24 March 2018 
18 September 2017

Cool by diamond – New generation of semiconductor lasers

Lasers became popular with movies like „Star Wars“ or „James Bond“. In reality, lasers are incredibly versatile applicable tools – they are used, e.g., for cutting and welding of a variety of materials. Physicists of the University of Stuttgart succeeded with a technological breakthrough.

Photo: Hermann KahlePhoto: Hermann Kahle
This will extend the choice of by semiconductor lasers accessible wavelengths and facilitate new applications. How can semiconductor disk lasers further be improved in terms of output power without losing their other wonderful properties? Scientists from the “Institut für Halb­leiteroptik und Funktionelle Grenz­flächen” examined this issue. The key solution sounds simple and is consequent though challenging as it is in most cases when going into practice.

Semiconductors themselves are poor thermal conductors. So one has just to omit all parts of the semiconductor structure not essentially necessary to build up a whole laser: the substrate on which the semiconductor layers are deposited has no function during laser operation and can be removed. External mirrors can replace the semiconductor mirror, integrated in all semiconductor disk lasers.

The only thing left of the semiconductor component is the several few hundreds of nanometers thick laser active region which gets sandwiched between two diamond disks. Diamond – transparent and the best thermal conductor available – is suitable in an outstanding way as an integrated heat spreader. The PhD-Students Hermann Kahle and Cherry May Mateo started with wet-chemical etching processes to isolate the laser active region from its substrate. The semiconductor membrane, in total thickness only one eightieth of the diameter of a regular human hair, can be stored and best handled when submerged in a liquid only.

The exciting thing at the end was to transfer the membrane onto a diamond disk which is four millimeter in diameter and 0.5 millimeter in thickness. Likewise, it has to keep in one piece, centered to the diamond and totally flat. And, there was never a second chance. Once bonded to the diamond by capillary forces it was impossible to remove the membrane again without destroying it. Laboratory work like this requires calm hands, lots of skill and endurance. The completed diamond-semiconductor-sandwich was then inserted into a laser resonator and characterized in the optics laboratory. After hours of adjustment work it flashed and the membrane laser was operating. A strong light beam in the red spectral range was emitted after a little more fine adjustment. And, it showed all characteristics we had hoped for: the tunability of the laser wavelength during operation, a perfectly shaped beam profile and especially a for semiconductor lasers high output power; and all this at an operating temperature of 10°C. Without the diamond sandwich the semiconductor membrane would rapidly overheat and stop to operate. Before this approach the whole semiconductor disk laser device sometimes had to be cooled down to minus 30°C.


More news about "Schweissen & Schneiden":

20 September 2017

Who’s the best robot operator?

Entitled "Robot Welding Contest", the German Welding Society (DVS) will continue its contest for the best weld with the aid of a robot at Schweissen & Schneiden (25-29 September in Düsseldorf). The international competition will take place in Hall 13. (more…)

20 April 2016

Five clearly structured areas

For Schweissen & Schneiden 2017, Messe Essen's team has reorganised the halls in an intelligible way according to thematically appropriate main focal points. (more…)


25/03/2018 - 28/03/2018 in Brüssel
The biggest Benelux Trade Fair for Automotive Professionals
26/03/2018 - 28/03/2018 in Shanghai
China's leading event dedicated to coil winding, insulation and electrical manufacturing
26/03/2018 - 29/03/2018 in Shanghai
Hotelex Equipment & Foodservice Expo
Trade platform of hotel supplies in China
26/03/2018 - 29/03/2018 in Almaty
Homedeco Kazakhstan
Exhibition for Home Textile for Drapery, Upholstery, Furniture, Decoration - Accessories Fair
26/03/2018 - 29/03/2018 in Dubai
A&D City, Accessoires & Homeware, Cabinets, Closets & Storage, Furniture & Furnishings, Lighting & Technology, Sleep & Textiles
27/03/2018 - 29/03/2018 in Moskau
Stylish Home Objects & Tableware
International specialized exhibition - Stylish Home. Objects & Tableware


Next date of the fair Schweissen & Schneiden: 13/09/2021 - 17/09/2021

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