Sensor device for magnetic field measurement using optical magnetic resonance measurement

Description

[0001] The present invention relates to a sensor device for magnetic field measurement by means of optical magnetic resonance measurement (ODMR), comprising a diamond having a plurality of color centers, in particular nitrogen vacancies, a laser emitter, a first photodetector and a circuit board, wherein the laser emitter is designed to excite the fluorescence of the color centers in the diamond, wherein the first photodetector is designed to receive fluorescence radiation from the color centers of the diamond. State of the art

[0002] Negatively charged nitrogen vacancy centers—i.e., a color center consisting of a substitute nitrogen atom in the diamond lattice and a directly adjacent vacancy in the lattice—in a diamond can be used for highly sensitive measurements of magnetic fields, electric fields, mechanical stresses, and temperatures. Such quantum technologies offer decisive advantages over classical sensor principles. These advantages include ultrahigh sensitivities, the possibility of vector magnetometry (determination of the direction of the magnetic field), and a large linear measurement range (Zeeman effect). Furthermore, no degradation occurs because color centers are stable or do not bleach, and the measurement is based on quantum mechanical states. To read out a sensor based on nitrogen vacancy centers, the magnetic resonance of the ground state triplet is optically detected (ODMR - optically detected magnetic resonance).To do this, the nitrogen vacancy center must be excited with green light. The red-shifted fluorescence light exhibits a characteristic dip in the energy position of the electron spin resonance. Due to the Zeeman effect, this position is linearly dependent on the magnetic field at the location of the nitrogen vacancy center. Since the nitrogen vacancy center in single-crystal diamond has four possible orientations within the crystal lattice, the presence of a directed magnetic field causes the nitrogen vacancy centers present in the crystal to react with varying strengths to the external magnetic field depending on their position within the crystal. This means that the projection of the magnetic field onto the nitrogen vacancy axis varies in size. As a result, at most four corresponding pairs of fluorescence minima can appear in the spectrum, from whose shape and position relative to each other, the magnitude and direction of the magnetic field can be unambiguously determined.

[0003] In order to obtain vector information even with weak external magnetic fields, suitable technical measures must be taken to ensure that the contributions of all four possible nitrogen vacancy orientations in the diamond crystal can be distinguished in the ODMR spectrum, even without an external magnetic field acting on the sensor. This can be achieved using a static bias magnetic field, which is provided within the sensor by appropriate technical measures. The bias magnetic field must have as homogeneous a field strength as possible within the sensitive diamond volume, since inhomogeneities in the bias magnetic field impair the sensitivity of the sensor. The strength of the bias magnetic field should be between 100 µT and 10 mT, ideally approximately 1 mT, to effectively split the four nitrogen vacancy orientations. The bias field must not deviate from the target value by more than 1 ‰ within the diamond volume.The bias field can be generated by permanent magnets or by current-carrying coils.

[0004] To achieve a sensitivity of < 1 pT / √ Hz To achieve this, it is necessary to optically pump the nitrogen vacancies in the diamond with approximately 1% of the saturation power density at 100 kW / cm². Laser emitters are used to achieve such intensities.

[0005] In conventional sensor devices for magnetic field measurement using optical magnetic resonance (MRI), this laser emitter is a separate component, and the light is guided to the diamond either via free-space optics or through an optical fiber. Therefore, conventional sensor devices for magnetic field measurement require a large installation space, which limits the potential fields of application. Furthermore, the separate laser emitter significantly increases manufacturing costs, making it impossible to address applications with significant cost pressure.

[0006] From DE 10 2018 214 617 A1, the applicant discloses a sensor device comprising a crystal body, in particular a diamond, with a number of color centers, in particular nitrogen vacancies, a light source for irradiating the crystal body with visible light, a high-frequency device for irradiating the crystal body with microwaves, and a photodetector. The photodetector is configured to detect fluorescent light generated due to the irradiation of the crystal body by the visible light and the microwaves. The sensor device comprises a gradient refractive index lens arranged between the crystal body and the photodetector, a light guide arranged between the crystal body and the photodetector, and / or a mirror at least partially surrounding the light source for visible light, and / or at least one filter layer covering part of a surface of the crystal body.

