CA2084461A1 - Method for fabricating an optical waveguide - Google Patents
Method for fabricating an optical waveguideInfo
- Publication number
- CA2084461A1 CA2084461A1 CA002084461A CA2084461A CA2084461A1 CA 2084461 A1 CA2084461 A1 CA 2084461A1 CA 002084461 A CA002084461 A CA 002084461A CA 2084461 A CA2084461 A CA 2084461A CA 2084461 A1 CA2084461 A1 CA 2084461A1
- Authority
- CA
- Canada
- Prior art keywords
- layer
- soot
- bulk density
- deposited
- forming
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
- C03B19/1453—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
- C03C17/02—Surface treatment of glass, not in the form of fibres or filaments, by coating with glass
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12035—Materials
- G02B2006/12038—Glass (SiO2 based materials)
Abstract
ABSTRACT OF THE DISCLOSURE
In the first step, a fuel and raw material gasses are fed to a burner while flames from the burner scan a Si substrate. Synthesized glass fine particles are deposited on the substrate to form a first porous vitreous layer to be a under cladding layer. In the second step, the first porous vitreous layer is heated by the flames. A bulk density of an upper part of the first porous vitreous layer is raised to 0.3 g/cm3. This upper part with a raised bulk density functions as a shield layer against GeO2. In the third step, a second porous vitreous layer to be a core layer is deposited uniformly on the first porous vitreous layer. In the fourth step, the first and the second porous vitreous layers are sintered. In this case, the shield layer with a higher bulk density hinders the GeO2 component which has evaporated from the second porous vitreous layer from diffusing into the first porous vitreous layer.
In the first step, a fuel and raw material gasses are fed to a burner while flames from the burner scan a Si substrate. Synthesized glass fine particles are deposited on the substrate to form a first porous vitreous layer to be a under cladding layer. In the second step, the first porous vitreous layer is heated by the flames. A bulk density of an upper part of the first porous vitreous layer is raised to 0.3 g/cm3. This upper part with a raised bulk density functions as a shield layer against GeO2. In the third step, a second porous vitreous layer to be a core layer is deposited uniformly on the first porous vitreous layer. In the fourth step, the first and the second porous vitreous layers are sintered. In this case, the shield layer with a higher bulk density hinders the GeO2 component which has evaporated from the second porous vitreous layer from diffusing into the first porous vitreous layer.
Description
; L.
A Method for Fabricating An Optical Waveguide BAC~GROUND OF THE INVENTION
Field of the Invention This invention relates to a process for forming an optical film structure for an optical waveguide and the optical waveguide by means of Flame Hydrolysis Deposition (FHD).
Related Background Art FIGs. lA-lC show fabricating steps o~ a conventional process f~r fabricating a ~ilm structure for an optical waveguide having under and over cladding layers and a core surrounded by them. In the step shown in FIG. lA, a first porous vitreous layer (SiO2+B203+P2o5) to be the under cladding layer 20 is made o~ SiC14> BC13 and POC13 on a substrate. In the step shown in FIG. lB, a second porous vitreous layer (SiOz+GeO2+B203+P20s) to be the core layer 30 is formed o~ SiC14, GeC14, BC13 and POC13 fed from a burner, on the substrate. In the step of FIG.
lC, all the porous vitreous layer are sintered to be transparent. Subsequently the transparent core layer 30 is patterned as required, and the over cladding layer(not shown) is formed thereon.
But in this process for forming optical waveguide films, when all the porous vitreous layers are sintered, the GeO2 component o F the porous vitreous layer to be the , , ~
- æ~ fi~
1 core layer 30, i.e., core soot, adversely evaporates into the under cladding layer 20. This results in a problem that the GeO2 component which has evaporated downward diffuses into the under cladding layer 20, and the interface between the core layer 30 and the cladding layer cannot be accurately controlled. FIG. lC shows such state.
SUMMARY OF THE INVENTION
An object of this invention is to provide a process for forming optical waveguide films, which can accurately control the core/the cladding layer interface.
A process for forming an optical film structure for an optical waveguide according to this invention comprises the first step of depositing glass soot on a substrate by FHD to form a first porous vitreous layer to be a under cladding layer while increasing a bulk density of an upper part of the under cladding layer, to form the under cladding layer having the upper part with a bulk density above a set bulk density;
the second step of depositing by ~HD soot with a refractive index increasing dopant added to on the first porous vitreous layer to form a second porous vitreous layer to be a core layer; and the third step of forming the first and the second porous vitreous layers into transparent glasses, ,, , , . ,:
1 said set bulk density being enough to substantially prevent the dif~usion of the re~ractive index increasing dopant added to the second porous vitreous layer into the first porous vitreous layer.
A process ~or ~orming an optical waveguide comprises the above-described steps o~ the process ~or ~orming optical waveguide ~ilms followed by the fourth step of etching an optical waYeguide pattern in the second porous vitreous layer;
the fifth step o~ forming a third porous vitreous layer to be an over cladding layer on the second porous vitreous layer by FHD; and the sixth step of ~orming the third porous YitreoUs layer into transparent glass may be included.
The ~irst step of this process may comprise the step o~ depositing glass soot on the substrate by FHD; and the second step o~ increasing a bulk density of at least the layer of the deposited soot above the set bulk density.
~ The ~irst step may comprise the step o~ depositing soot on the substrate by FHD so that a layer of the deposited soot has a bulk density lower than the set bulk density; and the second step o~ depositing soot said deposited soot layer by FHD so that the layer o~ the deposited soot has a bulk density lower than said set bulk density.
.
æ~h~ ~-1 The ~irst step may be ~or depositing soot on the substrate by FHD so that a layer o~ the deposited soot has a bulk density higher khan said set bulk density, to Porm the ~irst porous vitreous layer to be the under cladding layer.
The above-described process for ~orming an optical film structure ~or an optical waveguide and the process for forming an optical waveguide may be characterized by increasing the bulk density by increasing a temperature of an area of the deposited soot, by increasing a temperature of the substrate, by positioning burner Por glass synthesizing ~or use in FHD nearer to the substrate, by increasing a feed amount o~ a fuel gas to the burner, or by other means.
The above-described re~ractive index dopant may be ither of GeO2, P20~, A1203. A bulk density of at least the upper part oP the first porous vitreous layer to be the under cladding layer is above about 0.3 g/cm3. A
bulk density of at least the upper part of the Pirst porous vitreous layer is above that of the second porous vitreous layer.
As described above, according to this invention, a part o~ the first porous vitreous layer near the second porous vitreous layer has a higher bulk density. Owing to the shielding effect of the neighboring part oP a higher bulk density, a refractive index increasing .
, . '~
A Method for Fabricating An Optical Waveguide BAC~GROUND OF THE INVENTION
Field of the Invention This invention relates to a process for forming an optical film structure for an optical waveguide and the optical waveguide by means of Flame Hydrolysis Deposition (FHD).
