Recently by Susan Curtis

By Susan Curtis, publisher, Optics & Laser Europe and optics.org

It's not every day you get to meet the inventor of the iconic CO₂ industrial laser, so I was delighted to catch up with C Kumar Patel at the Pranalytica booth in the South Hall extension. Patel, who was awarded the US National Medal of Science back in 1996 for his invention of the CO₂ laser, is now chairman and CEO of Pranalytica, a company formed in 2000 to develop and commercialize high-power quantum cascade lasers for applications in spectroscopy and infrared countermeasures.

The latest release from Pranalytica is a 2 W continuous wave QCL that operates at room temperature and emits at 4.6 µm. "It's the highest power QCL currently available on the market," claimed Patel - who demonstrated by using the laser to burn a hole in his business card. The turn-key laser system is intended particularly for countermeasures systems in commercial and military aircraft, where higher powers are crucial to make laser-based systems effective over longer distances.

The newest version of the laser delivers double the output power of the previous incarnation, but maintains the same nearly diffraction-limited beam quality at potentially a lower cost per watt. Several thousands hours of lab testing testifies to the system's long-term reliability, while the package is hermetically sealed for use in adverse environments. As well as infrared countermeasures, Patel said that the 2 W system could also benefit LIDAR and free-space optical communications systems.

By Susan Curtis, publisher, Optics & Laser Europe magazine and optics.org

The economic downturn is making it even harder for start-up firms to raise investor cash, which makes it all the more impressive that Mobius Photonics has just closed a new round of financing worth some $20m. "It's been a very up and down process, but we now have enough backing to expand and to take us through our next development phase," said Laura Smoliar, CEO and founder of Mobius Photonics, when I spoke to her on the show floor.

At the heart of Mobius is a team of industry veterans from Quanta Ray and Lightwave Electronics, who are now putting their efforts into the development of high-power fibre-based lasers. The latest commercial release is an air-cooled laser system that delivers an average power of 10 W in the ultraviolet, and in a research paper presented at the conference the company demonstrated power scalability to 30 W at UV wavelengths.

Smoliar claims that the fibre-based system enables much greater flexibility than diode-pumped solid-state lasers in terms of output wavelength, pulse width and pulse timing. The same commercial system can produce 10 W in the UV, 18 W in green, and 30 W in the infrared, and offers independent control of the pulse repetition frequency (>200 kHz) and the pulse width (down to 2 ns) without any effect on the laser output.

The G1+ laser system is based on a pulsed master-oscillator, fiber-power-amplifier (MOFPA) architecture. A source module contains the master oscillator and a pre-amp, while a separate diode-based pump module powers the optical head.

According to Smoliar, the fibre-based system was developed with the microelectronics market in mind, and Mobius has patented a system architecture that enables high-throughput parallel processing for volume applications. In this case, a single source module is used to drive multiple pumps and optical outputs.

Given the current downturn in the semiconductor market, Mobius is keen to develop new applications for its innovative system. Target areas include supercontinuum generation, Ti:sapphire pumping, and medical therapy and manufacturing. Smoliar would be delighted to hear from any optics.org readers who have other potential applications for the system.

By Susan Curtis, publisher, Optics & Laser Europe and optics.org

Thursday 08.00 PT: Judging from the buzz at Texas Instruments' booth today, the company's latest DLP development kit for picoprojector applications is proving a hit with the Photonics West punters. TI is well known for its DLP optical switching technology, which uses an array of micromirrors to manipulate light emission, and its development kits allow scientists and engineers to incorporate the technology into their own optical systems.

According to TI's Arun Chhabra, the introduction of the development kits has driven the development of a whole new range of industrial and medical applications. DLP technology was originally conceived for use in displays, and indeed more than 18 million chipsets have been built into projector displays, digital cinema solutions and high-definition televisions. But photonics engineers have also been able to exploit the development kits to create systems for metrology, spectroscopy, and direct-image lithography - to name but a few.

The latest iteration of the development kit targets the emerging market of picoprojectors, which are designed to be so small that they can be integrated into mobile phones and other handheld devices. The development kit incorporates a miniaturized version of the DLP chipset, with the complete kit measuring just 44.8x67.4x14.2 mm - about the size of a mobile phone.

The PicoProjector kit includes a red, green and blue LED, which together produce full-colour output with a brightness of 7 lm. It has also been designed to interface with BeagleBoard, an off-the-shelf processing platform that has become popular within the development community.

Chhabra says the PicoProjector developer kit currently retails for $349, while the BeagleBoard platform cost an extra $149. At that price point, he believes that developers will be keen to experiment with the capabilities of the miniaturized chipset, which in turn will lead to a whole new set of applications that haven't yet been considered.

By Susan Curtis, publisher, Optics & Laser Europe magazine and optics.org

Tuesday 22.00 PT: Can you name a photonics company that has seen its revenues double in the last 12 months? BaySpec, exhibiting at booth #6355, claims to have achieved just that stellar performance by repurposing technology developed for the telecoms market for applications in near-infrared spectroscopy and optical coherence tomography.

BaySpec's Eric Bergles told me that the company's expertise originated in advanced modules for optical communications networks, notably optical channel monitors and erbium-doped fibre amplifiers for dense wavelength-division multiplexing (DWDM) systems. BaySpec still manufactures those modules, but is now also exploiting the same high-volume production processes to deliver low-cost spectral engines that offer the repeatability and reliability expected of commercial telecoms components.

