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); at least one optical component (30, 31) mounted on the component support (20), said optical component (30, 31) having at least one optical coupling point (40, 41); at least one free-form optical structure (50) which is connected to the optical coupling point (40, 41); at least one casing structure (70) which surrounds the free-form optical structure (50) at least in regions, said casing structure (70) comprising at least one viscoelastic casing material (80); and at least one delimiting structure (90), wherein the delimiting structure (90) and the at least one optical component (30, 31) at least partly enclose the casing structure (70), and the casing material (80) has a storage modulus with a maximum value of 1000 kPa.

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 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] For the optical connection of single-mode waveguides, a photonic wire bond should be dimensioned to be essentially single-mode, especially if the trajectory of the photonic wire bond includes bends. For common dimensions, this requires cladding the photonic wire bond with a cladding structure made of a selected cladding material that provides a desired optical refractive index, so that, together with the material of the photonic wire bond, a corresponding index contrast is established. Furthermore, the cladding structure should stabilize the photonic wire bond so that an optical arrangement can be operated over long periods under a wide range 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 diverse environmental conditions. For example, if an optical assembly is exposed to fluctuating temperatures from -40 °C to +85 °C, the optical properties must not vary significantly or even degrade. An optical assembly for the optical connection of 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 cladding structure.Under changing environmental conditions, different materials can change their properties, such as their thermal expansion, differently.

[0009] US 2013 / 0223788 A1 discloses that a freeform structure is embedded in a UV- or heat-curable polymer material, such as CYTOP, a fluoropolymer with a refractive index of approximately 1.37, a Shore D hardness of 78, and a coefficient of linear expansion (CTE) of 74 ppm / K. The curable polymer tightly encloses the freeform structure; the polymer is localized around the optical coupling point. However, the approximately 10-fold higher CTE compared to optical components made of silicon, InP, or glass leads to strong relative movement between the cladding material and the optical components under variable environmental conditions.Due to the high hardness of the cladding material, the embedded freeform structure generally follows this relative movement, which can lead to high optical losses, up to a complete loss of optical coupling, when the freeform structure is separated from the optical coupling point of the optical device.

[0010] Billah et al., "Hybrid integration of silicon photonics circuits and InP lasers by photonic wire bonding," Optica Vol. 5 (7), 2018, pp. 876-883, propose using an index oil as the cladding material to achieve a suitable refractive index contrast between the freeform structure and the cladding material. However, the problem here is that the oil dripped onto the coupling point can flow out of the optical coupling region, which does not lead to a long-term stable device.

[0011] Object of the invention 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.

[0012] 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 up to ± 260 K, particularly preferably of up to ± 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 cladding 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.

[0013] The change in the optical losses of an optical freeform structure used for the optical coupling of at least two optical components should preferably be at most 2 dB, particularly preferably at most 0.5 dB, if 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 cladding 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.

[0014] It would also be desirable if the optical properties of the optical connection could be kept constant, and if the cladding structure could remain localized in the area of ​​the optical coupling of at least two optical components and neither melt nor move over an extended period of time, thus contaminating other optical components located near the optical coupling point. Furthermore, changes in environmental conditions should have no or at most a negligible influence on the optical properties of the optical components, thus preferably ensuring long-term stability of the optical arrangement.

[0015] Disclosure of the Invention 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.

[0016] 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.

[0017] The optical arrangement includes:

[0018] - at least one component carrier;

[0019] - at least one optical component mounted on the component carrier, wherein the optical component has at least one optical coupling point;

[0020] - at least one optical freeform structure connected to the optical coupling point;

[0021] - at least one cladding structure which surrounds the optical freeform structure at least in regions, wherein the cladding structure comprises at least one viscoelastic cladding material;

[0022] - at least one boundary structure, wherein the boundary structure and the optical component form an at least partial enclosure for the cladding structure; wherein the cladding material has a storage modulus having a maximum value of 1000 kPa.

[0023] The present optical arrangement comprises at least one component carrier. The term "component carrier" refers to a preferably planar substrate configured 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 another material for the component carrier is possible.

[0024] The present optical arrangement further comprises at least one optical component 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.

