Quantum Vector Magnetometer Based on Nanoscale Fin Waveguide

Abstract

The present invention relates to a device, which includes: a substrate and nanoscale fins, the substrate and the nanoscale fins being formed of a first material; an RF transmitter that is at an energy within a radio frequency range; and a waveguide that is formed of a second material. The device further includes a dual-color directional coupler configured to couple a pump laser and a probe laser into the waveguide. The waveguide is positioned along a coupling length adjacent to the nanoscale fins such that the pump laser propagating within the waveguide is coupled into the nanoscale fins along the coupling length due to evanescent wave overlap. When the energy emitted by the RF transmitter is at one or more frequencies that depend on a magnetic field, the pump laser causes the first material to absorb the probe laser. The device further includes a processor configured to determine a magnetic field strength of the magnetic field based on an identification of the one or more frequencies.

Description

Background Art

[0001] Many applications use precise measurements of magnetic fields. Specifically, applications attempt to measure vector magnetic field information to provide desired functionality within a system. For example, applications can measure magnetic fields in anomaly-based navigation and dipole beacon-based navigation. These applications typically require magnetic sensors with the following: high sensitivity; low size, weight, and power; and the ability to operate in the Earth's field. Some techniques (e.g., superconducting quantum interference devices (SQUIDs) or atom-based magnetometry) can provide high sensitivity that can be used for certain applications. However, some of these techniques have drawbacks. For example, SQUIDs use cryogenic refrigeration, which increases the size and power consumption of the magnetometer, and atom-based magnetometers cannot operate in the Earth's field. Additionally, the aforementioned techniques use at least three sensors to provide vector information. Summary of the Invention

[0002] In one example, a device includes: a substrate and nanoscale fins formed of a first material; a radio frequency (RF) transmitter that emits energy within the RF range; and a waveguide formed of a second material, where the waveguide is positioned on the nanoscale fins. The device also includes a dual-color directional coupler configured to couple a pump laser and a probe laser into the waveguide. The waveguide is positioned adjacent to the nanoscale fins along a coupling length such that the pump laser propagating within the waveguide couples into the nanoscale fins along the coupling length due to evanescent wave overlap. When the energy emitted by the RF transmitter is at one or more frequencies that depend on a magnetic field, the pump laser causes the first material to absorb the probe laser. The device also includes a processor configured to determine the magnetic field strength of the magnetic field based on the identification of the one or more frequencies that depend on the magnetic field. Brief Description of the Drawings

[0003] It should be understood that the drawings only show some embodiments and should not be considered as limiting the scope. The exemplary embodiments will be described with additional features and details using the drawings, in which:

[0004] Figure 1 is a diagram showing transitions between various states of a specific material for manufacturing a magnetometer;

[0005] Figure 2 is a graph showing magnetic field detection based on the identification of resonance lines in an applied microwave field;

[0006] Figure 3 is a diagram showing a waveguide structure that can be used to detect a magnetic field;

[0007] Figures 4A to 4Bis a graph showing the effect of different waveguide widths in a waveguide structure for detecting a magnetic field;

[0008] Figures 5A to 5B is a graph showing the effect of different separation distances between a waveguide and a substrate in a waveguide structure for detecting a magnetic field;

[0009] Figures 6A to 6C is a graph showing the effect of the position of the coupling length along a waveguide in a waveguide structure for detecting a magnetic field;

[0010] Figure 7 is a graph showing the effect of pump power on the probe transmission from a waveguide in a waveguide structure for detecting a magnetic field;

[0011] Figure 8 is a diagram of a waveguide system for detecting a magnetic field;

[0012] Figure 9 is a flowchart of an exemplary method for manufacturing a waveguide structure for detecting a magnetic field; and

[0013] Figure 10 is a flowchart of an exemplary method for manufacturing a waveguide structure for detecting a magnetic field.

[0014] By convention, the various features described are not necessarily drawn to scale, but are used to emphasize specific features relevant to the exemplary embodiments. Detailed Description

[0015] 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 exemplary embodiments. It is to be understood, however, that other embodiments may be utilized and logical, mechanical, and electrical changes may be made.

[0016] Systems and methods for an integrated photonic quantum vector magnetometer are provided herein. In some examples, the magnetometer includes a waveguide structure that includes a waveguide positioned on a nanoscale fin formed from a wafer. Light from a pump laser is coupled into the waveguide, and the pump laser is coupled into the nanoscale fin along a length where the waveguide and the nanoscale fin are in close proximity to each other. Additionally, in the presence of a microwave signal, light from a probe laser is coupled into the waveguide and the pump laser is coupled into the nanoscale fin. At a specific frequency of the microwave signal, the probe laser is absorbed by the material of the nanoscale fin, and based on one or more frequencies at which the probe laser is absorbed, a magnetic vector can be determined. The waveguide structures and systems described herein can be fabricated on a bulk wafer without the need for the more difficult thin film technology described in the '533 patent application.

