A Monthly Journal of the IDSA
Directed Energy Weapons
By C.N. Ghosh *
Scientists knew for many years that either a coherent monochromatic light collimated beam; a beam of charged particles or neutral energy particles, can carry potentially destructive amounts of energy, capable under certain circumstances of melting or cracking metal. Effective range could be many thousands of kilometers. An United Nations protocol signed during their session from September 25 to October 13, 1995 banned use or transfer of blinding Laser weapons Yet there are reports appearing that the advanced nations are engaged in serious research work to develop Laser and Particle beam weapons.. Revolution in Military Affairs is on the anvil and it may be coming through the potential use of these Directed Energy Weapons. Such extraordinary kill mechanisms of future weapon systems raise a lot of questions in the military mind as well as about its implications.
Considering the capabilities of laser, United Nations decided to prevent its use against human beings and a protocol 1 was signed to limit the use of laser blinding weapons. As it stands, NATO nations are bound by this protocol and hopefully will restrict their use of laser weapons honouring the code of conduct dictated by the United Nations. These nations are to use laser against electro-optical sensors. But the development process in this direction belies all hopes of the United Nations. Laser weapons have already been dubbed as inhumane. Yet, the development of these weapons is progressing unabated. Certain defence analysts have already opined that the concept of nuclear weapons is as outdated as that of bows and arrows. Directed Energy Weapons (DEW) would replace the nuclear monsters soon enough and take the centerstage, probably proving the legendary HG Wells to be correct. In his book, The War of the Worlds, Wells talked about the invading Martians with heat ray guns. These ray guns of H G Wells are chillingly similar to the real laser weapons of today. At that time, DEW may have been the prerogative of comics and movies. But the superpowers of the pre- Cold War era took it up on themselves to develop these super killers. Clandestine research development went ahead under a strict veil of secrecy. Reports appearing in various magazines bring out to a large extent the general facts about the state of these weapons and the state of their development and the goal. This does not indicate in any way that the advanced nations are ready to subscribe to the United Nations protocol regarding DEW and their future use.
Concept of the DEW may have originated as early as in 212 BC in Greece, when Archimedes used polished mirrors to direct sun-light on the sails of Roman ships while defending the city of Syracuse. It was not until 1890 that HG Wells resurrected this concept in his book The War of the Worlds. And taking a leaf out of history, on May 23, 1983, Ronald Reagan the US President urged the development of a system that could intercept and destroy strategic ballistic missiles before these could reach US soil 2 or that of the US allies. He copied the idea directly from the star wars.. Enough funding was promised despite loud protests from various quarters. Subsequently, a report appeared in the IDR August 2000 issue that the DEW were well on their way towards actual deployment 3 .
High Energy Lasers
Laser (Light Amplification by Stimulated Emission of Radiation), is nothing but an atom or a molecule stimulated to reach a very high-energy state. This is done by various means like chemical reaction, electrical currents or intense light. When an atom falls to a lower energy state, it emits a photon. This photon has some finite energy and it is capable of colliding with another atom in a high-energy state and extracting another identical photon from it. This is called stimulated emission 4 . Stimulated emission of lights occurs when electrons are forced by incident radiation to add more photons to an incident beam. In a laser there are mirrors, which reflect these photons back and forth through the medium, the emission gets amplified and the escaping photons are known as the laser beam. This output beam is a light of continuous wavelength, which depends on the lasing medium being used. Laser light is highly monochromatic because it is generated by electron transitions between two narrow energy levels. As a consequence, laser light can be focused to a spot, less than 1 ìm in diameter. 5 Another outstanding feature of laser light is its strong collimation i.e. the parallel emergence of light from a laser window. 6 Therefore, it may be clearly understood that a laser weapon works by depositing intense heat energy on the target and destroying it by burning or causing fracture. Laser can be used for two types of attack, thermal and impulse. In a thermal kill, the target is destroyed by a long dwell time of the laser and burning through it. On the other hand, if a very high power laser pulse is used, it vapourises a small layer of the target skin and its surrounding air. These super heated gases expand explosively sending shock wave in to the target. Such a shock wave can destroy the skin, and is known as impulse kill. A particle beam could bore a hole in the outer shell of a missile, a satellite or an aircraft and cause serious damage to electronics inside or explode the high explosives trigger of a nuclear weapon. Such damage requires about 103 joules/cm3 deposited on the target. 7 The total energy of beam that has an angular divergence of a micro radian and can deliver that amount of energy can be generated by an accelerator that produces a particle beam pulse of 1000 amperes flux accelerated to 1 Ge V (Gega electron volt) that lasts for 100 ìsec. 8 ( One electron volt may be explained as the energy required to bring an electron from 0 volt to 1 volt).