[0025] The at least one 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, via 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 designed as grating couplers, so-called "inverse tapers," or as etched micromirrors. However, other types of optical coupling points are possible.

[0026] The present 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, making 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.

[0027] 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 fixed 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, the 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 is guided from a first optical coupling point to a second optical coupling point of a second optical component. However, a multitude of further embodiments are conceivable.

[0028] The present optical arrangement further comprises at least one cladding structure which surrounds the optical freeform structure at least in part, preferably completely. The term “cladding structure” here refers to a volume filled with a cladding material and designed to stabilize the optical freeform structure such that the optical arrangement can be operated for a long time under a wide variety of environmental conditions. Furthermore, the cladding structure can also be used for other purposes. In particular, if the optical freeform structure comprises a photonic wire bond, the cladding 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 cladding structure surrounding the photonic wire bond as the cladding.Further possibilities are conceivable.

[0029] The cladding material encompassed by the cladding structure can be selected from a variety of materials. In an embodiment in which the optical freeform structure comprises at least one polymer, particularly suitable materials are low-refractive-index polymers, especially from the group of acrylates or epoxides, polymers that may be fluorinated, polymers that may contain polysiloxane-based components, or oils; however, the use of other substances is possible.

[0030] According to the invention, the sheath material has a storage modulus with a maximum value of 1000 kPa. The term "storage modulus" refers to the energy stored in the object after a force is applied to it, whereby the application of the force can be dynamic or static. Part of this energy can be recovered from the object after the applied force has been released.

[0031] In a particularly preferred embodiment, the storage modulus can furthermore be at most a factor of 1000 greater than a loss modulus of the sheath material. In this case, the term “loss modulus” refers to a further part of this energy which remains in the object after the applied force has been relieved of the object, in particular after it has been converted into heat through internal friction. The specification of the loss modulus thus refers to a viscous portion of the material in the object. In a preferred embodiment, the sheath material can have a non-negligible viscous portion. This means that the material has a so-called “strain relieving” property, i.e. stresses can be reduced over time through external deformation of the sheath material.

[0032] In a preferred embodiment, the storage modulus can have a maximum value of 500 kPa, particularly preferably 200 kPa, in particular 100 kPa, and the storage modulus of the jacket material can be greater than the loss modulus of the jacket material by a factor of at most 500, particularly preferably by a factor of at most 200, in particular by a factor of at most 100. In a further preferred embodiment,

[0033] - the storage modulus has a value of 0.1 kPa to 60 kPa, preferably 1 kPa to 30 kPa, particularly preferably 2 kPa to 15 kPa; and

[0034] - the loss modulus has a value of 0.01 kPa to 30 kPa, preferably 0.05 kPa to 10 kPa, particularly preferably 0.1 kPa to 5 kPa.

[0035] In a preferred embodiment, the value of the storage modulus may be lower than the value of the loss modulus of the sheath material, so that the behavior of the sheath material corresponds to that of a liquid.

[0036] In a preferred embodiment, a value for the storage modulus can be set such that, within ambient conditions specified for use of the optical arrangement, the cladding material essentially retains its spatial position and shape and continues to surround at least the freeform structure, at least in part. 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 fill structure ensures that any change in the relative position of the optical components, the optical freeform structure, and the cladding structure to one another is so small that no significant changes in the optical properties of the optical arrangement occur. Typical 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 further preferred embodiment, a value for a shear modulus of the sheath material can be set such that, during a local relative movement between the sheath structure and the free-form structure within the ambient conditions specified for use of the arrangement, a shear stress of the sheath material surrounding the free-form structure is so low that the free-form structure essentially retains its spatial position and shape. The term "shear modulus" refers to a parameter of a material that indicates a linear-elastic deformation of an object comprising this material as a result of a shear stress or a shear force, wherein the deformation can occur dynamically or statically.A significant deformation or displacement in the optical arrangement occurs when the optical coupling between the two components via the freeform structure changes by at least 1.5 dB, preferably by at least 1.0 dB, in particular by at least 0.5 dB. It can be assumed that smaller deformations or displacements of the freeform structure, which do not affect the optical coupling losses, relax upon returning to the original ambient conditions.