Related Background Art FIGs. lA-lC show fabricating steps o~ a conventional process f~r fabricating a ~ilm structure for an optical waveguide having under and over cladding layers and a core surrounded by them. In the step shown in FIG. lA, a first porous vitreous layer (SiO2+B203+P2o5) to be the under cladding layer 20 is made o~ SiC14> BC13 and POC13 on a substrate. In the step shown in FIG. lB, a second porous vitreous layer (SiOz+GeO2+B203+P20s) to be the core layer 30 is formed o~ SiC14, GeC14, BC13 and POC13 fed from a burner, on the substrate. In the step of FIG.
lC, all the porous vitreous layer are sintered to be transparent. Subsequently the transparent core layer 30 is patterned as required, and the over cladding layer(not shown) is formed thereon.
But in this process for forming optical waveguide films, when all the porous vitreous layers are sintered, the GeO2 component o F the porous vitreous layer to be the , , ~
- æ~ fi~
1 core layer 30, i.e., core soot, adversely evaporates into the under cladding layer 20. This results in a problem that the GeO2 component which has evaporated downward diffuses into the under cladding layer 20, and the interface between the core layer 30 and the cladding layer cannot be accurately controlled. FIG. lC shows such state.
SUMMARY OF THE INVENTION
An object of this invention is to provide a process for forming optical waveguide films, which can accurately control the core/the cladding layer interface.
A process for forming an optical film structure for an optical waveguide according to this invention comprises the first step of depositing glass soot on a substrate by FHD to form a first porous vitreous layer to be a under cladding layer while increasing a bulk density of an upper part of the under cladding layer, to form the under cladding layer having the upper part with a bulk density above a set bulk density;
the second step of depositing by ~HD soot with a refractive index increasing dopant added to on the first porous vitreous layer to form a second porous vitreous layer to be a core layer; and the third step of forming the first and the second porous vitreous layers into transparent glasses, ,, , , . ,:
1 said set bulk density being enough to substantially prevent the dif~usion of the re~ractive index increasing dopant added to the second porous vitreous layer into the first porous vitreous layer.
A process ~or ~orming an optical waveguide comprises the above-described steps o~ the process ~or ~orming optical waveguide ~ilms followed by the fourth step of etching an optical waYeguide pattern in the second porous vitreous layer;
the fifth step o~ forming a third porous vitreous layer to be an over cladding layer on the second porous vitreous layer by FHD; and the sixth step of ~orming the third porous YitreoUs layer into transparent glass may be included.
The ~irst step of this process may comprise the step o~ depositing glass soot on the substrate by FHD; and the second step o~ increasing a bulk density of at least the layer of the deposited soot above the set bulk density.
~ The ~irst step may comprise the step o~ depositing soot on the substrate by FHD so that a layer of the deposited soot has a bulk density lower than the set bulk density; and the second step o~ depositing soot said deposited soot layer by FHD so that the layer o~ the deposited soot has a bulk density lower than said set bulk density.
.
æ~h~ ~-1 The ~irst step may be ~or depositing soot on the substrate by FHD so that a layer o~ the deposited soot has a bulk density higher khan said set bulk density, to Porm the ~irst porous vitreous layer to be the under cladding layer.
The above-described process for ~orming an optical film structure ~or an optical waveguide and the process for forming an optical waveguide may be characterized by increasing the bulk density by increasing a temperature of an area of the deposited soot, by increasing a temperature of the substrate, by positioning burner Por glass synthesizing ~or use in FHD nearer to the substrate, by increasing a feed amount o~ a fuel gas to the burner, or by other means.
The above-described re~ractive index dopant may be ither of GeO2, P20~, A1203. A bulk density of at least the upper part oP the first porous vitreous layer to be the under cladding layer is above about 0.3 g/cm3. A
bulk density of at least the upper part of the Pirst porous vitreous layer is above that of the second porous vitreous layer.
As described above, according to this invention, a part o~ the first porous vitreous layer near the second porous vitreous layer has a higher bulk density. Owing to the shielding effect of the neighboring part oP a higher bulk density, a refractive index increasing .
, . '~
2 ~
1 dopant in the second porous vitreous layer, which evaporates when the first and the second porous vitreous layers are sintered, is prevented ~rom diffusing into the first porous vitreous layer. As a resulk, an optical film structure for an optical waveguide can be ~ormed with the core/the cladding optical layer interface accurately controlled.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not ~o be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way o~ illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art form this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGs. lA-lC show a conventional process for Porming an optical ~ilm structure for an optical waveguide;
FIGs. 2A-2G show a process for forming a film structure for an optical waveguide films according to the 2 ~ 3 1 present inventio~;
FIGs. 3A-3D are views ~or comparing the conventional process with the process according to the present invention;
FIG. 4 is a schematic view of a device for depositing ~ine particles of glass;
FIG. 5 is a view of a refractive index distribution of optical films formed by the process according to one example of the present invention;
FIG. 6 is a view o~ a refractive index distribution of optical waveguide films formed by the process according to one control;
FIG. 7 is a view showing relationships between dif~usion ratios of Ge and bulk densities of the porous vitreous layer to be the under cladding layer; and FIG. 8 is a view de~ining a parameter X ~or a diffusion ratio of Ge.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The principle of this invention will be brie~ed below before exampIes o~ this invention are explained.
FIGs. 2A-2G show fabrication steps of the process for forming opti.cal waveguide having a under cladding layer, a over cladding layer and a core surrounded by them according to the present invention. In the step shown in Fig. 2A, a burner 4 for glass synthesis scans over the sur~ace of a substrate 1 while being ~ed with a .
... ..
, .
4 ~ ~-1 fuel and raw material gasses. Fine particles o~ quartz glass synthesized in the burner 4 is fed onko the substrate 1 on flames. Thus, a first porous cladding layer 5 to be an under cladding layer 50 is uniformly deposited on the substrate.
In the step shown in FIG. 2B, the supply of the raw material gasses to the burner 4 is stopped, and therea~ter the flame formed only by the fuel and without including the raw material gases scans a exposed surface of the first porous vitreous layer 5 to heat the upper part of the first porus vitreous layer 5. As a result, a bulk density of the upper part o~ the first porous vitreous layer 6 is increased. This upper part with an increased bulk density functions as a shield layer against a refractive index raising dopant, such as GeO~
or others, so that the refractive index raising dopant is prevented ~rom diffusing into the first porous vitreous layer ~.
In the step shown in FIG. 2C, the burner ~ scan the substrate while being fed with the fuel and the raw material gasses with the refracti~e index raising dopant. As a result, a second porous vitreous layer 6 to be a core layer 60 is deposited uniYormly on the first porous vitreous layer 5.
In the step of FIG. 2D, the first and the second porous vitreous layers 5 and 6 are heated to become 1 vitreous as a under cladding layer 50 and the core layer 60 which are transparent. In this case, the upper part of the first porous vitreous layer 5 preven~s the evaporated refractive index raising dopant from di~fusing into the first porous vitreous layer 5. Thus an optical waveguide with the core layer 60 formed on the under cladding layer 50 can be preparad.
Subsequently in the step of FI~. 2E, the core layer 60 is etched into a required pattern for a core 61 by RIE
or others. In the step of FIG. 2F, a third porous vitreous layer 7 to be the over cladding layer 70 is deposited so as to cover the core layer 60. In the step shown in FIG. 2G, the third porous vitreous layer 7 is heated to become vitreous. Thus, an optical waveguide with the core 61 surrounded by the under and the over cladding layers 50 and 70 is prepared.
