Lasers to kill viruses and improve DVDs

Ultraviolet semiconductor diode lasers are widely used in data processing, information storage and biology. However, their applications have been limited by their size, cost and power.

The current generation of ultraviolet lasers is based on a material called gallium nitride. However, Jianlin Liu, a professor of electrical engineering at the Riverside Bourns College of Engineering, University of California, together with his colleagues, has made a breakthrough in zinc oxide nanowire waveguide lasers. These come in smaller sizes, lower costs, higher powers and shorter wavelengths. The results of Liu’s studies have been published in the July issue of Nature Nanotechnology.

Until now, zinc oxide nanowires couldn’t be used in real world light emission applications because of the lack of a p-type, or positive type, material required by all semiconductors. Liu solved the problem by doping the zinc oxide nanowires with antimony, a metalloid element, to create the p-type material. The p-type zinc oxide nanowires were connected with n-type, or negative type, zinc oxide material to form what is called a p-n junction diode. Powered by a battery, a highly directional laser light emits only from the ends of the nanowires.

The discovery could have a wide-range of impacts. Zinc oxide nanowire lasers could be used to read and process much denser data on storage media such as DVDs because the ultraviolet has shorter wavelength than other lights. A DVD storing two hours of music could now store four or six hours of music. The ultra-small laser light beam from a nanowire laser can also penetrate a living cell, or excite its function from a bad cell to a good cell. The light could also be used to purify drinking water.

For photonics, the ultraviolet light could provide super-fast data processing and transmission. Reliable small ultraviolet semiconductor diode lasers may help develop ultraviolet wireless communication technology, which is potentially better than state-of-the-art infrared communication technologies used in various electronic information systems. It’s a work in progress.