[0038] The cladding material can preferably have an optical refractive index of 1 to 1.8, particularly preferably 1.2 to 1.5, in particular 1.3 to 1.47. An optical refractive index difference between the material of the optical freeform structure and the cladding material can preferably be 0.02 to 1, particularly preferably 0.05 to 0.5, in particular 0.07 to 0.2. In a particular embodiment, the cladding material can be an optically transparent material. For this purpose, the cladding material can preferably be selected such that the lowest possible absorption occurs at an operating wavelength of the optical freeform structure. The material absorption of the cladding material is at most 10 dB / mm, particularly 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, particularly preferably from 530 nm to 2300 nm, in particular from 530 nm to 1650 nm.

[0039] The present optical arrangement further comprises at least one delimiting structure which, together with the optical component and optionally further elements, in particular the component carrier, forms an at least partial enclosure for the cladding structure. The term “delimiting structure” here refers to a volume filled with a delimiting material and which, alone or with the additional use of at least one further structure, is designed to stabilize the cladding structure in such a way that the optical arrangement, in particular the at least one optical freeform structure comprised thereby, can be operated over a long period of time under a wide variety of environmental conditions. In a preferred embodiment, the delimiting structure, together with the at least one optical component and the at least one component carrier, can form an at least partial enclosure for the cladding structure.

[0040] The boundary material can preferably be selected from at least one crosslinkable polymer, preferably based on an epoxy, acrylate, or silicone, or a combination thereof. The boundary structure can, in particular, also be configured to form both a lateral boundary (dam) and a boundary on a top side (encapsulation) of the optical arrangement 10. The crosslinking of the at least one polymer can preferably be achieved by UV exposure, thermal exposure, at room temperature using moisture, and / or a two-component reaction.

[0041] In a preferred embodiment, the boundary structure can be configured such that, upon a change in the volume of the shell structure, the pressure inside the shell structure remains substantially constant. The term "substantially constant" refers to the fact that, if the boundary structure is configured elastically, the pressure may increase by a small amount, particularly if a change in the volume of the shell structure, for example, due to thermal expansion, leads to an increase in pressure within the volume enclosed by the boundary structure. Rather, the boundary structure itself can be deformed due to its elastic configuration.For this purpose, at least a portion of the boundary structure can be formed from a thin layer, preferably 1 mm or less, particularly preferably 0.5 mm or less, in particular 0.1 mm or less, of the boundary material, wherein the boundary material can have a hardness preferably of Shore A 80 or less, particularly preferably Shore A 50 or less. The boundary material can preferably have a higher storage modulus than the sheath material.

[0042] In a further preferred embodiment, the boundary structure can be in the form of a cover, which can in particular comprise a thin glass or a thin cover membrane. The cover can preferably be adhesively bonded to at least one optical component and, more preferably, to at least one further part of the boundary structure. The elasticity of the boundary structure can also be adjusted via the material and thickness of the cover. In a particular embodiment, the boundary structure can have at least one adhesive joint or an additionally applied structure.

[0043] In an alternative embodiment, the boundary structure can comprise an outer region of the shell structure, referred to as the "shell," wherein an inner region of the shell structure, referred to as the "core," comprises the viscoelastic shell material. The shell can have a thickness of at most 100 μm, particularly preferably at most 50 μm. The core can be a liquid material, while the "shell" can comprise a solid material.

[0044] In a preferred embodiment, the optical arrangement can additionally have at least one opening in the boundary structure. In this case, the size of the opening can be selected such that the viscoelastic cladding material cannot flow out in the event of volume changes, but is held in the enclosed volume by surface tension. This allows the liquid cladding material to be held in position, while at the same time, in the event of volume changes, in particular due to thermal expansion, no pressure changes can occur inside the boundary structure, which could have a negative effect on the optical arrangement, in particular the freeform structure. The at least one opening in the boundary structure can have lateral dimensions of preferably 200 pm or less, particularly preferably 100 pm or less, in particular 50 pm or less.

[0045] 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; b) Attaching at least one optical component, which has at least one optical coupling point, to the component carrier; c) Connecting at least one optical free-form structure to the at least one optical coupling point; d) At least partially surrounding the optical free-form structure with at least one cladding structure, wherein the cladding structure comprises at least one viscoelastic cladding material; e) Creating at least one boundary structure such that the boundary structure and the optical component form an at least partial enclosure for the cladding structure, wherein the cladding material is selected such that it has a storage modulus having a maximum value of 1000 kPa.

