DE2633921A1 - METHOD AND DEVICE FOR OPTICAL COUPLING OF LIGHT WAVE ENERGY - Google Patents

Description

7948-76 / Kö / S

RGA 69642/69703

USSN 627,354 of October 30,1975

USSN 627,353 of October 30,1975

RGA Corporation, FeW York, F.T., Y. St-. A.

Method and apparatus for optically coupling lightwave energy

The invention relates to a method for increasing the optical efficiency in the optical coupling of lightwave energy through phase-adjusted evanescent fields between a fiber optic core of originally cylindrical shape and a planar optical waveguide arranged to cooperate with a coupler portion of the fiber optic core. she also relates to a device for optically coupling light wave energy by phase-matched evanescent fields between a coupler part of a multi-wave type I-fiber optic core and a planar optical waveguide arranged with a part of its surface in the vicinity of the coupler part is.

An optical coupler of the type that the invention seeks to improve is in U.S. Patent 3,912,363 (dated October 10, 1975). With this well-known optical coupler is the optical coupling between a fiber optic waveguide and a planar optical waveguide through measures for phase adjustment of coupled

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evanescent fields of light wave energy, the traveling in the two types of waveguide is achieved.

The invention is based on the object of the optical To improve the efficiency with which an optical coupling of light wave energy by phase matching of decaying Fields between a Paseroptik waveguide and a planar one can accomplish optical waveguide.

In a method of the type mentioned at the outset, this is achieved according to the invention in that the originally cylindrical Shape of the coupler part of the fiber optic core is deformed to a predetermined different shape, which is a better Efficiency of the light energy coupling between the fiber optic core and the planar optical waveguide results in the undeformed cylindrical fiber optic core.

A device of the type mentioned at the outset is characterized according to the invention in that the coupler part of the fiber optic core has a predetermined spatula shape due to which the lightwave energy traveling in the fiber optic core can be coupled into the planar optical waveguide.

The deformation of the coupler part of the fiber optic core, through which the efficiency of the optical coupling between that in fiber optics, which may be multi-wave type fiber optics, traveling lightwave energy and that in planar optical waveguide transporting lightwave energy is improved with only a single or a few wave types, can be done in such a way that the coupler part flattened or flattened in a direction substantially perpendicular to the plane of the planar optical waveguide and that portion of the fiber optic core in a plane substantially parallel to the plane of the planar optical waveguide Direction is expanded in a fan shape.

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The invention is described below with reference to the drawing in individually explained. Show it:

! ig. 1 shows a typical arrangement according to the prior art for the optical coupling of light wave energy between a fiber optic with a cylindrical core and a planar one Waveguide through phase-matched decaying coupled to one another ! elder, as described in the above-mentioned USA patent 3,912,363;

! ig. 2a and 2b are a side view and a plan view, respectively a deformed spatula-shaped! aser optic shape according to a first embodiment of the invention;

! ig. 3 shows a deformed spatula-shaped optical lens shape according to a second embodiment of the invention;

! ig. 4 shows an arrangement with the aid of which a laser optic with initially a cylindrical core 1 or with the spatulate shape. 2a, 2b and 3 can be deformed so that they have the wavy shape of a diffraction grating in the Surface of a planar waveguide is matched;

! ig. 5 the optical coupling between a! Aser optics, which by means of the arrangement 4 has been deformed, and a planar waveguide with surface diffraction grating; and

! ig. 6 shows another arrangement for deforming the shape of an optical core for the optical coupling of an optical optical system / a planar waveguide with a diffraction grating.

The in! Ig. 1 corresponds to the known arrangement shown in FIG according to all essential features of the arrangement. 4a and 4b of referenced U.S. Patent 3,912,363. A planar waveguide 100 in! Form of a thin film on a base 102 is provided with a surface diffraction grating 104. the Aseroptik 106, consisting of a core 108 with a cladding 110, is with one end of its core 108 in the immediate vicinity Arranged near the diffraction grating 104 of the planar waveguide 100. A! Aser optic has a cylindrical core that

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is usually circular cylindrical, but also a different one Can have a cylindrical shape. As in the aforementioned US patent 3 912 563 described in detail, there is Diffraction grating 104 of grating lines with a given line spacing, which is oriented at a predetermined angle to the core 108 are. The given distance between the lines and the predetermined one Orientation angles are chosen in such a way that perfect phase matching is achieved through decaying or attenuated fields between in the core 108 of traveling lightwave energy and in the planar waveguide 100 in a preselected direction moving light wave energy results.

