Military laser technology spurs new civil applications
By Wilson Dizard III
Mogadishu, Somalia, 1995 - during the United Shield international humanitarian mission, U.S. troops man their perimeter at night. Four Somali men approach. "We illuminated them with a near infrared laser which they did not detect so we could get a better view of them through our night-vision gear," reports Air Force Lt. Robert Ireland.
"The first man clearly carried an AK-47 [rifle] and carried himself in an aggressive manner. Two men carried handguns of some type and the fourth man appeared unarmed," Ireland says. "They were 250 to 300 meters from our position and quickly becoming a threat. I fired the Saber Laser Illuminator at the man carrying the AK-47. All four men stopped immediately. The three men not illuminated took one long look at the man blinking red and fled. It was apparent that whatever was going to happen next was going to happen to him. The man with the AK-47 turned around in obvious terror and fled. He was no longer a threat and we did not see those men again for the duration of the U.N. withdrawal."
Ireland, operations officer with the Laser Applications Group at the U.S. Air Force Phillips Laboratory at Kirtland AFB, N.M., had an experience that is rare for many electronics developers - being able to see a new system work and save lives in a military operation.
Ireland and his colleagues at Phillips are working to apply commercial off-the-shelf (COTS) laser technologies to systems that are just entering production and have particular advantages not only for military applications, but also for "operations-other-than-war" and crime fighting.
The Saber 203 Laser Illuminator developed at Phillips relies on "advances in laser diode technology in the last decade, and on the development of very small laser diode arrays," Ireland says. He cites the semiconductor lasers produced at Opto-Power Inc. of Tucson, Ariz., as an example.
"From a technology point of view, we have higher yields now of both silicon and gallium arsenide semiconductors from wafers, as well as better packaging and fiber coupling techniques," he says.
The telecommunications industry in large part have developed the fiber coupling technologies, Ireland says. A single fiber optic strand is connected to each of many laser diodes on an array. "Each company does it differently. It`s done by hand, and they won`t tell you how they do it," he notes.
The fiber optic strands guide the laser light to its output unit, such as a telescope, which can be several meters away. That`s helpful when the laser system is to be installed on an aircraft, and external bulges containing laser gear would increase the aircraft`s vulnerability to radar.
System fits on grenade launcher
The Saber 203 system is specially fitted into an unmodified M-203 40-millimeter grenade launcher.
One part of the system, which houses the laser transmitter, is a hard plastic capsule about the size and shape of a 40-millimeter grenade. The capsule fits into the launcher like an actual grenade.
The second component is a small control box that snaps underneath the launcher. A button on the control box "fires" the laser in a continuous beam to illuminate a target. In an emergency, the operator can eject the capsule and replace it with a grenade.
The Saber 203 uses a 220-milliwatt laser that emits visible light in the 650 nanometer band.
"The Saber 203 is going in to production by Science & Engineering Associates of Albuquerque, N.M.," Ireland says. Company engineers will build 70 to 80 units in 1997 and later reach a production level of 400 to 500 units monthly, according to current plans.
Phillips experts have developed laser technology that laboratory staff then combine with COTS gear to bring systems to fruition. Ireland says the laboratory has devised a proprietary method of "homogenizing" laser light within a field that is being illuminated by near-infrared light. This method assures that the laser radiation will be spread at the same power density across the entire area to be illuminated. "It`s more appealing to the eye, and it`s much safer," he says.
Eye safety is a high concern for developers of laser light systems, according to Ireland. About a third of the budget for each Air Force laser system goes to assuring that the system will not exceed Mil-Std-1425A and ANSI Z136.1-1993 limits for maximum permissible exposure to laser radiation.
Near-infrared laser light systems for covert illumination generate energy in the 780-nanometers to 2-micrometers range. During United Shield, Marine units using near-infrared target-designation systems found them useful to a range of three kilometers. Similarly, the Saber 203 designated human targets at 300 meters and vehicles - called technicals in the parlance of the Somali conflict - at farther than a kilometer.
Using active night-vision gear of any kind presents the problem of possible enemy detection of emitted radiation. Facing an enemy equipped with sophisticated scanners ups the technological ante, Ireland and his colleagues know.
"If you`re using a laser illuminator with night-vision goggles and someone [on the other side] uses a scanner, we can hop out of band. You actively illuminate in a band that is not detectable by standard night-vision gear. For example, the Russian technology only allows you to see in a certain wavelength. So we hop out of band - out of what they can see," he says.
FLIR Systems Inc. of Portland, Ore., has forged a Cooperative Research and Development Agreement (CRADA) with Phillips Lab to commercialize Air Force-developed laser optics systems for agencies combating drug smugglers and other criminals.
Federal and state police agencies often use passive thermal imaging systems - many produced at FLIR Systems. "Such sensors, however, cannot read a license plate, ship registration, or aircraft tail number," Ireland says. "But an operator with special eyewear, using a laser spotlight having a wavelength invisible to the unaided eye, may be able to."
