Light Wars: The Bright Future of Laser Weapons WAR TECH SPRING WAR TECH by Hemma Mistry Lasers as directed energy weapons: this idea may sound like the ray guns and light sabers of a science fiction writer’s dreams, but the idea of incorporating lasers into military technology has been pursued since lasers were first invented. The U.S. government has spent millions of dol- lars attempting to make laser weaponry a reality. In 1983, the Reagan administration initiated an ambitious effort to create missile defense systems using lasers in space, nick- named “Star Wars.” Although these systems were never realized, the “Star Wars” program paved the way for future laser research. The Clinton administration continued the effort for missile defense laser weaponry with an agreement with the Israeli government in 1996. Currently there are several U.S. military funded programs developing laser weapons. What is a Laser? http://cord.org/step_online/st1- 5/images/Fig05-01.gif fying light through the process of stimulated emission. In 1916, Albert Einstein first theorized stimulated emission as one of the three processes by which light can interact with matter (Perram, et al. 2004). In this process, a photon of light hits an electron in an excited, high energy state, caus- ing the electron to fall to a lower energy state which releas- es a photon of light with the same wavelength, phase, and direction as the incident light. Mirrors are then used to amplify the emitted light, resulting in a beam of monochro- matic, coherent, directed laser light. This diagram shows the basic components of a laser. The gain medium, or amplifying medium, contains atoms whose electrons are stimulated to emit light. Mirrors on either end of the optical cavity reflect the light back several times through the gain medium, amplifying the beam. An energy input is also required to excite the electrons in the gain medium into a high energy state so that stimulated emission can occur. Military Interest in Lasers The characteristics of laser light give lasers the potential to make effective weapons. Because a laser beam is focused in one direction, laser weapons have the poten- The basic components of a laser tial to be extremely accurate in hitting targets. In combat, Lasers can serve as a valuable technology in warfare this accuracy would minimize the destruction of surround- because the light they emit has important and useful quali- ing area that is caused by more imprecise weapons such as ties. Laser light is monochromatic and coherent, which explosives. The precise aim of the weapon and the mini- means that not only does the light have a uniform wave- mal destruction would also reduce the harm caused to civil- length, but also the light waves maintain the same phase ians and other unintended targets. Lasers would also relationships over time. The waves also propagate in a def- enable the military to attack targets from far away, provided inite direction. These properties allow laser light to carry a that there is an unobstructed path for the laser’s beam to large amount of energy travel between the that can be applied in a weapon and target. specific direction, which Lasers could be used to destroy satel- Since the beam would is highly advantageous lites in space, or conversely, space-based travel at the speed of for a weapon. light, the weapon would lasers could attack targets on the ground. be effective on these The word laser is actually an acronym distant targets almost for “Light Amplification by Stimulated Emission of instantaneously. This long-range capability of lasers also Radiation,” and as the name implies, lasers work by ampli- means that a laser attack could be carried out covertly from