Measuring probe with a quantum emitter

Abstract

The present invention relates to a method for manufacturing a measuring probe, said method comprising the following steps: introducing two glass fibres and two electric lines into a sleeve; filling the sleeve with a carrier material, wherein the carrier material at least partially encloses the glass fibres and / or electric lines; curing the carrier material in the sleeve; polishing an end of the glass fibres, electric lines and / or carrier material received in the sleeve; arranging an HF antenna on the tip; and transferring a quantum emitter to the tip; laser-writing a light-guiding structure for optically connecting the quantum emitter to the first glass fibre and to the second glass fibre, wherein the first glass fibre is optically decoupled from the second glass fibre. The invention also relates to a measuring probe and a system.

Description

[0001] MEASURING PROBE WITH A QUANTUM EMITTER

[0002] The present invention relates to a method for producing a measuring probe, a corresponding measuring probe and a system with a corresponding measuring probe.

[0003] Quantum emitters, such as nitrogen vacancy centers in diamonds, are a promising candidate for sensors because they exhibit high magnetic sensitivity per volume and enable, among other things, measurements at room temperatures. It is known that quantum emitters can also be used to measure electric fields, temperatures, and vectorial magnetic fields.

[0004] Previous systems with such quantum emitters are mostly constructed in a microscope-like manner and are therefore more complicated to handle and less flexible in their application. One such system is disclosed, for example, at https / d oi . org / 10.1515 / nanoph-2019-0209.

[0005] Fiber-optic systems are known to improve handling. However, the disadvantage of these systems is that, while a certain reduction in size can be achieved, they cannot be sufficiently miniaturized to a size of a few millimeters or less. In particular, a deterministic method for fixing and connecting nanoscopically small quantum emitters is lacking. Furthermore, the influence of self-fluorescence increases with decreasing scale, thus limiting the possibilities of a simple reduction in size.

[0006] From the published patent application US 2021 0 196 177 A1, a magnetoencephalography device with a first magnetic field sensor attached to a line is known.

[0007] The present invention aims to create a stable, movable, and / or flexible measuring platform with minimal dimensions. In particular, a measuring probe is to be created that incorporates all the necessary elements for measurement. Particularly preferred is a measuring probe and a method for producing a measuring probe, wherein deterministic positioning of the quantum emitter on the measuring probe and subsequent fixation are possible.

[0008] This object is achieved by a method for producing a measuring probe according to claim 1, comprising the following steps:

[0009] Inserting at least two optical fibers and at least two electrical lines into a sleeve;

[0010] Filling the sleeve with a carrier material, which preferably comprises an epoxy resin, wherein the carrier material surrounds the glass fibers and / or the electrical lines at least in sections;

[0011] Curing of the carrier material in the sleeve;

[0012] Polishing one end of the glass fibers, electrical wires and / or the carrier material contained in the sleeve;

[0013] Arranging a radio-frequency antenna (RF antenna) on the polished tip; transferring a quantum emitter to the tip so that the quantum emitter can be excited by the RF antenna and fixed to a tip of a fiber optic cable;

[0014] Laser writing of a first and second optical fiber structure for optically and in particular physically connecting the quantum emitter to the first optical fiber and to the second optical fiber, wherein the first optical fiber is optically decoupled from the second optical fiber.

[0015] Furthermore, the object is achieved by a measuring probe, in particular manufactured according to the method described above, comprising: a quantum emitter; an RF antenna; two optical fibers and two electrical lines; a laser-scribed first optical fiber structure for optical connection and in particular for physical connection of the quantum emitter to the first optical fiber, for forming an optical feed line; a laser-scribed second optical fiber structure for optical connection and in particular for physical connection of the quantum emitter to the second optical fiber, for forming a signal line, wherein the feed line and the signal line are optically decoupled; the signal line is designed to conduct a measurement signal away from the quantum emitter; and the feed line is designed to conduct an excitation signal to the quantum emitter.

[0016] Finally, the above object is achieved by a system for measuring a temperature, a magnetic field and / or an electric field, comprising: a measuring probe as described above; an optical excitation unit for exciting a quantum emitter of the measuring probe; an RF excitation unit for generating an RF magnetic field by means of the RF antenna of the measuring probe; and an evaluation unit for receiving and / or evaluating a measurement signal from the measuring probe in response to excitation of the quantum emitter of the measuring probe by means of an optical excitation signal and by means of an RF magnetic field; wherein the evaluation unit is designed to determine a temperature, a magnetic field and / or an electric field at the tip of the measuring probe, in particular at the quantum emitter, based on the measurement signal.

[0017] The incorporation of at least two glass fibers and at least two electrical lines into a sleeve enables advantageous alignment of the glass fibers and electrical lines. In particular, the use of two glass fibers minimizes disruptive intrinsic fluorescence influences, particularly of the glass fiber. A higher degree of miniaturization and increased sensitivity can be achieved. A sleeve enables safe handling of the individual components during the individual processing steps during the manufacture of the measuring probe. A sleeve is particularly designed as a cylindrical tube. The sleeve can preferably be removed after completion of the manufacturing process. It is understood that the sleeve can also remain on the measuring probe.

[0018] By using a carrier material, particularly an epoxy resin, the stability of the individual components and the measuring probe can be increased. In particular, a cured carrier material can fix the alignment and position of the individual components relative to each other. Subsequent polishing of one end of the mixture of cured carrier material, the two glass fibers, and / or the electrical lines can create a basis for connecting the glass fibers and electrical lines. In particular, polishing can achieve a high signal yield with the measuring probe.

