Optical coupling unit

Abstract

The invention relates to an optical coupling unit (1) for coupling a waveguide (2) to an external medium (3), the optical coupling unit comprising an optical coupler (4) and an optical conductor structure (5), wherein: the optical coupler (4) is optically arranged to transmit a light beam between the optical conductor structure (5) and the waveguide (2); the optical conductor structure (5) is optically connected to the external medium (3) for transmitting the light beam; the optical coupler (4) is designed to deflect the light beam out of the plane of the waveguide (2) and to couple it into an entry surface (6) of the optical conductor structure (5); the optical conductor structure (5) has an exit surface (7) arranged at a predetermined angle with respect to the entry surface (6), and so the light beam exits the exit surface (7) at an exit angle specified by the predetermined angle and can be coupled into the external medium (3); and the optical conductor structure has a structured plastics material. An optical coupling unit for improved optical coupling of a waveguide to an external medium is thus provided.

Description

[0001] Optical coupling unit

[0002] The invention relates to an optical coupling unit for coupling a waveguide to an external medium, comprising an optical coupler, wherein the optical coupler is configured to deflect the light beam out of the plane of the waveguide.

[0003] Integrated photonics utilizes the proven manufacturing techniques of the microelectronics industry to miniaturize optical devices and bring them down to chip size. Optical signals are guided through integrated waveguides and manipulated using integrated optical components, enabling applications in areas such as telecommunications, data communication, and sensor technology. Typically, light is coupled into and out of optical chips using fiber-to-chip couplers, such as grating couplers, which efficiently match the optical mode of an external medium, such as an optical fiber, to the optical mode of the waveguide.

[0004] Standard solutions for the fiber-to-chip coupling problem include edge couplers, which consist of tapered waveguides that adiabatically convert the fiber's fundamental mode into the waveguide's fundamental mode, and grating couplers, which consist of a periodically or quasi-periodically perturbed waveguide that deflects light out of the chip plane. While edge couplers must be positioned on chip facets, restricting optical access to the components on the chip, grating couplers can be placed anywhere on the chip, facilitating wafer-scale testing and prototyping. On low-refractive-index contrast platforms, chirped-period grating couplers are used to focus the beam to a specific point above the chip surface.Perfect vertical radiation can only be achieved by increasing the complexity of each radiated field, thereby adding new degrees of freedom for attenuating Bragg reflections.

[0005] Edge couplers must be positioned on the chip facets, which significantly limits the flexibility of the chip layout and the number of optical access channels, and requires facet polishing that is often incompatible with other nanofabrication requirements. Grating couplers improve access to on-chip devices, but are limited in terms of coupling efficiency and beam angle due to a limited number of design parameters, or require very complex chirped / focused multilayer geometries that are difficult to implement in practical devices, often leading to conflicting limitations in the fabrication process. Practical designs typically achieve only modest efficiencies, occurring exclusively at specific beam angles that differ from the desired surface normal, requiring the optical fiber to be polished or tilted accordingly.To develop highly efficient grating couplers, however, only a limited number of degrees of freedom can be controlled, primarily the period length or grating constant and the grating fill factor. This limitation restricts the range of achievable radiation angles (or transmission bandwidth), field profiles, and coupling efficiencies. Total internal reflection couplers (TIR couplers) improve coupling efficiency and bandwidth, but the latter decreases drastically when perfectly vertical radiation is desired. TIR couplers also suffer from optical reflections at the polymer-air interfaces, which reduce coupling efficiency and lead to unwanted interference signals that propagate through the photonic circuits.

[0006] Based on this, the object of the present invention is to provide an optical coupling unit for improved optical coupling of a waveguide to an external medium.

[0007] This problem is solved by the subject matter of the independent claim. Preferred embodiments of the invention are described in the dependent claims.

