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United States Patent to 11, 4,011,116 Lee Et Al United States Patent to 11, 4,011,116 Lee et al. (45) Mar. 8, 1977 (54) CARBON DIOXIDE LASER FUELs (56) References Cited 76 Inventors: Lester A. Lee, 405 River Wood UNITED STATES PATENTS Drive, Oxon Hill, Md. 20022; Edward E. Baroody, 189 Bucknell 3, 173,921 3/1965 Einberg ............................... 149123 Road, Bryans Rd., Md. 20616 Primary Examiner-Stephen J. Lechert, Jr. (22 Filed: Dec. 6, 1974 (21) Appl. No.: 530,260 57 ABSTRACT (52) U.S. Cl. ................................... 149/46; 149/45; Gas dynamic and hybrid gas dynamic-transfer chemical 149/74; 49/75; 149/76; 149183; 149/88 laser systems are achieved by burning halogenated or (51 int. Cl.......................................... C06B 31/28 deuterated tetrazoles in the presence of an oxidizer. 58 Field of Search .................. 149/45, 75, 23,92, 149/46, 76, 74, 83, 85 13 Claims, No Drawings 401 1,116 1 2 at the precise angle with the desired velocity at the CARBON DOXIDE LASER FUELS right temperature to react to produce the desired laser The invention described herein may be manufac characteristics. These parameters are only a few of the tured and used by or for the Government of the United parameters which must be controlled in order for a States of America for Governmental purposes without chemical laser to function. Controls on each of the the payment of any royalites thereon or therefor. parameters are highly complicated in themselves and must be integrated with other complicated controls to BACKGROUND OF THE INVENTION produce the laser beam. All of these complications This invention relates to lasers, and more particularly substantially affect the use of the chemical laser. to a haolgenated or deuterated tetrazole suitable for O Simplest of the three types of lasers to use is the use as a fuel to generate a laser of the gas dynamic thermal or gas dynamic laser. This laser produces the transfer chemical type. laser beam by means of a rapid gas expansion. This type Laser is an acronym for light amplifications by stimu of laser is simplest to handle because the reactants are lated emission of radiation. A laser produces a beam in generally solid or liquid and easier to handle and store. the spectral region broadly defined as optical. The laser 15 However, finding reactants to produce laser action is beam is coherent electromagnetic radiation having a difficult. particular well defined frequency. Coherence is a Laser action occurs when two conditions are met: (1) unique feature of the laser because the optical range population inversion is achieved and (2) avalanche which includes the near ultraviolet, the visible, and process of photon amplification is established in a suit infrared wave lengths is incoherent. So ordinary light is 20 able cavity. Population inversion is established in an incoherent while lasers are coherent. Because of coher atomic system having at least one ground level, and at ence, lasers have extremely small divergence and are least two excited levels wherein one of the excited highly directional. Also enormous power is generated levels has a longer spontaneous emission lifetime than in a very small wavelength range. This power can be the other excited level. Inversion permits stimulated focused on a spot having a diameter of the wavelength 25 emission to exceed absorbtion which results in photon itself, and is capable of producing from a 50 kilowatt amplification. A more thorough discussion of laser outburst a radiant power density of 10' watts per action is found in U.S. Pat. No. 3,543,179 to Wilson square centimeter which is about 10 times the power incorporated herein by reference. density at the surface of the sun. Such power has many In spite of the difficulties involved in achieving a laser uses such as testing materials, welding, drilling or mili 30 beam, the power of the laser beam renders the field tary applications. Because of the power produced, highly fertile for research. Some of the areas most fer much research has been directed to the laser field. tile are those which simplify the generation of a laser There are two basic types of lasers known as the solid beam. The above-mentioned electrical discharge la state laser and the gas laser. The solid state laser has a sers, chemical lasers, and gas dynamic lasers are highly low energy when compared to the gas laser, because it 35 complex means of generating the desired laser beam. produces a laser beam by electronic excitation of crys Efforts in the thermal laser field are made because of talline materials and is a rather complex system, as the simple operation. However, thermal generation of a exemplified by the ruby laser. Due to the lower energy, laser beam is difficult. Chemical gas generation is a coherence is an important feature of the laser beam well-known method of simplifying a gas laser-genera produced