One example is the company's near-infrared spectrometer, which Bergles claims is "an affordable, accurate and ruggedized Raman spectral device". The spectrometer exploits an all solid-state design: a transmissive volume phase grating is used to spectrally disperse the signal, and the diffracted field is then focused onto a highly sensitive InGaAs detector array.

With its compact footprint and price point of around $6000, Bergles believes that BaySpec's NIR spectrometer is a truly disruptive technology. And, given the number of people stopping at BaySpec's booth today, it seems that he may be right.

By Susan Curtis, Publisher, Optics & Laser Europe magazine and optics.org

Monday 17.00 PT: The opening session at today's Laser & Photonics Marketplace Seminar left delegates in no doubt that the global economic crisis is now having a major impact on laser manufacturers. Before presenting his 2009 forecast, Steve Anderson, editor-in-chief of Laser Focus World, warned delegates that "there are a few bright spots, but there's more red ink than black".

What followed was unremitting bad news for laser makers. Anderson forecasts sharp declines for laser sales into both materials processing and optical storage applications, which together account for 55% of the total laser market. Telecoms will also be hit, but to a lesser extent than consumer-driven markets because investment in optical networks is still needed to support increased bandwidth demand.

Overall, Anderson predicts that revenues in the laser market will fall by 11% year-on-year, down from $7.12bn in 2008 to $6.33bn in 2009. But, given the events of the past couple of months, he cautioned that even that forecast could be optimistic.

Even more dismal is the outlook for manufacturers of industrial laser systems. David Belforte, editor-in-chief of Industrial Laser Solutions, acknowledged that his forecast, which was prepared back in November, has been rendered obsolete by recent events. His original predictions suggested that sales of industrial laser systems would fall by 6% in 2009, but he said that the market had seen a "precipitous decline" since the beginning of December. As a result, he now thinks that industrial laser makers will see revenues drop by 15% and "even up to 30% for some suppliers".

So far, so depressing. But Anderson highlighted a few areas where laser makers could expect some stability, if not outright growth. He expects sales of lasers for scientific R&D to remain flat at $181m, with extra funding expected for projects in clean energy, including photovoltaics and fusion reactors, as well as in sensors and bioimaging applications. Defence and security is viewed as another stable market, while Anderson also predicts that instrumentation and projection displays will hold steady.

And both Anderson and Belforte stressed that the market declines they are predicting have largely been caused by the global economic downturn, not any inherent weakness in the laser market.

"Lasers are an established technology, and no other technology exists to compete with them in the markets they serve," claimed Belforte. As a result, both Belforte and Anderson believe that the laser market will be quick to recover as and when market conditions improve. Belforte wouldn't be drawn on when that might happen, but let's all hope that it's sooner rather than later.

UPDATE Monday 1900 PT: While the forecasts spoke to the fear and corrosive pessimism mentioned by Joe McEntee in his entry Fear versus pragmatism, my conversations with other delegates revealed a greater tendency towards pragmatism and new opportunities. Companies developing innovative technologies for well defined markets seem more confident about the prospects for 2009, while Michael Lebby of the Optoelectronics Industry Development Association predicted that the market will rebound in 2010, if not later in 2009. Lebby urged optics companies to use 2009 as a time to focus on developing new technologies that could gain market traction in 2010, and believes that green photonics in particular will become a major market driver.

By Susan Curtis, Publisher, Optics&Laser Europe magazine and optics.org

Photonics West is often viewed as a barometer of the optics industry, and this year all eyes will be on the San Jose Convention Center to see how the wider economic gloom is affecting the photonics sector. As ever, the optics.org editorial team will be reporting directly from the show floor, and we'll be finding out first-hand how exhibitors are coping with the sudden decline in the global economy.

We'll be kicking off the blog in earnest at the weekend, when the BiOS conference and exhibition will be offering delegates a unique insight into the use of photonics in biology and medicine. After that, remember to check back here for regular postings from our editors at the main Photonics West event. Bookmark this page now.

If you're at the show, make sure you visit the optics.org team at booth 1437. As an added incentive, this year we will be hosting the Optics Golf Challenge, a game of skill in which players must try to putt three holes in one. The highest scorers each day will have the chance to win a bottle of whisky, the title of "Optics Champion" and the respect of their peers. We hope to see you there.

I wasn't at CLEO for the last day, but optics.org publisher Claire Bedrock was. There was one particular talk that caught her eye:

"For those who stayed for the final day of the conference there was a fascinating day-long symposium on hollow-core photonic crystal fibre. The final talk of the day created a particular buzz, when Brian Mangan of Crystal Fibre of Denmark presented some new results obtained in a collaboration with the Technical University of Denmark.

First up was a fibre with an antiresonant core, which achieved an attenuation of 9.3 dB/km ‐ a new record for this type of seven-cell fibre). Then Mangan presented results for two high-birefringence fibres, one with an air-fill factor of 91% and the other with a lower air-fill factor of 85%. The latter produced an impressive attenuation of 19 dB/km.

When questioned at the end about the future of photonic crystal fibre. Mangan replied that 'there are loads of talented guys in the field and I'm sure we'll find a solution to the limitations'. This seemed an appropriate note on which to end not only a fascinating symposium but an exciting conference."

In Thursday's post-deadline session, Liang Dong of fibre laser specialist IMRA showcased a new class of fibre that supports singlemode operation for fiber laser applications requiring high peak powers. According to Dong, the new all-glass fibre will extend the reach of practical ultrafast amplifiers to millijoule pulse energies, and could also lead to continuous-wave fibre lasers and amplifiers in the 10 kW range.