[0007] A sensor device according to the preamble of claim 1 is disclosed in Stürner, Felix M. et al.: "Compact integrated magnetometer based on nitrogen-vacancy centers in diamond," Diamond and Related Materials, Vol. 93, January 17, 2019, pages 59-65. Another such sensor device is known from Stürner, Felix M. et al.: "Integrated and Portable Magnetometer Based on Nitrogen-Vacancy Ensembles in Diamond," Advanced Quantum Technologies, Vol. 4, No. 4, February 10, 2021, page 2000111. The sensor device disclosed therein comprises a sensor head and two photodiodes, with Helmholtz coils being used for spectral splitting of the four NV orientations. Disclosure of the invention

[0008] The present invention is based on the object of providing a sensor device for magnetic field measurement by means of optical magnetic resonance measurement, which has a reduced size and reduced manufacturing costs compared to known devices.

[0009] To achieve the object underlying the invention, a sensor device for magnetic field measurement by means of optical magnetic resonance measurement (ODMR) according to claim 1 is proposed, comprising a diamond with a plurality of color centers, in particular nitrogen vacancies, a laser emitter, a first photodetector and a circuit board, wherein the laser emitter is designed to excite the fluorescence of the color centers in the diamond, wherein the first photodetector is designed to receive fluorescence radiation from the color centers of the diamond, wherein it is provided that the circuit board has several layers comprising at least one inner layer, that the laser emitter is arranged on a top side of the circuit board, that the first photodetector is arranged on a bottom side of the circuit board, that the diamond is arranged inside the circuit board in the plane of extension of the at least one inner layer,and that at least one of the layers has current-carrying structures which are designed to generate a magnetic field oriented perpendicular to the layers of the circuit board, homogeneous and penetrating the diamond.

[0010] In the context of the present invention, the terms "nitrogen vacancy", "nitrogen vacancy center" and "NV center" are used synonymously and can be interchanged.

[0011] The color centers, especially the nitrogen vacancy centers and / or the NV centers, are preferably negatively charged.

[0012] The physical principle of magnetic field measurement by means of optical magnetic resonance measurement (ODMR), for which the sensor device according to the invention is suitable, is known to the person skilled in the art and will not be explained in more detail here.

[0013] The circuit board of the sensor device according to the invention has multiple layers. This means, in particular, that the circuit board is formed from multiple layers of a substrate, each layer of which can have electrically conductive structures. The planes of extension of the layers are parallel to one another, and the layers are arranged at a distance from one another in direct physical contact and connected to one another.

[0014] The circuit board has at least one inner layer. Accordingly, the circuit board has at least three layers. The diamond of the sensor device is arranged in the extension plane of the at least one inner layer. For this purpose, a corresponding recess can be provided in the at least one inner layer. In the direction perpendicular to the extension plane of the inner layer, the diamond can protrude beyond the inner layer, such that the diamond is at least partially arranged in other inner layers of the circuit board, if present. Since the diamond is arranged inside the circuit board in the extension plane of the at least one inner layer, the inner layer encompasses the diamond.

[0015] According to the invention, it is now provided that at least one of the layers has current-carrying structures which are designed to generate a homogeneous magnetic field oriented perpendicular to the layers of the circuit board and penetrating the diamond.

[0016] The homogeneous magnetic field penetrating the diamond can be a bias magnetic field, with which the contributions of the possible spin orientations of the nitrogen vacancies in the diamond can be distinguished during the magnetic resonance measurement even without an external magnetic field acting on the sensor device.

[0017] A particularly advantageous feature of the sensor device according to the invention is that the arrangement of the diamond inside the circuit board and the current-carrying structures arranged inside the circuit board allow for a particularly compact sensor device for magnetic field measurement. Furthermore, manufacturing costs are reduced.

[0018] The current-carrying structures can be designed as coils or current loops. This means that the current-carrying structures can be circular or ring-shaped when viewed from above the circuit board perpendicular to the planes of extension of the layers. Furthermore, the current-carrying structures can enclose the diamond arranged in the inner layer.

[0019] In known devices, the bias magnetic field is generated, for example, using a pair of Helmholtz coils located outside the sensor devices. The sensor device according to the invention eliminates the need for an external pair of Helmholtz coils. The bias magnetic field is generated by the current-carrying structures integrated into the circuit board.

[0020] Further advantageously, the laser emitter can be a laser diode and / or the photodetector a photodiode. Laser diodes can provide the required intensity for optically exciting the nitrogen vacancy centers of the diamond. Furthermore, laser diodes and / or photodiodes are small and inexpensive.