in the solid state laser. Gas lasers, on the 40 tion process. The problem now becomes selecting an other hand, have such relatively high energy that co appropriate fuel or chemical which produces the herence is neither achieved as well nor made as impor proper gas for rapid thermal expansion when reacted or tant in the lower energy solid state laser. burned. There are three basic types of gas lasers. Electric It is possible to pump gas dynamic lasers by use of discharge, gas dynamic, and chemical lasers are known 45 hydrocarbon/air mixtures. These mixtures are ignited types of gas lasers. The basic physical process common in a combustion chamber and then allowed to expand to them is the competition between stimulated emission through a supersonic nozzle so that population inver and absorption of monochromatic radiation, where the sion occurs. Theoretically, the efficiency of the laser radiation energy corresponds to the difference between increases with increasing combustion pressure and two distinct energy levels of an atomic or molecular 50 temperature, and with increasing expansion ratio. The system. In chemical lasers, the products of highly ener combustion products must contain a high percentage of getic chemical reactions are formed directly in vibra nitrogen, and approximately 10% to 15% carbon diox tionally or electrically excited states with the upper ide, and some percentage of water vapor. In addition, levels preferentially populated. In gas dynamic lasers, the combustion products should not contain any solid an initially hot gas in thermodynamic equilibrium is 55 particles or highly corrosive gases; however, gases such rapidly expanded through a supersonic nozzle, and an as carbon monoxide and oxygen do not seem to be inversion is formed by differential relaxation processes detrimental to the optical gain. These requirements in the non equilibrium nozzle flow. In electric discharge rule out the use of conventional explosives such as lasers, the upper energy level is preferentially popu trinitrotoluene, nitrocellulose, and the like, as well as lated by collisions with electrons within a gas mixture 60 double-base and composite propellants. For military energized by an electric field. applications, lasers must meet rigid requirements such The laser effect in electric discharge lasers is pro as safety, storage, handling, and non-toxicity. duced by funneling the gas through an electric field to Additionally, for military applications, only solid achieve the desired excited level and produce a laser propellants are considered to generate the laser gases beam. High energy levels are required to excite the gas 65 mentioned above. The propellant would consist of only to laser producing levels. the elements carbon, hydrogen, oxygen, and nitrogen. Chemical lasers depend on a carefully monitored However, solid organic compounds that can produce flow of gases which intersect at precisely the right point high nitrogen, low carbon dioxide and water upon 401 1,116 3 4 burning are usually unstable, toxic, and hard to store, Another object of this invention is to provide a fuel especially in large quantities. They also have high com composition suitable for generating a laser beam. bustion temperatures that are difficult to use with laser These and other objects of the invention are met by equipment, providing a laser fuel comprising a halogenated or deu Gas dynamic and chemical lasers are similar in that 5 terated tetrazole and burning the fuel with an oxidizer both depend upon competition between stimulated to produce a gas which excites at least one molecule of emission and radiationless relaxation processes. Sev- at least one other gas to laser activity. eral publications have described the operation of gas dynamic lasers by the combustion of fE. E. DESCRIPTION OF THE PREFERRED tures in a combustion chamber. The hot gases in ther- 10 EMBODIMENT mal equilibrium are allowed to expand through a super- A gas such as carbon dioxide is excited to laser activ sonic nozzle so that population inversion occurs. The ity by a gas or gases produced from the burning of at inverted N. pumps the CO. least one tetrazole with at least one oxidizer. One disadvantage of the N-CO-He GDL is that The phenomenon of one gas causing laser activity in 60%. He with 30% N is required for maximum power. 15 another gas is known as the gas dynamic transfer chem Helium acts as a diluent and a relaxant for the CO ical laser. The gas dynamic transfer chemical laser uses lower laser level. The replacement of He with a more non-thermal vibrational energy of chemical reaction efficient relaxor such as % HO allows more N for products to create a total population inversion in a pumping. The 89% N - 10% CO - 1% HO system second molecule such as carbon dioxide, thereby creat which is one of the best, has the disadvantage of being 20 ing a transfer of energy.
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