[0008] According to the invention, an optical coupling unit for coupling a waveguide to an external medium is provided, comprising an optical coupler and a light guide structure, wherein the optical coupler is optically arranged for transmitting a light beam between the light guide structure and the waveguide, the light guide structure is optically connected to the external medium for transmitting the light beam, the optical coupler is configured to deflect the light beam out of the plane of the waveguide and couple it into an entrance surface of the light guide structure, the light guide structure has an exit surface arranged at a predetermined angle relative to the entrance surface, so that the light beam exits the exit surface at an exit angle given by the predetermined angle and can be coupled into the external medium, and the light guide structure comprises a structured plastic.

[0009] With the optical coupling unit according to the invention, it is therefore possible to efficiently transmit a light beam between an optical waveguide and an external medium, such as an optical fiber. For this purpose, a mode profile of the waveguide, a waveguide mode, is coupled into the optical fiber structure by the optical coupler, which can then be coupled in as an optical fiber mode at an exit angle determined by the optical fiber structure.

[0010] The optical coupling unit according to the invention comprises an optical coupler and a light guide structure. The optical coupler serves to deflect the light beam out of the waveguide and couple it into the entrance surface of the light guide structure. In this case, the waveguide is mounted on a substrate as part of a chip. One plane of the chip coincides with the plane of the waveguide.

[0011] The optical fiber structure has an exit surface arranged at a predetermined angle to the entrance surface, so that the light beam emerges from the exit surface at an angle determined by this predetermined angle and can be coupled into the external medium. The optical fiber structure is thus designed to couple the light beam into the external medium at an angle determined by this predetermined angle. This allows the exit angle of the light beam to be adjusted to a specific position of the external medium by means of the predetermined angle. The entrance and exit surfaces are accordingly formed in the side faces of the optical fiber structure. The predetermined angle is therefore understood to be an angle that enables the light beam to exit at an angle corresponding to a specific position of the external medium.The angle is predetermined by the exit angle required to enable improved coupling of the light beam into the external medium. This facilitates positioning of the external medium, especially when the external medium is an optical fiber. This is because the optical fiber has an end face that is optically connected to the light guide structure to transmit the light beam and which typically has a predefined fiber entry angle. Due to its adaptability, the optical coupling unit can be designed for any external medium position and any fiber entry angle with a corresponding predetermined angle. Advantageously, this improves coupling efficiency and simplifies integration. Here, coupling efficiency refers to the signal strength of the light beam, i.e., its amplitude.Intensity refers to the amount of light transmitted from the waveguide to the external medium, relative to the signal strength of the light beam at an output of the waveguide.

[0012] Similarly, the optical fiber structure reduces the size of the emitted light beam by a factor of cos(θ). p - o) due to refraction at an interface between the exit surface and the environment, which is used to increase the overlap between the optical fiber mode and the emitted light beam in waveguide-chip arrays with low or medium index contrast. Likewise, the combination of the optical fiber structure and the optical coupler provides additional degrees of freedom in the design of the optical coupling unit, allowing for a reduction in the complexity of the optical coupler and / or the addition of additional functions.

[0013] A structured plastic is a material that has been specially shaped or structured at the microscopic or nanometer level to achieve specific physical, optical, or mechanical properties. Accordingly, the structured plastic is a nano- or microstructured plastic. This allows for precise shaping of the light guide structure, resulting in better control over the light beam and improved coupling efficiency. Likewise, it provides flexibility in the fabrication of the optical coupling unit, enabling the light guide structure to be specifically tailored to the respective application. The light guide structure is thus designed so that it exhibits the predetermined angle between the entry and exit surfaces.The flexibility provided by the structured plastic therefore consists in the fact that the respective optical coupling unit can be flexibly shaped depending on the position of the external medium or allows an exit angle corresponding to the position of the external medium.

[0014] The combination of an optical coupler with a structured plastic light guide structure offers a large number of degrees of freedom to achieve precise control over the light beam emitted by the optical coupler. This arrangement allows for customized adjustment of the exit angle and beam profile to improve coupling efficiency and bandwidth with an external medium without increasing the complexity of the optical coupler topology.

