Integrated photonic tensor magnetometer

Abstract

Systems and embodiments for integrated photonic tensor magnetometers are described herein. In certain embodiments, a system includes a plurality of magnetometers. The system also includes a laser carrier wafer coupled to each magnetometer of the plurality of magnetometers that co-distributes one or more lasers to each magnetometer of the plurality of magnetometers. Additionally, the system includes a plurality of photodetectors that detect light emitted from the laser carrier wafer and the plurality of magnetometers. Furthermore, the system includes one or more processors that execute computer-executable instructions that cause the processor to monitor and control operation of the one or more lasers and calculate a magnetic field gradient based on the detected light from the magnetometers.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 62 / 976,208, filed on February 13, 2020, entitled “Integrated Photonic Tensor Magnetometer,” which is incorporated herein by reference. Background Technology

[0003] Many applications use sensing devices to measure the magnetic field tensor, which includes measurements of the vector field and its associated field gradient. Measuring the magnetic field gradient allows for the suppression of many sources of error and / or noise that can exist when only acquiring magnetic quantity values ​​or magnetic vector field measurements. Furthermore, measuring the magnetic field gradient allows for the determination of a wider variety of magnetic field distributions. Typically, a magnetic gradiometer can calculate the magnetic gradient using three or more measurements provided by a vector magnetometer, where each magnetic vector measurement is generated using three scalar magnetometers, each sensitive along an orthogonal axis. Therefore, nine or more scalar measurements can be used to generate the magnetic field gradient. Summary of the Invention

[0004] This document describes a system and implementation scheme for an integrated photonic tensor magnetometer. In some implementations, the system includes multiple magnetometers. The system also includes a laser carrier wafer coupled to each of the multiple magnetometers, the laser carrier wafer co-distributing one or more laser beams to each of the multiple magnetometers. Additionally, the system includes multiple photodetectors that detect light emitted from the laser carrier wafer and the multiple magnetometers. Furthermore, the system includes one or more processors executing computer-executable instructions that cause the processors to monitor and control the operation of one or more laser beams and calculate a magnetic field gradient based on the detected light from the magnetometers. Attached Figure Description

[0005] It should be understood that the accompanying drawings only illustrate some embodiments and should not be considered as limiting the scope. Exemplary embodiments will be described with additional features and details in the drawings, in which:

[0006] Figure 1 This is a block diagram illustrating an exemplary system for an integrated photonic tensor magnetometer according to one aspect of this disclosure;

[0007] Figure 2 This is an isometric view of a laser circuit wafer within an integrated photonic tensor magnetometer according to one aspect of this disclosure;

[0008] Figure 3is an isometric view of a vector magnetometer within an integrated photonic tensor magnetometer according to an aspect of the present disclosure; and

[0009] Figure 4 is a flowchart of a method for acquiring magnetic field gradient measurements using an integrated photonic tensor magnetometer according to an aspect of the present disclosure.

[0010] Conventions. The various features described may not necessarily be drawn to scale, and are shown by way of example and not limitation. DETAILED DESCRIPTION

[0011] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which are shown, by way of illustration, specific illustrative embodiments. It is understood that other embodiments can be utilized and logical, mechanical, and electrical changes can be made.

[0012] Systems and methods for integrated photonic tensor magnetometers are described herein. A device can measure a magnetic field tensor (i.e., a magnetic field gradient) by comparing vector components of magnetometers located at three or more different spatial locations. In some implementations, the magnetometers can be located at three separate locations, but coupled to different ports of a common laser carrier wafer. The laser carrier wafer can include waveguides or other optical structures that co-distribute one or more lasers to output ports through which the associated magnetometers receive the one or more lasers. The lasers are co-distributed when the lasers received by the magnetometers are produced by the same laser source and experience similar variations except for variations related to the unique connections between the laser carrier wafer and the magnetometers. The laser carrier wafer can also include various pick-off waveguides and / or additional ports for passing the lasers to various photodetectors to monitor noise, frequency, power, and other characteristics of the lasers propagating within the waveguides or provided by the laser carrier wafer.

[0013] In some embodiments, the magnetometers can use a combination of integrated photonic components such as waveguides, optical fibers, and free-space optics. Additionally, the magnetometers can include a combination of preparation or readout provided by either electrical components or optical components. One or more processors can use signals of the detected lasers to monitor operation of the lasers, control the lasers, and correct for intensity fluctuations and other errors that can arise during operation of the lasers. Additionally, the processors can calculate a magnetic vector field of the three or more magnetometers. The processors can then use differences in the magnetic vector fields to calculate a magnetic field gradient or magnetic tensor.

