EP1476775A2 - Dispositif et procede de guide d'ondes couple a une face d'extremite - Google Patents

Dispositif et procede de guide d'ondes couple a une face d'extremite

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Publication number
EP1476775A2
EP1476775A2 EP03736438A EP03736438A EP1476775A2 EP 1476775 A2 EP1476775 A2 EP 1476775A2 EP 03736438 A EP03736438 A EP 03736438A EP 03736438 A EP03736438 A EP 03736438A EP 1476775 A2 EP1476775 A2 EP 1476775A2
Authority
EP
European Patent Office
Prior art keywords
waveguide
core
refractive index
endface
optical device
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.)
Withdrawn
Application number
EP03736438A
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German (de)
English (en)
Inventor
Bruno Paul Marc Baney
Marc Moroni
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Priority to EP03736438A priority Critical patent/EP1476775A2/fr
Publication of EP1476775A2 publication Critical patent/EP1476775A2/fr
Withdrawn legal-status Critical Current

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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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • 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
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1221—Basic optical elements, e.g. light-guiding paths made from organic materials
    • 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

Definitions

  • the present invention relates generally to optical communications devices, and more specifically to the endface coupling of waveguide devices.
  • optical communication systems messages are transmitted by electromagnetic carrier waves at optical frequencies that are generated by such sources as lasers and light-emitting diodes. There is interest in such optical communication systems because they offer several advantages over conventional communication systems.
  • One preferred device for routing or guiding waves of optical frequencies from one point to another is an optical waveguide.
  • the operation of an optical waveguide is based on the fact that when a light- transmissive medium is surrounded or otherwise bounded by an outer medium having a lower refractive index, light introduced along the axis of the inner medium substantially parallel to the boundary with the outer medium is highly reflected at the boundary, trapping the light in the inner medium and thus producing a guiding effect.
  • a wide variety of optical devices can be made which incorporate such light guiding structures as the light transmissive elements.
  • optical waveguides may support a single optical mode or multiple modes, depending on the dimensions of the inner light guiding region and the difference in refractive index between the inner medium and the surrounding outer medium.
  • Optical waveguide devices and other optical interconnect devices may be constructed from organic polymeric materials. Whereas single mode optical devices built from planar waveguides made from glass are relatively unaffected by temperature, devices made from organic polymers may show a significant variation of properties with temperature. This is due to the fact that organic polymeric materials have a relatively high thermo-optic coefficient (dn/dT). Thus, as an organic polymer undergoes a change in temperature, its refractive index changes appreciably. This property can be exploited to make active, thermally tunable or controllable devices incorporating light transmissive elements made from organic polymers.
  • a thermally tunable device is a 1 x 2 switching element activated by the thermo-optic effect.
  • light from an input waveguide may be switched between two output waveguides by the application of a thermal gradient induced by a resistive heater. Typically, the heating/cooling processes occur over the span of one to several milliseconds.
  • planar waveguide devices In order to use planar waveguide devices in optical communications systems, it is usually necessary to couple another waveguide (e.g. an optical fiber) to the planar waveguide.
  • the process of coupling the endfaces of two waveguides, such as an optical fiber and a planar waveguide, is known herein as pigtailing.
  • Pigtailing allows for the efficient, stable transfer of an optical signal from one waveguide to another.
  • the endfaces of both the planar waveguide and an optical fiber are formed at angles from the normal to the propagation axis.
  • the endfaces of the waveguide and of the fiber are optically coupled with a small gap, typically about 10-30 ⁇ m, remaining between the two.
  • An adhesive is used to fill the gap and to hold the optical fiber into place against the planar waveguide. It is desirable to provide a stable and reliable joint with as low additional loss as possible as well as low back-reflectance (and therefore a low return loss) in the device.
  • the adhesive conventionally has an index of between 1.45 and about 1.52 at 1550 nm, while the optical fiber and typically has an index of about 1.46 at 1550 nm.
  • angled endfaces typically about 8° from normal ensures that any light reflected due to index differences at the waveguide/adhesive and fiber/adhesive interfaces is not coupled into waveguide or fiber propagation modes, thus minimizing return loss.
  • a principle aspect of the invention relates to an optical device for use with an optical signal propagating therein comprising a first waveguide having a core which is terminated at an endface, in which either (a) the endface of the waveguide is uncontrolled (as hereafter explained, for instance not being smooth, not being optically flat, and/or not being at an angle optimised to avoid deleterious back-reflection) or (b) the said first waveguide a polymer waveguide or (c) both.
  • a second waveguide is terminated at an endface within about 50 ⁇ m of the endface of the first waveguide so that the waveguides are optically coupled.
  • a pigtailing material is situated in the gap between the first waveguide and the second waveguide and has a refractive index within about 0.03 of the refractive index of the core of the first waveguide.
  • the optical device for use with an optical signal propagating therein.
  • the optical device includes a polymer waveguide having a core and an endface, the core having a refractive index, the core being terminated at the endface.
  • the optical device also includes an inorganic waveguide having a core and an endface, the core of the inorganic waveguide having a refractive index, the core of the inorganic waveguide being terminated at the endface, the endface of the polymer waveguide being within about 50 ⁇ m of the endface of the inorganic waveguide, the core of the polymer waveguide being substantially optically coupled to the core of the inorganic waveguide.
  • a pigtailing material having a refractive index within about 0.03 of the refractive index of the core of polymer waveguide is situated in the gap between the polymer waveguide and the inorganic waveguide.
  • the refractive index of the core of the polymer waveguide is less than about 1.4, or greater than about 1.57 at 1550 nm.
  • the optical device for use with an optical signal propagating therein.
  • the optical device includes a polymer waveguide having a core and an endface, the core having a refractive index, the core being terminated at the endface.
  • the optical device also includes an inorganic waveguide having a core and an endface, the core of the inorganic waveguide having a refractive index, the core of the inorganic waveguide being terminated at the endface, the endface of the polymer waveguide being within about 50 ⁇ m of the endface of the inorganic waveguide, the core of the polymer waveguide being substantially optically coupled to the core of the inorganic waveguide.