[0019] Arranging the RF antenna on the polished tip enables the creation of a comparatively small RF antenna that is stable and positioned accurately relative to the other components of the measuring probe. The RF antenna can preferably be produced using an additive process; more preferably, the RF antenna is written onto the tip using a laser writing process. The quantum emitter can be transferred to the prepared tip.

[0020] For this purpose, the quantum emitter can preferably be moved under the tip using an XYZ stage, precisely aligned, and finally transferred to the tip. Laser-writing a light guide structure enables precise connection of the quantum emitter to the first and second optical fibers.

[0021] Preferably, the optical decoupling is effected such that excitation light can be radiated into the quantum emitter through the first laser-scribed optical fiber structure in a first direction, which is different from the direction directed to the second optical fiber by the second laser-scribed optical fiber structure. It is understood that a multitude of possible directions are conceivable. Particularly preferably, the laser-scribed optical connections are configured such that a direction of the excitation light forms an angle of approximately 90 degrees to the direction of the light emitted and detected by the quantum emitter. Preferred embodiments of the invention are described in the dependent claims.It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or independently, without departing from the scope of the present invention. In particular, the measuring probe and the system can be designed according to the embodiments described for the method in the dependent claims.

[0022] In a preferred embodiment, the method comprises the steps:

[0023] Creating a suspension of a photoresist and the quantum emitter;

[0024] Positioning the suspension, preferably as drops, on a carrier plate;

[0025] Position the support plate in a predefined position relative to the polished end. The above steps are performed before the step of transferring the quantum emitter to the tip.

[0026] By placing the quantum emitter in a photoresist suspension and transferring this droplet onto the polished tip, the quantum emitter can be transferred together with a medium that allows the light-guiding structure to be laser-written. No additional transfer and holding structures are required, as the quantum emitter can be fixed in the photoresist by laser writing. Furthermore, optical connections can be created directly using the photoresist by laser writing. Preferably, the quantum emitter is transferred from the photoresist suspension onto a carrier plate. The carrier plate is moved under the polished tip using an XYZ table, aligned, and then transferred to the tip by moving it toward the tip. It is understood that more than two optical fibers can also be used.In this case, at least one of the glass fibers, which serves in particular as a supply line, is connected to the quantum emitter by means of a light-guiding structure made of a polymer. Furthermore, at least one of the glass fibers, which serves as a signal line, is connected to the quantum emitter by means of a light-guiding structure.

[0027] The glass fibers, which serve as supply lines, direct light to the quantum emitter. The glass fibers, which serve as signal lines, guide light from the quantum emitter to a detector unit.

[0028] Preferably, the laser writing of a first and second optical fiber structure comprises laser writing using polymer lacquer on a first optical fiber structure between a glass fiber core of the first optical fiber and the quantum emitter, and on a second optical fiber structure between a glass fiber core of the second optical fiber and the quantum emitter. The first optical fiber structure preferably comprises an optical connection to the quantum emitter that is perpendicular to an optical connection of the second optical fiber structure to the quantum emitter. This allows the creation of a stable physical structure that fixes the quantum emitter with respect to the two optical fibers. Furthermore, the laser writing can reliably achieve optical decoupling of the first and second optical fibers when connecting the quantum emitter.

[0029] The RF antenna is particularly preferably arranged at the tip using an additive process, in particular by laser writing. In addition, a material of the RF antenna comprises a material compatible with the material of the electrical lines. Furthermore, the electrical lines and the material of the RF antenna comprise, in particular, silver, copper and / or gold. By laser writing an RF antenna, a high-precision RF antenna can be created on a small scale. In particular, laser writing of the RF antenna enables an advantageous connection of the RF antenna to the electrical lines. By choosing a compatible material, functionality can be improved. The quality of the obtained data can be increased. In particular, the reliability of the measuring probe can be increased. With the method used, free antenna geometries can be produced in principle, which direct the field specifically to the quantum emitter orin the near field and generate the highest possible RF field intensity at the quantum emitter.

[0030] Advantageously, the method of direct laser writing of the RF antenna can optimize the homogeneity of the radiated near field and thus achieve better sensitivity.

[0031] Advantageously, the method comprises the step of adjusting the impedance of the RF antenna by measuring reflection and adapting the length of the electrical lines. This advantageous adjustment method allows a preferred impedance of the RF antenna to be set without having to make any changes to the RF antenna. In particular, the impedance of the RF antenna can also be changed subsequently, if necessary.

[0032] In a preferred embodiment, the method comprises the step of attaching a static magnetic field source, in particular a permanent magnet or a coil, in an area surrounding the tip to generate a static background magnetic field. A static background magnetic field is particularly advantageous for measuring very weak magnetic fields or electric fields. A permanent magnet can be used to create a passive component that therefore does not require separate control. By setting up a permanent magnetic field using a coil, a controllable background magnetic field can be set up, the strength of which can be adjusted, in particular, to the area to be measured. A static magnetic field is understood to be a magnetic field that has a constant magnetic field strength over a predefined period of time.

