Optical assembly and method for producing same

Abstract

The invention relates to an optical assembly (10), the integrity and optical properties of which are maintained as much as possible even under changing ambient conditions, and to a method (300) for the production thereof. The optical assembly (10) comprises: at least one component support (20), said component support (20) having a reference plane (100); at least two optical components (30, 40) mounted on the component support (20), each optical component (30, 40) having at least one optical coupling point (50, 55), wherein a mounting plane (110, 120) is defined for each optical component (30, 40), said mounting plane contacting the optical component on the face facing the component support (20) and being parallel to the reference plane (100); at least one free-form optical structure (200), which is connected to at least one of the optical coupling points (50, 55), a spatial region (150) being defined by the free-form optical structure (200) and the mounting planes (110, 120) defined for each optical component (30, 40); at least one protective structure (250) which surrounds the free-form optical structure (200) at least in regions and comprises at least one protective material (251); and at least one filling structure (210) comprising at least one filling material (211). The filling structure (210) at least partially fills the spatial region (150), and the filling material (211) has a smaller relative change in mechanical dimensions than the protective material (251) under ambient conditions which are defined for a use of the assembly (10).

Description

[0001] Optical arrangement and method for its manufacture

[0002] Field of the invention

[0003] The present invention relates to the field of integrated optics, in particular to waveguide structures for optical connections between optical components, in particular between planar-integrated photonic systems (chip-to-chip connections) or between planar-integrated photonic systems and optical fibers (fiber-to-chip connections). The present invention relates to an optical arrangement whose integrity and optical properties are maintained as largely as possible even under changing environmental conditions, as well as to a method for its production.

[0004] State of the art

[0005] In integrated optics, different material platforms are used for optical arrangements, which can also be referred to as "integrated optical systems", preferably indium phosphide (InP), silicon (SiP), silicon nitride (SiN), polymer and glass, with each material platform having its specific advantages and disadvantages. The use of different material platforms, so-called "hybrid integration", offers opportunities to cleverly combine the advantages of the different material platforms. However, cost-effective and technically feasible integration is not trivial. The conventional technique known as "butt coupling" involves directly connecting two components in an alignment with a precision in the low micrometer or even sub-micrometer range.This often requires slow and complex active alignment processes in which the coupling efficiency is continuously monitored while the position of the components is optimized. Furthermore, the adaptation of the various mode fields of the components must be carried out directly on the respective component. The mode field converters required for this require a significant portion of the chip area and / or additional processing steps during manufacturing. Another approach involves the use of additional components, preferably microlenses, prisms, or micromechanical supports, to adapt the size of the mode field and the emission direction of the light source between the optical components, which leads to comparatively large assemblies. In still other approaches, for example, III-V components (InP components) are mounted on a SiP chip.This approach not only consumes a lot of space on the chip, but also poses a challenge for the heat dissipation of the III-V devices through an underlying silicon-on-insulator (SOI) substrate, since the thermal conductivity of the buried oxide is comparatively low.

[0006] In addition, many optical components require optical connections to optical fibers. As in the case of hybrid integration between InP and SiP material platforms, conventional approaches include the above-mentioned butt coupling or the use of a free-space optical path through optical elements, particularly lenses or mirrors. These processes also frequently employ the technique of active alignment. A fiber optic cable is fixed in an optimized position using a laser welding process or a UV epoxy bonding process, requiring alignment tolerances in the submicrometer range. This process is performed at the component or package level and leads to undesirable throughput limitations with cycle times on the order of minutes to several tens of minutes per package, depending on the complexity of the photonic component to be assembled.

[0007] Photonic Wire Bonding (PWB) is a process for the automated 3D manufacturing of optical connections. The three-dimensional (3D) nanoprinting of freeform optical waveguides is based on two-photon polymerization (TPP) technology using femtosecond lasers with sub-diffraction resolution. A form of photonic wirebond can be adapted to the waveguide dimensions, i.e., the corresponding mode field profiles, of the devices and / or components across different material platforms. Typical waveguide dimensions on optical chips that can be connected using photonic wirebonds range from less than 1 pm for Si WGs, approximately 2 pm to 5 pm for InP chips, and core diameters of approximately 10 pm for single-mode fibers and 62.5 pm for multimode fibers.The position and trajectory of the photonic wire bonds can be adapted to the exact positions of the chips, eliminating the need for high-precision chip alignment, making the technology suitable for automated mass production. PWB enables low-loss coupling between different interfaces.

[0008] To optically connect single-mode waveguides, a photonic wire bond must be dimensioned to be single-mode. For common dimensions, this requires cladding the photonic wire bond with a protective structure made of a selected protective material that provides a desired optical refractive index. Furthermore, the protective structure should stabilize the photonic wire bond so that an optical arrangement can be operated for long periods under a wide variety of environmental conditions. Due to the dimensions of photonic wire bonds, which have a width and thickness of a few micrometers and a length of several hundred micrometers, the challenge is to provide an optical connection using photonic wire bonds in such a way that it functions well under different environmental conditions.For example, if an optical assembly is exposed to fluctuating temperatures from -40 °C to +85 °C, its optical properties must not vary significantly or even degrade. An optical assembly for optically connecting two or more optical components comprises a multitude of different materials with fundamentally different properties, ranging from the mechanical support and the materials of the optical chips to the material of the photonic wire bonds and the protective structure. Under changing environmental conditions, the different materials can change their properties, for example, their thermal expansion, differently.