Dong explained that high peak powers requires singlemode operation to be achieved in a fibre with a large effective area. He pointed out that today's large-mode area fibres are limited to a core diameter of 30 µm, while photonic crystal fibres have been demonstrated with diameters of up to 100 µm.

Those figures make it even more impressive that IMRA has achieved singlemode operation in fibres with core diameters of up to 170 µm. The fibres exploit the company's "leakage channel fibre" (LCF) design, in which the core of the fibre is formed by six low-index features arranged in a hexagonal grid. Unlike photonic crystal fibre, in LCF the air holes are filled with flourine-doped silica glass, and so it can be cleaved, spliced and handled in the same way as normal optical fibre.

Versions of the fibre with core diameters of 100 µm and 170 µm were designed as passive LCFs. The 100 µm version achieves a pump absorption of more than 25 dB/m &ndash which Dong says would mean that a typical amplifier could be just tens of centimetres long – while LCFs with larger diameters could yield even shorter amplifiers.

A ytterbium-doped LCF was also fabricated with a core diameter of 50 µm. A single-stage amplifier constructed from this fibre achieved pulse energies of 600 µJ for a pulse length of 600 ps and a repetition rate of 25 kHz, which Dong says shows that "the design is a practical choice for extending the peak power in fibre lasers".

Keen-eyed delegates may have been intrigued by the signage for PhotonXpo scattered around the CLEO exhibit hall.

Well, all was revealed this morning: it's part of a rebranding exercise for the CLEO technical exhibit. "The goal is to provide the exhibit with its own identity," Colleen Morrison, the OSA's director for for public relations, told me today. "It has continued to expand, and we wanted a name that would better reflect what's out there on the show floor."

This year's CLEO attracted 320 exhibitors, but the organizers hope that renaming the event will increase numbers at the 2009 event in Baltimore, Maryland.

And that's it from me for now. I'm off to the airport for the red-eye flight to London, but look out in the next couple of days for a couple of post-deadline posts.

The growing interest in commercial photovoltaic sources was apparent at Wednesday afternoon's PhAST session. A full conference room heard Craig Cruikshank of cintelliq, a UK consultancy specializing in organic semiconductors, explain how increased research funding into organic photovoltaics (OPVs) would lead to increased efficiencies and lifetimes, but that the real challenge will be to manufacture devices in high volume and at low cost.

For the moment, he said, the efficiency of OPVs is limited to around 5%, but manufacturers such as Konarka have claimed that improved materials and device architectures will increase that figure to 20% by 2015 – which is comparable to that of silicon solar cells. But he said that widespread adoption of OPVs would not happen until the cost per watt approaches that of conventional power generation systems.

That theme was picked up by James Dietz of Plextronics, a US-based manufacturer of OPV materials. He said that falling prices for OPV systems, combined with rapidly increasing rates for electricity producing using conventional means, would enable OPVs to reach grid parity in around 2015. "Analysts predict that demand for OPVs will outstrip supply once grid parity is reached," he said.

In the meantime, said Dietz, OPVs will be limited to niche applications. One key market lies in micro-powered consumer devices, for example to reduce the battery power required in toys and handheld devices. OPVs are particularly suited to this type of power scavenging application, since they maintain good efficiency at low light levels – such as you might find indoors.

Finally, both Dietz and Cruikshank issued a warning about the accuracy of efficiency and lifetime measurements claimed by OPV manufacturers. The methodology for taking these measurements has not yet been standardized, which can lead to some misleading figures. According to Dietz, Plextronics and other companies are now working with the National Renewable Energy Laboratory (NREL) – which currently runs a certification programme for OPV measurements – to define future standards.

At Wednesday's plenary session, the OSA recognized the achievements of key optical scientists and engineers in its annual awards ceremony.

A popular winner was Ursula Keller of ETH Zurich, who was presented the Joseph Fraunhofer award for her work on ultrafast lasers, notably semiconductor saturable absorber modelocking. We have already reported on Keller's latest research into integrated modelocked VECSELs, and she clearly felt honoured to receive such an award. She pointed out that her two sons, aged 9 and 11, were in the audience "to see why Mommy is away all the time".

In her acceptance speech, Keller urged women scientists to continue to do good science, but also to remember to have a family. "You can do it," she said. "It may be tough at times, but you just need to try harder."

Other winners were:

* Eric Mazur of Harvard University was awarded the Esther Hoffman Beller Medal, which is presented for contributions to optics education. Mazur won the award for developing a teaching methodology known as "peer instruction", which promotes deeper understanding of the fundamentals of science.

* Kam Y Lau, professor emeritus at the University of California, Berkeley, was awarded the Nick Holonak Jr. Award for his work on high-speed direct modulation of semiconductor lasers through enhanced differential gain.

* Robert R Alfano of the City College of New York won the Charles H Townes award for his contributions to the discovery and investigation of supercontinuum sources, and the development of tetravalent chromium-based tunable solid-state lasers. By a happy coincidence, Alfano also celebrated his birthday today.

Finally, the 2008 Student Award, which is sponsored by New Focus, was decided on Tuesday night in a competition between seven finalists. Each finalist presented a research paper to a panel of judges, as well as to a "live" audience, and the winner was Richard Sandberg of JILA and the University of Colorado at Boulder. Sandberg receives $5000 as part of his award, while the runners up each receive $1500.

