Abstract:
The present inventions pertain to a method of applying a solid protective coating to articles, to a system capable of depositing a solid film layer on articles, and to hermetically sealed articles. In particular, films are deposited on fused quartz substrates, optical fibers, and other items requiring a hermetic seal by a single or multiple beams laser-induced chemical vapor deposition [LCVD]. According to the present inventions, the protective layer can be deposited on the articles to be hermetically sealed in an open environment at atmospheric pressure and ambient temperature whereby the coating process may occur outside the confines of an enclosure. A coaxial precursor and non-reactive laminar gas jet configuration insulates the deposition area from oxygen and other aerial impurities. Moreover, the present inventions insulate items from corrosion resulting from hydrogen or water penetrating the items&#39; surfaces, maintain the items&#39; mechanical properties, and preserve the integrity of optical signal transmission of optical fibers.

Description:
STATEMENT AS TO FEDERALLY SPONSORED RESEARCH 
     The present inventions were developed pursuant to Grant # N00014-01-1-0691 awarded by the Office of Naval Research. The Government of the United States of America has a paid-up license in this invention and the right in limited circumstances to require the patent application owner to license others on reasonable terms as provided for by terms of the aforementioned Grant. 
    
    
     BACKGROUND OF THE INVENTIONS 
     1. Field of the Inventions 
     The present inventions pertain to a method of coating articles; particularly, to a process by which objects are coated with carbon or silicon carbide using laser-induced chemical vapor deposition at atmospheric pressure and ambient temperature. Additionally, the present inventions relate to objects such as optical fibers that are protected from environmental corrosion by an insulating film that is applied in an open-air environment. 
     2. Description of the Related Art 
     The process of applying a carbon film to a bare optical fiber in order to hermetically seal the fiber is constantly evolving. Generally, all types of optical fibers share the same basic structure; namely, a core with a high refractive index and a surrounding cladding region with a lower refractive index. In a typical single mode optical fiber, the cladding is approximately 125 μm in diameter, while the core is approximately from 4 to 8 μm in diameter. The core and cladding are indistinguishable to the naked eye and appear as one strand of glass 125 μm in diameter. A carbon coating, which is approximately 50 to 150 nm thick, is deposited onto the cladding. Then, polymer coatings, which are on the order of 10 μm thick, are deposited on top of the carbon coating. Optical fibers are typically forged from a pure glass material, such as fused silica or fused quartz. Then, small impurities and anomalies are introduced into the material in order to obtain the desired refractive indices. The difference between the refractive index of the core and of the surrounding region facilitates the transmission of a signal along the length of the optical fiber. In order to preserve the integrity of transmitted signals and optical fibers&#39; mechanical properties, a protective carbon film is typically applied to the external surface of optical fibers. 
     The system for applying a coating, film, layer, or sheath can also be used to coat the exposed section of the spliced optical fiber. Optical fiber can only be manufactured in finite lengths. However, there are scenarios such as long distance optical communication lines in which it may become necessary to join multiple fibers in order to produce a fiber longer than can be manufactured as a single strand. Two optical fibers can be joined together by a process called fusion splicing. Fusion splicing is the controlled aligning, melting, and pushing together of optical fibers resulting in a transparent, non-reflective joint. After fusion splicing an optical fiber, a section of the optical fiber is exposed such that the glass core is unprotected from environmental corrosives. 
     Yamauchi, in U.S. Pat. Nos. 5,223,014 and 5,360,464, discloses a technique for reinforcing and applying a carbon coating to the joint between carbon coated fibers. Yamauchi&#39;s process discloses splicing optical fibers in sealed chamber filled with inert gas at a temperature between 700° and 1000° C. using a single laser beam passing through a lens to heat the environment. After the optical fibers have been joined, a reactant hydrocarbon gas is pumped into the chamber so that a reinforcing carbon layer is deposited on the fusion spliced part. 
     One of the methods by which a carbon sheath is applied to a bare optical fiber is chemical vapor deposition. Chemical vapor deposition is a chain of chemical reactions which transform the gaseous molecules of a precursor gas into a thin film, on the surface of a substrate. Traditionally, the application of a carbon coating to optical fibers by chemical vapor deposition required the use of a furnace and a heated chamber. A precursor gas with carbon as one of its components is pumped into the chamber. Then, an optical fiber is drawn into the chamber. A furnace is used to heat the gas mixture and the optical fiber inside of a chamber to a temperature sufficiently high to result in the decomposition of the precursor gas. Chemical reactions that produce the carbon coating can also result from mounting the reaction chamber on a tower right below the furnace. As the optical fiber is drawn through the reaction chamber, its residual heat from the fiber draw will provide the thermal energy necessary for deposition to occur. Consequently, a carbon film is deposited on the optical fiber&#39;s surface. 
     Moreover, some chemical vapor deposition reactors utilize vacuum chambers. The vacuum chamber can serve three purposes. First, a decrease in the reaction enclosure&#39;s pressure results a more uniform coating, but at much lower deposition rates. The deposition rate of a system is measured in terms of either the thickness of the layer deposited on the article to be hermetically sealed divided by the time required to deposit a layer of desired thickness or the desired mass of the solid deposit material divided by the amount of time required to deposit such mass. 
     Unfortunately, all thickness and mass measurements must be made after completion of the coating process. The thickness of the deposited protective layer or diameter of the deposited layer can be determined by examining a cross-section of a coated optical fiber under an electron microscope with a resolution on the order of 10 nm. Due to the difficulty of obtaining a precise thickness distribution, several thickness measurements are taken across a radial cross-section. Using the average thickness measurement and assuming a constant mass density, 2.21 g cm −3  in the case of pure carbon, the total mass of the deposited film may be calculated. 
