30 Nov 2011
Leading research institute sheds light on applications for photonics.
The term 'photonics' has, over the last couple of years, come to the forefront in a range of markets. Yet photonics, as a technology, has been around for decades. Today, photonics is seen as technology fundamental to future product development; to the point where it is has been named by the European Commission as one of six key enabling technologies needed to enhance industrial competitiveness.
While photonics research has been undertaken for many years, the understanding of what photonics is may be less than clear. Tim Holt, chief executive of the Institute of Photonics at Strathclyde University, explains. "Very simply, it's the generation, manipulation and detection of light, although others have more complicated definitions."
The Institute of Photonics is one of the world's leading researchers into photonics. Established in 1996 by Professor Allister Ferguson, the institute's mission is to 'bridge the gap between academic research and industrial application, of photonics, through excellence in commercially relevant research and its exploitation'.
"Prof Ferguson looked at what university research was doing and what industry required, and saw a gap," states Holt. "So the institute was established to undertake commercially oriented research into photonics." Today, the institute works with organisations from around the world, but Holt says much of its work is local. "We work with anyone who wants help, but, like many research organisations, most of our customers come from within a 100mile radius."
One of the challenges facing the institute is how to work with companies of different sizes. "SMEs are a challenge," he notes. "They tend to want something in the next six months, so we need ways to work with different sized companies. However, we can do short-term projects."
From the 'blank sheet of paper' in 1996, the institute has grown to having some 50 staff and students, with research focused on two of the three areas of photonics defined by Holt: generation and manipulation of light. "Photonics is a wide area," he admits, "and we can't do everything. However, we have niches in which we are interested and, if we see something developing, we'll follow it."
The institute is particularly interested in continuing its work with microleds. And this has aleady resulted in a spin-out company called mLED, which is focusing on applications within the life sciences sector. "But we're still looking at a whole range of applications for microleds," he points out, "and developing the technology even further." Potential applications include lighting and bio instrumentation, where the technology may find application in stimulating cells.
An area of research with potential in semiconductor manufacturing is the use of microleds in maskless lithography. As features sizes get smaller, optical lithography is becoming increasingly challenged. Maskless lithograpy – the direct exposure of photoresists – is being seen as a way forward. The attraction of microleds is that they emit in the ultraviolet to blue/green part of the spectrum.
"The challenge here is to develop technology that can create the features sizes needed," Holt points out. "We have created microleds just 5µm in diameter and these can be used to generate to generate feature sizes smaller than that by collimation."
The approach is being developed as part of the HYPIX project, in which five research groups at four universities are looking to create hybrid photonics/cmos devices. HYPIX has attracted £3.8million of funding from EPSRC, of which the institute is receiving £1.6m.
"We've already developed 64 x 64 and 128 x 96 microled arrays, in which each element is addressable individually," he explains. "They consist of GaN leds grown on sapphire. We can flip the leds and machine the sapphire to create a lens. Then the microleds can be attached to a cmos substrate, which drives them. Using the array, patterns can be built sequentially across a wafer, rather like a chessboard."
Meanwhile, researchers at St Andrews – a HYPIX partner – are using photonics as a more accurate way to identify and deactivate unexploded mines. The prototype sensor features a thin film of polymer, whose electrons jump into higher energy levels when exposed to light. When the 'excited' polymer is exposed to the electron deficient molecules common to many explosives, electrons are 'stolen' and the light emission is reduced.
The institute is also pioneering the use of diamond in microleds and lasers. "It's a tremendous material," Holt says. "It's transparent, is a good heat sink and can be machined to form a lens for a microled. And it's biocompatible."
One of the applications for diamond may be as a Raman converter for lasers. A problem with lasers is that it's not always possible to get the wavelength needed for a particular application. "We can use materials such as diamond to change a laser's wavelength," he adds. Current laser research interests at the institute include the use of Raman generation, led pumping of lasers and intra cavity adaptive optics, which improve laser performance over a wide range of operating conditions.
A lot of work is being done in the mid infrared region at wavelengths from 1.5 to 4µm, or 1500 to 4000nm. "Although there are lasers that generate wavelengths in the region from uv upwards," said Holt, "there are wavelengths you can't produce, but which industry thinks it needs. The mid infrared is a good example and that's where we're looking."
In previous work with an Australian university, the Institute has developed yellow lasers. This has resulted in a spin out company producing yellow lasers for medical applications.
While much of that work is about generating light, manipulating it remains a strong area of interest. "We're looking to develop deformable mirrors," Holt continued, "where we can change the shape of the mirror if the laser changes. For example, if the laser changes because of heat, we can compensate using a 'bendy mirror'."
There's a wide range of potential applications for this, but free space lasers are one possibility. "They are being considered for 'final mile' applications in communications," said Holt. "Adaptive optics can compensate for building sway and weather changes." But the approach has also been used to improve images generated during microscopy.
Holt says part of the reason for the institute's success is that all the work it does has commercial potential – its revenue per researcher is high, 'because of the good work we do with industry'. "I used to work for Ferranti," Holt notes, "which had a big R&D lab. All those kinds of company have gone, but the research still has to be done somewhere. Many people believe R&D is one discipline, but they are different."
There is a substantial demand for photonics in the UK. Research by the ESPKTN claims there are 1,500 UK photonics companies employing 70,000 people and sustaining a market worth £10billion a year. "And yet companies don't realise the role which photonics plays in their success," he concludes.
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