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The Photonics Spotlight

Papers Reporting Yet Another Laser Crystal

Dr. Rüdiger Paschotta

Ref.: encyclopedia articles on laser crystals, gain media, solid-state lasers

Over the years, we have seen thousands of journal papers and conference talks presenting novel laser crystals, corresponding spectroscopic data and first demonstrations of laser action, mode locking, etc. The repetitive style of such reports can be tiring. So one may ask, do we really want all such papers?

My answer to this admittedly somewhat provocative question is: no, we don't like many of them, in fact would do better without them, but also we wouldn't like to miss quite a few of those papers.

Leaving aside questions of style, technical quality and alike for a moment, we should realize that even though a huge variety of laser crystals is known, this certainly doesn't mean that we don't need any new ones. Well, for some kinds of solid-state lasers, e.g. low or medium power continuous-wave lasers, existing gain media such as YAG or Nd:YVO4 could hardly be much better in terms of performance. For example, their gain efficiency could not be significantly better for a given gain bandwidth, because spontaneous emission sets fundamental limits. However, accessible laser wavelengths will remain a topic of interest for many years. Furthermore, there are kinds of lasers where available crystal materials do leave a lot of room for further wishes. In particular, what is available for the generation of ultrashort pulses with passive mode locking is still in some respects far from what would be convenient and physically possible. For example, a better compromise between a large gain bandwidth and high thermal conductivity, combined with large laser cross sections and a smooth shape of the gain spectrum, should be physically possible, even though we know e.g. that some factors which lead to a large gain bandwidth often tend to reduce the thermal conductivity. So a further search for better crystal materials may indeed bring great benefits for the performance of such lasers.

The quality of papers is a different matter, however. Indeed, experts (including referees) are tired of being flooded with papers of doubtful quality. In the context of laser crystals, the following problems are frequently encountered:

But again, we do need better crystals, and good papers on such developments should be warmly welcome! To be constructive, here are some suggestions for authoring such papers:

Of course, it is not all about authoring; first comes the hard work … But remember that a good paper will have the chance to be cited quite frequently, and will rightly earn more reputation.

By the way, you may suggest really good laser crystal papers (and of course papers on many other topics) for being cited in the Encyclopedia of Laser Physics and Technology.

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

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