Optical fiber devices and methods for providing the same

Abstract

An optical waveguide device comprises an optical circuit and a first optical waveguide connected to the optical circuit, as well as a second optical waveguide arranged with the first optical waveguide in a coupling section for evanescent wave coupling. The second optical waveguide is fixed relative to the first optical waveguide in the coupling section by a fixing material, and the fixing material has a refractive index that is lower than a refractive index of the first optical waveguide and the second optical waveguide.

Description

[0001] The present invention relates to optical fiber devices and methods for providing the same. In particular, the present invention relates to long-term stable and passivated ultra-low-loss fiber-to-chip couplings via adiabatic energy exchange.

[0002] Information can be transmitted using optical signals in optical fibers. For example, such optical fibers can be used to send optical signals to or receive signals from an optical circuit. Such optical transmission paths may require a connection between optical fibers to transfer light from a first waveguide to a second waveguide, or vice versa. Such connections or coupling points should be as low-loss as possible.

[0003] Optical fiber devices for coupling optical fibers with low optical losses would therefore be desirable.

[0004] An object of the present invention is therefore to propose optical waveguide devices and methods for providing the same which enable coupling between optical waveguides, preferably permanently, with a low degree of optical losses.

[0005] This problem is solved by the subject matter of the independent patent claims.

[0006] A core idea of ​​the present invention is to have recognized that the object according to the invention can be achieved on the one hand by arranging two optical waveguides to form an evanescent coupling, and by fixing one waveguide relative to the other waveguide by a fixing material whose refractive index is lower than a refractive index of the two waveguides provided for the evanescent coupling.

[0007] A further core idea of ​​the present invention is that the quality of the coupling between the waveguides arranged for evanescent wave coupling can be particularly high in that, on the one hand, a waveguide has a tapered shape and, in addition, a recess in a substrate is adapted to the tapered shape in such a way that, despite the tapered shape, a course of the optical axes of the waveguides parallel to one another is maintained, for example in that the recess has a variable width and / or variable depth.

[0008] According to one embodiment, an optical waveguide device comprises an optical circuit and a first optical waveguide connected to the optical circuit. The optical waveguide device comprises a second waveguide arranged with the first optical waveguide for evanescent wave coupling in a coupling section. The second optical waveguide is fixed relative to the first optical waveguide in the coupling section by a fixing material, and the fixing material has a refractive index that is lower than a refractive index of the first optical waveguide and the second optical waveguide. This enables particularly advantageous adiabatic coupling between the waveguides.

[0009] According to a further aspect of the embodiments described herein, an optical waveguide device comprises an optical circuit and a first optical waveguide connected to the optical circuit. Furthermore, a second optical waveguide is provided, arranged with the first optical waveguide for evanescent wave coupling in a coupling section. The second optical waveguide comprises an optical fiber arranged on a substrate and having a tapered shape in the coupling section. The substrate has a recess with a geometry adapted to the tapered shape.The recess is configured to receive the second optical waveguide and is designed to keep the course of a second optical axis of the second optical waveguide parallel to a course of a first optical axis of the first optical waveguide in the coupling section, which also enables efficient wave coupling.

[0010] The two aspects can be easily combined to further increase the efficiency of the wave coupling.

[0011] Further embodiments provide methods for providing such optical waveguide devices. Further advantageous embodiments of the present invention are the subject of dependent patent claims.

[0012] Particularly preferred embodiments of the present invention are explained below with reference to the accompanying drawings. Fig. 1 is a schematic block diagram of an optical fiber device according to an embodiment; Fig. 2a is a schematic cross-sectional view of an optical waveguide device according to an embodiment in which an optical waveguide is embedded in a substrate and arranged next to another optical waveguide; Fig. 2b is a schematic cross-sectional view of an optical waveguide device according to an embodiment, in which the optical waveguide is arranged on a surface of the substrate; Fig. 2c is a schematic cross-sectional view of an optical waveguide device according to an embodiment, in which the optical waveguide is arranged opposite the optical waveguide device from Fig. 2a is arranged with a changed position relative to the other optical fiber; Fig. 3a is a schematic plan view of an optical waveguide device according to an embodiment in which the optical waveguide has a tapered section; Fig. 3b-c schematic representations of cutting planes of the Fig. 3a; Fig. 4 is a schematic side sectional view of at least part of an optical waveguide device according to an embodiment with mutually inclined optical axes of the waveguides; Fig. 5 is a schematic side sectional view of an optical waveguide device according to an embodiment in which an optical waveguide has an optical interference structure; Fig. 6 is a schematic cross-sectional view of at least part of an optical waveguide device according to an embodiment in which, unlike in the optical waveguide devices of Fig. 2a-c an arrangement of the optical waveguides is made in direct contact; Fig. 7 is a schematic plan view of at least part of an optical waveguide device according to an embodiment in which more than one pair of optical waveguides is aligned with each other; Fig. 8 is a schematic flow diagram of a method according to an embodiment that can be used, for example, to provide an optical waveguide device according to the first aspect; and Fig. 9 is a schematic flow diagram of a method according to an embodiment that can be used, for example, to provide an optical fiber device according to the second aspect.