[0014] Figure 1is a block diagram of a system 100 for acquiring magnetic field gradient measurements using integrated photonic tensor magnetometers. As shown, the system 100 can acquire magnetic field gradient measurements using multiple magnetometers 103. As described herein, a magnetometer 103 can refer to a sensor that can acquire information about the strength of a magnetic field. The magnetometers 103 can be multiple scalar magnetometers that provide different measurements that are combined to form a vector measurement of the magnetic field, or the magnetometers 103 can be vector magnetometers that provide a vector measurement of the magnetic field. Additionally, the magnetometers can use received light to provide the magnetic field measurements. Some magnetometers 103, such as NV diamond based magnetometers, can detect vector components of a magnetic field within a single measurement region. The ability to detect vector components within a single region can allow smaller magnetometers 103 to have desirable functionality for many applications. Additionally, the magnetometers 103 with optical access for preparing or reading out measurements can further reduce weight and size when using integrated photonic elements.

[0015] In certain embodiments of the magnetometer 103 with optical access, the magnetometer 103 can refer to a sensor that uses changes in laser light to detect magnetic field strength and direction. For example, the magnetometer 103 can be fabricated using a material that absorbs light of a particular frequency, where the frequency of light absorption depends on the magnetic field experienced by the material. For example, nitrogen-vacancy diamond (NV diamond), silicon carbide with a defect center, or other materials can have the above sensitivity when subjected to a magnetic field. Examples of potential magnetometers using these materials are described in U.S. Non-Provisional Application Serial No. 16 / 786,495, filed February 10, 2020, entitled “QUANTUM VECTOR MAGNETOMETER BASED ON NANOSCALE FIN WAVEGUIDE” (hereinafter the “‘495 Application”), which claims the benefit of U.S. Provisional Application Serial No. 62 / 928,157, filed October 30, 2019, entitled “QUANTUM VECTOR MAGNETOMETER BASED ON NANOSCALE FIN WAVEGUIDE” (hereinafter the “‘157 Application”), both of which are hereby incorporated by reference herein. Additionally, examples of potential magnetometers using these materials are described in U.S. Non-Provisional Application Serial No. 16 / 788,819, filed February 12, 2020, entitled “INTEGRATED PHOTONICS QUANTUM VECTOR MAGNETOMETER” (hereinafter the “‘819 Application”), which claims the benefit of U.S. Provisional Application Serial No. 62 / 912,533, filed October 8, 2019, entitled “INTEGRATED PHOTONICS QUANTUM VECTOR MAGNETOMETER” (hereinafter the “‘533 Application”), both of which are hereby incorporated by reference herein.

[0016] In certain embodiments, the materials used to manufacture the magnetometers 103 can be sensitive to radio frequency (RF), as described in the '495 and '819 applications. Accordingly, the system 100 can include a plurality of individual RF sources 109, where each of the plurality of RF sources 109 is associated with an individual magnetometer 103. In particular, each of the RF sources 109 can expose the associated magnetometer 103 to a range of radio frequencies. The resonant frequency is the frequency at which the materials of the magnetometer 103 absorb light of a particular wavelength. Further, the resonant frequency varies based on the strength of the magnetic field experienced by the magnetometer 103. Accordingly, the range of frequencies of the RF energy provided by the RF source 109 to the associated magnetometer 103 can include the resonant frequency resulting from the expected range of magnetic field strengths of the magnetometer's 103 environment.

[0017] In some embodiments, each of the magnetometers 103 can be positioned spatially apart from one another. As the magnetometers 103 can take measurements at their respective locations by being located at different locations, the measurements of the individual magnetometers 103 can be used to calculate the magnetic gradient of the area spanned by the locations of the plurality of magnetometers 103. In some embodiments, the magnetometers 103 can be positioned relatively close to one another. Alternatively, the magnetometers 103 can be positioned at a greater distance from one another. When the magnetometers 103 are positioned close to one another, the sensitivity of the resulting magnetic gradient measurements can be limited. Additionally, the effect of noise on the measurements of the magnetic gradient measurements increases proportionally to the distance between the magnetometers 103. Accordingly, the different magnetometers can be placed a certain distance from one another to balance the sensitivity of the magnetic gradient and the effect of noise on the measurements of the different magnetometers 103.

[0018] In some embodiments, the system 100 can include one or more photodetectors 107 and one or more processors 105. In some embodiments, the photodetectors 107 can detect light produced by the magnetometers 103. For example, as discussed in the '495 and '819 patent applications, the magnetometers 103 can provide pump and probe lasers as output, where the intensity of the pump and probe lasers can be detected by the associated photodetectors 107. The photodetectors 107 can convert the detected pump and probe lasers into electrical signals for subsequent processing by the one or more processors 105.