FIGs. 3A-3D show comparisons between the conventional process and the process according to the above embodiment. FIG. 3A is a graph showing bulk densities of the respective layer formed by the conventional process in which a shield layer is not formed. FIG. 3B is a graph showing bulk densities of the respective layers formed by the above mentioned process to the present invention in which the shield layer is formed in the upper part of the first porous vitreous layer 5 to be the under cladding layer 50. As shown in ..
:
, 2 -(~ g ~
1 FIG. 3B, a part o~ the higher bulk density is formed in the under cladding layer 50 which is Pormed b~ ~he above-men-tioned process. In FIG. 3B, the one-dot chain line schematically indicates an increased bulk density of the whole first porous vitreous layer 5 to be the under cladding layer 50. In this case as well, the upper part of the first porous vitreous layer 5 functions as a shield layer. It is possible to increase a bulk density of the second porous vitreous layer 6. But due to the increased bulk density, in the ~ollowing sintering step the second porous vitreous layer 6 precedes the first porous vi*reous layer 5 in becoming transparent, and it is more possible that adversely bubbles remain in the first porous vitreous layer ~.
FIG. 3C shows a distribution o~ refractive indexes of the respective layers of FIG. 3A after sintered. FIG.
3D shows a distribution of refractive indexes of the respective layers of FIG. 3B after sintered. As apparently shown, in the conventional process in which the shield layer is not formed, the refractiv~ index raising dopant diffuses into the under cladding layer 20, and the re~ractive index gradually changes at the core layer(30) / the cladding layer(20) inter~ace in optical.
On the other hand, in the above-mentioned process according to the present inventionj the refractive index raising dopant does not di~fuse into the under cladding :
, .
C~
1 layer 50, and the re~ractive index changes in a s~ep at the core layer(60) / the cladding layer(50) interPace in optical. That is, it is seen that the process according to the present invention can well control the ~ormation of the core layer(60) / the claddi.ng layer(50) inter~ace in optical.
A first embodiment according to the present invention will be explained below.
Fine glass particles deposited film o~ SiO2 as a main component are ~ormed on a Si substrate by the device of FIG. 4.
Here the device of FIG. 4 ~or depositing fine glass particles will be explained. A reaction vessel has the bottom formed in a rotary turntable 11 (o~ a 60-mm diameter~. A plurality o~ substrate 1 (silicon wafers o~
a 3-inch (~75 mm~ diameter) on which fine glass particles - should be deposited by tha burner 4 are placed in the vessel 12. An exhaust pipe 13 is provided for drawing out fine glass particles which have not been deposited on the substrates 1, and exhaust gas from the vessel 12.
The turn-table 11 on which the substrates 1 are mounted on is rotated by a motor (not shown) around respect to a center axis of the reaction vessel 12. The burner 4 reciprocates in the radial direction of the turn-table 11. Thus fine glass particles can be uniformly deposited on the substrates 1. In the bottom of the turn~table 11 - . . ~ ~ ., -, - ~ : ~ . :
2 ~
1 there is provided a heater 14 for uniformly heating the substrates 1 mounted on the turn-table 11.
Vsing this device, fine glass particles for forming optical waveguide films are deposited. The turn-table 11 is rotated at a speed of 10 rpm while a fuel and raw material gasses are being fed to th~ burner 4 for synthesizing fine glass particles. On the other hand, the burner 4 is reciprocated over a 150-mm distance in the radial direction of the turn-table 11 at a speed of 30 mm/min. Thus fine glass particle layers are uniformly deposited on the silicon wafers, which are to be the substrates 1. At this time the silicon wafers are heated up to about 680 C by the heater 14 in the bottom of the turn-table 11.
In this case, the fuel and the raw materials to be fed to the burner 4 for the first step o~ forming a fine glass particle layer to be the under cladding layer 50 were as follows. The feeding time of the fuel and the raw ma-terials was 10 minutes.
SiC14 : 60 cc/min.
BC13 : 5 cc/min.
POC13 : 3 cc/min.
H2 : 4 l/min.
2 : 6 l~min.
Ar : 3 l/min.
The fuel and the raw materials to be fAd to the 2 g~
1 ~urner 4 ~or the second step o~ ~orming a glass ~ine particle layer to be the core layer 60 were as follows.
The feeding time o~ the ~uel and the raw materials was 5 minutes.
SiCl4 : 50 cc/min.
BCl3 : 5 cc/min.
POCl3 : 3 cc/min.
GeCl4 : 14 cc/min.
H2 : 4 l/min.
2 : 6 l/min.
Ar : 3 l/min.
Subsequentlyj The silicon wa~ers with the ~ine glass particle layers ~ormed thereon were heated ~or l hour in at 1300 C in an ambient atmosphere with a He/02 partial pressure ratio of 9/1 to ~orm transparent vitreous under cladding layer 50 and the core layer 60.
FIG. 5 shows a film thickness-wise distribution of differences in specific refractiYe index between the under cladding layer 50 and the core layer 60 prepared in the ~irst embodiment and pure quart~ glass. As apparent in FIG. 6, the refracti~e index changes in a step at the core layer(60)/the cladding layer(50) inter~ace. In this case, the distribution of the refractiYe indexes were measured by a transferencs microscope.
The fine glass particle layer ~or the under cladding layer 50 and that ~or the core layer 60~ that is, the 2~
1 first and second porous layers 5 and 6, prepared in the first embodiment respectively had hulk densities o~ 0,32 g/cm3 and 0.35 g/cm3. That is, the bulk denslties o~ the glass fine particle layers for the under cladding layer 50 and the core layer 60 prepared in the ~irst embodiment are generally higher. It is considered that owing to such increased bulk density of the glass fine particle layer, a good interface between the core layer 60 and the cladding layer interface could be prepared. In this case, the determination of the bulk densities were conducted by comparing thicknesses of the glass fine layers and an increase of a weight of the silicon wa~er between the first embodiment and a control sample.
A second embodiment of this invention will be explained below. The second embodiment is substantially the same as the first embodiment. But int he second step of forming the glass fine particle layer, that is, the second porous vitreous layer 6, ~or the core layer 60, the feed amount of H2 was decreased to 3 1/min., and that of GeC14 was decreased to 10 cc/min. The feed amount of GeC14 was decreased, taking into consideration that a sticking probability of the Ge increases accompanying a decrease in a feed amount of H2.
In the second embodiment as well, a satis~actory specific re~ractive indsx difference was obtained between the under cladding layer 50 and the core layer 2 ~
1 60.
The glass fine particle layer for the undsr cladding layer 60 and that for the core layer 60, that is, the first and second porous layers 5 and 6, prepared in the second embodiment respectiYely has specific bulk densities of 0.32 g/cm3 and 0.23 g/cm3. The bulk density of the glass ~ine particle layer for the under cladding layer 50 prepared in the second embodiment was generally higher, and that of the glass flne particle for the core layer 60 was also genarally higher. It is considered that owing to such increased bulk density of the glass fine particle layer for the under cladding layer 50, that is, the ~irst porous vitreous layer 5, a satis~actory interface between the core layer 60 and the cladding layer could be prepared.