     Secondly, by extracting a substantial portion of the air out of the reactor, the risks of the insulating carbon layer containing impurities or not being hermetically sealed are reduced. Thirdly, the carbon film can oxidize or the precursor gas can burn when exposed to the atmosphere at temperatures required for deposition. The minimization of impurities in the carbon film and the reduction of the film&#39;s porosity provide increased protection from corrosion of the optical fiber due to contact with hydrogen, water, and other environmental contaminants. However, the utilization of a furnace, a vacuum chamber and vacuum pump, or both makes the application system bulky, inconvenient to relocate, and expensive to operate. 
     For this reason, some conventional carbon coating applicators use a laser to heat an optical fiber and thermally decompose only the precursor gas that is in the vicinity of the optical fiber. While utilizing a laser as opposed to a furnace reduces the size and weight of the necessary equipment, the optical fiber section to be coated is placed in a vacuum chamber in order to prevent aerial impurities from compromising the integrity and from destroying the protective properties of the carbon film. Moreover, the prior art discloses processes of carbon coating optical fibers which are performed at pressures dramatically below atmospheric pressure due to vacuum extraction. 
     Alternately, some prior art also discloses pumping an inert gas along with the precursor gas into the reaction chamber after a vacuum pump has extracted the majority of the air from the chamber. However, these conventional systems, which apply a carbon coating to optical fibers using either chemical vapor deposition [CVD] or laser-induced chemical vapor deposition [LCVD] still require at least a reaction chamber and vacuum pump. 
     Therefore, previous chemical vapor deposition processes have required bulky and expensive reaction chambers in order to control the system&#39;s pressure, temperature, and atmospheric composition. 
     SUMMARY OF THE INVENTIONS 
     An object of the present inventions is eliminating the necessity of using a closed chamber to regulate pressure, temperature, surrounding gas composition or all three parameters when applying a carbon film to articles. 
     Another object of the present inventions is to increase the ease of mobility of a carbon coating application system for objects. 
     Yet another object of the present inventions is to deposit a carbon layer on items by a more cost efficient method. 
     A further object of the present inventions is to increase the rate at which articles can be coated. 
     Another object of the present inventions is to facilitate the ease with which a protective layer can be applied to objects. 
     An additional objective of the disclosed inventions is to insulate items from aerial impurities during the carbon application process by utilizing jets of non-reactive and precursor gases; whereby, a precursor gas jet is peripherally enclosed by a non-reactive gas jet. 
     A further object of the current inventions is to coat articles with a carbon sheath at atmospheric pressure and at ambient temperature. 
     Yet another object of present invention is to deposit a carbon layer on optical fiber without inducing signal attenuation to the fiber. 
     These and additional objects of the inventions are accomplished by an open-air LCVD system for carbon coating objects. The process deposits on an article a protective film which insulates the article from water, oxygen, and other environmental contaminants. The deposition method relies upon a curtain of non-reactive gas peripherally enclosing a precursor gas jet. Through laser heating the surface of the article, the deposition area can be well-defined which is advantageous; particularly, for fusion splicing optical fibers. Since the process can be performed at atmospheric pressure and ambient temperature without the use of a reaction chamber, hermetic sealing can be performed by a system which is mobile, fast, and inexpensive to operate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present inventions can be more completely understood by considering the following Description of the Preferred Embodiments and the accompanying figures. The specification of U.S. Provisional Patent Application No. 60/491,960 filed Aug. 4, 2003 by the instant inventors is a related application and is expressly incorporated herein by reference thereto. The article by the instant inventors entitled  Open - air carbon coatings on fused quartz by laser - induced chemical vapor deposition , Carbon 41 (2003) pages 673-680, is also expressly incorporated herein by reference thereto. In the figures, like numerals in different figures represent the same structural components or elements. The representations in each figure are diagrammatic and are not depicted to actual scale or precise ratios. The proportional relationships between structural components and elements are approximations. 
         FIG. 1  is a schematic drawing of a system for manufacturing carbon-coated optical fibers in accordance with the present inventions. An internal cross-sectional view of the base is represented. 
         FIG. 2  is a schematic drawing of an alternate embodiment of the present inventions in which the base in the system for manufacturing carbon-coated optical fibers depicted in  FIG. 1  is asymmetric. 
         FIG. 3  is a schematic drawing of an alternate embodiment of the present inventions in which the base in the system of apparatus for manufacturing carbon-coated optical fibers depicted in  FIG. 1  has multiple compartments for precursor gas. 
         FIG. 4  is a schematic drawing of an alternate embodiment of the present inventions in which the base in the system of apparatus for manufacturing carbon-coated optical fibers depicted in  FIG. 1  includes a compartment for precursor gas that is not parallel to the vertical axis. 
         FIG. 5  is a schematic drawing of the test cell assembly depicted in  FIG. 1 . 
         FIG. 6  is a plan view of the surface of the test cell depicted in  FIG. 5 , through which the jets of non-reactive and precursor gas are expelled. 
         FIG. 7  is a schematic drawing depicting the method by which the temperature at the deposition site is measured and maintained constant within a range of ten degrees Kelvin. 
         FIG. 8  is a concentric drawing of an optical fiber that has been coated with a carbon film according to the process described by the present inventions. For some cases, an intermediate silicon carbide (SiC) layer was observed. 
         FIG. 9  shows the cross-section of a carbon film deposited on a fused silica optical fiber as viewed using an environmental scanning electron microscope [hereinafter referred to as ESEM]. 
         FIGS. 10 and 11  illustrate the method by which the beam from the monochromatic coherent light source passes through multiple beam splitters, mirrors, and focusing lenses in order that beams of substantially equal power are focused approximately equidistant around the periphery of an optical fiber. In this configuration, two, three or four laser beams heating can be use to heat the optical fiber. 
         FIG. 12  is a cross-sectional view of a quartz tube which contains an electric switch and has been coated with a carbon layer according to the method described by the present inventions. 