  • a pigtailing material having a refractive index within about 0.03 of the refractive index of the core of polymer waveguide is situated in the gap between the polymer waveguide and the inorganic waveguide.
  • the refractive index of the core of the polymer waveguide is less than about 1.4 at 1550 nm.
  • a polymer waveguide having a core and an endface is provided, the core of the polymer waveguide having a refractive index, the core being terminated at the endface, the core having a refractive index of less than about 1.40 or greater than about 1.57 at 1550 nm.
  • An inorganic waveguide having a core and an endface is also provided, the core of the inorganic waveguide having a refractive index.
  • the endface of the polymer waveguide is aligned with the endface of the inorganic waveguide with a gap of less than 50 ⁇ m therebetween, the core of the polymer waveguide being substantially optically coupled to the core of the inorganic waveguide.
  • the gap is filled with an energy curable composition.
  • the energy curable composition is cured to yield a pigtailing material with a refractive index within about 0.03 of the refractive index of the core of the polymer waveguide.
  • Another aspect of the present invention relates to an optical device for use with an optical signal propagating therein.
  • the optical device includes a first waveguide having a core and an endface, the core of the first waveguide having a refractive index, the core being terminated at the endface, the endface of the waveguide being uncontrolled.
  • the optical device further includes a second waveguide having a core and an endface, the core of the second waveguide having a refractive index, the core of the second waveguide being terminated at the endface, the endface of the first waveguide being within about 50 ⁇ m of the endface of the second waveguide, the core of the first waveguide being substantially optically coupled to the core of the second waveguide.
  • a pigtailing material having a refractive index within about 0.03 of the refractive index of the core of the first waveguide is situated in the gap between the first waveguide and the second waveguide.
  • the devices, methods and compositions of the present invention result in a number of advantages over prior art devices, methods and compositions.
  • the devices of the present invention can exhibit a very low return loss. Further, it is possible to ensure consistent return losses from device to device and between different waveguides on a common device.
  • the adhesive compositions used in the present invention can be formulated to be especially compatible with the polymer waveguide material, thus improving adhesion. In the devices and methods of the present invention, less control of endface geometry and quality is required, simplifying manufacturing processes. Compared to prior methods, the present invention provides devices with improved return loss when using brittle, crystalline, or soft waveguide materials.
  • FIG. 1 is schematic side view of a pigtailed polymer waveguide device according to an embodiment of the present invention
  • FIG. 2 is a schematic side view of a pigtailed polymer waveguide device using an adhesive for mechanical stability according to an embodiment of the present invention
  • FIG. 3 is a schematic side view of an uncontrolled endface formed at an angle different than the angle of a substrate; and FIG. 4 is a schematic side view of a pigtailed waveguide device having an uncontrolled endface according to an embodiment of the present invention.
  • pigtailed polymer waveguide devices and methods for making pigtailed polymer waveguide devices are provided.
  • Polymer waveguides are conventionally made from a wide variety of materials. Since high concentrations of C-H bonds tend to increase optical loss at telecommunications wavelengths, it is desirable to construct waveguides from polymers without a significant concentration of C-H bonds.
  • highly fluorinated polymers may be used in polymer waveguides. Fluorination tends to decrease the refractive index of the polymer, resulting in a waveguide with a much lower refractive index than that of standard optical fiber and optical adhesives.
  • highly chlorinated polymers polymers with a high concentration of aromatic rings, and polymers with a high concentration of sulfur atoms may be used in polymer waveguides. Chlorination, aromaticity and sulfur tend to increase the refractive index of the polymer, resulting in a waveguide with a much higher effective refractive index than that of standard optical fiber and optical adhesives.
  • the present invention provides pigtailed polymer waveguides with a low and consistent return loss, as well as a method for making pigtailed polymer waveguides and adhesive compositions for use in making pigtailed polymer waveguides.
  • Optical devices of the present invention may have return losses of more negative than -40 dB, or even more negative than -50 dB.
  • polymer waveguide materials may have either very low refractive indices or very high refractive indices.
  • Low index polymer waveguides may have refractive indices of less than about 1.40, or even less than about 1.35 at 1550 nm.
  • High index polymer waveguides may have refractive indices of greater than about 1.57, or even greater than about 1.62 at 1550 nm.
  • a pigtailing material is a polymeric material that fills the gap between the endfaces of two endface-coupled waveguides.
  • the refractive index of the pigtailing material be within about 0.03 of the refractive index of the core of the polymer waveguide. It is even more desirable to have the refractive index of the pigtailing material be within about 0.01 of the refractive index of the core of the polymer waveguide.
  • the inventors surmise that the improvement in return loss variability has to do with the qualities of the endfaces of the waveguides. It is possible to dice (or "cleave") most inorganic waveguides to yield an endface with a controlled geometry, for example, with a known and controllable angle. Endfaces of inorganic waveguides may be made relatively smooth by dicing or polishing. Conversely, the softness of most polymer materials makes dicing and polishing polymer waveguides very difficult. In general, it is nearly impossible to control the angle and smoothness of the endface of a polymer waveguide prepared by dicing.
  • an optical device 20 includes a polymer waveguide 22.
  • the polymer waveguide may be made from any material system known to the skilled artisan, including, for example, highly fluorinated materials, such as those described in U.S.
  • the polymer waveguide may be fabricated using standard techniques such as spin coating, reactive ion etching, photolithography, micromolding, embossing, and transfer printing.
  • Polymer waveguide 22 has a core 24 for the propagation of an optical signal.
  • the polymer waveguide core 24 has a refractive index determined chiefly by the identity of the polymeric material from which the waveguide is made.
  • the polymer waveguide core may have a refractive index of greater than about 1.57, or even greater than about 1.62 at
  • the polymer waveguide core may have a refractive index of less than about 1.40, or even less than about 1.35 at 1550 nm.
  • highly fluorinated polymer waveguide cores may have a refractive index of about 1.34 at 1550 nm.
  • Highly aromatic thioether polymers may have a refractive index of about 1.75 at 1550 nm.