Both from theoretical considerations and from experimental ones Reasons it has emerged that on the one hand both the diffraction grating part due to the different shape 104 as well as the flat part of the surface of the planar waveguide 100 and on the other hand the cylindrical shape of the Core 108 only has a relatively low optical efficiency of the coupling of light wave energy between the core 108 and planar waveguide 100 is achieved by evanescent fields. Namely, a fiber optic is generally a multi-wave type optical waveguide, while a planar optical waveguide has only a single wave type or a few Can record wave types with wave vectors parallel to the waveguide plane. In the known arrangement of FIG at best only a relatively few of the numerous total wave types of the cylindrical core wave vectors, which by evanescent fields are phase-matched to the single or the few modes of the planar optical waveguide, so that an optical coupling is established between them. This is one of the reasons for the relatively low optical efficiency of the optical coupling in the known arrangement according to FIG. 1.

It is also when a bunging grille 104 for the Phase matching is used, impossible to make an intimate touch

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or intimate contact between the cylindrical core 108 and the undulating surface of the planar waveguide 100 in the Area of the diffraction grating 104 to produce. This determines the optical efficiency with which wave energy between the Core 108 and planar waveguide 100 are coupled by phase-matched evanescent fields using a diffraction grating can be further reduced.

On the other hand, according to the invention, it can be assumed that a planar optical waveguide with "single ^M wave type is actually a device which has a continuum of wave types with wave vectors which all have the same given size, but in all possible directions parallel to the waveguide plane Namely, it then becomes possible to modify the initial cylindrical shape of the coupler portion of the core 108 so that there is effective coupling of multiple or multiple wave type lightwave energy in the core 108 to the planar waveguide 100 or vice versa through phase matched evanescent fields.

If, as shown in FIGS. 2a and 2b, the end portion of the cylindrical core of a conventional fiber optic 200 in the flattening one orthogonal direction and orthogonal in the other Direction widened or widened in a fan shape, as shown in the case of the core 202 (in Fig. 2a in side view and in Fig. 2b shown in plan view), then one can convert the different wave types of a multiple wave type fiber into a wave type distribution, which roughly corresponds to the distribution characteristic of a planar waveguide, force by one has the core 202 arranged in substantial contact with the surface of a planar waveguide so that the plane of the fan-shaped portion of Figure 2b is substantially parallel to the surface of the planar waveguide.

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It is well known that the refractive index of the core of a fiber optic is somewhat higher than that of its cladding. On the other hand, the refractive index of the core of a fiber optic is usually much lower than the refractive index of the material of the planar waveguide (which can for example consist of a thin film of lithium niobate tantalate on a lithium tantalate base). By terminating the clad 204 of the fiber optic 200 at a suitable location (determined by the relative indices of refraction) either before or a little after the taper or the tapered portion of the core 202 is made, the greater difference in the index of refraction is achieved higher order fiber optic modes are maintained between the tapered portion of the core 202 and its surroundings (air or vacuum). In another possible embodiment (not specifically shown) one can merely remove the jacket 204 from the contacting surface of the core 202 so that the coupler portion 202 remains covered by the jacket 204 on the top and sides.

The embodiment of FIG. 3 differs from that of FIGS. 2a and 2b only in that the spatula-shaped end of the Core 302 of the fiber optic 300 has a slightly different shape. Fig. Is intended to illustrate the fact that by various Formations of the flattening and widening of the spatula-shaped end of the fiber optic core a variety of different Distributions of wave vectors can be achieved, so that the execution of the desired coupling orientations reduced to the fact that only wave energy from one to a second substantially planar waveguide with relative is transmitted with high efficiency through phase-matched evanescent fields, which is simple and known.