[0033] In a preferred embodiment of the measuring probe, it has at least two additional electrical lines and an additional laser-etched RF antenna. This allows for more precise excitation of the quantum emitter using the two RF antennas. Particularly preferably, a superposition of different excitation modes and / or a phase of the microwave field can be set up.

[0034] In a further preferred embodiment, the measuring probe comprises at least one additional optical fiber, which forms at least one additional supply line and / or one additional signal line. This allows the quantum emitter to be preferably superimposed with multiple light frequencies and to be optically excited more homogeneously from different directions. An additional signal line can improve the data quality of the received signal from the quantum emitter.

[0035] In a preferred embodiment of the system, the system comprises an optical connection unit arranged between the optical excitation unit and the measuring probe, as well as between the evaluation unit and the measuring probe. The optical connection unit has a first input interface, a second input interface, an optional third input interface, an output interface, and a combined input / output interface.

[0036] The interfaces are preferably designed as fiber couplers and are preferably used to connect glass fibers to the optical connection unit.

[0037] The first input interface is configured to couple in a first excitation signal in the form of laser light of a first wavelength. The second input interface is configured to couple in a second excitation signal in the form of laser light of a second wavelength. To this extent, the first input interface and the second input interface are connectable to laser light sources.

[0038] The third input interface is designed to couple in a measurement signal. Consequently, the third input interface is provided for connection to the measuring probe, in particular a signal line of the measuring probe.

[0039] The output interface is designed to couple the measurement signal. Consequently, the output interface is connected to a detector.

[0040] The combined input / output interface is designed to output the first excitation signal, the second excitation signal, and / or to input the measurement signal. Consequently, the combined input / output interface is preferably connected to the signal line of the measuring probe and / or the supply line of the measuring probe.

[0041] Between the first input interface and the combined input / output interface, a first light guide path is formed by a first mirror, a second mirror, and a first beam-overlapping element, in particular a first dichroic mirror. The first light guide path preferably further comprises a first waveplate, a first polarizing beam splitter, and a first filter.

[0042] Between the second input interface and the combined input / output interface, a second light guide path is formed by a third mirror, a fourth mirror, and a second beam-overlapping element, in particular a second dichroic mirror. The second light guide path preferably comprises a second waveplate, a second polarizing beam splitter, and a second filter, and in particular runs through the first beam-overlapping element. Between the combined input / output interface and the output interface, a third light guide path is formed by a fifth mirror and a sixth mirror. The third light guide path runs through the first beam-overlapping element and the second beam-overlapping element and preferably has a third filter and a fourth filter.

[0043] Between the third input interface and the output interface, a fourth light guide path is formed by an optional seventh mirror, the fifth mirror, and the sixth mirror. The fourth light guide path preferably comprises the third filter and the fourth filter.

[0044] The optical connection unit further comprises an optional optical separator that interrupts the third light guide path and shields the first light guide path and the second light guide path from the fourth light guide path. The first light guide path, the second light guide path, and the third light guide path optionally have an additional wave plate.

[0045] The optical connection unit is preferably designed as a compact box with a width of approximately 24 centimeters. The first wavelength is preferably in the range of 515 to 532 nanometers. The second wavelength is in the range of 580 to 640 nanometers.

[0046] Preferably, several wavelengths in a preferred wavelength range can also be superimposed in the first light guide path and / or in the second light guide path.

[0047] The invention is based on the measurement principle of exciting a quantum emitter, for example, a diamond with a nitrogen vacancy center in the diamond lattice, and obtaining information about magnetic and electric fields or temperatures based on brightness differences of this diamond. These brightness differences are transmitted to a detector via the light guide structure and a fiber optic cable. The basic measurement principles, such as optically detected magnetic resonance, the Zeeman effect, etc., are known to those skilled in the art and are described, for example, at https: / / doi.org / 10.48550 / arXiv.2108.06060.

[0048] RF refers specifically to high frequency. In electrical engineering, the frequency range from 9 kHz to the terahertz range is referred to as radio frequency.

[0049] An XYZ stage is a three-axis system, preferably consisting of three single-axis linear guide systems, that allows an object to be moved in three spatial directions. An XY stage enables movement within a single plane.

[0050] Laser writing, especially direct laser writing, is a generic term for additive, subtractive, and modifying manufacturing processes in which a relative motion is generated between a laser beam and a material, thereby causing ablation, transfer, or modification of the material. In addition to laser-induced chemical vapor deposition and selective laser sintering, stereolithography and multiphoton lithography are established as standard processes.

[0051] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show:

[0052] Figure 1 shows a schematic system according to the invention with a

[0053] measuring probe, an optical excitation unit, an RF excitation unit, an optional static magnetic field source and an evaluation unit;

[0054] Figure 2 shows a schematic representation of a head of a measuring probe; Figures 3a to 3f show schematic representations of individual steps for producing a measuring probe;

[0055] Figure 4 is a schematic representation of a structure of a measuring apparatus using the measuring probe;

[0056] Figure 5 is a schematic representation of an optical connection unit;

[0057] Figure 6 is a schematic perspective view of a coaxial structure of a measuring probe; and

[0058] Figure 7 is a schematic perspective view of another measuring probe.

[0059] Figure 1 schematically shows a system 10 for measuring a magnetic field, a temperature and / or an electric field.

[0060] The system 10 comprises an evaluation and excitation device 12 and a measuring probe 14. The evaluation and excitation device 12 comprises an optional optical connection unit 16, an optical excitation unit 18, an evaluation unit 20, and an RF excitation unit 22.