[0013] Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally equivalent or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.

[0014] The embodiments described below are described in conjunction with numerous details. However, embodiments may also be implemented without these detailed features. Furthermore, for clarity, embodiments are described using block diagrams instead of detailed illustrations. Furthermore, details and / or features of individual embodiments may be readily combined with one another, unless explicitly described otherwise.

[0015] The following exemplary embodiments relate to the arrangement of optical waveguides for evanescent wave coupling. In evanescent wave coupling, waves emerge from a waveguide, regardless of whether it is surrounded by another material, fluid, or vacuum, and penetrate another adjacent waveguide for further propagation. Thus, atmospheres other than air, such as protective gases or the like, can also be arranged.

[0016] Embodiments described herein relate to optical waveguide devices with an optical circuit. An optical circuit can refer to an optical testing device, such as a lab-on-chip, that performs measurements using optical signals, although embodiments are not limited thereto. Other types of optical transmission are, for example, in the field of quantum computers or optical computers or the transmission of light signals, such as in the field of on-chip single-photon sources. Such optical circuits can be permanently connected to an optical waveguide and, for example, coupled to another optical waveguide for mounting the optical circuit in different systems or devices.

[0017] For optical coupling, so-called grating couplers are known to those skilled in the art. These couplers utilize an integrated grating to achieve coupling within the waveguides. Besides the advantages of comparatively simple alignment and the freedom to choose the coupling position, this method yields comparatively poor coupling efficiencies and is wavelength- and polarization-dependent. Known designs and potentially achievable performance levels are described, for example, in [1].

[0018] Furthermore, so-called edge couplers are known to those skilled in the art. These couplers connect the components directly from the fiber to the waveguide, starting from the side of the chip. Even though high efficiencies can be achieved, the alignment of both structures requires very fine tolerances and is limited to the edge of the chip. Various designs of these are described in [2].

[0019] Embodiments are based on the concept of evanescent couplers, in which light is transmitted into the other waveguide via an adiabatically tapered fiber. Changing the cross-section results in the eigenmodes of both waveguides overlapping, allowing transmission with very high coupling efficiency. A continuous change in the cross-section used in exemplary embodiments ensures comparatively relaxed positioning accuracies. By using a fixing material with a refractive index lower than the refractive indices of the two optical waveguides, as described herein, permanent attachment or maintenance of the optical efficiencies can be achieved, thus also addressing the existing problem of long-term, high-quality optical transmission.

[0020] It is particularly preferred if the fixing material has a refractive index greater than 1.

[0021] Embodiments solve the problem of coupling light from fibers into integrated chip waveguides. This results in further challenges, since, for example, low-loss coupling of both components is not trivial to implement due to differences in mode shape and mode size. In addition, it may be necessary to achieve long-term stability of the system with suitable mounting of both geometries. One difficulty here is finding a mounting method that has no or occasionally only a minor negative impact on coupling efficiency, even during continuous use. The alignment of the coupling structures to each other can also involve tight tolerances.

[0022] Fig. Figure 1 shows a schematic block diagram of an optical waveguide device 10 according to one embodiment. The optical waveguide device 10 comprises an optical circuit 12, such as an optical chip or the like. An optical waveguide 14 is connected to the optical circuit and is configured to transport an optical signal away from the optical circuit 12 and / or to transport an optical signal to the optical circuit 12.

[0023] A further optical waveguide 16 is arranged in a coupling section 22 for evanescent wave coupling 18, so that in the coupling section 22, optical signals can be coupled from the optical waveguide 14 to the optical waveguide 16 and / or from the optical waveguide 16 to the optical waveguide 14. The coupling section 22 can be influenced by the mode formation in the waveguides 14 and / or 16. Even if the waveguide 14 and the waveguide 16 are illustrated as rectangular by way of example, at least one of the waveguides can, for example, have a tapered or widening shape, such as a tapered shape, which can be particularly advantageous if one of the waveguides 14 and / or 16 is designed as an optical fiber.

[0024] An exemplary substrate material is SiO2, which has a refractive index of approximately 1.44. In one exemplary embodiment, the refractive index of the second optical waveguide can have a similar value, for example, with a deviation of at most 20%, at most 10%, or at most 5%. Embodiments are based at least in part on considering a possible condition that the second optical waveguide (fiber) has a higher or the same, but not lower, refractive index than the substrate. In one possible configuration, the substrate has refractive index values ​​in a range from air (n=1) to, for example, germanium as a semiconductor (n approximately 4), which allows a corresponding bandwidth of the refractive index.The above-mentioned condition means that the implementation of the first optical waveguide and / or the second optical waveguide with the mentioned tolerances may also deviate from the mentioned values.

