2/2013

High-brightness yellow lasers set for breakthroughs in medicine and spectroscopy 

Mircea Guina

Semiconductor and high-brightness laser research has the potential to revolutionize laser eye surgery, transform cancer treatment and redefine time.

Yellow lasers are rare, because semiconductors are not able to emit yellow light directly. So far yellow lasers have not been available in a compact size and at an affordable price. Professor Mircea Guina and his Semiconductor Technology Group at TUT’s Optoelectronics Research Centre have now developed a new laser technology platform for generating high-brightness yellow-orange radiation (i.e. radiation at a wavelength of 570–620 nm) with semiconductors.

The Tekes-funded BRIGHTLASE project capitalizes on TUT’s earlier research results gained with compound semiconductors as novel laser gain materials. It focuses on using dilute nitride compounds to achieve record-high output powers (> 20 W) at the above wavelengths from frequency-doubled semiconductor disk lasers.

“Our job has been to carry out the pre-commercialization process with yellow lasers by developing a volume scalable technology and building prototypes that enable engagement with application developers,” says Guina. “Coming this far has taken about ten years of research into functional materials, novel laser concepts, and a high level of commitment from the research team at TUT.”

Currently, laboratory versions of the laser prototype are being tested by application developers in Japan, the US, the UK and Lithuania. Professor Guina believes that products based on his team’s research will become commercially available in a few years time.

WHO: Mircea Guina, age 40

  • Head of the Semiconductor Technology Group, Optoelectronics Research Centre, TUT
  • Completed a PhD at TUT in 2002
  • Born in Romania
  • Family: wife Anca, nine-year-old daughter Elina, seven-year-old Matias and mother-in-law
  • Hobbies: tending to the allotment in Nekala, football
 

Huge benefits in various fields

There is a wide range of opportunities for applying this technology. “For example, in today’s eye surgeries, surgeons use green laser light to control the photocoagulation process. However, yellow light would be more advantageous since it is absorbed better by haemoglobin,” Guina explains. “Affordable and practical yellow lasers could also revolutionise other medical applications and be used, for example, to reduce cholesterol levels, remove tattoos and enable local cancer treatment.”

Spectroscopy in industrial control presents another field of possible applications. For example, yellow laser allows power plant operators to closely monitor combustion processes and improve efficiency by monitoring sodium atoms that absorb yellow light.

“A very interesting application is the optical atomic clock that can measure time about 100,000 times more accurately than standard caesium clocks. In general, the use of high-brightness narrow linewidth lasers at new wavelengths allows scientists to tackle ion cooling and trapping concepts that are also essential for quantum information processing and applications, such as quantum computing,” adds Guina.

“Cooperation with the National Institute of Standards and Technology in the US has already yielded very promising preliminary results and continuation has been planned in a project proposal that is currently evaluated by the Academy of Finland.”

 
To generate yellow laser light, the wavelength is halved using
a nonlinear crystal. In the image, the laser beam has been split
into multiple beams by means of a so-called diffractive element.
 

A material technologist who fell for gardening

What keeps Guina motivated to pursue research on lasers? “I’m a materials scientist whose research interests also include laser physics. A laser is just one of the applications of semiconductors and helps us make a fast link between basic material research and high impact applications. It is fulfilling to develop technology that can help people recover faster after an eye operation and increase the effectiveness of cancer treatment,” he answers.

Guina has been at TUT since 1999 and has settled in Tampere with his family. Last year they bought an allotment in Nekala, and Guina could pursue his passion for gardening. “We grow herbs and vegetables, including some you will not easily find in Finnish gardens such as garlic, but we also had a great harvest of apples and berries. In many ways, gardening resembles my philosophy of applied research. Both are a team effort and it’s a delight to see the results of one’s work put to good use, in this case on the kitchen table!”
 

Text: Marjaana Lehtinen
Photo: Petri Laitinen

 
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