Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1997-11-12
1999-11-16
Yao, Sam Chuan
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156293, 156296, 385 65, 385 83, G02B 624, G02B 642
Patent
active
059850868
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the securing of an optical fibre in a V-groove formed in a substrate surface for the accurate positioning of the fibre relative to that substrate.
For the purposes of this specification, in relation to its associated optical fibre, a V-groove formed in a substrate is a groove having two inwardly inclined planar surfaces for fibre alignment against each of which the curved surface of the associated optical fibre is able to make simultaneous line contact. The V-groove may be defined in its entirety by these planar fibre alignment surfaces meeting in a line at the base of the groove, or it may take a truncated form in which the two planar fibre alignment surfaces are connected by a third surface. Typically such V-grooves, truncated or otherwise, are grooves etched to provide precisely located and oriented planar fibre alignment surfaces using photolithographic techniques involving the anisotropic etching of a crystalline substrate such as a single crystal silicon wafer.
FIG. 1 depicts a substrate 10 with such a V-groove and associated optical fibre 11. The V-groove is formed in a surface 12 of the substrate extending in an yz plane, with the groove extending in the z direction, its two planar fibre alignment surfaces being formed by planes 13 and 14. If the diameter of the fibre 11 is known, then, using the same photolithographic processing to define both the positions of the fibre alignment surfaces 13 and 14 and that of some integer 15 (such as a laser diode, photodetector or waveguide) formed on or secured to the substrate surface, a predetermined alignment of the fibre axis in relation to the integer can be brought about by positioning the curved surface of the fibre in contact with the two fibre alignment surfaces. Typically it is this alignment that is more critical in absolute magnitude terms than the magnitude of the distance separating the end of the fibre from the end of the integer 15, and this latter magnitude is capable of being adjusted by sliding the fibre along the V-groove. At least in principle, this separation distance can also be set to a predetermined value by arranging to advance the fibre until its end surface comes into contact with the end wall 16 of the V-groove.
When the optical fibre 11 is in its required position in its associated V-groove formed in substrate 10, having the curved surface of the fibre in simultaneous contact with both of the fibre alignment surfaces 13 and 14, it is generally desired to secure the fibre with some form of adhesive, which may for instance be an adhesive resin or a solder. The fibre may be secured, as depicted in FIG. 2a, with just two fillets 20 and 21 of adhesive above the lines of contact between the fibre and the fibre alignment walls. Additionally, as depicted in FIG. 2b, there may be two further fillets 22 and 23 of adhesive beneath the lines of contact between the fibre and the fibre alignment walls. Alternatively, as depicted in FIG. 2c, the place of the further fillets 22 and 23 may be taken by a single plug 24 of adhesive that completely fills, over at least a portion of the length of the groove, the space lying between the fibre and the substrate beneath the lines of contact between the fibre and the fibre alignment walls. For applying the adhesive mass to form the 24 under the fibre it may be convenient to dispense the adhesive in a slot that transversely intersects the base of the V-groove as described in the article by I P Hall entitled `Non-hermetic Encapsulation and Assembly Techniques for Optoelectronic Applications` at the 10th European Microelectronics Conference, May 14-17, 1995 Copenhagen, Denmark. (Such a slot is depicted in broken outline at 17 in FIG. 1.) A somewhat similar configuration is also to be found in WO-A-96/00 918.
The method hitherto adopted by us for securing optical fibres in V-grooves has been to clamp the fibre in position in its V-groove, and then to dispense a thermally curable epoxy adhesive resin at an elevated temperature along each side of the fibre directly from a dispenser. It
REFERENCES:
IBM Technical Disclosure Bulletin, Sep. 1981, Silicon Optical Bench For Reproducible Optical Feedback Path, pp. 1984-1985.
Northern Telecom Limited
Yao Sam Chuan
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