[0025] The first optical waveguide, in contrast, can have higher refractive indices. If the first optical waveguide, for example, comprises or consists of a silicon material or Si, the refractive index is approximately 3.48. If, for example, lithium niobate is used, the refractive index is 2.21. It is preferred if the refractive index of the substrate material is lower than the refractive index of the material of the first optical waveguide and if the refractive index of the fiber, if assumed to be an SMF28 fiber, for example, is greater than or equal to that of the substrate. In some embodiments, a fiber-to-chip coupling is implemented, where the fiber can have a lower refractive index than the waveguide. Second optical waveguides comprising quartz material, in contrast, can have a lower refractive index.

[0026] The optical waveguide 16 is fixed relative to the optical waveguide 14 in the coupling section 22 by a fixing material 24. The fixing material 24 has a refractive index that is lower than a refractive index of the optical waveguide 14 and a refractive index of the optical waveguide 16. In other words, the fixing material 24 can have a lowest refractive index that exists along an optical transmission path between the waveguides 14 and 16. This can also be expressed as: nFixation <nWellenleiter1,nWellenleiter2 where n denotes the refractive index and the refractive indices of the waveguide 1, ie, the waveguide 14, and the waveguide 2, ie, the waveguide 16, may be the same or different from each other, in which case nWaveguide1 <nWellenleiter2 or nWaveguide1>nWaveguide2 According to one embodiment, the refractive index of the fixing material 24 is smaller than a refractive index of a substrate 26 on or in which the waveguide 14 can be arranged.

[0027] In some embodiments of the present invention, additional material may be arranged between the optical waveguides 14 and 16, such as substrate material for carrying or supporting one or both of the waveguides. In such an embodiment, the fixation material 24 preferably has a refractive index that is also lower than this additional material. The fixation material 24 may, for example, comprise a polymer, but may also comprise hybrid polymers and / or insulating materials, such as SiO2 or the like. In embodiments, the fixation material of the waveguide device thus comprises a cured polymer or polymer material.

[0028] The fixing material 24 makes it possible, on the one hand, to impair the high quality of the optical coupling between the waveguides 14 and 16 only insignificantly, while, at the same time, maintaining this quality for the long term by fixing at least the waveguide 16. In some embodiments of the present invention, the fixing material is also arranged in a region of the optical waveguide 14 and, for example, covers both the optical waveguide 14 and the optical waveguide 16.

[0029] Fig. 2a shows a schematic cross-sectional view of an optical waveguide device 201 according to an embodiment. The optical waveguide 14 is, for example, embedded in a substrate 26. The substrate 26 comprises, for example, a semiconductor-based material, a dielectric material, or the like. The substrate 26 preferably comprises an insulator material, in particular a silicon oxide material. For example, silicon oxide (SiO2), sapphire or sapphire glass, silicon nitride (SiN / Si3N4), or the like can be used, although the use of silicon nitride can be difficult to implement. For example, air or ambient fluid can also be used as the substrate, or the arrangement of a solid can be omitted in order to obtain a freely suspended waveguide.

[0030] The substrate 26 may have an optional recess 28, which may, on the one hand, make it possible to simplify the alignment or orientation of the waveguide 16, as well as to enable the positioning of the waveguide 16. Nevertheless, the arrangement of the waveguide 16 may also be independent of the recess 28. In the embodiment of the optical waveguide device 201, the optical waveguide 16 may comprise an optical fiber. This may be attached to the substrate 26 by the fixing material 24. The recess 28 may, for example, be V-shaped, as shown in Fig. 2a. The fixing material 24 makes it possible to fix the optical waveguide 16 directly to the substrate 26. In alternative embodiments, the optical waveguide 16 can also be fixed at a defined distance from the substrate 26. For example, a positioning device could be used to align and hold the optical waveguide 16 until the fixing material 24 has hardened and can assume the permanent positioning of the optical waveguide 16. In an embodiment that can be implemented alternatively or additionally, the optical waveguide 16 can also be applied and placed directly onto the optical waveguide 14, for example, if the latter is at most incompletely surrounded by the substrate material 26 or if the substrate material is completely or partially absent in the coupling region.In some embodiments, alternatively or additionally, it is provided that a viscosity of the fixing material 24 before curing is used to adjust a distance between the optical waveguides 14 and 16.

[0031] The recess 28, also referred to as local etching geometry, can penetrate the substrate 26 completely or partially. In preferred embodiments, a depth of the recess 28 is less than a thickness 32 of the substrate 26.

[0032] Fig. Figure 2b shows a schematic cross-sectional view of an optical waveguide device 202 according to an embodiment. In this embodiment, the optical waveguide 14 is arranged on a surface 34 of the substrate 24, specifically on the same side as the optical waveguide 16. Fig. 2b with the Fig. 2a, it can be seen that in the optical waveguide device 201 not only the fixing material 24 is arranged between the optical waveguides 14 and 16, but also material of the substrate 26.

[0033] While this is possible in the optical waveguide device 202, it is not necessary, so that there may only be the fixing material 24 arranged between the optical waveguides 14 and 16. In both embodiments of the optical waveguide devices 201 and 202, the fixing material 24 has the lowest refractive index from the group consisting of the optical waveguide 14, the optical waveguide 16, the fixing material 24, and possibly the substrate 26.

