Classifications

• • 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
  • G02B6/12007—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 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• • 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
  • C03C14/00—Glass compositions containing a non-glass component, e.g. compositions containing fibres, filaments, whiskers, platelets, or the like, dispersed in a glass matrix
  • C03C14/008—Glass compositions containing a non-glass component, e.g. compositions containing fibres, filaments, whiskers, platelets, or the like, dispersed in a glass matrix the non-glass component being in molecular form
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/30—Optical coupling means for use between fibre and thin-film device
• • 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
  • C03C2214/00—Nature of the non-vitreous component
  • C03C2214/17—Nature of the non-vitreous component in molecular form (for molecular composites)
• • 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
  • C03C2214/00—Nature of the non-vitreous component
  • C03C2214/32—Nature of the non-vitreous component comprising a sol-gel process
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
  • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
  • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
  • G02B6/29361—Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
  • G02B6/29368—Light guide comprising the filter, e.g. filter deposited on a fibre end
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/42—Coupling light guides with opto-electronic elements
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/42—Coupling light guides with opto-electronic elements
  • G02B6/4201—Packages, e.g. shape, construction, internal or external details
  • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
  • G02B6/4212—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical element being a coupling medium interposed therebetween, e.g. epoxy resin, refractive index matching material, index grease, matching liquid or gel
• • 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
  • G02B6/24—Coupling light guides
  • G02B6/42—Coupling light guides with opto-electronic elements
  • G02B6/4201—Packages, e.g. shape, construction, internal or external details
  • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
  • G02B6/4236—Fixing or mounting methods of the aligned elements
  • G02B6/4239—Adhesive bonding; Encapsulation with polymer material

Definitions

• the field is an optically transmissive material and method that are useful in bonding two components, such as optical fibers and/or planar structures, to form an optical network
• Optical waveguide structures fabricated in planar forms can perform a variety of functions in optical light-paths These include optical coupling in various configurations, such as multi-channel star arrays, and multiplexing or demultiplexing through phasar or grating devices. Such waveguides also hold the promise of being lower in cost than discrete optical devices which are fabricated from fiber and micro-optic components In the future, they may provide a platform for hybrid, electro-optic devices
• the present invention is directed to overcoming these and other deficiencies in the art
• the present invention relates to an inorganic-organic hybrid material that comprises an extended matrix containing silicon and oxygen atoms with at least a fraction of the silicon atoms in the extended matrix being directly bonded to at least one hydrocarbon moiety
• the present invention also relates to a method of producing an article from the material which comprises preparing a material precursor comprising at least one silane selected from the group consisting of a tetraalkoxysilane, an alkyltrialkoxysilane, or an aryltrialkoxysilane and a source of a hydrocarbon moiety, at least partially hydrolyzing and condensing the precursor material to a viscosity suitable for forming the article
• the invention is an optically transmissive article, and a method of producing a bond between two transmissive components which comprises using the partially hydrolyzed and cured material as a bonding composition aligning the components in a spaced relationship to form a gap, filling the gap with the bonding composition to form a connection between the components completing hydrolysis and curing of the bonding composition under conditions effective to form a bond of an inorganic-organic, hybrid material that comprises an extended matrix containing silicon and oxygen atoms with at least a fraction of the silicon atoms
• the present invention further relates to a hydrolyzable and curable sol-gel composition
• the sol-gel composition includes at least one silane selected from the group consisting of a tetraalkoxysilane, an alkyltrialkoxysilane, and an aryltrialkoxysilane
• optically transmissive networks include optical fibers and optical planar waveguides, connected by an inorganic- organic, "hard” pigtail
• the connections thus made exhibit improved hydrative stability and resistance to temperature, pressure and humidity extremes
• the connections can also minimize back-reflection by providing a close index of refraction match to the core of the waveguide This obviates the need to make expensive, precision-machined facets in the optically transmissive materials
• they can be manufactured without the application of high heat This avoids stresses caused by differences in coefficients of thermal expansion between the components
• molded optical networks which may, optionally be laminated within a substrate, specifically designed components and like optically transmissive articles BRIEF DESCRIPTION OF THE DRAWINGS
• FIGURE 1 is a cross-sectional drawing of a joint between an optical fiber and an optical planar waveguide illustrating one form of optically transmissive article according to the present invention
• FIGURE 2 is a cross-sectional drawing illustrating a modified joint between an optical planar waveguide and an optically active component according to the present invention