[0017] Figure 1It is a diagram showing the transitions between various states of a specific material used to fabricate a magnetometer. For example, some materials may have certain physical properties that allow the material to respond to a magnetic field. For example, the first material can be nitrogen-vacancy (NV) diamond, silicon carbide with defect centers, or other materials with similar physical properties. As used herein, NV diamond can refer to a diamond material having multiple point defects, where the point defects include a nearest neighbor pair of a nitrogen atom substituting for a carbon atom and a lattice vacancy.

[0018] As shown in the figure, the first material can have a ground state that is a spin triplet. Specifically, the ground state can have multiple spin projections: a ground anti-parallel spin 101 of spin projection 0 and a ground parallel spin 103 of spin projections about + / -1, where the ground anti-parallel spin 101 and the ground parallel spin 103 are separated by a resonance frequency 121. For example, in the absence of a magnetic field, when the first material is NV diamond, the resonance frequency can be equal to 2.87 GHz. Additionally, the point defects within the first material can be optically excited to a spin triplet excited level through a spin-conserving transition, where the triplet excited level also has multiple spin projections: an excited anti-parallel spin 105 of spin projection 0 and an excited parallel spin 107 of spin projections about + / -1. To optically excite the point defects, the first material can be exposed to pump light having a specific frequency. For example, in NV diamond, a laser with a wavelength of 532 nm can cause a spin-conserving transition from the ground triplet to the excited triplet.

[0019] When the point defects within the first material are in the excited state, the defects can relax either through a radiative transition 115 or through an intersystem crossing 117. When the point defects relax through the radiative transition 115, the point defects can fluoresce and return to the ground triplet. For example, NV diamond point defects can emit light with a wavelength of 637 nm during the radiative transition 115. When the point defects relax through the intersystem crossing 117, the point defects will not fluoresce and will transition to a shelved state, where the shelved state can be a shelved ground state 111 or a shelved excited state 109. Additionally, when the point defects are in one of the shelved states 109 and 111, the point defects can absorb a probe laser 119 having a specific frequency. For example, NV diamond point defects in the shelved states 109 and 111 can absorb a probe laser 119 with a wavelength of 1042 nm.

[0020] In some examples, a microwave frequency can be applied to the first material to increase the rate of intersystem crossing 117 compared to radiative transition 115. In the first material, non-radiative intersystem crossing 117 can be strongly spin-selective. For example, point defects with parallel spins 107 are more likely to undergo intersystem crossing 117 to metastable states 109 and 111. In contrast, point defects with excited anti-parallel spins 105 are more likely to undergo a radiative transition back to the ground triplet state. To increase the probability of intersystem crossing, a microwave frequency equal to the resonant frequency of the first material can be applied to the first material. For example, when the first material is NV diamond, the resonant frequency can be 2.87 GHz. Thus, applying a radio frequency of 2.87 GHz to the first material can increase the probability of intersystem crossing 117 to metastable states 109 and 111.

[0021] Additionally, when a microwave signal at the resonant frequency is applied to the first material, the probe laser 119 is more likely to be absorbed by the first material because the population of point defects in metastable states 109 and 111 within the first material is greater than when the first material is not exposed to RF energy at the resonant frequency. Thus, when the probe laser 119 is applied to the first material in the absence of a microwave signal at the resonant frequency, the probe laser 119 is absorbed by the first material at a lower frequency. For example, when the NV diamond material is exposed to a microwave signal with a resonant frequency of 2.87 GHz, the NV diamond material can begin to absorb the probe laser 119 with a wavelength of 1042 nm at an increased rate.

[0022] In some examples, the resonant frequency of the first material can be changed in the presence of a magnetic field. For example, when the first material is exposed to a magnetic field, the Zeeman effect can cause the resonant frequency to undergo a shift that is proportional to the strength of the magnetic field experienced. Specifically, in the presence of a magnetic field, the resonant frequency can split into two different resonant frequencies, where the difference between the two resonant frequencies is proportional to the magnetic field experienced. Thus, the resonant frequency at which point defects in the first material absorb the probe laser 119 can be monitored to determine the strength of the magnetic field experienced by the first material.

[0023] Additionally, point defects within the first material can be in one of a plurality of different orientations. For example, when the first material is NV diamond, each point defect can be in one of four different orientations. Additionally, the first material can have many point defects in each of the four different orientations. Thus, when the probe laser 119 is applied to the first material, vector information of the magnetic field can be extracted from the first material. For example, when the first material is exposed to a magnetic field, the resonance frequency of the point defect can shift based on the orientation of the point defect relative to the magnetic field experienced. Thus, when the point defects in the first material are in a plurality of different orientations, the point defects in the first material can have individual resonance frequencies associated with each of the different orientations of the point defects. Thus, the vector information of the magnetic field can be determined by identifying which resonances correspond to the different orientations of the point defects in the first material. In some examples, a bias magnetic field can be applied to the first material to assist in determining which resonance frequencies are associated with a particular orientation of the point defect.

