By Geoff Giordano

Not only are lasers bridging worlds by offering solutions useful across the macro-, micro- and nanoprocessing spheres, but they are building a better world as vital components in the facilitation of green energy technologies.

From beginning to end, the Laser Institute of America highlighted these themes in a broad-ranging program for the 31^st International Congress on Applications of Lasers & Electro–Optics (ICALEO^®) from Sept. 23-27 in Anaheim. Nearly 500 attendees, including about 40 first-timers, from 33 countries gathered in southern California to take in as many of the more than 200 presentations as they could while interacting with peers and vendors.

LIA Executive Director Peter Baker and President Prof. Reinhart Poprawe presided over another collegial gathering that saw them exchange good-natured gifts to one another at the Wednesday awards luncheon — during which they announced that LIA easily overshot its financial projections for 2012. Earlier in the week, attendees were treated to an exciting president’s reception on Monday at the Marconi Automotive Museum in Tustin. Attendees eagerly shared insights and experiences while being bused to and from the event, where they witnessed a collection of vehicles valued at more than $30 million.

The chief honoree of ICALEO 2012 was Prof. Isamu Miyamoto, who won the Arthur L. Schawlow Award for his body of pioneering work on laser welding and materials processing. While he might have attended solely to enjoy this acknowledgement, Miyamoto instead remained busy to the very last day. Not only did he give presentations on welding characteristics of foturan glass and nondimensional evaluation of nonlinear absorptivity in internal modification of glass, but he also delivered a luncheon keynote titled “Origin and New Wave of Laser Welding” and a closing plenary address surveying operational details among Germany’s laser centers.

“From the scientist’s point of view, ultrashort laser pulse applications are most exciting,” Miyamoto noted while staying after one of his presentations to answer questions and sketch out ideas with an attendee. “I used to be involved in macro processing in the high-power region, (which) is also very interesting, but the most important part has been finished, I think. With short laser pulses there are many problems (to solve); there are a lot of new physics. When I started welding by ultrashort laser pulse, there were many researchers in that field. They did not agree with me because they believed that the ultrashort pulse laser is nonthermal.”

Noting the challenges of understanding the “real physics” of ultrashort pulse lasers, Miyamoto emphasized that more research is needed to help industries embrace applications with those tools. Development in that regard is moving quickly, he says. “For example, at (Fraunhofer) ILT they are developing a 1 kilowatt femtosecond laser. As I mentioned in the award address, the ultrashort pulse process is complicated, but sometimes it’s very simple. If you make the power, pulse or repetition rate double, the performance becomes double. Unfortunately, it’s an expensive area. But I think it’s the most exciting (area of study).”

A WEALTH OF KNOWLEDGE
In his opening remarks, ICALEO General Chair Kunihiko Washio emphasized a program geared more to industry and technology as opposed to last year’s focus on material and nanotech sciences. As he did while serving in the same role in 2011, Washio attended many sessions, often fueling further discussion with his post-presentation queries.

The opening plenary sessions, kicked off by Dr. Thomas Baer, executive director of the Stanford Photonics Research Center at Stanford University, amounted to the firing of a starting gun in researchers’ race to find more efficient means of producing effective alternative energy with laser-based light sources.

Baer, who gave his first ICALEO presentation in 1982 while with Spectra-Physics, asserted that “it’s surprising what a role photonics plays” in renewable power sources including hydro, wind, wave and solar. Noting that he installed 5 kilowatts of solar panels on the roof of his home, and that his Chevrolet Volt contains a 400-pound battery, he asserted that the power to dramatically increase the impact of alternative energy rests in the hands of the laser establishment.

“Part of the challenge we face as a photonics community and material science community is learning how to make good single-crystalline CIGS, or as close as we can get to single-crystalline CIGS — cad-tel and amorphous silicon — rapidly in a reel-to-reel process.” He noted that First Solar “claims that they can take a piece of glass in and 45 minutes later they have it assembled onto a module, which is an amazing feat, and they do indeed have the lowest-cost panels on the market.”

