Zinc oxide nanowire lasers boost DVD storage capacity

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

The current generation of ultraviolet lasers is based on gallium nitride, but Jianlin Liu, a professor of electrical engineering, and his colleagues have made a breakthrough in zinc oxide nanowire waveguide lasers, which can offer smaller sizes, lower costs, higher powers and shorter wavelengths.

Until now, zinc oxide nanowires could not be used in real-world light-emission applications because of the lack of p-type material needed by all semiconductors. Liu is said to have solved this 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 zinc oxide material to form a p-n junction diode. Powered by a battery, highly directional laser light emits only from the ends of the nanowires.

‘People in the zinc oxide research community throughout the world have been trying hard to achieve this for the past decade,’ Liu said. ‘This discovery is likely to stimulate the whole field to push the technology further.’

The discovery could have a wide range of impacts.

For information storage, the zinc oxide nanowire lasers could be used to read and process much denser data on storage media such as DVDs because the ultraviolet has a shorter wavelength than other lights, such as red. For example, a DVD that would store two hours of music could store four or six hours using the new type of laser.

For biology and medical therapeutics, the ultra-small laser light beam from a nanowire laser can penetrate a living cell, or excite or change its function. The light could also be used to purify drinking water.

For photonics, the ultraviolet light could provide super-fast data processing and transmission.

While Liu and the students in his laboratory have demonstrated the p-type doping of zinc oxide and electrically powered nanowire waveguide lasing in the ultraviolet range, he said more work still needs to be done with the stability and reliability of the p-type material.

Liu’s findings have been published in the July issue of Nature Nanotechnology.