[0061] The measuring probe 14 comprises a first glass fiber 24 and a second glass fiber 26, both of which are optically decoupled from each other and connected to a quantum emitter 28.

[0062] The first optical fiber 24 and the second optical fiber 26 are connected to the optical excitation unit 18 and the evaluation unit 20 by means of the optional optical connection unit 16.

[0063] The RF excitation unit 22 is connected to an RF antenna 34 via a first electrical line 30 and a second electrical line 32. The RF antenna 34 is arranged in an area surrounding the quantum emitter 28 and can excite it with RF radiation.

[0064] Furthermore, an optional static magnetic field source 35 is arranged near the quantum emitter 28. It is understood that the representation of the static magnetic field source 35 is only symbolic and any known static magnetic field source, such as a permanent magnet or a coil, can be used.

[0065] In this case, static means, in particular, that a constant background magnetic field can be created for a specific period of time. A person skilled in the art will recognize that a coil can create magnetic fields of varying strengths. These are also considered static in this case if they exhibit a constant magnetic field strength over a predefined period of time.

[0066] In the example shown, the quantum emitter 28 is formed as a diamond with nitrogen vacancy centers.

[0067] Figure 2 schematically shows a head of a measuring probe 14 in more detail. The head has a preferably laser-etched optical fiber structure between the first optical fiber 24 and the quantum emitter 28. Optically decoupled from this, the head has a second optical fiber structure from the second optical fiber 26 to the quantum emitter 28. In the illustrated embodiment, the two optical fiber structures at the quantum emitter 28 are perpendicular to each other. It is understood that other geometries are also conceivable.

[0068] The connections created by the optical fiber structures optically connect the quantum emitter 28 to the two glass fibers 24, 26. They also physically fix the quantum emitter 28 to the head. In the illustrated embodiment, the RF antenna 34 is designed as a so-called microstripline. It essentially comprises a flat, rectangular cross-section that connects the two electrical lines 30, 32. The two electrical lines 30, 32 are formed, for example, from silver cables or silver wires.

[0069] Figures 3a to 3f schematically show the individual steps for producing a measuring probe 14, with a side view of the components being shown on the left and a top view of the components being shown on the right.

[0070] In Figure 3a, according to a first step for producing a measuring probe, at least two glass fibers 24, 26 and at least two electrical lines 30, 32 are introduced into a sleeve 36. The sleeve 36 can preferably be a hollow ceramic sleeve, i.e., a hollow ceramic tube.

[0071] As shown in Figure 3b, a further step involves filling the sleeve 36 with a carrier material. The carrier material can be, for example, an epoxy resin. The carrier material surrounds the glass fibers 24, 26 and / or the electrical lines 30, 32 at least in sections. It is understood that an adhesive or other filler material can also be used instead of an epoxy resin. The filler material is then cured. The filling and curing preferably take place in a mold (not shown).

[0072] Figure 3c schematically shows a further step in which one end of the glass fibers 24, 26, electrical lines 30, 32, and / or the carrier material accommodated in the sleeve 36 is polished. Preferably, an at least partially flat surface can be created to allow the attachment of additional components to the measuring probe 14.

[0073] Figure 3d schematically illustrates the attachment of an RF antenna 34 to the measuring probe 14, wherein the RF antenna 34 is conductively connected to the two electrical lines 30, 32. In the embodiment shown in Figure 3d, the RF antenna 34 is arranged on the polished tip by laser writing with a laser writing device 38. It is understood that other attachment options are also conceivable, such as vapor deposition and / or mechanical application. In principle, any other, preferably additive, process is suitable.

[0074] Figure 3e schematically illustrates the step of transferring a quantum emitter 28 to the polished tip. The quantum emitter 28 is positioned at the tip in such a way that it can be excited by the RF antenna 34. For this purpose, a drop 40 of a photoresist emulsion is preferably formed, and the quantum emitter 28, together with the drop 40, is transferred to the tip.

[0075] For this purpose, the droplet 40 can preferably first be transferred to a glass support plate, which is then aligned relative to the tip of the measuring probe 14 using an XYZ table. This allows for precise positioning of the quantum emitter 28. Transfer can be achieved, for example, by moving the XYZ table toward the tip of the measuring probe 14. Alternatively, the tip can also be moved toward an XY table, which serves to position the droplet and quantum emitter relative to the tip.

[0076] Photoresist is understood, in particular, to be a transparent, low-fluorescence polymer resist. Furthermore, the photoresist is preferably suitable for an additive direct laser writing process or the like.

[0077] Figure 3f schematically illustrates the step of writing a first optical fiber structure for optically and physically connecting the quantum emitter 28 to the first optical fiber 24 and a second optical fiber structure for optically and physically connecting the quantum emitter 28 to the second optical fiber 26. The first optical fiber 24 is optically decoupled from the second optical fiber 26. Furthermore, the first optical fiber structure is also optically decoupled from the second optical fiber structure.

[0078] Optical decoupling means that preferably no or only little light is transmitted from the first glass fiber and the first light guide structure into the second glass fiber and / or second light guide structure and vice versa.

