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ET-MEROPE develops technology to combat thermal distortions in laser beams Einstein Telescope

In the field of Thermal Deformations technology, seven Dutch companies and knowledge institutions are collaborating in the ET-MEROPE consortium on innovative techniques to effectively measure and correct deviations in the laser beams of the future Einstein Telescope. This technology is crucial to the functioning of Europe's most advanced observatory for gravitational waves.

The Einstein Telescope detects gravitational waves—subtle ripples in space-time caused by, for example, colliding black holes—by using lasers to measure extremely small changes in the length of detector arms. This requires mirrors that are aligned as perfectly as possible. However, even small temperature changes can cause thermal distortions in these mirrors, distorting the laser beam and reducing measurement accuracy.

ET-MEROPE Consortium

The ET-MEROPE consortium, coordinated by TNO and with partners Sioux Technologies, ATG Engineering, Hoursec, NOVA, Nikhef, and DEMCON, is pooling expertise to tackle this challenge. They are developing a set of advanced techniques to actively compensate for thermal deformations in the optical systems of the Einstein Telescope.

"Corrective optics can help telescopes see through the turbulent atmosphere and study planets around stars other than the sun. Another application is secure and fast laser communication between satellites and stations on Earth," says Wouter Jonker of TNO.

“These are minute deviations, but for the precision we want to achieve with the Einstein Telescope, every picometer (millionth of a micrometer) is one too many,” says program manager Wouter Jonker of TNO, the consortium's coordinator. The consortium is therefore working on a mirror with deformable elements. This will be added to the light path of the Einstein Telescope and controlled in such a way that its own deformation compensates for the thermal deformations of other mirrors.

For their prototype, the partners are developing not only the deformable mirror but also machine learning to deduce from the deformed laser beam which of the hundreds of mirrors is deviating, so that it is clear how best to address the disturbance. They are also developing electronic control for the correction mirror, which generates hardly any heat itself and therefore does not cause any additional thermal deformations.

Spin-off potential — telescopes and laser communication

According to Wouter Jonker, the new knowledge and expertise gained by the consortium is of great importance to other markets. For example, corrective optics can help telescopes see through the turbulent atmosphere and study planets around stars other than the sun. Another application is secure and fast laser communication between satellites and stations on Earth.

The technology developed in this project falls under the Einstein Telescope for Business program, an initiative of the National Growth Fund to encourage Dutch high-tech companies to develop technologies for the Einstein Telescope. ROM LIOF is coordinating this program nationally on behalf of the Ministry of Economic Affairs (EZ), the Ministry of Education, Culture and Science (OCW), and Nikhef, with support from regional partners such as BOM, InnovationQuarter, and Oost NL.

The Einstein Telescope itself is still in preparation. The Netherlands is working with Belgium and Germany on a location in the border region. In 2026 or 2027, it will become clear where the observatory will be built.