[0034] While in the optical waveguide device 201 the fixing material 24 only covers the optical waveguide 16, in the optical waveguide device 202 it can cover both the optical waveguide 16 and the optical waveguide 14.

[0035] In the optical waveguide device 201, the fixing material 24 can at least fix the optical waveguide 16 to the substrate 26. In the optical waveguide device 202, the optical waveguide 14 can also be fixed to the substrate 26 by means of the fixing material 24. Alternatively or additionally, the optical waveguide 14 can be fixed to the substrate 26 entirely or partially by manufacturing processes, such as growth, etching, or the like.

[0036] It should be noted that the arrangement of the substrate for an optical waveguide device described herein is optional. For example, at least in the coupling region where the evanescent coupling occurs, the substrate material 26 could also be removed or absent, and the coupling region 22 could be arranged at least partially freestanding or suspended in midair.

[0037] Fig. 2c shows a schematic cross-sectional view of an optical waveguide device 203 according to an embodiment, in which the optical waveguide 14 is arranged with a changed position relative to the optical waveguide device 201 with respect to the optical waveguide 16.

[0038] The recess 28 can run parallel to the waveguide 14 at least in the coupling region and allow optical axes 361 of the optical waveguide 14 and 361 of the optical waveguide 16 to run parallel to one another. In the optical waveguide device 203, the optical axes 361 and 362 are offset from one another, for example, along a depth direction z, while in the optical waveguide device 201 they can be arranged offset along a y-direction perpendicular to the z-direction. An orthogonal offset is not absolutely necessary; a constant distance between the optical axes 361 and 362 in the coupling region can be sufficient, which can also be achieved by an arrangement according to the Fig. 2b can be obtained.

[0039] Fig. 3a shows a schematic top view of an optical waveguide device 30 according to an embodiment. The optical waveguide 16 can have a tapered section 38, in which the optical waveguide 16 has a tapered shape. This can be understood as axially tapering towards the optical circuit 12 or, conversely, as axially thickening away from the optical circuit. The modified cross-section can support wave coupling, wherein the modified diameter of the optical waveguide 16 can be challenging with regard to the positioning accuracy of the optical axes 361 and 362. This is solved in embodiments in that the recess 28 has a geometry adapted to the tapered shape and the recess 28 is configured and designed to accommodate the optical waveguide 16 in order to keep the course of the optical axis 362 parallel to a course of the optical axis 361 in the coupling section 22.The . Fig. 3a is to be understood schematically, inter alia, in the sense that in some embodiments a taper length of the second optical waveguide 16 can be longer or much longer than shown and can already begin before the coupling region 22 in order to achieve a remaining thickness at which coupling occurs with sufficient tapering.

[0040] This embodiment is based on the Fig. 3b in a section plane AA' and in Fig. 3c is explained in more detail using a section plane BB'. In the section plane AA', the recess 28, if used, can have a comparatively large dimension along the y-direction and / or z-direction in order to adjust a distance between the optical axes 361 and 362.

[0041] As it is in Fig. 3c, with a decreasing cross-section of the optical waveguide 16, comparatively less material can be arranged around the optical axis 362 due to the taper, which can be compensated for by a reduced dimension of the recess 28 along the y-direction and / or along the z-direction. The change in the dimension of the recess 28 can be adapted to the shape in the tapered section 38 and, for example, can be just as linear as the taper / widening of the cross-section of the optical waveguide 16. This makes it possible to keep the optical axes, designated, for example, by the geometric center of the cross-section of the two optical waveguides, parallel to one another and at a constant distance 42, even if it can be complex to implement a variable depth and / or width of the recess 28 along the axial extents, for example by performing an etching process.

[0042] In other words, the Fig. 2a-c, Fig. 3b and Fig. 3c Cross sections of the fiber-to-chip coupling orthogonal to an optical axis. The fiber 16, which is secured, for example, with a polymer-based fastening material, is aligned with the integrated waveguide 14. The waveguide is located in a cladding material 26, which has a local etched geometry 28 for positioning the fiber and has a thickness of 32. Fig. 2a-c show different possible arrangements of the coupling structures and in the Fig. 3b and Fig. 3c shows two positions along the optical axis, approximately matching the optical waveguide device 202. This illustrates the possibility of using a continuously decreasing adjustment 28, so that the optical axes of the tapered fiber and the waveguide always lie in the same plane. This groove, which varies in the propagation direction, can be used for various embodiments of the invention described herein.

[0043] Fig. 4 shows a schematic side sectional view of at least part of an optical waveguide device 40 according to an embodiment. The optical circuit, for example, is not shown. It shows a tapered shape of the optical waveguide 16 with an approximately constant distance 44 between the waveguide 16 on the one hand and the substrate material 26 on the other hand, which can be used, for example, as a cladding material or housing material for the optical circuit 12 and on or in which the waveguide 14 is arranged.