[0079] Figure 4 schematically shows a measurement setup for measuring with a measuring probe 14. The measuring probe 14 is shown on the left in Figure 4 and comprises two glass fibers 24, 26, which in the embodiment shown are arranged around the two electrical lines 30, 32. The first glass fiber 24 is optically connected to the quantum emitter 28 by means of a first optical fiber structure 42. The second glass fiber 26 is optically connected to the quantum emitter 28 by means of a second optical fiber structure 44. The two glass fibers 24, 26 and the two optical fiber structures 42, 44 are optically decoupled from one another.

[0080] The RF antenna 34 is arranged between the optical fiber structures 42, 44 and is electrically connected to the electrical lines 30, 32. An object 45 to be measured is arranged in front of the measuring probe 14.

[0081] The object 45 to be measured can, for example, be a magnetic and / or electrical source or a warm / cold object, in particular a warm / cold liquid or a warm / cold fluid. The electric and / or magnetic fields and / or thermal radiation / heat conduction or a temperature can be measured at the location of the quantum emitter 28, so that the object 45 to be measured can ultimately be measured.

[0082] The first optical fiber 24 is connected via a first interface 46a to a light sensor 20b and a data acquisition unit 20a, which together form a detector. Furthermore, the first optical fiber 24 is optically connected via the first interface 46a to a first laser light source 18a.

[0083] The second optical fiber 26 is connected to a second laser light source 18b by means of a second interface 46b.

[0084] The first electrical line 30 and the second electrical line 32 are connected by means of electrical connections 48 to an RF excitation unit 22, in particular a microwave source preferably for the range from 2.4 GHz to 3.5 GHz.

[0085] The light sources 18a, 18b, the RF excitation unit 22, and the data acquisition unit 20a are connected to a computer 49. A part of the computer 49, together with the data acquisition unit 20a and the light sensor 20b, forms an evaluation unit.

[0086] Another part of the computer 49 is configured to control the laser light sources 18a, 18b and the RF excitation unit 22. It is understood that the data acquisition unit 20a is configured and configured to transmit the fluorescence of the quantum emitter 28 detected by the light sensor 20b to the computer 49 as a suitable data format.

[0087] The second optical fiber 26 and the second light guide structure 44 form a second optical connection, which is preferably designed to transmit excitation light only to the quantum emitter 28, but not into the first light guide structure 42 and the first optical fiber 24.

[0088] The first glass fiber 24 preferably comprises a so-called multimode fiber, which on the one hand guides excitation light via a conductive / transparent, low-fluorescence structure, for example a polymer structure, to the quantum emitter 28 and collects fluorescent light from the optically excited quantum emitter 28 as efficiently as possible and forwards it to the light sensor 20b.

[0089] Consequently, excitation can occur via both the first optical fiber 24 and the second optical fiber 26, while detection preferably occurs only via the first optical fiber 24.

[0090] The RF antenna 34 is connected to the electrical lines 30, 32 and is designed to emit a high magnetic microwave field in the near field in the direction of the quantum emitter 28.

[0091] The tips of the electrical lines 30, 32 and the glass fibers 24, 26 as well as the RF antenna and the optical connections created by means of the light guide structures 42, 44 form a measuring probe.

[0092] In order to obtain sufficient mechanical stability, the tips of the electrical lines 30, 32 and the glass fibers 24, 26 are embedded, for example, in a ceramic sleeve and fixed with a filling material, in particular an epoxy resin.

[0093] To protect the structure and increase stability, a protective cap (not shown for reasons of clarity) can also surround the RF antenna 34, the light guide structures 42, 44 and the quantum emitter 28.

[0094] Figure 5 shows a schematic diagram of an optical connection unit.

[0095] The optional optical connection unit 16 has three input interfaces 46.1-46.3, one output interface 46.4 and one combined input / output interface 46.5.

[0096] The first input interface 46.1 is configured to couple in a first excitation signal in the form of laser light of a first wavelength or a first wavelength range. The first wavelength preferably comprises light in a range from 515 nanometers to 532 nanometers.

[0097] The second input interface 46.2 is configured to couple in a second excitation signal in the form of laser light of a second wavelength or a second wavelength range. The second wavelength is preferably in a range of 580 nanometers to 640 nanometers.

[0098] The third input interface 46.3 is an optional input interface. It is therefore not mandatory. The third input interface 46.3 is designed to couple a measurement signal into the optional optical connection unit 16. It can therefore be coupled to the first fiber optic cable 24.

[0099] The output interface 46.4 is designed to output the measurement signal. Therefore, the output interface 46.4 is preferably optically connected to a light sensor or an evaluation unit.

[0100] The combined input / output interface 46.5 is designed to output the first excitation signal, the second excitation signal, and / or to input the measurement signal. The combined input / output interface 46.5 can thus be optically connected to the first optical fiber 24 or to the second optical fiber 26.

[0101] A first light guide path runs between the first input interface 46.1 and the combined input / output interface 46.5. This is shown in dashed lines in the figure. The first light guide path is set up by a first mirror 50.1, a second mirror 50.2 and a first beam superimposing element 51.1, which in the embodiment shown comprises a first dichroic mirror. Furthermore, a first optional wave plate 54.1 and a first optional polarizing beam splitter 56.1 are arranged in the first light guide path between the first mirror 50.1 and the first input interface 46.1. A further optional wave plate 55 is arranged between the first dichroic mirror and the combined input / output interface 46.5. A first optional filter 52.1 is arranged between the second mirror 50.2 and the first dichroic mirror.

