CA2274478A1

CA2274478A1 - Organometallics for lightwave optical circuit applications

Info

Publication number: CA2274478A1
Application number: CA002274478A
Authority: CA
Inventors: Heather Boek; Carlton M. Truesdale; Elizabeth A. Boylan; Michael S. Dobbins; Gary L. Lewis; Richard O. Maschmeyer; Lisa A. Tietz
Original assignee: Individual
Current assignee: Corning Inc
Priority date: 1996-12-16
Filing date: 1997-11-07
Publication date: 1998-06-25
Also published as: JP2001506221A; EP0946436A4; KR20000057597A; AU5200298A; AU717947B2; EP0946436A1; TW373086B; WO1998027018A1

Abstract

A plurality of organometallic compounds (12-18) are converted into vapors and are mixed along with combustion gases (32-38) to form a vapor stream that flows along through pipe (40). This vapor stream burns at burner (42) to form soot (50). This soot (50) deposits onto rotating substrate (60) so as to form a consolidated oxide layer.

Description

CVO ~12?01$ PCTIUS97/21W33 ORGANOMETALLICS FOR LIGHTWAVE
OPTICAL CIRCUIT APPLICATIONS
FIELD OF THE INVENTION
This invention relates generally to conversion systems such as flame hydrolysis, and to the use of organometallic sources for depositing thin uniform oxide soot or pre-sintered glass layers on planar substrates. The deposited soot is consolidated into glass 1o layers. The glass layers form the core and cladding glasses that make up the optical waveguides in integrated optical circuits.
BACKGROUND OF THE INVENTION
1s Applicants have developed flame hydrolysis systems which deposit thin oxide soot layers on planar surfaces for Lightwave Optical Circuits (LOC) applications and the making of integrated optical waveguide devices such as integrated optical circuits.
These soot layers are consolidated into glass layers which form optical waveguide cores and cladding.
2o U.S. Patent Application No. 08/581,186 filed 12729/95, Bandwidth-Adjusted Wavelength Demultiplexer, by Denis M. Trouchet, discloses such an optical circuit which functions as a wavelength demultiplexer.

WO 98n70ig PCTfUS971Z0433 Conventional methods have relied on the combustion of halide compounds which are advantageous for certain applications, but which also have serious drawbacks.
Halogens such as chlorine will strip some of the oxides from the source material which will result in nonuniformity in the glass composition resulting from the deposited soot layer. This nonuniformity translates into a degradation of the optical properties of the resulting waveguiding glass layers made by these conventional halide processes In addition to the above, the end product of the combustion reaction of the halides is chlorine, which can react with moisture in the air to form HCI, which is highly corrosive and toxic and requires equipment capable of containing it.
to It can therefore be seen that there is a need for a system for forming oxide soot layers on planar surfaces or substrates which provides for improved uniformity in the glass composition, better optical performance of waveguiding glass layers formed by the flame hydrolysis technique, and an elimination of toxic or harmful combustion by-products.
SUMMARY OF THE INVENTION
The invention is directed to the use of organometallic sources for passive planar waveguide applications and making integrated optical waveguide devices such as 2o integrated optical circuits. The advantages of using these materials is the elimination of chlorine from the system. Chlorine will strip some of the laydown oxides from these source materials via reaction and presents problems in obtaining the desired concentration of desired oxides) in the deposited layer. Another advantage of using organometallic sources is the ease of delivering materials to a conversion site, such as a burner, and the added safety that the elimination of chlorine provides.
A soot layer is deposited using improved flame hydrolysis deposition (FHD) techniques of the present invention. FHD is capable of depositing thin, uniform oxide soot or pre-sintered' glass layers on planar substrates. In one embodiment, waveguiding layers are made using planar substrates made from fused silica, 100 mm in diameter, 1 3o mm thick. Waveguiding soot glass core compositions within the Ge02-B203-P205-Si02 system are made and cladded with a glass cladding layer within the B2O3-P2O5-SiO2 WO 9B/~7818 PGT11JS97120433 ternary system. The glass compositions are chosen to yield targeted refractive indices.
(For example, increasing Ge02 increases the %n.) The FHD system of the present invention consists of a mixture of fuel gases and organometallic vapors that are blended and fed into a common stream within a flame which comprises a conversion site that is aimed directly at the fused silica planar target substrate. Within the methane/oxygen flame, the organometallic vapors (from at least two materials selected from octamethylcyclotetrasiloxane, trimethylphosphate, triethylborate, titanium isopropoxide and germanium ethoxide) are combusted to yield multicomponent oxide soot particles.
1o The velocity of the flame, the ratios of the component gases in the flame, and the rate of vapor delivery control the final soot particle size and the degree to which they are sintered. The height of the target can be changed and the target can be traversed and/or rotated to control the temperature and distribution of the deposited particles.
Once the,soot layer is deposited to the desired thickness, the sample may be given a heat treatment in order to sinter and fully densify the glass. The sintering or consolidation depends on the glass composition and thickness. The thickness of the resulting waveguiding layer is typically S-9 ,um thick. The range of consolidation temperatures is from about 1150-1340° C and the hold time in this temperature range is between about 1-7 hours.
2o To make an integrated optical waveguide device, a soot layer is deposited and sintered on a planar substrate as described above to form a core layer. A
waveguide circuit is etched into this core layer using photolithographic and reactive ion etching (RIE) techniques. A cladding layer is then deposited over the etched layer and sintered.
2s BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description of a preferred mode of practicing the invention, read in connection with the accompanying drawings, in which:
3o FIG. 1 is a schematic diagram of the flame hydrolysis system for the present invention.