A third embodiment will be briefed below. The process according to the third embodime~t is substantially the same as that according to the second em~odiment. But in the ~irst step of forming the glass fine particle layer for the under cladding layer 50, the feed amount of H2 was decreased to 3 l/min. for the initial 8 minutes and increased to 4 l/min. for the last 2 minutes. subsequently in the same second step as in the second embodiment, the glass fine particle layer for the core layer 60 was formed.
The difference in specific refractive index between ., :
2~
1 the under cladding layer 50 and the core layer 60 prepared in the third embodiment was as good as FIG 5.
The bulk density of the glass fine particle layer for the under cladding layer 50 prepared in the third embodiment corresponding to the initial 8 minutes was 0.19 g/cm3, and the bulk density of the part corresponding to the last 2 minutes was 0.32 g/cm3. That is, the bulk density of the glass fine particle layer for tha under cladding layer ~0 is higher only in the upper part thereof. It is considered that owing to the increase o~ the bulk density only in the upper part of the glass fine particle layer, a good interface between the core layer 60 and the cladding layer could be prepared.
Then a fourth embodimen-t of this invention will be briefed. The process according to the fourth embodiment is basically the same as that according to the third embodiment. In the ~irst step of forming the glass fine particle layer for the under cladding lay~r ~0, the feed amount of H2 was decreased to 3 l/min. for an entire period of 10 minutes. Following the first step, the feed of the raw materials were stopped with the fuel alone ~ed, i.e., with H2 fed by 4 l/min., 2 fed by 6 l/min. and Ar fed by 3 l/min., so that the glass fine particle layer for the under cladding layer ~0 deposited on the silicon wafer is heated. Then the glass fine particle layer for 1 the core layer 60 was formed in the same second step a~
in the second and the third embodiments.
The difference in speci~ic refractive index between the under cladding layer 50 and the core layer 60 prepared in the fourth embodiment was the same as FIG. 5.
The bulk density of the whole glass fine particle layer for the under cladding layer 50 prepared in the fourth embodiment was 0.27 g/cm3 immediately before the ~ormation of the glass fine particle layer for the core layer 60. It is considered that at least the uppermost part of the glass fine particle layer for the under cladding layer ~0 was heated, so that the bulk density of the uppermost part has increased. The distribution of the bulk density o~ the interior o~ the glass fine particle layer for the under cladding layer ~0 i5 not known. But since the effect of raising a bulk density by the burner with the feed of the raw materials stopped increases toward the uppermost part, the uppermos~ part of the glass fine particle layer has a bulk density abo~e 0.27 g/cm3.
Finally controls will be briefed. The forming conditions of the controls are substantially the same as those of the first to the fourth embodiments. But the ~uel and raw materials fed in the first and the second steps are diff 2 rent.
In the first step of forming a glass fine particle .
2 ~
1 layer for the under cladding layer 20, th~ ~ollowing fuels and raw materials were fed Eor 10 minutes.
SiC14 : 50 cc/min.
BC13 : 5 cc/min.
POC13 : 3 cc/min.
H2 : 3 l/min.
2 : 6 1/min.
Ar : 3 l/min.
In the second step o~ forming a glass ~ine particle layer for the core layer 60, the following fuel and raw materials were fed ~or 5 minutes.
SiC14 : 50 cc/min.
BC13 : 5 cc/min.
POC13 : 3 cc/min.
GeC14 10 cc/min.
H2 : 3 1/min.
2 : 6 l~min.
Ar : 3 l/min.
FIG. 6 shows a distribution o~ specific re$ractive indexes of the under cladding layer 20 and the core layer 30 prepared in the above-described control. As apparent in FIG. 6, the reYracti~e index smoothly changes in the core layer(30)/the cladding layer(20).
The glass fine particle layer for the under cladding layer 20 and that for the core layer 30 respectively had bulk densities of 0.19 g/cm3 and 0.23 g/cm3.
, . ~
. . .
2~
1 A method ~or measuring a bulk density o~ the glass fine particle layer will be explained bslow ~or re~erence. The explanation will be m~de with re-~erence to the control. A glass fine particle layer synthesized under the same conditions as stated above had a thickness of 330 ~m. The glass ~ine particles deposited on a 3 inch (-75 mm~) silicon wafer was totally 290 mg.
Accordingly a bulk density of the composite layer o~ the under cladding layer 20 and the core layer 30 was 0.29 /((0.033 cm) x (7.5 cm)2 x (3.14/4~) - 0.2g/cm3.
The glass ~ine particle layer ~or the under cladding layer 20 had a thickness of 230 mm and a weight of 190 mg under the same conditions as stated above. Accordingly a bulk density o~ the glass fine particle layer ~or the under cladding layer 20 was 0.19 g/(~0.023 cm) x (7.5 cm)2 x (3.14/4)) - 0.19 g/cm3 a bulk density o~ the glass ~ine particle layer for th~
under cladding layer 20 was estimated to be (0.29 g - 0.19 g)/((0.33 - 0.023)cm x (7.~ cm)2 x (3.14/4)) - 0.23 g/cm3 .
Finally the relationships between di~usion ratios o~ Ge measured by electron probe micro-analysis (EPMA) and bulk densities of the porous vitreous layer to be the under cladding layer will be explained with reference to FIG. 7. FIG. 8 de~ines a parameter X for di~usion 2 ~
1 ratios of Ge. The parameter X is a distance frQm the position where the Ge concentration is 50 to the position where the Ge concentration is 5, when it is assumed that a peak value of the Ge concentration in the core layer is 100 .
The Ge concentration measurement was conducted by cutting off the substrate with the glass films which had been formed in transparent glasses, into about 3 mm x 10 mm samples, then the end surfaces of the pieces were polished, and depth-wise Ge concentration distributions of the pieces were measured by EPMA. As such measuring samples, four kinds of samples were prepared in accordance with Embodiment 1 and Control 1, Embodiment 1 with a H2 flow rate of 4.5 l/min. in the first step, and for Embodiment 1 with a H2 flow rate of 3.~ lJmin.
This measuring results are shown in FIG. 7. The parameter X for Ge diffusion ratios defined in FIG. 8 are ta~en on the vertical axis of FIG. 7, and the bulk densities are taken on the horizontal axis. It is seen in FIG. 7 that when the bulk density of the porous vitreous layer to be the under cladding layer is above about 0.3 g/cm3, the diffusion of Ge, which is a refractive index increasing dopant, is substantially suppressed substantially within a measuring error (~~m~.
This invantion is not limited to the above-described embodiments.
~8~
1 In the ~irst to the -third embodiments, a bulk density of the porous vitreous layer is increased by increasing a feed amount of a ~uel gas (H2 in these cases) to the burner. In the ~ourth embodiment, a bulk density of the porous vitreous layer is raised by depositing soot o~ a low bulk density and heating the surface by the burner. The bulk density is controlled by another method in which a substrate temperature at which the soot sticks is raised. A substrate temperature is raised by the above-described heater in the bottom of the turntable, or by heating from above by a heater, a lamp or other means.