[0019] As used herein, the processor 105 can be any computing device or circuit that can execute computer-readable instructions that cause the processor 105 to monitor the intensity of the probe laser detected by some of the photodetectors 107. Additionally, the instructions can cause the processor 105 to control the frequency of the RF energy emitted by the RF source 109. By detecting the intensity of the probe laser and controlling the frequency of the RF energy, the processor 105 can determine the frequency of the RF energy associated with the absorption of the probe laser. Using the information about the frequency of the RF energy, the processor 105 can calculate the magnetic field vectors measured by the different magnetometers 103. Additionally, using the calculated magnetic field vectors of the magnetometers 103 and information about the physical locations of the magnetometers 103 relative to each other, the processor 105 can also calculate the magnetic field gradient of the region between the locations of the magnetometers 103.

[0020] The processor 105 can be implemented using software, firmware, hardware, or other suitable combinations thereof. The processor 105 and / or other computing devices can be supplemented by, or incorporated into, specially designed application-specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs). The processor 105 and other computing devices can also include, or be supplemented by, software programs, firmware, or other computer-readable instructions or with them to perform various processing tasks, calculations, and control functions used in the methods and systems described herein.

[0021] Further, the methods described herein can be implemented by way of computer executable instructions, which are stored on a computer readable medium and which are executed by at least one processing device, such as the processor 105. Generally, programs that implement methods are pieces of code that are executable on the processing device. The software programs can be stored in any appropriate data storage device or computer readable media. The programs can be distributed over network coupled computer systems so that the programs are stored and executed in a distributed fashion. Language code can be created using any of a number of programming languages such as, for example, C, C++, Java, Visual Basic, Pascal, JavaScript, etc. Object oriented techniques can be used, and the methods can be implemented in a variety of ways, including procedure calls, web services, etc.

[0022] Suitable computer-readable storage media can include, for example, nonvolatile memory devices, including semiconductor memory devices, such as Erasable Programmable Read-Only Memory (EPROM), electrically Erasable programmable

[0023] As described above, the magnetometers 103 can be spatially located at different locations to provide the processor 105 with magnetic field measurements such that the magnetic field gradient of the area spanned by the magnetometers 103 can be measured. Because the magnetometers 103 are located at different locations, the performance of the system 100 in calculating the magnetic field gradient can be significantly reduced when the magnetometers 103 experience noise sources that are not common to the magnetometers 103 in the system 100. One potential noise source can be the independent light sources associated with the different magnetometers 103. Accordingly, the system 100 can include a laser carrier wafer 101. As described herein, the laser carrier wafer 101 can be a device that co-distributes laser beams from one or more laser sources to each of the magnetometers 103 in the system 100. For example, each of the magnetometers 103 can use light from a pump laser and a probe laser to detect a magnetic field as described in the '495 and '819 applications. Accordingly, the system 100 can include a single pump laser source and a single probe laser source, and the laser carrier wafer 101 can distribute light from the single pump laser and the single probe laser to each of the magnetometers 103 in the system 100. In some embodiments, the single pump laser can be a pump laser integrated cavity and the probe laser can be a probe laser integrated cavity, where the integrated cavities are formed on the laser carrier wafer 101 and are capable of generating laser light at a controlled frequency. Accordingly, noise sources affecting the laser light provided by the laser carrier wafer 101 can be substantially common before the laser light is provided to the magnetometers 103 because the laser light is co-distributed to the connected magnetometers.

[0024] In further embodiments, the laser carrier wafer 101 can provide a portion of the laser light to the photodetector 107. For example, the laser carrier wafer 101 can provide a portion of both the pump laser and the probe laser to the photodetector 107. The photodetector 107 can convert the detected light to an electrical signal and provide the electrical signal to the processor 105. The processor 105 can use the electrical signal representing the detected light to monitor and control the operation of the pump laser source and the probe laser source.

[0025] In certain embodiments, the processor 105 or other circuitry can monitor the provided electrical signals to identify noise unique to the different magnetometers 103 based on differences between the laser detected from the laser carrier wafer 101 and the laser detected from the different magnetometers 103. In addition, the processor 105 can also monitor the intensity and frequency of the laser detected from the laser carrier wafer 101 and the magnetometers 103. Further, for some magnetometers, such as NV diamond based magnetometers, the processor 105 can monitor the intensity of the light to identify the radio frequency emitted by the RF source 109 that causes the probe laser to be absorbed within the magnetometer 103. Based on the identified radio frequency, the processor 105 can calculate a vector measurement of the magnetic field at the location of the different magnetometer 103 and then use the calculated vector measurement to calculate a measurement of the magnetic field gradient of the area spanned by the magnetometer.