While the silicon market still dominates vis-à-vis thin film, Baer noted the thin-film market is increasing. “We have continued to have innovation in this area largely due to research around the world, and there is still great potential for these technologies to improve. The bottom line is they don’t have to improve much to have commercial impact.”

Using a video of a windmill destroyed by an approaching storm, Baer explained that lasers can have a role not only in a light detection and ranging (LIDAR) system that would sense wind velocity to adjust the pitch of the blades and protect them, but also could add 10 percent efficiency to the unit. Furthermore, lasers can monitor processes associated with consuming fossil resources — for example, within a coal-fired boiler to reduce the amount of unburned or partially burned fuel.

ICALEO emphasized research geared to these areas and more, especially with educational tracks devoted to processing of dissimilar materials, thin-film processing and the use of lasers in energy generation and storage. Among the many highlights:

• Consultant Sami Hendow of Los Altos, CA, showed how using laser pulses of 10 to 30 nanoseconds versus 200 nanoseconds allows thermal diffusion within the material being worked to improve micromachining precision, for example in ITO/silicon scribing. “If you give it some time, you can remove ITO. If you deposit a certain pulse and wait a little bit, you’re allowing for the heat to diffuse into the remainder of the substrate, and that makes it easy for the second pulse to come in and remove the remainder.”

  

• Qiying Chen of the Memorial University of Newfoundland described using femtosecond lasers to structure optical fibers, creating advanced sensing devices such as Fiber Mach-Zehnder Interferometers and long-period gratings.
• Dongsik Kim of POSTECH in South Korea detailed droplet optohydrodynamic processing, in which high-speed cleansing microjets can be created by firing lasers into liquid droplets. This allows for nonthermal micromachining of materials by removing nanoscale metallic or ceramic materials, and can even remove dental hard tissue.
• Ville Hautala of Finland presented the Tampere University of Technology’s work in local laser joining of two types of glass to silicon with a picosecond pulsed fiber laser at a wavelength of 1060 nanometers.
• Kerstin Kowalick of Germany’s Ruhr University Bochum echoed Baer’s advocacy of green research with a comprehensive discourse on the multiple values of lasers in producing thin-film photovoltaics.
• Paul Denney of Lincoln Electric gave an overview of laser additive manufacturing — and a preview of the LAM workshop he’s chairing for LIA in Houston this February. “There’s a lot going on in 3D rapid fabrication, or full functional deposition, whether it’s medical/dental, even aerospace. My point was there is a lot of activity and interest in surface technology — call it 2D-plus if you would. It’s large surfaces (using) thin or moderately thin buildups (of powder or wire), for corrosion protection, wear protection, repair. Some of that’s being driven by energy. We’re drilling deeper, we’re digging up oil sands, and we have to be able to recover that material in an economical fashion.” Laser processing has advantages over other technologies, he says, but it still needs to be faster and cheaper.

  

“The people who came to ICALEO get a lot of benefit out of these papers,” noted Milan Brandt, chair of the dissimilar materials track. “There’s a lot of exchange of information in terms of what research is being done in the U.S., Europe and Asia. The researchers get a picture of where things are and what’s happening in different regions.”

Laser development and research advances “go hand in hand,” he noted. “Maybe five to 10 years ago, the power levels out of fiber lasers were simply not there to be effectively used in any of these applications, so most of the work was done with CO₂ lasers. Now you’ve got developments in fiber lasers and disc lasers, so most of the research that was done with CO₂ has shifted to fiber and disc. Fiber-delivery systems make life so much easier for everybody.”

BUT IS IT PROFITABLE?

