Abstract:
A method for producing an optical waveguide component includes providing a glass producing soot, providing a soot delivery device adapted to provide an electrostatic charge to the soot, and providing a substrate material adapted to receive the glass producing soot thereon. The method also includes delivering the soot to the delivery device, and accelerating the soot as it passes through the delivery device. The method further includes charging the soot as the soot is passed through the delivery device with a sufficient charge to attract the soot to the substrate material, and depositing the soot on the substrate material by spraying the soot onto the substrate material via the delivery device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation-in-part of U.S. patent application Ser. No. 09/718,060, filed Nov. 20, 2000, entitled METHOD AND APPARATUS TO COLLECT SOOT FOR MELTS, which is hereby incorporated by reference, and which claims priority to U.S. Provisional Patent Application Ser. No. 60/187,755, filed Mar. 8, 2000, entitled METHOD AND APPARATUS TO COLLECT SOOT FOR MELTS, which is hereby incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention is generally related to manufacturing optical waveguides, components and products, and more particularly to an apparatus and method for applying a glass producing soot to a substrate.  
           [0004]    2. Technical Background  
           [0005]    One of the difficulties involved in most optical component manufacturing methods and processes is that of limiting attenuation losses in the resultant optical components. Attenuation loss is due, at least in part, to the difficulty and expense associated with obtaining soot materials of sufficient purity through heretofore utilized batch production methods. A need currently exists to produce and collect glass producing soot materials of sufficient purity via a waveguide burner.  
           [0006]    Another problem associated with most optical component manufacturing processes is the inability to obtain glass producing soots that contain dopants beyond certain weight percents. One of the reasons for this limitation is that the temperatures associated with most soot producing waveguide burners is great enough to “bake-out” dopants within the resultant soot above a certain weight percent. Therefore, a need exists that allows for the production of glass producing soot that allows greater amounts of a particular dopant to remain in the soot as a weight percent during production of the soot. This process should utilize waveguide burners currently available to enable the use of a wide variety of soot compositions and dopants, a wide variety of soot particle sizes, and numerous soot collection devices.  
           [0007]    Finally, typical soot producing systems utilize a single burner to produce soot that is deposited on a single substrate at a time. Methods that utilize conventional vapor delivery to the associated burner enable only a relatively narrow range of materials as dopants to be used. Further, scaling up of these systems would require the addition of entire wafer producing machines, and/or the addition of burners to each machine resulting in only a marginal increase in production rate. As a result of these limitations, a need exists for a method and apparatus for producing optical waveguide components more quickly and efficiently.  
         SUMMARY OF THE INVENTION  
         [0008]    This invention meets the need for a method and apparatus for producing optical waveguide devices in a low cost, high volume, high uniformity manufacturing process. Specifically, this invention utilizes electrostatic attraction forces to more quickly and effectively coat substrate materials with a glass producing soot.  
           [0009]    One aspect of the present invention is to provide a method for producing an optical waveguide component, including providing a glass producing soot, providing a soot delivery device adapted to provide a charge to the soot, and providing a substrate material adapted to receive the glass producing soot thereon. The method further includes adapted to receive the glass producing soot thereon. The method further includes delivering the soot to the delivery device, and accelerating the soot as it passes through the device. The method further includes charging the soot as the soot passes through the delivery device with a sufficient electrostatic charge to attract the soot to the substrate material, and depositing the soot on the substrate material by spraying the soot onto the substrate material via the delivery device.  
           [0010]    Another aspect of the present invention is to provide a method for producing an optical waveguide component that includes generating a glass-producing soot via a burner providing the generated soot to a surface area collector, and collecting the soot within the surface area collector, wherein the burner is disposed such that the soot collected in the surface area collector is substantially unaffected by the heat from the burner. The method also includes providing a soot delivery device adapted to provide a charge to the soot, and providing a substrate material adapted to receive the glass producing soot thereon. The method further includes delivering the soot from the surface area collector to the delivery device, accelerating the soot as it passes through the delivery device, electrically charging the soot as the soot passes through the delivery device with a sufficient electrostatic charge such that the soot is attracted to the substrate material, conveying a plurality of the substrates to a location proximate the delivery device, and depositing the soot on the plurality of substrates by spraying the soot onto the plurality of substrates via the delivery device. The method still further includes conveying the plurality of substrates from proximate the delivery device to a sintering oven, and sintering the plurality of substrates that have collected the soot, thereby allowing the resultant optical components to be made in a continuous-type process.  