[0024] In the examples described herein, the first material can be incorporated within a magnetometer that exposes the first material to pump light 113 to cause point defects within the first material to move to the excited triplet state. The magnetometer can also expose the first material to RF energy within a frequency range that includes the resonance frequency 121 of the first material, where the probability of intersystem crossing 117 to the shelving states 109 and 111 increases at the resonance frequency 121, as described above. Additionally, the first material can be exposed to the probe laser 119, where the probe laser 119 is absorbed by the point defects in the shelving states 109 and 111. Thus, the applied microwave signal can sweep through a range of frequencies to identify the resonance frequencies associated with the different orientations of the point defects within the first material. The resonance frequencies can be identified when the intensity of the applied probe laser 119 passing through the first material decreases (thereby indicating that the applied probe laser 119 is absorbed by the point defects within the first material). Based on the identified resonance frequencies, the magnetic field experienced by the first material can be calculated by: high sensitivity to magnetic field changes; low size, weight, and power; and robustness that enables the resulting magnetometer to be used in many magnetically / auxiliary-based applications such as in navigation.

[0025] Figure 2 is a graph showing magnetic field detection based on the identification of resonance lines in an applied microwave field that sweeps through a range of frequencies. As described above, the first material can be exposed to a range of microwave frequencies, where the applied frequency range includes the different resonance frequencies of the first material. Additionally, the different resonance frequencies are associated with the strength of the magnetic field experienced by the first material. Additionally, the first material can have different resonance frequencies associated with the different orientations of the point defects within the first material.

[0026] As shown in the figure, Figure 2Shows various graphs of the intensity of the probe laser emitted from a first material at different microwave frequencies for three different magnetic field strengths. For example, graph 201 shows the intensity of the probe laser emitted when the first material is not exposed to a magnetic field at different frequencies. When light from the probe laser is coupled into the first material in the absence of an applied magnetic field, the first material may not experience a Zeeman shift, and the probe laser may be absorbed at the single resonance frequency of the first material. Accordingly, the intensity of light 201 may decrease at the single resonance frequency of the first material.

[0027] Additionally, when the first material is exposed to different magnetic field strengths, the resonance frequency may experience a frequency shift that is proportional to the magnetic field strength experienced. For example, graphs 205 and 203 show the intensity of the probe laser emitted by the first material in the presence of different magnetic field strengths. For example, the magnetic field strength experienced by the first material associated with graph 203 is greater than the magnetic field strength experienced by the first material associated with graph 205. Accordingly, when the first material is exposed to a greater magnetic field strength, the magnitude of the shift in the resonance frequency is greater. To identify the magnitude of the shift in the resonance frequency, the system may identify the frequency 207 associated with a decrease in the intensity of the probe laser emitted by the first material. Based on the magnitude of the shift in the resonance frequency, the system may determine the magnetic field experienced by the point defect. Additionally, when there are multiple resonance frequencies, the system may identify the orientation of the point defect and the direction of the magnetic field experienced associated with the different resonance frequencies.

[0028] Figure 3 is a diagram showing a waveguide structure 300 that can be used within a system for detecting a magnetic field. In Figure 3 the example shown, the waveguide structure 300 includes a substrate 301, nanoscale fins 302, and a waveguide 304. In some examples, the waveguide structure 300 includes a cladding material (not shown) that fills the empty space between the substrate 301, nanoscale fins 302, and waveguide 304 shown. Figure 3 the empty space between the substrate 301, nanoscale fins 302, and waveguide 304 shown.

[0029] In some examples, the substrate 301 and the nanoscale fins 302 are formed of the first material described above. For example, the nanoscale fins 302 can be formed in an NV diamond substrate or other similar material using the following techniques. In some examples, the waveguide 304 is formed of a second material different from the first material. The waveguide 304 is transparent at the pump wavelength and the probe wavelength and has a sufficiently high refractive index so that it supports the pump optical mode and the probe optical mode. In an example where the first material is NV diamond, the second material is transparent at the pump wavelength (532nm) and the probe wavelength (1042nm) discussed above. In such examples, the refractive index of the second material should be greater than or equal to 2, and the refractive index will preferably be about 2.4 or higher. In some examples, the second material is titanium dioxide, silicon nitride, or another material that meets the above parameters.

