Boffins build nanowire lasers from nappy-rash cream
Spread here for ultraviolet diodes
A new breakthrough in zinc oxide–based semiconductor nanowire lasers may support applications that range from killing viruses to stuffing more stuff on a DVD.
"People in the zinc oxide research community throughout the world have been trying hard to achieve this for the past decade," the leader of the research team, Jianlin Liu, said in a statement announcing the breakthrough. "This discovery is likely to stimulate the whole field to push the technology further.”
Pardon our provincialism, but the existence of a zinc oxide research community was news to us. Perhaps it shouldn't have been, in light of the many and varied uses of the compound, from diaper-rash ointment to cigarette filters to vulcanization.
And now, thanks to Liu – a professor of electrical engineering at the University of California at Riverside's Bourns College of Engineering – and his UCR and University of Central Florida research teammates, zinc oxide can be fabricated into ultraviolet semiconductor diode lasers – tiny nanowire waveguide lasers, to boot.
Ultraviolet lasers are prized because of their short wavelengths – down in the 340nm range. Wavelengths that short provide a number of advantages, such as enabling more-precise laser-based fabrication, and packing more data onto laser-readable/writable surfaces such as DVDs.
Semiconductor lasers are prized because they're tiny and have no moving parts. Laser diodes based on gallium nitride can operate in the near-ultraviolet range, but they're relatively expensive, and fabricating them is fraught with manufacturing challenges.
Zinc oxide had been considered a fine candidate for nanowire laser diodes, but there was one major problem that needed to be solved: although zinc oxide was well-suited to the n-type (negative) diode element, it wasn't able to take on the p-type (positive) role.
That's the breakthrough that Liu and his team have made. As explained in an article in Nature Nanotechnology with the suitably sci-fi title of "Electrically pumped waveguide lasing from ZnO nanowires", the boffins doped zinc oxide with antimony, and the p-type problem was solved.
"We are so excited about this new development," one of the UCF researchers, Leonid Chernyak, said. "While more research is needed, this may give us more options to explore, which could have some significant impacts on our daily lives from how we store our data to medical therapies that could help treat disease."
The disease-treatment therapies to which Chernyak refers are enabled by the fact that zinc-oxide nanotube lasers can be exceptionally thin – small enough to be pushed through a cell wall – and yet the light emanating from the end of the nanowire could be powerful enough to kill that cell, excite it in some way, or – as the universities' statements state with no explanation – "change its function from a bad cell to a good cell."
Like Chernyak, Liu freely admits that much more work needs to be done to improve the stability and reliability of the p-type zinc oxide material. But the team has built a prototype and hooked it up to a battery, and it lased away just swimmingly. ®
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