In further another possible method for raising a bulk density, in addition to the burner ~or synthesizing the glass, another burner is provided for the exclusive purpose of heating to assist the former burner in heating the substrate. In a different method it is possible that ~ollowing sticking of the soot and the formation o~ the porous glass ~itreous layer, a substrate temperature is raised by heating by the lower heater in the bottom of the turntable, the upper heater, the lamp or other means so as to increase a bulk density. Otherwise, the burner ~or synthesizing the glass may be brought near to the substrate upon sticking the soot so as to raise a substrate temperature.
The refractive inde~ raising dopan-t is not limited 2 ~
1 to GeO2, and instead P205, A1203 or others may be used A
refractive index lowering dopant may be added to a material of the cladding layer.
The substrate is not limited to a Si substrate, and instead A1203 substrates, SiC substrates, ZrO2 substrates, etc. may be used.
From the invention thus described, it will be obvious that the invention may be varied in many ways.
Such variations are not to be regarded as a departure from the spirit and scope of the invention~ and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
:
; ~
1 dopant in the second porous vitreous layer, which evaporates when the first and the second porous vitreous layers are sintered, is prevented ~rom diffusing into the first porous vitreous layer. As a resulk, an optical film structure for an optical waveguide can be ~ormed with the core/the cladding optical layer interface accurately controlled.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not ~o be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way o~ illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art form this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGs. lA-lC show a conventional process for Porming an optical ~ilm structure for an optical waveguide;
FIGs. 2A-2G show a process for forming a film structure for an optical waveguide films according to the 2 ~ 3 1 present inventio~;
FIGs. 3A-3D are views ~or comparing the conventional process with the process according to the present invention;
FIG. 4 is a schematic view of a device for depositing ~ine particles of glass;
FIG. 5 is a view of a refractive index distribution of optical films formed by the process according to one example of the present invention;
FIG. 6 is a view o~ a refractive index distribution of optical waveguide films formed by the process according to one control;
FIG. 7 is a view showing relationships between dif~usion ratios of Ge and bulk densities of the porous vitreous layer to be the under cladding layer; and FIG. 8 is a view de~ining a parameter X ~or a diffusion ratio of Ge.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The principle of this invention will be brie~ed below before exampIes o~ this invention are explained.
FIGs. 2A-2G show fabrication steps of the process for forming opti.cal waveguide having a under cladding layer, a over cladding layer and a core surrounded by them according to the present invention. In the step shown in Fig. 2A, a burner 4 for glass synthesis scans over the sur~ace of a substrate 1 while being ~ed with a .
... ..
, .
4 ~ ~-1 fuel and raw material gasses. Fine particles o~ quartz glass synthesized in the burner 4 is fed onko the substrate 1 on flames. Thus, a first porous cladding layer 5 to be an under cladding layer 50 is uniformly deposited on the substrate.
In the step shown in FIG. 2B, the supply of the raw material gasses to the burner 4 is stopped, and therea~ter the flame formed only by the fuel and without including the raw material gases scans a exposed surface of the first porous vitreous layer 5 to heat the upper part of the first porus vitreous layer 5. As a result, a bulk density of the upper part o~ the first porous vitreous layer 6 is increased. This upper part with an increased bulk density functions as a shield layer against a refractive index raising dopant, such as GeO~
or others, so that the refractive index raising dopant is prevented ~rom diffusing into the first porous vitreous layer ~.
In the step shown in FIG. 2C, the burner ~ scan the substrate while being fed with the fuel and the raw material gasses with the refracti~e index raising dopant. As a result, a second porous vitreous layer 6 to be a core layer 60 is deposited uniYormly on the first porous vitreous layer 5.
In the step of FIG. 2D, the first and the second porous vitreous layers 5 and 6 are heated to become 1 vitreous as a under cladding layer 50 and the core layer 60 which are transparent. In this case, the upper part of the first porous vitreous layer 5 preven~s the evaporated refractive index raising dopant from di~fusing into the first porous vitreous layer 5. Thus an optical waveguide with the core layer 60 formed on the under cladding layer 50 can be preparad.
Subsequently in the step of FI~. 2E, the core layer 60 is etched into a required pattern for a core 61 by RIE
or others. In the step of FIG. 2F, a third porous vitreous layer 7 to be the over cladding layer 70 is deposited so as to cover the core layer 60. In the step shown in FIG. 2G, the third porous vitreous layer 7 is heated to become vitreous. Thus, an optical waveguide with the core 61 surrounded by the under and the over cladding layers 50 and 70 is prepared.
FIGs. 3A-3D show comparisons between the conventional process and the process according to the above embodiment. FIG. 3A is a graph showing bulk densities of the respective layer formed by the conventional process in which a shield layer is not formed. FIG. 3B is a graph showing bulk densities of the respective layers formed by the above mentioned process to the present invention in which the shield layer is formed in the upper part of the first porous vitreous layer 5 to be the under cladding layer 50. As shown in ..
:
, 2 -(~ g ~
1 FIG. 3B, a part o~ the higher bulk density is formed in the under cladding layer 50 which is Pormed b~ ~he above-men-tioned process. In FIG. 3B, the one-dot chain line schematically indicates an increased bulk density of the whole first porous vitreous layer 5 to be the under cladding layer 50. In this case as well, the upper part of the first porous vitreous layer 5 functions as a shield layer. It is possible to increase a bulk density of the second porous vitreous layer 6. But due to the increased bulk density, in the ~ollowing sintering step the second porous vitreous layer 6 precedes the first porous vi*reous layer 5 in becoming transparent, and it is more possible that adversely bubbles remain in the first porous vitreous layer ~.
FIG. 3C shows a distribution o~ refractive indexes of the respective layers of FIG. 3A after sintered. FIG.
3D shows a distribution of refractive indexes of the respective layers of FIG. 3B after sintered. As apparently shown, in the conventional process in which the shield layer is not formed, the refractiv~ index raising dopant diffuses into the under cladding layer 20, and the re~ractive index gradually changes at the core layer(30) / the cladding layer(20) inter~ace in optical.
On the other hand, in the above-mentioned process according to the present inventionj the refractive index raising dopant does not di~fuse into the under cladding :
, .
C~
1 layer 50, and the re~ractive index changes in a s~ep at the core layer(60) / the cladding layer(50) interPace in optical. That is, it is seen that the process according to the present invention can well control the ~ormation of the core layer(60) / the claddi.ng layer(50) inter~ace in optical.
A first embodiment according to the present invention will be explained below.
Fine glass particles deposited film o~ SiO2 as a main component are ~ormed on a Si substrate by the device of FIG. 4.
Here the device of FIG. 4 ~or depositing fine glass particles will be explained. A reaction vessel has the bottom formed in a rotary turntable 11 (o~ a 60-mm diameter~. A plurality o~ substrate 1 (silicon wafers o~
a 3-inch (~75 mm~ diameter) on which fine glass particles - should be deposited by tha burner 4 are placed in the vessel 12. An exhaust pipe 13 is provided for drawing out fine glass particles which have not been deposited on the substrates 1, and exhaust gas from the vessel 12.
The turn-table 11 on which the substrates 1 are mounted on is rotated by a motor (not shown) around respect to a center axis of the reaction vessel 12. The burner 4 reciprocates in the radial direction of the turn-table 11. Thus fine glass particles can be uniformly deposited on the substrates 1. In the bottom of the turn~table 11 - . . ~ ~ ., -, - ~ : ~ . :
2 ~
1 there is provided a heater 14 for uniformly heating the substrates 1 mounted on the turn-table 11.