One of the most eye catching displays at this year's CLEO exhibit can be found on Paradigm Lasers' booth. Its o-Tool product offers a simple visual display that allows users to quickly and easily assess the light output from a laser source. It can be used by scientists to instantly visualize the output intensity from their light source, and by educators to demonstrate the concept of polarization.

Company president Tim Irwin told me that the o-Tool provides the same ease-of-use for optical systems as a multimeter provides for electronic systems. "Full characterization of an electrical system requires an oscilloscope, but all labs have a multimeter to quickly measure voltage and current levels," he said.

Before use, the o-Tool just needs to be plugged in and energized by shining a light at a side hole. Directing a laser at the centre of the instrument then generates a response that depends on its intensity, and an optional infrared attachment makes it possible to "see" the output from an IR source.

An additional polarization plate makes it possible to visualize the direction and intensity of a polarized light source. Irwin believes this could be a real winner in a teaching environment, since it would allow students to see the effect of waveplates and polarizing sheets on the laser output. With the basic instrument retailing for around $225, it could be a worthwhile investment.

At the CLEO exhibit today, Paul Morris of Gooch & Housego gave me a sneak preview of a prototype fibre Q-switch that is significantly smaller than an earlier device that delivers similar performance (see picture). According to Morris, the innovative device is a direct result of the integrated strategy that Gooch & Housego unveiled back in January.

The fibre Q-switch is designed to boost the output of pulsed fibre lasers operating in the 20–40 W range. According to Morris, the small size of the device was achieved in part by reducing the size of the crystal, drawing on the expertise of the company's main site in Ilminster, UK. But it also exploits fibre packaging know-how acquired from the former SIFAM business in Torquay, UK, to efficiently couple light into the crystal and so eliminates the need for bulk optics to achieve good alignment.

Morris said that Gooch & Housego is currently previewing the device to key customers in the fibre laser space. A formal launch is scheduled for Q3 – at which time a full technical spec will be released – while manufacturing of the device is slated to start by the end of the year.

The size of the market for such a fibre Q-switch is not yet clear. Manufacturers of fibre lasers either use fibre amplifiers or Q-switches to achieve pulsed operation at high powers, depending on the performance parameters needed for each application. Morris believes that the compact size of the fibre Q-switch will prove popular, while power levels below 50 W represent a sweet spot for fibre lasers to displace conventional Q-switched lasers in marking applications.

Also in the pipeline is a scalable fibre isolator technology. Isolators are needed in all fibre lasers to prevent reflected laser light from damaging the pump laser diode, but currently they are fabricated one at a time in a lab-based environment. Gooch & Housego is now working on a fibre isolator that would allow for higher throughputs, and Morris said that formal announcements are likely to be made towards the end of this year, or early in 2009 – no doubt in time for next year's Photonics West.

All-optical data processing at ultrafast speeds is the goal of researchers at Sandia National Laboratories in Alberquerque, New Mexico. In today's conference session on high-speed components, Sandia's Gordon Keeler said that the initial aim is to develop a chip-based optical platform that can perform logic operations at speeds of up to 40 GHz, but that the longer term goal is to achieve processing speeds of 100 GHz and beyond.

The critical technology in the Sandia team's research is a self-electrooptic effect device, or SEED for short. SEEDs, which were invented 25 years ago by David Miller at Bell Labs, operate as both a modulator and a high-speed photodetector. Crucially, when two of these devices are put together to form a symmetric SEED (S-SEED), they operate as a bistable device that can be switched by an optical pump.

This means that S-SEEDs can be exploited as all-optical logic gates, in particular to perform both NAND and NOR operations. And, according to Keeler, more complex logic circuits can be realized by cascading several S-SEEDs together using micro-optics.

Earlier work at Sandia demonstrated fast switching times for S-SEEDs fabricated in AlGaAs that operate at 865 nm. Now, however, the team has developed devices in a different material system that deliver similar performance at the more useful telecom wavelength of 1550 nm.

The telecom-compatible S-SEEDs are made from InAlGaAs quantum well structures grown on InP substrates. According to Keeler, the quantum wells are made shallow enough that a few picojoules of energy from a modelocked fibre laser is sufficient to switch the state of the logic gate.

Using this scheme, Keeler and his Sandia colleagues have demonstrated switching times at 1550 nm of down to 5.5 ps, which should yield an operating frequency of 40 GHz. Simulations suggest that all-optical switching in this system shouldbe possible at speeds of up to 100 GHz, but will ultimately be limited by the carrier dynamics in the system.

An intriguing notion was presented this afternoon by Max Shtein of the University of Michigan. Rather than fabricating organic light-emitting diodes as discrete planar devices, Shtein has shown how organic emitters can be formed on 3D structures such as cylindrical fibres and micron-scale cantilevers for use in atomic force microscopy (AFM).

Once you think about it, the idea is obvious: organic materials have been fêted for their flexible nature, and the weak van der Waals forces that bind organic molecules together are weak enough for the organic layers that make up an OLED to conform to non-planar substrates.

The problem, says Shtein, is the need in conventional OLED structures for transparent electrodes. Indium tin oxide (ITO) is the usual choice, but remains an expensive option for large-area deposition. And ceramic materials that also combine optical transparency with good electrical conductivity must be deposited at high temperature – which increases the fabrication cost – and are too brittle to be used on curved substrates.

The solution for Shtein and his team is to replace the transparent electrodes either side of the organic layers with thin metal films. Tests on a planar metal–organic–metal (MOM) structure emit light efficiently, but the spectral content varies with viewing angle. In contrast, forming the MOM structure on a cylindrical fibre substrate yields uniform colour output at all viewing angles.