[0026] In example embodiments, the processor 105 can send control signals based on the monitored intensity and frequency of the laser to control the operation of the laser provided by the laser carrier wafer. For example, the processor 105 can detect whether the frequency of the laser source is deviating from a desired frequency or whether the intensity of the laser source is decreasing. In response, the processor 105 can change the frequency of the laser source to maintain the laser to the desired frequency. Further, the control signals from the processor 105 can increase or decrease the frequency of the laser based on the detected intensity of the laser. In addition, the processor 105 can remove the effects of the identified noise from the measurements from the magnetometers 103. Thus, the laser carrier wafer 101 in combination with the photodetector 107 and the processor 105 is able to reduce noise and other error sources in the laser provided to the magnetometers 103 in addition to making error sources common to the magnetometers 103.

[0027] Figure 2 is a detailed schematic view of an example embodiment of a laser carrier wafer 201. The laser carrier wafer 201 can function substantially similar to the laser carrier wafer 101 described above in connection with Figure 1 The laser carrier wafer 201 can distribute the laser provided from the laser source to the magnetometers 203-1, 203-2, and 203-3. For example, the laser carrier wafer 201 can include a pump laser source 211 and a probe laser source 221, which can be integrated cavities mounted on the laser carrier wafer 201. Alternatively, one or both of the pump laser source 211 and the probe laser source 221 can provide light coupled into the laser carrier wafer 201 for distribution to the magnetometers in combination with the laser carrier wafer 201.

[0028] As described in the '495 and '819 applications, the pump laser source 211 can provide a laser having a particular wavelength that optically excites point defects in the material used to manufacture the magnetometers 203-1, 203-2, and 203-3. When the point defects are optically excited, the laser can cause the point defects to undergo a spin-conserving transition from a ground triplet state to an excited triplet state. For example, when the material used to manufacture the magnetometers 203-1, 203-2, and 203-3 is NV diamond, a laser having a 532 nm wavelength can cause the point defects to undergo a spin-conserving transition from a ground triplet state to an excited triplet state.

[0029] In addition, the RF sources 209-1, 209-2, and 209-3, which function similarly to the RF source 109 described in connection with Figure 1 The RF sources 209-1, 209-2, and 209-3, which function similarly to the RF source 109 described in connection with the '495 and '819 applications, can expose the associated magnetometers 203-1, 203-2, and 203-3 to RF signals in a frequency range that includes the resonant frequency of the material of the magnetometers 203-1, 203-2, and 203-3. At the resonant frequency, the point defects in the material of the magnetometers 203-1, 203-2, and 203-3 in the excited state can relax to a shelved state through an inter-system crossing. In the shelved state, the point defects can absorb light having a particular wavelength. Accordingly, the laser carrier wafer 201 can also include a probe laser source 221 that provides a laser having the particular wavelength. When the material is NV diamond, the particular wavelength of the probe laser source 221 can be 1042 nm. The ability of the point defects to absorb the probe laser depends on the RF sources 209-1, 209-2, and 209-3 exposing the material to signals at the resonant frequency; the resonant frequency depends on the magnetic field experienced by the magnetometers 203-1, 203-2, and 203-3; and the sensitivity of the point defects to the magnetic field depends on the orientation of the point defects to the magnetic field. For example, in NV diamond, there are four potential defect orientations. The three Cartesian components of the vector field can be reconstructed from measurements of the magnetic field projections along the four defect orientations. Accordingly, the processor 105 can determine the magnetic field vector by measuring the intensity of the probe laser at RF frequencies in a range that includes the resonant frequencies of different point defects.

[0030] In certain embodiments, the laser carrier wafer 201 can route the probe laser provided by the probe laser source 221 and the pump laser provided by the pump laser source 211 to three or more magnetometers 203-1, 203-2, and 203-3. In some implementations, the laser carrier wafer 201 can use similar mechanisms to control the path of the pump laser and the probe laser through the laser carrier wafer 201. As shown, the laser carrier wafer 201 routes the pump laser and the probe laser to the magnetometers 203-1, 203-2, and 203-3, which are shown as abutting the laser carrier wafer 201. However, the magnetometers 203-1, 203-2, and 203-3 can acquire the light from the laser carrier wafer 201 using other means such as fiber optic cables, free space transmission, etc. However, different connections can introduce noise into the lasers, detrimentally affecting the operation of the tensor magnetometer.

[0031] In some embodiments, to control the path of the pump laser through the laser carrier wafer 201, the laser carrier wafer 201 can include a splitter 213 that splits the pump laser along a plurality of pump laser waveguide paths 249, where each pump laser waveguide path 249 is associated with a different waveguide on the laser carrier wafer 201 and routed through the different waveguide to an output port of the laser carrier wafer 201 for connection to one of the magnetometers 203-1, 203-2, and 203-3. Similarly, to control the path of the probe laser through the laser carrier wafer 201, the laser carrier wafer 201 can include a splitter 223 that splits the probe laser along a plurality of probe laser waveguide paths 251, where each probe laser waveguide path 251 is associated with a different waveguide on the laser carrier wafer 201 and routed through the different waveguide to an output port of the laser carrier wafer 201 for connection to one of the magnetometers 203-1, 203-2, and 203-3.

