[en] We study theoretically the enhancement of the light extraction from an OLED (Organic Light-Emitting Diode) with nano air-bubbles embedded inside a glass substrate. Due to such a nano structure inside the substrate, the critical angle which limits the light extraction outside the substrate from the OLED is increased. The theoretical results show that the nano air bubbles near by the substrate surface can improve the efficiency of the light extraction by 7%. Such a substrate may also be suitable for photovoltaic cells or display screens.