  • An endface 26 is formed in the polymer waveguide 22, with the core 24 being terminated at the endface 26.
  • the endface may be prepared, for example, by dicing.
  • the quality of the polymer endface is not critical.
  • diced polymer waveguides tend to have rough endfaces.
  • the angle of the endface may not be precisely known, and may vary along the endface. For example, for a given optical design, it may be desired to form an endface with an 8° angle to the normal of the propagation axis of the polymer waveguide core.
  • the endface resulting from dicing at an 8° angle may vary uncontrollably by several degrees and include undesirable roughness, corrugation, or other surface features.
  • uncontrolled waveguide endfaces are schematically depicted as a crooked line.
  • Optical device 20 also includes an inorganic waveguide 32.
  • Inorganic waveguide 32 may be an optical fiber, as shown in FIG. 1.
  • inorganic waveguide 32 may be a conventional single mode optical fiber.
  • inorganic waveguide 32 may be a planar waveguide.
  • the inorganic waveguide includes a core 34, having a refractive index, for the propagation of an optical signal.
  • An endface 36 is formed in the inorganic waveguide, with the core 34 being terminated at the endface.
  • the endface may be prepared, for example at a 7.3° angle to the waveguide axis normal.
  • Conventional inorganic doped silica waveguides have refractive indices of between about 1.44 and about 1.49 at 1550 nm.
  • the refractive index of the polymer waveguide core 24 need not be closely matched to the refractive index of the inorganic waveguide core 34.
  • the absolute value of the difference between the refractive index of the polymer waveguide core and the refractive index of the inorganic waveguide core may be greater than about 0.07, or even greater than about 0.10.
  • the waveguide endfaces 26 and 36 are within about 50 ⁇ m of one another and are substantially optically coupled to one another.
  • a polymeric pigtailing material 40 is a material that fills the gap between coupled waveguide endfaces.
  • the refractive index of the pigtailing material is closely matched to the refractive index of the polymer waveguide core 24.
  • the pigtailing material may have a refractive index within about 0.03 of the refractive index of the polymer waveguide core 24.
  • the pigtailing material has a refractive index within about 0.01 of the refractive index of the polymer waveguide core 24.
  • the pigtailing material preferably has adhesive properties, and serves to hold the inorganic waveguide in place against the polymer waveguide.
  • the pigtailing material situated in the gap may not have significant adhesive properties, in which case a separate adhesive 42 may be used to provide mechanical strength to the pigtailed device, as shown in FIG. 2.
  • the pigtailing material should be perfectly optically transparent.
  • relatively high loss materials e.g. 1-3 dB/cm (100-300 dB/m) can be used.
  • the gap-filling pigtailing material should be formulated to have a refractive index closely matching the refractive index of the polymer waveguide core as well as properties compatible with the polymer waveguide.
  • the gap-filling pigtailing material further has adhesive properties.
  • the monomers and polymers used to make the polymer waveguide will often be suitable for use in the gap-filling pigtailing material.
  • adhesion-enhancing additives such as organosilane coupling agents, may be combined with the monomers and polymers used in the fabrication of the polymer waveguide.
  • the polymers of the polymer waveguide are based on perfluorinated polyethers, it may be desirable to use a gap-filling pigtailing material based on perfluorinated polyethers.
  • an aromatic thiol-ene composition is used to fabricate the polymer waveguide, it may be desirable to use an aromatic thiol-ene composition as the basis of the pigtailing material.
  • the monomers and polymers used in the pigtailing material may also be designed by the skilled artisan to impart greater adhesion or cohesion to the pigtailing material.
  • a method for constructing an optical device is provided.
  • a polymer waveguide having a core and an endface, as described above, is provided.
  • the polymer waveguide endface need not have a well-controlled geometry.
  • An inorganic waveguide having a core and an endface, as described above, is provided.
  • the polymer waveguide core may have a refractive index of greater than about 1.57, or even greater than about 1.62 at 1550 nm.
  • the polymer waveguide core may have a refractive index of less than about 1.40, or even less than about 1.35 at 1550 nm.
  • the absolute value of the difference between the refractive index of the polymer waveguide core and the refractive index of the inorganic waveguide core may be greater than about 0.07, or even greater than about 0.10.
  • the endface of the polymer waveguide is aligned with the endface of the inorganic waveguide with a gap of less than 50 ⁇ m between the two.
  • the waveguide endfaces are aligned so that the core of the polymer waveguide is substantially optically coupled to the core of the inorganic waveguide.
  • This alignment may be performed passively or actively, using methods familiar to the skilled artisan.
  • the alignment may be performed using a conventional pigtailing bench equipped with two 4-axis precision stages, a light source coupled to the inorganic waveguide, and a detector coupled the polymer waveguide. Using the 4-axis stages, the relative positions of the waveguides are optimized to maximize the signal detected by the detector, thereby optimizing the coupling between the waveguide endfaces.
  • the gap formed between the endfaces is filled with an energy curable composition.
  • the energy curable composition is chosen to have, when cured, a refractive index closely matching that of the polymer waveguide core.
  • the energy curable composition may be introduced into the gap using, for example, a syringe.
  • the energy curable composition is cured using an appropriate source of energy to yield a pigtailing material.
  • actinic radiation, heat, or electron beam radiation may be used to cure the energy curable composition.
  • Some energy curable compositions may cure at ambient temperature in a reasonable time.
  • a variety of types of energy curable compositions may be used in the present invention. For example, acrylate, methacrylate, epoxy, and thiol-ene compositions may be used.
  • the resulting pigtailing material has a refractive index within about 0.03 of the refractive index of the core of the polymer waveguide.
  • the resulting pigtailing material has a refractive index within about 0.01 of the refractive index of the core of the polymer waveguide.
  • the polymer waveguide is a highly fluorinated waveguide based on the perfluorinated polyether acrylates described in U.S. Patent 6,306,563 and in commonly owned and copending U.S. Patent Application serial number 09/745,076.
  • the core of a perfluorinated polyether-based polymer waveguide has a refractive index of about 1.34 at 1550 nm.
  • Such waveguides may be pigtailed in accordance with the present invention using a gap-filling pigtailing material with a refractive index in the range of about 1.31 to about 1.37 at 1550 nm.
  • One desirable monomer for use in formulating energy curable compositions for pigtailing has the structure:
  • E is a polymerizable moiety
  • R is an aliphatic or aromatic linker moiety
  • Rf is a perfluorinated polyether moiety.
  • E may be 2-acryloxyethyl, 2-methacryloxyethyl, glycidyl or 2,3-dimercapto-1- propyl.
