High intensity and hugely popular

Nilson Dias Vieira Junior talks about the role the Nuclear and Energy Research Institute had in developing and popularizing the use of lasers in a wide variety of fields in Brazil

By Heitor Shimizu, in Lincoln  |  Agência FAPESP – Today the use of lasers in a wide variety of medical and dental procedures is common practice. But in Brazil in the 1980s, had someone told you they’d had laser treatment on their face or mouth – and were happy with the results – they would have been viewed with suspicion.

The Nuclear and Energy Research Institute (IPEN) has played a key role in the development of lasers and in popularizing the use of pulses of light amplification by the stimulated emission of radiation in a wide variety of fields in Brazil.

It was in the early 1980s when researchers from IPEN mastered the technology involved in growing yttrium lithium fluoride (YLiF4) crystals, with added rare earth ion neodymium – an addition, known as doping, that gives the crystal the semiconducting properties of the other element.

“The YLiF4 is birefringent, that means it has different rates of refraction for different directions of light propagation. The crystal gave rise to the first solid state lasers produced in Brazil, which were made with domestic components or adapted to our needs,” said Nilson Dias Vieira Junior, a researcher at IPEN and one of the speakers at FAPESP Week Nebraska-Texas, which is bringing together researchers from the United States and Brazil through September 22 in the cities of Lincoln (Nebraska) and Lubbock (Texas). He talked about the applications for high intensity lasers.

Vieira Junior joined IPEN in 1979. “I was invited by [physicist] Spero Morato to work on developing the first solid state laser in Brazil. Two years later, we were able to make it work, giving rise to the Laser Development Group, a special processes area within the Institute,” he told Agência FAPESP.

The researcher explained that after the initial pulsed and continuous lasers, IPEN produced crystals doped with another chemical element, holmium. These crystals allowed the production of lasers that emitted wavelengths that measured just a few micrometers and were more suited to applications in medicine and dentistry. That was also the starting point for applications in materials processing.

“We developed pulse lasers, continuous lasers, we covered all the technology of laser development and managed to vertically nationalize the entire process,” Vieira Junior said.

Once lasers became available, applications for them began to appear. “We helped develop a cochlear implant with the use of laser to obtain components measuring 300 micrometers in diameter. We did welding on a Brazilian Space Agency rocket prototype. In 1992, we began developing an extremely high energy holmium laser, which was used to remove material from teeth,” he said.

“In addition to the development of lasers, it is worth noting the training of personnel. From the beginning, we saw the importance of working with professionals from many different fields, and we understood that we could also contribute to training. We began to engage in various activities to promote the applications of lasers in Brazil,” said Vieira Junior, who served as IPEN supervisor from 2008 to 2012, and member of the FAPESP Board of Trustees from 2000 to 2006.

The Laser Development Group gave rise to today’s Center for Lasers and Applications (CLA) at IPEN. It was through this center that the first Professional Science Master in Lasers in Dentistry program was established in Brazil, offered in conjunction with the School of Dentistry at the University of São Paulo.

“IPEN and the USP School of Dentistry worked together from the very beginning. We have trained over 160 individuals through the master’s program, and this has resulted in the development of several therapeutic methods currently in clinical use,” Vieira Junior said.

Among them is the use of laser on caries prevention, microbial reduction in endodontics and periodontics through using low intensity laser, laser Doppler flowmetry and mitigation of the undesirable effects of radiation therapy and chemotherapy, such as oral mucositis.

The CLA is currently involved in developing therapeutic techniques through the use of nanomaterials. This line of research is investigating the effects of silver nanoparticles and quantum dots on optical diagnostics and therapeutic applications.

Vieira Junior is excited about the popularity of lasers in medical and dental applications, but warns of the care that must be taken with their use. “Lasers are important for applications and are widely available today. Niche applications are huge, but we need to understand the processes involved in using them,” he said.

“We made major contributions to IPEN with regard to communicating proper use of lasers. We set up safety protocols for patients and equipment operators. It is important to know the correct dose, the site on which to use it, and the type of laser that can be used. Just because it is popular does not mean it can be used on simply anything. Lasers are instruments capable of curing but also of injuring if misused. The laser pointer with the green light can even blind someone,” said Vieira Junior.

Materials and intensity

In materials processing, IPEN is developing applications that meet the demands of public and private companies, in work such as cutting, drilling or welding, among other things. Welding dissimilar materials for the aerospace industry and the medical fields are some of the success stories. “The Institute also has a processing unit with femtosecond lasers to produce microstructures,” Vieira Junior said.

The CLA is also developing scientific and technological competency in lasers for applications in environmental monitoring as well as in the nuclear industry, training human resources and generating products and services. The growth in demand for lasers along with maturing technology has led to the establishment of Lasertools, a spin-off of IPEN.

Laser development at IPEN has had the support of FAPESP since the very beginning. FAPESP has awarded more than 1,300 grants and scholarships to researchers at the Institute. IPEN researchers are currently engaged in 18 projects funded by FAPESP research grants.

IPEN researchers have also published in high impact science journals. In 2015, for example, Vieira Junior and his colleagues published a paper in the journal Scientific Reports, included in the Springer Nature Group, in which they described the synthesis of diamond from graphite by ultrafast laser driven dynamic compression. The study was carried out in partnership with researchers from the National Synchrotron Light Laboratory (LNLS) and the National Nanotechnology Laboratory (LNNano) at the Brazilian Center for Research in Energy and Materials (CNPEM), in Campinas, in São Paulo State.

Thanks to the development of high density lasers at IPEN – including the strongest in the Southern Hemisphere, operating at 0.5 TW –, researchers have been able to produce in the laboratory the extremely high thermodynamic conditions of temperature and pressure required for the transformation of carbon into diamond, as described in the article.

“One of the next steps will be to accelerate laser-charged particles to higher energies, energies comparable to electron rest, which are relativistic. The final goal will be to accelerate protons for use in nuclear medicine. We have to characterize, optimize and understand the basic phenomena, in line with the largest laser development centers in the world,” said Vieira Junior.