Apparatus, test card and method for testing a photonic integrated circuit, and a photonic integrated circuit

Abstract

An apparatus and test card for testing photonic integrated circuits, a corresponding system, and a photonic integrated circuit are provided, where a test card (24) is imaged by an optical unit (20) onto a photonic integrated circuit (22) to be tested, in such a way that parallel illumination of the photonic integrated circuit (22) at multiple different locations is possible.

Description

[Technical field]

[0001] This application claims priority to German Patent Application No. 102022103611.1, filed on February 16, 2023, entitled “Apparatuses, test cards and methods for testing photonic integrated circuits, and photonic integrated circuits”, which is incorporated by reference in its entirety for all purposes.

[0002] The present application relates to apparatus, test cards and methods for testing photonic integrated circuits (PICs), as well as photonic integrated circuits configured for such testing. [Background technology]

[0003] In photonic integrated circuits, as in electronic integrated circuits, multiple passive and / or active optical and optoelectronic components are assembled on a common substrate, for example a semiconductor wafer, to form complex optical circuits. In this case, conventional optical components, such as filters or couplers, can be replaced by more compact integrated optical components. The various components of the photonic integrated circuit are connected to each other via waveguides in the photonic integrated circuit. Such photonic integrated circuits have become more and more interesting in recent years, especially due to the significant increase in data traffic on the Internet, since here signal processing circuits with sufficient bandwidth and operating efficiently are required. Apart from telecommunications and data transmission applications, photonic integrated circuits are also of interest for other applications, such as, for example, sensor technology and applications in life sciences.

[0004] The production process of such photonic integrated circuits is similar to that of conventional electronic integrated circuits or microelectromechanical systems (MEMS). However, in contrast to these conventional technologies, for photonic integrated circuits, there are only a few test methods that can be used to efficiently check such circuits during or after the production process.

[0005] In order to test a photonic integrated circuit, and in particular a waveguiding structure located therein, it is necessary to couple light into the waveguiding structure of the photonic integrated circuit and detect light from the photonic integrated circuit, in particular from the waveguiding structure, or both.

[0006] One conventional method for testing such photonic integrated circuits is to use optical waveguide fibers, i.e., optical fibers or other dielectric optical waveguides, which are aligned and positioned on the photonic integrated circuit to be tested. By using these optical waveguide fibers, the photonic integrated circuit to be tested is illuminated at the corresponding input coupling point, and the light emerging from the photonic integrated circuit is collected and then evaluated. This requires a very high positioning accuracy within the range of less than 1 μm, which requires a relatively long time for positioning purposes and is therefore only suitable for a limited range for a large number of items.

[0007] To solve this problem, DE102017101626A1 filed by the applicant provides an apparatus for testing photonic integrated circuits, in which a light beam is directed onto the circuit to be tested by using a scanning device. This eliminates the need for complex positioning of the optical waveguide fiber. However, a movable and correspondingly precise scanning mirror is then required. Summary of the Invention

[0008] Therefore, there is a need for further possibilities for efficiently testing photonic integrated circuits.

[0009] There is provided an apparatus according to claim 1, a test card according to claim 5 or 12, a system according to claim 13, a photonic integrated circuit according to claim 15 or 19, and a method according to claim 20. The dependent claims define further embodiments.

[0010] According to one aspect, there is provided an apparatus for testing a photonic integrated circuit, comprising: a receptacle for a test card having a plurality of optical ports; an optical unit for imaging the test card onto the photonic integrated circuit to be tested; An apparatus is provided comprising:

[0011] By using the optical unit, the light coming out of the test card can be imaged to a corresponding illuminated point of one or more photonic integrated circuits, so that the photonic integrated circuits can be illuminated at multiple points for testing purposes. Conversely, the light from the photonic integrated circuits can be received in a corresponding manner. Such an optical unit can be embodied, for example, as a microscope optical unit, in a manner known per se. The optical unit can perform demagnification or magnification imaging. The test card can then be larger or smaller (scaled) than the photonic integrated circuits to be tested. The optical port can be an optical inlet or outlet, or a function of such.

[0012] The apparatus may further comprise a receptacle for a further test card having an optical inlet, the optical unit comprising a splitter element configured to pass light from the test card to the photonic integrated circuit and to pass light from the photonic integrated circuit to the further test card.

[0013] In this regard, separate test cards can be used for illumination and detection.

