Laser-induced tempering: targeted heating of surfaces and coatings

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LIMO laser-induced tempering

Today, lasers are considered extremely versatile systems – systems believed to be capable of virtually anything by those outside the field. But now, at Dortmund-based LIMO, there is talk of using a laser source for surface heating which will surely astound even seasoned photonics experts. It involves a special application of the Activation Line 300, the most powerful L3 LIMO Line Laser.

“Imagine that a surface with a functional layer only a few micrometers thin is to be heated to over 1000 degrees C,” says LIMO Thin-Film Activation director engineer Dirk Hauschild. “And think about doing this with a substrate that is already destroyed at 500 degrees C.” But it doesn’t stop there: The layers that are to be optimised are often composed of small particles or molecules that lose their desired properties and structural size just a few seconds after the processing temperature has been reached.

In these instances, there is a demand for fast and targeted heating and cooling. This challenge can be met with the use of an in-line high-temperature process that provides targeted surface heating in a matter of milliseconds. The Activation Line 300 was specifically designed to fill this need. With its high electro-optic energy efficiency of over 40 percent, the most powerful L3 LIMO Line Laser (a CW output of over 13kW with a homogeneous line focus 300mm long) heats even the thinnest functional layers (thicknesses of over 0.1 µm to more than 100 µm) with an intensity of 40kW/sq cm in a few milliseconds – delivering outstanding precision and consistency (beam quality M? < 3 in the processing direction) in the process. Because of the low thermal capacity, the layers also cool down again very quickly.

“The laser energy thus serves to functionalise the layer and, as a result, adds to its value,” says Mr Hauschild. “Thanks to the targeted irradiation using the laser line profile, the user can uniformly temper large surface areas. The Activation Line 300 thus enables customised annealing, crystallisation and sintering processes with fully closed surfaces.”

He says precision tempering of coatings on glass, metal, ceramics, films and even on paper is also possible. “For the production process, the user can also utilise extremely small energy and process windows that would otherwise not be feasible with the use of conventional technologies.”

The precision tempering technology was featured at the Photonics Moscow trade fair in Russia in March and the International Laser Technology Congress in Germany in May.

Photo: The Activation Line 300 Laser System from LIMO can heat and cool functional layers with thicknesses of just a few hundred nanometers, doing so with energy-efficiency and precision and without damaging the substrate below.

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