[0015] In principle, it is possible for the entrance surface of the optical fiber structure to be spaced apart from the optical coupler. However, according to a preferred embodiment of the invention, the entrance surface of the optical fiber structure is located directly adjacent to the optical coupler. The entrance surface can be understood as the part of the optical fiber structure, or the surface of the optical fiber structure, through which the light beam enters the optical fiber structure. The exit surface can be understood as the part of the optical fiber structure, or the surface of the optical fiber structure, through which the light beam exits the optical fiber structure. The reduced distance between the optical coupler and the optical fiber structure results in a lower beam divergence, which improves the efficiency of the light transmission.

[0016] In principle, the optical coupler can deflect the light beam out of the plane of the waveguide by various angles. However, according to a further preferred embodiment of the invention, the optical coupler is configured to deflect the light beam out of the plane of the waveguide by a coupler angle 0. p to deflect, the light guide structure the predetermined angle as well as a refractive index n p exhibits, and the exit angle 0 is given as follows:

[0017] if \0 + (j)\ > arcsin (7 / w p ).

[0018]

[0019] Will the condition be met?

[0020]

[0021] > arcsin (7 / w pIf this condition is met, the exit angle of the light beam from the exit surface can be precisely controlled. The exit angle depends on the predetermined angle and the refractive index of the material of the optical fiber structure.

[0022] In principle, various exit angles can be generated with the optical coupling unit. However, according to a preferred embodiment of the invention, the optical coupler is configured to deflect the light beam out of the plane of the waveguide by a coupler angle 0. p to deflect, and the light guide structure a predetermined angle as well as a refractive index n p exhibits a condition that is met as follows:

[0023] 0 p = ( / > -arcsin[sin(^) / w p ].

[0024] This makes it possible to couple the light beam perfectly perpendicular to the chip surface or the plane of the waveguide, i.e., parallel to a chip normal. This is particularly advantageous when the external medium is arranged perpendicular to the chip surface, which allows the light beam to be coupled in at 0° to the chip normal. This prevents the optical coupler from operating in the Bragg region, which would normally lead to undesirable second-order Bragg reflections, since the optical coupler alone cannot efficiently diffract light at 0° to the chip normal.

[0025] It is possible to use various optical couplers. However, according to a preferred embodiment of the invention, the optical coupler is a grating coupler. A grating coupler can be understood as an optical component that deflects light out of the plane of the waveguide or chip by diffraction. This improves the accessibility of on-chip components and facilitates testing and development of wafer-scale prototypes. In this context, according to a preferred embodiment of the invention, the grating coupler is apodized. Apodization is a technique in which the grating structure of the grating coupler is designed to distribute the intensity of the light beam more uniformly. This increases the coupling efficiency and improves the beam quality, i.e., the Gaussian shape of the light beam.

[0026] In principle, the optical fiber structure can be made of various materials. However, according to a preferred embodiment of the invention, the structured plastic is a structured polymer. Even more preferably, the optical fiber structure consists entirely of the structured polymer. A structured polymer is a polymer material that has been specially shaped or structured at the microscopic or nanometric level to achieve specific physical, optical, or mechanical properties. Accordingly, according to a preferred embodiment of the invention, the structured polymer is a nano- or microstructured polymer and can be produced by direct laser writing, two- or multi-photon polymerization, or nanoimprint lithography.This enables precise shaping of the light guide structure, leading to better control over the light beam guidance and improved coupling efficiency. According to a preferred embodiment of the invention, the structured polymer is SU-8, PMMA, IP, or IPX photoresin.

[0027] In principle, the exit surface can be flat. However, according to a preferred embodiment of the invention, a collimating lens is formed with the exit surface. A collimating lens is a lens that aligns light rays parallel to each other. This gives the optical fiber structure a focusing function that improves coupling efficiency. Such collimation of the light beam reduces alignment tolerances of the external medium relative to the waveguide, which facilitates fiber coupling using industrial methods. In this context, a particularly preferred embodiment of the invention provides for a convex exit surface. A convex surface is an outwardly curved surface. This improves the focusing of the light beam and increases coupling efficiency. A further preferred embodiment provides for an aspherical exit surface.In particular, this collimating lens can be flexibly formed within the structured plastic of the light guide structure. Depending on the distance and position of the external medium, the aforementioned manufacturing processes can be used to manipulate the structureable plastic in such a way that a light guide structure incorporating the structured plastic is produced, enabling the desired focusing and improved coupling efficiency.