Exoatmospheric uses of electron and proton beams will have their problems: 9
Limitations of Laser Beam
Inside atmospheric conditions the beam suffers from absorption and scattering, and becomes defocused and bent because of the properties of air. Whereas, in the vacuum of outer space the beam suffers only diffraction, which is inversely proportional to the size of the laser. There is an upper boundary of power density ( 107 /cm2) that a laser beam can transmit inside atmosphere, 12 because laser light of very high intensity can cause electrical breakdown of the air, which in turn disrupts the beam. Moreover, laser weapons efficiency while operating in the earth's atmosphere depends on local weather conditions and the presence of dust, smoke or aerosols. Application of laser for target detection and tracking would have to take these factors into consideration.
A scientific calculation based on facts can prove beyond doubt that a laser beam may not be able to melt or vapourise a metallic target very easily without disturbing the air, because the power density levels required tend to exceed the breakdown threshold of air. But there is no doubt that the most effective way to damage a target with a thin metallic skin like aircraft or missile will be by impulsive loading. Because these structures are already under severe stress, any addition to this stress need be supplied to exceed the acceptable stress of the material. Thermo mechanical damage can be caused to a target if it is exposed to a repetitively pulsed laser beam; each pulse will deposit plastic energy in the target, until an amount equivalent to the fracture energy is reached. This repetitive pulse beam exploits both thermal weakening and mechanical damage and will melt through.
Despite the UN protocol it can be safely estimated that high-energy lasers will be used in the near future for attacking targets like aircraft, satellites, ballistic missiles, and cruise missiles. And the design of these new weapons systems will depend on the vulnerabilities presented by the target. To cause maximum damage, the laser wavelength, pulse shape, energy, and beam diameter should be chosen correctly. The thermal damage to a target need not necessarily be melting. It can cause thermal damage mostly due to overheating. The energies absorbed by the target of ~103 joules/cm3 per pulse delivered in pulses of several tens of microseconds over a small area of the target will cause impulsive failure of a thin metal target. 13
There are four major types of lasers for weapon system applications. These would have differing wavelengths and differ in their output power. All of them could be employed in potential weapons systems. The types of laser are:
Despite production of high-energy laser, the fundamental requirement would be strong coupling action of the laser light to the target in order to cause any damage. This would depend on factors like wavelength, target material, and the aspect angle of the target to the beam. That is why a military application will have to take into consideration reflectivity of the beam for beam control and best absorption of the light by the target to cause maximum damage.
IDR reported that :
"US Department of Defense currently funds three kinds of device technology for High Energy Laser weapons; chemical, solid state and free electron. Chemical lasers use a chemical reaction (combustion) to provide the pumping energy. Weapon class chemical lasers include types using hydrogen fluoride(HF) and deuterium fluoride (DF) and chemical oxygen iodine lasers (COIL). These have achieved power levels of several megawatts with good beam quality." IDR August 2000. 23
Particle Beam Weapon
History of particle beam dates back to 1950s, even before the laser made its theoretical appearance. Scientists were able to accelerate charged sub atomic particles to very high speed in an accelerator. 24 And all such devices generate their destructive power by accelerating sufficient quantities of these sub atomic particles or atoms to velocities near the speed of light and focus the energy into a high energy beam. Each particle moving in the beam would have its kinetic energy due to its own mass and motion. Presently particles used to form this beam are electrons, protons and hydrogen atoms. In the case of hydrogen a single electron and a proton combination form a neutrally charged atom. Because of being neutrally charged, hydrogen atoms would not be susceptible to bending by the earth's magnetic field, which is a problem of weaponisation of particle beam (PB). In the atmosphere, charged particle beam neutralises itself by colliding with air molecules, effectively creating enough ions of the opposite charge to neutralise the beam.