[0014] The splitter element may include a polarizing beam splitter, which allows the illumination light beam and the detection light beam to be separated with relatively little loss.

[0015] The apparatus may further include a scanner device in the optical path from the receptacle to the photonic integrated circuit, which may be used, for example, to sequentially scan a plurality of photonic integrated circuits on a wafer.

[0016] According to a further aspect, there is provided a test card for testing a photonic integrated circuit, the test card comprising a plurality of light outlets for illuminating the photonic integrated circuit, the light outlets being arranged to correspond to locations on the photonic integrated circuit that are to be illuminated for testing purposes.

[0017] Such a test card and the above mentioned device make it possible to test the respective photonic integrated circuit in a simple manner.

[0018] The test card may further comprise a light source connected to the optical outlet via at least one optical fiber. In this connection, the photonic integrated circuit to be tested may be illuminated by light from the light source. In this case, the term "light source" also encompasses an arrangement having a plurality of individual light sources, for example light emitting diodes, connected to a respective assigned optical outlet by a respective assigned optical fiber.

[0019] In one variant, the light outlet may correspond to the end of at least one optical fiber, which end may then still be connected to an attachment optical unit.

[0020] In another variant, the test card comprises a photonic integrated circuit, in which it is possible to integrate various components for testing purposes.

[0021] Additionally or alternatively, the test card may comprise an electro-optical circuit board.Thus, various possibilities of implementation exist.

[0022] The light outlet can be configured to output polarized light, for example by embodiment as a grating coupler, such a test card then being usable in particular in conjunction with the above mentioned use of polarizing beam splitters.

[0023] The test card may further comprise a plurality of light inlets for receiving light from the photonic integrated circuit, the light inlets being arranged to correspond to light emitting locations of the photonic integrated circuit that emit light during testing of the photonic integrated circuit, such that such a test card may be used for both illumination and detection purposes.

[0024] According to a further aspect, there is provided a test card for testing a photonic integrated circuit, further comprising a plurality of light inlets for receiving light from the photonic integrated circuit, the light inlets being arranged to correspond to light emitting locations of the photonic integrated circuit that emit light during testing of the photonic integrated circuit. Such a test card can in particular be used as a further test card in the above mentioned device having a splitter element.

[0025] According to a further aspect, there is provided a system for testing a photonic integrated circuit, comprising an apparatus as described above and a test card as described above, said test card being received in a receptacle.

[0026] The system may further comprise a circuit board, the circuit board configured to contact the photonic integrated circuit; The circuit board includes at least one conductor track extending between the front surface of the circuit board and the back surface of the circuit board and configured to contact an electrical interface of a photonic integrated circuit positioned adjacent the back surface.

[0027] In this connection, electrical contacting of the photonic integrated circuit to be tested can additionally be performed.

[0028] The circuit board may be an electro-optical circuit board, which additionally includes at least one optical beam path extending between a front surface of the electro-optical circuit board and a back surface of the electro-optical circuit board and configured to contact an optical interface of a photonic integrated circuit positioned adjacent the back surface.

[0029] According to a further aspect, there is provided a photonic integrated circuit comprising a test structure having an input coupling element for coupling in light having a first polarization and an output coupling element for coupling out light having a second polarization different from the first polarization, the input coupling element and the output coupling element being optically connected to the photonic integrated circuit. Such a photonic integrated circuit can be tested by an apparatus as described above using a polarizing beam splitter.

[0030] The photonic integrated circuit may further comprise sawing lines between the input and output coupling elements on the one hand and the photonic integrated circuit on the other hand. After testing, separation may then be performed along the sawing lines, resulting in an edge coupler, and the photonic integrated circuit may then be delivered for its use.

[0031] The input coupling elements and the output coupling elements can be formed as a common element, which allows space to be saved.

[0032] The photonic integrated circuit may further comprise at least one combined input / output coupling element for alignment purposes, optically shorted with the waveguide.

[0033] This is also possible independently of the test structure mentioned above, so that according to a further aspect, a photonic integrated circuit is provided, further comprising at least one combined input / output coupling element for alignment purposes, optically shorted with the waveguide, such a shorted input / output coupling element making it possible to facilitate alignment of the test card in the above mentioned system.