           [0011]    Yet another aspect of the present invention is to provide an apparatus for producing an optical waveguide component that includes an enclosure for housing a glass producing soot therein, and a soot delivery device in communication with the enclosure for receiving the delivery device in communication with the enclosure for receiving the glass producing soot therefrom. The soot delivery device is adapted to provide an electrical charge to the glass producing soot and accelerate the glass producing soot towards a substrate as the glass producing soot is passed through the soot delivery device, thereby causing an electrostatic attraction force between the glass producing soot and the substrate and depositing the glass producing soot onto the substrate.  
           [0012]    Additional features and advantages of the invention will be set forth in the detailed description that follows and will be apparent to those skilled in the art from the description or recognized by practicing the invention as described in the description which follows, together with the claims and appended drawings.  
           [0013]    It is to be understood that both the forgoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of the specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a side elevational view of a soot delivery system of the present invention, cut-away to show a quantity of soot within a first housing and with a second housing shown in phantom about a soot delivery device;  
         [0015]    [0015]FIG. 2 is a side elevational view of an electrostatic gun of the soot delivery device;  
         [0016]    [0016]FIG. 3 is a partially schematic side elevational view of the soot delivery system in conjunction with a soot producing system;  
         [0017]    [0017]FIG. 4 is a cross-sectional side view of a burner for use within the soot producing system;  
         [0018]    [0018]FIG. 5 is a top view of a substrate with conductive materials; and  
         [0019]    [0019]FIG. 6 is a partially schematic side elevational view of an optical component production line incorporating the soot producing system and soot delivery system of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Reference will now be made in detail to the present preferred embodiments of the invention, examples for which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts.  
         [0021]    For purposes of the description herein, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting unless the claims expressly state otherwise.  
         [0022]    Referring initially to FIG. 1, there is shown a soot delivery system  10  for constructing an optical waveguide component embodying the present invention and used in its method. Delivery system  10  includes an enclosure or housing  12  that houses a glass producing soot  14  therein. Delivery system  10  includes a soot delivery device  15  that includes an electrostatic gun  16  which is in communication with housing  12  via a soot supply line  18 . In operation, soot  14  flows to electrostatic gun  16  via supply line  18  where electrostatic gun  16  electrically charges the individual particles of soot  14  as soot  14  flows through electrostatic gun  16 . Electrostatic gun  16  accelerates the soot towards a substrate  20 , where soot  26  is deposited onto substrate  20  via the electrostatic attraction force between substrate  20  and the charged particles of soot. The soot  26  as deposited onto substrate  20  can be deposited across the entire substrate  20  and in patterns thereon as discussed below.  
         [0023]    As illustrated, soot delivery device  15  includes electrostatic gun  16 , however, it should be noted that any device adapted to provide soot  14  with an electric charge and accelerate soot  14  towards a receiving substrate may be utilized. Electrostatic gun  16  is preferably provided in the form of a commercially available gun, such as the Model 8830 Arc Spray System, available from TAFA Incorporated of Concord, N.H. However, other electrostatic spray guns may be utilized. Electrostatic gun  16  (FIG. 2) includes a body section  22 , a directional nozzle  24  for concentrating the direction of sprayed soot  26  (FIG. 1) in a unified direction, and an electrical supply line  28  in communication with an electrical source  30 . Electrostatic gun  16  is adapted to receive soot  14  from housing  12 , provide an electrostatic charge to soot  14  as it passes through electrostatic gun  16 , resulting in a pattern of accelerated soot  26  directed towards substrate  20 .  
