Development of high-efficiency reflective grating by holographic processing for UV exoplanet science

We present our development of high-efficiency reflective grating development by holographic processing. Its primary objective is to carry out exoplanet science studies in the ultraviolet (UV) wavelength region using space-borne telescopes. While the final development goal is aspheric grating, in this study, we manufactured planar grating samples with laminar and blazed grooves for our first step in order to establish processing conditions and to evaluate characteristics of each grating. Geometry of the manufactured gratings is 30×30×10 mm, and their groove density is 2400/mm. It was confirmed by Atomic Force Microscope (AFM) evaluation that laminar and blazed grooves were constructed on the surface of each grating. The measured absolute diffraction efficiency achieved by the brazed grating is 40.2% and 44.1% at wavelengths of 122 nm and 131 nm, respectively. These values are higher than values of the laminar grating by factor of ∼1.5.