[0034] According to a further aspect, there is provided a method for testing a photonic integrated circuit using the apparatus described above, comprising the steps of: Inserting the test card described above into a receptacle; Aligning the test card (e.g., using shorting input / output coupling elements); Testing the photonic integrated circuit by using the test card, i.e. by illuminating with the test card and detecting light exiting the photonic integrated circuit by using the test card or a further test card. A method is provided, comprising:

[0035] Various exemplary embodiments will now be described with reference to the accompanying drawings. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a block diagram of a system according to an exemplary embodiment. [Diagram 2] FIG. 1 is a diagram of a system according to an exemplary embodiment. [Figure 3A] 1A-1C illustrate test cards according to different exemplary embodiments; [Figure 3B]1A-1C illustrate test cards according to different exemplary embodiments; [Figure 4A] FIG. 1 is a diagram to demonstrate polarization-based separation, according to some example embodiments. [Figure 4B] FIG. 4B illustrates a modification of FIG. 4A. [Diagram 5] FIG. 1 illustrates a system according to an exemplary embodiment. [Figure 6] FIG. 1 illustrates a system according to a further exemplary embodiment. [Figure 7] 1A-1C illustrate the provision of test structures for some exemplary embodiments of photonic integrated circuits. [Figure 8] 1A-1C illustrate the provision of alignment structures for some exemplary embodiments of photonic integrated circuits. [Figure 9] FIG. 1 is a flow diagram illustrating a method for testing a photonic integrated circuit using the system described above. [Figure 10] FIG. 13 is a block diagram of a further system having an additional electro-optical circuit board according to an illustrative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Various exemplary embodiments are described in detail below. These exemplary embodiments are provided by way of example only and should not be construed as limiting.

[0038] Features (e.g., components, method steps, elements, etc.) of different exemplary embodiments can be combined with each other, even if this is not explicitly indicated. Variations, modifications and details described for one of the exemplary embodiments are also applicable to other exemplary embodiments and therefore will not be described repeatedly. In addition to the features explicitly illustrated and described, other features may also be provided, in particular features of conventional devices for testing photonic integrated circuits and corresponding photonic integrated circuits. Such conventional features will not be described explicitly.

[0039] FIG. 1 shows a system for testing a photonic integrated circuit 12 according to one exemplary embodiment. The system of FIG. 1 comprises an optical unit 11 and a test card 10 coordinated with the photonic integrated circuit 12 to be tested. The optical unit 11 images the test card 10 onto the photonic integrated circuit 12. In this case, the test card 10 comprises an optical outlet, an optical inlet, or both, i.e., optical ports, as indicated by the arrow 13. These are imaged by the optical unit 11 onto the photonic integrated circuit 12, so that the latter is illuminated at a point corresponding to the optical outlet of the test card 10 and / or the test card 10 correspondingly receives at the optical inlet light emitted by the photonic integrated circuit 12 in response to illumination, as also indicated by the arrow 14. In other words, the test card 10 and the photonic integrated circuit 12 are arranged in the object plane and the assigned image plane of the optical unit 11. In this case, a corresponding mount 15 or other receptacle can be provided for the test card 10. The receptacle may be alignable, for example by micrometer screw gauges, piezoelectric elements, etc., to allow precise positioning of the test card 10. By providing such a receptacle, a corresponding test card for a type of photonic integrated circuit to be tested can be inserted in each case into the system of FIG. 1. In other exemplary embodiments, the test card is fixedly (non-replaceably) installed in the receptacle. In this case, only one type of photonic integrated circuit can be tested.

[0040] Here, the test card 10 can in particular comprise a number of light outlets at a number of locations, so that the photonic integrated circuit 12 can be illuminated at a number of points simultaneously. Conversely, light from a number of points on the photonic integrated circuit 12 can also be received simultaneously at various light inlets and then evaluated correspondingly. As a result, according to the dimensioning of the optical unit 11 and the test card 10, a simultaneous test of correspondingly sized areas on the photonic integrated circuit 12 is possible. By way of example, if the test card 10 is of a corresponding size and the optical unit 11 is correspondingly dimensioned, the entire photonic integrated circuit 12 can be tested in parallel, or multiple photonic integrated circuits arranged on a wafer can also be tested in parallel. However, the photonic integrated circuit 12 can also be movable, for example arranged on a sample stage, so that multiple partial areas of the same type, for example multiple photonic integrated circuits, arranged together on a wafer, can be tested in succession.

[0041] The assessment itself can then be carried out in any conventional manner.Detailed implementations of systems such as that of Figure 1 will now be described with reference to the following drawings.