[0032] In further embodiments, the laser carrier wafer 201 can include a plurality of features that route the probe laser and the pump laser toward off-chip photodetectors, such as the photodetector 107 in FIG. 1. Figure 1 For example, the laser carrier wafer 201 can have a plurality of splitters that split the pump laser from one or more of the waveguides connected to the output ports of the laser carrier wafer 201. In particular, the splitters can couple light toward a vertical grating 215. When the pump laser is coupled into the vertical grating 215, the pump laser can be coupled away from the plane of the laser carrier wafer 201 toward a photodetector above the laser carrier wafer 201. Alternatively, instead of using a vertical grating 215, the pump laser can be routed to an additional output port that is connected to another photodetector or an on-chip photodetector.

[0033] In some embodiments, when light from the vertical grating 215 is incident on the photodetector, the photodetector can convert the light into an electrical signal and provide the electrical signal to a processor, such as the processor 105 in Figure 1 . The processor 105 can then monitor the electrical signal for intensity noise in the pump laser. Additionally, the processor 105 can adjust the performance of the electrical signal for noise in the pump laser. Furthermore, the noise in the pump laser can be coupled back into the pump laser in a negative feedback loop to remove the noise.

[0034] Additionally, the laser carrier wafer 201 can couple light towards a frequency monitor cavity and a cavity grating 219. The pump laser can be coupled into a resonant cavity before being incident on the cavity grating 219. As shown, the resonant cavity can include two mirrors 217 (a first mirror 217-1 and a second mirror 217-2) separated from each other by a particular distance that is associated with a particular wavelength. The mirrors 217 can be Bragg reflection gratings in a waveguide or some other type of mirror. Thus, when light is coupled into the cavity, light at the resonant frequency can pass through to the cavity grating 219. The cavity grating 219 can then couple the light away from the plane of the laser carrier wafer 201 towards a photodetector above the laser carrier wafer 201. Alternatively, the resonant light can be routed to an additional output port connected to another photodetector.

[0035] Furthermore, when light from the cavity grating 219 is incident on the photodetector, the photodetector can convert the light into an electrical signal indicative of the intensity of the light coupled out of the laser carrier wafer 201 by the cavity grating 219, where the electrical signal is provided to a processor, such as the processor 105 in Figure 1 . The processor 105 can then monitor the electrical signal to determine whether the pump laser is at the correct wavelength. If the processor 105 determines that the pump laser is not at the correct wavelength based on the intensity of the light received from the cavity grating 219, the processor 105 can adjust the wavelength of the pump laser so that the pump laser resonates between the first mirror 217-1 and the second mirror 217-2 and locks to the resonant frequency.

[0036] Similarly, the laser carrier wafer 201 can have a plurality of splitters that split out probe lasers from one or more of the waveguides connected to the output ports of the laser carrier wafer 201. In particular, the splitters can couple light towards a vertical grating 225. When the probe lasers are coupled into the vertical grating 225, the probe lasers can be coupled away from the plane of the laser carrier wafer 201 towards a photodetector above the laser carrier wafer 201. Alternatively, instead of using the vertical grating 225, the probe lasers can be routed to an additional output port connected to another photodetector.

[0037] In some embodiments, when light from the vertical grating 225 is incident on the photodetector, the photodetector can convert the light into an electrical signal and provide the electrical signal to a processor, such as the processor 105 in Figure 1 . The processor 105 can then monitor the electrical signal for noise in the probe laser. Additionally, the processor 105 can adjust the performance of the electrical signal for noise in the probe laser. Furthermore, the noise in the probe laser can be coupled back into the probe laser in a negative feedback loop to remove the noise.

[0038] Additionally, the laser carrier wafer 201 can couple light towards the frequency monitor cavity and the cavity grating 229. The probe laser can be coupled into a resonant cavity before being incident on the cavity grating 229. As shown, the resonant cavity can include two mirrors (first mirror 227-1 and second mirror 227-2) separated from each other by a particular distance that is associated with a particular wavelength. The mirrors 217 can be Bragg reflective gratings in a waveguide or some other type of mirror. Thus, when light is coupled into the cavity, light at the resonant frequency can pass through to the cavity grating 229. The cavity grating 229 can then couple the light away from the plane of the laser carrier wafer 201 towards a photodetector above the laser carrier wafer 201. Alternatively, the resonant light can be routed to an additional output port connected to another photodetector.

[0039] Furthermore, when light from the cavity grating 229 is incident on the photodetector, the photodetector can convert the light into an electrical signal indicative of the intensity coupled out of the laser carrier wafer 201 by the cavity grating 229, where the electrical signal is provided to a processor, such as the processor 105 in Figure 1 . The processor 105 can then monitor the electrical signal to determine whether the probe laser is at the correct wavelength. If the processor 105 determines that the probe laser is not at the correct wavelength based on the intensity of the light received from the cavity grating 229, the processor 105 can adjust the wavelength of the probe laser so that the probe laser resonates between the first mirror 227-1 and the second mirror 227-2 and locks to the resonant frequency.