         [0024]    In the preferred embodiment, electrostatic forces guide soot particles  26  onto substrate  20  so that uniform layers  17  of soot particles  14  deposit upon substrate  20 . This is due to the electrostatic charge provided to soot  14  via the electrostatic gun  16 , and an electrostatic charge on the substrate  20 . In the illustrated example, substrate  20  is grounded to an outside ground, although it should be noted the substrate  20  may also be coupled to a positive or negative voltage source as described below.  
         [0025]    It should be noted that although the illustrated substrate  20  has a planar geometrical shape as illustrated, numerous other geometrical shapes and orientations useful in manufacturing optical waveguide devices and components may be utilized. These other shapes and orientations include, but are not limited to, those associated with optical waveguide fibers, lightwave optical circuits, narrow band wavelength demultiplexers, dynamic gain flattening filters, MEMS optical switches, liquid crystal cross-connects, phasers and electro-optic devices.  
         [0026]    The reference numeral  10   a  (FIG. 3) generally designates another embodiment of the soot delivery system as it is utilized in cooperation with a soot producing system  32 . Since soot delivery system  10   a  is similar to the previously described soot delivery system  10 , similar parts appearing in FIG. 1 and FIG. 3, respectively, are represented by the same, corresponding reference numeral, except for the suffix “a” in the numerals of the latter. Soot producing system  32  is adapted to produce and collect soot  14   a  for glass melting manufacturing those optical components and devices as noted above. In general, surface area collector  36  captures soot for such uses as (but not limited to) glass melting. Surface area collector  36  is designed to fit into existing soot deposition equipment.  
         [0027]    In the illustrated example, soot producing system  32  includes a waveguide burner  34  and a surface area collector  36 . Waveguide burner  34  preferably uses a precursor/liquid delivery system  38  in order to produce soot  14   a.  It should be noted that while a liquid delivery system is used in the illustrated example, liquid delivery or conventional vapor delivery burners are able to be used with the surface area collector  36 . Organometallic liquid precursors are pumped to waveguide burner  34  with an atomizing gas compound of a mixture of CF 4  and nitrogen, CF 4  and oxygen, or other like gases, such as perfluoro compounds, nitrogen/oxygen mixtures or argon, which are reacted within burner  34 . An exemplary organometallic liquid for the present invention includes octamethylcyclotetrasiloxane (OMCTS) Si 4 O 4 C 8 H 24 . The CF 4 —N 2  mixture atomizes the organometallic liquid precursor and provides a source of fluorine in the soot. Although a particular method for producing soot  14   a  is disclosed herein, any method known for producing a glass producing soot may be utilized.  
         [0028]    While a fluorine doped precursor is used as an example herein, any other desired elements may be doped into the soot by choosing an appropriate precursor dopant, as will be appreciated by a person of skill in the art. The precursor dopant includes the element desired to be doped into the soot. Elements that may be doped into the soot include, for example, fluorine, germanium, titanium, aluminum, phosphorus, rare earth elements, sulfur, zirconium, antimony and combinations thereof. The precursor may also include metal, metal oxides, non-metal oxides, and combinations thereof.  
         [0029]    Waveguide burner  34  of the present invention burns liquids directly and does not require materials to be vaporized before being burned in a waveguide burner as is done in prior art approaches. Using the fluorine dopant noted above as an example, prior art approaches achieve around 3 weight percent fluorine within the resultant soot, whereas the present invention achieves around 15 weight percent fluorine within the resultant soot. Moreover, the present invention is not limited to only using a fluorine doped precursor, but also is applicable to using any precursor substance, especially those substances that are impractical to place in a vapor phase, such as those having relatively low vapor pressure. As a non-limiting example, the present invention also generates and deposits soot containing relatively high concentrations of GeO 2  dopant. Moreover, the present invention includes not only the use of a single burner, but using multiple burners (not shown) with a collector sufficiently large enough to process the substrates from the multiple burners.  