[0042] Fig. 2 shows a system according to a further exemplary embodiment. The system of Fig. 2 comprises a measurement unit 28, a microscope 20 and a movable sample stage 210. A wafer 29 with a photonic integrated circuit 22 to be tested is placed on the sample stage 210. The measurement unit 28 comprises a test card 24 which may correspond to the test card 10 already discussed with reference to Fig. 1 and which, like the test card, may be placed in a corresponding mount. The test card 24 comprises a number of input / output coupling elements 25 as examples of light outlets and light inlets. An example of the structure of the test card 24 is explained further in more detail below with reference to Figs. 3A and 3B. Furthermore, the measurement unit 28 comprises a light source 27 and a detector 26. The light source 27 is connected to an output coupling element of the input / output coupling element 25, so that light is emitted by the test card 24 at the corresponding output coupling element. The detector 26 is connected to an input coupling element of the input / output coupling element 25 and receives the light leaving the photonic integrated circuit 22.

[0043] For this purpose, the microscope 20 images the test card 24, in particular its input / output coupling elements 25, onto corresponding input / output coupling elements 25 of the photonic integrated circuit 22 by using a corresponding microscope optical unit. The input / output coupling elements 23 of the photonic integrated circuit 22 can be, for example, grating couplers or other input / output coupling elements conventionally used in photonic integrated circuits, in particular for testing purposes. They can also be input / output coupling elements 23 used here in particular for testing the photonic integrated circuit 22, while in the subsequent normal operation of the photonic integrated circuit 22 other input / output coupling elements are used for in-coupling and out-coupling light.

[0044] In this way, light can be simultaneously provided from multiple output coupling elements from among the input / output coupling elements 25 to corresponding input coupling elements 23 of the photonic integrated circuit, and correspondingly emitted light can be received in response from the output coupling elements 23 by the photonic integrated circuit and evaluated by using the detector 26, where the detector 26 shall be considered to represent any type of detector and evaluation circuitry coupled thereto. The evaluation can be performed, for example, according to the presence or intensity of a received light beam or can include more complex measurement methods such as optical time domain reflectometry or optical frequency domain reflectometry, which allow the localization of disturbances along the propagation path of the light through the photonic integrated circuit 22.

[0045] Optionally, the microscope 20 can include a scanning unit 21 similar to the scanning unit described in DE 102017101626 A1 cited in the introduction. In this connection, for example, precise alignment of the imaging by using the microscope 20 can be performed, i.e. the input / output coupling element 25 can be aligned with the input / output coupling element 23. By moving the movable stage 210 and / or using the scanning unit 21, it is then possible to successively test, for example, a number of photonic integrated circuits 22 on a wafer 29.

[0046] In some exemplary embodiments, the test card 24 is the same size as the photonic integrated circuit 22. In other embodiments, the test card can be larger or smaller than the photonic integrated circuit 22 and scaled relative to the photonic integrated circuit 22, with the microscope 20 then ensuring a corresponding magnification or demagnification imaging. For example, as a result of a larger realization of the test card 24, more construction space is available and as a result of the scaling, larger manufacturing tolerances are allowed, and therefore the test card 24 can be imaged on the photonic integrated circuit 22 in a correspondingly reduced manner by using the microscope 20, making the production of the test card 24 easier. In yet other exemplary embodiments, the test card 24 can also have a topology, such as a curvature, to compensate for distortions of an optical unit such as the microscope 20. Finally, any embodiment of the test card 24 and the microscope 20 is possible in which the input / output coupling element 25 is imaged on the input / output coupling element 23, or vice versa, such that the desired illumination of the photonic integrated circuit 22 is performed and / or light from the photonic integrated circuit is detected.

[0047] Various embodiments of the test card 24 will now be described with reference to Figures 3A and 3B.

[0048] 3A shows a test card 24A constructed by using an optical fiber 30. The fiber end of the optical fiber 30 on the test card 24A constitutes the input / output coupling element 25 of FIG. 2. To form the input / output coupling element 25 in this manner, a miniaturized attachment optical unit can be additionally applied to the fiber end.

[0049] On the side facing away from the microscope 20, any fiber-coupled measurement system can then be connected, an example being a detector 26. In the case of Fig. 3A, high positioning accuracy and stability of the fiber end can be achieved, for example, by using V-shaped depressions or ferrules in a corresponding material such as ceramic, hard metal or suitable plastic. The fibers can be arranged in rows or in a two-dimensional matrix.

