Researchers have developed a tiny nanolaser that can function inside of
living tissues without harming them.
Just 50 to 150 nanometers thick, the laser is about 1/1,000th the thickness
of a single human hair. At this size, the laser can fit and function inside
living tissues, with the potential to sense disease biomarkers or perhaps treat
deep-brain neurological disorders, such as epilepsy.
Developed by researchers at Northwestern and Columbia Universities, the
nanolaser shows specific promise for imaging in living tissues. Not only is it
made mostly of glass, which is intrinsically biocompatible, the laser can also
be excited with longer wavelengths of light and emit at shorter wavelengths.
“Longer wavelengths of light are needed for bioimaging because they can
penetrate farther into tissues than visible wavelength photons,” said
Northwestern’s Teri Odom, who co-led the research. “But shorter wavelengths of
light are often desirable at those same deep areas. We have designed an
optically clean system that can effectively deliver visible laser light at
penetration depths accessible to longer wavelengths.”
The nanolaser also can operate in extremely confined spaces, including
quantum circuits and microprocessors for ultra-fast and low-power electronics.
The paper was published today (Sept. 23) in the journal Nature
Materials. Odom co-led the work with P. James Schuck at Columbia
University’s School of Engineering.
While many applications require increasingly small lasers, researchers
continually run into the same roadblock: Nanolasers tend to be much less
efficient than their macroscopic counterparts. And these lasers typically need
shorter wavelengths, such as ultraviolet light, to power them.
“This is bad because the unconventional environments in which people want
to use small lasers are highly susceptible to damage from UV light and the
excess heat generated by inefficient operation,” said Schuck, an associate
professor of mechanical engineering.
Odom, Schuck and their teams were able to achieve a nanolaser platform that
solves these issues by using photon upconversion. In upconversion, low-energy
photons are absorbed and converted into one photon with higher energy. In this
project, the team started with low-energy, “bio-friendly” infrared photons and
upconverted them to visible laser beams. The resulting laser can function under
low powers and is vertically much smaller than the wavelength of light.
“Our nanolaser is transparent but can generate visible photons when
optically pumped with light our eyes cannot see,” said Odom, the Charles E. and
Emma H. Morrison Professor of Chemistry in Northwestern’s Weinberg College of
Arts and Sciences. “The continuous wave, low-power characteristics will open
numerous new applications, especially in biological imaging.”
“Excitingly, our tiny lasers operate at powers that are orders of magnitude
smaller than observed in any existing lasers,” Schuck said.
Journal article: https://www.nature.com/articles/s41563-019-0482-5
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