John Miller, director of advanced technology for FLIR Systems, says the laser illuminating system that FLIR Systems is developing with Phillips "works under totally cloudy skies, and works better in fog or snow than passive means."
Miller explains that passive infrared night-vision systems, operating in the 10-micron wavelength, cannot sense contrasts in paint schemes, which is important in reading license plates. Paints are deliberately made to have reflective contrast, but not thermal contrast, he points out.
"This system would provide a laser which would provide a high contrast for paint schemes," Miller says.
Dick Kerr, vice president for advanced development at FLIR Systems, adds that countermeasures would not be a problem. "We`re talking about operations other than war, where you`re not expecting a sophisticated system to detect the laser." The system likely will be marketed for police helicopters that now use searchlights.
FLIR Systems, a company that draws its name from the acronym for forward- looking infrared, plans to integrate the laser technology with an existing infrared imaging system called Safire.
A key advantage of the integrated system is its ability to help uncover police evidence.
"You want to have evidence that will stand up in court," Kerr says. The U.S. Coast Guard, for example, uses such systems to gather evidence in cases involving illegal fishing. "In court, the lawyers will question how well they read that ship registry. We`re going to hook the system up with a videotape, so the evidence can be used in a court of law."
The key enabling technology is the laser diode arrays that are high power, low cost, and high reliability, Kerr says. "These are solid-state lasers. You put in electricity and get out laser light. There are tricks to coupling the optical fibers to the lasers and to the telescope [that directs the laser light to the desired area]."
FLIR Systems engineers are doing proof-of-principle testing of the system, and company executives are hoping to test the system in stormy weather to judge its effectiveness in rain and fog.
Laser diodes and associated gear in the laser-augmented Safire system could be located in the fuselage of an aircraft, and the light transmitted through a bundle of optical fibers to a gimbaled turret on the surface of the aircraft.
The Safire system likely will use laser diode arrays with a power output of 15 watts. By contrast, the laser in a standard CD player might generate about 10 microwatts.
"A few years ago, you could not get a 10- to 15-watt laser diode array," Kerr says. Although experts at Phillips Lab have built laser diode arrays as powerful as 100 watts, that equipment is not commercially available. "Heat becomes a problem [at those power levels]. Phillips has developed technologies to handle the heat," Kerr says.
Thermoelectric coolers can dissipate heat in such high-power laser diodes. These coolers are electrically driven heat exchangers first developed to cool electronic equipment in spaceborne systems where water wasn`t available as a coolant.
The Phillips/FLIR Systems CRADA began in September 1996 and is to run for about a year, Kerr says.
"We plan to do some testing of laboratory-scale prototypes at the Phillips laser range in March. The system will fly in an aircraft in July, he says." A production version could be available for sale in late 1997.
"The laser itself is in the near infrared," Kerr says. "The silicon diode technology, because of physics, likes to radiate at 800 nanometers. That`s going to stay indefinitely. That`s slightly into the infrared."
Kerr notes that the infrared/laser system could have applications in perimeter surveillance for industrial security at sites such as nuclear power plants or weapons-storage facilities.
Ireland says additional research is moving in the direction of green laser diodes. "The human eye is most responsive in green [wavelengths], because most things we perceive are green."
Using green light for visible-laser illuminators enables the systems designer to use less power than white laser light. Phillips is funding research on such lasers at Brown University in Providence, R.I., and at the University of Florida at Gainesville.
"A lot of it involves COTS technology," Ireland says. "In recent years, the systems have become more rugged and more eye safe."
The Laser Applications Group at Phillips has 14 researchers and a budget of about $4.5 million. The Air Force provides $500,000 annually, and other agencies such as the Defense Advanced Research Projects Agency, the Marine Corps, and the Office of Special Technologies provide the rest.
Among the other diode laser applications developed at Phillips recently are:
- Programmable Infrared Marker, which soldiers can use to guide helicopters equipped with infrared sensors safely to landing zones in unfamiliar terrain at night. The system uses a 50-foot fabric strip lined with light-emitting diodes spaced about three feet apart. It weighs two pounds and stores in a 6.5-inch-diameter by 2-inch high disk-shaped dispenser that can be carried in a pants pocket.
- Laser Medical Pen, a ruggedized one-pound handheld wand that can cut like a scalpel, close wounds, and coagulate bleeding. The five-watt device uses lithium batteries and is capable of contact and free-beam lasing.
- Laser Medical Pac is a larger system that weighs six pounds and fits into a belt pack. It uses an 8.5-watt laser to cut like a scalpel, coagulate bleeding, and close wounds. The system could be used for advanced trauma life support on the battlefield or in civil applications such as stabilizing highway accident victims before they are transported to a hospital.
- Pocket Laser Communicator, a small, light transceiver for secure voice communications over distances as far as 1.2 miles. The system uses a 9-volt rechargeable battery that allows four hours of operation. A magnifying lens focuses energy on the detector and an optical filter reduces noise.