FIG. 2 is an enlarged perspective view of the burner, showing the flame front and tails, and how the burner-to-sample height is measured.
FIG. 3 is an exploded perspective view of the burner assembly.
FIG. 3a is a cross-sectional view through the center of the burner shown in FIG.
3.
FIG. 4 is a side sectional view of one bubbles assembly.
FIG. 5 is a plan view of the substrate holder vacuum chuck assembly.
FIG. Sa is a bottom view of the chuck bottom.
FIG. 6 is an exploded perspective view of a second embodiment of a burner 1o assembly.
FIG. 7 illustrates a plot of consolidated glass roughness as a function of burner to sample height and the number of burner rows.
FIG. 8 illustrates a plot of change in composition as a fiinction of sample to burner height.
DETAIZ,ED DESCRIPTION OF THE INVENTION
The present invention is best illustrated by FIG. 1 which is a schematic diagram of the flame hydrolysis system 10 of the present invention which is suitable for use in 2o producing oxide soot layers on planar surfaces for use in lightwave optical circuit (LOC) applications and for making integrated optical waveguide devices such as integrated optical circuits. Selected organometallic liquids are stored in bubblers 12, 14, 16, and 18, respectively. The organometallic vapors generated by the system are carried by a nitrogen source 20 which passes N2 through heated pipes 22 into each bubbles.
The organometallic liquid is vaporized within the bubbles and carried by the nitrogen vapor through heated lines 24, 26, 28 and 30, respectively. The organometallic vapors are mixed with a preselected mixture of fuel gases which include air 32, nitrogen 34, oxygen 36 and methane 38, and delivered from pipe 39 through pipe 40 to a burner assembly 42 as a single stream. Oxide soot 50 is generated by combustion of the vapors in 3o conversion site flame 48 (see Fig. 2). The soot is deposited on a substrate 53 that is held in place by a vacuum chuck assembly 60 (Figs. 5 and Sa). Optionally, the chuck WO 98/29018 PCT/US11712A~433 can be traversed and/or rotated by a conventional transverse planetary mechanism 70 well known to the art. The exhaust from combustion, not shown, travels through a hood 62 to a scrubber (not shown). The burner assembly 42 and the vacuum chuck assembly 60 are surrounded by a filtered enclosure 52.