         FIG. 13  is a planar view of an electronic microchip hermetically sealed between two silicon wafers by application of a protective carbon film along the seam between the wafers by the process described by the present inventions. 
         FIG. 14  is a graph of the amount of signal loss in dB (Decibel) in of the optical fiber induced by the LCVD process at different film deposition temperatures. No signal attenuation was observed at the range of desirable deposition temperature. 
         FIG. 15  shows the cross-section of a silica carbide thin film deposited on fused quartz as view by the ESEM. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to the present inventions, a system for applying a coating, film, layer, or sheath to an item helps to insulate the item from corrosion resulting from exposure to water or hydrogen penetration while simultaneously maintaining the objects&#39; mechanical properties and the signal integrity of optical fibers. By administering a protective layer to an optical fiber, neither the integrity of the transmitted signal nor the fiber&#39;s mechanical strength will be compromised. 
     The application process depends on the use of multiple laminar gas jets arranged in a configuration such that inner gas jets, of which there is at least one, are surrounded by an outer gas jet. The jets of gas pass through a mesh material in order to maintain steady and laminar streams. The aperture size of the mesh material is selected such that the interior jets encircle the article to be coated and the exterior jet provides insulation from aerial contaminants and impurities. A coaxial circle configuration with a single inner gas laminar jet is preferred; however, any configuration in which the inner gas jets are peripherally surrounded by the outer gas jet is acceptable. At least one inner gas jet emits a precursor which pyrolyzes to form the carbon film. In laser-induced chemical vapor deposition, a precursor gas, in the heated region, decomposes into a solid deposit, which affixes to the article to be hermetically sealed, and gaseous molecules by thermally driven chemical reactions. Examples of precursor gases suitable for use in laser-induced chemical vapor deposition include hydrocarbon, halides, carbon tetrachloride gases available from Dow Corning located in Midland, Mich. (trimethylsilane, dimethyldmethane, tetramethylsilane, and tetramethylcyclotetrasiloxane), gases available from Starfire Systems located in Watervliet, N.Y. (hydridopolycarbosilane, SP-4000, SP-2000, methylhydridopolycarbosilane [SiMe(H)CH 2 ] n , and 1,1,3,3-teramethyl-1,3-disilacyclobutane [Ch 2 SiMe 2 ] n ), and other similar gaseous chemicals. An outer gas jet emits a non-reactive gas which insulates the pyrolitic reaction from oxygen and other contaminants found in the air, therefore, eliminating the need for a vacuum chamber. When at a temperature less than or approximately equal to the temperature at a deposition site on the article and atmospheric pressure, a non-reactive gas will not react with the elements and gases present in the precursor jet, article to be coated, and the atmosphere; for example, non-reactive gases such as nitrogen, helium, neon, argon, and other inert gases. 
     According to the present embodiment, at least one monochromatic coherent light source, such as a laser, is focused on a deposition site, the heated section of an article located within the stream of precursor gas. The monochromatic coherent light source&#39;s power level is sufficient to provide enough thermal energy to heat a section of the article such as a stationary or moving optical fiber and the precursor gas in proximity to the article to a sufficiently high temperature to pyrolyze a precursor gas and result in deposition of a hermetically sealing coating. A sufficiently high temperature is the minimum temperature at which the precursor gas will at atmospheric pressure at least partially thermally decompose into hydrogen, carbon, and simpler precursor molecules. The most common hydrocarbon products are methyl radicals (CH 3 ), ethylene (C 2 H 4 ), and acetylene (C 2 H 2 ). Subsequently, the carbon molecules chemically bond with the surface of the article. Finally, the process may be repeated until the entire surface area of the article is covered by a protective carbon layer which has a thickness substantially between about 30 and 5,000 nm. The range of carbon layer thickness that can be obtained is about 30 to 5000 nm. According to the preferred embodiment, the velocity of the inner hydrocarbon gas jet is in the range of about 1 to 100 cm/s. But the most effective velocity is about 10-30 cm/s. The ratio of the diameter of a non-reactive gas conduit to the diameter of precursor gas conduit is between 8 to 14 for safety and effectiveness reasons. For example, if the inner diameter is 3 mm and the ratio is 10, then the outer diameter is 3*10=30 mm. In the preferred embodiment, the velocity of second conduit is always greater than or equal to half of the inner conduit hydrocarbon jet velocity. The draw rate for the moving article such as an optical fiber should be sufficient to allow uniform coating of the article. The preferred draw rate or velocity range of the linear traverse mechanism (include the V groove) is about 0.01 to 5 cm/s. For glass rod diameters of about 0.1 to 3 mm and laser power up to 25 W focused down to about a one mm laser spot, the system will work most effectively with a linear velocity of the traverse mechanism at the range of about 0.1 to 1 cm/s. According to the preferred embodiment a rack and pinion system provides mechanical motion to the linear traverse mechanism. The linear traverse mechanism must move the article or optical fiber at a linear velocity sufficient to permit uniform coating of the hermetically sealing material without altering the optical properties of the fiber to excess heat from the laser. In the preferred embodiment, the rack and pinion system includes a machined nylon 14½ degree pressure angle spur gear and rack. The pitch of the gear rack and the spur gear must have substantially the same value. The instant inventors used a pitch of 32 in the preferred embodiment of the rack and pinion system. The rack is attached to the side of the linear traverse mechanism and the spur gear is attached to the motor shaft. The spur gear teeth mesh with the teeth on the rack. According to the preferred embodiment, the inner nozzle (conduit) is about 4.2 mm and is made out of 6.4 mm (0.25 in) outer diameter (OD) stainless steel tubing. The outer nozzle diameter is preferably an annulus having a 6.4 mm inner diameter (ID) and 52.3 mm OD. The ID wall of the outer nozzle is defined by the inner nozzle, which is preferably composed of stainless steel (SS) tubing, and the OD of the outer nozzle is preferably made out of aluminum stock. Honeycomb mesh is inserted into the annulus, with pentagon shape and longest spacing of 3.5 mm. The honeycomb mesh is used to fix the location of the inner nozzle relative to the outer nozzle. Gas jet oscillation and turbulence is a fluid mechanics phenomenon that occurs when the jet flows at a high enough velocity into a quiescent medium. Friction between the moving gas and surrounding stationary air will cause the flow to destabilize. This phenomenon can be quantified by the Reynolds number (Re), in which Re is proportional to the velocity and gas jet diameter, and inversely proportional to the gas dynamic viscosity. So, above a critical value of Re, jet oscillation and/or turbulence will occur. To prevent or minimize the effects of oscillation and/or turbulence, one can either reduce the velocity of nozzle flow or reduce the diameter of the nozzle, thereby reducing Re below the critical value. The critical Re is highly specific for different flow configurations. When oscillation occurs, the gas jet will dance from side to side, which is very undesirable since the jet may dance out of the deposition zone. Turbulence also occurs at high gas jet velocity, which will increase the possibility of mixing impurities such as oxygen with the contents exiting the jet. In order to avoid oscillation and turbulence, the inner hydrocarbon gas jet velocity should be kept in range of about 1-100 cm/s for a jet diameter of about 4.2 mm and gas precursors considered. 