In practice, the desired shape of the originally cylindrical core of the fiber optic 200 or 300 can thereby can be achieved by suitably heating and pressurizing the core in a polished (e.g. glassy) carbon dye,

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thereby the end of the fiber optic core within the dye to deform.

Although a fiber optic core with a spatula-shaped end, as shown for example in Figs. 2a, 2b and 3, is preferably used to Optically coupling wave energy through a diffraction grating onto a planar waveguide, as shown in Figure 1, is it is not always important that the optical coupling takes place through a diffraction grating. So you can see the spatula-shaped end of the Fiber optic core, as shown in Figures 2a, 2b and 3, in certain cases directly onto the flat surface of a planar optical waveguide without diffraction grating.

Fig. 4 illustrates one method of deforming a core 400 of a fiber optic 402 such that it is the wavy surface of a diffraction grating 404 of the planar waveguide 406 is adapted. The fiber optic core 400 can still have their original cylindrical shape or have already been deformed into a spatula shape, e.g. in 2a, 2b and 3 shown. As shown in Fig. 4, a lower press plate 408, which rests on a heating plate 410, carries the Pad 407 with the planar waveguide 406 attached to it. The fiber optic 402 is located on top of the planar waveguide 406, the core 400 being in contact with the wavy surface of the diffraction grating 404 and between the lower press plate 408 and the jacket of the fiber optics 402, an intermediate piece 412 as a support for the fiber optics 402 is arranged. An upper press plate 414 on one external force is exerted lies on top of the fiber optic 402 in contact with the core 400. The external force can be exerted by means of a weight or other pressurizing device. The angular displacement of the top Press plate 414 with respect to the horizontal is shown greatly exaggerated in FIG.

Under the influence of the heat from the heating plate 410 and des

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Pressure from the applied force softens the core material 400 (glass or plastic) and flows into the grooves of the diffraction grating 404, so that the core 4OO is a negative of the grating pattern of the diffraction grating 404 is impressed.

The heating can also take place in an oven instead of by means of the heating plate 410. In either case, as in Pig. 5 exaggerated shown, the shape of the surface of the core 400 is deformed so that it is in intimate contact with the undulating surface of the diffraction grating 404 of the planar waveguide 406 can be brought.

If desired, you can adjust the pressure and temperature at Select the embossing of the core 400 so that the core 400 coincides with the diffraction grating surface 404 of the planar waveguide 406 connected or welded. For example, a plastic fiber optic made from Dupont crofan plastic and a planar Waveguide made of lithium niobate tantalate an embossing and fusion with a hot plate temperature of 260 ° G. (500 ° F.) using the force of a weight of 4.536 kg (10 pounds) performed. If, on the other hand, the fiber optic 400 is detachable or removable should be, you can use a suitable separating connection that prevents permanent welding or gluing, use.

Another possible method of effectively deforming the coupler portion of a fiber optic core to make a intimate contact with the wavy surface of a diffraction grating in a planar waveguide is illustrated in FIG. There the coupler part of the undeformed core 600 is the Fiber optics 602 physically with the wavy surface of the diffraction grating 604 of the planar waveguide 606 on the base 607 coupled by an index matching plastic molding material 608 which is applied to the original, cylindrical coupler part of the core 600 is applied. With the material 608, the refractive index of which is equal to or higher than that of the undeformed core 600 and lower than that of the planar waveguide 606

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should, the undeformed core 600 is cast around, so that a The result is a grid pattern that matches the wavy surface of the Diffraction grating 604 of the planar waveguide 606 is connected or welded. As index matching plastic molding material you can use Oastolite AP, for example.