[0009] To produce an optical arrangement, typically at least one optical component is attached to a component carrier. The optical component is usually a discrete component on its own substrate. Two optical elements integrated on the same substrate, each with its own coupling point, count as one component. The component contains at least one optical coupling point to which, for example, an optical freeform structure, in particular a photonic wire bond, is connected and is at least partially enclosed by a protective structure. The connected freeform structure does not necessarily have to be in mechanical contact with the coupling point; what is crucial is that it has a fixed mechanical relationship with the coupling point and that light emitted from the optical coupling point can interact with the freeform structure.

[0010] According to the prior art, components that are to be connected, for example, with a photonic wire bond, are mounted next to one another on a component carrier, with the height of the components typically being adjusted to one another via the component carrier. Lindenmann et al., J., Lightwave Technol. 33, 755 - 760 (2015) describe an optical arrangement comprising two optical components, a fiber optic cable and a silicon photonic chip, which are mounted on a common component carrier. The component carrier is designed such that a step is present to bring the coupling points of the optical components to approximately the same height. A photonic wire bond, which connects the coupling points to one another, is surrounded by a protective structure between the optical components.This optical arrangement has the disadvantages described above: the protective structure fills the space below the photonic wire bond up to at least the mounting plane of an optical component, so that the minimum volume is determined by at least one component height. As a result, the entire volume of the protective structure below the photonic wire bond will expand or shrink upon temperature changes, exerting a force on the photonic wire bond, which is detrimental to the optical properties and long-term stability of the photonic wire bond.

[0011] Blaicher et al., Light: Science & Applications (2020) 9:71, will present various concepts for connecting optical components using photonic wire bonds. These concepts have in common that a gap between the optical components is at least 100 pm deep and extends at least to the mounting plane of one of the components. As a result, changes in ambient conditions can cause the protective structure surrounding the photonic wire bonds to expand significantly and deform the photonic wire bonds, which is detrimental to their optical properties and long-term stability.

[0012] In addition to the approaches of the two aforementioned publications, Darcie et al., Proc. SPIE 11691, Silicon Photonics XVI, 116910C (2021) also show exemplary arrangements for connecting two optical components. In this case, one optical component (e.g., laser or fiber optic) is mounted on another component (e.g., SiP chip) in a recess, placing the coupling points at approximately the same height, and connected using a freeform structure. One component simultaneously serves as the component carrier. Here, too, the space between the freeform structure and the mounting plane is completely filled with the protective structure. Furthermore, the depth of the gap is determined by the thickness of the component and cannot be selected independently. A further disadvantage of this approach is that the laser transfers its heat directly to the SiP chip, which can lead to undesirable heating of the SiP chip.However, independent heat dissipation cannot be implemented with this type of optical arrangement design.

[0013] Object of the invention

[0014] Based on this, the object of the present invention is to provide an optical arrangement and a method for its production which at least partially overcome the disadvantages and limitations of the prior art.

[0015] The object of the present invention is, in particular, to provide an optical arrangement in which, despite changes in ambient conditions, in particular in temperature, preferably of ± 260 K, particularly preferably of ± 80 K, or in ambient pressure or the occurrence of vibrations, a change in the relative position of the optical components, the optical freeform structure and the protective structure for the optical freeform structure to one another is so small that no significant changes in the optical properties of the optical arrangement occur. Typically expected changes in ambient conditions include temperature changes from -40 °C to +85 °C or from -60 °C to +125 °C or vibrations of the optical arrangement from 10 Hz to 2 kHz with accelerations of up to 20 g and mechanical shocks with accelerations of up to 500 g within one millisecond.

[0016] The change in the optical losses of an optical freeform structure used to couple at least two optical components should preferably be at most 2 dB, particularly preferably at most 0.5 dB, provided that typical fluctuations in the ambient conditions occur, in particular a temperature change of ± 80 K. In the case of a photonic wire bond or a printed 3D microlens that are introduced as an optical freeform structure between two optical components on a common carrier, the change in the optical freeform structure occurring as a result of a relative movement of a protective structure surrounding the optical freeform structure with respect to a position of the coupling points on the optical components should preferably be at most 20 pm, particularly preferably at most 6 pm.

[0017] For a solution that is as general as possible for industrial use, it would also be desirable if no special processing steps were required on the optical component, but instead standardized, commercially available optical components could be used. It would be particularly desirable if the thickness of the protective structure beneath the freeform optical structure were independent of the dimensions of the optical components used and, in particular, not predetermined by the distance of the respective coupling point from the underside of the associated optical component. Furthermore, changes in environmental conditions should have no or at most a negligible influence on the optical properties of the optical components, so that, preferably, the long-term stability of the optical arrangement is ensured.

[0018] Disclosure of the invention

[0019] This object is achieved by an optical arrangement and a method for its production having the features of the independent patent claims. Advantageous further developments, which can be implemented individually or in any combination, are presented in the following description and in the dependent claims.

[0020] In a first aspect, the present invention relates to an optical arrangement. The term "optical arrangement" refers to a multi-part device comprising a plurality of elements that interact in such a way that they are configured to process optical radiation. The optical radiation used for this purpose can, in principle, comprise any type of optical radiation having a wavelength within the optical spectrum or an adjacent spectral range.While the visible optical spectrum has wavelengths from 380 nm to 780 nm, the infrared spectral range comprises wavelengths from 780 nm to 1 nm, in particular from 780 nm to 3 pm, 15 (near infrared, "NIR") or from 3 pm to 8 pm (mid infrared, "MIR"), and the ultraviolet spectral range comprises wavelengths from 1 nm to 400 nm, preferably from 100 nm to 400 nm, in particular from 400 nm to 315 nm ("UV-A"), from 315 nm to 280 nm ("UV-B") or from 280 nm to 100 nm ("UV-C"). A wavelength of 500 nm to 2000 nm is particularly preferred.

