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New development of eye-safe fiber lasers
New highly efficient fiber lasers that are safe for the eyes have been developed by researchers from the U.S. Naval Research Laboratory. Based on the use of nanotechnology, the researchers include rare-earth ions of holmium in the core of the laser system’s silica fiber. This laser technology allows achieving an 85% level of efficiency with a fiber laser operating at a wavelength of 2 µm that is regarded as safer for the human eyes than a conventional 1 µm wavelength laser system.
Nanopowder doping process
The particle size of the nanopowder dopant is generally less than 20 nm. This is the reason why it was necessary to produce an appropriate crystal environment for the rare-earth ions in a fiber laser. The solution to the problem is the application of “clever” chemistry that dissolved holmium in a nanopowder of lutetia or lanthanum oxide or lanthanum fluoride.
Challenges of doping nanopowders into silica fiber
The researchers also face the challenge of successfully dope these nanopowders into the silica fiber in quantities that would be appropriate to reach laser system generation. The use of a room-sized, glass-working lathe enables cleaning the glass that is the future optical fiber with fluorine gases, then the American researchers molded the glass with a blow torch, and infused it with the nanoparticle slurry.
Creation of optical preforms
A rare-earth-ion-doped, 1-in. diameter glass rod or simply optical preform has to be then softened with a furnace and elongated to create an optical fiber about as thin as a human hair for its future application in the fiber laser system. The advantages of the novel fiber laser include not only improved eye safety, but the nanoparticle doping in the laser system also defends the rare earth ions from the silica, as well as separates them (the ions) from each other, thus saving the light output produced by a laser beam.
Eye safety advantages of 2 µm fiber lasers
The scattered light from the path of a 100-kW fiber laser operating at 1 µm is able to provoke severe damage to the retina, leading to blindness, while the laser system with wavelengths beyond 1.4 µm (like this fiber laser system) reduces the danger from scattered light.
Potential applications of eye-safe fiber lasers
The potential applications of the new specialty fiber lasers include:
- high-powered laser systems;
- amplifiers for defense, telecommunications, and even welding;
- laser-cutting.
The presented laser technology is considered to be highly prospective and commercially effective because the process of powder production and its installation into the optical fiber has a low cost and resembles the development of a telecom fiber.