[0046] 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.

[0047] According to method step b), at least one optical component, which, as described in more detail above or below, has at least one optical coupling point, is attached to the component carrier.

[0048] According to process step c), as described in more detail above or below, at least one optical freeform structure is connected to the at least one optical coupling point. In particular, the optical freeform structure can be manufactured using an additive nanofabrication process, particularly preferably using two-photon polymerization; however, the use of another process is possible.

[0049] According to method step d), the optical freeform structure is surrounded at least partially by at least one cladding structure, wherein the cladding structure comprises at least one viscoelastic cladding material, wherein the cladding material is selected such that it has a storage modulus with a maximum value of 1000 kPa. Particularly preferably, the storage modulus can be at most a factor of 1000 greater than a loss modulus of the cladding material.

[0050] According to method step e), at least one boundary structure is created such that the boundary structure and the optical component form an at least partial enclosure for the cladding structure. The boundary structure can preferably be created by applying the boundary structure to the cladding structure. The boundary structure can also be applied, at least in part, before method step d). In an alternative embodiment, the boundary structure can be created by treating the outer region of the cladding structure, referred to as the "shell", with the viscoelastic cladding material remaining in the inner region of the cladding structure, referred to as the "core". The treatment can preferably be carried out by means of UV exposure, thermal exposure, at room temperature using moisture and / or a two-component reaction.The treatment forms the shell, which has a thickness of at most 100 pm, particularly preferably at most 50 pm.

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

[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 also allows the optical properties of the optical connection to be kept constant, and the cladding structure can remain localized in the area of ​​the optical coupling of at least two optical components. It would neither melt nor move over an extended period of time, thus contaminating other optical components located near the optical coupling point. 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 may be provided singly or multiple times, are generally used only 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 may be provided singly or multiple times.

[0057] 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 an embodiment of the invention" or by "in an embodiment of the invention" are understood to be optional features, without limiting alternative embodiments or the scope of the independent claims.Furthermore, these introductory expressions are intended to leave untouched all possibilities of combining the features introduced thereby with other features, whether optional or non-optional.

[0058] Short description of the characters

[0059] 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:

[0060] Figures 1 to 3 each show a schematic representation of a preferred embodiment of an optical arrangement according to the invention; and

[0061] Figure 4 is a schematic representation of a preferred embodiment of a

[0062] Method for producing the optical arrangement according to the invention.

[0063] Description of the embodiments

[0064] Figure 1 shows a schematic representation of a preferred embodiment of an optical arrangement 10 according to the invention, which typically comprises a first optical component 30 and a second optical component 31. The optical components 30, 31 can preferably be selected from a silicon photonic chip, in particular a silicon-on-insulator (SOI chip), a laser made of indium phosphide (InP), a photonic chip based on silicon nitride or lithium niobium oxide, or a single-mode fiber. As can also be seen from Figure 1, the optical components 30, 31 are mounted on a common component carrier 20, wherein the component carrier 20 can preferably comprise aluminum nitride or tungsten-copper; however, the use of a different material for the component carrier 20 is possible.In a special embodiment (not shown), one optical component can simultaneously serve as a carrier for the other optical component, particularly when an InP laser is placed on an SOI chip. Each of the two optical components 30, 31 has at least one optical coupling point 40, 41. The optical coupling points 40, 41 of the two optical components 30, 31 are arranged relative to one another in such a way that they can be connected by means of an optical freeform structure 50.

[0065] The optical arrangement 10 further comprises an optical freeform structure 50, which connects the optical coupling points 40, 41 encompassed by the two optical components 30, 31. The freeform structure 50, shown schematically in Figure 1, comprises a material 60, in particular a polymer, which is produced by 3D lithography, specifically by two-photon polymerization. It is not necessary for the freeform structure 50 to be in direct mechanical contact with the optical coupling points 40, 41; rather, it is sufficient if light from the optical coupling points 40, 41 can interact with the freeform structure 50. As shown in Figure 1, the freeform structure 50 can preferably be designed as a photonic wire bond. In an alternative embodiment according to Figure 2, the freeform structure 50 can be designed as a microlens, which enables optical coupling.