[0028] It is possible to design the exit surface in various ways. However, according to a preferred embodiment of the invention, the exit surface is formed with a metamaterial, and the metamaterial has a periodic lattice structure. Metamaterials are artificially produced materials with specific optical properties determined by their structure. The metamaterial can be applied separately to the exit surface or formed directly within the exit surface using the methods described above, provided the optical fiber structure consists of such a structureable plastic. The exit surface accordingly has a certain thickness, which is determined by the thickness of the periodic lattice structure within the exit surface. A periodic lattice structure can be understood as a regularly arranged structure.This reduces reflection at the exit surface, which increases coupling efficiency. The metamaterial can also be flexibly formed directly at the exit surface using the aforementioned manufacturing processes.

[0029] In principle, the grating structure can be formed in various ways. However, according to a preferred embodiment of the invention, a grating constant of the grating structure is lower than a wavelength of the light beam, so that a subwavelength grating is formed in the exit surface. A subwavelength grating structure is characterized by spacings between elements of the grating structure that are smaller than the wavelength of the light. This creates an antireflection coating that reduces reflections at the interface between the optical fiber structure and the surrounding medium, usually air.

[0030] In principle, the elements can be designed in various ways. However, according to a further preferred embodiment of the invention, the grid structure comprises periodically arranged elements that are trapezoidal in cross-section along an edge of the exit surface. The exit surface has edges at the transition to other surfaces of the optical fiber structure. Particularly preferred in this context is that the elements are trapezoidal in cross-section along an edge that adjoins an edge between the entrance surface and the exit surface of the optical fiber structure. This structure behaves like a layer with a smooth refractive index variation in the direction perpendicular to the exit surface. This further improves the antireflection effect.Similarly, according to a further preferred embodiment of the invention, the lattice structure can have periodically arranged elements, and these periodically arranged elements are truncated pyramids formed two-dimensionally in the exit surface. A truncated pyramid is a pyramid shape with a flattened apex. This further optimizes the light beam guidance. The lattice structure can be designed in various ways. However, according to a preferred embodiment of the invention, the lattice structure is apodized.

[0031] According to a preferred embodiment of the invention, the exit surface comprises a non-reflective blaze grating, and the blaze grating is configured to transmit the light beam of a single predetermined diffraction order. This means that diffraction orders that are not transmitted are absorbed and not backscattered into the optical fiber structure, thereby improving the clarity and intensity of the light beam diffracted in the blaze grating. A blaze grating is a grating structure designed to direct light of a single predetermined diffraction order in a specific direction. This increases the efficiency of light transmission and provides spectral selectivity. Likewise, the light beam is focused towards the external medium.

[0032] It is possible to design the non-reflective blaze grating in various ways. However, according to a preferred embodiment of the invention, the non-reflective blaze grating is apodized to change the phase of the incoming beam and to cause the outgoing beam to radiate vertically and focus onto the fiber. This leads to improved coupling efficiency and allows for the adaptation of a spectral emission characteristic. Specifically, the apodization minimizes oscillations in the emitted spectrum.

[0033] In principle, the optical fiber structure can have various shapes. However, according to a preferred embodiment, the optical fiber structure is a prism, with the entrance surface adjacent to the exit surface, and the predetermined angle being a prism angle formed between the entrance and exit surfaces. The entrance surface is a side face of the prism corresponding to a leg (or catheti), and the exit surface is a side face of the prism corresponding to a hypotenuse. This allows the prism to be mounted on the optical coupler as efficiently and compactly as possible. In this context, "leg" and "hypotenuse" refer to the sides in the prism's cross-section that correspond to the respective side faces.