  • the linker moiety R may be, for example, a 1 ,5-isophoronyl moiety or a 2,4-tolylene moiety.
  • Rf may be -CF 2 0-[(CF 2 CF 2 0) m (CF 2 0) n ]-CF 2 -,
  • perfluorinated polyether urethane materials may be used to formulate acrylate, epoxy, and thiol-ene based energy curable compositions.
  • the polymer waveguide is a high refractive index polymer waveguide based on the aromatic sulfur-containing polymers described in commonly owned and copending U.S. Patent Application serial number 09/684,953 and in U.S. Patent 5,612,390.
  • the core of an aromatic sulfur-containing polymer waveguide may have a refractive index of about 1.66 at 1550 nm.
  • Such waveguides may be pigtailed in accordance with the present invention using a gap-filling pigtailing material with a refractive index in the range of about 1.63 to about 1.69 at 1550 nm.
  • a small amount of the aromatic sulfur-containing energy curable composition used to make the polymer waveguide cladding may fill the gap between the inorganic waveguide endface and the polymer waveguide endface.
  • the energy curable composition may be cured to yield the pigtailing material.
  • the pigtail may then be given mechanical strength using a conventional adhesive, as described above in connection with FIG. 2.
  • an uncontrolled endface is an endface that is sufficiently rough to degrade an optical signal of a desired wavelength, or is not formed at an angle substantially matching the endface of the substrate upon which the waveguide is constructed.
  • an uncontrolled endface may be a substantially nonplanar endface having a surface roughness, surface corrugation, or other surface features large enough to degrade an optical signal of a desired wavelength.
  • An uncontrolled endface may also be substantially planar, but formed at an angle differing by more than about 2° from the angle of the endface of the substrate upon which the waveguide is formed.
  • FIG. 3 shows a waveguide 82 built on a substrate 84.
  • the endface 86 of the waveguide 82 is formed at a substantially different angle than the endface 88 of the substrate 84.
  • polymeric waveguide devices prepared by dicing tend to have uncontrolled endfaces.
  • Waveguides made from brittle, highly stressed, or crystalline inorganic materials may also have uncontrolled endfaces upon dicing or polishing.
  • the skilled artisan will apply the teachings described in connection with the pigtailing of polymer waveguides to the more general case of pigtailing waveguides with uncontrolled endfaces.
  • Optical device 120 includes a first waveguide 122.
  • First waveguide 122 includes a core 124 for the propagation of an optical signal.
  • the refractive index of the first waveguide core 124 is determined chiefly by the identity of the material from which the first waveguide is constructed.
  • the first waveguide core 124 may have a refractive index of greater than about 1.57, or even greater than about 1.62 at 1550 nm.
  • the waveguide core 124 may have a refractive index of less than about 1.40, or even less than about 1.35 at 1550 nm.
  • An endface 126 is formed in the first waveguide 122, with the core 124 being terminated at the endface 126.
  • the endface may be prepared, for example, by dicing.
  • the endface of the first waveguide is uncontrolled, as described above, and as shown in FIG. 4 by a rough line.
  • Optical device 120 also includes a second waveguide 132.
  • Second waveguide 132 may be, for example, an optical fiber or a planar waveguide.
  • the second waveguide includes a core 134, having a refractive index, for the propagation of an optical signal.
  • An endface 136 is formed in the second waveguide, with the core 134 being terminated at the endface.
  • the endfaces of the first waveguide core 124 and the second waveguide core 134 are substantially optically coupled to one another, and the waveguide endfaces 126 and 136 are within about 50 mm of one another.
  • a polymeric pigtailing material 40 In the gap formed between the endfaces is a polymeric pigtailing material 40.
  • the refractive index of the pigtailing material is closely matched to the refractive index of the first waveguide core 124.
  • the pigtailing material may have a refractive index within about 0.03 of the refractive index of the first waveguide core 124.
  • the pigtailing material has a refractive index within about 0.01 of the refractive index of the first waveguide core 124.
  • a method for constructing an optical device is provided.
  • a first waveguide having a core and an uncontrolled endface, as described above, is provided.
  • a second waveguide having a core and an endface, as described above, is provided.
  • the first waveguide core may have a refractive index of greater than about 1.57, or even greater than about 1.62 at 1550 nm.
  • the first waveguide core may have a refractive index of less than about 1.40, or even less than about 1.35 at 1550 nm.
  • the absolute value of the difference between the refractive index of the first waveguide core and the refractive index of the second waveguide core may be greater than about 0.07, or even greater than about 0.10.
  • the endface of the first waveguide is aligned with the endface of the second waveguide with a gap of less than 50 ⁇ m between the two.
  • the waveguide endfaces are aligned so that the endface of the first waveguide is substantially optically coupled to the endface of the second waveguide.
  • This alignment may be performed passively or actively, using methods familiar to the skilled artisan.
  • the alignment may be performed using a conventional pigtailing bench equipped with two 4-axis precision stages, a light source coupled to the inorganic waveguide, and a detector coupled the polymer waveguide. Using the 4-axis stages, the relative positions of the waveguides are optimized to maximize the signal detected by the detector, thereby optimizing the coupling between the waveguide endfaces.
  • the gap formed between the endfaces is filled with an energy curable composition.
  • the energy curable composition is chosen to have, when cured, a refractive index closely matching that of the first waveguide core.
  • the energy curable composition may be introduced into the gap using, for example, a syringe.
  • the energy curable composition is cured using an appropriate source of energy to yield a pigtailing material. For example, actinic radiation, heat, or electron beam radiation may be used to cure the energy curable composition.
  • Some energy curable compositions may be cured by being exposed to ambient temperature for a specified amount of time. A variety of types of energy curable compositions may be used in the present invention.
  • the resulting pigtailing material has a refractive index within about 0.03 of the refractive index of the core of the first waveguide.
  • the resulting pigtailing material has a refractive index within about 0.01 of the refractive index of the core of the first waveguide.
  • Example 1 a suitable process for the fabrication of the polymer waveguide is described.
  • Examples 2 and 3 syntheses of novel perfluorinated polyether-based monomers are described.
  • Example 4 the synthesis of a fluorinated photoinitiator is described.
  • Example 5, 6 and 7 energy curable compositions suitable for pigtailing the polymer waveguide of Example 1 are described.
  • Example 8 the pigtailing of the polymer waveguide of Example 1 using the energy curable compositions of Examples 5, 6 and 7 is described.
  • Example 9 provides an example of a high index polymer waveguide system.
  • UV-D10 has a molecular weight of about 1200 g/mol and has the structure:
  • UV-T has a molecular weight of about 2400 g/mol and has the structure:
  • DAROCUR 1173 is 2-hydroxy-2-methyI-1-phenylpropan-1-one, and is available from E. Merck of Darmstadt, Germany.
  • IRGACURE 2959 is 1- [4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropan-1-one, and is available from Ciba Additives of Basel, Switzerland.
  • IRGACURE 907 is 2- methyl-1 -[(4-methylthio)phenyl]-2-morpholinopropan-1 -one, and is available from Ciba Additives of Basel, Switzerland.
  • IRGACURE 184 is 1- hydroxycyclohexyl phenyl ketone, and is available from Ciba Additives of Basel, Switzerland.
  • FLUOROLINK T The tetrafunctional polyol FLUOROLINK T is available from Ausimont USA, Inc., of Thorofare, NJ. FLUOROLINK T has a molecular weight of about 2200 g/mol, and has the structure:
  • FPI is a fluorinated photoiniator described in U.S. Patent No. RE35.060. FPI has the structure:
  • the process described herein was applied to the production of an array of planar polymer waveguides on a silicon wafer. This process was demonstrated to have advantages in ease of use and ease of scalability. Additionally, the process produced fabricated waveguides with high uniformity of such physical features as layer thickness and waveguide geometry, and with very low optical insertion loss at important telecommunication waveguides of roughly 1.3 ⁇ m and 1.55 ⁇ m.
  • a 100-mm diameter 4" silicon wafer with a 500 nm thick oxide layer was obtained in a clean state from the wafer manufacturer.
  • the silicon substrate was treated by soaking in 4 M NaOH solution for 1 hour, followed by rinsing under flowing de-ionized water for 15 minutes.
  • the NaOH treatment is meant to ensure complete functionalization of the silicon oxide surface with OH groups.
  • the silicon wafer was dried by blowing off excess water and baking on a 120°C hot plate for 10 minutes. Neat (3-acryloxypropyl)trichlorosilane was soaked onto a swab and then coated entirely over onto the surface of the wafer.
  • a cleanroom cloth soaked with ethanol was gently rubbed over the surface to remove any large particles resulting from the fast hydrolysis reaction of the trichlorosilane material.
  • the wafer was then flooded with ethanol and spun at 1000 rpm for 30 seconds. After inspection to ensure that no large particles remained, the wafer was annealed at 120°C for 3 minutes to assure complete cure of the (3-acryloxypropyl)trichlorosilane and to remove any residual ethanol.
  • the core mixture was 92 parts by weight UV-T, 8 parts by weight UV-8, and 1 part by weight DAROCUR 1173.
  • the cladding mixture was 100 parts by weight UV-T and 1 part by weight DAROCUR 1173.
  • the buffer mixture was 75 parts by weight UV-T, 25 parts by weight UV-D10, and 2 parts by weight FPI. These mixtures produce system components consisting of matched core and cladding with refractive indices of 1.336 and 1.329, respectively, and a buffer with a refractive index of 1.313. All mixtures were pre-filtered to eliminate particles above 0.1 micron.
  • the materials chosen were 100% solids and had viscosities of 100 to 500 cP which allowed them to be spin coated, neat, onto silicon wafers.
  • the wafer was then centered on the chuck of a spin coating apparatus.
  • a volume of 0.7 mL of a buffer material was dispensed on the wafer.
  • the puddle of monomer was spread at low rotational speed, 300 rpm, and then accelerated to 1300 rpm for 18 seconds to create a wet film that was measured to be 10 ⁇ m thick.
  • an edge bead removal cycle was carried out.
  • acetone was dispensed through a capillary tube above the edge of the spinning wafer so as to dispense onto the outer 1 cm of the wafer. The material in this region was thus removed.
  • a back-side rinse step with acetone was carried out to clean any residual material from the backside of the wafer.
  • the thickness was verified using non-contact, interferometric thin film measurements.
  • the wafer was then transferred to a vacuum-purge chamber.
  • a leak-free chamber with an internal volume of 3 liters was used.
  • the chamber was constructed of aluminum walls, VITON O-rings, and quartz window and allowed for both evacuation of air and nitrogen purging. Clamps on the box lid and a check valve were used to ensure that a positive pressure of nitrogen could be established during purging. This also ensured that no air could leak in during the purge cycle. Likewise, air could easily be eliminated in the vacuum cycle by ensuring that the chamber was leak free.
  • the chamber could be evacuated to 0.2 Torr or less with a standard rotary vein mechanical pump. For process consistency, a standard purge cycle was established. Vacuum was applied for
  • the wafer was placed on a wafer-photomask aligning jig.
  • the jig contained an integrated wafer vacuum chuck. The vacuum chuck was designed to hold the wafer flat and in a specific orientation with respect to the wafer flat. Wires, were then placed on the wafer to act as a spacer.
  • the wire was placed on the silicon wafer in the area of the edge bead removal.
  • a 25 ⁇ m wire provided a proximity spacing of approximately 7 ⁇ m.
  • a 35 ⁇ m wire provided a proximity spacing of 17 ⁇ m.
  • a wedge-shaped spacer, V_" high, was then place next to the wafer.
  • a 6" x 6" photomask was then placed, with the high resolution chrome image face down above the wafer and its alignment was ensured by the wafer-photomask alignment jig. One edge of the mask was held up by the wedge shaped spacer.
  • the mask was held away from the wafer to minimize the potential that contact of the photopolymerizable material to the mask could occur during the purge cycle.
  • the core layer was purged with more mild vacuum and purge cycles. Vacuum was applied for 1 sec at a time, reducing the vacuum to 300 Torr. The chamber was then purged back to atmospheric pressure with nitrogen. This vacuum-purge cycle was repeated 6 times, once every 20 seconds, until 100 seconds had elapsed. Finally, nitrogen purge was continued for an additional 320 seconds. The more gentle vacuum cycle prevents evaporating monomers from contaminating the photomask. After the purging was complete, the mask was lowered by moving the wedge using a vacuum- sealed linear motion feed through.
  • the mask thus rested on the wire spacers and did not contact the wafer nor the wet photopolymerizable material layers directly.
  • a collimated UV light source Using a collimated UV light source, a dose of 17 mJ/cm 2 was applied.
  • the wafer was then moved back to the spin coater, where an appropriate solvent was used to spin-develop regions of the wet core layer which had not been exposed.
  • the core ribs were analyzed using a microscope and height profiling instrument. For a rib with nominal dimensions of 6 x 6 ⁇ m, the height and width were both held within a maximum deviation of 0.2 ⁇ m across the wafer.
  • the thickness uniformity of the core was excellent. Since the wafer chuck and mask were both very flat and free of bow or warp, the width uniformity attained through the proximity exposure process was also excellent.
  • overclad material was spun on using the techniques described above. In this case, edge bead removal was optional. Since the resist did not dry during spinning, the overclad material flowed over the core ribs and planarized the surface above the core ribs quite well. The residual bump of the core rib under the overclad was about 0.5 ⁇ m tall.
  • the sample was again placed in the vacuum-purge chamber. Vacuum was applied for 30 seconds until a level of 5 Torr was reached. This step was followed by 1.5 minutes of nitrogen purging at 10 L/min. Using the 5 degree diffuser, a dose of 4400 mJ/cm 2 for was applied to the overclad and the underlying material layers. The sample was then placed in a 100°C oven for three hours to drive out volatile components.