[0066] In particular, in order to achieve an adapted refractive index contrast, the freeform structure 50 is, according to the invention, at least partially surrounded by a cladding structure 70, wherein the cladding structure 70 comprises at least one viscoelastic cladding material 80. The refractive index contrast between the freeform structure 50 and the cladding structure 70 can preferably assume a value of 0.01 to 1.0, particularly preferably from 0.05 to 0.2. For example, a photonic wire bond as the freeform structure 50 can have a refractive index of 1.5, while the cladding material 80 assumes a refractive index of 1.4. The cladding material 80 can preferably be substantially transparent to light with a wavelength of 190 nm to 10.7 pm, particularly preferably from 400 nm to 2.5 pm, in particular from 530 nm to 1.8 pm. In a preferred embodiment, the cladding material 80 can be liquid and in this case can have a viscosity preferably of 1 cm 2 / s up to 1,000,000 cm2 / s, especially preferably from 100 cm 2 / s up to 100000 cm 2 / s, especially 1 000 cm 2 / s and 50000 cm 2 / s. The viscoelastic sheath material can preferably be a so-called index oil, for example "Cargille Series A", fluids based on monomer mixtures, siloxane-based fluids, or hydrocarbon-based oils.

[0067] In a further embodiment, the shearing material 80 is not liquid, but a viscoelastic material, wherein a value for the shear modulus of the shearing material 80 is selected such that in the event of a local relative movement between the shearing structure 70 and the free-form structure 50 attached to the at least one coupling point 40, 41 due to changing ambient conditions, in particular temperature changes, vibrations or even during the curing of applied materials, the shear stress of the viscoelastic material surrounding the free-form structure 50 is so low that no significant deformation or displacement of the free-form structure 50 occurs. At the same time, the storage modulus of the shearing material 80 can be selected such that it is dimensionally stable, i.e. it does not flow under the influence of gravity and / or typical ambient conditions, in particular temperatures from -40 °C to +85 °C and / or vibration or shock tests up to 500 g.

[0068] For this purpose, the sheath material 80 can be embodied as a gel-like material, preferably based on at least one epoxy, acrylate, or siloxane, or a mixture thereof. The viscoelastic material can be applied in liquid form and can be crosslinked by UV exposure, thermal exposure, at room temperature through moisture, or by means of a two-component reaction. The storage modulus of the crosslinked sheath material 80 can preferably be from 0.1 kPa to 50 kPa, particularly preferably from 1 kPa to 20 kPa, in particular from 2 kPa to 10 kPa, while the loss modulus can preferably be from 0.01 kPa to 20 kPa, particularly preferably from 0.05 kPa to 5 kPa, in particular from 0.1 kPa to 2 kPa. As a result, the freeform structure, which can preferably be designed as a photonic wire bond or as an optical lens, can have a hardness of Shore D 50 to 80 or higher and a shear modulus > 50 MPa and does not deform significantly during thermal expansion.

[0069] A shear modulus of the cladding material 80 can preferably be selected such that, in the event of a local relative movement between the cladding structure 70 and the freeform structure 50 due to changing ambient conditions, preferably during temperature changes from -40 °C to +85 °C, particularly preferably between -60 °C and 125 °C, the shear stress of the cladding material 80 is so low that no significant deformation or displacement of the freeform structure 50 occurs. A significant deformation or displacement occurs when the optical coupling by means of the freeform structure 50 between the two components 30, 31 changes by at least 1.5 dB, in particular by at least 0.5 dB. As mentioned above, it can be assumed that smaller deformations or displacements of the freeform structure, which do not influence the optical coupling losses, relax again upon return to the original ambient conditions.

[0070] In order to hold the viscoelastic cladding material 80 in position around the free-form structure 50, in the embodiment according to Figure 1, the cladding structure 70 is enclosed by the component carrier 20, the two optical components 30, 31, and a boundary structure 90. For this purpose, the boundary structure 90 can comprise a material 100 that is preferably selected from at least one crosslinkable polymer. The polymer can preferably be based on an epoxy, acrylate, or silicone, or a combination thereof. For this purpose, the boundary structure 90 can, in particular, be configured to form both a lateral boundary (dam) and a boundary on an upper side (encapsulation) of the optical arrangement 10. The crosslinking of the at least one polymer can preferably take place by means of UV illumination, thermal exposure, at room temperature using moisture, and / or by means of a two-component reaction.