     Therefore, the application process, in accordance with the present embodiments, can be performed in an open-air environment. By eliminating the need for a vacuum chamber or a furnace, the amount of equipment needed is decreased so that the present embodiment is more mobile and cost-efficient methods of carbon coating objects. 
     The term “open-air” as used herein relates to a carbon or other material coating application system in which an article such as an optical fiber is insulated from contamination caused by oxygen and other impurities in the air by a curtain of non-reactive gas emitted from gas jets rather than by use of a vacuum chamber, furnace, or similar enclosure. Additionally, “open-air” refers to a system operating at atmospheric pressure and ambient temperature. 
     As illustrated in  FIG. 1 , the primary components of the open-air carbon coating system are a base  113 , a monochromatic coherent light source  111 , an exhaust hood  110 , a first conduit  105 , a second conduit  102 , precursor gas supply  103 , non-reactive gas supply  100 , and a dual-colored pyrometer  106 . The base  113  is a rectangular cube manufactured from aluminum or an aluminum alloy. 
     The interior of base  113  is separated into an inner compartment  115  and an outer compartment  116 . The inner compartment  115  extends the entire height of the base  113  such that the outer compartment  116  completely surrounds the inner compartment  115 . The inner compartment  115  of the base  113  communicates with a first gas flow regulator  108 . The outer compartment  116  of the base  113  communicates with a second gas flow regulator  101 . The first gas regulator  108  connects to a supply of precursor gas  103  with stainless steel tubing. The second gas regulator  101  connects to at least one supply of non-reactive gas  100  via stainless steel tubing. 
     The precursor gas supply  103  and the non-reactive gas supply  100  are pressurized up to approximately 2000 psi. However, a two-stage regulator is used to reduce the pressure to less than approximately 10 psi. The linear velocities at which the precursor gas and the non-reactive gas as they exit through the first conduit  105  and second conduit  102  respectively are controlled using a needle valve. The needle valve for each type of gas is adjusted so that slight pressure upstream of the tubing will force gas through the first conduit  105  and second conduit  102 . The precursor gas is pumped into the inner compartment  115  and expelled through a first conduit  105  located in the top surface of the base  113  at a velocity between approximately 1 and 100 cm s −1  in which range the precursor gas stream will most effectively operate between 10 and 30 cm s −1 . 
     The diameter of the first conduit  105  needs to be larger than the optical fiber  104  in order to fully encompass the optical fiber  104  with the precursor gas during deposition. The non-reactive gas curtain needs to be sufficiently thick to: (1) prevent impurities from entering the deposition zone; (2) prevent oxygen from entering the deposition zone where it can burn the coating  114  and/or ignite the precursor gas; and (3) cool the optical fiber  104  enough as it moves out of the deposition zone so that the coating  114  does not burn. The ratio of the diameter of the first conduit  105  to the diameter of the second conduit  102  will depend on (1) the gas flow rates since unsteady or turbulent flow can entrain oxygen or impurities from outside, the non-reactive gas jet can oscillate to the point that it does not encompass the precursor gas jet, and oxygen and impurities can diffuse through a slow flowing gas stream; and (2) how effective the non-reactive gas is in cooling the moving article such as an optical fiber. However, in order for the system to operate most effectively, the ratio of the diameter of the second conduit  102  expelling the non-reactive gas to the diameter of the first conduit  105  expelling the precursor gas should approximately be between 8 and 14. The precursor gas conduit can have a diameter approximately between 3 and 5 mm. The non-reactive gas conduit can have a diameter substantially between 39 and 65 mm. 
     The non-reactive gas is pumped into the outer compartment  116  and expelled from the top surface of the base  113  through a second conduit  102  at a velocity substantially equal to at least half of the velocity of the precursor gas. The linear velocities at which the precursor gas and the non-reactive gas exit through the first conduit  105  and second conduit  102 , respectively, are each controlled by a needle valve. The needle valve for each type of gas is adjusted so that slight pressure upstream of the tubing will force gas through the first conduit  105  and second conduit  102 . Finally, the exhaust hood  110  draws in the non-reactive and remaining precursor gases expelled from the second conduit  102  and the first conduit  105 , respectively. 
