Transparent porous films with real refractive index close to unity for photonic applications [Dataset]

In this manuscript, we demonstrate a new approach to develop highly transparent thin films with effective refractive index close to unity that can be easily generalized to create highly performing photonic materials. Central to the procedure herein proposed is the used of sacrificial polymer nanosphere thin films that can be coated by chemical vapor deposition with thin interconnected shells of metal oxides, which gives rise to ultralow refractive index slabs upon removal of the organic template. The method herein presented is compatible with the processing techniques employed for other nanomaterials, which allows us to over-come the challenge of integrating ultralow refractive index materials into more complex photonic architectures. As proofs-of-principle of their potential significance in the field of photonics, we show how to obtain (i) a very thin film acting as a highly diffusive random optical medium, which results from the high refractive index contrast between the air-like refractive index film and spherical scatterers dispersed in it, and (ii) a film loaded with nanophosphors displaying enhanced photoluminescence out-coupling, as a result of the reduced light guiding losses achieved by the low dielectric contrast between the host of the emitters and the surrounding environment.