[0071] It can be particularly advantageous if the boundary structure 90 is designed to be elastic, so that a change in the volume of the casing structure 70, for example due to thermal expansion, cannot lead to an increase in pressure within the volume enclosed by the boundary structure 90, but rather the boundary structure 90 itself can be deformed. This can be achieved in particular if at least part of the boundary structure is formed from a thin layer, preferably 1 mm or less, particularly preferably 0.5 mm or less, in particular 0.1 mm or less, of the boundary material 100, wherein the boundary material can have a hardness preferably of Shore A 80 or less, particularly preferably Shore A 50 or less. The boundary material 100 can preferably have a higher storage modulus than the casing material 80.

[0072] In a further embodiment, the boundary structure 90 can be in the form of a cover, in particular made of thin glass or a thin cover membrane, wherein the cover can be adhesively bonded to the optical components 30, 31 and, preferably, to at least one further part of the boundary structure 90. The elasticity of the boundary structure 90 can also be adjusted via the material and thickness of the cover. Furthermore, the boundary structure 90 can also have adhesive joints or additionally applied structures.

[0073] As schematically illustrated in Figure 1, the optical arrangement 10 can comprise the two optical components 30, 31 on the common component carrier 20, wherein the two optical components 30, 31 are optically connected to one another by means of the freeform structure 50. As described above, the freeform structure 50 is surrounded, at least in regions, by the cladding structure 70 made of the viscoelastic cladding material 80, wherein the cladding structure 70 is held in position by the at least one delimiting structure 90.

[0074] Figure 2 shows an alternative embodiment in which the optical arrangement 10, in which the cladding structure 70 is completely enclosed by the two components 30, 31, the component carrier 20, and the delimiting structure 90, additionally has at least one opening (not shown) in the delimiting structure 90. The size of the opening can be selected such that the viscoelastic cladding material 80 cannot flow out in the event of volume changes, but is held in the enclosed volume by surface tension. As a result, the liquid cladding material 80 can be held in position, while at the same time, in the event of volume changes, in particular due to thermal expansion, no pressure changes can occur inside the delimiting structure 90, which could have a negative effect on the optical arrangement 10, in particular the freeform structure 50.As mentioned above, the at least one opening in the boundary structure can have lateral dimensions of preferably 200 pm or less, particularly preferably 100 pm or less, in particular 50 pm or less.

[0075] While in the embodiment according to Figure 1 the typically incompressible, viscoelastic cladding material 80 is completely enclosed by the optical components 30, 31, the component carrier 20 and the boundary structure 90, in the embodiment according to Figure 2 the volume enclosed within the boundary structure 90 comprises a small gas volume 110, which may in particular comprise nitrogen or air. As a result, the viscoelastic cladding material 80 can be held in position, while at the same time no significant increase in pressure can occur in the event of volume changes, in particular due to thermal expansion, in particular since any pressure changes can be compensated by the compressible gas. The enclosed gas volume can be positioned such that it advantageously cannot come into contact with the freeform structure 50.The enclosure of the cladding structure 70 can be designed such that the cladding material 80 is preferably in contact with a structural element of the optical arrangement 10 comprising a solid material over at least 70%, particularly preferably at least 80%, in particular over at least 90%, 95% or 98% of its surface.

[0076] Figure 3 shows a schematic representation of a further, likewise preferred embodiment of the optical arrangement 10 according to the invention. Here, the cladding material 80 and the material 100 of the boundary structure 90 comprise the same or a similar polymer curable by UV exposure. The material 80, 100 and the UV exposure acting on the material 80, 100 are selected such that, upon UV exposure, only an outer region of the material 80, 100, also referred to as the "shell," cures, while an inner region of the cladding material 80, also referred to as the "core," remains liquid. Alternatively, the outer region of the material 80, 100 can have a higher viscoelasticity than the inner region of the cladding material 80. In this way, a harder shell can form, which can hold a liquid portion of the jacket material 80 in position in the core, thus in particular in the area around the free-form structure 50.This embodiment can be obtained in particular by using a strongly absorbing photoinitiator in the material 80, 100 in order to absorb the UV light for curing preferably within an externally determined distance of at most 100 pm, particularly preferably of at most 50 pm, whereby at a greater distance curing of the polymer around the freeform structure 50 inhibits and the freeform structure remains surrounded by liquid sheath material 80.