5 As shown in Figs. 3 and 3 a, the conversion site burner assembly 42 consists of a housing 43 with a single row of 0.30" diameter holes 44. The housing contains a glass-ceramic insert 45 which contains parallel rows of holes 41, and fine mesh stainless steel screen wrap 46 that is inserted into a cylindrical manifolding chamber 47. In a preferred embodiment, which provides for a more even distribution of the vapor mixture, insert 84 of Fig. 6 replaces screen wrap 46. The fuel gas-organometallic vapor mixture enters the burner through pipe 48 which is threaded into housing 43 and which is connected to pipe 40. The manifold chamber is sealed with threaded nut 49.
A second embodiment of a burner assembly which provides for maintaining the flame points at equal height across the entire burner face is illustrated in Fig. 6. In this embodiment, the burner assembly 70 consists of a housing 72 and a burner slot 74. The burner baffle consists of two inserts that are placed inside cylindrical manifolding chamber 76. A ceramic insert 80 has two parallel rows of hole ~ 82. A
stainless steel insert 84 is constructed in such a manner that when butted against the ceramic insert provides a path for the vapors to be distributed evenly, while maintaining the flame 2o points at equal height across the entire burner face. The vapor mixture enters the burner through pipe 86 and the chamber is sealed with threaded nut 78.
In order to ensure a layer of uniform thickness, and avoid rastering, the length "L" of the burner face or top surface which contains the burner slot or holes should be at least equal to or longer than the diameter or width of the planar substrate being coated.
The vacuum chuck assembly 60 which holds the substrate in place is shown more clearly in Figs. S and Sa. The chuck contains a vertical shaft 61, a rotation collar 62, an inner shielding ring 63 and an outer ring 67. The chuck bottom face 64 (Fig.
5a) shows the placement of the vacuum holes 65 that hold the sample 53 in place.
In operation, organometallic liquid components such as octamethylcyclotetrasiloxane, trimethylphosphate, triethylborate, and germanium ethoxide are separately placed in bubblers 12, 14, 16 and 18, respectively.
The bubblers are connected to a nitrogen carrier gas inlet valve with an aerator in its base and a vapor output valve for each bubbler. As more clearly shown in FIG. 4, which is an enlarged view of an individual bubbler as shown in FIG. 1, each bubbler chamber 12 is made of stainless steel and is roughly cylindrical with a round bottom and top. The bubbler contains ports for the inlet of nitrogen and out-flowing vapor output 13 to the burner 42. The nitrogen flows into the bubbler through input 15 at a given rate and delivered by an aerator tube that is submerged in the liquid and positioned at the bottom of the bubbler. For temperature control, the bubblers may optionally be wrapped in heat tape which are controlled by temperature controllers. The bubblers are then insulated with an 1o appropriate insulator. The outlet lines are also heated by wrapped heat-tape to temperatures in excess of the boiling point of the organometallics in order to ensure that the vapor remains gaseous. All of the outlet lines lead to a single common pipe 40 which acts to mix the vapors before reaching the burner. The temperature of the pipe must be at least as high as the highest boiling point of the components.
15 Thermocouples may be used to monitor the temperature of the organometallic liquids. Thermocouples 17 and 18 are placed inside of each bubbler so that they are submerged in the liquid. An additional thermocouple 19 is attached to the outside of each of the bubblers, along the inlet and outlet pipes.
The bubblers also have ports for filling and draining. A drain 21 is contained in 2o the bottom of each bubbler which is capped offunless the bubbler is being drained.
The delivery rates of the vapor and gases are governed by mass flow controllers (mfcs) 23 available under the trade name TYLAN and provide a volumetric flow rate.
The organometallics in vapor form are delivered by the nitrogen stream. The methane and oxygen gases are delivered separately. The system also has the capability for 25 nitrogen, air and hydrogen as part of the fuel premix. For one embodiment of the invention, the ranges of the mfcs are as follows:
CITd and 02 = 10 sLpm (standard Iiter per minute) N2 for premix = 10 sLpm OMCTS N2 = 100 sccm (standard cc per minute) 3o TMP N2 = 200 sccm TEB NZ = 50 sccm GeE = 1000 sccm W0 98127018 PCTIUS97IZ~.33 Secondary regulator (going to the mfcs):
N2 = 15 psi OZ = 17 psi Only the nitrogen line is filtered to trap moisture.
The lines from the mfcs are stainless steel, and lead either to the burner manifold directly, or to the bubblers. The lines are preheated and temperature controlled by heat-tape and commercially available temperature controllers. The temperature of each line is to equal to its own bubbler temperature.