• the article of the present invention is an optical network comprising at least two optically transmissive components connected with a bond
• the invention arose from research directed at bonding an optical fiber to a planar waveguide structure a practice known as "pigtaihng " Accordingly, it is so described However, its broader application will be evident
• a key feature of the invention is an improved "hard” bond for connecting optically transmissive components
• Such a bond should have a good refractive index match to the components close to 1 46 It should also have a total signal loss of not over 0 2 db
• the bond must be insensitive to hydrative effects (85° C at 85% relative humidity for thousands of hours), and must be stable over a thermal cycling range of -40° to +85° C
• the pigtail preferably has sufficient strength to support a one lb tensile load
• the bond (pigtail) must lend itself to rapid and flexible production processes For example, it may be desired to successively bond a substantial number of fibers to a multiport, planar structure In such a process, a bond desirably is made in no more than two minutes while retaining other properties
• optical fiber 2 has a portion of its polymeric coating 4 removed to expose a segment of cladding 6 Core 8, contained within cladding 6, is aligned with planar device 10, which is supported by substrate 14 of planar waveguide 12 Core 8 is optically connected to planar device 10 with bonding material 16 in accordance with the method of the present invention
• Optical fiber 2 is also attached to planar waveguide 12 with mass 18 Mass 18 contacts cladding 6 of optical fiber 2 and also bonds to substrate 14 of optical waveguide 12 Mass 18 can be a glass formed by sol-gel processes, a fired glass frit paste, or a photocured polymer
• Optical fiber 2 is also attached to planar waveguide 12 with overcoating material 20 Overcoating material 20 covers, protects and bonds to cladding 6 and polymeric material 4 of optical fiber 2 as well as bonding to substrate 14 of optical waveguide 12 This strengthens the attachment of optical fiber 2 to optical waveguide 12
• the optical network can, alternatively, include a planar optical waveguide having a slot cut therein and an optically active component inserted into the slot Suitable optically active components may modify the character of the light passing through a waveguide, such as by applying a polarizing shift, isolation, or filtering
• FIGURE 2 shows a typical configuration of a planar waveguide with such a component added Slot 22, machined into planar waveguide 24, has a depth sufficient to penetrate through overclad layer 26, through core layer 28, and, optionally, into substrate 30
• Slot 22 has a width sufficient to receive optically active component 32 Preferably, it has additional width to permit optimizing the position of optically active component 32 to minimize transmission loss
• a hydrolyzed, bonding composition 34 is applied to fill slot 22 and wet optically active component 32 The composition fills slot 22 It is cured by heating to immobilize optically active component 32 in its optimal position
• bonding material 34 matches the index of refraction of core layer 28 to minimize back-reflection
• bonding material 34 should be stable to thermal
• the method of the present invention can also be used to connect a planar waveguide with a "drop-in" optically active component as shown in FIGURE 2
• a "drop-in" optically active component as shown in FIGURE 2
• These components are typically inserted into slots machined into the surface of the planar waveguide
• These drop-in configurations require that back-reflection at the interface between the drop-in component and the planar waveguide be low
• the drop-in component typically both surfaces of the drop-in component, be optically connected to the planar waveguide
• Alignment in such an application can be accomplished actively or passively
• a drop-in component can be actively held in a loss-minimized position during contact of the components and final curing of the bonding composition
• alignment can be ensured by providing a positional slot (commonly referred to as a positioning groove), and simply inserting the drop-in component into the slot
• the contact point is a line defined by the intersection of the drop-in component and the side of the slot Curing the hydrolyzed bonding composition connects the drop-in component and the optical waveguide along this line This reduces back-reflection at the interface
• the optically transmissive components are two optical fibers
• alignment can be effected by butting the ends of the optical fibers to each other
• alignment can be effected by butting an end of the optical fiber with an edge of the planar waveguide
• the components are aligned at the contact point
• the components must be slightly spaced for bonding,
• a bonding composition This comprises a mixture of hydrolyzable precursors composed essentially of at least one alkoxysilane selected from the group consisting of tetraalkoxysilanes, alkyltrialkoyxsilanes and aryltrialkoxysilanes Optionally, it contains modifiers as noted, infra
• the mixture may be dissolved in a solvent such as an alcohol and hydrolyzed by addition of acid and water
• a solvent such as an alcohol
• the composition is aged while hydrolysis and condensation proceed to form a viscous bonding composition
• This partially hydrolyzed and condensed material is hereafter termed the "bonding composition" to contrast with the ultimate bond wherein hydrolysis and curing are essentially complete
• Tetraalkoxysilanes are silicon atoms having four alkoxy groups bound thereto The four alkoxy groups are usually the same, but this is only for convenience
• Alkoxy as used herein, is meant to include the deprotonated form of any alcohol, including aliphatic alcohols
• Alkyltrialkoxysilanes are silicon atoms having three alkoxy groups and one alkyl group bonded thereto Alkyl is also meant to include arylalkyls
• Alkyltrialkoxysilanes suitable for use in the practice of the present invention include, for example, methyltrimethoxysilane ("MTMS”) and methyltriethoxysilane ("MTES").
