Lasers emerged in 1958 as new and novel devices, and over
the years they have appeared in countless science-fiction movies to entertain
the masses. Fiction has become fact as scientists at Kirtland Air Force Base, Albuquerque,
NM, and around the world continue to research and develop laser technologies.
Much has evolved from the first appearance of lasers. Today,
gases, liquids and solids are used to create lasers. Some are as small as a
grain of sand and some are as large as a football field. In general, they have
become smaller, lighter and more powerful. As scientists continue their
research, laser applications continue to grow. The Air Force Research
Laboratory’s (AFRL) Directed Energy Directorate has been developing
technologies that have reached, or are near, fruition. The work at the
directorate began in the early 1960s when the Advanced Research Projects Agency
issued Order 313-62 to the Air Force Systems Command (now the Air Force
Materiel Command) to investigate lasers.
A task force, at the Air Force Weapons Laboratory (now the
Air Force Research Laboratory’s Directed Energy Directorate), was formed in
1966 to study the feasibility of laser systems for weapons applications.
Research in the 1970s resulted in the building of a
tri-service laser at the Starfire Optical Range. A contract for an airborne
pointer/tracker was initiated with Hughes Aircraft Co., and the Airborne Laser
Laboratory design effort was also initiated with General Dynamics Corp. The
first high-energy laser beam was generated from a gas dynamics laser. The
technology development at the end of the 1970s resulted in the completion of
ground testing for the Airborne Laser Laboratory.
In the 1980s, the first engagement against a tube-launched,
optically tracked, wire-guided missile (TOW) target at the White Sands Missile
Range was completed, resulting in the first high-energy laser beam ever fired
from an aircraft in flight. The first attempt at an AIM-9 Sidewinder air-to-air
missile engagement was carried out at China Lake Naval Air Station in Ridgecrest,
CA, on May 28, 1981.
In July of 1983, the Air Force announced a major milestone
in weapons development with the successful engagement of the Airborne Laser
Laboratory’s NC-135, the military version of Boeing’s 707. The aircraft was
modified to use a carbon-dioxide laser against AIM-9 missiles.
Five missiles were successfully destroyed. Two months later,
the Airborne Laser Laboratory successfully engaged a BQM-33A drone at low
altitude over the Pacific. It was the final target engagement of this program.
The Airborne Laser Laboratory program was completed in 1984.
It provided the Air Force invaluable insight into the disciplines and
technologies of beam control, atmospheric effects, optical component
integration, lightweight structures and pointing and tracking that are vital to
laser research today. It also showed that a laser mounted on an aircraft could
be an effective defensive weapon.
“The Airborne Laser Laboratory created the path of
opportunity for today’s directed-energy systems,” said Colonel Mark W. Neice,
chief of the Directed Energy Directorate’s Laser Division. “It is the program
that allowed other programs to emerge.”
As a tool for the warfighter, lasers can pinpoint a target
from a cluttered environment of non-targets to destroy only what is selected.
Collateral damage, if not completely eliminated, can be reduced greatly as
carefully measured amounts of energy are delivered, said Neice.
Laser research and development work at the directorate
includes work with the chemical, solid-state, and diode lasers. Research in these
and other areas will determine the laser power source of the future.
According to Dr. Kip R. Kendrick, program manager for the
Advanced Tactical Laser, the directorate has done extensive work with a
chemical laser invented there in 1977, which can be scaled to mega-watt power
levels generating its energy through chemical reaction. It is considerably
compact compared to the carbon-dioxide laser, a kilowatt-class system that was
used on the Airborne Laser Laboratory.
The Chemical Oxygen Iodine Laser’s (COIL) energy is created
by the chemical reaction between energetic oxygen and iodine molecules when
they are mixed. The laser propagates at 1.315 microns in the infrared spectrum.
The wavelength travels easily through the atmosphere and has greater brightness
or destructive potential on a target.
The COIL had been implemented in a new concept of
operations, the Airborne Laser (ABL). The ABL, a Missile Defense Agency
program, involves the use of the COIL on a modified Boeing 747-400
freighter-series aircraft to destroy ballistic missiles during their boost
phase.
In addition to this laser, there are three other important
lasers aboard the aircraft: the Active Ranger System, which provides
preliminary tracking data; the Track Illuminator Laser, which produces more
refined tracking data; and the Beacon Illuminator Laser which measures the
amount of atmospheric disturbance.
The development of this revolutionary use of a
directed-energy system as a weapon, rather than as a targeting or range-finding
apparatus, should change how our country will be able to defend itself.
“A near-term application is putting the COIL on tactical
platforms, such as a C-130,” said Kendrick. Ideally, this will evolve to a
C-130 gunship and eventually lead to lasers on fighter-type platforms. With a
sealed exhaust system, chemicals are not ejected overboard and zeolites—a
substance that acts as a gas sponge—allows for gas to be stored in a small
volume, added the senior scientist. An Advanced Concepts Technical
Demonstration (ACTD), sponsored by the Air Force’s Special Operations Command,
is planned for completion in December 2006.
Kendrick said the AFRL’s Advanced Tactical Laser Technology
Development Program is developing technology in parallel with the Special
Operations Command and Boeing to enhance the capabilities of the Advanced
Tactical Laser.
The advantage chemical lasers now have over solid-state
lasers is in the amount of energy produced, however, research and development
with solid-state lasers include improving their power levels.