[0021] The optical arrangement includes:

[0022] - at least one component carrier, wherein the component carrier has a reference plane;

[0023] - at least two optical components mounted on the component carrier, each optical component having at least one optical coupling point, each optical component being defined with a mounting plane touching the component carrier on the side facing the component carrier and parallel to the reference plane;

[0024] - at least one optical free-form structure connected to at least one of the optical coupling points, wherein a spatial area is defined by the optical free-form structure and the mounting plane defined for each optical component;

[0025] - at least one protective structure surrounding the optical freeform structure at least in part, comprising at least one protective material;

[0026] - at least one filling structure comprising at least one filling material, wherein the filling structure at least partially fills the spatial area, and wherein the filling material has a smaller relative change in mechanical dimensions than the protective material within environmental conditions defined for use of the arrangement.

[0027] The optical arrangement comprises at least one component carrier. The term “component carrier” here refers to a preferably planar substrate that is designed to receive at least one further element, in particular the at least two optical components and the at least one fill structure. The component carrier can preferably be a transparent or non-transparent substrate, preferably comprising glass, silicon, at least one metal, in particular tungsten-copper or Invar36, a ceramic, in particular aluminum nitride or aluminum oxide; however, the use of a different material for the component carrier is possible, in particular in a special embodiment in which, as explained in more detail below, the at least one fill structure can be part of the component carrier. The component carrier used for the optical arrangement has a reference plane.The term "reference plane" refers to an imaginary plane that, apart from tolerance-related deviations, is arranged parallel to an optical axis of the component carrier and the at least two optical coupling points within the optical arrangement, described in more detail below. Particularly preferably, the position of the reference plane in the direction of its surface normal can be selected such that a cross-sectional figure of the reference plane with the component carrier assumes a maximum area. However, the selection of a different reference plane for the component carrier is conceivable.

[0028] The optical arrangement further comprises at least two optical components mounted on the component carrier. The term "optical component" refers to an optical element configured to emit, receive, modify, or transmit light. The optical component can comprise a single optical element or a plurality of optical elements.The optical element can preferably be selected from a glass fiber, in particular a light-conducting single-mode or multi-mode fiber made of organic or inorganic materials; semiconductor-based integrated optical chips, in particular lasers, optical amplifiers, photodiodes, superluminescent diodes, or silicon photonic chips; integrated optical chips based on semiconductors or dielectric materials, preferably glass, silicon dioxide, silicon nitride, or polymers; optical circuit boards; or optical elements for free-space optics, in particular lenses, beam splitters, isolators, thin-film filters, mirrors, or diffraction gratings. Other types of optical components are conceivable, in particular filters, power splitters, or electro-optical modulators.

[0029] Every optical component has at least one optical coupling point. The term "optical coupling point" refers to a portion of the optical component to be connected, through which light can be coupled into an optical component or light can be emitted from an optical component. In simple optical components, such as optical fibers or edge-emitting integrated optical chips, the optical coupling point can also be referred to as a "facet" or "waveguide facet." In photodiodes, the optical coupling point can be identical to a so-called "active area" of a pn junction used for detection, within which the incident light leads to the generation of an electrical signal. In lasers, it can be a light-emitting area at an edge or on a surface.More complex designs of optical coupling points can be configured as grating couplers, so-called "inverse tapers," or as etched micromirrors. However, other types of optical coupling points are possible. For each optical component in the present optical arrangement, a mounting plane is defined for each optical component. This mounting plane, apart from tolerance-related deviations, is arranged parallel to the reference plane and touches the optical component on the side facing the component carrier. The term "mounting plane" refers to an imaginary surface on the component carrier on which the corresponding optical element is mounted. The mounting of the optical element on the component carrier can be carried out in such a way that there is direct contact between the optical element and the component carrier.Alternatively, the optical element can be mounted on the component carrier, in particular by means of an adhesive bonding or soldering process, in such a way that a distance remains between the optical element and the component carrier, which can be advantageous for positioning the optical element on the component carrier. The distance between the optical element and the component carrier can preferably be adjusted by means of an adhesive gap or a spacer. For details regarding the reference plane and the mounting planes, reference is made to the description below together with the figures.

[0030] The optical arrangement further comprises at least one optical freeform structure. The term “optical freeform structure” refers to a structure which, within the framework of technical limitations in terms of resolution and accuracy, can have arbitrarily curved surfaces, at least in some regions. A freeform structure thus differs particularly from classic structural geometries that can be produced using planar microstructuring processes. A combination of these classic planar microstructuring processes generally leads to prism-like three-dimensional structural geometries, each of which has a base surface and top surface that are essentially parallel to the substrate surface and are identical or very similar in shape. Depending on the respective etching or deposition process, side walls that are perpendicular to the substrate surface, inclined, or curved inwards or outwards are connected to one another.In contrast, an optical freeform structure is not subject to these restrictions, or not to the same extent, which makes it possible, in particular, to provide waveguide-based optical coupling elements with non-planar structures in which the center lines of the waveguides forming the coupling element do not have to lie in a common or mutually parallel plane. In a preferred embodiment, the optical freeform structure can comprise a photonic wire bond or a micro-optical structure, preferably a printed 3D microlens; however, the choice of a different optical freeform structure is possible. In particular, the optical freeform structure can be manufactured using an additive nanofabrication process, particularly preferably using two-photon polymerization. In the present optical arrangement, at least one optical freeform structure is connected to at least one of the optical coupling points.The term "connected" here means that an optical freeform structure is in a fixed mechanical relationship with an optical coupling point and that light from the optical coupling point can interact with the freeform structure. However, this does not require the connected freeform structure to be in direct mechanical contact with the optical coupling point. In a particularly preferred embodiment, exactly one optical freeform structure, in particular a photonic wire bond, can serve to provide an optical connection between two remote optical coupling points. In particular, in this embodiment, a lateral distance between the two optical coupling points can be from 10 pm to 10 mm, preferably from 20 pm to 1 mm, particularly preferably from 80 pm to 500 pm.In an alternative embodiment, exactly one optical freeform structure, in particular a printed 3D microlens, can be connected to exactly one of the optical coupling points, so that the optical radiation from a first optical coupling point is guided to a second optical coupling point of a second optical component. However, numerous other embodiments are conceivable.