[0030] The nanoscale fins 302 serve multiple purposes of the waveguide structure 300. The nanoscale fins 302 serve to separate the optical modes propagating in the waveguide 304 from the substrate 301. If the optical modes (pump mode and probe mode) are too close to the substrate 301, the light may radiate downward through the nanoscale fins 302 to the substrate 301. In order to provide sufficient spacing between the optical modes and the substrate 301, the height of the nanoscale fins 302 must be above a threshold height. In some examples, the height of the nanoscale fins 302 is about 3 microns or more.

[0031] In addition, the nano-scale fin 302 is the same as above. Figure 1 The absorption of the pump laser and the probe laser occurs in the waveguide structure 300. In some examples, the waveguide 304 is positioned near the top surface of the nanoscale fin 302 so that light propagating through the waveguide 304 is coupled into the nanoscale fin 302 due to evanescent wave overlap. For example, light from the pump laser may be coupled into the waveguide 304, and the pump laser is coupled from the waveguide 304 into the nanoscale fin 302 due to evanescent wave overlap. In some examples, the pump laser is configured to emit light at the frequency of the above-mentioned pump laser. For example, when the nanoscale fin 302 is formed of NV diamond, the pump laser may be a laser configured to emit light having a wavelength of 532 nm. Therefore, as the pump laser is coupled from the waveguide 304 into the nanoscale fin 302 due to evanescent wave overlap, the pump laser may cause point defects within the nanoscale fin 302 to be converted into excited triplet states.

[0032] In some examples, light from a probe laser is coupled from a laser source into the waveguide 304. The probe laser may emit light having a wavelength that is absorbed by point defects in a resting state within the first material. For example, when the nanoscale fin 302 is made of NV diamond, the light from the probe laser may have a wavelength of 1042 nm.

[0033] When the waveguide structure 300 is exposed to a signal having the resonant frequency of the first material, the pump laser coupled into the waveguide 304 and gradually coupled into the nanoscale fins 302 due to evanescent wave overlap can cause point defects within the nanoscale fins 302 to move to a shelved state. As the pump laser is gradually coupled into the nanoscale fins 302 along the coupling length between the nanoscale fins 302 and the waveguide 304, in the presence of a signal having the resonant frequency of the first material, the point defects can absorb the probe laser along the coupling length. Additionally, since the resonant frequency of the first material changes when exposed to a magnetic field, the frequency of the applied signal can be changed to identify the frequency at which the point defects within the nanoscale fins 302 absorb the probe laser. As described above, different identified frequencies can be identified to determine the magnitude and direction of the magnetic field.

[0034] Although the waveguide 304 appears to be uniform in Figure 3 this figure, it should be understood that this is for illustrative purposes. In some examples, the physical characteristics of the waveguide 304 (e.g., width) and the relationship between the waveguide 304 and the substrate 301 and / or the nanoscale fins 302 can be modified such that the pump laser is gradually coupled from the waveguide 304 into the nanoscale fins 302 due to evanescent wave overlap. In some examples, the width of the waveguide 304 is changed such that the pump laser is gradually coupled into the nanoscale fins 302 along the coupling length where the nanoscale fins 302 and the waveguide 304 are close to each other. In some examples, the physical relationship between the waveguide 304 and the substrate 301 and the nanoscale fins 302 is changed such that the pump laser is gradually coupled into the nanoscale fins 302 along the coupling length where the nanoscale fins 302 and the waveguide 304 are close to each other. Additionally, in some examples, the pump laser is substantially coupled into the nanoscale fins 302 such that the pump laser no longer propagates within the waveguide 304 after the coupling length of the nanoscale fins 302 and the waveguide 304. By gradually coupling the pump laser from the second waveguide 304 into the nanoscale fins 302 due to evanescent wave overlap, the amount of point defects transformed into the excited triplet state within the nanoscale fins 302 increases.

[0035] As discussed with respect to Figure 3 the use of the waveguide structure 300 increases the interaction length of light within the first material. As discussed above, both the pump laser and the probe laser propagate within the waveguide. When the nanoscale fins 302 and the waveguide 304 are used, the pump laser can be slowly coupled into the nanoscale fins 302 due to evanescent wave overlap. Specifically, the rate at which the pump laser is absorbed by the first material is faster than the rate at which the probe laser is absorbed by the first material.

[0036] By slowly leaking the pump laser into the nanoscale fins 302, the waveguide structure 300 can provide increased absorption of the probe laser, resulting in greater contrast and efficient absorption of the pump laser along the coupling length between the nanoscale fins 302 and the waveguide 304. As described below, light can be slowly coupled from the waveguide 304 into the nanoscale fins 302 in such a way that the pump laser has a substantially constant intensity over the entire coupling length of the nanoscale fins 302.