     As an optical fiber  104  passes through the system as depicted in  FIG. 1 , the optical fiber  104  enters the curtain of non-reactive gas created by the expulsion from the second conduit  102 . The optical fiber  104  then passes into the stream of precursor gas escaping through the first conduit  105 . The optical fiber  104  is insulated from contamination caused by oxygen and other impurities in the air by the curtain of non-reactive gas created by expulsion of the non-reactive gas from the second conduit  102 . As the optical fiber  104  passes through the stream of precursor gas being emitted from the first conduit  105 , a monochromatic light source  111  produces a beam  107  which is focused on the segment of the optical fiber  104  over which precursor gas is blown. Subsequently, the beam dump  109  absorbs the portion of the beam  107  not intercepted by the optical fiber  104 . 
     Additionally, a dual-color pyrometer  106  measures the temperature of the surface of the optical fiber  104  where the beam  107  strikes the optical fiber  104 . The pyrometer  106  transmits the temperature measurement to a computer  112  on which LabVIEW PID Controller software is installed. Ideally, the temperature of the optical fiber  104  within the stream of precursor gas remains within an approximately 10 K range. Thus, if the temperature measured by the pyrometer  106  is outside the acceptable temperature range, the computer  112  alters the power of the monochromatic coherent light source  111 . 
       FIGS. 2-4  illustrate alternate embodiments of the base of the carbon coating system depicted in  FIG. 1 . Second conduit  202 , first conduit  205 , and outer compartment  216  are otherwise identical to their  FIG. 1  counterparts.  FIG. 2  shows a base  213  in which the inner compartment  215  containing precursor is positioned off-center with respect to the base  213  as a whole.  FIG. 3  shows a base  313  which has multiple precursor compartments  315 . Second conduit  302 , first conduit  305 , and outer compartment  316  are otherwise identical to their  FIG. 1  counterparts.  FIG. 4  shows a base  413  in which the precursor compartment  415  is at a non-zero angle to the vertical axis. The angle to the vertical needs to be sufficiently small such that the precursor gas emitted from the inner outlet  405  is completely peripherally enclosed by the non-reactive gas emitted from the outer outlet  402 . Outer compartment  416  is otherwise identical to its  FIG. 1  counterpart. 
       FIG. 5  depicts how an optical fiber  504  moves through the carbon coating application system. A V-groove clamp  550  grips the optical fiber  504 . The clamp  550  traverse a linear mechanism track  551  by means of a rack and pinion connection  552  rotated by a motor  553  along a series of ball bearings  554 . The pitch of the rack and pinion connection  552  and of the track  551  are equal to each other. The linear motion of the clamp  550  moves the optical fiber  504  into the region of non-reactive gas expelled from outer conduit  502  in a base  513  and then into the precursor gas stream emanating from the inner conduit  505  in the base  513 . Once a segment of the optical fiber  504  is in the precursor gas jet, a beam  507  from a monochromatic coherent light source  511  is focused on the segment. As the beam  507  heats the surface of the optical fiber  504 , the precursor gas thermally decomposes, and carbon then chemically bonds with the optical fiber  504  depositing a carbon film  514  on the optical fiber&#39;s  504  external surface. Finally, an exhaust hood  510 , which is positioned above and substantially parallel to the top surface of the base  513 , draws in the non-reactive and precursor gases expelled from the outer conduit  502  and inner conduit  505  respectively. 
       FIG. 6  depicts a plan view of the top surface of a base  613  as illustrated in  FIG. 5 . In this embodiment, a non-reactive gas conduit  602  and a precursor gas conduit  605  are in a coaxial configuration. Non-reactive gas is ejected from the entire shaded region  602 , which is the non-reactive gas conduit; while, precursor gas is ejected from the complete shaded region  605 , which is the precursor gas conduit. A bare optical fiber  604  passes through the curtain of non-reactive gas expelled from the exterior gas conduit  602  and into the precursor gas jet exhausted from the interior gas conduit  605 . The segment of the optical fiber  604  within the precursor gas jet is struck by a monochromatic light beam  607  which heats the surface of the optical fiber  604 . The coherent monochromatic light beam  607  can also strike upstream of the precursor gas jet, as long as the optical fiber  604  is at a sufficiently high temperature to deposit a carbon coating when exposed to the precursor gas jet. Energy from the beam  607  causes the precursor gas to decompose into smaller molecules. The carbon molecules then chemically bond with the optical fiber  604  thus creating a protective carbon sheath  614  bonded to the exterior of the optical fiber  604 . 
       FIG. 7  illustrates a method by which a computer  712 , on which LabVIEW PID Controller software is installed, and a dual-color pyrometer  706  measure and adjust the temperature of an optical fiber  704  at a deposition site  721 , which is defined by the location where a beam  707  from a monochromatic coherent light source  711  hits the optical fiber  704 . The dual-color pyrometer  706  measures the temperature of the surface of the carbon film  714  on the optical fiber  704  at a monitoring site  723 , which is defined as the point at which the pyrometer  706  is focused on the optical fiber  704 . The offset distance  722  between the deposition site  721  and the monitoring site  723  is on the order of millimeters. The temperature measurement made by the pyrometer  706  is transmitted to the computer  712 . If the temperature reading is outside of a specified temperature range of approximately 10 K, the computer  712  communicates with the monochromatic coherent light source  711  and adjusts the power of the monochromatic light source  711  accordingly. 
       FIG. 8  is cross-sectional view of a sample optical fiber  804  to which a carbon sheath  814  was applied in accordance with the present embodiment. An intermediate layer  824  between the optical fiber  804  and the protective carbon sheath  814  is formed during the carbon application process. The intermediate layer  824 , which bonds the carbon layer  814  to the surface of the optical fiber  804 , has a different composition than the core of the optical fiber  804  and the carbon sheath  814 . 
       FIG. 9  is a cross-sectional view of a sample fused silica fiber  904  to which a carbon layer was applied in accordance with the present embodiment. An intermediate layer  924  between the fused quartz substrate  904  and the protective carbon layer  914  is formed during the carbon application process. The intermediate layer  924 , which bonds the carbon layer  914  to the surface of the fused silica optical fiber  904 , is silica carbide and has a different composition than the core of the fused silica optical fiber  904  and the carbon layer  914 . The image was generated by an ESEM. 
