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Optical innovation

Filters rescue the possible commercial application of the chromium laser

eduardo cesarCr:LiSAF laser has wide spectral emissioneduardo cesar

Optical filters used by researches at the Lasers and Applications Center of the Nuclear and Energy Research Institute – IPEN, rescue the possibility of using a special type of solid state laser, known as Cr:LiSAF, in commercial applications. This laser has various promising properties, such as a wide emission spectrum and a long life span, but had been practically forgotten because its crystal has low thermal conductivity. “With the application of optical filters in its light emitter, we minimized the thermal problems and opened up the possibility that it can be used”, says Nilson Dias Vieira Junior, the manager at the Lasers and Applications Center (CLA).

The laser is only one of the components of the 1 terawatt system that is being developed within the thematic project funded by FAPESP. A terawatt of power is equivalent to 10¹² watts  – which corresponds to the amount  of 1 trillion watts. The research that resulted in the optical innovation was the theme of the doctorate thesis written by Ricardo Elgul Samad, and supervised by professor Vieira Junior.

The advance obtained resulted in a relatively simple solution, in the professor’s estimation. “We did with the Cr:LiSAF what the solar filter does with people on the beach. We eliminated the undesirable radiations and managed to use it as a high power laser”, says Vieira Junior. The innovation was published in the periodicals Applied Optics and Optics Letters. The study’s results caught the attention of the main magazine for divulging information in the photonics area, the Photonics Spectra, which published an article about the subject in its February edition of this year.

The Cr:LiSAF laser, an abbreviation for  Chromium-doped lithium strontium aluminum fluoride, allows, when used as a multi-pass amplifier, the emission of light with enormous coherence – that is, an electromagnetic wave with frequency and phase very well defined. When all of the 1 terawatt system is operating, this laser will be installed within it in order to amplify the energy of the pulses one hundred times. As the laser has very short pulses, measured in femtoseconds – 1 femtosecond is equivalent to 1 second divided by 1 quadrillion times -, the power of 1 terawatt is generated during this time and not during all of the operation. The expectation is that by the end of this month the system will be ready

With high power and extremely short temporal duration, the laser with the terawatt power will allow for an enormous range of applications, under strict safety norms. As it acts in a selective manner, without producing heat, it could be used, for example, on the tissue of a tooth without destroying what is around it. The laser will also be used to identify chemically atmospheric pollutants at kilometers of altitude. “The terawatt system could have the same type of function as the National Synchrotron Light Laboratory (LNLS), or that is to say, researchers from other institutions in the country and even abroad, could, together with the IPEN researchers, carry out experiments with the new equipment”, stated professor Vieira Junior.

The Project
Implementation of terawatt laser system and its applications
Thematic Project
Professor Nilson Dias Vieira Junior – IPEN
R$ 2,766,893.57 (FAPESP)