• Aryltrialkoxysilanes are silicon atoms having three alkoxy groups and one aryl group bonded thereto. As used herein, aryl also is meant to include alkylaryl moieties
• Aryltrialkoxysilanes suitable for use in the practice of the present invention include, for example, phenyltrimethoxysilane ("PTMS”) and phenyltriethoxysilane ("PTES”)
• the hydrolyzed bonding composition can advantageously include organic components which, on a microscopic level, modify the inorganic network formed by condensation of the silane, hydrolysis products
• the organic component can modify the network with an organo-metallic bond to a silicon atom
• the organic component can coexist as an interpenetrating, intermolecular, or intramolecular network within the inorganic network, which does not attach to a silicon atom
• Suitable organic components which can be incorporated into the hydrolyzed bonding composition include one or more hydrolysis products of inert network modifiers, active network modifiers, organic network-forming modifiers, reactive polymeric modifiers, reactive polymerizable modifiers, and non-interacting, interpenetrating network modifiers.
• Inert network modifiers include alkylalkoxysilanes and arylalkoxysilanes, particularly those having the formula (R ⁇ O ⁇ Si, wherein n is 1, 2 or 3 O R 2 is an alkoxy moiety, such as ethoxy and methoxy.
• R 1 can be an alkyl moiety or an aryl moiety, including, for example, methyl, ethyl and phenyl
• the bonding composition can include from about 0 to about 100 mole %, preferably from about 50 to about 100 mole %, more preferably from about 50 to about 96 mole % of the hydrolysis product of the inert network modifier, such as the hydrolysis product of methyltriethoxysilane Further details with respect to inert network modifiers can be found in the literature
• n Si wherein n is 1, 2 or 3 and wherein OR 2 is an alkoxy moiety
• R J can be a amine-, carboxy-, mercapto- or hydroxy-substituted alkyl or aryl moiety
• the hydrolysis product of the active network modifier is preferably present in an amount from about 1 to about 25 mole %
• the bonding composition can also include one or more hydrolysis products or organic network-forming modifiers, reactive polymeric modifiers, or reactive polymerizable modifiers
• hydrolysis products of these modifiers when polymerized, are believed to form organic networks that are covalently bonded to the inorganic network via Si-C bonds
• Organic network-forming modifiers are (substituted alkyl)alkoxysilane compounds that are substituted with groups capable of participating in reactions with other like-substituted (substituted alkyl)alkoxysilane compounds
• Suitable network-forming modifiers include those having the formula (R 4 ) compassion(R 2 0) 4-n Si, wherein n is 1, 2 or 3 and OR 2 is an alkoxy moiety, suitable examples of which are ethoxy and methoxy R can be a substituted alkyl moiety or aryl moiety, such as an alkacryloxyalkyl-, an acryloxyalkyl-, a vinyl-, or an (epoxy-substituted)alkylsilane
• the hydrolyzed bonding composition can include from about 0 to about 95 mole %, preferably from about 0 to about 50 mole % of a hydrolysis product of an organic network-forming modifier, such as the hydrolysis product of methacryloxy- propyltriethoxysilane
• the hydrolysis products of organic network- forming modifiers are preferably present in an amount of from about 20 to about 50 mole %
• Suitable photoinitiators include titanocene radical photoinitiators, such as IRGACURETM 784 or cationic ferrocmium photoinitiators, such as IRGACURETM 261 (both available from Ciba Geigy, Ardsley NY)
• the photoinitiators where employed are preferably included in the bonding composition in amounts less than about 0 8 weight percent, preferably about 0 2 to about
• Reactive polymeric modifiers are inorganic or organic polymers which are capable of participating in condensation reactions with hydrolyzed tetraalkoxysilanes, alkyltrialkoxysilanes, or aryltrialkoxysilanes
• Suitable reactive polymeric modifiers include those having the formula (R 2 0) 3 0- S ⁇ -0-(P) personally-S ⁇ -0(OR )3, or (HO)-(P) n -OH, where (P) n represents an organic polymer, such as a polytetramethylene oxide, and OR 2 is an alkoxy moiety, such as ethoxy and methoxy
