Development of atomically thin optical devices with graphene for astronomical applications

Thin-film optical devices have been on board X-ray satellites. We have proposed to utilize graphene in X-ray astronomy. Graphene is atomically-thin but possesses superior heat resistance and mechanical strength. Thus, we have been developing ultra-thin film optical devices capable of achieving ultra-high transmittance in the extreme ultraviolet to soft X-ray bands. Transfer processes have been optimized to realize large aperture structure and we successfully fabricated freestanding structures of 300 µm in diameter with a single layer and 800 µm with a bilayer of graphene. Moreover, we conducted high-speed atomic oxygen irradiation tests. The results showed no significant change in the observed D/G ratio in the Raman spectra at fluences up to 2×10^17 atoms/cm^2. However, at a fluence of 2×10^18 atoms/cm^2, the D/G ratio exhibited a significant change from 0.04 ± 0.03 to 0.8 ± 0.4. In this presentation, we will report our recent status.