       FIG. 10  illustrates how the beam  1007  from a monochromatic coherent light source  1011  is split into 4 beams of substantially equivalent intensity and power then focused on the optical fiber  1004 . The four resulting beams strike the optical fiber  1004  at points approximately equidistant around the periphery of the optical fiber  1004 . A monochromatic coherent light source  1011  emits a beam  1007  which passes through a first 50/50 beam splitter  1025  generating a first and a second beam. The first beam passes through a second 50/50 beam splitter  1026  which splits the beam into a third and a fourth beam with intensities approximately equal to a quarter of the intensity of the original beam  1007 . The third beam passes through a first focusing lens  1040  before striking the optical fiber  1004  at an angle to the longitudinal axis of the optical fiber  1004 . The fourth beam is directed towards a first mirror  1030  which reflects the fourth beam through a second focusing lens  1043  so that it strikes the surface of the optical fiber  1004  at an angle to its longitudinal axis. The second beam is reflected off of a second mirror  1031  and passes through a third 50/50 beam splitter  1027  creating a fifth and a sixth beam. The fifth beam passes through a third focusing lens  1041  and strikes the optical fiber  1004  at an angle to the longitudinal axis of the optical fiber  1004 . The sixth beam is reflected off of a third mirror  1032 , passes through a fourth focusing lens  1042 , and hits the optical fiber  1004  at an angle to its longitudinal axis. 
     A base  1013  has central compartment  1015  and an outer compartment  1016  which house a supply of precursor gas and non-reactive gas, respectively. The optical fiber  1004  passes through the stream of non-reactive gas expelled from a second nozzle  1002  and the stream of precursor gas emitted from a first nozzle  1005 . The first nozzle  1005  and the second nozzles  1002  connect to the central compartment  1015  and to the outer compartment  1016 , respectively. After passing through the gas streams and receiving a carbon layer  1014 , the optical fiber  1004  passes through a hole in a beam dump  1009 . The beam dump  1009  is oriented such that the excess energy from the third, fourth, fifth, and sixth beams that is not absorbed by the optical fiber  1004  is directed at and absorbed by the beam dump  1009 . 
       FIG. 11  illustrates how the beam  1107  from a monochromatic coherent light source  1111  is split into 3 beams of substantially equivalent intensity and power then focused on a hollow quartz tube  1150  containing a switch  1151 . The three resulting beams strike the quartz tube  1150  at points approximately equidistant around the periphery of the quartz tube  1150 . A monochromatic coherent light source  1111  emits a beam  1107  which passes through a 33/67 beam splitter  1125  generating a first and a second beam. The first beam passes through a first focusing lens  1140  before striking the quartz tube  1150  at an angle to the longitudinal axis of the quartz tube  1150 . The second beam is reflected off of a first mirror  1131  and passes through a 50/50 beam splitter  1127  creating a third and a fourth beam. The third beam passes through a second focusing lens  1141  and strikes the quartz tube  1150  at an angle to its longitudinal axis. The fourth beam is reflected off of a second mirror  1132 , passes through a third focusing lens  1142 , and hits the quartz tube  1150  at an angle to its longitudinal axis. 
     A base  1113  has an inner compartment  1115  and an outer compartment  1116  which house a supply of precursor gas and non-reactive gas, respectively. The quartz tube  1150  is placed inside a stream of precursor gas expelled from a first conduit  1105  which is peripherally surrounded by a stream of non-reactive gas expelled from a second nozzle  1102 . The first nozzle  1105  and the second nozzles  1102  connect to the inner compartment  1115  and to the outer compartment  1016  respectively. While in the stream of precursor gas, the quartz tube  1150  receives a carbon sheath. A beam dump  1009  is oriented such that the excess energy from the second, third, and fourth sixth beams that is not absorbed by the quartz tube  1150  is directed at and absorbed by the beam dump  1009 . 
       FIG. 12  is a cross-sectional view of a sample quartz tube  1260 , encasing an electrical switch  1261 , to which a carbon sheath  1214  was applied in accordance with the present embodiment. An intermediate layer  1224  between the surface of the quartz tube  1260  and the protective carbon layer  1214  is formed during the carbon application process. The intermediate layer  1224  which bonds the carbon layer  1214  to the exterior of quartz tube  1260 , has a different composition than the quartz tube  1260  and the carbon sheath  1214 . 
       FIG. 13  is planar view of a hermetically sealed electronics microchip  1360 . An electronic microchip  1363  sandwiched between a first silicon wafer  1361  and a second silicon wafer  1362 . The microchip  1363  is placed on a surface of the first silicon wafer  1361 . The second silicon wafer  1362  is placed on top of the electronic chip  1362  and is pressed against the first silicon wafer  1361 . A protective carbon film  1314  is then applied along the seam between the first silicon wafer  1361  and the second silicon wafer  1362  in order to prevent corrosion of the electronic chip by oxygen, water, and other environmental impurities. 
       FIG. 14  shows the amount of optical fiber signal attenuation induced by the laser heating and carbon deposition process. The test results indicated at the deposition temperature range of 1450-1700 K, no signal loss is observed. The attenuation measurements are performed by an EXFO fiber testing system that consists of an IQ  2100  light source operating at 1550 nm and an IQ  2100  power meter with a resolution of 0.001 dB. 
       FIG. 15  is a cross-section view of a sample fused quartz rod [###] to which a silica carbide layer [###] was applied in accordance with the present embodiment. The image was generated by an ESEM. 
