High energy laser (HEL) weapons are ready for some of today’s most challenging military applications. For example, the Airborne Laser (ABL) program is designed to defend against Theater Ballistic Missiles in a tactical war scenario. Similarly, the Tactical High Energy Laser (THEL) program is currently testing a laser to defend against rockets and other tactical weapons. The Space Based Laser (SBL), Advanced Tactical Laser (ATL) and Large Aircraft Infrared Countermeasures (LAIRCM) programs promise even greater applications for laser weapons. This technology overview addresses both strategic and tactical roles for HEL weapons on the modern battlefield and examines current technology limited performance of weapon systems components, including various laser device types, beam control systems, atmospheric propagation, and target lethality issues. The characteristics, history, basic hardware, and fundamental performance of chemical lasers, solid state lasers and free electron lasers are summarized and compared. The elements of beam control, including the primary aperture, fast steering mirror, deformable mirrors, wavefront sensors, beacons and illuminators will be discussed with an emphasis on typical and required performance parameters. The effects of diffraction, atmospheric absorption, scattering, turbulence and thermal blooming phenomenon on irradiance at the target are described. Finally, lethality criteria and measures of weapon effectiveness are addressed. The primary purpose of the presentation is to define terminology, establish key performance parameters, and summarize technology capabilities.

Since the beginning of High Energy Laser systems, simulations have been used to predict performance, do parameter trades, and assist in troubleshooting. Today, simulations benefit from higher speed computers with more memory, but they are also being asked to do more. New types of HEL devices are being proposed, more hardware details are being incorporated, beam control systems are becoming more complex, innovative new systems are being designed to work under conditions of strong turbulence, and more types of targets are being considered. There are three types of physics level codes: resonator, beam control, and lethality. All three are slow running and require a high level of expertise to use. Scaling law codes are much easier to use and much faster running. These codes are based on analytical predictions and anchored to the wave optics simulations and to experiments. Scaling law codes can quickly predict performance, weight, and volume for various scenarios and conditions. Now that HEL systems are closer to reality, there is more interest in incorporating the scaling law codes into engagement codes, which predict overall system effectiveness in battle situations.

Deuterium fluoride (DF) lasers have been under development since about 1970. Their intrinsic ability to store high levels of energy internally plus their ability to quickly dispose of waste heat by the convective flow of exhaust gases make this type of laser attractive to the Army for producing high power levels for an air and missile defense weapon system. This paper reviews the basic principles of a DF laser, the chemistry and spectroscopy associated with producing an excited DF lasing molecule, and the generation of a high power laser beam. This paper also reviews the development history of DF lasers and early lethality demonstrations. This includes a detailed discussion of the Army’s recent Tactical High Energy Laser (THEL) Demonstrator, its architecture and successes during engagements of in-flight rockets and artillery projectiles. The Army is moving forward in developing a new generation, high power DF laser weapon system, the Mobile Tactical High Energy Laser (MTHEL). This system will provide our soldiers protection in the future against a variety of airborne threats.

In the late 1960's researchers realized that producing a population inversion in a moving medium could be used to generate high-energy laser beams. The first lasers to scale to the 10 kW size with good beam quality were supersonic flows of N2 - CO2, emitting radiation from the CO2 at 10.6 microns. In the 1970's gas dynamic CO2 lasers were scaled to hundreds of kilowatts and engineered into a KC-135 aircraft. This aircraft (The Airborne Laser Laboratory) was used to shoot down Sidewinder AIM-9B missiles in the early 1980’s. During this same time period (1970-1990) hydrogen fluoride and deuterium fluoride lasers were scaled to the MW scale in ground-based facilities. In 1978, the Iodine laser was invented at the Air Force Research Laboratory and scaled to the 100 kW level by the early 1990’s. Since the 60s, the DOD Chemical Laser development efforts have included CO2, CO, DF, HF, and Iodine. Currently, the DOD is developing DF, HF, and Iodine lasers, since CO2 and CO have wavelengths and diffraction limitations which make them less attractive for high energy weapons applications. The current military vision is to use chemical lasers to prove the principles and field ground and air mounted laser systems while attempting to develop weight efficient solid-state lasers at the high power levels for use in future Strategic and Tactical situations. This paper describes the evolution of Chemical Oxygen Iodine Lasers, their selection for use in the Airborne Laser (ABL), and the Advanced Tactical Laser (ATL). COIL was selected for these early applications because of its power scalability, its short wavelength, its atmospheric transmittance, and its excellent beam quality. The advantages and challenges are described, as well as some of the activities to improve magazine depth and logistics supportability. COIL lasers are also potentially applicable to mobile ground based applications, and future space based applications, but challenges exist. In addition, COIL is being considered for civil commercial applications in the US and overseas.

Lasers have come a long way since the first demonstration by Maiman of a ruby crystal laser in 1960. Lasers are used as scientific tools as well as for a wide variety of applications for both commercial industry and the military. Today lasers come in all types, shapes and sizes depending on their application. The solid-state laser has some distinct advantages in that it can be rugged, compact, and self contained, making it reliable over long periods of time. With the advent of diode laser pumping a ten times increase in overall laser efficiency has been realized. This significant event, and others, is changing the way solid-state lasers are applied and allows new possibilities. One of those new areas of exploration is the high energy laser. Solid-state lasers for welding are already developed and yield energies in the 0.5 to 6 kilojoule range. These lasers are at the forefront of what is possible in terms of high energy solid-state lasers. It is possible to achieve energies of greater than 100 kJ. These sorts of energies would allow applications, in addition to welding, such as directed energy weapons, extremely remote sensing, power transfer, propulsion, biological and chemical agent neutralization and unexploded and mine neutralization. This article will review these new advances in solid-state lasers and the different paths toward achieving a high energy laser. The advantages and challenges of each approach will be highlighted.

Active track and beacon illuminator lasers, which are critical components of most high energy laser beam control systems, have benefited significantly over the past decade from technology advancements that have enabled more than an order of magnitude growth in average output power while maintaining excellent beam quality. An overview of how high energy laser system illuminator requirements are developed, along with a short history and current status of diode-pumped solid-state laser illuminator technology development in the United States, will be provided.