RP Photonics

Encyclopedia … combined with a great Buyer's Guide!

VLib
Virtual
Library

The Photonics Spotlight

Resolution of Conundrum: Threshold Power for Parametric Nonlinear Interactions

Posted on 2006-09-03 as a part of the Photonics Spotlight (available as e-mail newsletter!)

Permanent link: https://www.rp-photonics.com/spotlight_2006_09_03.html

Author: Dr. Rüdiger Paschotta, RP Photonics Consulting GmbH

Abstract: This article presents the resolution to a physics conundrum in the area of nonlinear optics. Essentially the question was why parametric oscillation involves a threshold pump power, while frequency doubling does not, even though both processes appear to be time-reversed versions of each other. A closer inspection shows that time reversal of frequency doubling in fact leads to a an OPO with an subharmonic input wave.

Dr. Rüdiger Paschotta

Ref.: encyclopedia articles on parametric amplification, optical parametric oscillators, frequency doubling, etc.

On 2006-07-30, the Photonics Spotlight presented a physics conundrum: the question was essentially why parametric oscillation involves a threshold pump power, while frequency doubling does not, even though both processes appear to be time-reversed versions of each other.

The resolution of this issue is found through a closer inspection of what time reversal really leads to. Consider a resonant frequency doubler operated at a rather low pump power level. It will generate some second-harmonic light, but leaves much of the pump light unconverted. Now imagine the time-reserved situation. This looks like a degenerate optical parametric oscillator (OPO), converting some higher-frequency pump light into lower-frequency light. It is essential not to overlook that the unconverted pump light leaving the frequency doubler now appears as subharmonic light which forms a second input of the OPO. Only with this additional subharmonic input, the OPO can convert light power at arbitrarily low power levels. If you omit this input, you don't have a time-reversed situation of a frequency doubler any more, and therefore it is not surprising that there is then a threshold power involved.

This article is a posting of the Photonics Spotlight, authored by Dr. Rüdiger Paschotta. You may link to this page and cite it, because its location is permanent. See also the Encyclopedia of Laser Physics and Technology.

Note that you can also receive the articles in the form of a newsletter or with an RSS feed.

How do you rate this article?

Click here to send us your feedback!

Your general impression: don't know poor satisfactory good excellent
Technical quality: don't know poor satisfactory good excellent
Usefulness: don't know poor satisfactory good excellent
Readability: don't know poor satisfactory good excellent
Comments:

Found any errors? Suggestions for improvements? Do you know a better web page on this topic?

Spam protection: (enter the value of 5 + 8 in this field!)

If you want a response, you may leave your e-mail address in the comments field, or directly send an e-mail.

If you enter any personal data, this implies that you agree with storing it; we will use it only for the purpose of improving our website and possibly giving you a response; see also our declaration of data privacy.

If you like our website, you may also want to get our newsletters!

If you like this article, share it with your friends and colleagues, e.g. via social media:

arrow