[0021] The laser emitter is preferably designed to emit optical light in the green range, preferably between 520 nm and 530 nm.

[0022] It can be further advantageous for several of the layers to have current-carrying structures for generating the homogeneous magnetic field, wherein the layers are preferably arranged above and below the layer comprising the diamond.

[0023] In a particular embodiment, at least one further layer is provided above the layer comprising the diamond, which further layer comprises a current-carrying structure, for example, designed as a current loop or a coil. Furthermore, a further layer is preferably provided below the layer comprising the diamond, which further layer comprises a current-carrying structure, for example, designed as a current loop or a coil. Several layers with current-carrying structures can also be arranged above and below the layer comprising the diamond.

[0024] The terms above and below refer to a direction perpendicular to the planes of extension of the layers, with layers arranged above the layer comprising the diamond being closer to the top side and the laser emitter arranged on the top side, and layers arranged below the layer comprising the diamond being closer to the bottom side and the photodetector arranged on the bottom side.

[0025] Preferably, it can be provided that the emission direction of the laser emitter is aligned parallel to the top side of the circuit board, and that a first optical element is arranged on a first light exit side of the laser emitter, which first optical element is designed to deflect laser light emerging from the first light exit side, preferably by 90°, so that the laser light strikes the diamond.

[0026] The first optical element is thus designed to redirect the laser beam emerging from the first light exit side of the laser emitter, which exits the laser emitter parallel to the top side of the circuit board, into the interior of the circuit board, preferably by 90°, so that the laser light strikes the diamond arranged there. The laser emitter can therefore be mounted flush and directly on the top side of the circuit board, saving installation space.

[0027] It is preferably provided that the first optical element is arranged in immediate and direct physical contact with the first light exit side of the laser emitter.

[0028] It is preferably provided that the first optical element is a mirror or a prism.

[0029] Further preferably, a second photodetector is provided, wherein the second photodetector is arranged on the underside of the circuit board, and that a second optical element, preferably a mirror or a prism, is arranged on a second light exit side opposite the first light exit side of the laser emitter, which second optical element is designed to deflect laser light emerging from the second light exit side, preferably by 90°, so that the laser light strikes the second photodetector.

[0030] Using the laser light emitted from the second light exit side and directed onto the second photodetector, a reference laser beam can be created and measured with the second photodetector. The reference laser beam serves to correct fluctuations in the laser light power.

[0031] To ensure that the laser light deflected by the second optical element, originating from the top side of the circuit board, reaches the second photodetector located on the underside of the circuit board, an aperture or opening can be provided that penetrates the circuit board from the top side to the underside. Optionally, the opening or aperture can be filled with a light-conducting medium.

[0032] Accordingly, to ensure that the laser light deflected by the first optical element, originating from the top side of the circuit board, reaches the diamond arranged inside the circuit board, an aperture or opening can be provided that penetrates the circuit board from the top side to the diamond. Optionally, the opening or aperture can be filled with a light-conducting medium. Furthermore, a further aperture or opening can be provided that extends from the diamond to the bottom side so that the fluorescent radiation from the diamond can reach the first photodetector.

[0033] It is preferably provided that laser light deflected by the first optical element and / or by the second optical element runs through the circuit board in a direction perpendicular to the layers.

[0034] Preferably, it can be provided that a first optically transparent body, preferably a glass block, is arranged between the first optical element and the diamond, so that light deflected by the first optical element passes through the first optically transparent body and strikes the diamond.

[0035] The laser light deflected by the first optical element exits the first optical element and enters the first optically transparent body. The light then travels through the optically transparent body to the diamond, where it is optically excited. For this purpose, the optically transparent body can be arranged in a corresponding aperture or opening located above the diamond in the circuit board.

[0036] Particularly preferably, the first optically transparent body is located at a distance from and in direct physical contact with the exit side of the first optical element. Further preferably, the diamond arranged below the first transparent body is located at a distance from and in direct physical contact with a bottom side of the first optically transparent body.

[0037] Preferably, the diamond has an optical coating on a top side, preferably the side facing the first optically transparent body, in particular a red reflector, which ensures that green excitation light is almost completely transmitted, while red fluorescent light from the color centers with wavelengths greater than approximately 700 nm is almost completely reflected. Furthermore, the diamond preferably has an optical coating on a bottom side, in particular a green reflector, which ensures that red fluorescent light with wavelengths greater than 700 nm is almost completely transmitted, while green excitation light from the laser emitter is almost completely reflected.

