Embodiments of the present invention provide an apparatus that reduces an audible noise produced in a power supply. Composite materials obtainable according to the process of the invention have desirable characteristics regarding adherence to the substrate, durability, hydrophilicity, wettability, biocompatibility and permeability and are thus useful for the manufacture of biomedical articles such as ophthalmic devices. A coating layer is formed over an outside of the lateral faces of the active layer, an upper electrode is electrically connected to an upper portion of the n-GaN layer, and a distributed Bragg reflector is formed over the n-GaN layer and the upper electrode. In a third phase, the FEXTNEXT transfer function is determined based on the measurements of the first and second phases.