  • Example 2 Example 2
  • This diisocyanate (3.0 g) was heated at reflux for two hours with 2.2 equivalents (0.255 g) of hydroxyethyl acrylate and 50 mg dibutyltin dilaurate in about 10 mL ethyl nonafluorobutyl ether. The reaction was followed by monitoring the disappearance of the isocyanate stretching band and the growth of the carbonyl band by FTIR. Upon completion of the reaction, the mixture was washed well with water and concentrated by rotary evaporation to yield a very viscous oil having the idealized structure:
  • This macromonomer has been given the acronym PFETMP.
  • AD5 89 parts by weight FPEDA, 10 parts by weight heptadecafluorodecyl acrylate, 0.6 parts by weight FBPI, 0.2 parts by weight IRGACURE 907, and 0.2 parts by weight IRGACURE 184.
  • This formulation is known herein as AD5.
  • the AD5 formulation was carefully outgassed under vacuum and loaded into a syringe in a nitrogen-filled glovebox.
  • the AD5 formulation is oxygen sensitive, and is best used within two hours of formulation.
  • the AD5 formulation may be cured using UV radiation to yield a polymeric material with a refractive index of about 1.36 at 1550 nm.
  • Example 6 An energy curable composition was formulated by combining
  • AD6 84 parts by weight FPEDA, 10 parts by weight UV-8, 5 parts by weight heptadecafluorodecyl acrylate, 0.6 parts by weight FBPI, 0.2 parts by weight IRGACURE 907, and 0.2 parts by weight IRGACURE 184.
  • This formulation is known herein as AD6.
  • the AD6 formulation was carefully outgassed under vacuum and loaded into a syringe in a nitrogen-filled glovebox.
  • the AD6 formulation is oxygen sensitive, and is best used within two hours of formulation.
  • the AD6 formulation may be cured using UV radiation to yield a polymeric material with a refractive index of about 1.36 at 1550 nm.
  • a three-neck flask was equipped with a Dean-Stark condenser and a magnetic stirrer. To the flask was added FLUOROLINK T (82 g) and 3-mercaptopropionic acid. To the mixture was added one drop of polyphosphoric acid and 100 mL of toluene. The flask was heated at reflux with the water formed in the esterification reaction being collected in the Dean-Stark condenser. After two days, the mixture was cooled to room temperature and triethylamine (1 mL) was added to neutralize any unreacted acid. The mixture was washed three times with a mixture of 90 g of methanol and 10 g of water. Residual solvent was removed by rotary evaporation.
  • T-SH The relatively high absorbance (0.085 cm -1 at 1550 nm) of this material was attributed to incomplete esterification; infrared spectroscopy confirmed the presence of residual hydroxyl groups.
  • This material has been named T-SH and can be described as having the structure:
  • Desirable materials have a ratio of m:n of about 1 , an average m and an average n of about 10.3.
  • An energy curable composition was formulated by combining 1.0 g UV-T, 0.8 g T-SH, 0.15 g PFETMP, 0.05 g FBPI, 0.03 g (3- acryloxypropyl)trimethoxysilane, and 0.03 g (3- glycidyloxypropyl)trimethoxysiiane.
  • This formulation is known herein as AD7.
  • the AD7 formulation was carefully outgassed under vacuum and loaded into a syringe in a nitrogen-filled glovebox.
  • the AD7 formulation has a shelf life of at least about three weeks.
  • the AD7 formulation may be cured using UV radiation to yield a polymeric material with a refractive index of about 1.34 at 1550 nm.
  • the polymer waveguide described in Example 1 was diced to provide an endface with four waveguide cores exposed. The dicing was at an 8° to the vertical, as shown in FIG. 2.
  • a fiber block based on a silicon V-groove substrate was loaded with four optical fibers (SMF 28 available from Corning Incorporated and having a core refractive index of 1.465 at 1550 nm) and diced at an 8° angle to the vertical, as shown in FIG. 4.
  • the fiber block was aligned to the waveguide cores using an active alignment process on conventional pigtailing bench equipped with two 4-axis precision stages, a light source coupled to the inorganic waveguide, and a detector coupled the polymer waveguide.
  • the relative positions of the waveguides were optimized to maximize the signal detected by the detector. This process left a gap of less than about 10 ⁇ m between the endfaces of the fibers and of the polymer waveguides.
  • the gap was filled with one of the energy curable compositions (AD5, AD6 or AD7), and the energy curable composition was cured with UV radiation from the top and the bottom of the device using a high pressure mercury lamp (-10 W/cm2) for two minutes.
  • the devices were post-baked at 65 °C for 12 hours.
  • An aromatic sulfur-containing oligomer may be prepared by heating 4,4'-thiobisbenzenethiol (3.762 g) and 1 ,3-diisopropyenylbenzene (2.142 g) in mesitylene (3.316 g) at 85 °C until reaction of the isopropenyl double bonds is complete as determined by infrared spectroscopy. Ethylene glycol dimethacrylate (0.606 g) is added, and the mixture is heated at 60°C until reaction of the thiol is complete as determined by infrared spectroscopy.
  • p-Methoxyphenol (0.008 g), thiodiethylenebis(3,5- di-te- ⁇ butyl-4-hydroxy)hydrocinnamate, available from Ciba as IRGANOX 1035 (0.146 g), (3-aminopropyl)trimethoxysilane (0.003 g), and
  • GENORAD 16 a polymerization inhibitor in acrylic acid ester available from Rahn USA (0.017 g) are added.
  • the oligomer has the putative structure
  • An energy curable composition suitable for making a high index waveguide core may be made by mixing the above oligomer solution (6.15 g) with bis(4-methacryloylthiophenyl)sulfide (3.516 g) and IRGACURE 1850 (50 wt% 1-benzoyl-1-hydroxycyclohexane + 50 wt% bis(2,5-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide), available from Ciba Additives of Basel, Switzerland (0.22 g).
  • An energy curable composition suitable for making a high index waveguide cladding may be made by mixing the above oligomer solution (5.67 g) with bis(4- methacryloylthiophenyl)sulfide (3.70 g), ethoxylated bisphenol A diacrylate, available from Sartomer as SR-349 (0.40 g), and IRGACURE 1850 (50 wt% 1-benzoyl-1-hydroxycyclohexane + 50 wt% bis(2,5- dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide), available from Ciba Additives of Basel, Switzerland (0.24 g).
  • compositions of this Example may be used in a UV embossing microreplication process in which liquid compositions are applied to a transparent substrate, patterned with a tool, and cured.
  • the tool may be on a cylindrical drum, which is rolled across the liquid composition while UV radiation is exposed to the area of the composition in contact with the tool.
  • the tool is rolled away from the cured polymer, leaving the waveguide pattern in the cured polymer composition.
  • the waveguide may be overclad with the cladding composition by spin coating followed by curing.
  • the core of this waveguide has a refractive index of about 1.652 at 1550 nm.
  • the high index polymer waveguide thus constructed may be diced, and pigtailed to an optical fiber using a pigtailing material with a refractive index in the range of about 1.62 to about 1.68 at 1550 nm.
  • the materials of the waveguide itself have good adhesion and are amenable to a pigtailing process.
  • the waveguide may be pigtailed using the cladding energy curable composition detailed above to form the pigtailing material.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Optical Integrated Circuits (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

