Researchers at Northwestern University have created a nanolaser that can be used in living tissues without harming them. Developed in conjunction with a team from Columbia University, the nanolaser can be 50 nm to 150 nm thick, which allows it to fit and fully function inside living tissues. “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. Researchers have developed a nanolaser that can function inside of living tissues without harming them. Courtesy of Northwestern University. “Longer wavelengths of light are needed for bioimaging because they can penetrate farther into tissues than visible wavelength photons,” said 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.” Nanolasers have typically been less efficient than macroscopic devices, and most often require shorter wavelengths (i.e., UV light) to power them. However, according to Schuck, unconventional settings such as inside living tissue have been difficult for researchers to explore because they are “highly susceptible to damage from UV light and the excess heat generated by inefficient operation.” The researchers were able to resolve such issues with a nanolaser platform that uses photon upconversion. With this technique, low-energy photons are absorbed and converted into one photon with higher energy. In its study, published in Nature Materials, the team used bio-friendly (low-energy) IR photons and upconverted them to visible laser beams. This makes the new nanolaser smaller vertically than the wavelength of light and allows it to function under lower powers. “Our nanolaser is transparent but can generate visible photons when optically pumped with light our eyes cannot see,” Odom said. “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. The research was published in Nature Materials (https://doi.org/10.1038/s41563-019-0482-5).