• Other suitable reactive polymei ic modifiers include polydialkylsiloxanes having the formula R 5 0£S ⁇ (R 6 ) 2 -0] n R 5 , wherein n is an integer from about 2 to about 50, R 5 is a hydrogen, or an alkyl or aryl moiety, R 6 is an alkyl group, preferably a methyl group
• the reactive polymeric modifier is a polydimethylsiloxane having a molecular weight of from about 200 to about 900 g/mole, preferably about 550 g/mole
• the bonding composition can include from
• Reactive polyme ⁇ zable modifiers are substituted alkylalkoxysilane compounds which can form organic networks only in combination with a second polyme ⁇ zable component which is reactive with the substitutent on the substituted alkylalkoxysilane compound
• the second polyme ⁇ zable component may or may not be bonded to an alkoxysilane
• the bonding composition can include from about 0 to about 95 mole %, preferably from about 0 to about 50 mole % of the hydrolysis product of the reactive polyme ⁇ zable modifier
• the hydrolysis product of the reactive polymerizable modifier is preferably present in an amount of from about 20 to about 50 mole %
• These reactive polymerizable modifiers contain a hydrolytically stable silicon-carbon bond
• Non-interacting interpenetrating network modifiers are organic polymers Preferably, they do not contain groups capable of forming Si-C bonds with silicon atoms, or precursors to such organic polymers
• non-interacting, interpenetrating network modifiers can be incorporated into the bonding composition in amounts of from about 0 to about 50 mole % They may be used to impart functional character, such as to increase plasticity or to introduce photoactive polymers into the extended silicon-oxide matrix They are preferably present in an amount of from about 5 to about 25 mole % Further details with respect to these non-interacting interpenetrating network modifiers can be found, for example, in U S Patent No 5,412,016 to Sharp, which is hereby incorporated by reference Increased indices of refraction in the bond composition may be obtained by further including one or more reactive compounds, such as the alkoxide of an element selected from the group consisting of Ge, Ti, Zr, Hf, Er, Nd The alkoxides can, optionally, be hydrolyzed to their hydrolysis products
• the amount of alkoxide, and the hydrolysis products thereof, collectively present in the bonding composition depends on the refractive index desired in the bond Suitable amounts of alkoxide and hydrolysis products thereof may range from about 0 to about 25 mole %, preferably from about 0 to about 15 mole %
• the bonding composition can, optionally, contain a fluoride source, such as a hydrolysis product of a fluorosilane, for example, an alkylfluorosilane
• a fluoride source such as a hydrolysis product of a fluorosilane, for example, an alkylfluorosilane
• suitable fluoride sources such as hydrogen fluoride, ammonium bifluoride and other fluoride salts which dissociate, may be used
• the incorporation of a fluoride source is advantageous where suppression of the ca 3300 cm "1 SiO-H infrared absorption band is desired Such a case is where the material connecting the optically transmissive materials must pass infrared radiation without significant attenuation
• an aryltrifluorosilane was included in the hydrolyzable precursor composition It was found that the mixture of PDMS, MTES, PTES and PTFS could be hydrolyzed directly, that is, without the presence of a solvent
• the sol After an aging period, during which the water is consumed and the alcohol is produced, the sol is a clear liquid The sol can then by "dried” by allowing the alcohol to evaporate over several hours at room temperature The clear, colorless fluid becomes significantly more viscous, and continues to do so until it gelled The viscous liquid can be thermally treated to provide the solid gel with a total mass loss of only about 10% This permits greater flexibility in processing crack-free bonds
• Particularly preferred bonding compositions of the present invention are curable sol-gels which include a silane selected from the group consisting of a tetraalkoxysilane, an alkyltrialkoxysilane, an aryltrialkoxysilane, a trialkoxysilane, an alkacryloxypropyltrialkoxysilane and combinations thereof, in a total amount of from about 50 to about 95 mole %
