Cupric oxide photonic microcavities and their omnidirectional high-efficiency light-trapping characteristics

Cupric Oxide's black appearance hides interesting topographic structures and optical properties. This work examines the structure of thermally-grown cupric oxide and describes optical effects exhibited by surface layers of cupric oxide. It also highlights connections of surface optical properties with the intricate 3D micro and nanostructures that are formed on the surface during the oxidation process. These structures exist over several orders of magnitude in length we show that the CuO surface has a random microcavity structure that leads not only to strong photon trapping – giving CuO its black appearance – but also confers omnidirectional light absorption characteristics. This can benefit a number of applications – both active and passive. Our work also shows that CuO surfaces can be restructured by irradiation with a laser beam. Furthermore, it is shown that CuO surfaces can emit strong black body cavity radiation due to their high emissivity, which could throw light on interesting physical phenomena.