[0034] According to a particularly preferred embodiment of the invention, the prism is truncated at the exit surface at an angle opposite to the predetermined prism angle, thus reducing the size of the exit surface and forming a contact surface. A contact surface is an additional surface that enables a closer connection between the prism and the external medium. With the contact surface, the prism therefore has four lateral surfaces. The contact surface thus has an angle that allows the external medium to be positioned as close as possible to the exit surface. This significantly shortens the transmission path between the exit surface and the external medium, which in turn leads to a significantly reduced beam divergence. In principle, the contact surface can be formed at various angles relative to the inlet surface.However, according to a preferred embodiment of the invention, the contact surface is designed to be parallel to the entry surface. The external medium can therefore be brought towards the prism at an angle of 0° to the chip normal until it makes contact with the contact surface, thus enabling, on the one hand, a highly advantageous positioning and alignment of the external medium and, on the other hand, very good coupling efficiency.

[0035] According to a preferred embodiment of the invention, the optical fiber structure is cuboid in shape, and the inlet surface is arranged parallel to the outlet surface. The predetermined angle is therefore 0°. A cuboid optical fiber structure has rectangular surfaces that are parallel to each other. This arrangement enables simple and efficient integration between the waveguide and the external medium. The parallel outlet surface is accordingly perpendicular to the chip normal and also allows the external medium to be brought close to the outlet surface.

[0036] It is possible to arrange the waveguide and the optical coupler in various ways. However, according to a preferred embodiment of the invention, the waveguide and the optical coupler are arranged directly adjacent to each other on an insulating layer. The insulating layer is applied to a substrate, and the entry surface of the optical fiber structure is located on the side of the waveguide and the optical coupler opposite the insulating layer. This arrangement ensures a compact design and efficient light transmission. In this context, according to a preferred embodiment of the invention, the optical coupler is a surface grating coupler. A surface grating coupler is a special type of grating coupler that deflects light out of the chip plane. This increases the flexibility in positioning the optical coupler on the chip.

[0037] In principle, the optical coupling unit can be used to couple into various external media. However, according to a preferred embodiment of the invention, the external medium is an optical fiber, and the optical fiber is arranged perpendicular to the entry surface at the exit surface. "Perpendicular to the entry surface" in this context means parallel to the chip normal. An optical fiber is a waveguide that transmits light over long distances with minimal loss. The optical coupling unit according to the invention enables efficient coupling of the light beam into the optical fiber.

[0038] In principle, the optical fiber structure can be manufactured in various ways. However, according to a preferred embodiment of the invention, the optical fiber structure is manufactured using direct laser writing, two- or multi-photon polymerization, or nanoimprint lithography. These manufacturing processes enable precise and cost-effective production of the optical fiber structure, further improving the flexibility of the optical coupling unit. This makes it possible to attach the grating coupler to a basic structure, which is then shaped into its final form using the aforementioned methods, taking into account the position and type of the external medium. This final shape produces the exit angle corresponding to the position of the external medium, as well as the desired amplitude or intensity of the light beam, in order to efficiently couple it into the external medium.Since the optical fiber structure is made of a structurable plastic, the methods described above can be used to transform the structurable plastic into a structured polymer. The optical fiber structure can therefore be implemented monolithically in the optical coupling unit. The invention is described in more detail below with reference to the drawings and preferred embodiments.

[0039] The drawings show

[0040] Fig. 1a schematically shows an optical coupling unit for coupling a waveguide to an external medium according to a first embodiment of the invention.

[0041] Fig. 1b schematically shows an optical coupling unit for coupling a waveguide to an external medium according to a second embodiment of the invention.

[0042] Fig. 1c schematically shows an optical coupling unit for coupling a waveguide to an external medium according to a third embodiment of the invention.

[0043] Fig. Id schematically shows an optical coupling unit for coupling a waveguide to an external medium according to a fourth embodiment of the invention.

[0044] Fig. 2a shows a perspective view of a light guide structure according to a first embodiment of the invention, and

[0045] Fig. 2b shows a perspective view of a light guide structure according to a second embodiment of the invention.

