A heat-seeking missile bearing down on an aircraft zeros in on the infrared signature of its exhaust. In the past the aircraft might deploy flares or, if the plane was large enough, it might use a rudimentary laser to disrupt the incoming missile's guidance system. Neither of these approaches has proved reliable enough for the U.S. military's liking, which is why the Army is considering new type of infrared countermeasure (IRCM) system that uses a smaller, more nimble solid-state laser designed to better protect helicopters and other low-flying aircraft from small arms and shoulder-fired missile attacks such as those that are so prevalent in Afghanistan and Iraq (pdf).

The Army's choice of updated IRCM systems is expected in a few months, which is why several defense contractors developing this technology are making a serious push for consideration at this week's annual Association of the United States Army meeting and expo in Washington, D.C.

Whereas the U.S. military, led by the Army, has for decades used IRCM technology weighing several dozens of kilograms to disrupt heat-seeking missile attacks, the Army is hoping a newer, lighter approach called Common Infrared Countermeasures (CIRCM) will more reliably protect a wider range of aircraft. To meet the Army's 38.6-kilogram CIRCM weight limit, some contractors are turning to solid-state quantum cascade lasers as a means of disrupting a missile's guidance system and throwing it off course.

Quantum cascade lasers, first developed at Bell Laboratories in 1994, are semiconductor lasers that emit in the mid- to far-infrared portion of the electromagnetic spectrum. Such lasers can be made smaller, lighter and more reliable than the optical parametric oscillator (OPO), the multiband laser OPO, and the fiber laser–pumped systems used in current IRCM systems. This is because a quantum cascade laser directly converts electrons entering the semiconductor to photons. (Multiple photons can even be generated by a single electron, improving the system's efficiency.) Other types of lasers require more complicated setups for generating the wavelengths needed to target missile-guidance systems. In addition, semiconductor lasers can be manufactured at about 4.5 millimeters in length in high volumes on wafers similar to the way transistors are produced. A conventional glass OPO laser could be up to half a meter long.

ITT Electronics Systems (see video below)—competing for the Army contract against BAE Systems, Northrop Grumman and Raytheon Co.—is proposing a CIRCM using a solid-state quantum cascade laser system developed by Daylight Solutions. The system, which Northrop Grumman is also using as part of its CIRCM bid, features a low-wattage semiconductor laser much like those found in DVD and CD players, although the CIRCM laser emits invisible wavelengths rather than optical red light, says Tim Day, president and CEO of Daylight Solutions.

ITT and Daylight have worked together in the past, with ITT integrating an earlier version of Daylight's fiber-coupled quantum cascade–based JammIR laser system into its IRCM technology. The companies claim to have conducted several successful flight tests  on board U.S. military Sikorsky UH-60 Black Hawk helicopters.

ITT has taken a modular approach to its CIRCM in an effort to make the system available to a wider range of aircraft. "We tried to make the system extremely flexible, having multiple boxes so we divide up the functionality, putting the lasers in one box, the pointer trackers in another and the power supply in still another box installed on the aircraft," says Bob Palazzo, ITT Electronic Systems' director of advanced programs. "We interconnect the boxes with a fiber-optic cable so they can be placed throughout the aircraft and provide a more balanced weight distribution."

Raytheon claims its CIRCM is seven kilograms less than the Army's requirement, light enough to be installed on unmanned aircraft systems drones—although this was not an Army requirement at this time.

The Army is looking to equip 1,076 aircraft with CIRCM systems initially at an estimated cost of $1 billion to $1.5 billion. If the CIRCM implementations are successful, the number of aircraft—primarily light- to medium-weight helicopters—outfitted with the technology is expected to grow to as many as 4,000. The Army is expected to choose two of the four competing companies within the next three months to move on to the technology development phase of the program.

Video courtesy of ITT