[0037] Figures 4A to 4B is a graph showing the effect of different widths of waveguides in a waveguide structure (such as Figure 3 the waveguide structure 300 in ) on the detection of a magnetic field. In Figure 4A it shows the various coupling coefficients of the pump mode propagating in waveguides made of a second material with different widths. For example, graph 401 shows the pump mode coupling coefficients of the waveguide and the nanoscale fins for various widths of the waveguide of the waveguide structure. In Figure 4B it shows the various coupling coefficients of the probe mode propagating in the waveguide 304 made of a second material with different widths. For example, graph 402 shows the probe mode coupling coefficients of the waveguide and the nanoscale fins for various widths of the waveguide of the waveguide structure. As can be seen from Figures 4A to 4B the overall trend of the pump mode coupling coefficient with respect to the waveguide width is similar to the overall trend of the probe mode coupling coefficient with respect to the waveguide width.

[0038] Figure 5A is a graph showing the effect of different separation distances between the substrate and the waveguide in a waveguide structure (such as Figure 3 the waveguide structure 300 in ) on the detection of a magnetic field. In Figure 5A it shows the various coupling coefficients of the pump mode propagating in a 0.6 μm wide waveguide 304 made of a second material and separated from the substrate by various distances. For example, graph 501 shows the pump mode coupling coefficients of the waveguide and the nanoscale fins for various separation distances between the substrate and the waveguide of the waveguide structure.

[0039] Figure 5B is a graph showing the effect of different separation distances between the substrate and the waveguide in a waveguide structure (such as Figure 3 the waveguide structure 300 in ) on the detection of a magnetic field. In Figure 5BIn it, various coupling coefficients of the probe mode propagating in a waveguide 304 with a width of 0.6 μm made of a second material and separated from the substrate by various distances are shown for various pump powers. For example, graph 502 shows the probe mode coupling coefficient between the waveguide and the nanoscale fin when the pump power is 8 mW, graph 503 shows the probe mode coupling coefficient between the waveguide and the nanoscale fin when the pump power is 4 mW, graph 504 shows the probe mode coupling coefficient between the waveguide and the nanoscale fin when the pump power is 2 mW, and graph 505 shows the probe mode coupling coefficient between the waveguide and the nanoscale fin when the pump power is 1 mW. As can be seen from Figures 5A to 5B it, the overall trend of the pump mode coupling coefficient with respect to the separation distance is similar to the overall trend of the probe mode coupling coefficient with respect to the separation distance.

[0040] As Figures 4A to 5B shown, the rate at which light couples from waveguide 304 to nanoscale fin 302 along the coupling length of waveguide structure 300 depends on both the lateral width of waveguide 304 and the vertical distance between the substrate and waveguide 304 (the height of the nanoscale fin). Thus, in order to control the rate at which light couples from waveguide 304 to nanoscale fin 302 along the coupling length of the waveguide structure, the width of waveguide 304 and / or the distance between substrate 301 and waveguide 304 (the height of nanoscale fin 302) can be varied along the coupling length.

[0041] Figures 6A to 6C Graphs are shown depicting the influence of different positions along the coupling distance of the waveguide in a waveguide structure (such as the waveguide structure 300 in Figure 3 ) for detecting a magnetic field. In Figure 6A , various coupling coefficients of the pump mode propagating at various positions along the coupling length of the waveguide in a waveguide 304 made of a second material are shown. For example, graph 601 shows the pump mode coupling coefficient between the waveguide and the nanoscale fin along the coupling length of the waveguide of the waveguide structure. In Figure 6B , various coupling coefficients of the probe mode propagating at various positions along the coupling length of the waveguide in a waveguide 304 made of a second material are shown. For example, graph 602 shows the probe mode coupling coefficient between the waveguide and the nanoscale fin along the coupling length of the waveguide of the waveguide structure when the pump power is 8 mW.

[0042] Figure 6C Graphs are shown depicting the variation of the distance between substrate 301 and waveguide 304 along the coupling length of waveguide 304 such that the pump absorption in the nanoscale fin is uniform. For example, graph 603 shows the separation distance between substrate 301 and waveguide 304 decreasing along the coupling length of waveguide 304 such that the absorption of the pump laser in the nanoscale fin is uniform.

[0043] Figure 7 is a graph showing the effect of pump power on the probe transmission of a waveguide in a waveguide structure (such as Figure 3 the waveguide structure 300 in Figure 7 . In

[0044] Figure 8 is a diagram of a waveguide system 800 that can be used to detect a magnetic field. In Figure 8 the example shown, the waveguide system 800 includes a waveguide structure 802, which includes similar features as described above with respect to the waveguide structure 300, which was described above with respect to Figure 3 . In some examples, the waveguide system 800 includes an absorption region 801. As used herein, the absorption region 801 may refer to a region within the waveguide system 800 where the nanoscale fins and the waveguide of the waveguide structure 802 extend close to each other through a coupling length such that the pump laser 807 and the probe laser 809 introduced into the waveguide from a pump laser source and a probe laser source, respectively, are coupled into the nanoscale fins due to evanescent wave overlap as described above.