[0046] Figure 1a shows an optical coupling unit 1 for coupling a waveguide 2 to an external medium 3 according to a first embodiment of the invention. The external medium 3 is an optical fiber. The optical coupling unit 1 comprises an optical coupler 4 and a light guide structure 5 designed as a prism 5. The optical coupler 4 is a surface grating coupler and is applied directly adjacent to the waveguide 2 on an insulating layer 12 of a chip 14. The insulating layer 12 is arranged between a substrate 13 and the optical coupling unit 1 or the waveguide 2.

[0047] The optical coupler 4 couples a waveguide-modulated light beam from the waveguide 2 into an entrance surface 6 of a prism 5 attached to the optical coupler 4 as a Gaussian light beam at a coupler angle d. pone. The light beam is accordingly deflected by the optical coupler by the coupler angle d. p deflected out of the plane of waveguide 2. Prism 5 is a structured polymer with a refractive index n. p and has an exit surface 7 arranged at a predetermined angle to the entrance surface 6. In this case, the predetermined angle is a predetermined prism angle. The entrance surface 6 is applied directly to the optical coupler 4, so that the entrance surface 6 has the profile of the surface grating coupler and beam divergence is reduced when coupling into the entrance surface of the prism 5.

[0048] The inlet surface 6 and the outlet surface 7 are adjacent to each other, such that the predetermined prism angle is formed between them. The inlet surface 6 corresponds to a leg of the prism, and the outlet surface 7 corresponds to a hypotenuse. The prism 5 is truncated at the outlet surface 7 at an angle opposite the predetermined prism angle, thus reducing the size of the outlet surface 7 and forming a contact surface 11. The external medium 3 can be brought sufficiently close to the outlet surface 7 via the contact surface 11.

[0049]

[0050] > arcsin (7 / w p ) applies, an exit angle of 0 can be determined depending on the predetermined prism angle and the refractive index n. vprecisely controlled to ensure improved coupling into the external medium 3 according to the following relationship:

[0051] 6 = arcsin \n p sin (0 p - ^)] + , if |0 + (j>\ > arcsin (7 / ft P The exit surface 7 has a periodic lattice structure 8 and is designed with a metamaterial as a subwavelength lattice.

[0052] Corresponding grating structures 8 are shown in Figures 2a and 2b. Figure 2a shows a subwavelength grating with periodically arranged elements 9, which are trapezoidal in cross-section along an edge of the exit surface 7. Figure 2b, on the other hand, shows a subwavelength grating with periodically arranged elements 9 that are truncated pyramids formed two-dimensionally in the exit surface.

[0053] Figure 1b shows an optical coupling unit 1 according to a second preferred embodiment of the invention. The external medium 3 is arranged perpendicularly, i.e., at an angle of 0° to the chip normal, above the exit surface 7 of the prism 5, which is provided with a grating structure 8. The predetermined prism angle and the refractive index n p The prism 5 is chosen such that the following condition is met:

[0054] 0 p = ( / > -arcsin[sin(^) / w p ].

[0055] This causes the light beam to exit the exit surface 7 at such an exit angle 0 that the light beam is coupled into the external medium 3 parallel to the chip normal.

[0056] Fig. 1c shows an optical coupling unit 1 according to a third embodiment of the invention. The exit surface 7 is provided with the grating structure 8 and is designed as a collimating lens.

[0057] Finally, Fig. Id shows an optical coupling unit according to a fourth embodiment of the invention. In this embodiment, the optical fiber structure 5 is designed as a cuboid with parallel entry surfaces 6 and exit surfaces 7. The optical fiber structure 5 encloses a transition between the optical coupler 4 and the waveguide 2 and has a blaze grating 10 at its exit surface 7. The work leading to this invention was supported by the European Union through the SURQUID project (Grant agreement ID: 899824). Reference reference list

