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Although lasers based on diamond have been around around for several years, they have never been very powerful. That’s beginning to change now as new CVD fabrication methods provide larger, and purer, diamonds. Researchers from the Fraunhofer Institute for Applied Optics in Germany, and the MQ Photonics Research Centre in Australia, have just built a diamond laser with 20 times more power than anything yet to date.

The ability to slice through steel has always been the benchmark for cutting power. With 380 Watts @ 1240nm, the new laser has enough oomph to handle the job. While lesser lasers have made similar claims, without the actual watts behind them no amount of focussing or pulse compression can make the task worthwhile. In other words, if your depth of focus is so tight that the sweet spot for cutting is barely thicker than a foil, and you need to ‘Q-switch’ your laser to compress the all the power into impossibly brief pulses just to make a mark, you are likely wasting your time.

More typical workhorse solid state lasers, like Yb-doped disk and fiber lasers, can routinely deliver kilowatt range power. However, they are ultimately limited by their relatively narrow wavelength coverage and inability to handle the extreme thermal loads that are part-and-parcel of higher power. Diamond optics can not only handle the heat, but can also transfer it away from the hot zone faster that just about anything else.

The new diamond lasers make use of something known as Raman conversion to shift light to wavelengths that are long enough to be efficiently absorbed by steel. If the photons merely pass through, or get reflected, they won’t deposit enough energy for cutting. In doped glass fibers, the ‘Raman gain’ is usually limited by line broadening effects. An extremely tight line would be required at the input stage to the frequency conversion stage to get any significant power out. Furthermore, the wavelength range of these fibers is restricted to the transparency of silica.

The release stories for this laser mention that the infrared wavelengths used here are safer for the eye than either visible or UV radiation. While that may be generally true, anything that has significant amounts of water is a potential absorber of IR energy across a fairly wide band. It also appears to be fashionable to compare output power of cutting lasers to laser pointers, with many noting that the new diamond laser is equal to “400,000 laser pointers.” In light of the ample variance in both wavelength and power of pointer devices, those kinds of comparisons should probably be taken as rough.

Diamond lasers can potentially unleash more than just new cutting or machining technologies. Since silicon doesn’t reflect x-rays, imaging applications based on x-ray lasers have traditionally been severely limited. Diamond-based x-ray lasers, on the other hand, would be a whole new ball game. CVD diamond still has its costs, but they are rapidly falling while output quality is rising. It would seem that these trends should soon make off-the-shelf diamond lasers fairly commonplace.