[0045] In some examples, the pump laser 807 and the probe laser 809 are coupled into the waveguide 802 via a dichroic directional coupler 806. In the presence of a resonant frequency signal, the probe laser 809 can be absorbed by point defects within the nanoscale fins, such that the power of the light received from the waveguide is reduced. To monitor the power of the probe laser 809 within the waveguide, the waveguide system 800 includes a filter 815. In some examples, the filter 815 is coupled to the waveguide structure 802 and is configured to receive light from the waveguide after the light has passed through the absorption region 801. In some examples, the filter 815 is configured to reflect light at the frequency of the probe laser 809 through a reflection port 813 and allow light at other frequencies (such as the frequency of the pump laser 807 or the fluorescence frequency) to pass through to a filter output port 811. The remaining pump laser 807 (if any) passes through the filter output port 811 after leaving the absorption region 801. In some examples, the power of the pump laser 807 at the filter output port 811 may be substantially equal to or close to zero, since most of the pump laser 807 can be coupled into the nanoscale fins in the absorption region 801.

[0046] In some examples, light at the reflection port 813 is coupled to a light detection device (such as a photodetector or a camera), which is configured to monitor the intensity of the received light. During operation, microwave radiation may be emitted around the absorption region 801, where the microwave radiation sweeps through a range of frequencies including the possible resonance frequencies of the first material. The light detection device may monitor the light received from the reflection port 813 and provide a signal associated with the intensity of the received light. In some examples, a processor (not shown) is configured to receive the signal from the light detection device and, when measuring the intensity of the received light, associate the intensity of the received light with the frequency of the microwave radiation applied to the absorption region 801. In some examples, the processor is configured to execute computer-executable instructions that identify the applied frequency associated with a decrease in light intensity. In some examples, the processor may determine the identified frequency as the resonance frequency and calculate the magnitude and direction of the magnetic field applied to the absorption region 801.

[0047] Figure 9 An exemplary method 900 for fabricating a waveguide structure for detecting a magnetic field is shown. The method begins by forming nanoscale fins in a wafer formed of a first material (block 902). In some examples, the first material may be nitrogen-vacancy (NV) diamond, silicon carbide, or other materials having similar physical properties. As used herein, NV diamond may refer to a diamond material having a plurality of point defects, where the point defects include a nearest neighbor pair of a nitrogen atom substituting for a carbon atom and a lattice vacancy.

[0048] In some examples, forming nanoscale fins in the wafer includes etching the wafer using, for example, reactive ion etching. In such examples, photolithography techniques may be used to prepare the wafer for etching. In some examples, the wafer is prepared by depositing a photoresist layer on the wafer; patterning the photoresist layer using photolithography (such as electron beam lithography or UV lithography); and developing the photoresist layer. Once the nanoscale fins are sufficiently formed after reactive ion etching, any remaining photoresist is removed.

[0049] Method 900 continues by depositing a cladding material over the nanoscale fins (block 904). In some examples, the cladding material has a lower refractive index (such as silica) compared to the wafer. In some examples, the cladding material is deposited using chemical vapor deposition or atomic layer deposition. In some examples, chemical mechanical polishing is used to polish the cladding material to prepare the cladding material for further manufacturing steps. In some examples, the cladding material is polished until the top surface of the nanoscale fins is exposed.

[0050] Method 900 continues with forming a waveguide on the nanoscale fins (block 906). In some examples, the waveguide is formed of a second material different from the first material. The waveguide is transparent at the pump wavelength and the probe wavelength and has a refractive index high enough such that it supports a pump optical mode and a probe optical mode. In an example where the first material is NV diamond, the second material is transparent at the pump wavelength (532 nm) and the probe wavelength (1042 nm) discussed above. In such examples, the refractive index of the second material should be greater than or equal to 2, and the refractive index will preferably be about 2.4 or higher. In some examples, the second material is titanium dioxide, silicon nitride, or another material meeting the above parameters.

[0051] In some examples, forming the waveguide includes using, for example, reactive ion etching. In such examples, photolithography techniques can be used to prepare the waveguide material for etching. In some examples, the waveguide material is prepared by depositing a photoresist layer on the waveguide material layer; patterning the photoresist layer using photolithography (e.g., electron beam lithography or UV lithography); and developing the photoresist layer. In some examples, the photoresist layer is removed after reactive ion etching.

[0052] Method 900 continues with depositing a cladding material over the waveguide in a manner similar to that described above with respect to block 904 (block 908).