[0102] A second light guide path is formed between the second input interface 46.2 and the combined input / output interface 46.5. The second light guide path comprises a third mirror 50.3, a fourth mirror 50.4, and a second beam-overlapping element 51.2, which is also designed as a second dichroic mirror. A second optional waveplate 54.2 and a second optional polarizing beam splitter 56.2 are arranged in the second light guide path between the second input interface 46.2 and the third mirror 50.3. The first dichroic mirror and the further optional waveplate 55 are arranged between the second dichroic mirror and the combined input / output interface 46.5. A second optional filter 52.2 is arranged between the fourth mirror 50.4 and the second dichroic mirror.

[0103] A third light guide path is formed between the combined input / output interface 46.5 and the output interface 46.4. The third light guide path comprises a fifth mirror 50.5 and a sixth mirror 50.6. The first and second dichroic mirrors, as well as the additional optional waveplate 55, are arranged in the third light guide path between the fifth mirror 50.5 and the combined input / output interface 46.5. A third optional filter 52.3 is arranged between the sixth mirror 50.6 and the output interface 46.4. A fourth optional filter 52.4 is arranged between the fifth mirror 50.5 and the sixth mirror 50.6.

[0104] A fourth light guide path is formed between the optional third input interface 46.3 and the output interface 46.4. The fourth light guide path includes an optional seventh mirror 50.7, the fifth mirror 50.5, and the sixth mirror 50.6. The fourth light guide path preferably includes the third optional filter 52.3 and the fourth optional filter 52.4.

[0105] To improve the shielding of the individual light guide paths from one another, an optional optical separator 58 can be provided. The optional optical separator 58 interrupts the third light guide path and shields the first light guide path and the second light guide path from the fourth light guide path.

[0106] In the figure, the individual light guide paths are shown in dashed lines. Optional elements are also shown in dashed lines.

[0107] The excitation light, i.e. light that is brought into the optional optical connection unit 16 via the first input interface 46.1 and / or the second input interface 46.2, is preferably adjusted in polarization by a wave plate, in particular a lambda / 2 plate, in such a way that maximum transmission through the respective polarizing beam splitter 56.1 and 56.2 is achieved.

[0108] The beam splitters 56.1, 56.2 also ensure that, if possible, only linearly polarized light is transmitted in one oscillation direction. The first to fourth mirrors 50.1 to 50.4 serve to optimize and adjust the respective beam position and angle so that maximum coupling efficiency into the connected fiber optic cable, i.e., the first fiber optic cable 24 or the second fiber optic cable 26, can be achieved at the combined input / output interface 46.5. The first and second filters 52.1, 52.2 serve to filter the excitation light in a wavelength-selective manner.

[0109] Dichroic mirrors are mirrors that transmit light above a certain wavelength and reflect light below a certain wavelength. This means that laser beams of different wavelengths can be superimposed if properly selected, and fluorescent light above a higher wavelength can be transmitted through the dichroic mirrors almost unhindered to a detector.

[0110] In the embodiment shown, the cutoff wavelength of the first dichroic mirror is 550 nanometers, and that of the second dichroic mirror is 660 nanometers.

[0111] Thus, light with a wavelength shorter than 550 nanometers can be directed via the first dichroic mirror, and light with a wavelength shorter than 660 nanometers can be directed via the second dichroic mirror to the combined input / output interface 46.5, i.e., the measuring probe. Light with a wavelength longer than 660 nanometers, however, is transmitted through the mirrors to the output interface 46.4, i.e., the detector.

[0112] The additional wave plate 55 can be installed between the combined input / output interface 46.5 and the first and second light guide path, i.e. the excitation light, in order to change the polarization of the excitation light towards the measuring probe and thereby further increase the sensitivity.

[0113] The combined input / output interface 46.5 can be used as a connection for a multimode or single-mode optical fiber of the sensor, i.e. either the first optical fiber 24 or the second optical fiber 26 can be connected to the combined input / output interface 46.5.

[0114] If the single-mode fiber optic cable, i.e., the second fiber optic cable 26, is connected to the combined input / output interface 46.5, the multimode fiber optic cable, i.e., the first fiber optic cable 24 of the measuring probe 14, must be connected to the optional third input interface 46.3 to detect the fluorescence of the quantum emitter 28. The fluorescence is then forwarded to the output interface 46.4 via the optional seventh mirror 50.7. At this output interface 46.4, the fluorescence is in turn coupled into a preferably commercial fiber optic cable and forwarded, for example, to a fiber-coupled photodetector. Alternatively, the photodetector can also be installed directly at the location of the output interface 46.4.

[0115] With this measurement method, the optional optical separation element 58 can be used to further reduce stray light. This element divides the optional optical connection unit 16 into two optically separate areas, so that only excitation light is directed into one area and only detection light is directed into the other area. This allows stray light, particularly on the detection side, to be minimized.

[0116] Alternatively, the multimode optical fiber of the measuring probe, i.e., the first optical fiber 24, can be connected to the combined input / output interface 46.5. Excitation and detection are performed by the first optical fiber 24. The fluorescent light then travels along the third light guide path. It should be understood that the optional optical separation element 58 and the optional seventh mirror 50.7 are not installed for this purpose. The single-mode optical fiber of the measuring probe, i.e., the second optical fiber 26, is not required.