[0031] According to the invention, a spatial area is defined, on the one hand, by the optical freeform structure and, on the other hand, by the mounting plane defined for each optical component. The term “spatial area” refers to a volume defined by at least two boundary surfaces. If more than one mounting plane can be defined for an optical component, the mounting plane defined for the optical component in question with the smallest distance to the freeform structure is preferably used. The term “shortest distance” refers to a connecting distance between two points that is shorter than any other connecting distance between the two points. In this preferred embodiment, all connecting distances between any points on the optical freeform structure and a respective nearest point on the component carrier run through the defined spatial area.

[0032] The optical arrangement further comprises at least one protective structure which surrounds the optical freeform structure at least in part, preferably completely. The term “protective structure” here refers to a volume filled with a protective material and designed to stabilize the optical freeform structure such that the optical arrangement can be operated for long periods under a wide variety of environmental conditions. Furthermore, the protective structure can also be used for other purposes. In particular, if the optical freeform structure comprises a photonic wire bond, the protective material can further be designed to provide a desired optical refractive index so that an optical waveguide can be formed from the photonic wire bond as the waveguide core and the protective structure surrounding the photonic wire bond as the cladding. Other possibilities are conceivable.

[0033] The protective material comprised by the protective structure can be selected from a variety of materials. In an embodiment in which the optical freeform structure comprises at least one polymer, low-refractive-index polymers are particularly suitable for this purpose, in particular from the group of acrylates or epoxides, polymers that may be fluorinated, or polymers that may contain polysiloxane-based components; however, the use of other substances is possible. The protective material can preferably have an optical refractive index of 1 to 1.8, particularly preferably of 1.2 to 1.5, in particular of 1.3 to 1.47. An optical refractive index difference between the material of the optical freeform structure and the protective material can preferably be from 0.02 to 1, particularly preferably from 0.05 to 0.5, in particular from 0.1 to 0.3.The protective material can preferably be selected so that it has the lowest possible absorption at an operating wavelength of the optical freeform structure. The material absorption of the cladding material is at most 10 dB / mm, more preferably at most 5 dB / mm, in particular at most 2 dB / mm, 1 dB / mm, or 0.5 dB / mm, within a wavelength range from 250 nm to 5000 nm, preferably from 400 nm to 2500 nm, more preferably from 530 nm to 2300 nm, in particular from 530 nm to 1650 nm.

[0034] The above-mentioned problem of the present invention is solved in particular by at least one filler structure, which is further comprised by the optical arrangement. The at least one filler structure at least partially fills the spatial region which is defined, on the one hand, by the optical freeform structure and, on the other hand, by the mounting plane defined for each optical component. In this case, the spatial region which comprises all connecting paths between any points of the optical freeform structure and the nearest point on the respective mounting plane is particularly preferred. The term "at least partially filling" refers to the presence of a filler structure in a volume, wherein the filler structure is present wholly or partially in the volume.In a particularly preferred embodiment, the spatial region can be filled with the filling material up to a height of less than 200 pm, particularly preferably less than 100 pm, below the optical coupling points.

[0035] By using the filler structure proposed here, the influence of the relative change in mechanical dimensions of the protective structure on other mechanical properties and / or optical properties of the optical freeform structure can be reduced. The term "relative" takes into account that a change in the mechanical dimensions of a structure also depends on the properties of the structure's material. It therefore specifies that the filler material exhibits a smaller change in mechanical dimensions than the protective material in the direction perpendicular to the reference plane or one of the mounting planes. This corresponds to the same effect as if the protective material and the filler material were replaced together by a common material whose change in mechanical dimension under changing ambient conditions corresponds to the average value between the protective material and the filler material.

[0036] The filler material encompassed by the filler structure can preferably be selected such that, within the ambient conditions specified for the use of the optical arrangement, it exhibits a smaller variation in relative mechanical dimensions than the protective structure for the optical freeform structure. The term "ambient conditions" refers to external parameters acting on the optical arrangement, in particular on the optical freeform structure. These include, in particular, temperature, ambient pressure, or vibrations that impact the optical arrangement from the outside.Despite changes in temperature, ambient pressure, or the occurrence of vibrations, the use of the filling structure ensures that any change in the relative position of the optical components, the optical freeform structure, and the protective structure for the optical freeform structure is so small that no significant changes in the optical properties of the optical arrangement occur. Typically expected changes in ambient conditions for the optical arrangements presented here can include temperature changes from -40 °C to +85 °C or from -60 °C to +125 °C, or vibrations of the optical arrangement from 10 Hz to 2 kHz with accelerations of up to 20 g, and mechanical shocks with accelerations of up to 500 g within one millisecond; however, changes across other ranges are conceivable.

[0037] In a particularly preferred embodiment, the filling material can have a lower thermal expansion coefficient compared to the thermal expansion coefficient of the protective material. The term "low thermal expansion coefficient" here includes one that is at most 100 • 10' 6 / K, preferably no more than 50 • 10' 6 / K, particularly preferably not more than 20 • 10' 6 / K, in particular not more than 10 • 10' 6 / K. Preferably, a combination of the filler material and the protective material has an average thermal expansion coefficient that is at least a factor of 2 lower than the thermal expansion coefficient of the protective material alone. In a particular embodiment, the thermal expansion coefficient of the filler material can differ from the thermal expansion coefficient of a material of each optical component and / or the component carrier by at most 80%, preferably by at most 40%, particularly preferably by at most 20%.

