New interference gratings developed in Jena
Jena physicists developed the prototype of an interference grating made of dielectric thin-film systems in a Thuringian joint project. Interference gratings filter out defined wavelength ranges from light beams and are among the standard components of lasers and optical measuring instruments. The dielectric grids are significantly better performing and longer lasting than traditional metal film coated glasses. The Jena prototype was created as a standard solution in cooperation with physicists from the Friedrich Schiller University Jena, the Fraunhofer Institute for Applied Optics and Precision Engineering and the Mellinger company Layertec; The Thuringian Ministry of Science is funding the two-year project with a total of 650.000 marks. A high-tech variant for extreme lasers is now to be developed in an international project. The European Union has provided around two million marks for this.
For the new type of interference grating, the Jena scientists use a combination of tantalum pentoxide (Ta2O5) and silicon dioxide (SiO2) layers that are only 100 billionths of a meter thick, which are vapour-deposited onto a substrate under vacuum conditions. In a second step, a grid structure is 'scratched' into these layers using electron beam lithography, which filters out the desired wave ranges through light diffraction. The reflectivity of the new coating is 99.9999 percent and is significantly higher than conventional aluminum or silver interference gratings.
&132;This enables us to achieve a very high damage threshold of 10-20 joules per square centimeter&147;, explains the Jena laser physicist Prof. Dr. Roland Sauerbrey. The result is higher efficiency, less wear and tear and therefore lower costs in industrial applications. But we will also open the door to a new dimension for high-power laser technology, he predicts.
Because while the Thuringian project aims to bring interference gratings with just one Ta2O5/SiO2 combination layer to series production, the researchers in the EU-wide network want to try out the combination of several superimposed layer systems. If this succeeds, lasers could be built with even more intense light pulses that significantly exceed the current terawatt range (trillions of watts). In the project, which will start this year, the University of Jena is collaborating with the renowned Rutherford Appleton Laboratories (RAL) in England, several French partners and Zeiss Oberkochen.