To form a particle beam, an electronic accelerator should have a diode in a vacuum. A very high electrical voltage is applied across the diode, the negatively charged electrons that are emitted instead of being collected at the anode are made to pass into an accelerator. This accelerator has suitable arrangement of electrical and magnetic fields, which impart high acceleration to these electrons and can focus them also. This is a simple linear accelerator. 25 A similar process can be achieved in a circular accelerator with the electrons accelerating in circles of increasing diameters, which is known as cyclotron. Energy of the beam is expressed in electron volts, the beam current in amperes, and power of the beam in watts. The power of a PB is the rate at which it transports energy. That would give a clear idea about the rate at which the energy will be deposited on the target. The electron and protons of the beam are deposited on the target, which collide with the atoms of the target, and break the atoms like snooker balls. The area of the target where the beam has been focused will get heated up rapidly and the target will explode.
There are two types of Particle Beam Weapons. Charged particle beam weapon and the neutral beam weapon. The charged particle weapons are for use within atmosphere (endoatmospheric) and the neutral particle beam weapons are used in space (exoatmospheric). Both these weapon systems will have different characteristics of their own. 26
The fire control, procurement and tracking system of PBW must acquire and track the target, point the weapon at the target, fire the beam at the appropriate time and assess target damage. The miss distance has to be calculated and correction has to be carried out on time. Advantages of PBW: 27
Power Supply and Accelerator Technology
This is no doubt a difficult problem for the PBWs. To operate an endoatmopheric weapon, tremendous amount of electrical energy is required over a very short period of time. As power is energy divided by time, large amounts of energy over a short period of time translate into extremely high power level. Lightweight components capable of producing millions of watts will be the actual requirement of the weapon system. In addition, the accelerators create the high-energy particle beam. It is composed of a source of ions (electron, protons or charged atoms) a device injecting the particles into the accelerating section and the accelerating section itself. There are various types of accelerators, like linear, circular and radio frequency linear. As reported, Advanced Test Accelerator is designed to generate 50 Me V (million electron volt) beam with 10,000 amperes of current in pulses of 50 nano second ( 50 billionths of a second). 28
High Power Microwave Weapons
High power microwave weapons were on the drawing board for a long time. But for the first time in Kosovo war some testing could have been carried out, (as claimed by the Russians). It seems that the weapon can be delivered by cruise missile or by any other stand off platform and can be exploded within yards of a target. The explosion would be followed by generation of high power microwaves that can disable electronic circuitry in computers and communication systems. The electromagnetic pulses could create havoc to anything that is electronically operated. The EMP, which was noticed during the high altitude nuclear explosion has at last been perfected by a team of US scientists probably at Los Alamos and may add a new and unknown dimension to future wars. 29 The technology that would be used to generate the EMP is:
lExplosively pumped flux compression generator.
lHPM devices based on virtual cathode ray oscillator or vircator
lPropellant driven magneto hydrodynamic generators.
Like all other DEW, defence against such weapons systems would be very difficult to install because the capabilities of such a menace are not yet known exactly. It is very well to claim that certain amount of electronic hardening would be the solution but there are some serious limitations. It is not known whether equipment can be hardened totally or some part will remain vulnerable to electromagnetic attack. And if one part gets affected, what would happen to the equipment as a whole. Also it is quite clear that this would be the route to gain command of the electromagnetic spectrum so as to carry out subsequent operations with impunity using other conventional weapons. Subject to the lethality of the weapon, command and control system would become ineffective and cause havoc to the economic system. Effect of a massed attack with such weapons at the opening phase of the battle can only be imagined.
