Efficient deep-UV light source has potential for food safety and counterfeit detection

Ultraviolet light has many industrial applications, because it is one of the best ways to kill harmful bacteria. The energetic wavelength of the band of light known as UV-C or deep UV (200 to 280nm) can penetrate the cell walls of bacteria, viruses and moulds, attacking their DNA and killing them. But producing these wavelengths is an awkward business. Lamps that emit deep-UV are based on light emission from xenon gas or mercury vapour, which is toxic; moreover, they are bulky and energy-inefficient.

However, such is the usefulness of UV for disinfecting water supplies, preserving food and checking for counterfeit currency (banknote designers are increasingly using ink visible under deep-UV to mark out legitimate currency) that many research groups are looking for better ways of producing UV-C. A group at Cornell University in New York State has now achieved the lowest wavelength yet using thin films of semiconductors rather than mercury vapour as the emitter.