[0038] It is further advantageously provided that a second optically transparent body, in particular a glass block, is arranged between the diamond and the first photodetector, that metallic conductor tracks are arranged on an upper side of the second optically transparent body, wherein a layer of the printed circuit board has lines for the voltage supply of the metallic conductor tracks.

[0039] According to the invention, a second optically transparent body is arranged below the diamond, i.e. closer to the underside of the circuit board, which second optically transparent body is more preferably arranged in direct physical contact with and at a distance from the diamond. In other words, at least one of the layers of the circuit board below the layer comprising the diamond comprises the second optically transparent body. The second optically transparent body has metallic conductor tracks or a metallic coating on an upper side, i.e. the side facing the diamond. The conductor tracks can be applied with widths and spacings of a few micrometers. The layer of the circuit board comprising the second optically transparent body or an adjacent layer further comprises lines for supplying voltage to the metallic conductor tracks of the second optically transparent body.By applying an alternating voltage to the conductors of the corresponding layer, the metallic conductor tracks on the second optically transparent body can be supplied with alternating current. This generates a microwave magnetic field in the diamond, directed parallel to the top surface of the circuit board. A microwave frequency of approximately 2.87 GHz is particularly preferred for this purpose.

[0040] The second optically transparent body can be larger in the plane of extension than the diamond.

[0041] The second optically transparent body is preferably in direct and unspaced physical contact with the diamond.

[0042] It is preferably provided that a third optically transparent body is arranged between the second optically transparent body and the first photodetector.

[0043] The third optically transparent body is preferably in direct physical contact with the underside of the second optically transparent body. Furthermore, the third optically transparent body is preferably in direct physical contact with the top side of the first photodetector.

[0044] Fluorescent light emerging from the diamond passes through the second optically transparent body and through the third optically transparent body to the first photodetector. Apertures, recesses, or openings for the first, second, and third optically transparent bodies can be provided within the circuit board.

[0045] Most preferably, all optical elements—that is, the laser emitter, the first optical element, the first optically transparent body, the diamond, the second optically transparent body, the third optically transparent body, and the photodetector—are in direct physical contact with one another, in that order. This ensures optimal beam guidance of the laser and reduces the installation space for the sensor device.

[0046] It can be further advantageously provided that a fourth optically transparent body, preferably a glass block, is arranged between the second optical element and the second photodetector.

[0047] The fourth optically transparent body is further preferably in direct physical contact with the exit side of the second optical element and the top side of the second photodetector. The fourth optically transparent body is preferably arranged in an aperture, recess, or opening penetrating the circuit board from the top side to the bottom side.

[0048] It is preferably provided that the circuit board has at least 5, preferably at least 7, layers.

[0049] It is further preferably provided that a heat sink and / or ground is arranged on the underside of the circuit board, that the heat sink and / or ground is connected to the laser emitter via a thermal and / or electrical via running from the underside to the top side.

[0050] The electrical power loss of the laser emitter, which can be up to 100 mW, can be dissipated via the electrical or thermal via to the underside of the sensor device or the circuit board and there distributed over a larger area in the heat sink.

[0051] Preferably, the laser emitter, in particular the laser diode, is attached, in particular soldered, with the cathode side to the top side of the circuit board. Further preferably, the anode contact of the laser emitter is connected to the top layer of the circuit board via a wire bond.

[0052] Furthermore, the cathodes of the first and / or second photodetector are preferably electrically and thermally connected to the heat sink and / or ground.

[0053] With further advantage, spacers can be provided between the heat sink and the underside of the circuit board.

[0054] The spacers increase the mechanical stability of the structure.

[0055] With even further advantage, at least five layers have the current-carrying structures for generating the homogeneous magnetic field.

[0056] Particularly preferably, the circuit board has dimensions of 5 mm x 5 mm, measured in the plane of extension. Furthermore, the components for a laser emitter driver circuit, a microwave driver circuit, and a photodetector evaluation circuit can be integrated on or in the circuit board. These components are preferably designed as ASIC modules.

[0057] Most preferably, the sensor device has a box volume of 2 cm x 2 cm x 0.5 cm.

