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Breakthrough with holmium-infused glass fibers
Holmium-infused glass fibers open the possibility of developing high-powered fiber lasers. Scientists from the USA have presented a new technique that allows designing powerful fiber lasers that are considered to be more efficient and safer for eye surgery due to the application of nanotechnology.
Rare-earth-ion-doped fiber technology
The nanoparticles are applied to produce a “rare-earth-ion-doped fiber” that consists of silica fiber infused with ions of the rare-earth element holmium. This material offers 85% efficiency of fiber laser systems.
Operating principle
The operating principle of the laser system is based on a pump source (quite often provided by another fiber laser) that excites the rare-earth ions, which lead to photon emission to create a high-quality laser beam at the desired wavelength.
Efficiency limitations in fiber lasers
The fiber laser technology does not provide 100% efficiency.
Pump energy vs. output light
The energy applied is seen as pump energy, but this does not represent the high-quality laser beam light at the needed wavelength. A much higher quality of light in the fiber laser system is possible to obtain at the specific wavelength; the energy that isn’t converted into laser beam light is wasted and converted into heat.
Importance of efficiency
This loss of energy defines the significant limitation of power scaling and the laser system’s quality, which makes qualities such as efficiency especially important. The doping process from nanoparticles enables fiber lasers to achieve 85% efficiency with a laser system that operates at a 2-micron wavelength (safe wavelength for eye surgery compared to standard 1-micron lasers).
Safety considerations for eye surgery
Scattered light risks
“The danger arises from the risk of scattered light being reflected into the eye during a laser beam’s operation.” For instance, scattered light from a 100-kW fiber laser operating at 1 micron can result in serious damage to the retina and blindness as well.
Eye-safe wavelengths
An “eye-safe” laser system that operates at wavelengths beyond 1.4 microns greatly decreases risks from scattered light.
Role of nanotechnology in overcoming challenges
Nanotechnology allows for overcoming several other challenges.
Protection of rare-earth ions
The first is that it protects the rare earth ions from the silica in fiber lasers.
Separation of ions
“The nanoparticle doping also separates the rare-earth ions from each other, which is helpful because packing them closely together can reduce the light output.” Conventional laser systems operating at 1 micron, applying a ytterbium dopant, are more resistant to these factors.