More intriguing still is the idea of depositing OLED structures onto an AFM tip. This enables localized current injection at the vertex of the tip – largely because the sharpness of the tip concentrates the electric field and so increases the current density – which leads to controlled light emission at the vertex of the tip.

What's more, says Shtein, the fabrication process is scalable, and so could allow OLED structures to be deposited onto an array of AFM tips in a single process run. "The ability to fabricate nanoscale light sources on commercial AFM cantilevers could enable new applications in high-resolution optical scanning microscopy, as well as nanoscale optical and chemical sensing," he said.

The first fibre-based laser to deliver picosecond pulses at high average power levels took pride of place when I visited Coherent's booth this morning. According to Matthias Schulze, Coherent's director for product marketing, the Talisker laser is targeted at industrial micromachining applications where high precision and high throughput are critical for success.

Schulze told me that nanosecond Q-switched lasers operating at ultraviolet wavelengths have become the industry standard for machining materials such as silicon at the micron scale. But he says that in some cases the Talisker laser could offer the same performance at infrared wavelengths, which would eliminate the need for costly UV beam delivery systems.

Indeed, the Talisker laser can switch operation between three wavelengths. UV output at 355 nm enables ultraprecise machining with an average power output of 4 W, while the laser can also produce visible output at 532 nm and infrared at 1064 nm – in which case the average power output rises to 18 W. In each case, the pulse repetition rate is 200 kHz, which equates to a pulse width of less than 15 ps.

According to Schulze, this flexibility will allow customers to evaluate which wavelength works best for their particular application. "If infrared picosecond pulses provide the same precision as a UV nanosecond laser, Talisker would make it possible to increase throughput and lower the system cost without compromising on precision," said Schulze.

According the Schulze, the combination of ultrafast operation and high output power Talisker is only possible with a hybrid design. A fibre-based laser oscillator provides a stable and robust source of picosecond pulses, while a free-space amplifier boosts the peak power to levels some ten times greater than is possible with a fibre laser on its own.

Schulze says that the laser could be used for micromachining applications in the microelectronics, biomedical, and solar cell industries, and that customers are currently evaluating its use with a range of materials. He also mentioned that Talisker is just the first in a series of fibre-based products that Coherent will be launching to address materials processing applications at the micron scale.

* Also new for CLEO, and aimed more at the research community, are two new ultrafast amplifiers that now offer pulse widths of less that 25 fs. The Legend Elite USX-HE offers pulse energies of more than 2.5 mJ, while the Duo-USX model delivers pulse energies in excess of 5 mJ.

According to Marco Arrigoni, director of marketing for Coherent's scientific business, this is the first amplifier to achieve such short pulse widths – which are needed in research applications such as ultrafast spectroscopy, high-harmonic generation, and attosecond physics. This performance is achieved by a regenerative amplifier module combined with Coherent's BandMax technology, which ensures stable short-pulse generation.

According to Phil Wright of the Optoelectronics Industry Development Association (OIDA), sales of commercial OLED lighting products will reach $14 bn by 2020. Speaking at today's PhAST conference, which is held in conjunction with the CLEO exhibit, Wright said that OLED backlights for LCD screens would be the first application to drive widespread market adoption.

"OLEDs will start to displace other backlight technologies by 2010, and it will still be the largest single market for OLEDs in 2020," he said. "Illumination applications will be the second largest market by 2020, followed by automotive and signage."

Wright believes that early adopters of OLEDs for illumination will be lighting engineers who want to make a bold design statement. Otherwise, OLEDs face stiff competition from incumbent technologies, including compact fluorescent bulbs and inorganic LEDs.

Further penetration of OLEDs into the lighting market will require further improvements in luminous efficacy and lifetime, combined with a reduction in manufacturing costs. Wright pointed out that the US Department of Energy predicts that laboratory devices will achieve efficiencies of 150 lm/W by 2012, with the same figure being attained by commercial devices a few years later. Lifetimes are also expected to reach 40,000 hours by 2015, while the cost of production is predicted to fall to $10 per thousand lumens over the same time frame.

A full conference session this afternoon heard Ursula Keller of ETH Zurich describe a new type of ultrafast semiconductor laser called the MIXSEL – which stands for modelocked integrated external-cavity laser. MIXSELs promise to deliver high output powers at repetition rates of 10–100 GHz, parameters that Keller says are needed in biomedical applications, optical clocks for computer processor cores, and telecoms applications.

The MIXSEL design is the culmination of several years' work on passively modelocked vertical external-cavity surface-emitting lasers (VECSELs), which were first demonstrated by Keller's group in 2000. Indeed, the latest modelocked devices achieve an average output power of 2.1 W at pulse durations of less than 500 fs and repetition rates of 50 GHz – which Keller says is competitive with the performance of diode-pumped solid-state lasers.

However, these headline results were obtained from a hybrid structure consisting of the VECSEL gain medium and a separate semiconductor saturable absorber mirror (SESAM), an arrangement that poses problems for high-volume wafer-scale fabrication. Keller's group has therefore been working to integrate the SESAM functionality into a single laser architecture.

The result of these efforts is the MIXSEL structure, which consists of five sections: a distributed Bragg reflector (DBR) that is highly reflective at the laser wavelength of 960 nm; a saturated absorber made from self-assembled InAs quantum dots embedded in GaAs layers; an intermediate DBR for the pump wavelength at 808 nm; the gain section with seven InGaAs quantum wells; and an anti-reflection coating.

