A process for preparing polyisobutenyl ethers by reacting a polyisobutene epoxide having at least one terminal epoxide group with itself, with other epoxides andor with nucleophiles selected from among alcohols and thiols in the presence of a Lewis-acid compound as catalyst andor a cationic photoinitiator with illumination is described. An oxide VCSEL structure includes a bottom mirror region, an active region atop the bottom mirror region, a top mirror region atop the active region, an oxidation cavity partially through the top mirror region, a first passivation layer covering a surface of the oxidation cavity, and a second passivation layer covering the first passivation layer. The character andor image advertisement is partially mixed with a specific image selected as one of the images for television broadcasting, mobile communication terminals and image storage media. This removal of the etch stop layer may be performed by wet etching the first portion of the etch stop layer using a phosphoric acid solution. The poisoning is reduced by treating the surface of the DARC film with a hydrogen or helium-containing plasma which is capable of removing the hydroxyl groups.