Vsing this device, fine glass particles for forming optical waveguide films are deposited. The turn-table 11 is rotated at a speed of 10 rpm while a fuel and raw material gasses are being fed to th~ burner 4 for synthesizing fine glass particles. On the other hand, the burner 4 is reciprocated over a 150-mm distance in the radial direction of the turn-table 11 at a speed of 30 mm/min. Thus fine glass particle layers are uniformly deposited on the silicon wafers, which are to be the substrates 1. At this time the silicon wafers are heated up to about 680 C by the heater 14 in the bottom of the turn-table 11.
In this case, the fuel and the raw materials to be fed to the burner 4 for the first step o~ forming a fine glass particle layer to be the under cladding layer 50 were as follows. The feeding time of the fuel and the raw ma-terials was 10 minutes.
SiC14 : 60 cc/min.
BC13 : 5 cc/min.
POC13 : 3 cc/min.
H2 : 4 l/min.
2 : 6 l~min.
Ar : 3 l/min.
The fuel and the raw materials to be fAd to the 2 g~
1 ~urner 4 ~or the second step o~ ~orming a glass ~ine particle layer to be the core layer 60 were as follows.
The feeding time o~ the ~uel and the raw materials was 5 minutes.
SiCl4 : 50 cc/min.
BCl3 : 5 cc/min.
POCl3 : 3 cc/min.
GeCl4 : 14 cc/min.
H2 : 4 l/min.
2 : 6 l/min.
Ar : 3 l/min.
Subsequentlyj The silicon wa~ers with the ~ine glass particle layers ~ormed thereon were heated ~or l hour in at 1300 C in an ambient atmosphere with a He/02 partial pressure ratio of 9/1 to ~orm transparent vitreous under cladding layer 50 and the core layer 60.
FIG. 5 shows a film thickness-wise distribution of differences in specific refractiYe index between the under cladding layer 50 and the core layer 60 prepared in the ~irst embodiment and pure quart~ glass. As apparent in FIG. 6, the refracti~e index changes in a step at the core layer(60)/the cladding layer(50) inter~ace. In this case, the distribution of the refractiYe indexes were measured by a transferencs microscope.
The fine glass particle layer ~or the under cladding layer 50 and that ~or the core layer 60~ that is, the 2~
1 first and second porous layers 5 and 6, prepared in the first embodiment respectively had hulk densities o~ 0,32 g/cm3 and 0.35 g/cm3. That is, the bulk denslties o~ the glass fine particle layers for the under cladding layer 50 and the core layer 60 prepared in the ~irst embodiment are generally higher. It is considered that owing to such increased bulk density of the glass fine particle layer, a good interface between the core layer 60 and the cladding layer interface could be prepared. In this case, the determination of the bulk densities were conducted by comparing thicknesses of the glass fine layers and an increase of a weight of the silicon wa~er between the first embodiment and a control sample.
A second embodiment of this invention will be explained below. The second embodiment is substantially the same as the first embodiment. But int he second step of forming the glass fine particle layer, that is, the second porous vitreous layer 6, ~or the core layer 60, the feed amount of H2 was decreased to 3 1/min., and that of GeC14 was decreased to 10 cc/min. The feed amount of GeC14 was decreased, taking into consideration that a sticking probability of the Ge increases accompanying a decrease in a feed amount of H2.
In the second embodiment as well, a satis~actory specific re~ractive indsx difference was obtained between the under cladding layer 50 and the core layer 2 ~
1 60.
The glass fine particle layer for the undsr cladding layer 60 and that for the core layer 60, that is, the first and second porous layers 5 and 6, prepared in the second embodiment respectiYely has specific bulk densities of 0.32 g/cm3 and 0.23 g/cm3. The bulk density of the glass ~ine particle layer for the under cladding layer 50 prepared in the second embodiment was generally higher, and that of the glass flne particle for the core layer 60 was also genarally higher. It is considered that owing to such increased bulk density of the glass fine particle layer for the under cladding layer 50, that is, the ~irst porous vitreous layer 5, a satis~actory interface between the core layer 60 and the cladding layer could be prepared.
A third embodiment will be briefed below. The process according to the third embodime~t is substantially the same as that according to the second em~odiment. But in the ~irst step of forming the glass fine particle layer for the under cladding layer 50, the feed amount of H2 was decreased to 3 l/min. for the initial 8 minutes and increased to 4 l/min. for the last 2 minutes. subsequently in the same second step as in the second embodiment, the glass fine particle layer for the core layer 60 was formed.
The difference in specific refractive index between ., :
2~
1 the under cladding layer 50 and the core layer 60 prepared in the third embodiment was as good as FIG 5.
The bulk density of the glass fine particle layer for the under cladding layer 50 prepared in the third embodiment corresponding to the initial 8 minutes was 0.19 g/cm3, and the bulk density of the part corresponding to the last 2 minutes was 0.32 g/cm3. That is, the bulk density of the glass fine particle layer for tha under cladding layer ~0 is higher only in the upper part thereof. It is considered that owing to the increase o~ the bulk density only in the upper part of the glass fine particle layer, a good interface between the core layer 60 and the cladding layer could be prepared.
Then a fourth embodimen-t of this invention will be briefed. The process according to the fourth embodiment is basically the same as that according to the third embodiment. In the ~irst step of forming the glass fine particle layer for the under cladding lay~r ~0, the feed amount of H2 was decreased to 3 l/min. for an entire period of 10 minutes. Following the first step, the feed of the raw materials were stopped with the fuel alone ~ed, i.e., with H2 fed by 4 l/min., 2 fed by 6 l/min. and Ar fed by 3 l/min., so that the glass fine particle layer for the under cladding layer ~0 deposited on the silicon wafer is heated. Then the glass fine particle layer for 1 the core layer 60 was formed in the same second step a~
in the second and the third embodiments.
The difference in speci~ic refractive index between the under cladding layer 50 and the core layer 60 prepared in the fourth embodiment was the same as FIG. 5.
The bulk density of the whole glass fine particle layer for the under cladding layer 50 prepared in the fourth embodiment was 0.27 g/cm3 immediately before the ~ormation of the glass fine particle layer for the core layer 60. It is considered that at least the uppermost part of the glass fine particle layer for the under cladding layer ~0 was heated, so that the bulk density of the uppermost part has increased. The distribution of the bulk density o~ the interior o~ the glass fine particle layer for the under cladding layer ~0 i5 not known. But since the effect of raising a bulk density by the burner with the feed of the raw materials stopped increases toward the uppermost part, the uppermos~ part of the glass fine particle layer has a bulk density abo~e 0.27 g/cm3.
Finally controls will be briefed. The forming conditions of the controls are substantially the same as those of the first to the fourth embodiments. But the ~uel and raw materials fed in the first and the second steps are diff 2 rent.
In the first step of forming a glass fine particle .
2 ~
1 layer for the under cladding layer 20, th~ ~ollowing fuels and raw materials were fed Eor 10 minutes.
SiC14 : 50 cc/min.
BC13 : 5 cc/min.
