The French Commission for Atomic Energy is currently involved in a project which consists of the construction of a 2 MJ/500TW (351-nm) pulsed Nd:glass laser and which will be devoted to Inertial Confmement Fusion (ICF) research in France. With 240 laser beams and almost 10,000 m2 in coated area required, the proposed megajoule-class laser will be the largest laser system ever built in the world. Room temperature and atmospheric pressure deposited coatings such as sol-gel for antireflective (AR) applications and silicone for environmental protective coatings, with high optical and laser-included damage performance, can be applied at a low cost compared to conventional vacuum deposition processes. Today, we are using such a technology to AR-coat prototypes of lenses, windows, blast-shields, debris-shields, flashlamps and harmonic converters required by our proposed megajoule-class laser. This technology has also been selected for the preparation of multilayer highly reflective (HR) coatings for use as cavity-end deformable mirrors in the laser system. Due to their suitability to ensure appropriate deposited optical thickness, room-temperature deposition techniques such as dip-, spin- or laminar-flow-coating have been optimized for such laser coating production.