Alternatively, the bubblers may be replaced with a vaporizer system which are known to the art, as shown in U.S. Patent No. 4,529,427 and JP 60-108338 and which are incorporated herein by reference.
In one embodiment of the present invention, a soot core and a soot clad layer are 1s formed as follows:
The core soot glass composition #5 (see Table 3 is within the GeOz-B203-P20s-Si02 system ( 15 .79, 3.86, 2.19, and 78.16% by weight) and the clad layer glass # 10 (see Table 1 ) has a composition within the B2O3-PzOs-S1O2 ternary (7.95, 3.25, and 88.8%
by weight). The compositions were analyzed by standard electron probe microanalysis 20 (EPMA) techniques.
A soot layer is deposited using standard flame hydrolysis deposition (FHD) techniques as described for Figs. 1-S. The FHD system basically consists of fuel gases and organometallic vapors that are blended and fed into a common stream within a conversion site flame that is aimed directly at a planar target substrate.
Within the 2s methane/oxygen flame, the organometallic vapors (from octamethylcyclotetrasiloxane OMCTS, trimethylphosphate TMP, triethylborate TEB, and germanium ethoxide TEOG
or GE) ire combusted and converted into multicomponent oxide soot particles.
The delivery system uses bubblers, one for each component. The bubblers are 100-400 mL
in volume and the liquid is kept at a constant level. The carrier gas is nitrogen, and the 30 lines into the bubblers are preheated to the same temperature as the bubbler in order to avoid cooling the liquid as the N2 flows. The temperatures for the bubblers were chosen to be as low as possible while still high enough to produce adequate vapor for a given N2 flow. The outlet lines need to exceed the boiling point in order to keep the vapors of wo ~s~z~ois rc°r~s9~rio~3 s the liquids from condensing. The temperature controllers for the carrier gas inlet lines, bubblers, and outlet lines are preheated to the following temperatures:
Temperature (° C) 81 Inlet to the OMCTS bubbler and the bubbler itself (22 + 18) 70 Inlet to TMP and TMP bubbler (22 + 16) 60 Inlet to TEB and TEB bubbler (22 + 14) 51 Inlet to GE and GE bubbler (22 + 12) >176 Outlet line from OMCTS bubbler (30) > 197 Outlet tine from TMP bubbIer (28) > 117 Outlet line from TEB bubbler (26) >185 Outlet line from GE bubbler (24) r 197 Common port below the burner A fused silica substrate (100 mm diameter, 1 mm thick) is cleaned and weighed before placing on the chuck 60 which holds the sample above the flame by vacuum. The mass flow controllers are turned on to flow the carrier gas into the bubblers to deliver a given volume flow rate of vapor (sccm), as well as to control the flow rate of the 2o methane and oxygen (sLpm). The delivery rates for the materials for the core and clad glass are as follows:
OMCTS TMP TEB GE CH., Oz core #5 0.023 0.0002 0.009 0.006 5.85 5.6 clad #10 0.025 0.0040 0.007 0 5.85 5.6 The magnehelic below the burner monitors the backpressure, usually at 1.0 in.
H20. The height of the substrate above the flame is set accordingly to a predetermined distance and the substrate is traversed at a constant speed and simultaneously rotated by mechanism 70 to control the temperature and distribution of the deposited particles.
The thickness of the glass soot is controlled by how many times the substrate traverses above the flame. Typically, the thickness of the core layer is from about 5 to 7 microns and the thickness of the clad layer is from about 4 to 20 microns.
3o Once the soot layer is deposited to the desired thickness, the sample is given a heat treatment in order to sinter and fully densify the glass. The consolidation schedule depends on the glass composition and thickness. The thickness of the core layer #S is 5 ,um thick; the clad layer # 10 is about 4 ,cun thick. The top consolidation temperature for wo ~snao~s rcrrt~ssr~ruw~3 the core was 1290° C, and for the clad was 1200° C. The hold times at those temperatures were 2 and I hours, respectively.
The step of forming an integrated optical waveguide circuit device includes:
1. A device circuitry is etched into the core layer using photolithographic and reactive ion etching (ItIE) techniques.
2. A cladding layer is deposited and sintered, blanketing this device circuitry.
3. The device is pigtailed, packaged, and connectorized.
Tables 1 and 2 show a comparison of standard deviations of oxide weight 1o percentages from cross-section EPMA data for organometallic-generated glasses of this invention and for traditionally deposited halide-generated cladding glasses.
(The lowest values for the halide-generated glasses (0.47 for SiOz, 0.39 for B203, and 0.
I3 P205) were used as upper values for the degree of compositional contaol needed for the organometallic-generated glasses of this invention.) The glasses of this invention show is significantly less variation for each oxide throughout the deposited glass layer.