[0077] Figure 4 shows a schematic representation of a preferred embodiment of a method 200 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 3.

[0078] In a provision step 210 according to method step a), at least one component carrier 20 is provided.

[0079] In an attachment step 220 according to method step b), the at least one optical component 30, 31, which has at least one optical coupling point 40, 41, is attached to the component carrier 20.

[0080] In a connection step 230 according to method step c), the at least one optical freeform structure 50 is connected to the at least one optical coupling point 40, 41. The optical freeform structure 50 can preferably be produced by means of an additive nanofabrication process, particularly preferably by means of two-photon polymerization.

[0081] In an enclosing step 240 according to method step d), the optical freeform structure 50 is at least partially surrounded by the at least one cladding structure 70, wherein the cladding structure 70 comprises the at least one viscoelastic cladding material 80. According to the invention, the cladding material 80 is selected such that it has a storage modulus with a maximum value of 1000 kPa. Particularly preferably, the storage modulus can be at most a factor of 1000 greater than a loss modulus of the cladding material 80. If the cladding material 80 comprises at least one liquid, curable viscoelastic material, the at least one optical freeform structure 50 can be at least partially surrounded by the liquid, curable viscoelastic material, wherein the enclosing step 240 can comprise a curing step comprising at least partial curing of the liquid, curable viscoelastic material.

[0082] In a production step 250 according to method step e), at least one boundary structure 90 is produced such that the boundary structure 90 and the optical component 30 form an at least partial enclosure for the cladding structure 70. In the preferred embodiments according to Figures 1 to 3, the component carrier 20 also contributes to the enclosure of the cladding structure 70. As schematically shown in Figures 1 and 2, the boundary structure 90 can be produced by attaching the boundary structure 90 to the cladding structure 70. According to the embodiment according to Figure 3, the boundary structure can be produced by treating the shell of the cladding structure 70, while the viscoelastic cladding material remains in the core of the cladding structure 70.

[0083] For further details on Figures 2 to 4, please refer to the above description of Figure 1. List of reference symbols

[0084] 10 optical arrangement

[0085] 20 component carriers

[0086] 30, 31 optical component

[0087] 40, 41 optical coupling point

[0088] 50 freeform structure

[0089] 60 Material (of the freeform structure)

[0090] 70 Sheath structure at least one

[0091] 80 (vi scoelastic) sheath material

[0092] 90 Boundary structure

[0093] 100 Material of the (boundary structure)

[0094] 110 gas volume

[0095] 200 Method for producing an optical arrangement

[0096] 210 Deployment step

[0097] 220 installation steps

[0098] 230 Connection step

[0099] 240 environmental step

[0100] 250 application steps

Claims

Patent claims 1. Optical arrangement (10), comprising - at least one component carrier (20); - at least one optical component (30, 31) mounted on the component carrier (20), wherein the optical component (30, 31) has at least one optical coupling point (40, 41); - at least one optical freeform structure (50) connected to the optical coupling point (40, 41); - at least one cladding structure (70) which surrounds the optical freeform structure (50) at least in regions, wherein the cladding structure (70) comprises at least one viscoelastic cladding material (80); - at least one boundary structure (90), wherein the boundary structure (90) and the at least one optical component (30, 31) form an at least partial enclosure for the cladding structure (70), wherein the cladding material (80) has a storage modulus having a maximum value of 1000 kPa.

2. Optical arrangement (10) according to the preceding claim, wherein the storage modulus is at most a factor of 1000 greater than a loss modulus of the cladding material (80).

3. Optical arrangement (10) according to the preceding claim, wherein the storage modulus is at most a factor of 100 greater than the loss modulus of the cladding material (80), and wherein the storage modulus has a maximum value of 100 kPa.