Initial results for this structure showed an average output power of 182 mW with a pulse duration of 32 ps when the MIXSEL was cooled to –50°C. In this case, however, the power output was limited by the high thermal impedance of the 600 µm GaAs substrate on which the structure was grown. Further power scaling will be achieved by growing the layers in reverse order (the normal "upside down" approach), which will allow the substrate to be removed using selective etching.

The existing MIXSEL design requires optical pumping, but Keller is confident that electrical pumping should also be possible. Further optimization is also needed to produce shorter pulses, potentially down to the femtosecond range, and this will one of the goals of a new European research project to produce compact ultrafast sources for biomedical applications.

Near-field pattern

At my first CLEO talk of the day, Susumu Yoshimoto and colleagues at Kyoto University in Japan described an electrically pumped GaN laser that emits blue-violet wavelengths at room temperature. The device is the first GaN photonic-crystal surface-emitting laser (PC-SEL) to operate at room temperature under pulsed current injection.

Just a couple of weeks ago, optics.org reported on a GaN VCSEL that achieves electrically pumped lasing at 462 nm. But Yoshimoto claims that the PC-SEL design could deliver powers of up to 1 W – orders of magnitude greater than can be achieved with both GaN VCSELs and photonic-crystal nanolasers – while also producing a narrower and more controllable beam than is possible with edge-emitting devices.

In the PC-SEL design, a two-dimensional photonic structure is created close to the active quantum-well region of the device. The photonic crystal creates a feedback effect that leads to the generation of a 2D cavity mode, and also acts to couple light emission into the vertical direction. Changing the parameters of the photonic crystal also allows the polarization and the beam pattern of the emitted light to be controlled.

This type of operation has already in demonstrated in GaAs-based structures, but fabricating a PC-SEL in GaN proved more difficult. One key problem, said Yoshimoto, is that the distance between the planar photonic crystal and the active region should be about the same as the wavelength of light in the material, which is shorter in GaN than it is in GaAs.

"To obtain the required band-edge effect, the photonic-crystal structure must be constructed within 300 nm of the active layer," said Yoshimoto. "It also requires the fabrication of a high-quality GaN/air periodic structure with a lattice constant of between 100 and 200 nm."

To meet these exacting demands, Yoshimoto's group developed a new fabrication method known as AROG (air holes retained over growth). In this technique, the periodic pattern is first defined in the GaN epitaxial layer using lithography and dry etch processes, and silicon dioxide is then deposited in each air hole. Another GaN layer is then overgrown using molecular-organic vapour phase epitaxy to cap the top of the air holes, while the silicon dioxide prevents GaN growth within the holes. The result is a well defined arrangement of air holes inside the GaN epitaxial layer.

Tests on the GaN PC-SEL revealed light emission at 406.5 nm, with large-area lasing observed in the near field and a narrow (100 µm²) beam forming in the far field. This replicates the single-mode, large-area oscillation that has previously been observed in GaAs structures.

One remaining challenge is that the laser currently requires a large threshold current, at around 6.9 A (67 kA/cm²). Yoshimoto believes that this could be reduced by improving the crystalline quality of the multiple-quantum-well active layer; optimizing the distance between the active layer and photonic; and using a transparent electrode. The target threshold current density for the group is 5.4 kA/cm².

Farmer's market

Most visitors to CLEO from Europe will, like me, have flown on Saturday to get a cheaper airfare. The downside is that you miss a weekend at home (and, for those from the UK, this time it's a holiday weekend), but the upside is that you get an extra day to recover from the flight and the jet lag.

You might wonder what there is to do in downtown San Jose on what has turned out to be a beautiful spring day. Well, so did I.

Luckily for me, a couple of friends recommended that I should stay for the weekend in Los Gatos, a town in the Santa Cruz hills that is only about 15 miles away from San Jose. And I'm glad they did, because Los Gatos is the perfect place to spend a lazy day.

I found plenty of interesting shops to browse in (I particularly liked Powells Sweet Shoppe and Inner Journey, a purveyor of "metaphysical supplies"); a farmer's market with fresh Californian produce that's held every Sunday morning; and great coffee and cake in the Los Gatos Coffee Roasting Company.

There's plenty here for more active types as well. I started my day with a run along the Los Gatos Creek Trail, an off-road track that's clearly popular with walkers, joggers and cyclists. It was certainly enough to give me an appetite for a proper American breakfast.

Tomorrow, of course, I shall be making my way to San Jose for a full day of conference sessions. So enough of my travelog - tomorrow it's back to optics!

Terminal 5

My journey to CLEO started this morning with my first visit to Heathrow's Terminal 5, which opened in March with the aim of easing the chronic congestion at the world's busiest international airport. Sadly, the big opening was dogged by serious baggage handling problems that caused dozens of flights to be cancelled.

Today, thankfully, there was no hint of that earlier chaos. The arrivals hall is light and airy, and seems almost serene – although it's true that the terminal is still only operating at around half of its full capacity. I was even greeted by a calming display of synchronized fountains when I arrived early this morning.

But there were a few telltale signs of those "teething troubles". The fast bag drop wasn't exactly speedy and, although the system for security checks looks high tech, it took just as long as ever to get through. And I'm not sure how well the system will cope when more passengers are going through the doors.

There were other little niggles: the two-level departures area is confusing to navigate, and a simple map of the facilities would have been a big help. And although the restrooms look great – and feature those fab ultrafast hand-drying machines – some of the door locks don't work properly.