L'invention concerne un dispositif optique dans lequel se propage un signal optique, qui comprend un premier guide d'ondes présentant un coeur qui se termine au niveau d'une face d'extrémité, dans lequel: (a) soit la face d'extrémité du guide d'ondes n'est pas commandée (par exemple n'est pas lisse, pas optiquement plate, et/ou n'est pas à un angle optimisé pour éviter une rétroréflexion nuisible); (b) soit ledit premier guide d'ondes est un guide d'ondes polymère; (c) soit les conditions (a) et (b) sont réunies. Un second guide d'ondes se termine au niveau d'une face d'extrémité à environ 50 µm de la face d'extrémité de façon que les guides d'ondes soient couplés par voie optique. Un matériau de fibre amorce est placé dans l'espacement se situant entre le premier et le second guide d'ondes et présente un indice de réfraction à environ 0,03 de celui du coeur du premier guide d'ondes. Lorsque ledit premier guide d'ondes est un guide d'ondes polymère, son coeur présente de préférence un indice de réfraction effectif soit inférieur à environ 1,4 soit supérieur à environ 1,57 (à 1550 nm).
EP03736438A 2002-02-21 2003-02-21 Dispositif et procede de guide d'ondes couple a une face d'extremite Withdrawn EP1476775A2 (fr)