[0038] Materials with a low thermal expansion coefficient are preferred for the filler structure. These include, in particular, tungsten, copper, or Invar36, silicon, ceramics, glasses, UV-curing polymers, or two-component adhesives; however, the use of at least one other filler material is possible.

[0039] In a particular embodiment, the protective material can be an optically transparent material. In this embodiment, the optical refractive index of the filler material can preferably correspond to the optical refractive index of the protective material within a difference of 0.25.

[0040] The filling structure can preferably represent an independent filling structure; in a particular embodiment, it can be part of one of the optical components or of the component carrier. The filling structure can therefore preferably be a material additionally introduced into the arrangement. In a particularly preferred embodiment, the filling structure can comprise a filling element made of a solid filling material and introduced into the spatial region. Alternatively, the filling structure can comprise a material cured in the spatial region. In a particularly preferred alternative embodiment, the filling structure can be firmly or detachably connected to the component carrier or be part of the component carrier, wherein the component carrier and the filling structure can preferably comprise the same material, i.e. the filling material.In a particularly preferred alternative embodiment, the filling structure can be permanently or detachably connected to at least one of the optical components or can be part of at least one of the optical components. In a particular embodiment, the filling structure can serve as a mechanical stop for positioning the optical component.

[0041] In a further aspect, the present invention relates to a method for producing an optical arrangement, in particular the optical arrangement described in more detail above or below. The present method comprises the following method steps, wherein one or more, in particular successive method steps, can also be carried out at least partially simultaneously: a) providing at least one component carrier, wherein the component carrier has a reference plane; b) attaching at least two optical components, each having at least one optical coupling point, to the component carrier, whereby a mounting plane is defined for each optical component, touching the component carrier on the side facing the component carrier and parallel to the reference plane;c) Connecting at least one optical freeform structure to at least one of the optical coupling points, wherein the at least one optical freeform structure is at least partially surrounded by at least one protective structure comprising at least one protective material, wherein a spatial area is defined by the optical freeform structure and the mounting plane defined for each optical component; d) At least partially filling the spatial area by means of at least one filling structure made of at least one filling material, wherein the filling material has a smaller relative change in mechanical dimensions than the protective material within environmental conditions defined for use of the arrangement;

[0042] In a particularly preferred embodiment, process step d) can be carried out directly after process step a), directly after process step b) or simultaneously with process step b); however, a different order of the process steps is possible.

[0043] According to method step a), at least one component carrier is provided, in particular at least one of the component carriers described in more detail above or below. As already described above, the component carrier has a reference plane.

[0044] According to method step b), at least two optical components, each of which has at least one optical coupling point, as described in more detail above or below, are mounted on the component carrier. This defines a mounting plane for each optical component, which is arranged parallel to the reference plane and touches the optical component on the side facing the component carrier.

[0045] According to method step c), as described in more detail above or below, at least one optical freeform structure is connected to at least one of the optical coupling points, wherein a spatial region is defined by the optical freeform structure, the component carrier, and the optical component. A spatial region is defined, on the one hand, by the optical freeform structure and, on the other hand, by the mounting plane defined for each optical component. In particular, the optical freeform structure can be produced using an additive nanofabrication process, particularly preferably using two-photon polymerization; however, the use of another process is possible. According to method step d), the spatial region is at least partially filled, preferably not completely filled, by at least one filling structure made of at least one filling material. In a preferred embodiment, the at least partial filling of the spatial region can be...

[0046] - an independent filling structure, in particular a solid filling element, is introduced into the spatial area;

[0047] - a precursor structure of a filling element is introduced into the spatial area and processed into the filling element, in particular by applying heat to the precursor structure;

[0048] - an optical component which already comprises a filling element or to which a filling element is attached is applied to the component carrier in such a way that the filling element is thereby brought into the later spatial area;

[0049] - at least one component carrier which already comprises a filling element or to which a filling element is attached is provided and the optical elements are applied to the component carrier in such a way that the filling element thereby reaches the later spatial area.

[0050] According to the invention, a filling material is used for this purpose which has a smaller relative change in mechanical dimensions than the protective material within environmental conditions defined for use of the arrangement.

[0051] For further details regarding the present method, reference is made to the description of the optical arrangement according to the invention.

[0052] Advantages of the invention

[0053] The present optical arrangement has a number of advantages over the optical arrangements known from the prior art. In the optical arrangement provided, despite changes in ambient conditions, in particular in temperature, preferably of ± 260 K, particularly preferably of ± 80 K, or in ambient pressure, or the occurrence of vibrations, a change in the relative position of the optical components, the optical freeform structure, and the protective structure for the optical freeform structure to one another is so small that no significant changes in the optical properties of the optical arrangement occur. The change in the optical losses of the optical freeform structure preferably affects at most 2 dB, particularly preferably at most 0.5 dB, provided that typical fluctuations in the ambient conditions, in particular a temperature change of ± 80 K, occur.In the case of a photonic wire bond or a printed 3D microlens, the change in the optical freeform structure occurring due to a local relative movement of the protective structure with respect to a position of the coupling points on the optical components is preferably at most 20 pm, particularly preferably at most 6 pm, in particular at most 2 pm, wherein the change in the optical losses is typically smaller the smaller the movement of the protective structure and thus of the photonic wire bond is.