Currently, the state-of-the-art solid-state laser has an
operational power of 2 to 3 kilowatts. The Directed Energy Directorate, with
the Army and the High Energy Laser Joint Technology Office, is involved in a
program to develop a 25-kilowatt solid-state laser, said Neice. The eventual
goal of this joint project is to demonstrate the laser at this power level in
2005, and ultimately, a solid-state laser at 100 kilowatts in 2007.
If the goal is reached, the solid-state laser could become
the laser of choice for directed-energy weaponry over the chemical laser
because of its smaller size, larger magazine and no concerns for chemical
management, such as chemical waste stream. Chemical mixing and wasting
complicates the logistics trail and is undesirable for battlefield operations,
said Neice.
All branches of the military are interested in the use of
the solid-state laser, said Neice. The Army is interested in it as an element
of Future Combat Systems, the Navy is interested in its use for ship-based
defense, and the Marines are interested for its capability in area defense. The
Air Force’s interest relates to airborne applications, such as fighter
aircraft, as well as space-based applications.
According to Neice, other laser research and technology
development being accomplished at the directorate involves the study of lasers
and sensors working together to detect and defend large platforms dealing with
air-mobility and air-refueling missions. This work is under the umbrella of the
Large Aircraft Infrared Counter Measures (LAIRCM) program.
“The focus is to improve the laser and extend the range,”
Neice said. He further explained that protection against all threats including,
short-range, rocket- propelled grenades and shoulder-launched missiles, known
as man-portable air defense (MANPAD) systems, is being investigated.
“Infrared missiles are a threat, and our work deals with
directing lasers to defeat those vulnerable spots of the missiles,” said Neice.
Work with the Focal Plane Array, a new type of missile seeker
consisting of a two-dimensional array of detectors that creates an image from
light, has been conducted with the different branches of the military and a
team from the British Ministry of Defence at the directorate. This joint team
has been testing surrogate missiles and the countermeasures used against them.
“Designed to better attack an aircraft and reject flares,
the detectors can see what the human eye cannot,” said Donald J. Smith, the
directorate research physicist who has headed some of these experiments.
According to Smith, the detectors are placed on the front
end of the missile and act like the eye’s retina electronically transferring an
image to the computerized brain of the missile where the information is
processed guiding the missile to impact.
Fiber lasers, light through a fiber, is yet another area of
concentration for the Directed Energy Directorate’s laser division. Because
fiber lasers are good for heat distribution, easily transmit laser light and
are robust, they have proven effective in daily applications such as medical,
welding and repair work.
For the medical arena, the laser medical pac and laser
medical pen, both developed in-house, provide medical personnel with a unique,
compact, portable and battery-operated laser capability. The laser can cut like
a scalpel and coagulate bleeding. The military applications for these items are
with advance trauma life support on the battlefield and can be used by special
operations and pararescue personnel.
Laser energy is delivered to the medical pac by a
fiber-optic cable that provides very intense power at the tip of the
instrument. The output wavelength is 808 nanometers with an output power of 8
1/2 watts.
As a directed energy system, fibers are worth exploring for
future weapon applications. The primary application for this type laser is
development of high-energy lasers for tactical weapons that could be
incorporated into current platforms using only electricity as the energy
source. The major technical challenge is to coherently combine many of these
single mode fiber lasers to achieve kW or greater laser systems.
Solid-state lasers use diodes to pump gain material, such as
crystal or glass. Diode lasers, also known as semi-conductor lasers and closely
related to the light-emitting diodes that provide the red numeral and letter
displays on some calculators, are small and can be mass-produced relatively
inexpensively.
Diodes are compact and are very efficient at converting
electrical power to laser light. Due to their narrow emission bandwidth, they
reduce the thermal loading of the laser crystals and allow higher powers to be
extracted, said Captain Steven M. Massey, program manager for the directorate’s
special projects section.
The (diodes are reliable and have an approximate lifetime of
10,000 hours, said the laser physicist. The research and technology development
in this area is focused on fiber-coupled diode lasers as efficient small
sources of excitation energy for a solid-state laser which could lead to small,
lightweight, efficient, high-average power lasers as battlefield weapons.
The Directed Energy Directorate places great emphasis on
integrating and transitioning research technologies into military systems used
by operational commands and maintained by the Air Force Materiel Command.
The laser division is the United States Air Force’s center
of expertise for developing high-energy lasers and getting those technologies
to U.S. military forces.
The Davis Advanced Laser Facility, a research facility for
the Air Force Research Laboratory’s Directed Energy Directorate, is used for
research development of chemical, electrical and hybrid lasers that can be used
in air-, ground-, and space-based systems.
The facility consists of six major laboratories, along with
several smaller ones, a chemistry laboratory, an electronics laboratory and two
conference rooms. The interior configuration is such that it can be rearranged
to fit the needs of new experiments. Two of the laboratories are dedicated to
chemical laser work. The other four laser laboratories are used for solid-state
or electrical laser research.
The Directed Energy Directorate is located at the Phillips
Research Site, Kirtland Air Force Base, NM. In addition to laser development,
the directorate is committed to high-power microwave and advanced optics and
imaging technologies.
The mission of the directorate is to develop innovative and
advanced directed-energy technologies that will provide instant defeat and
instant detection of adversaries. The vision of the directorate is one that
provides the U.S. military forces with “speed-of-light” battlespace dominance.
O
Deborah Mercurio is with the Air Force Research Laboratory’s
Directed Energy Public Affairs Office.