POC13 : 3 cc/min.
H2 : 3 l/min.
2 : 6 1/min.
Ar : 3 l/min.
In the second step o~ forming a glass ~ine particle layer for the core layer 60, the following fuel and raw materials were fed ~or 5 minutes.
SiC14 : 50 cc/min.
BC13 : 5 cc/min.
POC13 : 3 cc/min.
GeC14 10 cc/min.
H2 : 3 1/min.
2 : 6 l~min.
Ar : 3 l/min.
FIG. 6 shows a distribution o~ specific re$ractive indexes of the under cladding layer 20 and the core layer 30 prepared in the above-described control. As apparent in FIG. 6, the reYracti~e index smoothly changes in the core layer(30)/the cladding layer(20).
The glass fine particle layer for the under cladding layer 20 and that for the core layer 30 respectively had bulk densities of 0.19 g/cm3 and 0.23 g/cm3.
, . ~
. . .
2~
1 A method ~or measuring a bulk density o~ the glass fine particle layer will be explained bslow ~or re~erence. The explanation will be m~de with re-~erence to the control. A glass fine particle layer synthesized under the same conditions as stated above had a thickness of 330 ~m. The glass ~ine particles deposited on a 3 inch (-75 mm~) silicon wafer was totally 290 mg.
Accordingly a bulk density of the composite layer o~ the under cladding layer 20 and the core layer 30 was 0.29 /((0.033 cm) x (7.5 cm)2 x (3.14/4~) - 0.2g/cm3.
The glass ~ine particle layer ~or the under cladding layer 20 had a thickness of 230 mm and a weight of 190 mg under the same conditions as stated above. Accordingly a bulk density o~ the glass fine particle layer ~or the under cladding layer 20 was 0.19 g/(~0.023 cm) x (7.5 cm)2 x (3.14/4)) - 0.19 g/cm3 a bulk density o~ the glass ~ine particle layer for th~
under cladding layer 20 was estimated to be (0.29 g - 0.19 g)/((0.33 - 0.023)cm x (7.~ cm)2 x (3.14/4)) - 0.23 g/cm3 .
Finally the relationships between di~usion ratios o~ Ge measured by electron probe micro-analysis (EPMA) and bulk densities of the porous vitreous layer to be the under cladding layer will be explained with reference to FIG. 7. FIG. 8 de~ines a parameter X for di~usion 2 ~
1 ratios of Ge. The parameter X is a distance frQm the position where the Ge concentration is 50 to the position where the Ge concentration is 5, when it is assumed that a peak value of the Ge concentration in the core layer is 100 .
The Ge concentration measurement was conducted by cutting off the substrate with the glass films which had been formed in transparent glasses, into about 3 mm x 10 mm samples, then the end surfaces of the pieces were polished, and depth-wise Ge concentration distributions of the pieces were measured by EPMA. As such measuring samples, four kinds of samples were prepared in accordance with Embodiment 1 and Control 1, Embodiment 1 with a H2 flow rate of 4.5 l/min. in the first step, and for Embodiment 1 with a H2 flow rate of 3.~ lJmin.
This measuring results are shown in FIG. 7. The parameter X for Ge diffusion ratios defined in FIG. 8 are ta~en on the vertical axis of FIG. 7, and the bulk densities are taken on the horizontal axis. It is seen in FIG. 7 that when the bulk density of the porous vitreous layer to be the under cladding layer is above about 0.3 g/cm3, the diffusion of Ge, which is a refractive index increasing dopant, is substantially suppressed substantially within a measuring error (~~m~.
This invantion is not limited to the above-described embodiments.
~8~
1 In the ~irst to the -third embodiments, a bulk density of the porous vitreous layer is increased by increasing a feed amount of a ~uel gas (H2 in these cases) to the burner. In the ~ourth embodiment, a bulk density of the porous vitreous layer is raised by depositing soot o~ a low bulk density and heating the surface by the burner. The bulk density is controlled by another method in which a substrate temperature at which the soot sticks is raised. A substrate temperature is raised by the above-described heater in the bottom of the turntable, or by heating from above by a heater, a lamp or other means.
In further another possible method for raising a bulk density, in addition to the burner ~or synthesizing the glass, another burner is provided for the exclusive purpose of heating to assist the former burner in heating the substrate. In a different method it is possible that ~ollowing sticking of the soot and the formation o~ the porous glass ~itreous layer, a substrate temperature is raised by heating by the lower heater in the bottom of the turntable, the upper heater, the lamp or other means so as to increase a bulk density. Otherwise, the burner ~or synthesizing the glass may be brought near to the substrate upon sticking the soot so as to raise a substrate temperature.
The refractive inde~ raising dopan-t is not limited 2 ~
1 to GeO2, and instead P205, A1203 or others may be used A
refractive index lowering dopant may be added to a material of the cladding layer.
The substrate is not limited to a Si substrate, and instead A1203 substrates, SiC substrates, ZrO2 substrates, etc. may be used.
From the invention thus described, it will be obvious that the invention may be varied in many ways.
Such variations are not to be regarded as a departure from the spirit and scope of the invention~ and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
:
; ~
Claims (15)
1. A process for forming an optical film structure for an optical waveguide having a under and over cladding layers and a core surrounded by them, comprising:
the first step of depositing glass soot on a substrate by Flame Hydrolysis Deposition (FHD) to form a first porous vitreous layer to be the under cladding layer while increasing a bulk density of at least upper part of the under cladding layer, said at least upper part of said first porous layer having a predetermined bulk density;
the second step of depositing glass soot with a refractive index increasing dopant added to on the first porous vitreous layer to form a second porous vitreous layer to be the core; and the third step of making the first and the second porous vitreous layers into transparent glasses, said predetermined bulk density being enough to substantially prevent the diffusion of the refractive index increasing dopant added to the second porous vitreous layer into the first porous vitreous layer.
the first step of depositing glass soot on a substrate by Flame Hydrolysis Deposition (FHD) to form a first porous vitreous layer to be the under cladding layer while increasing a bulk density of at least upper part of the under cladding layer, said at least upper part of said first porous layer having a predetermined bulk density;
the second step of depositing glass soot with a refractive index increasing dopant added to on the first porous vitreous layer to form a second porous vitreous layer to be the core; and the third step of making the first and the second porous vitreous layers into transparent glasses, said predetermined bulk density being enough to substantially prevent the diffusion of the refractive index increasing dopant added to the second porous vitreous layer into the first porous vitreous layer.
2. A process for forming an optical waveguide having under and over cladding layers and a core surrounded by them, comprising:
the steps of forming an optical film structure on a substrate by the process for forming optical waveguide films according to claim 1;
said process further comprising:
the fourth step of etching an optical waveguide pattern in the second porous vitreous layer;
the fifth step of forming a third porous vitreous layer to be an over cladding layer on the second porous vitreous layer by FHD; and the sixth step of forming the third porous vitreous layer into transparent glass.
the steps of forming an optical film structure on a substrate by the process for forming optical waveguide films according to claim 1;
said process further comprising:
the fourth step of etching an optical waveguide pattern in the second porous vitreous layer;
the fifth step of forming a third porous vitreous layer to be an over cladding layer on the second porous vitreous layer by FHD; and the sixth step of forming the third porous vitreous layer into transparent glass.
