The Italian partner Optomaterials produces competitive crystals, which the Lithuanian company Altechna provides with a special coating. To achieve the necessary properties for space-applications, Altechna has developed special coating designs and processes based on ion beam and magnetron sputtering processes.
Proven: Space suitability
Scientists at the LZH thoroughly tested the crystals in special laser systems. They have designed these systems with future applications in mind. The demonstrators could lay the foundation for new laser-based measuring instruments.
The LZH’s scientists exposed the Alexandrite crystals to proton and gamma radiation and ran them through several temperature cycles typical for space applications. Before and after these environmental tests, they have characterized the crystals in terms of their transmission properties and laser performance, among other things. Since the environmental tests did not significantly change the measured parameters, the space suitability could be demonstrated. In addition, the researchers showed that the laser-induced damage threshold (LIDT) of the crystals is equal to – or even exceeds – top products on the world market.
Crystals now ready for the market: GALACTIC has reached TRL 6
The GALACTIC team has thus successfully raised the Technology Readiness Level (TRL) of space-qualified alexandrite crystals from Europe from 4 to 6 and have made the crystals ready for the market.
Special properties for more precise data
Alexandrite crystals have very good thermal conductivity and fracture strength. Therefore, they are suitable for use in high power laser systems and are robust enough to withstand the harsh conditions in space. Since the crystals can be used to tune the output wavelength of laser systems, they could form the basis of new types of laser-based measuring instruments for Earth observation satellites. Such instruments could be used to collect more precise climate-relevant data on the state of the atmosphere or vegetation.
In the project "High Performance Alexandrite Crystals and Coatings for High Power Space Applications" (GALACTIC), the Laser Zentrum Hannover e.V. together with Altechna and Optomaterials S.r.l. have established an independent, purely European supply chain for alexandrite laser crystals. GALACTIC was funded by the research and innovation program "Horizon 2020" of the European Union under funding code No. 870427. GALACTIC was coordinated by the LZH.
Recent publication of GALACTIC’s results:
S. Unland, R. Kalms, P. Wessels, D. Kracht, and J. Neumann, "High-performance cavity-dumped Q-switched Alexandrite laser CW diode-pumped in double-pass configuration," Opt. Express 31, 1112-1124 (2023) https://doi.org/10.1364/OE.478628
L. Lukoševičius, J. Butkus, P. Weßels, S. Unland, R. Kalms, T. Böntgen, H. Mädebach, M. Hunnekuhl, D. Kracht, J. Neumann, M. Lorrai, P. G. Lorrai, and M. Hmidat, "Investigation of advanced optical coating influence on the properties of Alexandrite laser crystals," in Optical Interference Coatings Conference (OIC) 2022, R. Sargent and A. Sytchkova, eds., Technical Digest Series (Optica Publishing Group, 2022), paper TEA.2. https://opg.optica.org/abstract.cfm?URI=OIC-2022-TEA.2
More information about GALACTIC and further publications are available at h2020-galactic.eu.