[0044] The optical axis 362 may be inclined, deviating from a parallel course to the optical axis 361, as shown in Fig. 4. An inclination angle can be adapted to a taper angle in order to enable the most constant value of the distance 44 over the axial course.

[0045] The fastening material 24 can be arranged both in the coupling region 22 and outside the coupling region 22, for example in a strain relief region 46. There, an additional fastening of the optical waveguide 16 can be obtained, even if no optical properties are required here. In other words, Fig. Figure 4 shows a view of the fiber-to-chip coupling along the optical axis. It shows the coupling region 22, where the energy transfer takes place, as well as the bonding of the strain relief 46 using the polymer or fixation material 24. The fiber 16 is thus attached to the cladding material 26 of the chip, enabling and possibly even guaranteeing adiabatic coupling to the waveguide 14 and / or from the waveguide 14 to the optical waveguide 16.

[0046] At a tapered end, the optical waveguide 16 can have a diameter or minimum diameter 48 of at least 500 nm, at least 700 nm, or at least 1 µm, preferably greater than 1 µm, since such dimensions are easier to handle and the optical quality of the coupling can still be maintained with the present embodiments. The taper can be as shown in the Fig. 3a-c shown symmetrically with respect to the optical axis.

[0047] Fig. 5 shows a schematic side sectional view of an optical waveguide device 50 according to an exemplary embodiment. In this embodiment, the optical waveguide 14 is configured such that, at least within the coupling section 22, but not necessarily limited thereto, it has an optical interference structure 52 for coupling optical radiation out of the waveguide 14' or into the waveguide 14'. The optical interference structure 52 can, for example, comprise a grating structure, such as a surface grating or a Bragg grating. The interference structure 52 can, in particular in an embodiment with an optical grating, be configured such that a periodic or aperiodic optical interference is generated in the optical waveguide 14'.For example, distances 54 between adjacent perturbation elements 561 and 562 along a course of the optical waveguide 14' can be constant, linearly variable, non-linearly variable and thus periodic or non-periodic.

[0048] Based on the Fig. Figures 1 to 5 explain advantageous configurations for fixing two waveguides relative to each other and achieving high optical efficiency. However, embodiments of the present invention are not limited to this, but also allow for an arrangement of more than one waveguide pair.

[0049] Fig. 6 shows a schematic cross-sectional view of at least part of an optical waveguide device 60 according to an embodiment in which, unlike in the optical waveguide devices 201, 202, 203 and 30, the optical waveguide 16 is arranged in direct contact with the optical waveguide 14, for example by placing the optical waveguide 16 on the optical waveguide 14 and then fixing it with the fixing material 24.

[0050] Fig. 7 shows a schematic plan view of at least a part of an optical waveguide device 70 in which more than one optical waveguide pair is aligned with each other, for example six optical waveguide pairs, wherein any other number of at least one, at least two, at least three, at least four, at least five, at least seven or more, such as at least ten or at least 20 optical waveguide pairs is possible. Fig. 7 shows several advantageous embodiments that can be used independently of one another but in particular also in combination.

[0051] The respective coupling locations are, for example, in accordance with the Fig. 6. As shown in the schematic plan view, both the optical waveguides 161 to 166 and 141 to 146 of a respective pair of optical waveguides can have a tapered shape, which lie opposite each other in the respective coupling region 221 to 226. The fixing material 24 can be arranged in the coupling region 221 to 226 and locally also outside thereof.

[0052] In the top view shown, optical axes 36 1,j and 36 2,jwith j = 1,..., 6, or the number of pairs of optical waveguides, run parallel to each other, approximately in the viewing plane shown. This means that, in addition to using multiple pairs, a tapered form of only the optical waveguide 14 of a pair, only the optical waveguide 16 of a pair, or both waveguides 14 and 16 can be used.

[0053] In Fig. 7, the optical waveguide 141 may be one of a group of optical waveguides 141 to 146 connected to the optical circuit. The optical waveguide 16 may be one of a second group of optical waveguides 161 to 166. An optical waveguide of the second group may be arranged for evanescent wave coupling with an associated optical waveguide of the first group. While in the Fig. 7 shows a 1:1 assignment between waveguides 14 and 16, embodiments also allow for a multiple assignment, wherein a 1:2 arrangement or a 2:1 arrangement is particularly advantageous, i.e., an optical waveguide 14 couples to two optical waveguides 161 and 162 or an optical waveguide 16 couples to two optical waveguides 141 and 142. If, for example, the optical waveguide device 30 is considered, an optical waveguide 14 could be arranged on both sides of the optical waveguide 16 or optical waveguides 16 could be arranged on both sides of the optical waveguide 14. If, in addition, the arrangement according to the Fig. 6, a 1:3 assignment and / or a 3:1 assignment could also be easily implemented. While in the optical fiber device 60, each coupling point can function independently of another coupling point, in a multiple arrangement, a dependency can be maintained and possibly utilized, for example, for signal splitting or a multiplexing process.