DEW of USA
"Lt Gen John Costello commanding general of the US Army's Space and Missile defence command describes DEW as a potentially revolutionary addition to the battlefield of the future." 30 During the frightening period of the Cold War arms race, both the superpowers generated a lot of heat by claiming the development of death ray and other DEW. But since then it was the prerogative only of USA to spend enough amount of money and time to gain superiority by gaining access to these frightful and seemingly innocent weapons systems and call for a global nuclear disarmament. It was way back in the Falkland War of 1982 that UK, an US ally employed a laser dazzler and now it has come to notice that the Chinese People's Liberation Army has deployed weapons like ZM87 laser interference device that could cause short term blindness at ranges upto 10 km. PLA's Type 98/WZ-123 main battle tank carries a turret mounted installation of a laser equipment which could be used against both ground based and air borne optical and electro optical sensors 31 . It is understood that US development of the DEW is progressing unabated despite many obstacles. And there is no doubt that US will forge ahead in this field considering the pace of the development brought out in the IDR. High Energy Laser Executive Review Panel of USA headed by the Deputy Undersecretary of Defense for Science and Technology clarified in their report that: 32
This is more or less an accurate statement because despite having a solid base in the field of physics; break up of the Soviet Union has put many impediments for the growth of this field in present day Russia. The main problem being the funding for fundamental research. The US committee while commenting on laser weapon development identified a few areas which require immediate attention and are to be supported by adequate funding: 33
Out of the many lasers, USAF research for the Air Borne Laser (ABL) 34 and Space Based Laser (SBL) System have advanced on the determined path. Large Aircraft Infrared Countermeasures programme (LAIRCOM) is aimed at arming C-17, and C130 air lifters, together with KC 135 tankers. USAF would be ready to deploy at least seven Boeing 747-400Fs with capabilities to engage ballistic missiles during their boost phase from a stand off distance of about 400 km. 35 The system is expected to be functional during the financial year 2005 and will hopefully be completed by the year 2009. The Space Based Laser (SBL) deployment will take longer than ABL. The entire system would comprise 20-40 satellites at altitudes of 700-1300 km for global coverage. The system would be able to engage any ballistic missile with a range of more than 120 km during its boost phase. 36 Each satellite equipped to carry acquisition, tracking and pointing system using low power illuminator and a high energy laser with a range of more than 3,000 km, would engage the missile. The system fits all the QR of the much talked National Missile Defence (NMD) of USA.
US Army's joint programme with the Israeli scientific community which began in 1996 has brought about the development of the Tactical High Energy Laser (THEL), which could destroy a Katyusha rocket in flight carrying a live warhead. 37 On its success, Lt Gen Costello commented that " we have just turned science fiction into reality" But it seems that the statement cannot be taken just at face value. There is a subtle warning about the US's emergence as the sole leader in the field of DEW without a challenger to be seen anywhere.
DEW of India
DEW are not mentioned in the Indian defence environment because it is more or less taken for granted that such weapon systems are beyond our means and that is why they do not feature in any of the military studies. Indian military may not be thinking of application of laser beyond laser ranging and laser designation. Recently a study has been ordered by the Chiefs of Staff Committee (COSC) to look into the feasibility of the DEW. Defence Research and Development Organisation (DRDO), the only research organisation in India serving Indian defence purposes has certain research projects on laser weapons but it is not known what the state of that research is and whether any weapon system is developed for deployment with the armed forces. But before the Indian Armed Forces can lay their hands on the DEW and employ them, they may undertake defensive measures.
Defensive Tactics Against Directed Energy Weapons
As has been already described that DEW include lasers, Particle Beam (PB) and High Power Micro (HPM) wave weapons. These weapons produce casualties and damage equipment by depositing energy on the target. Whereas, conventional weapons rely upon kinetic/chemical energy of a projectile to destroy the target. DEW depend upon sub atomic particles or electromagnetic waves impacting on the target at or near the speed of light and are expected to cause damage to soft targets like personnel, soft components of hard targets, like optics. It is expected that the equipment fielded in future wars will be built with certain amount of hardening against DEW attacks and older equipment may be refitted with protective devices. But presently the armed forces personnel should be taught to defend themselves against these weapons.