Priority Applications (1)

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EP03736438A EP1476775A2 (fr) 2002-02-21 2003-02-21 Dispositif et procede de guide d'ondes couple a une face d'extremite

Applications Claiming Priority (4)

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EP02290418 2002-02-21
EP02290418A EP1338905A1 (fr) 2002-02-21 2002-02-21 Couplage des extrémités de guides d'ondes optiques
EP03736438A EP1476775A2 (fr) 2002-02-21 2003-02-21 Dispositif et procede de guide d'ondes couple a une face d'extremite
PCT/US2003/005064 WO2003079081A2 (fr) 2002-02-21 2003-02-21 Dispositif et procede de guide d'ondes couple a une face d'extremite

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EP03736438A Withdrawn EP1476775A2 (fr) 2002-02-21 2003-02-21 Dispositif et procede de guide d'ondes couple a une face d'extremite

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CN104391354B (zh) * 2014-11-21 2017-06-13 武汉邮电科学研究院 一种光纤与高折射率波导之间的耦合结构

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DE3784152T3 (de) * 1986-12-26 1997-03-20 Nippon Catalytic Chem Ind Harz mit hohem Brechungsindex, Verfahren zu seiner Herstellung und optische Materialien aus diesem Harz.
JPH0673358A (ja) * 1992-08-26 1994-03-15 Nippon Telegr & Teleph Corp <Ntt> 屈折率整合精密接着剤
AU668648B2 (en) * 1993-05-26 1996-05-09 Sumitomo Electric Industries, Ltd. Optical waveguide module and method of manufacturing the same
JP3497510B2 (ja) * 1996-01-26 2004-02-16 住友電気工業株式会社 光導波路モジュール
US5991493A (en) * 1996-12-13 1999-11-23 Corning Incorporated Optically transmissive bonding material
IT1312344B1 (it) * 1999-06-03 2002-04-15 Ausimont Spa Composizioni per film a basso indice di rifrazione.
US6306563B1 (en) * 1999-06-21 2001-10-23 Corning Inc. Optical devices made from radiation curable fluorinated compositions

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Title
See references of WO03079081A3 *

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WO2003079081A3 (fr) 2003-11-20

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