WO 981270!8 PCT/US97l2A433 Table 1 - Organometallic Clad Example P205 stdev B203 stdev Si02 stdev #

1 .09 0.23 0.21 2 0.10 0.19 0.23 3 0.13 0.19 0.28 4 0.11 O.I3 0.16 5 0.03 0.28 0.21 6 0.04 0.22 0.16 7 0.04 0.18 0.12 8 0.03 0.23 0.05 9 0.05 0.15 0.37 10 0.06 0.13 0.02 11 0.06 0.13 0.09 ~2 0.06 0.21 0.41 13 0.09 0.13 0.10 14 0.08 0.26 0.10 0. i 1 0.31 0.02 stdev max 0.13 0.31 0.41 stdev min 0.03 0.13 0.02 Table 2 - Halide Clad ' I
Example P205 stdev B203 stdev SiOz stdev I
#

1 0.16 1.50 1.44 2 0.13 0.56 0.51 3 0.41 0.96 0.77 4 0.67 1.38 1.11 5 0.22 0.6I 0.47 6 0.13 0.64 0.83 7 0.15 0.55 0.51 8 0.21 0.72 0.74 stdev max 0.67 1.50 1.44 stdev min 0.13 0.5 5 0.47 wo 9snms rcrmss~ruw33 The following Tables 3 and 4 show comparisons of standard deviations of oxide weight percentages for cross-section EPMA data for halide-generated core-type glasses and for organometallio-generated glasses of this invention. The glasses of this invention show significantly less variation for Ge02 and Si02 throughout the deposited core glass layer.
Table 3 - Organometallic Core Example P20s stdevB2O3 stdev Si02 stdev Ge02 stdev #

1 0.22 0.19 0.66 0.30 2 0.02 0.16 0.59 0.45 3 0.28 0.13 0.42 0.65 4 0.21 0.24 0.17 0.26 0.21 0.13 0.21 0.16 6 0.19 0.13 0.20 0.28 7 0.15 0.23 0.55 0.56 8 0.13 0.20 0.05 0.08 9 0.36 0.20 0.31 0.30 0.14 0.12 0.01 0.21 11 0.15 0.10 0.24 0.40 stdev max 0.36 0.24 0.66 0.65 stdev min 0.02 0.01 0.01 0.08 WO ~2?plg PCT/US97/Z0433 Table 4 - Halide Core Example P20s stdevBz03 stdev Si02 stdevGe02 stdev #

