High Energy Lasers Green, David10/20/2018

David Green

85 NW Sleret Ave

Gresham, Oregon

503-492-2108

High Energy Lasers used as Weapons

David Green

Advancements in technology has brought about many changes in our everyday lives. Some of these changes are beneficial and some are not. In our race for advancement, we have developed many weapons, none of them as formidable as the laser. Lasers have great potential in industry, surgery and communications. To understanding how society has advanced towards high-energy lasers: a better understanding of their development and functionality is needed.

Lasers come in different forms and construction. However, all lasers contain an energized substance that has the properties to intensity the light passing through it. This substance can be made from a variety of mediums. The mediums can be in any of the principle states such as solid, liquid or gas. These mediums must have the ability to store energy until it is released as light.

The variation of substance establishes the medium’s factor. This factor contributes to the lasers amplification, along with the wavelength and intensity of the incoming light, and the length of the medium.

Figure 1 diagram of a laser in operation

To increase the intensity of the light beam that is passing through the medium, energy must be added. The energy is supplied by an additional source. The process is known as “pumping.” The photon’s energy (E) is determined by its frequency (V) and Planck’s constant (h). Photon emission occurs when the electron drops from one state to a lower state.

The energy source causes the electrons in the medium to become excited. While absorbing the energy the electrons will climb into a higher state. This state is unstable and the electrons will fall back to the lower state, however they will emit photons. The photons will travel in a multitude of directions. On each end of the medium are attached mirrors, one of which has a lesser reflective property than the other. Some of the photons strike the mirrors and are reflected back along the length of the medium.

Figure 2 Photon building up energy

Lasers operate at relative wavelengths; in appendix A is a chart of laser types and their corresponding wavelengths.
What makes a high energy laser (HEL)? When laser energy is more that 1 Joule/pulse, and the average power exceeds 100 Watts, then the laser is considered high energy. Actual systems develop up to 100,000 Joules, and an average power of 1,000,000 Watts. The peak power on the pulsed lasers may even exceed 10,000,000,000 Watts.

At the High Energy Laser Systems Test Facility (HELSTF) located in White Sands Missile Range, New Mexico, resides the Mid Infrared Advanced Chemical Laser (MIRACL), the United States' most powerful laser. The Mid-Infrared Advanced Chemical Laser (MIRACL) was the first megawatt-class, continuous wave, chemical laser built in the free world. It is a deuterium fluoride (DF) chemical laser with energy spectra distributed among about 10 lasing lines between 3.6 and 4.2 microns wavelength. It remains the highest average power laser in the US. MIRACL operation is similar to a rocket engine in which a fuel (ethylene, C2H4) is burned with an oxidizer (nitrogen trifluoride, NF3).

Free, excited fluorine atoms are one of the combustion products of MIRACL’s exhaust. Just downstream from the combustor, deuterium and helium are injected into the exhaust. Deuterium combines with the excited fluorine to give excited deuterium fluoride (DF) molecules, while the helium stabilizes the reaction and controls the temperature. The laser's resonator mirrors are wrapped around the excited exhaust gas and optical energy is extracted. The cavity is actively cooled and can be run until the fuel supply is exhausted.

The laser's output power can be varied over a wide range by altering the fuel flow rates and mixture. This laser produces a beam in the resonator is approximately 21 cm high and 3 cm wide. Beam shaping optics are used to produce a 14 cm square beam shape, which is propagated through the rest of the beam train.

MIRACL ready for action

A Beam Director is mounted on top and consists of a large aperture (1.8 meter) gimbaled telescope with optics to point the MIRACL at the target. The high power clear aperture is 1.5 meters. The remaining 0.3 meters is normally reserved for a tracker using the outer annulus of the primary mirror. The system is extremely agile and capable of high rotation and acceleration rates. The targeting device (SLBD) weighs 28,000 pounds, of which 18,000 are on the movable portion. The SLBD can also be used as a sensor platform.

The telescope is capable of focusing from a minimum range of 400 meters to infinity. A suite of infrared and visible sensors on the top of the gimbal (off axis from the HEL aperture) is used to acquire and track the target. These sensors look through a 40 cm telescope that can focus over the same range as the SLBD telescope and also correct for parallax between the two lines of sight. Boresight between the SLBD telescope and the sensor is maintained by an automatic laser alignment system. In addition, an aperture-sharing element in the high power beam path makes it possible to track a target through the full 1.5 meter telescope aperture even when the high power beam is propagating.

Artist rendering of the SLBD

These elements have been combined into an integrated system that can acquire and track targets at extended ranges, accept a very high energy beam, focus and aim the beam on a moving target, and keep this beam at the same position as long as necessary to destroy or disable the target. The SLBD has successfully engaged five BQM-34 drones as well as a supersonic Vandal missile, all at tactically significant ranges.

