The ESA mission Euclid is designed to map the geometry of the dark Universe by investigating the distance-redshift relationship and the evolution of cosmic structures. In the Euclid design of the NISP instrument, the spectroscopic channel uses four slitless low resolution grisms in NIR wavelength with four different orientations. Euclid grisms combine two optical functions: a grism function (ie dispersion without deviation at a specific wavelength) done by the grating associated with the prism and a spectral filter function done by a multilayer filter deposited on the entrance surface of the prism. After a successful development of a prototype of a grating realized by a photolithography process, we have begun a new phase of the prototype to manufacture a complete component, with a grism and a filter, and to validate its performance. Its development is very challenging as it requires manufacturing of the component in several steps which involve three different companies. We will present first the main optical requirements for the grism defined for the phase B and how the efficiency and wavefront specifications are split into the different components of the grism (mechanical mount, grating and filter). Then, we will describe the manufacturing process chosen for the NISP grism. Finally, we will present the first results of the optical characterisation of the prototype of the grism: global efficiency measurement, shape of the groove, wavefront contribution, and the trade-off made to achieve the final performance.

Date Published: 7 August 2014
PDF: 8 pages
Proc. SPIE 9151, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, 91515E (7 August 2014); doi: 10.1117/12.2055113

Published in SPIE Proceedings Vol. 9151:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation
Ramón Navarro; Colin R. Cunningham; Allison A. Barto, Editor(s)