Defence against Laser
Laser systems will definitely be fielded by the enemies of Indian armed forces in some form or the other. There is increasing evidence of the presence of laser devices in the inventories of all the armed forces, like target designator or a laser range finder. And the most probable target of laser weapons will be optical and electro-optical systems, and the personnel behind the sights. A laser beam entering a direct view optical system such as a telescope will have its power magnified. Anyone looking through the system will suffer burns to the eyes. The severity of the burns, the permanence of the damage and the time required for healing will depend upon weather conditions, the intensity of the laser, magnification of the optical laser and the duration of the eye's exposure to the laser. Eye injury may range from temporary flash blinding and mild burns to total blindness. A soldier subjected to this type of injury may be incapacitated and unable to aim his weapon. It is anticipated that a laser weapon will fire at a target for a split second and aim at another. Laser weapons fired against individuals could cause burns. As the eye is more sensitive during the night, laser energy entering the eye during darkness will have a greater effect than it would during daylight. Certain forms of laser will be hazardous to soldier's eyes even though the laser cannot be seen.
A laser beam entering an electro optical device, such as night vision sights or thermal imagery device, will deposit its energy in the form of heat on the sensor screens inside. There are chances that this can burn out the screen, making the device useless. Any uncovered glass surface ( eyeglasses, vision blocks, or binoculars) has the potential to attract or alert an anti electro-optical weapon's target acquisition system. However, it is not precisely known about the effect of a laser beam on human beings.
How to avoid anti-electro-optical weapon systems:
Defence Against EMP Weapons
Electro Magnetic Pulse (EMP) can severely damage or destroy sensitive electronic equipment such as microchips, coils and fuses by overloading them with electrical current. 38 Any equipment containing electronic components is subject to damage or destruction from EMP attack. The amount of damage to equipment depends on its distance from the source of the pulse and type of hardening it had. An EMP attack lasts only for a split second and affects a large area. Protecting equipment against such an attack is extremely difficult. The only way to protect equipment would be to totally encase the equipment in a metallic shielding. Burying or covering with sandbags or other nonmetallic materials will not provide any protection. Terrain masking is also ineffective because EMP follows the curvature of the earth. While operating from combat vehicles, sensitive equipment not needed for use at the moment should be disconnected and moved to the center of the vehicle. Hatch cover should be kept closed. By doing this, only a minimum of equipment is susceptible to destruction and the remainder is available for use after the attack. Direct or indirect fire weapons within range should attack known EMP generating ground-based weapons.
Defence against PBW
Particle beam is a directed flow of atomic or sub atomic particles. When concentrated into a beam that can interact with a target it can melt or fracture target material. But it is not known whether a particle beam weapon is ready for deployment by any country. The defence against the same will be similar to that of the other DEW as discussed earlier. Commanders at all levels will have to bring awareness to their subordinates to this new dimension of threat that is emerging and will become a reality in the next round of combat.
Impact of Directed Energy Weapons
RMA is gaining ground in the thought process of the military strategists of the entire world and there is no doubt that the changes are technology and information driven. While discussing these, Kapil Kak of IDSA mentioned that;
"Technology change may well revolutionise warfare in the 21st century. Countries that can exploit emerging technologies and synergise the same with innovative operational doctrines and organizational adaptation could doubtless achieve far higher levels of relative military effectiveness." 39
Technology changes are round the corner and these would be more dangerous and more lethal than anything seen or experienced before the directed energy weapons. Neither do they make any noise nor do they inform about their deployment. The super observation capability of a nation may discover the design of an adversary but it would be very difficult to determine the time and direction of the attack and the effectiveness. For example, the EMP weapons could write off the entire computer systems and throw the command and control in complete disarray. Few military analysts know how to combat this new dimension of warfare. A complete paradigm shift is expected when the Laser and Particle beam weapons are brought in. Nuclear bombs and the perceived threat from them vis a vis these new developments have to be analysed by the military thinkers and effective action taken before being completely surprised. It would not be very easy to assess the impact of these weapons because of their peculiarities and the absence of collateral damage scenario. Collateral electrical damage is the most likely possibility. It may paralyse a nation for few days, but as long it does not affect a human being no one will raise a finger at the aggressor and. make an issue out of it. The aggressor will achieve his purpose. Nuclear doctrines, mutually assured destruction, limited response, (CTBT), (MCTR) etc will lose their relevance in the backdrop of the silent revolution of DEW. The Air Borne Laser system to be deployed by USA, with capability to destroy a missile with any range beyond 120 km at boost phase is not very far away. But the Space based laser or particle beam weapon capable of punching a hole in any missile at a range of 3000 km or more can only be analysed to an extent.
