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Ultrathin fiber lasers
A compact fiber laser system that can operate inside living tissues without damaging them has been recently developed by a team of researchers from Northwestern and Columbia Universities. The developed fiber laser has a thickness of just 50 to 150 nanometers, which is considered to be about 1/1,000th the thickness of a single human hair. The advantage of the laser system’s size allows the laser to fit and operate inside living tissues, resulting in efficient detection of disease biomarkers or even potential treatment of deep-brain neurological disorders, such as epilepsy.
The researchers confirm that the tiny fiber laser system demonstrates specific promise for the imaging process in living tissues. Also, this laser system is regarded as a biocompatible one; it is possible to excite the fiber laser with longer wavelengths of light produced by a laser beam, enabling it to emit at shorter wavelengths.
Importance of wavelength selection
Longer light wavelengths are required for the bioimaging process because these laser systems are able to penetrate farther into tissues than visible wavelength photons. Laser beam light with shorter wavelengths is often needed at those same deep areas. Hence, the developed fiber laser system is an optically clean system that allows efficient delivery of visible laser beam light at penetration depths accessible to longer wavelengths.
Use in confined spaces and electronics
The tiny fiber laser can be used in extremely confined spaces, comprising quantum circuits and microprocessors for ultra-fast and low-power electronics. Although the need for increasingly tiny laser systems or laser modules does not decline, there is one disadvantage that the researchers face: tiny fiber lasers offer less effectiveness than their macroscopic counterparts, and these laser systems use shorter wavelengths to power them.
Challenges of tiny fiber laser operation
This disadvantage causes challenges because “the unconventional environments in which people want to apply tiny fiber laser systems are highly susceptible to damage from UV light and the excess heat generated by inefficient operation”. The researchers were able to develop a fiber laser platform that solves these problems by applying photon upconversion. “Low-energy photons are absorbed and converted into one photon with higher energy” in the fiber laser system during the process of upconversion.
Testing and results of the fiber laser
The developed fiber laser was tested, and the researchers succeeded in producing “bio-friendly” infrared photons and upconverted them to visible laser beams. The laser system can operate under low powers, and it is smaller than the light wavelength; it produces visible photons when optically pumped with light that human eyes cannot see. The compact fiber laser systems can function at powers that are orders of magnitude smaller than observed in any current lasers.