This development has brought the army and air force new weapons. The Airborne Laser (ABL) weapon system consists of a high-energy, chemical oxygen iodine laser (COIL) mounted on a modified 747-400F (freighter) aircraft to shoot down theater ballistic missiles in their boost phase. A crew of four, including pilot and co-pilot, would be required to operate the airborne laser, which would patrol in pairs at high altitude, about 40,000 feet, flying in orbits over friendly territory, scanning the horizon for the plumes of rising missiles. Capable of autonomous operation, the ABL would acquire and track missiles in the boost phase of flight, illuminating the missile with a tracking laser beam while computers measure the distance and calculate its course and direction. After acquiring and locking onto the target, a second laser, with weapons-class strength, would fire a three to five second burst from a turret located in the 747's nose, destroying the missiles over the launch area.

Artist rendering of THEL in action

The U.S. Army Space and Strategic Defense Command is working on a new active defense weapon system concept to enhance protection for combat forces and theater level assets for the Force XXI Army. The mobile Tactical High Energy Laser, or THEL, weapon system would provide an innovative solution for the acquisition and close-in engagement problems associated with so-called "dumb munitions" -- a primary concern because counter-battery fire may not be an option in densely populated areas.

In its first live warhead test, the Tactical High Energy Laser (THEL) system intercepted and destroyed an armed Russian-made Katyusha rocket within seconds of its launch at the White Sands Missile Range. The system detected the 10-foot-long, 5-inch-diameter rocket with its radar before shooting it down at the speed of light with any difficulty.

The army’s LBL program utilizing the THEL data.

Given the advancements in technology and development in high-energy lasers, military defense weapons of war would naturally follow. The research into HEL is mainly funded by the federal government. This double edge sword has given industry opportunities that would never have been available. Research continues, weapon development along side gives America the advancement in industry to compete in today’s global economy

Star wars program SBHEL in construction

MIRCLE night test at White Sands

Appendix A Wave Lengths Of The More Common Laser Types

Laser Type / Media / Wave Length (s) / Nanometers
Excimer Gas Lasers / Argon Fluoride / (UV) / 193 nm
Krypton Chloride / (UV) / 222 nm
Krypton Fluoride / (UV) / 248 nm
Xenon Chloride / (UV) / 308 nm
Xenon Fluoride / (UV) / 351 nm
Gas Lasers / Nitrogen / (UV) / 337 nm
Helium Cadmium / (UV) / 325 nm
Helium Cadmium / (Violet) / 441 nm
Argon / (Blue) / 488 nm
Argon / (Green) / 514 nm
Krypton / (Blue) / 476 nm
Krypton / (Green) / 528 nm
Krypton / (Yellow) / 568 nm
Krypton / (Red) / 647 nm
Xenon / (White) / Multiple
Helium Neon / (Green) / 543 nm
Helium Neon / (Yellow) / 594 nm
Helium Neon / (Orange) / 612 nm
Helium Neon / (Red) / 633 nm
Helium Neon / (NIR) / 1,152 nm
Helium Neon / (MIR) / 3,390 nm
Hydrogen Fluoride / (MIR) / 2,700 nm
Carbon Dioxide / (FIR) / 10,600 nm
Metal Vapor Lasers / Copper Vapor / (Green) / 510 nm
Copper Vapor / (Yellow) / 570 nm
Gold Vapor / (Red) / 627 nm
Doubled Nd: YAG / (Green) / 532 nm
Neodymium: YAG / (NIR) / 1,064 nm
Erbium: Glass / (MIR) / 1,540 nm
Erbium: YAG / (MIR) / 2,940 nm
Holmium: YLF / (MIR) / 2,060 nm
Holmium: YAG / (MIR) / 2,100 nm
Chromium Sapphire (Ruby) / (Red) / 694 nm
Titanium Sapphire / (NIR) / 840-1,100 nm
Alexandrite / (NIR) / 700-815 nm
Dye Lasers / Rhodamine 6G / (VIS) / 570-650 nm
Coumarin C30 / (Green) / 504 nm
Semiconductor Lasers / Gallium Arsenide (GaAs) / (NIR) / 840 nm
Gallium Aluminum Arsenide / (VIS/NIR) / 670-830 nm

Work Cited

US Army Space and Missile Defense Command, “High Energy Laser System Test Facility, 03/09/2003,

Defense Department, “Tactical High Energy Laser THEL system” 03/09/2003,

Foundation for Advancement in Science, “Tactical High Energy Laser” 03/07/2003,

Foundation for Advancement in Science, “Laser Technology” 03/07/2003,

Robert Aldrich, ”Laser Fundamentals”, 03/07/2003,

John Gormally, “Laser Tutorial”, 03/07/2003,

1