[0050] FIG. 3B shows a test card 24B, which itself can be constructed as a photonic integrated circuit or an electro-optical circuit board. An electro-optical circuit board is described, for example, in DE102018108283A1. When embodied as a photonic integrated circuit, the optical fiber 30 can be connected by using a grating coupler or an edge coupler. In the exemplary embodiment of FIG. 3A, a further measurement system can then be connected. Such a grating or edge coupler can in particular be arranged on the side of the test card 24B facing away from the sample. The input / output coupling element 25 facing the microscope 20 and thus the sample 22 can likewise be realized as a grating or edge coupler. In the same way, when the test card 24B is embodied as an electro-optical circuit board, the optical fiber 30 can be connected by a prism or an edge coupler. The sample-side coupling element 25 can also be realized by a prism or an edge coupler.

[0051] 3B, further functions such as light sources, detectors, modulators and spectrometers may also be realized in test card 24B, which is realized as a photonic integrated circuit or electro-optical circuit board, such that part or the entire measurement system is realized in test card 24B itself. In other words, detector 26 and / or light source 27 may also be realized directly in test card 24B, without the need for coupling by optical fiber 30.

[0052] In the case of the exemplary embodiment described above, the light entering the photonic integrated circuit is spatially separated from the light exiting the photonic integrated circuit, thus achieving a separation between illumination and measurement. In other words, the light is emitted by the test card 24 at a different input / output coupling element than the one at which the light is received. Additionally or alternatively, a separation based on polarization can be performed. This is explained with reference to Figures 4 to 6.

[0053] In the case of photonic integrated circuits, polarization sensitivity can generally be obtained by using grating couplers aligned in the corresponding direction. Figure 4A shows a corresponding example.

[0054] FIG. 4A shows a photonic integrated circuit 40 to be tested (DUT, device under test) connected via a waveguide to an input coupling grating 43 and an output coupling grating 41. The input coupling grating 43 and the output coupling grating 41 can be specific test structures used only for testing the photonic integrated circuit. Such structures can be arranged on a wafer on which the photonic integrated circuit 40 is formed and which can be partially separated after testing, for example along a sawing line 46. The two edge couplers of the photonic integrated circuit 40 then arise at the edges of the waveguides at the sawing line. In this case, compared to the grating coupler 41 used for output coupling, the grating coupler 43 used for input coupling of light has its gratings aligned in an orthogonal direction, so that the grating coupler 43 incouples light with a polarization according to the arrow 45, while the grating coupler 41 outcouples light with a polarization according to the arrow 46, i.e. perpendicular to the polarization of the light that is incoupled. Arrows 42 and 44 symbolize how light is guided from grating coupler 42 to photonic integrated circuit 40 and from photonic integrated circuit 40 to grating coupler 41 .

[0055] As shown in Fig. 4B, instead of the separate grating couplers 41, 43, a dual polarization grating coupler 47 can also be used. Fig. 4B otherwise corresponds to Fig. 4A. Thus, in Fig. 4B, as in Fig. 4A, two separate edge couplers are also available at the sawing line 46. That is, light can then be in-coupled and out-coupled at the edges.

[0056] FIG. 5 shows a system according to one exemplary embodiment using a photonic integrated circuit 22 with polarization-sensitive input and output couplings as described with reference to FIGS. 4A and 4B. FIG. 5 shows a system in which the corresponding polarization separation is realized in a microscope. The system of FIG. 5 comprises a first test card 24C, a second test card 24D and a microscope 20A for testing the photonic integrated circuit 22, in this case using separate polarizations for the input and output couplings at least for testing purposes, i.e. a corresponding test structure, as described with reference to FIGS. 4A and 4B. The test card 24C serves to transmit light from the light source 26, and the test card 24D serves to receive the light and detect it by using the detector 27. The light exiting the test card 24C passes a polarizing beam splitter 50 with a corresponding polarization into the photonic integrated circuit 22 and is then in-coupled by an input coupling grating, such as the input coupling grating 43 of FIG. 4A. In contrast, the light exiting the photonic integrated circuit 22 is directed through the polarizing beam splitter 50 to the test card 24D, where it is analyzed. Apart from the polarizing beam splitter 50, the microscope 20A corresponds to the microscope 20 of Fig. 2. Compared to a solution using a simple beam splitter without polarized light, a larger proportion of light now passes to the detector 27 and can be evaluated.

