UV Tuneable Laser Source
“You just realise that you’ve got this new capability that you had no way of getting out of universities. It almost seems like toys for us to play with!” – Roger Reeves.
About the Equipment:
The tuneable laser source produces any wavelength of light from red to UV. It is made up of two lasers – a pump laser, which produces green light and a tuneable dye laser, which produces variable frequencies of red light. It adds photons from the two lasers together in a process called frequency conversion to produce light across the UV spectrum. The resulting laser light covers a very narrow range of energies.
Roger’s group uses the tuneable laser source for Photoluminescence Excitation (PLE) measurements to reveal information about the structure, impurities and defects in materials – in particular, semiconductors. Several groups in the MacDiarmid Institute are developing new semiconductor materials and devices. To do anything useful with their materials they first need to find out their true properties. One of their biggest limitations for doing this is the defects and impurities in the crystal structure which alter the materials’ properties and can also be extremely difficult to detect. This is where Roger comes in. The new laser acts like a very fine probe with which he can find and analyse all the defects and impurities hiding in the material. This information feeds back to the team developing the material. “It’s a very rapid turn around,” says Roger – “a synergy of the quick characterisation back to the grower.” This is far more efficient than packing thirty samples in a suitcase and heading for the United States as researchers would have had to do in the past. The laser’s UV capability opens the technique up to a huge range of new materials. The group have recently been focusing on a UV-emitting semiconductor called zinc oxide which shows great potential in the optoelectronics industry, in particular as a replacement for the toxic mercury vapour used in fluorescent lighting tubes. They have already had a Marsden proposal accepted for the work and their collaborators in the Canterbury Electrical Engineering Department are working on devices based on the material. “Anything more we do in this advanced semiconductor area always brings it a step closer to commercialisation,” says Roger. The UV capability has also raised the possibility of working with organic materials. “Anything organic really responds well to UV light” Roger explains. “Fabrics fade, they break, they decompose so UV light is quite a good probe of organic materials.” Roger has already had interest from a group of engineers interested in looking at the effects of UV light on the structure of wood. Projects set up using the new laser are likely to draw more students to the group. “They will be different – broader,” says Roger. “The students will have a wider training base. They will be more capable when they go to different labs and do post-doctoral fellowships.”
The facility offers New Zealand researchers the opportunity to work with experts using a world class suite of equipment. Roger’s group already works with MacDiarmid researchers from the Electrical Engineering Department at Canterbury University, from IRL, GNS, Victoria and Auckland Universities as well as researchers in the US. He is sure the new laser will lead to many unexpected collaborations in the future.