[0053] In some examples, method 900 continues with coupling a probe laser source and a pump laser source to the waveguide (block 910). For example, the probe laser source can be coupled to the waveguide and configured to emit a probe laser into the waveguide, and the pump laser source can be coupled to the waveguide and configured to emit a pump laser into the waveguide when the nanoscale fins are exposed to one or more resonant frequencies of the first material such that the first material absorbs the wavelength of the probe laser. In some examples, the probe laser source and the pump laser source are coupled to the waveguide using optical fibers and a dichroic directional coupler. In such examples, the probe laser source and the pump laser source are coupled to respective optical fibers, and then these optical fibers are coupled to the dichroic directional coupler. The dichroic directional coupler oscillates the light from the probe laser source and the pump laser source such that substantially all of the light from the probe laser source and the pump laser source is coupled into the waveguide.

[0054] Figure 10 An exemplary method 1000 for fabricating a waveguide structure for detecting a magnetic field is shown, and cross-sections of the waveguide structure during various steps of method 1000 are depicted.

[0055] In various aspects, system elements, method steps, or examples (e.g., processors) described throughout this disclosure may be implemented on one or more computer systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), or similar devices that include hardware-executable code for implementing those elements, processes, or examples, with the code stored on a non-transitory data storage device. These devices include software programs, firmware, or other computer-readable instructions for performing various methods, process tasks, calculations, and control functions for synchronization and fault management in a distributed antenna system, or operating in conjunction with software programs, firmware, or other computer-readable instructions.

[0056] These instructions are typically stored on any suitable computer storage medium for storing computer-readable instructions or data structures. Computer-readable media can be implemented as any available medium accessible by a general or special-purpose computer or processor or any programmable logic device. Suitable processor-readable media can include storage or memory media, such as magnetic or optical media. For example, storage or memory media can include conventional hard disks, compact disc-read only memory (CD-ROM), volatile or non-volatile media such as random access memory (RAM) (including, but not limited to, synchronous dynamic random access memory (SDRAM), double data rate (DDR) RAM, RAMBUS dynamic RAM (RDRAM), static RAM (SRAM), etc.), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), and flash memory, among others. Suitable processor-readable media can also include transmission media (such as electrical, electromagnetic, or digital signals) transmitted via a communication medium (such as a network and / or wireless link).

[0057] The methods and techniques described herein can be implemented in digital electronic circuitry or in firmware, software, or a combination thereof for a programmable processor, e.g., a special purpose processor or a general purpose processor such as a computer. Apparatus embodying these techniques may include appropriate input and output devices, a programmable processor, and a storage medium tangibly embodying program instructions for execution by the programmable processor. The processes embodying these techniques may be performed by a programmable processor executing an instruction program to perform the desired functions by operating on input data and generating output. These techniques may advantageously be implemented in one or more programs executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. In general, a processor will receive instructions and data from a read only memory and / or a random access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of nonvolatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and DVD disks. Any of the foregoing may be supplemented or incorporated in specially designed application specific integrated circuits (ASICs).

[0058] Exemplary embodiments

[0059] Embodiment 1 includes an apparatus that includes: a substrate and nanoscale fins formed of a first material; a radio frequency emitter configured to emit energy in a radio frequency range; a waveguide formed of a second material; a dichroic directional coupler configured to couple a pump laser and a probe laser into the waveguide, wherein the waveguide is positioned along a coupling length adjacent to the nanoscale fins such that the pump laser propagating within the waveguide is coupled into the nanoscale fins along the coupling length due to evanescent wave overlap, wherein when the energy emitted by the radio frequency emitter is at one or more frequencies that depend on a magnetic field, the pump laser causes the first material to absorb the probe laser; and a processor configured to determine a magnetic field strength based on an identification of the one or more frequencies that depend on the magnetic field.

[0060] Embodiment 2 includes the apparatus according to Embodiment 1, wherein the first material includes nitrogen vacancy diamond.

[0061] Embodiment 3 includes the apparatus according to any one of Embodiments 1 to 2, wherein the second material includes titanium dioxide.

[0062] Example 4 includes the apparatus according to any one of Examples 1 to 3, wherein the height of the nanoscale fins is greater than or equal to about 3 micrometers.

[0063] Example 5 includes the apparatus according to any one of Examples 1 to 4, wherein the height of the nanoscale fins varies along the coupling length.

[0064] Example 6 includes the apparatus according to any one of Examples 1 to 5, wherein the height of the nanoscale fins increases along the coupling length.

[0065] Example 7 includes the apparatus according to any one of Examples 1 to 6, wherein the width of the waveguide varies along the coupling length.

[0066] Example 8 includes a system that includes: a substrate and nanoscale fins formed of a first material; a radio frequency transmitter configured to emit energy in a radio frequency range; a waveguide formed of a second material; a pump laser source configured to generate the pump laser; a probe laser source configured to generate the probe laser; a dichroic directional coupler coupled to the pump laser source and the probe laser source, wherein the dichroic directional coupler is configured to couple the pump laser and the probe laser into the waveguide, wherein the waveguide is positioned adjacent to the nanoscale fins along a coupling length such that the pump laser propagating within the waveguide is coupled into the nanoscale fins along the coupling length due to evanescent wave overlap, wherein when the energy emitted by the radio frequency transmitter is at one or more frequencies that depend on a magnetic field, the pump laser causes the first material to absorb the probe laser; and a processor configured to determine a magnetic field strength based on an identification of the one or more frequencies that depend on the magnetic field.