[0057] Apart from the polarization separation and the use of separate test cards and different polarizations, the exemplary embodiment of Fig. 5 corresponds to that of Fig. 2, and other details may be implemented as discussed with reference to Fig. 2. The test cards 24C, 24D may each be implemented as discussed with reference to Figs. 3A and 3B, where in the illustrated exemplary embodiment only components for emitting light (e.g., a light outlet) are implemented in the test card 24C and only components for receiving light (e.g., a light inlet) are implemented in the test card 24D. In other exemplary embodiments, one or both of the two test cards 24C, 24D may comprise components for emitting light and also components for receiving light.

[0058] Figure 6 shows an alternative system. Here, the microscope 20 corresponds to the microscope 20 of figure 2 and, in particular, in contrast to the microscope 20A of figure 5, does not comprise a polarizing beam splitter. The system of figure 6 further comprises a test card 24E. The test card 24E comprises input / output coupling elements, such as input / output coupling elements 61, through which both the in-coupling and the out-coupling of light takes place. These input / output coupling elements 61 are then connected to both the light source 27 and the detector 26 via a polarizing beam splitter 60. Thus, here, the beam splitting does not take place in the microscope 20 as in the case of figure 5, but in or downstream of the test card 24E.

[0059] As already mentioned, a plurality of photonic integrated circuits to be tested can be provided on a wafer. The coupling gratings connected thereto can be placed close together. An example is shown in FIG. 7. FIG. 7 has four photonic integrated circuits to be tested 40A-40C, which are connected to three dual polarization grating couplers 70a-70c via corresponding waveguides as shown. In this case, the dual polarization grating couplers 70a-70c correspond to the dual polarization grating coupler 47 of FIG. 4B. A similar configuration with separate input and output coupling grating couplers according to FIG. 4A is also possible.

[0060] As shown in FIG. 7, the dual polarization grating couplers 70a-70c are arranged close together. In this way, overall, only a relatively small chip area on the corresponding wafer is required for coupler A, and the corresponding test card is then embodied such that light is emitted onto and received from said couplers 70a-70c. After cutting along sawing lines 46, as explained with reference to FIG. 4A and FIG. 4B, two edge couplers are then available in each case for each of the photonic integrated circuits 40A-40C. Although one optical input and one optical output (either in combination as a dual polarization grating coupler or by separate grating couplers) are shown for each tested photonic integrated circuit in FIG. 4A and FIG. 4B and also in FIG. 7, in other embodiments it is also possible that two or more input coupling elements and / or two or more output coupling elements are assigned to one, several or all tested photonic integrated circuits.

[0061] As already briefly explained, for testing purposes, each test card (e.g., 24 in FIG. 2) or multiple test cards (e.g., 24C, 24D in FIG. 5) must be correctly aligned so that each photonic integrated circuit to be tested (e.g., 22) is illuminated in the correct place and light is collected from the correct place. To facilitate this alignment, in some exemplary embodiments, optical alignment markers can be used. A corresponding exemplary embodiment of a wafer or chip to be tested 80 having multiple photonic integrated circuits to be tested is shown in FIG. 8. In FIG. 8, four dual polarization grating couplers 81A-81D are provided, which are short-circuited with themselves by their respective waveguides, i.e. the incident light is directly emitted again with modified polarization. This can be tested correspondingly using the systems of Figures 5 and 6, i.e. it is possible to test whether light leaving test card 24E of Figure 6 or test card 24C of Figure 5 at points assigned to couplers 81A-81D is received at corresponding points (in that case the same points) of test card 24E of Figure 6 or test card 24D of Figure 5. In this case, two coupling elements 81A-81D are required for a two-dimensional configuration and three coupling elements are required for a three-dimensional configuration, it is also possible to provide more coupling elements, e.g. four coupling elements as shown in Figure 8.

[0062] Many variations of the above-described system are possible.

[0063] Instead of separating based on polarization, in other exemplary embodiments, separation by propagation direction, incoming or outgoing light, can also be performed if a circulator is used instead of a polarization splitter.

[0064] Additionally, a semi-transparent or foldable mirror may be conventionally provided within microscopes 20 and 20A to direct light from the photonic integrated circuit onto a camera, thus enabling an external image.

[0065] FIG. 9 shows a flow diagram illustrating a method for testing a photonic integrated circuit using the system described above.

[0066] In step 90, a test card, such as test card 10 of FIG. 1, test card 24 of FIG. 2, or one of the discussed test cards 24A-24E, is inserted into a corresponding device, such as microscope 20, 20A. If necessary, in step 91, the test card is then oriented and aligned, for example using coupling elements 81A-81D of FIG. 8. Each photonic integrated circuit is then tested by having light emitted therein and in response the light is measured, as previously described with reference to the device.