T5 fountains

All of these problems will, I'm sure, get sorted out in the coming weeks and months. But there is one big design flaw: although the shops and eateries in the departure area are arranged over two floors, there are no stairs (that I could find) and no "up" escalators – but there are two "down" escalators. Where's the logic in that?

The acid test, of course, is whether the flight left on time. In this case, we boarded the plane on time (well done, T5!), but had to wait 40 minutes for a runway slot. So T5 may well alleviate the congestion in the terminals, but Heathrow's runways are just as busy as ever.

PS. For those who aren't interested in the numerous shopping opportunities that T5 has to offer, I can recommend Gordon Ramsay's café/restaurant "Plane Food" as a peaceful haven with an outside view (nice planes!)

Web usage is a fascinating thing. A quick look at the optics.org visitor stats revealed that almost 50,000 people have viewed one specific article in the last month. Which article had piqued the interest of so many readers? Well, it wasn't a recent news item, but an article about an optical lock that we published back in 2004 (see Optical lock foils thieves).

Further research revealed that the article had been picked up by StumbleUpon, a website that claims to "find great websites, videos, photos and more based on your interests". It's strange to think that 22 people (at the time I wrote this) felt moved to comment on work that is now at least four years old, but for the record most respondents were skeptical that it would work in practice. Click here for the full "discussion".

As Photonics West winds up for another year, Jacqueline and I are heading to the airport for the night flight to London. As ever, it's been a blast: we've been impressed by the sheer size of the show, and by the truly innovative products that have been on display at many of the booths.

You can read all about our highlights of the show in the blog entries below. So it's goodbye for now, and see you all again next year.

This morning's executive panel focused on the realities of doing business in China. Adonis Mak of Laser Focus World China, which is published out of Hong Kong, highlighted the opportunity for companies in the West to supply laser products to scientific research institutes in China.

"All colleges in China have physics and optics departments," he said, "and in many cases they have abundant budgets to buy high-end devices and equipment."

Within the industrial sector, Mak identified four key markets in China that rely on laser technology: consumer electronics, car production, semiconductor manufacture, and optical communications. Car manufacturing and to some extent semiconductor fabrication have benefited from inward investment from leading overseas firms, while China is now the largest manufacturer of consumer electronics in the world.

Laser manufacturers have not been slow to recognize this opportunity. Newport-Spectra Physics established a presence in China 25 years ago, while Coherent has been in the country for the past decade. More recent arrivals have been big hitters such as Edmund Optics, IPG Photonics, Dilas and Ocean Optics.

But Mak acknowledged that many challenges remain for Western firms. "Guan-zi [relationships] still play an important role when doing business in China, which means that you need a local partner," he said. "Most research institutes are also controlled by the government, and that can make buying behaviours difficult to predict."

Robert Huang of Wavelength Technology (booth 6247), a company based in Singapore that established a Chinese facility in 2003, highlighted the problems associated with IP piracy. When asked how companies should protect their intellectual property, he said: "You've got to be fast so that no-one has a chance to copy you."

But Huang said that photonics firms should not be scared to invest in China. "The technology and quality of Western suppliers is welcome in China, but price is also a key issue."

We've heard a lot this week about photovoltaics, and in particular about the role that lasers have to play in their fabrication. At the Lasers and Photonics Marketplace Seminar on Monday, Newport's Dave Clark explained how laser scribing is an essential technology for the manufacture of emerging thin-film solar cells, while a visit to the Coherent booth on Tuesday revealed that this company also sees big potential in the photovoltaic market.

So it was interesting when yesterday's executive panel debated whether photovoltaics offer a real opportunity for laser manufacturers, or whether it's all just a chimera. Moderator Steve Eglash pointed out that the solar market is currently worth $15 bn worldwide, and that the solar sector has already seen a number of successful IPOs. He himself has "voted with his feet", being CEO of solar start-up Cyrium Technologies.

Others were more cautious. Newport's director for strategic marketing, Randy Hyler, clearly sees an opportunity for laser makers, but believes it will be a long-term play. Certainly, lasers aren't crucial for the manufacture of silicon solar cells, which continue the dominate the market, which means that companies such as Newport might need to wait until thin-film versions become more popular.

Hyler also pointed out that 99% of solar cell deployments have so far been in Japan and Germany, where government rebates have made the finances look more attractive. The danger, he says, is that demand will fall away once these programs have run their course.

Meanwhile, Stuart Schoenmann, CEO of CVI Melles Griot, says that he is "still evaluating" the market opportunity. Interestingly, CVI Melles Griot is based in Albuquerque, New Mexico, where Schott is currently building a solar factory.

Perhaps the most sceptical was Trumpf's Holger Schlueter, who referred to the rush for photovoltaics as a "solar craze". He also maintains that there's no point investing in renewable energy sources without stable power grids and storage.

New on the Ophir-Spiricon booth was its wireless interface for its laser measurement system that exploits Bluetooth technology - which company president Gary Wagner told me is an industry first. In a live demonstration of the Quasar system, a laser energy meter was positioned close a light source on one end of the booth, and the smart heads and computer were located at the other end. The graphical display clearly showed the 60 Hz oscillations in the mains-driven light output.

Wagner explained that the laser meter data can be broadcast to any PC or laptop within 10 m. He says that the system not only avoids the need for lots of cables, but is also particularly suitable for applications in a tight space - such as high-power lasers that are hidden behind barriers.