[0054] The present optical arrangement is particularly suitable for industrial use because no special processing steps are required on the optical component; instead, standardized, commercially available optical components can be used. The thickness of the protective structure beneath the freeform optical structure is independent of the dimensions of the optical components used, while the freeform optical structure is not predetermined by the distance of the respective coupling point from the underside of the associated optical component. Furthermore, changes in environmental conditions have no or at most a negligible influence on the optical properties of the optical components, thus ensuring the desired long-term stability of the optical arrangement.

[0055] Herein, the terms "have," "have," "comprise," or "include," or any grammatical variations thereof, are used non-exclusively. Accordingly, these terms can refer both to situations in which, besides the features introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the expression "A has B," "A has B," "A comprises B," or "A includes B" can refer both to the situation in which, apart from B, no further element is present in A (i.e., a situation in which A consists exclusively of B), and to the situation in which, in addition to B, one or more further elements are present in A, for example, element C, elements C and D, or even further elements.

[0056] Furthermore, it should be noted that the terms “at least one” and “one or more” as well as grammatical variations of these terms, when used in connection with one or more elements or features and intended to express that the element or feature can be provided singly or multiple times, are generally only used once, for example when the feature or element is first introduced. When the feature or element is subsequently mentioned again, the corresponding term “at least one” or “one or more” is generally no longer used, without limiting the possibility that the feature or element can be provided singly or multiple times. Furthermore, the terms “preferred”, “preferably”, “in particular”, “for example” or similar terms are used herein in connection with optional features, without limiting alternative embodiments.Thus, features introduced by these terms are optional features, and these features are not intended to limit the scope of the claims, and in particular the independent claims. Thus, as those skilled in the art will recognize, the invention can also be carried out using other embodiments. Similarly, features introduced by "in one embodiment of the invention" or "in an embodiment of the invention" are understood to be optional features, without this being intended to limit alternative embodiments or the scope of the independent claims. Furthermore, these introductory expressions are intended to leave unchallenged all possibilities of combining the features introduced thereby with other features, be they optional or non-optional.

[0057] Short description of the characters

[0058] Further details and features of the present invention will become apparent from the following description of a preferred embodiment, particularly in conjunction with the dependent claims. The respective features can be implemented individually or in combination with one another. The invention is not limited to the embodiments. The embodiments are schematically illustrated in the following figures. Like reference numerals in the figures denote like or functionally identical elements, or elements that correspond to one another in terms of their functions. In detail:

[0059] Figures 1 to 4 each show a schematic representation of a preferred embodiment of an optical arrangement according to the invention; and

[0060] Figure 5 is a schematic representation of a preferred embodiment of a

[0061] Method for producing the optical arrangement according to the invention.

[0062] Description of the embodiments

[0063] Figure 1 shows a schematic representation of a preferred embodiment of an optical arrangement 10 according to the invention, which comprises a first optical component 30 and a second optical component 40, which can preferably be designed as planar lightwave circuits (PLCs), as lasers mounted on a substrate (submolecular), as photodetectors, or as glass fibers. The optical components 30, 40 comprise an optical material 31, 41, which can preferably be selected from silicon, silicon nitride, glass, a polymer, or indium phosphide; however, the use of another optical material is possible. Each of the two optical components 30, 40 has at least one optical coupling point 50, 55. The optical coupling points 50, 55 of the two optical components 30, 40 are arranged relative to one another in such a way that they can be connected by means of an optical freeform structure 200.

[0064] The optical arrangement 10 schematically illustrated in Figure 1 further comprises a common, preferably planar component carrier 20, on which the two optical components 30, 40 are mounted such that they typically have a lateral spacing of 50 pm to 2000 pm, preferably 100 pm to 500 pm, from one another. The component carrier 20 can preferably comprise a carrier material 21, preferably metal, glass, or ceramic; however, the use of another carrier material is possible.

[0065] The optical arrangement 10 schematically illustrated in Figure 1 further comprises the optical freeform structure 200, which connects the optical coupling points 50, 55 encompassed by the two optical components 30, 40. The freeform structure 200 shown in Figure 1 represents a preferred embodiment in the form of a photonic wire bond 205.

[0066] As further shown in Figure 1, a spatial region 150 can be defined by a component height 140, which typically has a value dwo of 100 pm to 2,000 pm, and by the lateral spacing of the optical components 30, 40. The spatial region 150 lies between a mounting plane 110, 120 associated with the respective optical component 30, 40 and the freeform structure 200. According to the invention, it is proposed that the spatial region 150 be at least partially filled with a filling structure 210. In a particularly preferred embodiment, the spatial region 150 can be filled with a filling material 211, starting from an upper edge of the component carrier 20 up to a height of less than 200 pm, particularly preferably less than 100 pm, below the optical coupling points 50, 55. Preferably, the mounting plane 110, 120 defined for each optical component 30, 40 is defined with a smallest distance with a value of dieo or dies to the free-form structure 200.As a result, all connecting lines 160, 165 between any points 160b, 165b on the optical free-form structure 200 and a nearest point 160a, 165a on the respective mounting plane 110, 120 run through the spatial area 150.

[0067] The inventive introduction of the filling structure 210 into the spatial region 150 can take place before or after the production of the freeform structure 200; however, particularly preferably before the introduction of a protective structure 250 comprising at least one protective material 251. Preferably, the smallest distance between the optical freeform structure 200 and the filling structure 210 is less than 100 times the diameter of the optical freeform structure 200, which is preferably measured perpendicular to the local propagation direction of the light.