[0058] The invention is explained in more detail below with reference to the attached figure.

[0059] The single figure shows a sensor device for magnetic field measurement comprising a laser emitter and a diamond arranged in a circuit board.

[0060] The figure shows a sensor device 100 for magnetic field measurement using optical magnetic resonance measurement. The sensor device 100 comprises a diamond 10 with a plurality of color centers (not shown in detail), which in this case are negatively charged nitrogen vacancies or NV centers. The sensor device 100 further comprises a circuit board 11. A laser emitter 13 is arranged on a top side 12 of the circuit board 11. The laser emitter 13 is designed as a laser diode 14 and emits green light at a wavelength of 520 nm to 530 nm. The circuit board 11 has several layers 15. The several layers 15 comprise an inner layer 15a. The diamond 10 is arranged in the extension plane 16 of the inner layer 15a. A first photodetector 18 is arranged on an underside 17 of the circuit board 11.The laser emitter 13 is arranged on the top side 12 of the circuit board 11 such that the laser light is emitted parallel to the top side 12 of the circuit board 11. In order to guide the laser light emitted by the laser emitter 13 onto the diamond 10, an optical element 19 designed as a prism 19a is arranged on a first light exit side 32a of the laser emitter 13, which optical element redirects the laser light by 90° downwards in the direction of the diamond 10 into the circuit board 11. A first optically transparent body 21 is arranged between the first optical element 19 and the diamond 10 in an opening 20 provided for this purpose in the circuit board 11. Below the diamond 10, a second optically transparent body 23 and a third optically transparent body 24 are arranged in a further opening 22 of the circuit board 11, wherein the third optically transparent body 24 is arranged below the second optically transparent body 23.Laser light emerging from the first light exit side 32a of the laser emitter 13 passes through the first optical element 19 and the first optically transparent body 21 and strikes the diamond 10, where it excites the nitrogen vacancies. Red-shifted fluorescent light is then emitted from the diamond 10, which passes through the second optically transparent body 23 and the third optically transparent body 24 and strikes the first photodetector 18.

[0061] The diamond 10 has a red reflector 26 on a top side 25, which ensures that green excitation light is almost completely transmitted, while red fluorescent light from the nitrogen vacancies with wavelengths greater than approximately 700 nm is almost completely reflected. Furthermore, the diamond 10 has a green reflector 28 on a bottom side 27, which ensures that red fluorescent light with wavelengths greater than 700 nm is almost completely transmitted, while green excitation light from the laser emitter 13 is almost completely reflected. Metallic conductor tracks 30 are arranged on the top side 29 of the second optically transparent body 23. To supply voltage to the electrical conductor tracks 30, lines 30a are provided on the layer 15b of the circuit board 11 comprising the second optically transparent body 23. By applying an alternating frequency of approx.By applying a microwave magnetic field of 2.87 GHz to the lines 30a, a microwave magnetic field can be generated in the diamond 10, which is directed parallel to the top side 12 of the circuit board 11. Furthermore, several of the inner layers 15c have current-carrying structures 31, which are designed to generate a homogeneous magnetic field oriented perpendicular to the layers 15 of the circuit board 11 and penetrating the diamond 10. The layers 15c carrying the current-carrying structures 31 are arranged above and below the layer 15a surrounding the diamond 10.

[0062] On the second light exit side 32b of the laser emitter 13, opposite the first light exit side 32a, there is a second optical element 33 which deflects the laser light emerging from the second light exit side 32b downward by 90° toward a second photodetector 34 arranged on the underside 17 of the circuit board 11. A fourth optically transparent body 36 is inserted into a recess 35 in the circuit board 11. The light emerging from the second optical element 33 passes through the fourth optically transparent body 36 and is detected by the second photodetector 34. The laser beam detected by the second photodetector 34 serves as a reference beam to correct fluctuations in the laser light power. The laser emitter 13 is soldered onto the top side 12 of the circuit board 11 with the cathode side 37 facing downward.The anode contact 39 of the laser emitter 13 is connected to the upper layer 15d of the circuit board 11 via a wire bond 38. A thermal and electrical via 40 is arranged in the circuit board 11 below the cathode side 37 of the laser emitter 13, which extends down to a heat sink and ground 41 arranged on the underside 17 of the circuit board 11. The thermal dissipation of the laser emitter 13 can be dissipated via the via 40.