         [0030]    The technique of the present invention produces soot  14   a  which is intrinsically of a higher purity than batch melts. Multi-component soots are produced in waveguide burner  34  are more intimately mixed, and of a smaller particle size than most batch materials purchased for melting processes. The resulting waveguide soots melt at lower temperatures, and produce more homogeneous cord-free glasses. This is especially advantageous for viscous, high melting glasses, such as the alkali-antimony-alumino-silicates used as optical amplifier materials. Again, as a non-limiting example, waveguide burner  34  is provided with alkoxide solutions as precursors in order to produce the alkali-antimony-alumino-silicates.  
         [0031]    [0031]FIG. 4 depicts a cross-sectional view of burner  34 . Burner  34  incorporates within its structure an atomizer  64 , which injects very finely atomized liquid reactant particles into flame  66 . Soot is produced by combustion of the liquid reactant and is collected by the surface area collector  36  (FIG. 3). As shown by FIG. 4, burner  34  includes a series of concentric channels surrounding atomizer  64 . Oxygen is delivered to flame  66  through channels  68  and  70 . A premix of oxygen and a fuel such as methane is conducted to the flame through outermost channel  72 .  
         [0032]    As a non-limiting example, channel  65  contains a mixture of CF 4  and N 2 . The CF 4 —N 2  mixture atomizes the organometallic liquid precursor into particles which is burned in the flame of the burner. The CF 4 —N 2  atomizing mixture provides the source of fluorine in the soot. Mixtures other than CF 4  may be used, such as SF 6 . The atomizing mixture is varied in order to vary the amount of fluorine or other dopant in the soot depending upon the specific application.  
         [0033]    Soot  14   a  is preferably directed into an interior chamber  46  of surface area collector  36  through an opening or aperture  40 . It should be noted that in the present example, collector  46  is utilized in a similar manner as housing  12  described above, in that collector  46  is used to house soot  14   a  for delivery to an associated delivery device  15   a.  Soot  14  is directed through aperture  40  and rotates and swirls within chamber  46  of surface area collector  36  and collects upon walls  42  and/or floor  44  of collector  36 . The top of collector  36  includes a fume exhaust  50  which allows gases from within chamber  46  to adjust to the soot capture rate.  
         [0034]    Soot  14  is extracted after a period of time when the interior chamber  46  of collector  36  has sufficiently cooled. A flange  53  depicts where an upper portion  55  of surface area collector  36  detaches from a lower portion  57  of collector  36  in order to extract soot  14  if so desired. To aid in soot removal and reduce the possibility contamination, the inside of chamber  46  in one embodiment contains a heat resistant coating  52  that is compatible with the materials being collected. Coating  52  includes, but is in no way limited to, being made of silica so that metallic contamination from the collector is eliminated. However, it is to be understood that the present invention includes using other chemically inert and heat resistant materials, such as, but not limited to, quartz.  
         [0035]    Surface area collector  36  in this embodiment as well as with other embodiments includes a water cooled shell/jacket (not shown) that encircles the outside diameter of chamber  46 . The water cooled shell enhances the thermophoresis and capture efficiency of the surface area collector  36 . Due at least to the enhanced thermophoresis, i.e., the process by which particles move in a temperature gradient from hot regions to cooler regions, surface area collector  36  collects soot  14  in a substantially uniform manner on its walls  42  and floor  44 .  
         [0036]    The operating temperature of the surface area collector  36  is typically around 300° C. and thus does not bake out the fluorine from soot  14   a  as do the prior art approaches since the prior art approaches operate at a much higher temperature. Thus, the approach of collecting the deposit in a 300° C. environment that is removed from where burner  34  is located has decided advantages since soot  14   a  is not substantially reheated by subsequently deposited soot. Preferably, the collector environment is about two feet removed from the burner location. However, the distance of two feet is only an exemplary distance as other distances will achieve the effect of the present invention as it is dependent upon the application at hand. Such exemplary non-limiting distances include six, twelve, eighteen inches and greater between the flame of burner  34  and where soot  14   a  is deposited within chamber  46  of surface area collector  36 . This environment has substantial advantages versus a 2000° C. environment since it helps in part to improve the amount of fluorine, or other dopant, retained in the deposited material. It should be understood that the present invention is not limited to operating around a 300° C. temperature, but includes collecting soot from a burner at a distance that allows the soot not to be reheated.  
