Phase-Separation Method Leads to Better AR Coating

Since the 1930s, it has been common practice to cover lenses with antireflection coatings to enhance the performance of devices that require the maximum transmission of light. Despite years of intensive research, broadband antireflection coatings are still limited by a lack of materials with low refractive indices.

Now a research team from the Universitat Konstanz in Germany has pioneered a method based on the phase separation of a macromolecular liquid to produce nanoporous films. The researchers dissolved polystyrene and polymethyl methacrylate in a solvent, which they then used to coat a glass slide. When the polystyrene was removed with a second solvent, it left 100-nm pores in the remaining polymer. These tiny holes cut down reflection and increased transmission of light by 8 percent.

The team reported its findings in the Jan. 22 issue of Science.