• the curable sol-gel composition also includes a network modifier selected from the group consisting of a monomeric dialkyldialkoxysilane, a diacryldialkoxysilane, and a polymeric polydialkylsilane in an amount of about 4 to about 25 mole %, an aryltrifluorosilane in an amount of about 5 to about 20 mole %, a tetraalkoxytitanium in an amount of about 0 to about 10 mole % and a tetraalkoxygermanium in an amount of about
• Hydrolyzed bonding compositions can be prepared by adding water to precursor bonding compositions which contain an alkoxysilane Hydrolysis begins immediately upon the addition of water, and results in the replacement of alkoxy groups with hydroxy groups
• the rates of hydrolysis of the various silanes depend on the nature of the substitutents bonded to the silicon atoms Therefore, it can be advantageous to begin the hydrolysis process of various alkoxysilanes (or alkoxides of other elements, such as tetraethoxygermanium) separately and mix them together after some or all of the alkoxy groups have been hydrolyzed
• the amount of water added is from about 75% to about 100% of the stoichiometric amount
• Hydrolysis can be carried out using the following general procedure
• a precursor bonding composition, including a selected alkoxysilane, together with one or more of the optional additive modifiers, is dissolved in a suitable solvent
• the solvent is non-reactive with, and capable of solubilizing, all of the precursor bonding composition
• the preferred solvent is ethanol Where reaction rates of the precursors are sufficiently similar, the precursor bonding composition may be mixed and hydrolyzed directly, without a solvent
• Hydrolyzed bonding compositions containing primarily alkyl trialkoxides can be advantageously prepared by the following alternate general method
• a precursor bonding composition, including a selected alkoxysilane, together with one or more of the optional modifiers, is prepared without the addition of solvent
• Water in the desired amount is added to the precursor bonding composition
• the addition of water can be carried out at room temperature, or in a hot water bath
• the precursor bonding composition, prior to addition of water is at a temperature from about 60° C to about 80° C
• the amount of water with which the precursor bonding composition reacts is better controlled if the addition is conducted under conditions which exclude moisture in the ambient air, such as by capping the reaction vessel
• the phase separated mixture can be agitated to dissolve the water in the precursor bonding composition
• Agitation is preferably carried out in a vessel isolated from the ambient atmosphere, such as with a cap
• the system is preferably vented (if capped) and then rested, preferably isolated from the ambient atmosphere, at a temperature from room temperature up to about 100° C for a period of time from about 15 minutes to about 6 hours
• the hydrolyzed bonding composition can, optionally, be aged, preferably at room temperature and for from about 1 to about 10 days
• the hydrolysis reaction may be catalyzed by a mineral acid or an organic acid, preferably HC1
• the amount of acid used in the hydration reaction can be from about 0 to about 5%, expressed in terms of equivalents of acid per mole of water used
• a fluoride source such as PTFS
• the amount of water used in the hydrolysis reaction can be from about 10% to about 200%), expressed in terms of moles of water per moles of hydrolyzable alkoxy group
• the stoichiometric hydrolysis of one mole of alkoxy group requires 0 5 moles of water
• the amount of water is preferably from about 45% to about 55%
• the resulting hydrolyzed bonding composition can be stored at room temperature for from about 3 to about 30 days before use in connecting optically transmissive components Shelf life can frequently be extended by employing dimethylformamide as the reaction solvent, or as a cosolvent with an alcohol
• the bonding composition contains germanium or titanium
• its shelf life can be extended by adding the germanium or titanium alkoxide to the sol after hydrolysis of the alkoxy silanes is at least partially completed Shelf life can also be extended by reducing the amount of water employed in the hydrolysis process, such as from about 50% to about 25% of the stoichiometric amount.