[0058] 1 Optical coupling unit 2 Waveguides

[0059] 3 external medium

[0060] 4 optical couplers

[0061] 5 Light guide structure / prism 6 Entrance area

[0062] 7 Exit area

[0063] 8 Grid structure

[0064] 9 Element

[0065] 10 Blaze Grids

[0066] 11 Contact area

[0067] 12 Insulation layer

[0068] 13 Substrat

[0069] 14 Chip

Claims

Patent claims 1. Optical coupling unit (1) for coupling a waveguide (2) to an external medium (3), comprising an optical coupler (4) and a light guide structure (5), wherein the optical coupler (4) is arranged optically for the transmission of a light beam between the optical fiber structure (5) and the waveguide (2), the light guide structure (5) is optically connected to the external medium (3) for the transmission of the light beam, the optical coupler (4) is designed to deflect the light beam out of the plane of the waveguide (2) and couple it into an entrance surface (6) of the optical fiber structure (5), the light guide structure (5) has an exit surface (7) arranged at a predetermined angle to the entrance surface (6), so that the light beam exits the exit surface (7) at an exit angle given by the predetermined angle and can be coupled into the external medium (3), and the light guide structure (5) has a structured plastic.

2. Optical coupling unit (1) according to claim 1, wherein the optical coupler (4) is configured to deflect the light beam out of the plane of the waveguide (2) by a coupler angle d p to deflect the optical fiber structure (5) to the predetermined angle and a refractive index n p exhibits, and the exit angle 0 is given as follows: if it is true that \() + > arcsin (7 / ft P ).

3. Optical coupling unit (1) according to claim 1 or 2, wherein the optical coupler (4) is configured to deflect the light beam out of the plane of the waveguide (2) by a coupler angle d p to deflect, and the optical fiber structure (5) the predetermined angle as well as a refractive index n p exhibits a condition that is met as follows: 0 p = (j) - arcsin [sin(^) / w p ].

4. Optical coupling unit (1) according to one of the preceding claims, wherein the optical coupler (4) is a grating coupler.

5. Optical coupling unit (1) according to one of the preceding claims, wherein the structured plastic is a structured polymer.

6. Optical coupling unit (1) according to one of the preceding claims, wherein a collimating lens is formed with the exit surface (7).

7. Optical coupling unit (1) according to one of the preceding claims, wherein the exit surface (7) is formed with a metamaterial, and the metamaterial has a periodic lattice structure (8).

8. Optical coupling unit (1) according to claim 7, wherein a grating constant of the grating structure (8) is lower than a wavelength of the light beam, such that a subwavelength grating is formed in the exit surface.

9. Optical coupling unit (1) according to one of claims 7 or 8, wherein the lattice structure (8) has periodically arranged elements (9) which are trapezoidal in cross-section along an edge of the exit surface (7).

10. Optical coupling unit according to one of claims 1 to 7, wherein the exit surface (7) has a non-reflective blaze grating (10), and the blaze grating (10) is configured to transmit the light beam of a single predetermined diffraction order.

11. Optical coupling unit (1) according to one of the preceding claims, wherein the light guide structure (5) is a prism (5), the entrance surface (6) adjoins the exit surface (7) and the predetermined angle is a prism angle formed between the entrance surface (6) and the exit surface (7), wherein the entrance surface (6) is a side surface of the prism (5) corresponding to a leg, and the exit surface (7) is a side surface of the prism (5) corresponding to a hypotenuse.

12. Optical coupling unit (1) according to claim 11, wherein the prism (5) is cut off at an angle opposite to the predetermined prism angle at the exit surface (7) such that the exit surface (7) is reduced and a contact surface (11) is formed.

13. Optical coupling unit (1) according to one of claims 1 to 10, wherein the light guide structure (5) is cuboid and the entry surface (6) is arranged parallel to the exit surface (7).

14. Optical coupling unit (1) according to one of the preceding claims, wherein the waveguide (2) and the optical coupler (4) are arranged directly adjacent to each other on an insulating layer (12), the insulating layer (12) is applied to a substrate (13), and the entry surface (6) of the optical fiber structure (5) is arranged on one side of the waveguide (2) and the optical coupler (4) opposite the insulating layer (12).

15. Optical coupling unit (1) according to one of the preceding claims, wherein the light guide structure (5) is produced by direct laser writing or two- or multi-photon polymerization process or nanoimprint lithography.

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