[0054] According to such an embodiment, the optical waveguide 14 may be one of a group 141 to 14 j of optical waveguides, wherein the optical waveguide 16 is arranged with at least two of the optical waveguides 14 for evanescent wave coupling. Alternatively, the optical waveguide 16 may be one of a group of optical waveguides 161 to 16 j wherein the optical waveguide 14 is connected to at least two of the optical waveguides 161 to 16 jfrom the second group of optical waveguides for evanescent wave coupling is arranged and fixed.

[0055] With reference to the Fig. 3a-c, embodiments enable, independently of the use of the fixing material, but particularly in combination therewith, to provide an optical waveguide device comprising an optical circuit and a first optical waveguide connected to the optical circuit, such as the optical waveguide 14. Furthermore, a second optical waveguide is provided, arranged in a coupling section with the first optical waveguide for evanescent wave coupling. The second optical waveguide comprises an optical fiber, wherein the optical fiber is arranged on a substrate and has a tapered shape in the coupling section. The substrate has a recess with a geometry adapted to the tapered shape.Furthermore, the recess for receiving the second optical waveguide is configured and designed to maintain the course of a second optical axis of the second optical waveguide in the coupling section parallel to a course of the first optical axis of the first optical waveguide. In one possible embodiment, for example, the waveguide device 30 could be formed without the fixing material 24. Based on the described embodiment, however, the second optical waveguide can also be fixed relative to the first optical waveguide in the coupling section by means of a fixing material, wherein the fixing material has a refractive index that is lower than a refractive index of the first and second optical waveguides.

[0056] Fig. 8 shows a schematic flow diagram of a method 800 according to an embodiment, which can be used, for example, to provide an optical waveguide device according to the first aspect, i.e., using the fixing material. A step 810 comprises providing an arrangement with an optical circuit and with a first optical waveguide connected to the optical circuit. A step 820 comprises arranging a second optical waveguide with respect to the first optical waveguide for evanescent wave coupling with the first optical waveguide in a coupling section of the second optical waveguide.A step 830 includes fixing the second optical waveguide relative to the first optical waveguide in the coupling section with a fixing material having a refractive index lower than a refractive index of the first optical waveguide and the second optical waveguide.

[0057] In an advantageous embodiment of method 800, the arrangement of the second optical waveguide is carried out such that an adjustment is carried out to find a relative position between the first optical waveguide and the second optical waveguide, in which the evanescent coupling occurs with a quality that corresponds at least to a threshold value. This can be done, for example, by laterally displacing at least one of the waveguides. If a quality of the coupling is measured simultaneously, it can be determined at what point in time the threshold value is reached or exceeded. The method can then comprise a step in which the fixing comprises curing the fixing material as a polymer material at the found relative position. This makes it possible to apply the fixing material before or after the suitable position has been found.Curing may, for example, comprise irradiation with a suitable wavelength, such as UV radiation or the like, to cure the polymer.

[0058] Fig. 9 shows a schematic flow diagram of a method 900 according to an embodiment, which can be used, for example, for providing an optical waveguide device according to the second aspect, that is, for applying the variable groove adapted to the taper shape.

[0059] A step 910 comprises providing an arrangement with an optical circuit and a first optical waveguide connected to the optical circuit. A step 920 comprises arranging a second optical waveguide comprising an optical fiber that has a tapered shape in a coupling section, i.e., axially tapered or widened, and is arranged with respect to the first optical waveguide for evanescent wave coupling with the first optical waveguide in the coupling section.

[0060] The method is carried out such that the optical fiber is arranged on a substrate having a recess with a geometry adapted to the tapered shape. Furthermore, the method is carried out such that the recess is configured to receive the second optical waveguide and is designed to keep the course of a second optical axis of the second optical waveguide parallel to a course of a first optical axis of the first optical waveguide in the coupling section.

[0061] The embodiments described herein provide approaches that can fall into the group of evanescent couplers and are thus capable of achieving comparatively high coupling efficiencies. The approaches described herein can be implemented according to the described embodiments, but are not limited thereto. Within the scope of the embodiments, the optical waveguide 16, for example formed as a fiber, can be adjustably inserted and aligned with the waveguide using a specially etched groove, as described in the Fig. 2a-c. Once a maximum in coupling efficiency is reached, the structure can be secured with a polymer, as described in connection with method 800.

[0062] Optical waveguide devices described herein may have an optical interface (not shown) for coupling to a light source to provide for transmission of an optical signal between the light source and the optical circuit of the optical waveguide device. This means that the optical light source may be implemented outside the optical waveguide device and coupled to the optical circuit via the optical interface. Alternatively or additionally, a light device described herein may be equipped with an optical interface (not shown) for coupling to an optical detector to provide for transmission of an optical signal between the optical detector and the optical circuit, for example, from the optical circuit to the optical detector.