[0067] Example 9 includes the system according to Example 8, wherein the first material includes nitrogen-vacancy diamond.

[0068] Example 10 includes the system according to any one of Examples 8 to 9, wherein the second material includes titanium dioxide.

[0069] Example 11 includes the system according to any one of Examples 8 to 10, wherein the height of the nanoscale fins is greater than or equal to about 3 micrometers.

[0070] Example 12 includes the system according to any one of Examples 8 to 11, wherein the height of the nanoscale fins varies along the coupling length.

[0071] Example 13 includes the system according to any one of Examples 8 to 12, wherein the height of the nanoscale fins increases along the coupling length.

[0072] Example 14 includes the system according to any one of Examples 8 to 13, wherein the width of the waveguide varies along the coupling length.

[0073] Example 15 includes the system according to any one of Examples 8 to 14, further comprising a filter coupled to the waveguide, wherein the filter is configured to output the probe laser at a first output port of the filter and output the pump laser and fluorescence at a second output port of the filter.

[0074] Example 16 includes the system according to Example 15, further comprising an optical detection device coupled to the first output port of the filter and the processor, wherein the optical detection device is configured to monitor the intensity of the probe laser received from the filter and provide a signal associated with the intensity of the probe laser to the processor.

[0075] Example 17 includes a method that includes: forming nanoscale fins in a substrate of a first material; depositing a cladding material on the nanoscale fins and the substrate; forming a waveguide from a second material, wherein the waveguide is positioned along a coupling length adjacent to a top surface of the nanoscale fins such that light propagating within the waveguide couples into the nanoscale fins along the coupling length due to evanescent wave overlap; depositing the cladding material on the waveguide; coupling a probe laser source to the waveguide, wherein the probe laser source is configured to emit a probe laser into the waveguide; and coupling a pump laser source to the waveguide, wherein the pump laser source is configured to emit a pump laser into the waveguide at one or more resonant frequencies at which the waveguide layer is exposed to the first material such that the first material absorbs the wavelength of the probe laser.

[0076] Example 18 includes the method according to Example 17, wherein the first material includes nitrogen-vacancy diamond.

[0077] Example 19 includes the method according to any one of Examples 17 to 18, wherein the second material includes titanium dioxide.

[0078] Example 20 includes the method according to any one of Examples 17 to 19, wherein the height of the nanoscale fins is greater than or equal to approximately 3 micrometers.

[0079] Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will recognize that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. It is, therefore, evident that the invention is limited only by the claims and their equivalents.

Claims

1. An integrated photonic quantum vector magnetometer (800), comprising: A substrate (301) and nanoscale fins (302), the substrate and the nanoscale fins being formed of a first material, wherein a first end of the nanoscale fins (302) is connected to the substrate (301); A radio frequency transmitter configured to emit energy within a radio frequency range; Waveguides (304, 802) formed of a second material; A two-color directional coupler (806) configured to couple pump laser (807) and probe laser (809) into the waveguides (304, 802), wherein the waveguides (304, 802) are positioned along a coupling length direction close to a second end of the nanoscale fins (302) opposite the first end, such that the pump laser (807) propagating within the waveguides (304, 802) is coupled into the nanoscale fins (302) along the coupling length due to evanescent wave overlap, wherein the coupling length refers to the length of the waveguides, and wherein when the energy emitted by the radio frequency transmitter is at one or more frequencies depending on a magnetic field, the pump laser (807) causes the first material to absorb the probe laser (809); and A processor configured to determine a magnetic field strength based on an identification of the one or more frequencies depending on the magnetic field.

2. The integrated photonic quantum vector magnetometer (800) according to claim 1, wherein a height between the first end and the second end of the nanoscale fins (302) varies along the coupling length direction over the coupling length, and wherein a width of the waveguides (304, 802) varies along the coupling length direction over the coupling length.

3. The integrated photonic quantum vector magnetometer (800) according to claim 1, further comprising: A filter (815) coupled to the waveguides (304, 802), wherein the filter (815) is configured to output the probe laser (809) at a first output port (813) of the filter (815) and to output the pump laser (807) and fluorescence at a second output port (811) of the filter (815); and An optical detection device coupled to the first output port (813) of the filter (815) and the processor, wherein the optical detection device is configured to monitor an intensity of the probe laser (809) received from the filter (815) and to provide a signal associated with the intensity of the probe laser (809) to the processor.

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