New biocompatible nanolaser could function inside living tissues.

It is known that extensive research is currently being carried out to leverage laser technology to improve patient outcomes for different conditions. This includes the use of laser therapy to attack cancer cells, remove diseased tissue from delicate areas, blast away toxic brain proteins, and as a biosensor to detect and monitor disease. However, miniaturising and placing these devices inside the body at the site of disease greatly expands sensitivity and accuracy. Now, a study led by researchers at Northwestern University develops a tiny bio-compatible nanolaser which could, theoretically, be implanted inside living tissues without causing them damage. The team state the nanolaser, measuring less than 150 nanometers in thickness and requiring minimal amounts of power, can fit and function inside living tissues, with the potential to sense disease biomarkers or treat deep-brain neurological disorders, such as epilepsy. The study is published in the journal Nature Materials.

Previous studies show that the design of nanolasers are similar to conventional semiconductor lasers in common use for several decades. The difference is that the cavities of nanolasers are exceedingly small, on the order of the wavelength of the light they emit. Since they mostly generate visible and infrared light, the size is on the order of one millionth of a meter. This means nanolasers tend to be less efficient than their larger counterparts, requiring shorter wavelengths like Ultraviolet light to be powered, which can also damage surfaces or tissues being worked on. The current study develops a biocompatible nanolaser powered with longer wavelengths of light to emit at shorter wavelengths, allowing higher accuracy deeper within the body.

The current study develops a nanolaser platform using photon upconversion. In upconversion, low-energy photons are absorbed and converted into one photon with higher energy. Results show these low-energy, bio-friendly infrared photons upconvert to visible laser beams. Data findings show the laser beam can function under low powers and is vertically much smaller than the wavelength of light.

Results show the nanolaser is transparent and can generate visible photons when optically pumped with light invisible to the human eye. Data findings show the nanolasers operate at powers orders of magnitude smaller than those observed existing lasers. The lab state their nanolaser shows specific promise for imaging in living tissues. They explain that longer wavelengths of light are needed for bioimaging because they can penetrate farther into tissues than visible wavelength photons, however, shorter wavelengths of light are often desirable at those same deep areas.

The team surmise they have designed an optically clean nanolaser system that can effectively deliver visible laser light, with the potential to be used inside the body. For the future, the researchers state the continuous wave, low-power characteristics of their biocompatible nanolaser will open numerous new applications, especially in biological imaging.

Source: Northwestern University

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