[0067] FIG. 10 illustrates a block diagram of a further system having an additional electro-optical circuit board according to one exemplary embodiment.

[0068] In order to provide electrical contacts in addition to the optical contacts of the photonic integrated circuit, an electro-optical circuit board (EOCB) can be arranged adjacent to the photonic integrated circuit (PIC). Such an electro-optical circuit board is described, for example, in the document DE102018108283A1.

[0069] The electro-optical circuit board may comprise at least one conductor track extending between a surface of the electro-optical circuit board and a back surface of the electro-optical circuit board and configured to contact an electrical interface of a photonic integrated circuit positioned adjacent the back surface, and may further comprise at least one optical beam path extending between a surface of the electro-optical circuit board and a back surface of the electro-optical circuit board and configured to contact an optical interface of a photonic integrated circuit positioned adjacent the back surface.

[0070] As can be seen in Fig. 10, the electro-optical circuit board can be disposed on the photonic integrated circuit, so that both electrical and optical signals can be passed by the electro-optical circuit board between the electro-optical circuit board and the photonic integrated circuit, as indicated by arrow 16. In this case, the optical unit 11 images the test card 10 onto the electro-optical circuit board, so that the electro-optical circuit board is illuminated at a point corresponding to the optical outlet of the test card 10, as indicated by arrow 14, and passes the optical signal to the photonic integrated circuit. Correspondingly, the electro-optical circuit board can receive light emitted by the photonic integrated circuit 12 in response to the illumination, and can pass the light to the optical unit 11 or the test card 15, also indicated by arrow 14. As a result, the electro-optical circuit board passes the optical signal between the test card 15 and the photonic integrated circuit 12, and additionally provides electrical contact of the photonic integrated circuit.

[0071] In a further exemplary embodiment, an electro-optical circuit board, or alternatively a purely electrical circuit board, can also be arranged on the opposite side of the photonic integrated circuit with respect to the optical unit 11. As a result, the photonic integrated circuit can be contacted purely optically on the side of the photonic integrated circuit facing the optical unit 11 and additionally purely electrically from the side of the photonic integrated circuit facing away from the optical unit 11. In this case, the electrical and optical contacting of the photonic integrated circuit can be performed as described in document DE102018108283A1.

[0072] By using an electro-optical circuit board, it is possible to contact the photonic integrated circuit in a particularly simple manner. By way of example, the topology of the back side of the electro-optical circuit board can be adapted to the topology of the photonic integrated circuit. This means that the lateral arrangement of the optical coupling points formed by at least one optical beam path is adapted to the topology of the optical interface of the photonic integrated circuit. In the case of a high integration density of the photonic integrated circuit, this can mean that the average distance between adjacent coupling points on the back side of the electro-optical circuit board is relatively small, for example in the range of micrometers. In particular, the average distance between the coupling points on the back side can be smaller than the average distance between the coupling points on the front side of the electro-optical circuit board. This can make it possible to automatically and particularly reliably generate optical contact with the photonic integrated circuit via the coupling points on the front side of the electro-optical circuit board, since only a relatively low positioning accuracy is required to image the test card onto the electro-optical circuit board according to the optical coupling points.

Claims

1. An apparatus for testing a photonic integrated circuit (12; 22; 40; 40A-40C), comprising: a receptacle for a test card (24; 24A-24E) having a plurality of optical ports (25, 61); an optical unit (11; 20; 20A) for imaging said test card (24; 24A-24E) onto a photonic integrated circuit (12; 22; 40; 40A-40C) to be tested; An apparatus comprising:

2. 2. The apparatus of claim 1, further comprising a receptacle for a further test card (24; 24A-24E) having an optical inlet (25), and wherein the optical unit (11; 20; 20A) comprises a splitter element (50) configured to pass light from a test card (24; 24A-24E) to the photonic integrated circuit (12; 22; 40; 40A-40C) and to pass light from the photonic integrated circuit (12; 22; 40; 40A-40C) to the further test card (24; 24A-24E).

3. The apparatus of claim 2 , wherein the splitter element (50) comprises a polarizing beam splitter.

4. An apparatus according to any preceding claim, further comprising a scanner device (21) in an optical path from the receptacle to the photonic integrated circuit (12; 22; 40; 40A-40C).