[0063] The cathodes of the first photodetector 18 and the second photodetector 34 are electrically and thermally connected to the heat sink and ground 41. Furthermore, spacers 42 are provided below the circuit board 11, which keep the heat sink and ground 41 at a distance and increase the mechanical stability of the structure.

Claims

1. Sensor device (100) for magnetic field measurement by means of optical magnetic resonance measurement (ODMR), comprising a diamond (10) having a multiplicity of colour centres, in particular nitrogen defects, a laser emitter (13), a first photodetector (18) and a printed circuit board (11), wherein the laser emitter (13) is configured for fluorescence excitation of the colour centres in the diamond (10), wherein the first photodetector (18) is configured to receive fluorescence radiation from the colour centres of the diamond (10), characterized in that the printed circuit board (11) comprises a plurality of layers (15, 15a, 15b 15c, 15d) comprising at least one inner layer (15a), in that the laser emitter (13) is arranged on a top side (12) of the printed circuit board (11), in that the first photodetector (18) is arranged on a lower side (17) of the printed circuit board (11), in that the diamond (10) is arranged in the interior of the printed circuit board (11) in the plane of extent (16) of the at least one inner layer (15a), and in that at least one of the layers (15c) has current-carrying structures (31), which are configured to produce a homogeneous bias magnetic field perpendicular to the layers (15, 15a, 15b 15c, 15d) of the printed circuit board (11), which field passes through the diamond (10), and wherein at least one of the layers (15b) below the layer (15a) comprising the diamond (10) has a second optically transparent body (23), the top side (29) of which has metallic conductor tracks (30) or a metallic coating, and wherein the layer (15a) comprising the diamond (10) or an adjoining layer has lines (30a) for supplying the metallic conductor tracks (30) with power, such that, by applying AC voltage to the lines (30a), a microwave magnetic field can be generated in the diamond (10), which is directed parallel to the top side (12) of the printed circuit board (11).

2. Sensor device (100) according to Claim 1, characterized in that the laser emitter (13) is a laser diode (14), and / or in that the photodetector (18) is a photodiode.

3. Sensor device (100) according to Claim 1 or 2, characterized in that a plurality of the layers (15c) have current-carrying structures (31) for generating the homogeneous bias magnetic field, wherein the layers (15c) are preferably arranged above and / or below the inner layer (15a) comprising the diamond (10).

4. Sensor device (100) according to any one of the preceding claims, characterized in that the emission direction of the laser emitter (13) is aligned parallel to the top side (12) of the printed circuit board (11), and in that a first optical element (19) is arranged on a first light exit side (32a) of the laser emitter (13) which is configured to deflect laser light emerging from the first light exit side (32a), preferably by 90°, such that the laser light is incident on the diamond (10), wherein further preferably the first optical element (19) is a mirror or a prism (19a).

5. Sensor device (100) according to Claim 4, characterized in that a second photodetector (34) is provided, in that the second photodetector (34) is arranged on the lower side (17) of the printed circuit board (11), and in that a second optical element (33), preferably, a mirror or a prism, is arranged on a second light exit side (32b) lying opposite the first light exit side (32a) of the laser emitter (13), which second optical element is configured to deflect laser light emerging from the second light exit side (32b) preferably by 90°, such that the laser light is incident on the second photodetector (34).

6. Sensor device (100) according to Claim 4 or 5, characterized in that a first optically transparent body (21), preferably a glass block, is arranged between the first optical element (19) and the diamond (10) such that light deflected by the first optical element (19) passes through the first optically transparent body (21) and is incident on the diamond (10).

7. Sensor device (100) according to any one of the preceding claims, characterized in that a third optically transparent body (24) is arranged between the second optically transparent body (23) and the first photodetector (18).

8. Sensor device (100) according to any one of the preceding claims, characterized in that a fourth optically transparent body (36), preferably a glass block, is arranged between the second optical element (33) and the second photodetector (34).

9. Sensor device (100) according to any one of the preceding claims, characterized in that the printed circuit board (11) has at least 5, preferably at least 7, layers (15, 15a, 15b 15c, 15d) and / or in that a heat sink and / or ground (41) is arranged on the lower side (17) of the printed circuit board (11), in that the heat sink and / or ground (41) is connected to the laser emitter (13) via a thermal and / or electrical via (40) extending from the lower side (17) to the top side (12).