk) 16:45, 6 April 2021 (UTC)[reply]