Antireflection coating on large lenses for G-CLEF blue camera

The GMT-Consortium Large Earth Finder (G-CLEF) is a spectrograph, to be delivered as the first light scientific instrument for the Giant Magellan Telescope (GMT), and divided into a red and a blue channel. <br/> In the frame of this project, Bertin Winlight is in charge of the manufacturing of the blue camera lenses, and entrusted CILAS to develop and realize the antireflection coatings on the 8 different lenses of this camera. The camera consist of 8 lenses with diameter in the 190 – 323 mm range made of CaF2 and other optical glass (BAL35Y, PBM18Y, BSM51Y). We present the results on the design, development and manufacturing of antireflection coating with PIAD (Plasma-Ion Assisted Deposition) technology, which is well adapted to produce very dense layers and high quality coatings for severe environments. <br/> The design of antireflection coating, in the spectral range 350-541nm, has taken into account large diameter and high curvature of the lenses and has been experimentally validated on a dummy shape. Moreover a dedicated coating process has been implemented and qualified on CaF2 substrates, leading to the successful coating of the 8 different lenses.