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Claims (11)

Claims -H). Method for increasing the optical efficiency in optical coupling of light wave energy through phase-adjusted * evanescent fields between a fiber optic core originally cylindrical in shape and a planar optical waveguide, which is arranged in such a way that it interacts with a coupler part of the fiber optic core, characterized by draws that the originally cylindrical shape of the coupler part of the fiber optic core to a predetermined other shape is deformed, which has a better efficiency '-the Light energy coupling between the fiber optic core and the planar optical waveguide yields as the undeformed one cylindrical fiber optic core. 2. The method of claim 1, wherein the fiber optic core a multi-wave type waveguide of the multi-wave energy is, characterized in that in the process of deforming the originally cylindrical Shape of the coupler part of the fiber optic core in a manner substantially perpendicular to the plane of the planar optical waveguide Direction flattened and in a direction substantially parallel to the plane of the planar optical waveguide is widened in a fan shape, such that the coupler part is deformed into a predetermined spatula-shaped shape, the a better efficiency of optical coupling of multi-wave type lightwave energy between the fiber optic and the planar optical waveguide by phase-matched evanescent Fields results. 3. The method of claim 2, wherein the planar optical waveguide is essentially a single-wave type waveguide for light wave energy with a wave vector of a given size, which moves in the planar optical waveguide, is, 709819/0665 GBiGlNAL l * 4SP £ GTED 633921 characterized in that in the process step of deforming the coupler part of the laser-optic core is deformed to a predetermined spatula shape, the different types of waves in the Paseroptik core Forcing light wave energy to move into wave types, all of which essentially have the wave vector of the given magnitude, however, see moving along various paths, all of which in the are substantially parallel to the plane of the planar optical waveguide. 4. The method according to claim 3, characterized that in the process step of deforming the special contour of the flattening and expansion of the predetermined shape is shaped so that the special orientation of the coupled from the Paseroptik core into the planar optical waveguide Light wave energy in this waveguide by influencing the sighting of the various port propagation paths is determined. 5. The method as claimed in claim 1, in which a field-phase-matching on the surface of the planar optical waveguide Diffraction grating is provided, characterized in that in the process step of deforming the Coupler part of the fiber optic core on the coupler part has a contact surface that is a negative of the wavy surface of the diffraction grating is attached and that this contact surface is in intimate contact with the substantially wavy surface of the diffraction grating is arranged. 6. The method according to claim 5, characterized in that that in the process step of deforming the coupler part of the Paseroptik core prior to deforming on the wavy surface of the diffraction grating is placed and that the material of the coupler part by applying heat and pressure is softened so that it flows into the grooves of the wavy surface of the diffraction grating. 709818/0665 7. The method according to claim 5, characterized in that in the process step of deforming the Coupler part of the fiber optic core is arranged in the immediate vicinity of the diffraction grating and that the coupler part a Cast compound is added, which flows into the grooves of the wavy surface of the diffraction grating before hardening and their Refractive index at least as high as the lower of the refractive indices of the fiber optic core and the planar optical Waveguide, but lower than the higher of the refractive indices of the fiber optic core and the planar optical Waveguide is. 8. Apparatus for optically coupling lightwave energy through phase-matched evanescent fields between a coupler part a multi-wave type fiber optic core and a planar one optical waveguide which is arranged with a part of its surface in the vicinity of the coupler part, thereby characterized in that the coupler portion of the fiber optic core (202; 302) has a predetermined spatula shape due to which the light wave energy traveling in the fiber optic core is coupled into the planar optical waveguide can be. 9. Apparatus according to claim 8, characterized in that the fiber optic core with the exception its coupler part has a cylindrical shape. 10. A device with a planar optical waveguide on the surface of which a diffraction grating is attached, and a fiber optic core that connects a phase-matched evanescent fields optically to the planar optical waveguide whose diffraction grating has coupled coupler part, characterized in that the coupler H. of the fiber optic core (400; 600) has a contact surface which is essentially a negative of the wavy surface of the 709818/0 665 Diffraction grating (404; 604); and that the contact surface of the coupler part is arranged so that it substantially fills the grooves of the wavy surface of the diffraction grating. 11. The apparatus of claim 10, wherein the fiber optic core is a multi-wave type waveguide, d u r ch characterized in that the coupler part of the fiber optic core in one to the planar optical waveguide in the substantially perpendicular direction and flattened in a substantially parallel to the planar optical waveguide Direction is expanded in a fan shape such that the coupler part has a spatula shape which is a multi-wave type coupling between the Easeroptik core and the planar optical waveguide. 709818/0665