MU laser lab receives funding for back-to-the-basics research approach
In the Femtosecond Laser Lab on the lower level of MU Engineering’s Lafferre Hall, Assistant Research Professor Vitaly Gruzdev holds out a shard of boiled chicken bone.
Side by side, he points out two tiny holes on the bone’s surface, cut by lasers. One hole, with the surrounding area burned black, was cut using nanosecond-long pulses. The second hole is more cleanly cut, with none of the surrounding damage of the first.
“You see the difference,” Gruzdev says of the second hole. “No black edges. And if I were to use a microscope to show details of this hole, you would see no microfractures and no damage to the surrounding area.”
This clean and precise hole was cut with femtosecond laser pulses, which last one-millionth of one-billionth of a second. Though both are faster than a blink of an eye, a nanosecond and a femtosecond are worlds apart in terms of the quality of a laser cut.
The MU Femtosecond Laser Lab is doing research on femtosecond laser technology in an effort to refine it. The lab recently received a grant from the Air Force Office of Scientific Research (AFOSR) to support that research over three years.
MU’s femtosecond laser, one of three lasers in the laser lab, generates ultrashort pulses of light that can cut almost anything, including glass and diamond. According to Gruzdev, the quality of the cut is “almost perfect.”
When these ultrashort pulses are focused into a tiny spot, they can gently remove material without affecting the nearby area, he said.
Where a regular laser may create debris or damage the surrounding area, a femtosecond laser can cut the material without causing any collateral damage.
The cuts are extremely precise, Gruzdev said. For example, they’re capable of damaging particular proteins in a food source without damaging other proteins, a topic of research Gruzdev pursued with the MU biochemistry department after receiving Mizzou Advantage funding in 2011. The project ended in the research team innovating a new technology, and a patent is now being pursued.
Another application of femtosecond lasers is in surgery, where longer-pulsed lasers create black edges that doctors then have to remove with surgical knives or saws. If that step could be removed, Gruzdev believes the healing process could be shortened.
Though researchers working with femtosecond lasers have discovered plenty of possible applications for the technology, one conspicuous question is still left unanswered; how does the technology work?
“That is exactly one of the problems that is not well understood so far,” Gruzdev said. After all of the research that has been done, the mechanisms behind how lasers work are still not clear.
“There are several models, but actually most of those models come to a certain fundamental level … it doesn’t go any deeper,” Gruzdev said. So to be fully utilized, the technology has to be refined. And to be refined, it must first be understood.
“OK, you can make a clean cut — can you make it even better? What is the optimal balance of speed and quality of the cut?” Gruzdev said. “That’s the question. If you do not understand how it happens, you cannot say how to improve it.”
How do lasers, which are made of light, remove mass without using heat?
“When you think about it, it’s a real magic. Something without mass moves something with real mass that we can feel… we do not understand how it happens, but somehow it works.”
Despite it’s many benefits, a drawback of the laser technology is that it takes a long time to cut material. Gruzdev said, for example, that where one regular laser pulse would suffice during a surgery, about 30 femtosecond pulses would be needed to cut the same amount of bone.
Gruzdev said the lab’s number one goal is to find a way to make femtosecond pulses cut materials faster. To that end, the lab conducts experiments in an attempt to create a theoretical model and simulation for how ultrashort laser pulses induce ionization in dielectric crystals — the reason for the damage.
Laser interactions such as welding, cutting and surface structuring include just a few fundamental interactions, he said. It’s those fundamental interactions that his lab wants to look at. “If you understand those interactions in details, then we can figure out how to optimize laser technology, how to make them cheaper and more effective.”
Gruzdev said his own dentist understands the impact this technology, if refined, could have in his field of work.
“When I first told him, he got absolutely crazy about that…. Each time I go to his office, he asks me the same question: ‘Have you finished your unique laser instrument yet? I would like to test it in my office. Let me know when you are finished and I’d like to purchase it.’”
Microfractures caused by drilling teeth create tiny cracks where bacteria can get in, destroying the tissue around a filling and decreasing its life span. Gruzdev’s dentist recognizes that an instrument that works without causing microfractures could revolutionize dentistry.
The tissue damage that comes from mechanical tools requires fillings to be replaced from time to time, Gruzdev said. “If this technology comes to dentistry, you would have to visit once, and you are done for the entire rest of your life, because lasers do not destroy the tissue around the cavity.”
Despite its potential, femtosecond laser technology is still not prepared to make the move to operating theaters or dentist offices; it’s still too slow to be practical in those settings. But once its speed is improved, the impacts of such a technology could be far-reaching across many fields and MU Femtosecond Lab will continue its work to push the technology forward.
Note: A 2008 gift from Bill Thompson BSCiE ’68, and his wife Nancy was used to purchase Mizzou Engineering’s femtosecond laser.