1 0.21 0.70 0.98 0.79 2 0.17 0.49 1.17 1.12 3 0.41 0.73 2.3 9 2.25 4 0.15 0.27 1.78 1.46 0.26 0.29 1.09 1.13 6 0.29 0.34 1.05 0.72 7 0.10 0.26 0.96 0.66 8 0.16 0.44 2.13 1.55 9_ 0.12 0.18 _ 1.74 1.45 stdev max 0.41 0.73 2.39 2.25 stdev min 0.10 0.18 0.96 0.66 The following formulas illustrate the combustion products of typical organometallics which may be used in the present invention.
s Table 5 Combustion Products of Organometallics OMCTS : Octamethylcylcotetrasiloxane CgH2aOaSi4 + 16 02 = 4 Si02 + 8 COZ + 12 H20 to TMP: Trimethylphosphate 2(CH30)3P0 + 9 02 = P20s + 6 C02 + 9 H20 TEB: Triethylborate 2B(OCZHs)3 + 18 02 = B203 + 12 C02 + 15 H20 GeE: Germanium ethoxide CaHzoOaGe + 12 O2 = GeO2 + 8 COi + 10 H20 WO 98l270I8 PCTJUS97IZA~33 Titanium isopropoxide Ti(OC3H~)4 + 18 Oa = TiOa + 12 COa + 14 Ha0 In a further embodiment of the present invention, the oxide soot particles can be concurrently deposited and sintered into a uniform glass layer on the planar substrate without melting or softening the substrate. This embodiment provides the advantage of eliminating a separate consolidation step, avoids wafer warpage, and provides a glass surface which is smooth with few or no defects.
The methods by which this sintering in situ can be accomplished is by raising the 1o substrate temperature as follows:
1. increase the methane concentration (hotter flame) 2. insulate or heat the sample holder 3. lower sample height (as close as possible to burner to obtain hotter and smaller soot particles) i5 4. alter the composition to a lower sintering temperature (e.g., increase B2O3/P205) 5. use a high velocity burner (single row vs. triple row).
The first method consists of increasing the methane to oxygen ratio, while holding all other conditions constant. The level of the oxygen is high enough to result in 2o stoichiometric reactions while the higher methane produces a hotter flame.
Samples 10 cm in diameter are used, and the pre-sintered area is circular and clear glass. The boundaries of this region are measured in terms of outer diameter (cm) (see Table 6).
When the CHI /OZ ratio increases, the diameter increases from 4.8 to 6.0 cm.
When the ratio is about the same but the CHa is increased, the diameter increases from 6.0 to 8.8 25 cm.
Table 6 Sample # 02 (sLpm)CH4 (sLpm) CH4 /Oa Pre-sintered diameter 95-276 5.06 5.20 1.03 6.0 cm 95-278 6.00 5.20 0.87 4.8 cm 95-279 5.60 5.90 1.05 8.8 cm WO 98n'r018 PCT/US97120433 Another method is to insulate the sample holder. This is accomplished by covering the vacuum chuck with a thick layer of form-fitting fiberfrax. The pre-sintered area increased from 6.0 to 6.5 when the chuck was kept hotter through the run (see Table 7).
Table 7 Sample 02 (sLpm)CH4 (sLpm) CH4 /02 Pre-sintered diameter #

95-276 5.06 5.20 1.03 6.0 cm : No insulation 95-277 5.06 5.20 1.03 6.5 cm : With insulation A third method consists of bringing the substrate holder close to the flame front.
The optimum burner-to-sample height is directly above the points of the flame.
A fourth method consists of modifying the composition of the glass. Fig. 8 to shows a change in composition in the consolidated glass with a ratio of B203lPZOs decreasing as a function of sample-to-burner height. For higher B203/P205 ratios, the snots are more easily sintered.
A fifth method consists of increasing the velocity of the flame, such as by using a single row of burner holes rather than three rows of holes. The roughness of the soot as 15 a function of coarseness of the soot can be correlated with the number of rows of burner holes.
Consolidated samples were measured for roughness using a profilometer, averaging 3 traces at 3 different sites over a distance of 4 mm. The roughness average as a function of sample-to-burner height is shown in Fig. 7 for samples generated using a 2o single row burner and a triple row burner. The glass surface is smoother for the single row burner and roughens for both cases with increasing height above the burner.
While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without 25 departing from the spirit and scope of the invention as defined by the claims.

Claims

WE CLAIM:

1. A method for forming an oxide soot layer on a planar substrate which comprises the steps:
(a) producing a halide free gas stream containing a plurality of organometallic compounds in vapor;
(b) passing said stream into a conversion site to form a mixture of oxide soot particles; and (c) positioning a planar support proximate said conversion site and depositing said mixture of oxide soot particles onto said support to form a coherent oxide soot layer.

2. The method of claim 1 in which the step of producing a halide free gas stream containing a plurality of organometallic compounds in vapor form further includes mixing a gaseous fuel with said stream.

3. The method of claim 1 in which the step of positioning a planar support proximate said conversion site further includes positioning said planar support horizontally above said conversion site.

4. The method of claim 1 in which the organometallic compounds comprise at least two materials selected from the group consisting of octamethylcyclotetrasiloxane, trimethylphosphate, triethylborate, titanium isopropoxide and germanium ethoxide.