Quasar is compatible most Ophir smart heads, including thermopile,
photodiode and pyroelectric versions. An optional antenna can also extend
the wireless range of up to 60 m. "Combining wireless technology with laser power/energy measurements is an enabling technology," said Wagner.

A new way to dramatically speed up the electromagnetic simulation of CMOS image sensors was being demonstrated today on the Synopsys booth. In one example cited by Ric Borges, Synopsys' technical marketing manager, the simulation time was reduced from more than 13 hours to just 22 minutes.

The key to this step-change in performance is hardware acceleration technology developed by Acceleware, a developer of high-performance computing applications. According to Ryan Schneider, the company's CTO, Acceleware's approach is to exploit the computing power of graphics processing units (GPUs) to deliver significantly more processing power in a deskside unit.

The solution developed by the two companies exploits Acceleware's ClusterInABox Quad Q30 workstation, which comprises a workstation plus two accelerator deskside units to deliver up to two Teraflops of computational power. This has been combined with Synopsys' device simulation software, known as Sentaurus, that exploits a finite-difference time-domain algorithm to model in 3D the behaviour of light within a CMOS image sensor.

According to Borges, designers of image sensors are increasingly turning to computer simulation to optimize performance before fabrication. With the move to 200 mm and 300 mm wafers, he says, a company could spend tens of thousands of dollars on a single trial run.

Normally, device engineers simulate the transmission of light through a single pixel, and then use those results to improve device performance. It's also crucial to model the behaviour of a small array of pixels to check for cross talk, but the computing overhead makes that prohibitive except as a very final check.

Now, says Borges, engineers can get the results from these larger simulations in a fraction of the time, which means that cross-talk issues can be identified much earlier in the design process. In the highly competitive optoelectronics sector, where speed-to-market is crucial, Synopys and Acceleware believe they are onto a winner.

The world's fastest CMOS-based digital camera was on show at the Vision Research booth today. The Phantom V12 can record up to one million frames per second, but Paul Laureano, director of international sales, told me not to get too hung up on this headline figure. More important is the combination of high resolution and high speed that can be achieved at around 40,000-50,000 frames per second.

At the heart of the camera is a 1280x800 high-definition CMOS sensor that has been optimized for high-speed imaging applications. The resolution that can be achieved depends on the frame rate: at full resolution the camera can record 6315 frames per second, while at the maximum speed the resolution falls to 256x8.

The light sensitivity of the camera has been optimized by combining an active pixel size of 20 µm with improved quantum well efficiency, while a shutter speed of down to 300 ns eliminates blur and accentuates detail.

According to Laureano, Vision Research was the first company to introduce CMOS image sensors into high-speed cameras, and the Phantom V12 is the result of the company's engineering expertise in this area. The camera is designed for recording extraordinarily fast events, specifically ballistics and explosions testing, and those that take place at the microscopic level.

This morning we learned from Eugene Arthurs, SPIE's executive director, that Photonics West will be held in San Francisco's Moscone Center in 2010. The reason is clear: the San Jose Convention Center is no longer able to cater for the growing number of exhibitors and delegates who visit the show every year.

Indeed, for the first time this year the show organizers could not accommodate all the exhibitors in the Main Hall and the South Hall, itself a semi-permanent extension to the main convention center. An extra tent has had to be added onto one end of the South Hall, which is reported to leak when it rains.

Arthurs says that plans had been in the pipeline to extend the McEnery Convention Center, but the city had been unable to afford the work in the wake of the telecoms downturn. As a result, SPIE has taken the decision to host the event in the larger facility in San Francisco.

But, he says, don't make the mistake of booking your tickets to San Francisco next year. Photonics West 2009 will be back at the San Jose Convention Center just one more time.

"This is a completely new class of materials that could really change the field of optoelectronics," asserted Fred Schubert of the Rensselaer Polytechnic Institute (RPI), speaking at one of the technical sessions this afternoon. He was referring to the emergence of low refractive index materials that he believes can deliver big improvements in the efficiency of optoelectronic devices such as LEDs and solar cells.

So what is a low refractive index material? Schubert points out that no natural solid materials have a refractive index lower than about 1.4 - silica comes in 1.46, while the more exotic magnesium fluoride has a refractive index of 1.39. And yet the performance of many optical components depend on changes in refractive index, and increasing the difference in refractive index improves some of the most important figures of merit.

Schubert and colleagues at the RPI have now demonstrated that materials with a refractive index of down to 1.05 can be fabricated using a process called oblique-angle evaporation. This process has been shown to produce a self-organized array of nanorods, with the pores between individual nanorods measuring 2-8 nm - much smaller than the wavelength of light. As a result, the surface morphology of the nanorod layer is completely smooth and featureless.

What's more, the refractive index of the nanorod thin film can be controlled by altering the angle at which the rods are deposited. Larger angles produce a more porous structure, which in turn has a lower refractive index, while smaller angles result in denser layers that have a higher refractive index.

This tunability has been exploited by Schubert's team to fabricate graded refractive-index layers that act as almost perfect antireflective coatings. He explained that reflectivity depends on the change in refractive index between two materials, which means that reflections can be minimized by changing the refractive index in a series of small steps.

Results presented by Schubert show that graded coatings can reduce reflectivity to less than 0.5% over a wavelength range of 570-1000 nm. And incorporating these antireflective layers into LEDs - which are typically made from semiconductors with high refractive indices - has also been shown to increase light output by more than 40%. And Schubert believes that low refractive index material could also improve the performance of optical sensors, solar cells and other optical components.