     EXAMPLES 
     Example 1 
     A bare fused silica optical fiber  104  with a diameter of 3 mm was cleansed with methanol and distilled water before the carbon coating process was started. A protective carbon coating  514  was applied to a bare silica quartz optical fiber  104  by the process as illustrated in  FIGS. 1 &amp; 5 . The applied carbon layer was polycrystalline graphite with a grain size less than or equal to 100 angstroms. Additionally, the carbon film  514  had a thickness of 250 nm and an assumed constant mass density of 2.210 g cm −3 . 
     The uncoated optical fiber  104  was secured in the v-groove clamp  550  which was mounted on a linear traverse mechanism attached to a gear rack  551  as illustrated in  FIG. 5 . The v-groove clamp  550  was driven across the linear traverse mechanism using a rack and pinion system. The rack and pinion system comprised the gear rack  551 , a machined nylon 14½ degree pressure angle spur gear  552 , and an electric motor. The spur gear  552  attached to the shaft of the electric motor  553  which rotated the spur gear  552 . The teeth of the spur gear  552  meshed with a plurality of ball bearings  554  housed in the gear rack  551 . The pitch of the gear rack  551  and of the spur gear  552  are each equal to 32. The V-groove clamp  550  moved linearly at a speed of between approximately 0.01 to 5 cm s −1 . However, for a fused silica optical fiber  104  with a diameter of 125 μm and fused quartz rod with a diameter between approximately 1 and 3 mm and a laser  111  operating at up to 25 Watts, the deposition process will work most effectively when the v-groove clamp  550  moves a linear speed substantially between 0.1 and 1 cm s −1 . 
     The top surface of the base  113 , which was manufactured from aluminum or an aluminum alloy, had a first conduit  105  and a second conduit  102  with diameters of 4.2 and 52.3 mm respectively. The first conduit  105  was formed by stainless steel tubing having an outer diameter of 6.4 mm. The inner wall of the second conduit  102  was formed by the stainless steel tubing of the first conduit  105 ; while, the outer wall of the second conduit  102  was manufactured from aluminum. A honey comb mesh material, having pentagon-shaped apertures which were 3.5 mm wide at their widest point, was inserted perpendicular to and between the stainless steel tubing of the first conduit  105  and the aluminum outer wall of the second conduit  102 . Therefore, the nitrogen gas was expelled from a surface of the base  113  through the honeycomb mesh in the second conduit  102 . The honeycomb mesh helped to prevent the nitrogen gas stream emanating from the second conduit  102  from becoming unsteady, turbulent, or oscillating, which might permit oxygen and other aerial impurities to reach the segment of the optical fiber  104  inside the hydrocarbon gas stream. 
     A first manually adjustable gas flow regulator  108  controlled the rate at which propane gas flowed from the propane supply  103  into an inner compartment  115  in the base  113 . The gas flow regulator  108  was adjusted such that the first conduit  105  expelled propane gas with 99.95% purity at a linear velocity of 17 cm s −1 . A second manually adjustable gas flow regulator  101  controlled the rate at which nitrogen gas flowed from the nitrogen gas supply  100  into an outer compartment  116  in the base  113  so that nitrogen gas with a linear velocity of 8 cm s −1  was expelled through the second conduit  102 . 
     The fused silica optical fiber  104  moved into the region defined by the jet of propane gas expelled from the first conduit  105 . The beam  107  from a 25-Watt continuous wave carbon dioxide laser (Synrad J48-2W)  111  operating at a wavelength of 10.6 μm passed through a series of three 50/50 beam splitters  1025 ,  1026 , and  1027  creating four beams. Each of the resulting four laser beams passed through a ZnSe focusing lens  1040 ,  1041 ,  1042 , and  1043  in order to produce four beams of substantially equivalent power (intensity/surface area) that were distributed substantially equidistant around the periphery of the optical fiber  104 . The diameter of the beams hitting the optical fiber  104  is approximately 1 mm. The laser beams after passing through the beam splitters and reflecting off of mirrors  1030 ,  1031 , and  1032  with a highly reflective Copper coating were focused at an angle with respect to the axis of the fused silica optical fiber  104  and on the portion of the fused silica optical fiber  104  inside the stream of propane gas. The four laser beams heated the deposition areas  721  on the optical fiber  104 . The profile of the initial laser beam  107  was Gaussian TEM 00  with a beam diameter of 1.8 mm, a divergence angle of 4 mRad, and M 2 =1.3. 
     The fused silica fiber  104  absorbed the laser energy to produce a heated deposition site  721  while propane gas pyrolyzed near the fiber&#39;s  104  surface creating a thin carbon coating  514 . Using a negative feedback loop, a two-color pyrometer (Quantum Logics QL2500-1A/S7)  106 , which operated at wavelengths of 0.90 and 1.55 μm, measured the temperature of the optical fiber  104  at a monitoring site  723 , which is approximately 2.4 mm from the deposition site  721 . The pyrometer  106  was calibrated for use within the temperature range of 1073 to 1773 K with an Optronic Laboratories&#39; quartz-halogen tungsten calibration lamp with a calibration accuracy of ±25 K. If the measured temperature was not within ±10 K of the initial preset temperature, which ranged from 1375 to 1750 K, the pyrometer  106  communicated with the computer  112  on which the LabVIEW PID Controller software was installed. When deviations greater than 5 K were measured, the computer  112  altered the laser power output in order to bring the temperature at the deposition site  721  back into the range of tolerance. 
     The beam dump  109  located behind the optical fiber  104  and opposite to the carbon dioxide laser  111  was a metal plate forged from 2024 aluminum, painted black, and measured 12.7 cm×15.24 cm×1.905 cm. The metal plate  109  had one straight internal channel 0.635 cm in diameter through which water is circulated using a water pump. The metal plate  109  was oriented with respect to the rest of the assembly so that any part of the laser beam  107  not being intercepted by the optical fiber  104  impinges on the water channel within aluminum plate  109 . 
