New ultraviolet laser technology could increase storage capacity of optical disc media

Although ultraviolet semiconductor diode lasers are widely used in data processing, information storage and biology, their applications have been limited by the lasers' size, cost and power. Now researchers at the University of California, Riverside Bourns College of Engineering have overcome these problems by developing a new semiconductor nanowire laser technology that could be used to provide denser optical disc storage, superfast data processing and transmission and even to change the function of a living cell.

The breakthrough comes in the form of zinc oxide nanowire waveguide laser technology that the team says offers smaller sizes, lower costs, higher powers and shorter wavelengths than the current generation of ultraviolet lasers based on gallium nitride.

Until now, zinc oxide nanowires couldn't be used in real world light emission applications because of the lack of p-type (positive type) material needed by all semiconductors. Jianlin Liu, a professor of electrical engineering, and his colleagues solved this problem and created the p-type material by doping the zinc oxide nanowires with a metalloid element known as antimony.

They connected the p-type zinc oxide nanowires with n-type (negative type) zinc oxide material to form a device called a p-n junction node, that when powered by a battery results in highly directional laser light being emitted 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 team says the discovery could have a wide range of impacts. Because ultraviolet has a shorter wavelength than other lights, such as red used to read DVDs and violet used to read Blu-ray discs (even though Blu-ray lasers are referred to as "blue" they are in the violet range), the zinc oxide nanowires could be used to create denser optical disc storage.

The discovery also has applications in the fields of biology and medical therapeutics. Since the ultra-small laser light beam from a nanowire laser can penetrate a living cell, it could be used to excite the cell or change its function. It could also be used to purify drinking water.

Meanwhile, in the field of photonics, the ultraviolet light could provide superfast data processing and transmission and could also lead to the development of ultraviolet wireless communication technology, which is potentially better than state-of-the-art infrared communications technologies currently used in various electronic information systems.

Although the team has demonstrated the p-type doping of zinc oxide and electrically powered nanowire waveguide lasing in the ultraviolet range, Liu admits more work still needs to be done with the stability and reliability of the p-type material.