[0040] As described above, the laser carrier wafer 201 can provide multiple lasers, such as the pump laser provided from the pump laser source 211 and the probe laser provided from the probe laser source 221, to any connected magnetometers, such as the magnetometers 203-1, 203-2, and 203-3. Additionally, the laser carrier wafer 201 can include mechanisms for monitoring the noise on the pump laser and the probe laser as well as the wavelengths of the pump laser and the probe laser. Thus, the laser carrier wafer 201 can provide lasers with both common noise and reduced noise to the output ports.

[0041] Figure 3is a schematic diagram of an exemplary vector magnetometer 303 within an integrated photonics tensor magnetometer. The vector magnetometer 303 can function similarly to the magnetometers described in the '495 and '819 applications. As shown, the vector magnetometer 303 can include a plurality of input ports for receiving light provided by the laser carrier wafer 201. For example, the vector magnetometer 303 can include a probe input port 347 and a pump laser input port 345. As described above, the vector magnetometer 303 can abut the associated laser carrier wafer 201. Alternatively, the vector magnetometer 303 can be connected to the associated laser carrier wafer 201 using other optical connections such as optical fibers, multi-core couplers, etc. In embodiments where the vector magnetometer 303 abuts the associated laser carrier wafer 201, the probe input port 347 and the pump laser input port 345 can be directly connected to associated probe output ports and pump output ports on the laser carrier wafer 201.

[0042] In some embodiments, the pump laser input port 345 and the probe input port 347 can each split onto separate waveguide paths, with a first path connecting the input port to an associated bare waveguide and a second path connecting the input port to an absorption region 343. In some embodiments, the pump laser and the probe laser can have significant overlap in the absorption region 343. As used herein, a bare waveguide refers to a waveguide having little or no overlap between the pump laser and the probe laser. For example, a second path connects the pump laser input port 345 and the probe input port 347 to the absorption region 343. As used herein, the absorption region 343 can refer to a region within the vector magnetometer 303 in which a first waveguide having a portion of the pump laser propagating therein and a second waveguide having a portion of the probe laser propagating therein extend adjacent to each other through a coupling length. Within the absorption region 343, the pump laser introduced into the first waveguide from the pump laser input port 345 couples into the second waveguide as described in the '495 and '819 applications.

[0043] In the presence of a resonant frequency signal, such as the resonant frequency signal provided by the RF source 109, the pump laser can condition point defects within the second waveguide throughout the absorption region 343 to absorb the probe laser such that the power of the probe laser propagating within the second waveguide experiences a power reduction as the probe laser propagates through the absorption region 343. To monitor the power of the probe laser after propagating through the absorption region 343, the vector magnetometer 303 can couple the waveguide having the probe laser propagating therein through a probe laser detection waveguide 339 to a probe laser detection photodetector 307-2. The probe laser detection photodetector 307-2 can provide a signal indicative of the power of the probe laser to a processor, such as the processor 305, which can determine a magnetic field based on the signal indicative of the power of the probe laser. Figure 1The processor 105 in the system 100 provides an electrical signal representing the intensity of the probe laser. The processor 105 can use the intensity of the probe laser and information describing the RF signal applied to the vector magnetometer 303 by the associated RF source 109 to calculate the magnetic field vector. Additionally, the processor 105 can monitor the power of the pump laser after propagating through the absorption region 343 by receiving an electrical signal from the photodetector 307-3, which can be coupled to the absorption region 343 through the pump laser detection waveguide 337.

[0044] Additionally, the vector magnetometer 303 can provide output to other photodetectors 307 for detecting other aspects of the operation of the vector magnetometer 303. For example, the vector magnetometer 303 can be connected to a pump laser detection photodetector 307-3 for detecting the intensity of the pump laser on a first waveguide, which is the waveguide connected to the pump laser input port 345. Additionally, the vector magnetometer 303 can connect photodetectors 307 to bare waveguides, such as the bare pump waveguide 335 and the bare probe waveguide 341 (collectively referred to herein as bare waveguides). For example, the bare pump waveguide 335 connects the pump laser input port 345 to a bare pump photodetector 307-4. Similarly, the bare pump waveguide 335 connects the probe input port 347 to a bare probe photodetector 307-1. Both the bare pump photodetector 307-4 and the bare probe photodetector 307-1 can provide electrical signals to a processor, such as the processor 105 in the system 100. The processor 105 can use the electrical signals provided from detecting light in the bare waveguides to normalize fluctuations in laser power, which can be different for different vector magnetometers 303 connected to the laser carrier wafer 201. For example, how a particular vector magnetometer 303 is connected to the laser carrier wafer 201 can introduce fluctuations specific to the vector magnetometer 303. By comparing different fluctuations on the connected magnetometer 303 along with the power measured from the laser carrier wafer 201, the processor 105 can normalize the operation of the laser on the vector magnetometer 303. Figure 1