[0117] The fifth and sixth mirrors 50.5 and 50.6 serve to couple the fluorescent light into the fiber optic cable, which is connected to the output interface 46.4 and guides the fluorescent light to the detector. Alternatively, the detector can be connected directly to the output interface 46.4.

[0118] The optional third filter 52.3 preferably represents a long-pass filter, which filters out the excitation light that is also guided to the detector due to reflection or the like.

[0119] The fourth filter 52.4 represents, for example, a gray filter or the like.

[0120] Figure 6 schematically shows an alternative embodiment of the first optical fiber 24. This is a so-called coaxial design, in which the first electrical line 30 coaxially encloses the first optical fiber 24. The first optical fiber 24 is enclosed by an electrical insulation structure 60, which in turn is enclosed by the second electrical line 32. This allows the potential overall size of the measuring probe 14 to be further reduced.

[0121] Figure 7 schematically illustrates another configuration of a measuring probe 14. The measuring probe 14 has the two electrical leads 30, 32 and the two glass fibers 24, 26, which extend from the sleeve 36 and can be used for connection to measuring electronics, as described, for example, with reference to Figures 4 and / or 5. Furthermore, an elongated measuring head 62 is shown on the opposite side of the sleeve 36, which can be configured, for example, as described with reference to Figure 2.

[0122] The invention has been described in detail. One skilled in the art will recognize that, in particular, one or more of the following advantages can be achieved with the disclosed teachings.

[0123] The invention enables the construction of a miniaturized, fully integrated, fiber-based sensor or measuring probe based on quantum effects. In particular, a manufacturing method for creating such a measuring probe is disclosed. The complete integration of a fiber-based approach is particularly advantageous.

[0124] In particular, the method according to the invention enables improved deterministic positioning and fixation of nanoscopic quantum emitters on a suitable measurement platform using an additive manufacturing method, which is advantageous over simple adhesive bonds. The light, i.e., both excitation and detection light, can be specifically directed within the connection structure, and the quantum emitter can be specifically positioned and fixed on a measurement platform. Furthermore, the required RF field strength can be reduced by minimizing the distance between the quantum emitter and the RF antenna, as well as by specifically shaping the emitted field through the geometry of the RF antenna. This is preferably achieved using additive methods, in particular metallic direct laser writing with silver lacquer.

[0125] Furthermore, sensitivity can be increased by optically separating the excitation and detection beam paths. This leads, in particular, to an improvement in the signal-to-noise ratio by reducing autofluorescence. Furthermore, the disclosed system is stable against temperature fluctuations, since linear expansions can be essentially equalized by the connection to the light-conducting structures.

[0126] By minimizing and connecting all components required for the described sensor, such a sensor can be positioned flexibly and used as a measuring probe even in tight spaces.

[0127] By providing remote access to the measuring probe via a fiber optic cable for optical signals and an electrical antenna feed line for generating locally intense RF field strengths directly at the measuring probe or quantum emitter, a central measuring and computing unit can be used, which can be positioned at various measuring points of a device or similar.

[0128] List of reference symbols

[0129] 10 systems

[0130] 12 Evaluation and excitation device

[0131] 14 measuring probe

[0132] 16 Optical connection unit

[0133] 18 Optical excitation unit

[0134] 18a First laser light source

[0135] 18b Second laser light source

[0136] 20 evaluation unit

[0137] 20a Data acquisition unit

[0138] 20b Light sensor

[0139] 22 RF excitation unit

[0140] 24 First fiber optic

[0141] 26 Second fiber optic

[0142] 28 quantum emitters

[0143] 30 First electrical line

[0144] 32 Second electrical line

[0145] 34 RF antenna

[0146] 35 Static magnetic field source

[0147] 36 sleeve

[0148] 38 laser writing device

[0149] 40 drops

[0150] 42 First light guide structure

[0151] 44 Second light guide structure

[0152] 45 Object to be measured

[0153] 46a first interface 46b second interface

[0154] 46.1 to 46.3 Input interfaces

[0155] 46.4 Output interface

[0156] 46.5 Combined input / output interface 48 Electrical connections

[0157] 49 computers

[0158] 50.1 to 50.7 mirrors

[0159] 51.1 to 51.2 Beam superimposing element

[0160] 52.1 to 52.4 Filters 54.1 to 54.2 Wave plates

[0161] 55 Additional wave plate

[0162] 56.1 to 56.2 Polarizing beam splitter

[0163] 58 Optical separator

[0164] 60 Insulation structure 62 Measuring head

Claims

Patent claims 1. A method for producing a measuring probe (14), comprising the following steps: Inserting two glass fibers (24, 26) and two electrical lines (30, 32) into a sleeve (36); Filling the sleeve (36) with a carrier material, wherein the carrier material surrounds the glass fibers (24, 26) and / or electrical lines (30, 32) at least in sections; Curing the carrier material in the sleeve (36); Polishing one end of the glass fibers (24, 26), electrical lines (30, 32) and / or the carrier material accommodated in the sleeve (36); Arranging an RF antenna (34) on the tip; and Transferring a quantum emitter (28) to the tip; Laser writing a first and second optical fiber structure (42, 44) for optically connecting the quantum emitter (28) to the first glass fiber (24) and to the second glass fiber (26), wherein the first glass fiber (24) is optically decoupled from the second glass fiber (26).

