What next for the product once famously described as a solution in search of a problem? Warren Clark hears the views of leading industry figures
The laser has come a long way from its inception some 40 years ago, but where can it go from here? Eugene Arthurs, executive director of SPIE, says: 'Charles Townes' colleagues may have had good basis to tease him that the laser was a solution looking for a problem in the 1960s. Now, laser applications abound, and it would take volumes to describe them. I don't think I am atypical, with maybe 10 lasers in my home, in multiple CD and DVD players, and computer CD and DVD read/write drives. Of course, I wouldn't have these lasers or the newer devices but for the laser lithography used to fabricate the highest density silicon circuits. Lasers are well established in many manufacturing technologies, for precision delivery of intense power for scribing, cutting welding, and for precise 2D and 3D metrology. The many thousands of less powerful - but precise - lasers cutting fabrics, making patterns in glass blocks, customising trophies and so on, really show how the laser has moved from technical marvel to common tool. Lasers in hospitals, dermatological suites, dental surgeries and eye clinics benefit many, day in, day out. I'm not so sure about the laser comb for hair stimulation, but the laser beard sculpting available in New York supposedly works - as it should for $150.
'So, 45 years has brought us from Maiman's "Death Ray" headlines to commoditisation, and with it a sort of anonymity. I believe we have much more ahead. The laser has unique properties that will make it the only solution for challenges in this century of the photon. We have only seen the tip of the iceberg in telecommunications; wireless is wonderfully convenient but bandwidth-limited. As miniaturisation moves us into the nanoworld, whether the future be with molecular electronics or nanostructure computing, the future of connections is with light, and only a laser can provide adequate power density for nanoscale connections. Perhaps I am wrong and optical computing will win the post-silicon future, but that would mean an even more central role for lasers. And lasers will be central to the future data storage requirements for HD3D displays, volumetric data storage way beyond Blu Ray or HD DVDs.
'The laser will ultimately - I believe shortly - fulfil its promise in the huge field that was called analytical chemistry, and become increasingly prolific in diagnostic medicine. Spectral properties and spatial coherence will assure this as the lab shrinks to chipscale. The future world of pharmagenomics will rely on lasers for genetic typing and perhaps for activation of the appropriate therapeutic course.
'The laser may also hold the key to the future of energy. Information from huge systems, such as the NIF and Laser MegaJoule, and the rapid progress in tabletop high-repetition petawatt systems, may converge to practical fusion power sources. Scoff as you will, but Townes, now a hale and hearty 90, is having the last laugh - and there should be a lesson there. We wish him many more years to be fascinated by the ubiquitous laser.'
Paul Meissner, executive vice president of global business operations at Coherent, believes that applications, per se, are not a problem. He says: 'There are an unbelievable number of potential applications, but the question for us is: “What will it take to drive those applications into the volume market?” I think this is a bigger issue. We believe that aspects such as reliability, product lifetime and the product quality need to be addressed before new applications can be supplied effectively. These are advances that I would classify as product innovation, rather than technology innovation, and until they're addressed, the laser will continue to be a limited use solution, employed only in niche applications for which there are no other options.
'We think, therefore, that the barriers to any new applications are not necessarily because the technology is not there, but rather that the reliability of the product doesn't foster widespread adoption. For example, no one would hesitate to design a product that incorporates ICs, but they only use lasers when they have to. Once that reliability does arrive, product designers won't hesitate to utilise lasers, and our volumes will increase. Then, the advantages of scaling will come into play, and provide customers with access to a more affordable product.'
Jon Richardson, UK sales manager at Newport Spectra Physics, says: 'As a company, we have always tried to drive technology forward. In recent years, this has meant shifting away from gas to solid-state lasers. We believe that small gas lasers, like the air-cooled ion laser, are likely to be phased out altogether in the near future. Customers are now seeking complete sealed systems, which are compact, hands-off and computer-controlled. We've certainly seen this in our ultrafast laser product lines. These sealed system lasers need to provide a reliable source of energy, rather than be an experiment in themselves.
'Other growth areas will be in thin disk lasers, which are cheaper to manufacture, and can be used for applications such as sapphire pumping, and also fibre lasers, which have a big future ahead of them. As far as applications are concerned, the biomedical market will become increasingly important. Any fluorescency application, such as DNA sequencing, will be a growth market.'