• the amount of heat applied is dependent on the presence of solvent in the preparation
• a solvent free preparation largely avoids bubbling and cracking With a solvent present, the heat applied must be controlled It is desirable to cure the hydrolyzed bonding composition quickly However, too rapid heating can cause significant trapping of solvent as bubbles, cracking due to rapid shrinkage, or misalignment of the components being connected
• the temperature for curing is about 150° C to about 300° C , preferably 225° C to about 250° C
• the cured bonding composition is sufficiently strong to withstand normal handling
• the bonding composition can be set to spatially fix the components without complete curing
• the bonding composition can be set, for example, by exposing it to radiation Typically, this is ultraviolet light having a wavelength of from about 360 nm to about 370 nm, at a power of from about 80 W/cm 2 to about 100 W/ cm 2 , and applied for about 1 to about 5 minutes.
• the bonding material formed depends upon the components of the initial bonding composition Bonding compositions, which contain hydrolysis products of one or more modifiers, form bonding materials containing a silicon oxide matrix (i e., a Si-O- Si network), in which a portion of the silicon atoms are directly bonded to substituted or unsubstituted hydrocarbon moieties
• Bonding compositions which contain hydrolysis products of one or more modifiers, form bonding materials containing a silicon oxide matrix (i e., a Si-O- Si network), in which a portion of the silicon atoms are directly bonded to substituted or unsubstituted hydrocarbon moieties
• the hydrocarbon moieties are substituted alkyl or aryl moieties, such as those containing alkylene or arylene moieties having the formula -R-.
• the alkylene or arylene moieties are bonded on either end of silicon atoms to form Si-R-Si bonds
• the fraction of silicon atoms directly bonded to substituted or unsubstituted alkyl moieties can be from about 4% to about 100%, preferably from about 20%o to about 100%), most preferably from about 50% to about 100%
• Hydrolyzed bonding compositions which contain non-interacting, interpenetrating network modifiers or their hydrolysis products form bonding materials containing an extended silicon oxide matrix (i.e., a Si-O-Si network) and an interpenetrating, organic, polymeric matrix
• the extended silicon-oxide matrix and polymeric matrix are not bonded to one another so that substantially none of the atoms in the polymeric matrix are bonded atoms in the extended silicon-oxide matrix.
• solutions may be prepared by dissolving organo-alkoxysilanes in ethanol or diinethylformamide and bringing to reflux. A mixture of ethanol, water, and HC1 is added and the sol allowed to reflux 30 minutes The reaction vessel is then capped and cooled
• methylacryloxypropyltriethoxysilane (MEMO) for formation of intramolecular interpenetrating network via a reactive polymeric modification with ultraviolet photocure capability
• MTES methyltriethoxysilane
• PTFS tetraethoxygermanium
• TBTi tetrabutoxytitanium
• Germanium and titanium are added as alkoxides to base compositions Both Ge and Ti hydrolyze rapidly, so control is achieved by prehydrolyzing a silaneethoxy mixture with sub-stoichiometric water to form a clear fluid sol A dilute solution of the
• Mass loss in the system was found in three regions from 20° to 100°C, which is drying of solvent and excess water, from 100° to 300°C, which can be attributed primarily to water evolved from completion of hydrolysis and condensation reactions that increase the skeletal density of the gel, and from 300° to 600° C, which arises from decomposition and oxidation of non-hydrolytic organic modifiers Shrinkage stresses are expected to accompany significant mass loss, as well as skeletal densification processes Optimization of the process involves maximizing the extent of hydrolysis and condensation at low temperatures (where gel is soft and compliant) and providing sufficient stress relaxation in the dense structure to accommodate any high temperature shrinkage Fluoride gels provide higher temperature stability Their low organic content also favors low mass loss and fewer thermally activated densification events On the other hand, it is the incorporation of organic modifiers that gives structural flexibility to the gel
• the ideal index of refraction is about 1 46
• the index of refraction of the glass material commonly used for the optical fiber cores Compositional effects, such as a methyl function, or structural effects, such as porosity in the material, can significantly lower index of refraction
• small portions of the silica are replaced with germania or titania
