An NUI Galway research team is using models to understand what happens to atoms when a laser strikes a surface, reports Dr Claire O'Connell
A four-strong research team at the National Centre for Laser Applications (NCLA) at NUI Galway is tapping into a national supercomputer facility to look at how lasers interact with materials and produce debris. Ultimately, the researchers want to make manufacturing processes more efficient in areas such as medical devices and micro- electronics.
In recent years, laser technology has produced powerful tools such as UV diode-pumped solid-state systems (UV-DPSS) where the light source is a diode rather than a flash-lamp, explains Dr Gerard O'Connor, who is director of fundamental research at the NCLA. This makes the process of generating lasers more efficient and results in more robust lasers that are easier to use for minute operations.
"These have really enabled a huge number of applications, particularly in areas where we're talking about making things down in the micron or nanometre level," he says.
Unlike daylight or room lights, which are made up of many wavelengths, lasers contain radiation of a single wavelength, and here too the newer lasers can be improved.
"The efficiency of generating the laser radiation is so good that we can put the beams through additional crystals which convert the wavelength from one micron [one millionth of a metre] to half a micron - we can change the colour of the laser wavelength," says Dr O'Connor.
Materials absorb these shorter laser wavelengths better at their surfaces, he adds, which localises the beam and provides more options for manufacturing technology.
"There are great opportunities to apply these in micro-manufacturing, for example in drilling small holes or making small incision cuts," Dr O'Connor says.
However, the amount of energy that goes into the new UV-DPSS lasers, which pulse at 300,000 times per second, can be problematic. Dr O'Connor cites the example of drilling a tiny hole about a micron wide into a medical device or a microelectronics circuit.
"The energy you need to pulse is quite large so you tend to get a lot of material vapourising with each pulse and you can't extract it out of the hole quick enough," he says. "Where the width of the hole is very small, the depth becomes relatively large. You tend to be drilling down the bottom of a deep hole with large side walls which trap a lot of the vapours."
Solutions to the problem include pausing the pulses at intervals to allow trapped vapours to escape, or changing the machining environment, explains Dr O'Connor. Working out the best strategy to clean up the process is where supercomputers come in.
The NCLA researchers link into the Irish Centre for High-End Computing, which gives them supercomputing tools to analyse interactions between the laser and the material they are drilling or cutting.
"We build up a model of around a million atoms in our material and we write a computer programme where we describe how the laser pulse interacts with this series of atoms," says Dr O'Connor. This allows the researchers to develop simulations that look at how the material responds to the laser pulses on a femtosecond (one millionth of a billionth of a second) scale.
"This is really valuable in understanding how the debris is emitted," says Dr O'Connor. "We can monitor the process at a period in time where we just can't do it experimentally."
The group has now developed working models of the interactions and the next step is to work out solutions that modify the thermodynamics of the system to extract the debris, says Dr O'Connor. "The simulation gives us a test bed for doing that."
Their findings could have wide implications in areas such as biotechnology and information technologies, Dr O'Connor says.