Applications growing for mid-IR lasers

Caren B. Les, caren.les@photonics.com

New military and sensing applications are expected to drive the mid-IR laser market in the next few years. These new segments will grow approximately 30 percent per year, compounded annually through 2014, according to a report titled Mid-Infrared Lasers 2010 from Strategies Unlimited.

The report, published in September 2010, examines the spectrum region from ~1.8 to ~15 μm.

“What is new is the use of new types of lasers for military applications, followed by a wide array of sensing applications, from industrial process controls and environmental monitors to hazardous chemical detection and new medical diagnostics,” said Dr. Tom Hausken, director of photonics and compound semiconductors at Strategies Unlimited.

“The most obvious new [technological] development is in compactness and robustness,” he added, noting that these more compact products enable more mobile platforms and installation into industrial processes. Semiconductor lasers, optically pumped semiconductor lasers and optical parametric oscillators (OPOs) are now more compact and robust. The new technology is much improved over gas lasers, lamp-pumped solid-state lasers and OPOs designed for scientific purposes, he said.

Currently, in the mid-IR range, CO₂ and solid-state lasers dominate in materials processing and medical treatment applications, respectively. “The challenge is to get the cost of the new technologies to the level suitable to the target application, which is often near the level of an existing, very inexpensive technology,” Hausken said. “Here the semiconductor laser technologies have the most promise, but you cannot assume that they can scale easily or quickly to high volume and low cost. And, anyway, they aren’t the best fit for every application.”

Imagine a Breathalyzer that can determine whether you have or don’t have a certain medical condition, Hausken said.

“Knowing this at the time of a doctor or hospital visit might save a costly and time-consuming test or an expensive treatment,” he said. “The list of these potential solutions is long.”

“Likewise, imagine that you can place small sensors all over an industrial plant, or a city, and monitor for environmental hazards or different types of CO₂ emissions. These are just the more dramatic applications. There are many more.”

In the military segment, mid-IR lasers are used as countermeasures against heat-seeking missiles. The more advanced missiles are wise to last-generation countermeasures, so the countermeasures must become smarter than the missiles, Hausken said.

Various lighting related to thermal vision is another major application category, he noted, adding that one application is simply to introduce illumination to create shadows and contrast. But there are also beacons and other applications, including mid-IR communication links and lidar.

He predicts that many new mid-IR laser technologies will emerge in the next few years – among them, quantum cascade lasers, which offer a new approach in certain parts of the mid-IR spectrum. Other semiconductor lasers, interband cascade lasers and gallium antimonide diode lasers, which mostly cover different parts of the spectrum, also have different features, he said. OPOs and amplifiers continue to improve, and there are also advances in solid-state and fiber lasers for specific parts of the spectrum.

“We agree with Hausken’s overall [market] growth assessment, and, in fact, it may be more bullish,” said Michael Radunsky, product marketing manager for Daylight Solutions in San Diego. “We are focused on quantum cascade and interband cascade lasers and the diode side of the market, but here we have seen tremendous growth in orders and interest. Further, the types of customers have grown from scientists and those on the cutting edge to established companies not populated by laser physicists who now accept the technology as a viable solution to their sensing needs.”

Radunsky mentioned some applications newly served by these mid-IR coherent, narrowband light sources: protein folding dynamics studies and facilitation of drug development, stand-off explosive detection, time-resolved IR spectroscopy, sub-diffraction-limited hyperspectral imaging (scanning near-field optical microscopy), and the detection of low-volume or transient analytes.

The report from Strategies Unlimited includes a model for scaling the wafer-based semiconductor laser products to larger volumes and lower prices.

“There is a need for lower-priced sensor products, which, for mid-IR lasers, means lower-priced lasers, and many point to semiconductor lasers as a good platform to do that,” Hausken said. “That generally makes sense, since the same model has worked for other semiconductor laser products, even in moderate volumes. In high volumes, it can be extremely advantageous.

“Where one has to be careful is to assume that, since a product is based on semiconductors, it necessarily can migrate quickly and easily to high volumes and low prices. First, it may be hard just to scale the technology. For example, uniformity on larger wafers can be very difficult to achieve. Second, there is a chicken-and-egg problem that has to be overcome. It happens incrementally, not in one giant step.

“Finally, large volumes are only great if the prices are high enough to make a decent margin. If not, it can be more profitable to scale the company to a smaller volume. If they can be achieved, however, the high volume opportunities are very exciting. New sensors could be used in medicine and for environmental monitoring at low cost.”

Recent innovations could help the mid-IR laser market; for example, quartz-enhanced photoacoustic spectroscopy is an inexpensive way to detect mid-IR radiation. “Part of the problem is that the detectors can be quite expensive, especially if they need to be cooled,” Hausken said. “This spectroscopy can sometimes sidestep that.

This integrated mid-IR laser system was developed by Fibertek Inc. and Northrop Grumman Defense Systems Div. as an enhancement to the mid-IR source in the AN/AAQ-24(V) Nemesis directional IR countermeasures self-projection suite used in fixed and rotary wing aircraft against heat-seeking missiles. Courtesy of Fibertek and Northrop Grumman.

“The same goes for the uncooled focal plane arrays for imaging. Since the mid-IR range spans thermal emission, the detector noise declines if you cool it. This is especially important when the signal is low, or the pixel size is small. In recent years, the quality and price of uncooled focal plane arrays has improved. This makes thermal imaging more affordable, which means that various illumination products are more attractive, too.”

An important market trend is vertical consolidation – customers buying their suppliers, Hausken said. The vertically integrated companies prefer to keep the technology in-house – sometimes also selling it outside and sometimes not – because it sets them apart. Given that landscape, some of the new mid-IR laser companies will be nice targets for such suitors, he said.

Mid-IR laser technololgy is helping vertically integrated companies differentiate themselves from competitors in segments such as solid-state lasers in medical systems, OPOs for military systems and in mid-IR semiconductor lasers in sensing systems, he added.

Among the challenges faced by mid-IR suppliers are components that have a hefty price tag because of requirements for exotic materials and coatings, cryogenic cooling and low manufacturing volumes, according to the report.

The types of technologies that compete with mid-IR lasers depend on the application, Hausken said. In materials processing, there is competition mainly from 1-µm solid-state and fiber lasers, and in military illumination, from the near-IR imaging and illumination technologies. In sensing, there are competing near-IR lasers in Raman spectroscopy, and lamps and glow bars in Fourier transform IR.

“There are many competitive technologies, and many are inexpensive, so it is a great challenge for mid-IR laser suppliers to identify those applications where they have an advantage, even if the price is higher.”