3. A process for forming an optical film structure according to claim 1, wherein the first step comprises the step of depositing glass soot on the substrate by FHD; and the second step of increasing a bulk density of at least the layer of the deposited soot above the set bulk density.
4. A process for forming an optical film structure according to claim 1, wherein the first step comprises the step of depositing glass soot on the substrate by FHD so that a layer of the deposited soot has a bulk density lower than the set bulk density; and the second step of depositing soot said deposited soot layer by FHD so that the layer of the deposited soot has a bulk density lower than said set bulk density.
5. A process for forming an optical film structure according to claim 1, wherein the first step is for depositing glass soot on the substrate by FHD so that a layer of the deposited soot has a bulk density higher than said predetermined bulk density, to form the first porous vitreous layer to be the under cladding layer.
6. A process for forming an optical film structure according to claim 3, wherein the increase of the bulk density is conducted by raising a temperature of the soot area following the deposition of the soot.
7. A process forming an optical film structure according to claim 4, wherein said glass soot is deposited by raising a temperature of the substrate higher while the soot is being deposited than while the deposition of soot with the lower density so that the deposited soot has the bulk density above said bulk density.
8. A process for forming an optical film structure according to claim 4, wherein the soot is deposited by positioning a glass synthesizing burner for use in FHD nearer to the substrate during the deposition of the soot than during the deposition of the deposited soot layer with the lower bulk density so that the layer of the deposited soot has the bulk density above said set bulk density.
9. A process for forming an optical film structure according to claim 4, wherein the soot is deposited by feeding a larger amount of a fuel gas to a glass synthesizing burner for use in FHD
during the deposition of the soot than during the deposition of the deposited soot layer with the lower bulk density so that the layer of the deposited soot has the bulk density above said set bulk density.
during the deposition of the soot than during the deposition of the deposited soot layer with the lower bulk density so that the layer of the deposited soot has the bulk density above said set bulk density.
10. A process for forming an optical film structure according to claim 5, wherein the soot is deposited by increasing a temperature of the substrate during the deposition of the soot so that the layer of the deposited soot has the higher bulk density.
11. A process for forming an optical film structure according to claim 5, wherein the soot is deposited by positioning nearer the substrate a glass synthesizing burner for use in FHD
during the deposition of the soot so that the layer of the deposited soot has the higher bulk density.
during the deposition of the soot so that the layer of the deposited soot has the higher bulk density.
12. A process for forming an optical film structure according to claim 5, wherein the soot is deposited by feed a larger amount of a fuel gas to glass synthesizing burner for use in FHD so that the layer of the deposited sot has the higher bulk density.
13. A process for forming an optical film structure according to claim 1, wherein the refractive index increasing dopant is either of GeO2, P2O5, Al2O3.
14. A process for forming an optical film structure according to claim 1, wherein said set bulk density is about 0.3 g/cm3.
15. A process for forming an optical film structure according to claim 1, wherein said predetermined bulk density is higher than that of the second porous vitreous layer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP323093/1991 | 1991-12-06 | ||
| JP32309391 | 1991-12-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2084461A1 true CA2084461A1 (en) | 1993-06-07 |
Family
ID=18151001
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002084461A Abandoned CA2084461A1 (en) | 1991-12-06 | 1992-12-03 | Method for fabricating an optical waveguide |
Country Status (6)
| Country | Link |
|---|---|
| US (2) | US5385594A (en) |
| EP (1) | EP0545432B1 (en) |
| JP (1) | JPH05273426A (en) |
| AU (1) | AU654415B2 (en) |
| CA (1) | CA2084461A1 (en) |
| DE (1) | DE69212575T2 (en) |
Families Citing this family (45)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05273426A (en) * | 1991-12-06 | 1993-10-22 | Sumitomo Electric Ind Ltd | Production of optical waveguide film and production of optical waveguide by using the same |
| JPH07294760A (en) * | 1994-04-22 | 1995-11-10 | Sumitomo Electric Ind Ltd | Production of optical waveguide |
| JPH0854528A (en) * | 1994-08-10 | 1996-02-27 | Furukawa Electric Co Ltd:The | Production of optical waveguide |
| EP0747327B2 (en) * | 1995-06-07 | 2003-08-27 | Corning Incorporated | Method of thermally treating and consolidating silica preforms for reducing laser-induced optical damage in silica |
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| US3806223A (en) * | 1972-03-30 | 1974-04-23 | Corning Glass Works | Planar optical waveguide |
| US3934061A (en) * | 1972-03-30 | 1976-01-20 | Corning Glass Works | Method of forming planar optical waveguides |
| GB1574115A (en) * | 1978-05-18 | 1980-09-03 | Standard Telephones Cables Ltd | Optical fibre manufacture |
| US4425146A (en) * | 1979-12-17 | 1984-01-10 | Nippon Telegraph & Telephone Public Corporation | Method of making glass waveguide for optical circuit |
| JPS5781213A (en) * | 1980-11-11 | 1982-05-21 | Nippon Telegr & Teleph Corp <Ntt> | Production of thin film for optical waveguide |
| US4363647A (en) * | 1981-05-14 | 1982-12-14 | Corning Glass Works | Method of making fused silica-containing material |
| US4378985A (en) * | 1981-06-04 | 1983-04-05 | Corning Glass Works | Method and apparatus for forming an optical waveguide fiber |
| US5043002A (en) * | 1990-08-16 | 1991-08-27 | Corning Incorporated | Method of making fused silica by decomposing siloxanes |
| JPH04131805A (en) * | 1990-09-25 | 1992-05-06 | Sumitomo Electric Ind Ltd | Quartz optical waveguide and production thereof |
| DE59102740D1 (en) * | 1990-12-21 | 1994-10-06 | Kabelmetal Electro Gmbh | Method of making an optical fiber preform. |
| JPH05273426A (en) * | 1991-12-06 | 1993-10-22 | Sumitomo Electric Ind Ltd | Production of optical waveguide film and production of optical waveguide by using the same |
-
1992
- 1992-12-03 JP JP4324331A patent/JPH05273426A/en active Pending
- 1992-12-03 CA CA002084461A patent/CA2084461A1/en not_active Abandoned
- 1992-12-04 DE DE69212575T patent/DE69212575T2/en not_active Expired - Fee Related
- 1992-12-04 US US07/986,001 patent/US5385594A/en not_active Expired - Fee Related
- 1992-12-04 EP EP92120742A patent/EP0545432B1/en not_active Expired - Lifetime
- 1992-12-04 AU AU29864/92A patent/AU654415B2/en not_active Ceased
-
1994
- 1994-06-23 US US08/264,301 patent/US5556442A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| AU2986492A (en) | 1993-06-10 |
| EP0545432A1 (en) | 1993-06-09 |
| DE69212575D1 (en) | 1996-09-05 |
| AU654415B2 (en) | 1994-11-03 |
| US5385594A (en) | 1995-01-31 |
| EP0545432B1 (en) | 1996-07-31 |
| US5556442A (en) | 1996-09-17 |
| DE69212575T2 (en) | 1997-01-23 |
| JPH05273426A (en) | 1993-10-22 |
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