Of course, profitability is a driving factor in refining existing technologies and exploring new ones. For example, “I think there’s money to be made in switching to photovoltaics; there’s certainly a lot of incentive,” Baer noted. To that end, LIA invited Dr. Larry Marshall of Southern Cross Ventures in Palo Alto, CA, to give a short course detailing how researchers can think like entrepreneurs.“Reinvent yourself every five years,” Marshall advised. “Technology has a wonderful way of pulling us out of a financial crisis. Many scientists are too smart to be entrepreneurs; stop being so complicated. Put down the technology and think like a customer.”

Marshall, who came to the U.S. from Australia during the 1987 financial crisis, recalled how he created Light Solutions using about 40 credit cards to raise $250,000 to fund the company. They created a shoebox-size solid-state green laser and targeted makers of far larger units for ophthalmology. While their competitor needed a truck to get its laser to a hospital, Light Solutions could FedEx its product to clinics and physicians, tripling the market.

The company’s crowning achievement was a laser that treated retinopathy of prematurity, in which children born more than six weeks prematurely are rendered clinically blind because their retina isn’t formed and excess blood vessels must be “killed” to restore vision. Light Solutions replaced cryotherapy, which was about 60 percent effective, as the standard of care by building an infrared laser at a wavelength capable of penetrating the sclera. The optic system created a large beam to enter the eye without damaging tissue, then focused down inside the eye so the physician could selectively burn excess blood vessels.

But success doesn’t always afford the best lessons. “It’s OK to fail,” Marshall explained. “As an engineer or scientist, we abhor failure. There is no such thing as failure in the entrepreneurial world. You learn infinitely more from something that doesn’t work than you do when you happen to get lucky and find something that does work. It’s very important when you find success to acknowledge that it’s luck. If you acknowledge it’s luck, you’ll stay humble.”

IMPRESSIONS OF ICALEO
While critical research is always at the heart of ICALEO, it is a chance for the global laser community to connect on many levels in ways other conferences might not allow.

One first-time attendee, Prof. Walter Weingaertner, came to engage with industry professionals as he creates a laser institute in Brazil, one in a system of 38 being built under government and industry auspices. Having used lasers for 10 years, he has sent people to Germany to build Brazil’s photonics knowledge base, which has been oriented more toward welding and cutting and needs growth in the optics field. ICALEO is “an excellent opportunity,” he concluded. “I’ve had a lot of very nice experiences at this conference.”

Howon Lee, a post-doctoral researcher from MIT, was another first-time attendee who doesn’t even use lasers in his microfabrication system, but was eager to attend ICALEO to hear how researchers are using spatial light modulators (SLMs). He came “to meet people who are interested in 3D microfabrication, to share common interests and get some feedback from this community. There are a lot of interesting talks.”

One of the sessions Lee attended was Dr. Stuart Edwardson’s discussion of the University of Liverpool’s advances using SLMs to split beams for high-throughput patterning of silicon, titanium and thin-film electrodes on flexible and glass substrates. Edwardson had attended his first ICALEO in 2001.

“It’s getting busier,” he noted. “The quality of presentations is certainly going up, and the breadth of what’s being discussed and presented is increasing. Every time I come here there’s a new component. The latest in laser materials processing is here; it’s one of my favorite conferences.”

To order the highly detailed ICALEO 2012 conference proceedings, visit www.lia.org/store/icaleo. To register for ICALEO 2013 to be held Oct. 6-10 in Miami, stay tuned for updates at www.icaleo.org.

STUDENT AWARD WINNERS
1st Place: 1003: Peter Stritt; University of Stuttgart, Stuttgart, Germany, “New Hot Cracking Criterion for Laser Welding in Close-Edge Position”

2nd Place: N404: Wei Xiong; University of NebraskaLincoln, Lincoln, Nebraska, USA, “Three-Dimensional Micro/Nano-Fabrication by Integration of Additive and Subtractive Femtosecond-Laser Direct Writing Processes”

3rd Place: M1104: Krste Pangovski; University of Cambridge, Cambridge, Great Britain, “Designer Pulses for Precise Machining of Silicon – A Step Towards Photonic Compositions”