[0063] Possible implementation variants of the embodiments described herein include various arrangements from the fiber to the waveguide, as described, for example, in the Fig. 2a-c or Fig. 6. The fiber can be tapered linearly or non-linearly, and the waveguide can also be formed in various shapes, such as tapered, non-tapered, or split. In order to align fibers with the waveguide in their optical axes, or to be at the same height and, in particular, to run parallel to each other, the groove can be continuously reduced in the propagation direction, as described in connection with the Fig. 3a-c is described.

[0064] The embodiments described herein offer, among other things, the following advantages or solve the following tasks: - Due to the higher refractive index of the polymer compared to the environment, especially the air environment, the fiber taper can be tapered less to ensure adiabatic conditions. The angles can be determined at least partially by the coupling length and the diameters, for example, provided that the condition that the angle maintains an adiabatic transition is met, whereby the exact values ​​can depend on the configuration. Examples allow for large diameters of more than 500 nm, more than 700 nm, or even more than 1 µm. - The etched adjustment geometry of the recess 28, for example, as a V-shaped groove, enables a reduction in the degrees of freedom and thus the adjustment effort. For example, six degrees of freedom can be reduced to two, so that the coupling length and rotation remain as degrees of freedom, which is advantageous. - By using a fixation material, such as a polymer, not only long-term stabilization of the structure but also passivation of the coupling point can be achieved. This protects the critical areas from dirt and aging effects, and thus from stray light from the coupling structures. - The connection of the structures with the approach shown enables a permanent and stable bonding of the components and at the same time ensures strain relief of the fiber-chip structure.

[0065] Compared to known designs, embodiments allow for reduced adjustment effort, high robustness against external influences, long-term stability and tapered fiber tips of more than 1 µm.

[0066] This does not exclude combinations with other measures, such as operation in a protective atmosphere or an inorganic coating.

[0067] Optical waveguide devices described herein may have a fiber taper of more than 1 µm. Optionally, they may be fully sealed with a transparent polymer with a refractive index lower than the refractive index n of SiO2. Locally etched structures for aligning the coupling components may also be included.

[0068] Embodiments described herein can be used in different areas of fiber-to-chip coupling, such as an on-chip single photon source and / or quantum computers or optical computers.

[0069] Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or component of a device can also be understood as a corresponding method step or as a feature of a method step. Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device.

[0070] The above-described embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented in the description and explanation of the embodiments herein. Sources [1] Marchetti, Riccardo & Lacava, Cosimo & Carroll, Lee & Gradkowski, Kamil & Minzioni, Paolo. (2019). Coupling strategies for silicon photonics integrated chips [Invited]. Photonics Research. 7. 10.1364 / PRJ.7.000201. [2] Son, Gyeongho & Han, Seungjun & Park, Jongwoo & Kwon, Kyungmook & Yu, Kyoungsik. (2018). High-efficiency broadband light coupling between optical fibers and photonic integrated circuits. Nanophotonics. 7. 10.1515 / nanoph-2018-0075. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] Marchetti, Riccardo & Lacava, Cosimo & Carroll, Lee & Gradkowski, Kamil & Minzioni, Paolo. (2019). Coupling strategies for silicon photonics integrated chips [Invited]. Photonics Research. 7. 10.1364 / PRJ.7.000201

[0070] Son, Gyeongho & Han, Seungjun & Park, Jongwoo & Kwon, Kyungmook & Yu, Kyoungsik. (2018). High-efficiency broadband light coupling between optical fibers and photonic integrated circuits. Nanophotonics. 7. 10.1515 / nanoph-2018-0075

[0070]