• the index of refraction may also be varied by incorporating phenyltrialk- oxysilane, diphenyldialkoxysilane, phenyltrifluorosilane, or combinations thereof into the composition Compositions with 8% polydimethylsiloxane, between 0 and 80%) phenyltriethoxysilane and/or phenyltrifluorosilane, and the remainder methyltriethoxysilane were made and converted to clear discs heated to 250° C
• the index of refraction at 588 nm was measured by comparison with a series of standard index of refraction oils using the Becke line method Table 3 details the silicon relationship of the various compositions and their indices of refraction
• the index of refraction for these compositions may be varied between 1 39 and 1 55
• the transmission properties of the present material formulations at wavelengths of 13 10 nm and 1550 nm are particularly useful attributes
• the optical spectrum of these hybrid materials in the near infrared (IR) is dominated by vibrational overtones from the organic modifiers and from incompletely reacted silanol groups
• the formulations of the invention have been carefully designed to minimize the number of vibrational modes This renders the overtone and combination band spectrum in the near IR as uncomplicated as possible
• a low silanol content in the final material is important to minimize the presence of the undesired absorption bands
• the absorbance at the optical windows of 13 10 nm and 1550 nm is thus driven to very low levels This is particularly important since major telecommunication applications operate at these windows Even the low losses thus obtained may be significant in some cases Thus absorption tails or combination bands may still cause undue loss at the 13 10 or 1 50 nm window
• Hybrid materials can be made to reduce such absorption by using precursors with deuterium exchanged organic groups When precursors such as CD 3 S ⁇ (OC H5) 3 and are employed, the siloxane network becomes modified with CDi and C ⁇ D, groups The C-D vibrational frequencies shift to lower energies from the same C-H mode, and the overtones then are shifted as well In this manner the overall absorbance in the near IR region can be reduced This results from absorption tails being smaller, and interfering features being higher order overtones, which possess fundamentally lower intensity
• the pigtail process with present materials was evaluated by aligning two fibers and joining them with a drop of a sol A sol was prepared from a mixture of 17 parts polydimethylsilane, 21 parts methyltriethoxysilane and 62 parts tetrathoxysilane A drop of the sol was placed on the joint A brief reoptimization of the 1550 nm signal was performed The joint was then heated with a convective heat source held at a distance of about 5 cm until the joint became rigid and, then, for an additional minute
• Losses that could be expected from the hybrid joint were measured in the following manner Two fibers were aligned on an optical bench Light from a 1550 nm laser was passed through one fiber, through the air gap (25 ⁇ ), and through the second fiber with a minimal loss
• Example 2 Hard Pigtaihng Two Fibers Using MTES-Rich Bonding Compositions
• PDMS polydimethylsiloxane
• MTES methyltriethoxysilane
• PTFS phenyltrifluorosilane
• the mixture was heated to 70°C and then was mixed with 5.4 cc water
• the water initially phase separated in the mixture, but, after 20 to 30 minutes of vigorous shaking, the solution homogenized to a single phase.
• the sol was warmed for an additional 30 minutes and then cooled
• the product was a clear colorless sol with a viscosity of about 5 to 10 centipoise
• the sol was allowed to air dry for 1 day providing a sol with viscosity of 10 " poise
• Two fibers were aligned on an optical bench so that light from a 1550 nm laser passed through one fiber, through an air gap of 25 ⁇ , and then through the second fiber with minimal loss A small drop of the sol was placed onto the joint Due to the surface tension of the fiber, a slight displacement of the fiber occurred.
• the fibers were realigned to achieve a minimum optical loss through the fibers and uncured adhesive
• the joint was then exposed to a directed, heated air stream for 2 minutes to achieve a 235°C temperature and then allowed to cool.
• the cooled joint was hard and robust
• a polymeric methacrylate was used to bond the fibers to a silica chip to prevent fracture of the joint by stresses that develop from normal handling
• Example 3 Hard Pigtailing a Fiber and an Optical Waveguide
• a fiber was aligned with the core of a planar waveguide on an optical bench Light from a 1550 nm laser was passed through one fiber, through an air gap of lO ⁇ , and through the waveguide with minimal loss.