5. 1. A test card (10; 24; 24A-24E) for testing a photonic integrated circuit (12; 22; 40; 40A-40C), comprising a plurality of light outlets (25, 61) for illuminating the photonic integrated circuit (12; 22; 40; 40A-40C), the light outlets being arranged to correspond to locations on the photonic integrated circuit (12; 22; 40; 40A-40C) that are to be illuminated for testing purposes.

6. A test card (10; 24; 24A-24E) according to claim 5, further comprising a light source (26) connected to said light outlet (25, 61) via at least one optical fibre (30).

7. A test card (10; 24; 24A-24E) according to claim 6, wherein said light outlet (25, 61) corresponds to an end of said at least one optical fibre (30).

8. A test card (10; 24; 24A-24E) according to claim 5 or 6, wherein the test card (10; 24; 24A-24E) comprises a photonic integrated circuit (12; 22; 40; 40A-40C).

9. A test card (10; 24; 24A-24E) according to any one of claims 5 to 8, wherein the test card comprises an electro-optical circuit board.

10. A test card (10; 24; 24A-24E) according to any one of claims 5 to 9, wherein the light outlet (25, 61) is adapted to output polarised light.

11. A test card as claimed in any one of claims 5 to 10, further comprising a plurality of optical inlets (25, 61) for receiving light from the photonic integrated circuit (12; 22; 40; 40A-40C), arranged to correspond to light emitting locations of the photonic integrated circuit (12; 22; 40; 40A-40C) that emit light during testing of the photonic integrated circuit (12; 22; 40; 40A-40C).

12. 1. A test card (10; 24; 24A-24E) for testing a photonic integrated circuit (12; 22; 40; 40A-40C), comprising a plurality of optical inlets (25, 61) for receiving light from the photonic integrated circuit (12; 22; 40; 40A-40C), the optical inlets (25, 61) being arranged to correspond to light emitting locations of the photonic integrated circuit (12; 22; 40; 40A-40C) that emit light during testing of the photonic integrated circuit (12; 22; 40; 40A-40C).

13. A system for testing a photonic integrated circuit (12; 22; 40; 40A-40C), comprising an apparatus according to any one of claims 1 to 4 and a test card (10; 24; 24A-24E) according to any one of claims 5 to 12, said test card being received in a receptacle.

14. The system of claim 13, wherein the apparatus is embodied according to claim 2 and the system comprises a test card (10; 24; 24A-24E) according to claim 11, the test card being received in the further receptacle.

15. a circuit board configured to contact the photonic integrated circuit (12; 22; 40; 40A-40C); 15. The system of claim 13, further comprising at least one conductor track extending between a front surface of the circuit board and a rear surface of the circuit board and configured to contact an electrical interface of the photonic integrated circuit (12; 22; 40; 40A-40C) positioned adjacent to the rear surface.

16. A photonic integrated circuit (12; 22; 40; 40A-40C) comprising a test structure having an input coupling element (41; 70) for coupling in light having a first polarization and an output coupling element (41; 47) for coupling out light having a second polarization different from the first polarization, the input coupling element and the output coupling element being optically connected to the photonic integrated circuit (12; 22; 40; 40A-40C).

17. The photonic integrated circuit (12; 22; 40; 40A-40C) of claim 16, further comprising a sawing line (46) between the input coupling element (41; 70) and the output coupling element on the one hand and the photonic integrated circuit (12; 22; 40; 40A-40C) on the other hand.

18. A photonic integrated circuit (12; 22; 40; 40A-40C) according to any of claims 16 and 17, wherein the input coupling element and the output coupling element are formed as a common element (47).

19. A photonic integrated circuit (12; 22; 40; 40A-40C) according to any of claims 16 to 18, further comprising at least one combined input / output coupling element for alignment purposes, optically shorted with the waveguide.

20. A photonic integrated circuit (12; 22; 40; 40A-40C) comprising at least one combined input / output coupling element for alignment purposes, optically shorted with a waveguide.

21. A method for testing a photonic integrated circuit (12; 22; 40; 40A-40C) using an apparatus according to any one of claims 1 to 4, comprising: Inserting a test card (10; 24; 24A-24E) according to any one of claims 5 to 12 into a receptacle; aligning said test card (10; 24; 24A-24E); testing said photonic integrated circuits (12; 22; 40; 40A-40C) by using said test cards (10; 24; 24A-24E); A method comprising:

Images