Indian military planners must take these new threats into their force structuring or else they will face a new kind of battlefield unknown to them. The concept of DEW application is like the morning star on the horizon. It looks good but is difficult to reach. The DRDO is in the process of developing some of these weapon systems but till such time it is made available with the military, the system cannot be integrated with other weapons in the inventory of the Indian Armed Forces. DRDO may carry on with their own research and will be welcomed by the armed forces if they produce something worthwhile and hand it over to the Indian military. But it would be consistent to suggest that Indian Armed Forces must have their own laboratories manned by dedicated scientists, to develop the futuristic weapons under proven military scientific leadership or else the technological world will drive past the door of the Indian military and the RMA will be the word of the analysts only. It should be understood by the Indian military system that technology driven RMA is brought about by weapons or systems exploiting powerful combinations of technologies, combined with supporting doctrine and organisation. Input process being the technology breakthrough and the output being the RMA.
Whether the current technological breakthrough in relation to DEW is real term RMA or not, cannot be defined readily now. Because after detailed strategic analysis only, can it be assessed, whether the new weapons can render obsolete or irrelevant one or more core components of a dominant player in the new dimension of warfare. But it cannot be discounted either. The cyberspace-based technologies supported by the DEW in a future conflict might inflict unacceptable damage, sufficient to significantly alter the course of the conflict. Revolution in Military Affairs is however unclear and definitely not taking a predictive course. That is why a hypothesis can only be drawn from the present about the future.
History of Laser and Particle Beam Weapons
Laser theory by Charles H Towns.
First Laser and simple laser operations.
Carbon dioxide laser Invisible beam at wavelength of 10 micrometers in the infrared. C Kumar N Patel at Bell lab 8800 watts 750 feet beam.
Gas Dynamic laser - Scalable to high energy
Chemical lasers reach high power
sLaser range finders and designators
First Military operational laser.
USAF tested shooting down of drones with laser. The project was kept secret till 1982.
US Army used 30 to 40 kW laser in a tank to shoot down helicopter drones at Red Stone Arsenal, Alabama.
US Navy demonstrated moderate power chemical laser 400 kW to shoot down a TOW antitank missile.
Alpha programme confirmed that a high-energy chemical laser could generate sufficient power to destroy a missile at a good distance. During that period it was demonstrated that large optics were possible.
USAF spent approximately $ 5.2 billion between Fiscal year 1968-2000 on applications of directed energy weapons for offensive and defensive applications and plans to invest a further $4.6 billion by financial year 2007.
USAF is continuing its development of the following projects:-
History of PBW
1958 PBW development programme initiated by DARPA projects Seesaw.
1974-1978Chair Heritage Particle Beams for US Navy. Micro explosion fuel pallets - miniature versions of hydrogen bombs. Internal Confinement Fusion simulates effects of nuclear explosion. Accelerator technology and pulsed power systems.
1977Soviet Union Particle Beam weapons for ballistic missile defense.
1983Ronald Reagan for the first time talked about rendering the nuclear missile obsolete by deployment of PBWs.