[0045] Figure 4 ​is a flowchart of a method 400 for providing magnetic field gradient measurements using an integrated photon tensor magnetometer according to the embodiments described herein. The method 400 proceeds at 401, where one or more lasers are provided to a plurality of magnetometers by a laser carrier wafer. Additionally, the method 400 proceeds at 403, where a range of radio frequency signals are applied to the plurality of magnetometers. Moreover, the method 400 proceeds at 405, where operation of the one or more lasers is monitored at both the laser carrier wafer and the plurality of magnetometers. Additionally, the method 400 proceeds at 407, where operation of the one or more lasers is normalized based on the monitored operation. Moreover, the method 400 proceeds at 409, where a plurality of orientations of the magnetometers in the plurality of magnetometers are processed to acquire vector information at separate locations. Furthermore, the method 400 proceeds at 411, where a magnetic field gradient is calculated based on the monitored operation, the vector information, and the applied range of radio frequency signals.

[0046] Exemplary Embodiments

[0047] Example 1 includes a system comprising: a plurality of magnetometers; a laser carrier wafer coupled to each of the plurality of magnetometers, the laser carrier wafer co-distributing one or more lasers to each of the plurality of magnetometers; a plurality of photodetectors that detect light emitted from the laser carrier wafer and light emitted from the plurality of magnetometers; and one or more processors that execute computer-executable instructions that cause the one or more processors to monitor and control operation of the one or more lasers and calculate a magnetic field gradient based on the detected light from the plurality of magnetometers.

[0048] Example 2 includes the system of Example 1, further comprising a plurality of radio frequency sources that apply a range of radio frequency signals to each of the plurality of magnetometers.

[0049] Example 3 includes the system of any of Examples 1-2, wherein the one or more lasers are produced by: a pump laser source that produces pump laser light that is distributed to the plurality of magnetometers through a pump laser waveguide path; and a probe laser source that produces probe laser light that is distributed to the plurality of magnetometers through a probe laser waveguide path.

[0050] Example 4 includes the system of Example 3, wherein at least one of the pump laser source and the probe laser source is mounted on the laser carrier wafer.

[0051] Example 5 includes the system of any of Examples 3-4, wherein the laser carrier wafer includes a pump laser integrated cavity associated with the pump laser waveguide path and a probe laser integrated cavity associated with the probe laser waveguide path, wherein the pump laser integrated cavity is to maintain a wavelength of the pump laser at a resonant wavelength of the plurality of magnetometers and the probe laser integrated cavity is to maintain a probe laser wavelength at the resonant wavelength of the plurality of magnetometers.

[0052] Example 6 includes the system of any of Examples 1-5, wherein the laser carrier wafer includes a plurality of gratings to emit portions of the one or more lasers from the laser carrier wafer for detection by the plurality of photodetectors.

[0053] Example 7 includes the system of any of Examples 1-6, wherein one or more of the plurality of photodetectors detects the one or more lasers distributed to each of the plurality of magnetometers.

[0054] Example 8 includes the system of Example 7, wherein the one or more processors adjust measurements provided by the plurality of magnetometers based on the detected one or more lasers distributed to the plurality of magnetometers.

[0055] Example 9 includes the system of Example 8, wherein a magnetometer of the plurality of magnetometers passes a portion of the one or more lasers directly through an absorption region to a photodetector of the plurality of photodetectors.

[0056] Example 10 includes a method comprising: providing one or more lasers from one or more laser sources to a plurality of magnetometers through a laser carrier wafer; applying a range of radio frequency signals to the plurality of magnetometers; monitoring an operation of the one or more lasers provided to each of the plurality of magnetometers at both the laser carrier wafer and the plurality of magnetometers; normalizing an operation of the one or more laser sources based on the monitored operation; processing a plurality of orientations of a magnetometer of the plurality of magnetometers to acquire vector information at separate locations; and for each of the plurality of magnetometers, calculating a magnetic field gradient based on the monitored operation, the vector information, and the applied range of radio frequency signals.

[0057] Example 11 includes the method of Example 10, wherein the range of radio frequency signals is associated with an expected range of magnetic fields experienced by the plurality of magnetometers.

[0058] Example 12 includes the method of any of Examples 10-11, wherein providing the one or more lasers comprises: distributing a pump laser to the plurality of magnetometers through a pump laser waveguide path; and distributing a probe laser to the plurality of magnetometers through a probe laser waveguide path.