         [0037]    In a preferred embodiment, soot  14   a  is then supplied from chamber  46  of collector  36  to electrostatic gun  16  of soot delivery device  15   a  via soot supply line  18   a.  In this manner, an optical waveguide component production line is created, wherein soot producing system  32  produces a highly pure soot  14   a  that is in turn utilized to produce optical waveguide components via delivery system  10   a  that efficiently and accurately supplies soot  14   a  to substrate  20   a.  The soot  14   a  is attracted to the associated substrate  20   a  via the electrostatic attraction forces therebetween. As described above, soot  14   a  receives an electrostatic charge from electrostatic gun  16   a . Substrate  20   a  may be grounded to an outside source  21  as noted above. Alternatively, a source  100  for generating a charge near substrate  20   a  that cooperated with the electrostatic charge of soot  14   a  may be utilized to enhance the attraction of soot  14   a  to substrate  20   a.  In the illustrated example, an electromagnet  102  having a ferrous core wrapped with a wire that carries a D.C. current is placed near substrate  20   a  as soot  14   a  is sprayed from electrostatic gun  16   a  towards substrate  20   a.  The electromagnet  102  creates an electromagnetic field near substrate  20   a  that cooperates with the electrostatic charge of soot  14   a , thereby attracting soot  14   a  to substrate  20   a.  Although an electrostatic force is used as an example, other methods and devices capable of generating a charge that cooperates with the electrostatic charge of soot  14   a  may be utilized. As illustrated, a current source  104  provides an electrical current to electromagnet  102 .  
         [0038]    In an alternative embodiment, a housing  59  (FIGS. 1 and 3) is located about soot delivery devices  15  and  15   a,  thereby containing any over-spray soot supplied by soot delivery devices  15  and  15   a  but not captured on substrates  20  and  20   a.    
         [0039]    [0039]FIG. 5 depicts an embodiment of substrate  20  wherein a lightwave optical component circuit is created on substrate  20 . First, conductive materials  60  are deposited in the pattern  62  of a desired lightwave optical component circuit. Substrate  20  with circuit pattern  62  is then charged. The charged circuit pattern  62  being of a different material with different conductive properties than substrate  20  attracts soot  14  such that soot  14  is deposited at least substantially on charged circuit pattern  62 . This approach produces an optical pathway without requiring masking and etching processes to create the pathway.  
         [0040]    [0040]FIG. 6 depicts an optical component production line  79  for efficiently processing multiple substrates (e.g., planar substrates) according to the teachings of the present invention and which utilized the concepts of the soot delivery system  10  and conveying system  80  that conveys substrates  20  in proximity to electrostatic gun  16  and a sintering oven  82 . Specifically, substrates  20  are loaded at the upstream end  84  of conveying system  80  so that substrates  20  can pass in close proximity to the electrostatic gun  16  and receive soot  14  thereon. Soot  14  is supplied from collector  36  to electrostatic gun  16  via soot delivery line  18 . Soot  14  is then sprayed onto substrates  20 , thereby creating a layer of deposited soot  17  on each substrate  20 .  
         [0041]    Substrates  20  remain in proximity to gun  16  for an amount of time that allows a sufficient amount of soot  14  to be deposited upon substrates  20 . After a sufficient deposition has occurred, conveyor system  80  conveys substrates  20  to sintering oven  82  so that the soot deposition on substrates  20  can be sintered. After sintering of the deposition has occurred, conveyor system  80  conveys substrates  20  from sintering oven  82  to the downstream end  92  where the finished parts are removed.  
         [0042]    It will become apparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.