• a small drop of the sol of Example 2 was placed onto the waveguide and fiber, filling the gap Due to the surface tension of the fiber, a slight displacement of the fiber occurred
• the fiber was repositioned to achieve a minimum optical loss through the complete optical system
• the joint was then heated with a directed, heated air stream for 2 minutes to achieve a 235° C temperature Upon cooling, the joint was hard and robust
• a polymeric methacrylate was used to make a rear joint to provide mechanical toughness Optical losses were measured throughout the process and are presented in Table 5 for three chips made in this way The low losses and/or improvement in optical power demonstrate the quality of the optical joint
• This example describes loss reduction with a bonding composition in a network that provides a function in a lightpath, such as polarizing or filtering the light
• a sol having a composition of 8% PDMS, 66% MTES, 9% PTFS and 17% phenyltriethoxysilane (PTES) on a molar basis was prepared in accordance with
• the slot was cleaned, and a small drop of the bonding composition was placed on the slot completely filling the slot
• the waveguide was then heated to 250°C and cooled
• the resulting filled slot was crack free
• the transmission loss at 1 550 nm was compared to the loss with an index of refraction oil
• the transmission loss for a slot having an air gap loss of 6 0 db was reduced to 3 3 db when the slot was filled with index of refraction oil and to 3 0 db when filled with the bonding composition
• the transmission loss for a slot having an air gap loss of 7.8 db was reduced to 4 2 db when the slot was filled with index of refraction of oil and to 3 9 db when filled with the hydrolyzed bonding composition
• the low losses measured after filling the slot with the bonding composition demonstrate the quality of the optical adhesive for use with drop- in components
• Example 5 The sol composition of Example 5 was employed as a base composition Additional sols were prepared having small compositional changes Cured bond samples were produced for refractive index measurements Based on the measurements, it was determined that the refractive index was dependent on the ratio of MTES to the sum of
• the refractive index can be varied from about 1 45 to 1 47 by varying the ratio from 69 MTES 14 PTFS + 9 PTES to 63 MTES 20 PTFS + 9 PTES
• the PDMS content is maintained constant at 8%
• a fiber and planar waveguide were aligned as described in Example 3
• a drop of sol made in accordance with the composition of Example 5 was placed onto the waveguide and the fiber, filling the 5 to 10 micron gap between them
• a C0 2 laser beam was used to heat the fiber-sol-waveguide junction
• the laser beam used was about 1 to 2 watts, and was unfocused (nominal 8 mm diameter)
• a ceramic mask intercepted all but a 2 mm zone in the center of the beam, and was aligned to allow the beam to illuminate the bonding material
• the beam heated the junction to a temperature of 250° C within 30 seconds, and then was extinguished.
• the total time required to heat and cool the joint was less than two minutes Upon cooling, the joint was hard and robust
• a polymeric methacrylate-urethane formulation was used to make a rear joint
• the 1 by 4 splitter described in Example 7 was fusion spliced to fiber connected to a light source at the input and to a detector at the outputs The outputs were connected through an optical switch that allowed sequential loss measurements at 1550 nm to be acquired for all four channels
• the pigtailed chip was placed in an environmental chamber in which an 85° C temperature and 85% relative humidity condition was established The optical loss was monitored hourly to determine the effect of damp heat on the hard pigtailed joints
• Table 7 provides the excursion, defined by the difference between the maximum and minimum optical power during the test, and the drift, defined by the different between the final optical power and the starting optical power, for these four waveguides
• the results are for aging times of 650 hours
• the sol-gel bonding composition provides excursions of less than 0 15 dB and drift values of ⁇ 0 10 dB, in contrast to the values obtained with polymeric adhesives of 0 5 dB excursion and 0 2 dB drift
• Table 7 Excursion and drift during 650 hours of aging at 85 ° C. and 85% relative humidity.
• Example 7 Three pigtailed fiber-to-chip joints made as described in Example 7 were fusion spliced to fiber connected to a light source at the input and to a detector at the outputs The outputs were connected through an optical switch that allowed sequential loss measurements to be acquired for all four channels. The chip was then placed into a programmable oven and cycled from -40° to +80° C. for ten cycles.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Optics & Photonics (AREA)
• General Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Dispersion Chemistry (AREA)
• Ceramic Engineering (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Silicon Polymers (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Mechanical Coupling Of Light Guides (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=21867815

Family Applications (1)

Country Status (5)

Families Citing this family (10)

Family Cites Families (7)

• 1997
  • 1997-11-21 CA CA002274851A patent/CA2274851A1/en not_active Abandoned
  • 1997-11-21 WO PCT/US1997/021315 patent/WO1998025862A1/en not_active Application Discontinuation
  • 1997-11-21 EP EP97949533A patent/EP0956273A1/de not_active Withdrawn
  • 1997-11-21 AU AU74043/98A patent/AU723352B2/en not_active Ceased
  • 1997-11-21 JP JP52669598A patent/JP2002509564A/ja active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events