Immersed grating Demonstrator Delivered to NOVA-ASTRON

© NOVA Optical Infrared Instrumentation group

The Dutch astronomical community is deeply involved in the instrumentation program for the European Extremely-Large Telescope (ELT). One of its instruments will be METIS, an instrument that will study the universe at "thermal" wavelengths - looking primarily at cooler and heavily embedded objects, like star formation regions, proto-planetary disks, planets, the galactic centre.

One of its key capabilities is high resolution integral field spectroscopy. Due to the criticality of the performance of the disperser in the instrument, an alternative method to disperse the light has been developed in close collaboration with SRON, Philips Innovation Services and TNO.

The advantage of an immersed grating is that the size of the large component (160mmx126mm) is significantly smaller (a factor of 3) than a conventional grating would be. However, the accuracy of its surfaces needs to be better by the same factor of 3. Using lithography techniques, the quality of the component can meet the requirements, and it has now been succesfully integrated. The next steps will be the full characterisation of its performance, which will be done at the NOVA-ASTRON group and at ESTEC in Noordwijk.

The component is transparent for IR-wavelengths, and fully reflective for visible light. The nice colours from the sides of the prism-shaped grating (bottom) are caused by Anti-Reflection and Absorption coatings. More information is available via http://esfri.strw.leidenuniv.nl/