[0068] The filling material 211 can preferably be selected from:

[0069] - a light-curing material, in particular a UV-curing material;

[0070] - a thermosetting material;

[0071] - a material that hardens at room temperature by means of moisture; or

[0072] - a two-component material with a low thermal expansion coefficient according to the above definition; however, the use of a material other than the filler material 211 is possible. Examples of materials include "Optocast 3410," a silica-filled epoxy with a thermal expansion coefficient of less than 20 • 10' 6 / K, or “EP42HT-2LTE” from MasterBond with a thermal expansion coefficient of less than 12 • 10' 6 / K. Other materials, particularly "glassomer," can also be considered as filler material. When using such materials, high flowability and subsequent curing can simplify their insertion into the space 150 between the optical components 30, 40.

[0073] Figure 2 shows a schematic representation of another preferred embodiment of the optical arrangement 10 according to the invention. In this embodiment, the arrangement 10 also comprises the two optical components 30, 40, which, as described above, are arranged on the common component carrier 20 such that a lateral distance remains between the two components 30, 40 in order to connect the associated coupling points 50, 55 by means of an optical freeform structure 200. In this embodiment, both the coupling points 50, 55 and the freeform structure 200 are arranged only in the upper region of the optical components 30, 40, so that the spatial region 150 is partially filled with a filling element 212 made of a solid filling material 211 with a low thermal expansion coefficient. The filling element 212 is preferably introduced before the production of the optical freeform structure 200 and before the application of the associated protective structure 250.The filling element 212 can, in particular, be selected from a thin element made of glass, silicon, ceramic, or metal that at least partially fills the spatial region 150. Preferred filling materials 211 for the filling element 212 include float glass with a thermal expansion coefficient of 3 • 10'. 6 / K, silicon with 4.2 • 10' 6 / K, quartz glass with 0.6 • 10' 6 / K , WCu with 8 • 10' 6 / K or Invar36 with 2 • 10' 6 / K; however, the use of another filler material with a low thermal expansion coefficient is possible. For this purpose, the filler element 212 can preferably adjoin or be connected to the component holder 20, to one or more of the optical components 30, 40, preferably by means of an adhesive element (not shown). The filler element can adjoin directly to one or more of the optical components 30, 40, wherein the connection can include one or more butt gaps or adhesive gaps. Particularly for practical reasons for producing the optical arrangement 10, it can be advantageous to first attach the filler element 212 to the optical component 30, preferably a glass fiber, and then to attach the optical component 30 together with the filler element 212 to the component carrier 20 and then to connect the second optical element 40 thereto. Numerous other variants of this procedure are possible, however.

[0074] Figure 3 shows a schematic representation of another preferred embodiment of the optical arrangement 10 according to the invention. In this embodiment, a combined component carrier and filling element 22 is designed such that an edge is formed between the optical components 30, 40, which edge defines the lateral distance between the optical components 30, 40 and serves as the partial filling element 212 for the spatial region 150 between the optical components 30, 40, the freeform structure 200 and the mounting planes 110, 120 of the optical components 30, 40. The carrier material 211 of the combined component carrier and filling element 22 also has a low thermal expansion coefficient, preferably less than 200 • 10' 6 / K, particularly preferably less than 100 • 10' 6 / K, especially preferably less than 50 • 10' 6 / K. For the formation of the combined component carrier and filling element 22,

[0075] - Metals such as WCu with a thermal expansion coefficient of 8 • 10' 6 / K;

[0076] - Invar36 with a thermal expansion coefficient of 2 • 10' 6 / K; or

[0077] - (sintered) ceramics with a low thermal expansion coefficient such as AlN or Al2O3; however, the use of a material other than the filler material 211 is also possible here.

[0078] Figure 4 shows a schematic representation of a further preferred embodiment of the optical arrangement 10 according to the invention. The optical arrangement 10 schematically represented in Figure 4 comprises the optical freeform structure 200, which here is embodied as a micro-optical structure, in particular as a printed 3D microlens 206, which is attached to the optical coupling point 50. However, other types of freeform structures are conceivable. Preferably, light from the optical coupling point 50 can be guided through the freeform structure 200 into a further optical coupling point 55. The optical freeform structure 200, which here is in the form of a 3D microlens coupled to the optical coupling point 50, does not necessarily have to be mechanically connected to the coupling point; it can also be mechanically connected only to the optical component 30 or only to the filling structure 210.

[0079] Figure 5 shows a schematic representation of a preferred embodiment of a method 310 for producing the optical arrangement 10 according to the invention, which is described in particular in one of the embodiments according to Figures 1 to 4.

[0080] In a provision step 312 according to method step a), the component carrier 20 is provided, wherein the component carrier 20 has the reference plane 100.

[0081] In an attachment step 314 according to method step b), the first optical component 30, which has the optical coupling point 50, and the second optical component 40, which has the optical coupling point 55, are attached to the component carrier 20. This defines the first mounting plane 110 for the first optical component 30, which touches the first optical component 30 on the side facing the component carrier 20 and is parallel to the reference plane 100. Likewise, the second mounting plane 120 is defined for the second optical component 40, which touches the second optical component 40 on the side facing the component carrier 20 and is also parallel to the reference plane 100.

[0082] In a filling step 316 according to method step d), the spatial region 150 is at least partially filled, preferably not completely filled, by means of at least one filling structure 210 made of the filling material 211. In the preferred embodiment of the method 310 schematically illustrated in Figure 5, method step d) is carried out directly after method step a) or simultaneously with method step b); however, a different order of the method steps (not shown) is possible. As described above, the filling material 211 exhibits a smaller relative change in mechanical dimensions than the protective material 251 within the ambient conditions defined for the use of the arrangement 10.

[0083] In a connection step 318 according to method step c), the optical freeform structure 200 is connected to one or both optical coupling points 50, 55. In this connection, the optical freeform structure 200 is surrounded at least partially, preferably completely, by the protective structure 250, which comprises the protective material 251. As a result, the spatial area 150 is defined by the optical freeform structure 200 and the mounting planes 110, 120 defined for each optical component 30, 40. For further details on Figures 2 to 5, reference is made to the above description of Figure 1.