5. The method of claim 1 in which the vapors of organometallic compounds are contained in an inert gas.

6. The method of claim 5 in which the inert gas comprises nitrogen.

7. The method of claim 2 in which the gaseous fuel comprises methane and oxygen.

8. A method of making an optical waveguide device which comprises the steps:
(a) producing a halide free gas stream containing a plurality of organometallic compounds in vapor form;
(b) mixing said gas stream with a gaseous fuel mixture to form a common vapor stream;
(c) passing said vapor stream into a flame of a burner to form a plurality of oxide soot particles;
(d) depositing said oxide soot particles onto a support to form a coherent oxide soot layer;
(e) consolidating said oxide soot layer into a glass layer; and (f) forming an optical waveguide device with said glass layer.

9. A method of making an integrated optical waveguide upon a supporting planar substrate which comprises the steps:
(a) producing a halide free gas stream containing a plurality of organometallic compounds in vapor;
(b) mixing said gas stream with a gaseous fuel mixture to form a common vapor stream;
(c) passing said vapor stream into a flame of a burner to form a plurality of oxide soot particles;
(d) depositing said oxide soot particles onto a support which is heated to an elevated temperature sufficient to sinter said oxide particles in situ to form a glassy layer; and (e) forming an integrated optical waveguide device with said glassy layer.

10. A method of making an optical circuit which comprises the steps:

(a) producing a halide free gas stream containing a plurality of organometallic compounds in vapor form;
(b) mixing said gas stream with a gaseous fuel to form a common vapor stream;
(c) passing said vapor stream into a flame of a burner to form a plurality of oxide soot particles;
(d) depositing said oxide soot particles onto a planar support which is suspended above the burner to form a coherent oxide soot layer; and (e) forming an optical circuit from said oxide soot layer.

11. The method of claim 10 in which the planar support is traversed over the burner flame during the deposition process.

12. The method of claim 11 in which the support is also rotated during the deposition process.

13. The method of claim 10 in which the support is moved over the burner flame in a planetary motion during the deposition process.

14. Apparatus for forming an oxide soot layer on a planar substrate which comprises:
(a) a vapor mixing piping network, said vapor mixing piping network comprised of a common mixing pipe, a plurality of vapor compound supply lines connected to said common mixing pipe, said vapor compound supply lines for supplying a plurality of vapor compounds to said common mixing pipe, a fuel gas pipe connected to said common mixing pipe, said fuel gas pipe for supplying a fuel gas to said common mixing pipe, a herein said plurality of vapor compounds and said fuel gas mix together within said common mixing pipe to form a common mixed vapor stream contained within said common mixing pipe, said vapor mixing piping network further comprised of a burner input pipe end, said burner input pipe end connected to said common mixing pipe, said burner input pipe end for inputting said common mixed vapor stream contained within said common mixing pipe into a burner;
(b) a burner which has an outer housing which includes a top upper face which contain a burner port which is connected to said burner input pipe end through a common internal burner manifold chamber, said manifold chamber within said burner; and (c) a support for a planar substrate disposed above said burner, said support having means for providing horizontal movement across the face of said burner.

15. The apparatus of claim 14 in which said support also provides for means to rotate a substrate above said burner.

16. The apparatus of claim 14 in which the burner port comprises an elongated slot.

17. The apparatus of claim 14 in which the burner port comprises a plurality of holes.

18. The apparatus of claim 17 in which the holes are contained in a single row of equally spaced holes.

19. The apparatus of claim 14 in which the burner contains at least one internal burner baffle member contained within said manifold chamber which provides for uniform flow across the length of the burner face.

20. The apparatus of claim 19 in which the at least one internal burner baffle member consists of two inserts which are abutted against each other to provide a path for the common vapor steam to be evenly distributed to the burner port.

21. The apparatus of claim 14 in which the length of the burner is equal to or longer than the diameter or width of the planar substrate.

22. A method for forming an oxide soot layer on a substrate which comprises the steps:
(a) producing a halide free gas stream containing a plurality of organometallic compounds in vapor form;
(b) passing said stream into a conversion site to form a mixture of oxide soot particles; and (c) positioning a support proximate said conversion site and depositing said mixture of oxide soot particles onto said support to form an oxide soot layer.

23. The method of claim 22 in which the conversion site comprises a flame.

24. The method of claim 23 in which the halide free gas stream containing a plurality of organometallic compounds in vapor form is produced distal from said flame.