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Laser Modeling

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Definition: the investigation of phenomena and quantitative relations in lasers, using theoretical models and computational methods

German: Modellierung von Lasern

Categories: lasers, methods, physical foundations

How to cite the article; suggest additional literature

The operation of lasers involves a complicated interplay of many effects, which can affect a variety of important performance parameters. In many cases, it can be vital to obtain a decent understanding of how various effects interact. As it can be very difficult to obtain experimental access to certain key parameters, and a good understanding can be badly needed even before constructing the first prototype, there is often a need to set up a laser model which allows the calculation and testing of certain aspects of the workings of a laser. The activity of constructing models is called modeling (British spelling: modelling). This term may include the process of applying a model.

What a Model is

A model is essentially a mental object which is constructed so that it resembles in some ways the properties of a class of real objects.

Some important aspects of models are the following:

Different models may be used for investigating different aspects of a single laser. As far as possible, such aspects should be separated: a model containing all such aspects, enabling multi-physics simulations, would be complex and difficult to handle, and is needed only where different physical effects interact in an essential way. Figure 1 illustrates how different models can treat the relations between different aspects in a solid-state laser system.

laser modeling

Figure 1: Examples of physical aspects which different laser models can cover.

In any case, the purpose of a laser model should be to serve as a tool to enhance the physical understanding of some aspects of certain lasers (see below).

Uses and Benefits of Laser Models

Laser models can be used to investigate a wide range of aspects. Some examples are:

Possible benefits of laser modeling include:

The main benefits are probably saving a lot of time in the laboratory gaining a deeper insight into the relevant physical mechanisms. The magnitude of such benefits, however, depends strongly on the circumstances. Whereas in some cases (e.g. ultrafast fiber lasers) a laser model may be the essential tool for understanding the principle of operation and the limitations, many other laser devices can be designed on the basis of simpler design rules, which make a sophisticated model obsolete.

Software for Laser Modeling

Laser modeling is very often done with some software, which can perform the required calculations and display or store the results. Software may also help with the construction of a model, with the organization of the data, or with convenient visualizations.

Three-dimensional problems often occur in optics; examples are beam propagation and temperature profiles. Finite-element algorithms are often employed in such situations, but there are also techniques to reduce the effective dimensionality of a model so as to simplify the solution greatly without losing important aspects. For example, the fact can be exploited that many lasers exhibit a close to Gaussian laser beam, so that the laser output calculations can be greatly simplified by assuming the Gaussian profile (with parameters from the analysis of resonator modes) while still properly treating the transverse dependencies of optical intensities and the laser gain. This can speed up the calculations enormously, cut down the usage of memory, and simplify the visualization and further analysis. A similar case in nonlinear optics is the use of mode coupling techniques.

Apart from the numerical core, doing the actual calculations, the quality of the user interface is essential. There are different types of user interfaces, which can be more or less appropriate under different circumstances:

If commercial software with the required features is not available, custom software may be developed. This, however, requires a lot of experience to be efficient, and the poor user interfaces of self-made software often create serious problems. For example, it is difficult to maintain software which requires different versions of source code for different versions of a model and the risk of handling errors can also be very high.

Failing Modeling Exercises

Although laser models can bring extremely valuable benefits, modeling exercises can also fail to produce valid and useful results. Possible causes for such failure include:

A Strategy for Successful Modeling

It is very advisable to use a systematic strategy for modeling. This can be based on, e.g., the following steps:

Curiously, the last step, which should be the most important one, is often forgotten: there are plenty of research papers reporting the construction and perhaps validation of some model, whereas it is not apparent that the model has been used to do some work.


The RP Photonics Buyer's Guide contains 7 suppliers for laser modeling services and software. Among them:


[1]How to Build a Transparent Laser – thoughts about a fundamental problem of laser development and a powerful solution (can also view this as a video)
[2]R. Paschotta, tutorial on "Modeling of Fiber Amplifiers and Lasers"

(Suggest additional literature!)

See also: lasers, laser resonators, rate equation modeling, laser dynamics, pulse propagation modeling, Spotlight article 2006-11-16, Spotlight article 2007-02-26, Spotlight article 2008-11-08
and other articles in the categories lasers, methods, physical foundations

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