Encyclopedia … combined with a great Buyer's Guide!

VLib
Virtual
Library
Sponsoring this encyclopedia:     and others

Laser Models - not Always Useful

Posted on 2006-11-16 as a part of the Photonics Spotlight (available as e-mail newsletter!)

Permanent link: https://www.rp-photonics.com/spotlight_2006_11_16.html

Author: , RP Photonics Consulting GmbH

Abstract: The article encourages some amount of healthy skepticism against many efforts of laser modeling, while also pointing out substantial benefits. To realize those at a reasonable cost, one needs to take a number of systematic steps.

Dr. Rüdiger Paschotta

Ref.: encyclopedia article on laser modeling; web page on modeling of optical devices and systems

There are many scientific papers reporting some kind of analytical or numerical model of a laser device (or a fiber amplifier, parametric oscillator, etc.). A lot of equations are presented, the model is explained, some numbers (sometimes of unclear origin – fitted values? fudge factors?) are plugged in, and in the end there are some graphs demonstrating “excellent agreement of the model with the measured laser performance”. The latter often appears to be considered as the final goal. Very frequently, however, there could hardly be a favorable answer to the question: What have we actually learned from the model? This may be a nasty question, but it is obviously essential.

While a critical look at each proposed model is certainly advisable, one should not generally dismiss the possibility that an analytical or numerical model can be very useful. Imagine how much faster and cheaper a model can be for testing certain assumptions or ideas, compared with experimental tests. With a model one can also often do such things in a more reliable way, as it makes it easy to modify one parameter without affecting several others, and gives insight into parameters which can hardly be measured. And there is often hardly a better way to obtain a deep understanding of the workings of a device than “experimenting” with a good model.

In order to really get the potentially great benefits at a reasonable cost, a number of steps have to be taken. One should always begin by formulating a set of concrete questions which one hopes to clarify. (For example: Is it possible that effect X is responsible for observation Y? Will measure Z cure the problem? At which power level will effects L limit the performance?) Second, one needs to judge whether there is a kind of model which has a chance to reliably answer these questions, and what the estimated effort of realization is. Third, the model has to be put together, possibly including a numerical realization on the computer. Fourth, certain tests are required for validation of the model. Finally, the model can be applied to answer the original questions, to improve the general understanding e.g. of limiting effects, etc. Having this procedure in mind, one easily understands (a) that many modeling attempts fail because some of the described steps are not (or not properly) carried out, and (b) that it takes a fair amount of experience to efficiently do such a job; it is usually not an issue for Friday afternoon.


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 RP Photonics Encyclopedia.

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

preview

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

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