Claims

[1] Optical fiber device with: an optical circuit (12); a first optical waveguide (14) connected to the optical circuit (12); a second optical waveguide (16) arranged with the first optical waveguide (14) for evanescent wave coupling (18) in a coupling section (22); wherein the second optical waveguide (16) is fixed relative to the first optical waveguide (14) in the coupling section (22) by a fixing material (24); and the fixing material (24) has a refractive index that is lower than a refractive index of the first optical waveguide (14) and the second optical waveguide (16). [2] The optical waveguide device according to claim 1, wherein the first optical waveguide (14) is disposed on or in a substrate (26); and wherein the fixing material (24) fixes the second optical waveguide (16) to the substrate (26). [3] Optical waveguide device according to claim 2, wherein the substrate (26) comprises an insulating material, in particular a silicon oxide material. [4] An optical waveguide device according to any one of the preceding claims, wherein the second optical waveguide (16) comprises an optical fiber. [5] Optical waveguide device according to claim 4, wherein the optical fiber is fixed to a substrate (26) by the fixing material (24) and has a tapered shape in the coupling section (22); wherein the substrate (26) has a recess (28) with a geometry adapted to the tapered shape; wherein the recess (28) is designed to receive the second optical waveguide (16) and is designed to keep the course of a second optical axis (362) of the second optical waveguide (16) parallel to a course of a first optical axis (361) of the first optical waveguide (14) in the coupling section (22). [6] Optical fiber device according to claim 5, wherein the geometry of the recess (28) is V-shaped and formed with a variable depth. [7] Optical fiber device according to one of the preceding claims, wherein the fixing material (24) has a refractive index greater than 1. [8] Optical waveguide device according to one of the preceding claims, wherein the first optical waveguide (14) has an optical interference structure (52) within the coupling section (22) for coupling optical radiation from or into the first optical waveguide (14). [9] Optical waveguide device according to claim 8, wherein the optical perturbation structure (52) comprises an optical grating configured to generate a periodic or aperiodic optical perturbation in the first optical waveguide (14). [10] Optical waveguide device according to one of the preceding claims, wherein the second optical waveguide (16) comprises an optical fiber having a waveguiding section and the coupling section (22), the optical fiber having a smallest diameter (48) of at least 500 nm in the coupling section (22). [11] Optical fiber device according to one of the preceding claims, wherein the fixing material (24) comprises a cured polymer. [12] Optical waveguide device according to one of the preceding claims, wherein the refractive index of the fixing material (24) is smaller than a refractive index of a substrate (26) on or in which the first optical waveguide (14) is arranged. [13] Optical waveguide device according to one of the preceding claims, wherein the refractive index of the first optical waveguide (14) is greater than the refractive index of the second optical waveguide (16). [14] An optical waveguide device according to any preceding claim, comprising an optical interface for coupling to a light source; to provide transmission of an optical signal between the light source and the optical circuit (12). [15] An optical waveguide device according to any preceding claim, comprising an optical interface for coupling to an optical detector; to provide transmission of an optical signal between the optical detector and the optical circuit (12). [16] An optical waveguide device according to any one of the preceding claims, wherein the first optical waveguide (14) is one of a first group (141-146) of optical waveguides connected to the optical circuit (12); and wherein the second optical waveguide (16) is one of a second group (161-166) of optical waveguides; wherein an optical waveguide of the second group (161-166) is arranged and fixed for evanescent wave coupling (18) with an associated optical waveguide of the first group (141-146). [17] Optical fiber device according to one of the preceding claims, wherein the first optical waveguide (14) is one of a first group (141-146) of optical waveguides, wherein the second optical waveguide (16) is arranged and fixed with at least the first optical waveguide (14) and a further optical waveguide from the first group (141-146) of optical waveguides for evanescent wave coupling (18); or wherein the second optical waveguide (16) is one of a second group (161-166) of optical waveguides, wherein the first optical waveguide (14) is arranged and fixed with at least the second optical waveguide (16) and a further optical waveguide from the second group (161-166) of optical waveguides for evanescent wave coupling (18). [18] Optical fiber device comprising: an optical circuit (12); a first optical waveguide (14) connected to the optical circuit (12); a second optical waveguide (16) arranged with the first optical waveguide (14) for evanescent wave coupling (18) in a coupling section (22); wherein the second optical waveguide (16) comprises an optical fiber; wherein the optical fiber is arranged on a substrate (26) and has a tapered shape in the coupling section (22); wherein the substrate (26) has a recess (28) with a geometry adapted to the tapered shape; wherein the recess (28) is arranged to receive the second optical waveguide (16) and is designed to keep the course of a second optical axis of the second optical waveguide (16) parallel to a course of a first optical axis of the first optical waveguide (14) in the coupling section (22). [19] The optical waveguide device according to claim 18, wherein the second optical waveguide (16) is fixed relative to the first optical waveguide (14) in the coupling portion (22) by a fixing material (24); and the fixing material (24) has a refractive index lower than a refractive index of the first optical waveguide (14) and the second optical waveguide (16). [20] A method (800) for providing an optical fiber device comprising the following steps: Providing (810) an arrangement comprising an optical circuit and a first optical waveguide connected to the optical circuit; Arranging (820) a second optical waveguide with respect to the first optical waveguide for evanescent wave coupling with the first optical waveguide in a coupling section of the second optical waveguide; and fixing (830) the second optical waveguide with respect to the first optical waveguide in the coupling section with a fixing material having a refractive index lower than a refractive index of the first optical waveguide and the second optical waveguide. [21] A method according to claim 20, wherein the arranging of the second optical waveguide comprises an adjustment for finding a relative position between the first optical waveguide and the second optical waveguide, in which the evanescent coupling occurs with a quality that corresponds at least to a threshold value; and wherein the fixing comprises curing the fixing material as a polymer material at the found relative position. [22] A method (900) for providing an optical fiber device comprising the following steps: Providing (910) an arrangement comprising an optical circuit and a first optical waveguide connected to the optical circuit; and Arranging (920) a second optical waveguide comprising an optical fiber having a tapered shape in a coupling section with respect to the first optical waveguide for evanescent wave coupling with the first optical waveguide in the coupling section; so that the optical fiber is arranged on a substrate having a recess with a geometry adapted to the tapered shape; so that the recess is arranged to receive the second optical waveguide and is designed to keep the course of a second optical axis of the second optical waveguide parallel to a course of a first optical axis of the first optical waveguide in the coupling section.

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