2. Method according to claim 1, comprising the steps: Creating a suspension of a photoresist and the quantum emitter (28); Positioning the suspension on a carrier plate; and Positioning the carrier plate in a predefined position with respect to the polished end, wherein the above steps are carried out before the step of transferring the quantum emitter (28) to the tip.

3. Method according to one of the preceding claims, wherein the laser writing of a first and second optical fiber structure (42, 44) comprises laser writing by means of polymer lacquer from a first optical fiber structure (42) between a glass fiber core of the first glass fiber (24) and the quantum emitter (28) and from a second optical fiber structure (44) between a glass fiber core of the second glass fiber (26) and the quantum emitter (28), and the first optical fiber structure (42) preferably comprises an optical connection to the quantum emitter (28) which is perpendicular to an optical connection of the second optical fiber structure (44) to the quantum emitter (28).

4. Method according to one of the preceding claims, wherein The RF antenna (34) is arranged at the tip by means of an additive process, in particular by means of laser writing, and a material of the RF antenna (34) comprises a material compatible with the material of the electrical lines (30, 32); and the electrical lines (30, 32) and the material of the RF antenna (34) comprise in particular silver, copper and / or gold.

5. Method according to one of the preceding claims, comprising the steps of: adapting an impedance of the RF antenna (34) by a reflection measurement and adapting a length of the electrical lines (30, 32).

6. Method according to one of the preceding claims, comprising the step of: attaching a static magnetic field source (35), in particular a permanent magnet or a coil, in an environment of the tip for generating a static background magnetic field.

7. A measuring probe (14), preferably manufactured according to a method according to one of the preceding claims, comprising: a quantum emitter (28); an RF antenna (34); two glass fibers (24, 26); two electrical lines (30, 32), and a laser-scribed first light-guiding structure (42) for optically connecting the quantum emitter (28) to the first glass fiber (24) to form an optical feed line, and a laser-scribed second light-guiding structure (44) for optically connecting the quantum emitter (28) to the second glass fiber (26) to form a signal line; wherein the feed line and the signal line are optically decoupled; the signal line is designed to conduct a measurement signal away from the quantum emitter (28); and the feed line is designed to conduct an excitation signal to the quantum emitter (28).

8. Measuring probe (14) according to claim 7, wherein the measuring probe (14) comprises at least two further electrical lines and a further laser-scribed RF antenna.

9. Measuring probe (14) according to claim 7 or 8, wherein the measuring probe (14) comprises at least one further glass fiber which forms at least one further supply line and / or one further signal line.

10. A system (10) for measuring a temperature, a magnetic field, and / or an electric field, comprising: a measuring probe (14) according to one of claims 7 to 9; an optical excitation unit (18) for exciting a quantum emitter (28) of the measuring probe (14); an RF excitation unit (22) for generating an RF magnetic field by means of the RF antenna (34) of the measuring probe (14); an optional static magnetic field source (35) in the form of a permanent magnet or a coil; and an evaluation unit (20) for receiving and evaluating a measurement signal from the measuring probe (14) in response to excitation of the quantum emitter (28) of the measuring probe (14) by means of an optical excitation signal and by means of an RF magnetic field, wherein the evaluation unit (20) is designed to determine a temperature, a magnetic field and / or an electric field at a tip of the measuring probe (14), in particular at the quantum emitter (28), based on the measurement signal.

11. System (10) according to the preceding claim, with an optical connection unit (16) which is arranged between the optical excitation unit (18) and the measuring probe (14) and between the evaluation unit (20) and the measuring probe (14), wherein the optical connection unit (16) has a first input interface (46.1), a second input interface (46.2), an optional third input interface (46.3), an output interface (46.4) and a combined input / output interface (46.5); the first input interface (46.1) is designed to couple in a first excitation signal in the form of laser light of a first wavelength; the second input interface (46.2) is designed to couple in a second excitation signal in the form of laser light of a second wavelength; the third input interface (46.3) is designed to couple in a measuring signal; the output interface (46.4) is designed to output the measurement signal; the combined input / output interface (46.5) is designed to output the first excitation signal, the second excitation signal and / or to input the measurement signal; between the first input interface (46.1) and the combined input / output interface (46.5), a first light guide path is formed by a first mirror (50.1), a second mirror (50.2) and a first beam superimposing element (51.2), which preferably comprises a first wave plate (54.1), a first polarizing beam splitter (56.1) and a first filter (52.1);. between the second input interface (46.2) and the combined input / output interface (46.5), a second light guide path is formed by a third mirror (50.3), a fourth mirror (50.4), and a second beam-overlapping element (51.2), which preferably comprises a second waveplate (54.2), a second polarizing beam splitter (56.2), and a second filter (52.2); between the combined input / output interface (46.5) and the output interface (46.4), a third light guide path is formed by a fifth mirror (50.5) and a sixth mirror (50.6), which runs through the first beam-overlapping element (51.1) and the second beam-overlapping element (51.2), and preferably comprises a third filter (52.3) and a fourth filter (52.4); between the third input interface (46.3) and the output interface (46.4) a fourth light guide path through an optional seventh mirror (50.7), the fifth mirror (50.5) and the sixth mirror (50.6), which preferably has the third filter (52.3) and the fourth filter (52.4); an optional optical separating element (58) interrupts the third light guide path and shields the first light guide path and the second light guide path from the fourth light guide path; and the first light guide path, the second light guide path and the third light guide path have an optional further wave plate (55).

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