Andrew May, managing director of Rofin-Baasel UK, is involved in laser marking. As far as his sector of the market is concerned, there are changes ahead: 'I think we can already see some interesting industrial laser developments in 266nm (frequency quadrupled) lasers (which have been around for a long time in “scientific” formats) and in ultrafast (femto/picosecond) lasers, but the impact on laser marking applications of these is likely to be minimal. More interesting are fibre lasers and disc lasers; both exhibit higher efficiencies and better beam quality at higher powers than the rod-based lasers. In one sense disc and fibre lasers represent two extreme changes in the geometry that limits rod lasers. The problem with rod lasers is that there is only a modest surface area from which to extract the heat that develops within the rod - the consequence of which is that at high pump powers the thermal gradient along the radius of the rod leads to a refractive index gradient, which limits the beam quality of the output. By changing the aspect ratio of the cylinder from a rod to either a disc or a fibre, this problem can be largely eliminated.
'Fibre lasers are becoming available as the "engines" for laser markers; the extent to which they will impact future markets is not yet clear. They are not normally q-switched in the same way as rod lasers, but act as amplifiers for a seed source which is modulated at high frequency. The effect in terms of output is similar - with the possible upside of being able to maintain a flat peak power profile with respect to q-switch frequency. This means that in principle one can change the q-switch frequency according to what the process requires (in terms of pulse overlap for example), without changing the peak power characteristics of the output. Possible downsides might be lower peak powers ultimately achievable, and issues with back-reflections owing to the high-gain amplification of fibre lasers.
'Alternatively, at the other geometric extreme, the disc laser, designed with a lower gain, is less sensitive to back reflections, and a recently-demonstrated model has yielded nearly 100W of TEM00 q-switched power. Such laser output requires galvo heads to deflect the beam very rapidly and will provide more impetus to suppliers of this technology to extend the speed capabilities and the field sizes.'
Bookham is a company involved in both industrial lasers and, of course, telecommunications. On the pump and industrial side the designs of 980nm lasers for Er doped fibre pumping are now very mature, according to Bookham, with the emergent generation of devices delivering well over half a watt of single mode pump power, powering +20-23 dBm amplifiers; it seems unlikely that further increases in power will be required.
'We will see further expansion of this market, with cost reduction being a central theme,' says Dr. Steve Turley, chief commercial officer. 'We see the industrial laser market entering a period of change where new technologies such as disc lasers and fibre lasers are emerging. In addition the applicability of direct diode applications is spreading in many areas. All of these are reliant on the increasing power and brightness now reliably available from pump diodes at wavelengths between 800 and 1000nm.
'A key parameter for the market is the cost to deliver power. New high-power pump diode technologies offer much greater capability due to advances in chip design and the application of hard soldering techniques that circumvent the limitations of soft solder at high power.
'All of this means that concerns over pump laser reliability for industrial applications can at last be left behind and diode laser technology can now enable rapid advances in economics and performance of the industrial laser market.'
On the telecommunications side, Andy Carter, VP research and development, says: 'We predict that in the future we will see pervasive tunability, based on monolithic fullband tunable lasers, delivering equivalent performance to standard DFB lasers with the added benefit of full band tunability.
'We also predict increasing use of monolithic integration in InP, where the embedded laser becomes one element of an integrated transmission terminal chain, including maybe modulators, detectors and other optical elements. Tunability will be mandatory in such schemes, as will elements in the design to facilitate low cost packaging. Laser operating temperatures will increase, and hence transceiver power will accelerate downward, as new materials (quantum dots, dilute nitrides ...) and designs impact operating temperature, giving high reliability and performance in uncooled applications. Together with the above integration, we will see increasing functionality with low dissipation in very small form factor assemblies, such as XFP.'
Another major application area for photonics has traditionally been defence and security. Dr Iain Howieson, R&D director at Cascade Technologies, believes changes are coming about here too: 'The proliferation of IR surface to aircraft missiles (SAMS), coupled with a rapid growth in international terrorism and increased global political uncertainty, has resulted in a significantly increased missile threat to aircraft. Conventional counter measure techniques, such as RF jammers or decoy flares, are becoming increasingly ineffective against advanced IR seekers. This had led to an alternative approach, commonly referred to as directed infrared countermeasures (DIRCM), to help defeat the threat of in-flight missiles.
'DIRCM techniques work by directing modulated beams of light towards the seeker, which ultimately results in false data reaching the tracking system causing it to veer away from its intended target. Current, state-of-the-art QCL lasers are well suited to such applications. A combination of broad spectral coverage in the 4-5µm region, output powers greater than 0.5W, fast modulation speeds and Gaussian beam characteristics provide significant advantages over incumbent flash lamp technology. The fast pace of development indicates that QCL performance will rapidly outstrip other laser-based solutions, such as diode pump YAG-OPOs, with improvements in key areas such as lasing efficiency, output powers and spectral coverage, while existing advantages such as lifetime, beam quality, low power requirements and reduced cost all indicate that the QCL should rapidly become the source of choice for DIRCM applications.'