     Fused quartz substrates were invisible to the pyrometer  106 . 
     Example 2 
     The carbon layer application in a second preferred embodiment is carried out in the same way as that in the first preferred embodiment, except in the following aspects. The beam  107  from the 25-W continuous monochromatic laser  111  is split into three beams instead of four as depicted in  FIG. 11 . The hydrocarbon gas blown onto the heated deposition site  721  is butane with the same purity as the propane used in the first preferred embodiment. The initial preset temperature at the deposition site is between 1375 and 1500 K. The inner compartment  115  of the base  113  is not centered within the base  113 . While not centered in the base  113 , the inner compartment  113  is still axially surrounded by the outer compartment  116 . 
     Example 3 
     A hermetically sealing silicon carbide layer  514  is applied to a microchip assembly  1360  comprising a superconductor microchip  1363  pressed between a first silicon wafer  1361  and a second silicon wafer  1362 , by the process as illustrated in  FIGS. 1 and 10 . The top surface of the base  113  has a central nozzle  105  and an outer nozzle  102  with diameters of 4.2 and 52.3 mm respectively. The outer nozzle  102  expels argon gas, and the central nozzle  105  expels trimethylsilane. 
     The microchip assembly  1360  is secured on the top surface of the base  1013  within the stream of trimethylsilane gas emanating from the central nozzle  1005 . The microchip assembly  1360  is oriented such that the microchip  1363  is perpendicular to the surface of the base  113  containing the central nozzle  105  and the outer nozzle  102 . A 25 Watt continuous carbon dioxide laser  111  operating at a wavelength of 10.6 μm is focused on the seam between the first silicon wafer  1361  and the second silicon wafer  1362  and heats the deposition area along the seam. The microchip assembly  1360  absorbs the energy from the argon ion  111  to produce a heated deposition site. The thermal energy of laser  111  causes the trimethylsilane gas in the vicinity of the surface of the microchip assembly  1360  to thermally decompose thus depositing a thin silicon carbide coating  514  along the seam of the microchip assembly  1360 . 
     Using a negative feedback loop, a two-color pyrometer  106  and a computer  112 , on which LabView PID Controller software is installed, maintain the temperature of the surface of the microchip assembly  1360  at the deposition site within ±10 K of the initial temperature. The pyrometer  106  is calibrated for use within the temperature range of 1073 to 1773 K with an Optronic Laboratories&#39; quartz-halogen tungsten calibration lamp with a calibration accuracy of ±25 K. When the temperature deviates more than 10 K, the pyrometer  106  communicates with the computer  112  which in turn alters the laser&#39;s  111  power output in order for the temperature to return to within the acceptable range. 
     The beam dump  109 , which is located behind and parallel to the microchip assembly  1360  and opposite the carbon dioxide laser  111 , is a solid metal slab. The metal slab  109  is oriented with respect to the rest of the assembly such that the metal slab  109  absorbs any part of the laser beam  107  not being intercepted by the microchip assembly  1360 . 
     Example 4 
     The carbon layer application in a second preferred embodiment is carried out in the same way as that in the first preferred embodiment, except in the following aspects. The base  113  has multiple inner compartments  115 . However, all of the inner compartments  115  are surrounded by the outer compartment  116 . All of the streams of hydrocarbon gas emanating from the first conduits  105  are peripherally surrounded by the stream of non-reactive gas emanating from the second conduit  102  between the surface in the base  113  in which the first conduits  105  and the second conduit  102  are located and the exhaust hood  110 . 
     Example 5 
     A hermetically sealing silicon carbide layer  514  is applied to a quartz tube  1150  encasing an electrical switch  1151  by the process as illustrated in  FIGS. 1 and 11 . The top surface of the base  113  has a central nozzle  105  and an outer nozzle  102  with diameters of 4.2 and 52.3 mm respectively. The outer nozzle  102  expels argon gas with a linear velocity of 8 cm s −1 . The central nozzle  105  expels trimethylsilane at a linear velocity of 17 cm s −1 . 
     The quartz tube  1150  is placed on the top surface of the base  1113  within the central nozzle  1105 . A 25 W continuous carbon dioxide laser  111  operating at a wavelength of 10.6 μm is focused on the portion of the surface of the quartz tube  1150  inside the stream of trimethylsilane gas and heats the deposition area on the tube  1150 . The quartz tube  1150  absorbs the energy from the laser  111  to produce a heated deposition site  721 . The laser&#39;s  111  thermal energy causes the trimethylsilane gas in the vicinity of the surface of the quartz tube  1150  to break down creating a thin silicon carbide coating  514 . 
     Using a negative feedback loop, a two-color pyrometer  106  and a computer  112 , on which LabView PID Controller software is installed, maintain the temperature of the quartz tube  1150  at the deposition site  721  within ±10 K of the initial temperature. The pyrometer  106  is calibrated for use within the temperature range of 1073 to 1773 K with an Optronic Laboratories&#39; quartz-halogen tungsten calibration lamp with a calibration accuracy of ±25 K. When the temperature deviates more than 5 K, the pyrometer  106  communicates with the computer  112  which in turn alters the laser&#39;s  111  power output in order for the temperature to return to within the acceptable range. 
     The beam dump  109 , which is located behind the quartz tube  1150  and opposite the laser  111 , is a solid metal slab. The metal slab  109  is oriented with respect to the rest of the assembly such that the metal slab  109  absorbs any part of the laser beam  107  not being intercepted by the quartz tube  1150 . 
     The preceding examples are not intended to limit the breadth of the present inventions disclosed in this application. Additional embodiments are disclosed in the following claims. Individuals skilled in the art will appreciate and recognize that a variety of alternative methods and embodiments exist given the above teachings. Therefore, the present inventions may be practiced, consistent with the scope of the claims, in manners other than those means explicitly described.