Requirements of Directed Energy Weapons
Operational Requirement for Directed Energy Weapons
DEW system must have the following:-
Some special requirement of the high-energy laser and particle beam weapons:-
Note 1: Review Conference of States Parties Conventional Weapons Convention, Vienna, September 25-October 13 "Adopts Ban on Use, Transfer of Blinding Laser Weapons" (Press Release United Nation DC/2525, October 17, 1995).Back
Note 14: Lasers that employ electrically excited gasses as the active medium have operated at the highest efficiency. The gas discharges remain optically homogeneous and virtually there is no loss at the lasing wavelength even when the optical path length is several meters long. In this context, Carbon Dioxide Lasers may be the best examples. The output of this laser could be to the tune of 9 kw of power. An electron beam can only produce this type of energy. Monte Ross Laser Applications (New York: Academic Press 1971) pp. 203-214.Back
Note 16: Solid-State Laser. The solid state optically pumped laser produces the highest energy peak power. This is possible because of very high density of laser ions available in solid materials. Concentration of ~1020 laser ions/cm3 are typical for solid hosts. Whereas gaseous lasers usually operate with lesser than ~ 1018 laser particles/cm3 . Moreover, solid laser materials can be excited very rapidly with high energy flash lamps to extract the stored laser energy in a great pulse of short duration. Ibid., pp. 212-214.Back
Note 17: Ruby Laser. Ruby was the first material in which laser action was demonstrated and has continued to be an important source of high power laser emission. It is an extremely hard and durable material with high thermal conductivity, permitting effective cooling of the laser rod. Laser actions are quite dependent upon the rod temperature, so an efficient cooling system is required for its continuous operations. Ibid pp. 215-216.Back
Note 18: YAG. A short name of Yttrium Aluminum Garnet (YAG) doped with Nd3+ (Neodium) or materials like chromium, erubrium, holium, cerium and titanium possess many favourable qualities to make them a good source material for laser. It is hard, durable and has good thermal conductivity. YAG also can be produced with excellent optical quality. The cost and its limiting size may restrict the use of YAG lasers commercially but it may be used for weapons applications. It may be pointed out that because of its unique qualities, YAG is the only solid-state laser material that has generated significant amount of continuous laser power, over 1100W at 1.06 ìm. (wavelength) Ibid., p. 218.Back
Note 19: Glass Laser. Glass lasers can produce very high-energy pulses in short length of time. Lasing strength more than 5000 J is not uncommon. Barium crown glass and high silicate glasses are commonly used doped with Nd3 ( Neodium). Glass laser rods over 72 inches in length have been fabricated with good optical qualities. Ibid., pp. 216-217.Back
Note 20: Semi Conductor Lasers. Semi conductor lasers developed recently are going to replace the gas based ion laser and other solid state lasers. Power as high as 1000 W can be achieved easily. Wavelength of these lasers can be from infrared to ultra violet range. Peltier or conventional cooling can be used for semi conductor based lasers. Power consumption is much lower than the other types of lasers and this will help much-needed miniaturisation for weapons systems of the future. RE Hunamel, Electronic Properties of Materials, (New Delhi, Narosa Publishing, 1993) pp. 245-252.Back
Note 21: Solid-state lasers also include heat capacity lasers, fiber optic lasers and continuously cooled designs. Typical criteria of certain solid-state lasers are their tenability over a large bandwidth.. Titanium sapphire lasers have the bandwidth 0.66- 1.18 microns., whereas, alexandrite ( a chromium doped crysoberyl, crystal can have the wavelengths from 0.7 to 0.82 microns. Ibid.Back
Note 22: Free Electron Lasers are high efficiency lasers and can be tuned over a broad part of the spectrum. These lasers produce their energy by passing an electron beam through a structured magnetic field. Electrons change direction sharply because of alternate magnets placed in the array which have reversed polarity and that causes the emission of the energy. Ibid.Back
Note 27: Dr. Richard M Roberds "Introducing the Particle beam Weapon" pp. 3-5. <http://www.airpower.maxwell.af.mi./airchroniocles/aureview/1984 jul-aug/roberds.htm>Back
Note 34: Ibid. p.37 "the ABL has passed its critical design review in April. The PDRR phase includes the installation of a half power (14 module) laser in a 747-400 test aircraft, which began an 18 month modification program in January. Installation of ABL system components is due to start at Edward Air Force Base, California, in July 2001."Back
Note 37: Ibid., p. 38-40 "" High Energy Laser System Test Facility ( HELSTF) at White Sands Missile Range in New Mexico integrate the SSL at HELSTF for testing and evaluation and demonstrated the effectiveness of lasers against short-range rockets."Back
Note 38: Ibid., p. 39 "" pulsed power includes the design and construction of compact Marx Banks, together with explosive magnetohydrodynamic and maganetocumulative generators.""explosive flux compression generators could typically provide up to 100 MJ and 100 MA, using up to 450 kg of high explosives per shot"Back