[0059] Example 13 includes the method of Example 12, wherein at least one of the one or more laser sources that generate the pump laser and the probe laser is mounted on a laser carrier wafer.

[0060] Example 14 includes the method of any of Examples 10-13, further comprising: causing at least one of the one or more lasers to resonate within an integrated cavity in the laser carrier wafer; detecting the resonant laser as an output from the integrated cavity; and controlling a frequency of the at least one laser based on the detected resonant laser.

[0061] Example 15 includes the method of any of Examples 10-14, wherein monitoring the operation of the one or more lasers at the laser carrier wafer includes: emitting a portion of the one or more lasers from one or more gratings; and detecting the emitted portion of the one or more lasers at one or more photodetectors.

[0062] Example 16 includes the method of any of Examples 10-15, wherein monitoring the operation of the one or more lasers at the plurality of magnetometers includes routing a received one of the one or more lasers directly through a bare waveguide to a photodetector.

[0063] Example 17 includes the method of Example 16, further comprising adjusting measurements provided by the plurality of magnetometers based on measurements of the one or more lasers distributed by the photodetector to the plurality of magnetometers.

[0064] Example 18 includes a system comprising: a plurality of magnetometers; a plurality of radio frequency sources that apply a range of radio frequency signals to each of the plurality of magnetometers; a laser carrier wafer coupled to each of the plurality of magnetometers, the laser carrier wafer providing one or more lasers to each of the plurality of magnetometers, wherein the laser carrier wafer comprises: one or more waveguide paths, wherein each of the one or more waveguide paths collectively distributes a laser of the one or more lasers to each of the plurality of magnetometers; one or more integrated cavities, wherein each of the one or more integrated cavities is associated with a waveguide path of the one or more waveguide paths and locks the laser distributed within the waveguide path to a resonant frequency; and a plurality of gratings to emit the one or more lasers from the one or more waveguide paths; a plurality of photodetectors that detect light emitted from the plurality of gratings from the laser carrier wafer and the plurality of magnetometers; and a processor that executes computer executable instructions that cause the processor to: control operation of the one or more lasers based on electrical signals received from the plurality of photodetectors; calculate a difference in light provided to the plurality of magnetometers; and calculate a magnetic field gradient based on the detected light from the plurality of magnetometers and the range of radio frequency signals applied to the plurality of magnetometers.

[0065] Example 19 includes the system of any of Examples 18, wherein the one or more lasers are produced by: a pump laser source that produces a pump laser that is distributed through a pump laser waveguide path to the plurality of magnetometers; and a probe laser source that produces a probe laser that is distributed through a probe laser waveguide path to the plurality of magnetometers.

[0066] Example 20 includes the system of any of Examples 18-19, wherein a magnetometer of the plurality of magnetometers passes a portion of a received laser of the one or more lasers directly through to a photodetector of the plurality of photodetectors for detection.

[0067] While specific embodiments have been illustrated and described herein, it will be appreciated that any arrangement devised to achieve the same purpose can be substituted for the specific embodiments shown. Therefore, it is evident that the present application has only been described in an illustrative fashion and not a restrictive one. The scope of the application should be determined only by the appended claims and equivalents thereof.

Claims

1. A system for an integrated photonic tensor magnetometer, the system comprising: Multiple magnetometers (103); A laser carrier wafer (101) is coupled to each of the plurality of magnetometers (103), the laser carrier wafer distributing one or more lasers to each of the plurality of magnetometers (103); Multiple photodetectors (107) detect light emitted from the laser carrier wafer (101) and light emitted from the multiple magnetometers (103); as well as One or more processors (105) execute computer-executable instructions that cause the one or more processors (105) to monitor and control the operation of the one or more lasers and to calculate a magnetic field gradient based on the light detected from the plurality of magnetometers (103).

2. The system of claim 1, wherein the one or more lasers are generated by: A pump laser source (211) generates a pump laser that is distributed to the plurality of magnetometers (103) via a pump laser waveguide path (249); and A probe laser source (221) generates probe laser light that is distributed to the plurality of magnetometers (103) through a probe laser waveguide path (251). The one or more processors (105) adjust the measurement results provided by the plurality of magnetometers (103) based on the detected one or more lasers distributed to the plurality of magnetometers (103).

3. A method for an integrated photonic tensor magnetometer, the method comprising: One or more lasers are supplied from one or more laser sources to multiple magnetometers (103) via a laser carrier wafer (101); A certain range of radio frequency signals are applied to the plurality of magnetometers (103); The operation of one or more lasers supplied to each of the plurality of magnetometers (103) at both the laser carrier wafer (101) and the plurality of magnetometers (103) is monitored; The operation of the one or more laser sources is normalized based on the monitored operation; and For each of the plurality of magnetometers (103), the magnetic field gradient is calculated based on the monitored operation and the range of the applied radio frequency signal.

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