Biocompatible nanolaser could function inside living tissues

October 21, 2019 //By Julien Happich
A team of researchers from Northwestern University and Columbia University has created a nanolaser that can be used in living tissues without harming them. Instead of relying on UV-light pumping, which can be harmful to living tissues, the researchers leveraged what’s known as photon upconversion to pump their nanolaser with infrared light and get their device to lase in the visible range.

The 50 to 150nm thick nanolasers described in the Nature Materials journal under the title “Ultralow-threshold, continuous-wave upconverting lasing from subwavelength plasmons”, consist of Yb 3+/Er3+-co-doped upconverting nanoparticles conformally coated on Ag nanopillar arrays supporting a single, sharp lattice plasmon cavity mode. The device exhibits a greater than wavelength λ/20 field confinement in the vertical dimension, and the intense electromagnetic near-fields localized in the vicinity of the nanopillars result in a lasing threshold of 70 W cm −2, orders of magnitude lower than other small lasers, the authors report.

“Our tiny lasers operate at powers that are orders of magnitude smaller than observed in any existing lasers,” said P. James Schuck, an associate professor of mechanical engineering at Columbia and co-leader of the study.

The nanolaser can operate in “extremely confined spaces” including quantum circuits and microprocessors for ultrafast and low-power electronics. It is made mainly of glass, which itself is biocompatible. The technology can also be excited by longer wavelengths of light while emitting at shorter wavelengths.

“Longer wavelengths of light are needed for bio-imaging because they can penetrate farther into tissues than visible wavelength photons,” says Teri Odom, the study co-lead and the Charles E. and Emma H. Morrison Professor of Chemistry in Northwestern’s Weinberg College of Arts and Sciences. “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.”

“Our nanolaser is transparent but can generate visible photons when optically pumped with light our eyes cannot see,” Odom continued. “The continuous-wave, low-power characteristics will open numerous new applications, especially in biological imaging.”

Specifically, the technology has the potential to detect disease biomarkers and help treat neurological disorders such as epilepsy.

Northwestern University -

Columbia University -

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