4. Optical arrangement (10) according to one of the preceding claims, wherein a value for the storage modulus is set such that, within ambient conditions set for use of the optical arrangement (10), the cladding material (80) substantially retains its spatial position and shape and continues to surround at least the free-form structure (50) at least in regions.

5. Optical arrangement (10) according to one of the preceding claims, wherein - the storage modulus has a value of 0.1 kPa to 60 kPa, preferably 1 kPa to 30 kPa, particularly preferably 2 kPa to 15 kPa; and - the loss modulus has a value of 0.01 kPa to 30 kPa, preferably 0.05 kPa to 10 kPa, particularly preferably 0.1 kPa to 5 kPa.

6. Optical arrangement (10) according to one of the preceding claims, wherein a value is set for a shear modulus of the cladding material (80) such that, in the case of a local relative movement between the cladding structure (70) and the free-form structure (50) within environmental conditions which are set for use of the arrangement (10), a shear stress of the cladding material (80) surrounding the free-form structure (50) is so low that the free-form structure (50) essentially retains its spatial position and shape.

7. Optical arrangement (10) according to one of the preceding claims, wherein the cladding material (80) comprises at least one liquid, locally curable polymer, and a cured cladding material (80) forms at least part of the boundary structure (90).

8. Optical arrangement (10) according to one of the preceding claims, wherein a region around the free-form structure (50) which corresponds to at least twice the value of the diameter of the free-form structure (50), which preferably assumes a value of at least 4 pm, comprises at least one liquid viscoelastic material.

9. Optical arrangement (10) according to the preceding claim, wherein the liquid viscoelastic material has a viscosity of 1 cm 2 / s up to 1,000,000 cm 2 / s.

10. Optical arrangement (10) according to one of the preceding claims, wherein the limiting structure (90) is arranged such that when a volume of the cladding structure (70) changes, a pressure inside the cladding structure (70) remains substantially constant.

11. Optical arrangement (10) according to one of the preceding claims, wherein the boundary structure (90) at least partially comprises the cladding material (80).

12. Optical arrangement (10) according to one of the preceding claims, wherein the limiting structure (90) comprises an elastic material.

13. Optical arrangement (10) according to one of the preceding claims, wherein the at least partial enclosure for the cladding structure (70) comprises a closed volume (110) which is not completely filled by the cladding material (80).

14. Optical arrangement (10) according to one of the preceding claims, wherein the cladding material (80) and a material (60) comprised by the freeform structure (50) are optically transparent, wherein the cladding material (80) has a lower refractive index than the material (60) comprised by the freeform structure (50).

15. Optical arrangement (10) according to one of the preceding claims, further comprising - at least one opening in the at least partial enclosure for the casing structure (70), wherein the opening is designed for pressure equalization.

16. 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); b) attaching at least one optical component (30, 31) having at least one optical coupling point (40, 41) to the component carrier (20); c) connecting at least one optical freeform structure (50) to the at least one optical coupling point (40, 41); d) at least partially surrounding the optical freeform structure (50) with at least one cladding structure (70), wherein the cladding structure (70) comprises at least one viscoelastic cladding material (80);e) producing at least one boundary structure (90) such that the boundary structure (90) and the optical component (30) form an at least partial enclosure for the cladding structure (70), wherein the cladding material (80) is selected such that it has a storage modulus having a maximum value of 1000 kPa; 17. The method (310) according to the preceding claim, wherein the cladding material (80) is selected such that the storage modulus is at most a factor of 1000 greater than a loss modulus of the cladding material (80).

18. Method (310) according to any preceding method claim, wherein the optical freeform structure (50) is produced by means of an additive nanofabrication process, particularly preferably by means of two-photon polymerization.

19. Method (310) according to any preceding method claim, wherein at least one liquid, viscoelastic material is selected for the cladding material (80), wherein the at least one optical freeform structure (50) is at least partially surrounded by the liquid, viscoelastic material (80), and wherein the liquid viscoelastic material has a viscosity of 1 cm 2 / s up to 1,000,000 cm 2 / s.

20. Method (310) according to the preceding claim, wherein the liquid, curable viscoelastic material is at least partially cured, preferably site-selectively, in a curing step.

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