[0084] List of reference symbols

[0085] 10 optical arrangement 20 component carrier 21 carrier material 22 combined component carrier and filling element

[0086] 30, 40 optical component

[0087] 31, 41 optical material 50, 55 optical coupling point 100 reference plane 110, 120 mounting plane 140 component height

[0088] 150 spatial region 160, 165 connecting lines 160a, 165a nearest point 160b, 165b arbitrary point 200 freeform structure 205 photonic wire bond 206 printed 3D microlens 210 filling structure 211 filling material 212 filling element 250 protection structure 251 protection material 310 method for producing an optical assembly 312 provision step 314 attachment step 316 filling step 318 connection step

Claims

Patent claims 1. Optical arrangement (10), comprising - at least one component carrier (20), wherein the component carrier (20) has a reference plane (100); - at least two optical components (30, 40) mounted on the component carrier (20), each optical component (30, 40) having at least one optical coupling point (50, 55), each optical component (30, 40) having a mounting plane (110, 120) which touches the component carrier (20) on the side facing the optical component and is parallel to the reference plane (100); - at least one optical free-form structure (200) which is connected to at least one of the optical coupling points (50, 55), wherein a spatial area (150) is defined by the optical free-form structure (200) and the mounting planes (110, 120) defined for each optical component (30, 40); - at least one protective structure (250) surrounding the optical freeform structure (200) at least in regions, comprising at least one protective material (251); - at least one filling structure (210) comprising at least one filling material (211), wherein the filling structure (210) at least partially fills the spatial region (150), and wherein the filling material (211) has a smaller relative change in mechanical dimensions than the protective material (251) within environmental conditions defined for use of the arrangement (10).

2. Optical arrangement (10) according to the preceding claim, wherein all connecting paths (160, 165) between any points (160b, 165b) on the optical freeform structure (200) and a respective nearest point (160a, 165a) on the respective mounting plane (110, 120) run through the spatial region (150).

3. Optical arrangement (10) according to one of the preceding claims, wherein the spatial region (150) is filled with the filling material (211) up to a height of less than 200 pm, particularly preferably less than 100 pm, below the optical coupling points (50, 55).

4. Optical arrangement (10) according to one of the preceding claims, wherein a minimum distance between the optical freeform structure (200) and the filling structure (210) is less than 100 times a diameter of the optical freeform structure 200.

5. Optical arrangement (10) according to one of the preceding claims, wherein the filling material (211) has a thermal expansion coefficient of at most 100 • 10' 6 / K.

6. Optical arrangement (10) according to one of the preceding claims, wherein a combination of the filling material (211) and the protective material (251) has an average thermal expansion coefficient that is at least a factor of 2 below the thermal expansion coefficient of the protective material (251) alone.

7. Optical arrangement (10) according to one of the preceding claims, wherein the thermal expansion coefficient of the filling material (211) in the spatial region (150) differs from the thermal expansion coefficient of a material of each optical component (30, 40) by at most 50%.

8. Optical arrangement (10) according to one of the preceding claims, wherein the filling structure (210) - comprises a material cured in the spatial region (150); - a filling element (212) made of a solid filling material (211) introduced into the spatial area (150).

9. Optical arrangement (10) according to one of the preceding claims, wherein the filling structure (210) - is part of the component carrier (20); - is firmly or detachably connected to the component carrier (20), wherein the component carrier (20) preferably also comprises the filling material (211).

10. Optical arrangement (10) according to one of the preceding claims, wherein the filling structure (210) - is fixedly or detachably connected to at least one of the optical components (30, 40); - is part of at least one of the optical components (30, 40).

11. Optical arrangement (10) according to one of the preceding claims, wherein the filling structure (210) serves as a mechanical stop for positioning the optical component (30, 40).

12. Optical arrangement (10) according to one of the preceding claims, wherein a lateral distance between the two optical coupling points (50, 55) is from 10 pm to 10 mm.

13. Optical arrangement (10) according to one of the preceding claims, wherein the optical freeform structure (200) comprises a photonic wire bond (205) or a micro-optical structure.

14. Optical arrangement (10) according to one of the preceding claims, wherein the protective material (251) is an optically transparent material, wherein an optical refractive index of the filling material (211) is lower than the optical refractive index of the protective material (251).

15. A method (310) for producing an optical arrangement (10), in particular according to one of the preceding claims, comprising the method steps: a) providing at least one component carrier (20), wherein the component carrier (20) has a reference plane (100); b) attaching at least two optical components (30, 40), each having at least one optical coupling point (50, 55), to the component carrier (20), whereby for each optical component (30, 40) a mounting plane (110, 120) is defined which touches the component carrier (20) on the side facing the component carrier (20) and is parallel to the reference plane (100);c) connecting at least one optical free-form structure (200) to at least one of the optical coupling points (50, 55), wherein the at least one optical free-form structure (200) is at least partially surrounded by at least one protective structure (250) comprising at least one protective material (251), wherein a spatial region (150) is defined by the optical free-form structure (200) and the mounting planes (110, 120) defined for each optical component (30, 40); d) at least partially filling the spatial region (150) by means of at least one filling structure (210) made of at least one filling material (211), wherein the filling material (211) has a smaller relative change in mechanical dimensions than the protective material (251) within environmental conditions defined for use of the arrangement (10); 16. The method (310) according to the preceding claim, wherein the optical freeform structure (200) is produced by means of an additive nanofabrication process, particularly preferably by means of two-photon polymerization.

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