Patent Description:
The present invention relates generally to sensor systems, and specifically to an atomic sensor system.

Atomic sensor systems, such as nuclear magnetic resonance (NMR) gyroscopes and magnetometers and/or electron paramagnetic resonance (EPR) magnetometers, can include a sensor cell that contains sensing media, such as alkali metal vapors (e.g., rubidium or cesium) caused to precess in response to a magnetic field. The sensing media can be stimulated to an excited state in response to optical pumping in a given frequency band. As an example, in an NMR gyroscope system, the sensor cell can also include gyromagnetic isotopes that are caused to precess in response to a magnetic field. The signal processing circuitry can extract the Larmor precession frequency and/or phase information of the one or more gyromagnetic isotopes. As a result, a gyroscope rotation rate or orientation angle about the sensitive axis can be calculated based on the extracted Larmor precession frequencies and phase information. As another example, in a magnetometer system, the precession of the alkali metal vapor(s) can be monitored by an optical signal. A change in the precession resulting from an external magnetic field relative to the sensitive axis can thus be detected to provide for a measurement of the amplitude of the external magnetic field.

<CIT> discloses a magnetic field measuring apparatus including a cell array with sensor cell systems, wherein an optical beam is provided to each of the sensor cell systems. The article "<NPL>, describes a high-sensitivity atomic gradiometer and suggests vector and tensor measurements in arrays. <CIT> describes an optical pumping magnetic sensor unit with several sensor cells for becoming sensitive to magnetic fields in different directions.

One aspect of the invention concerns an atomic sensor system in accordance with claim <NUM>. The system includes an optical source configured to provide an optical beam including a pump beam and a probe beam; and a plurality of sensor cell systems. Each of the sensor cell systems comprises sensing media enclosed in a volume therein. The system also includes optics configured to provide the optical beam to each of the sensor cell systems to provide interaction of the optical beam with the sensing media in each of the respective sensor cell systems. The optical beam exiting each of the sensor cell systems is a respective detection beam. The system further comprises a detection system comprising at least one photodetector configured to receive the detection beam from each of the sensor cell systems and to determine a measurable parameter based on an optical characteristic associated with the detection beam from each of the sensor cell systems.

Another aspect of the invention concerns a method in accordance with claim <NUM> for determining a measurable parameter in an atomic sensor system. The method comprises providing an optical beam including a pump beam and a probe beam to a plurality of sensor cell systems via optics to provide interaction of the optical beam with sensing media in each of the respective sensor cell systems. The optical beam exits each of the sensor cell systems as a respective detection beam. The method further includes monitoring the detection beam from each of the sensor cell systems to determine a measurable parameter based on an optical characteristic associated with the detection beam from each of the sensor cell systems.

The system according to the invention is a three-axis atomic sensor system. The system includes an optical source configured to provide an optical beam. The system also includes a first sensor cell system comprising sensing media and a first magnetic field generator arranged to provide a first magnetic field in a first vector direction, a second sensor cell system comprising the sensing media and a second magnetic field generator arranged to provide a second magnetic field in a second vector direction different from the first vector direction and a third sensor cell system comprising the sensing media and a third magnetic field generator arranged to provide a third magnetic field in a third vector direction different from the first and second vector directions. The first, second, and third sensor cell systems can be arranged in a 1x3 array. The system can also include optics configured to provide the optical beam parallel with respect to the arrangement of the first, second, and third sensor cell systems in the 1x3 array. The optics can include a plurality of beamsplitters configured to provide a portion of the optical beam to each of the first, second, and third sensor cell systems to provide interaction of each of the respective optical beam with the sensing media in each of the respective first, second, and third sensor cell systems. The portion of the optical beam exiting each of the first, second, and third sensor cell systems can be provided as a respective detection beam. The system further includes a detection system comprising at least one photodetector configured to receive the detection beam from each of the first, second, and third sensor cell systems and to determine a measurable parameter based on an optical characteristic associated with the detection beam from each of the first, second, and third sensor cell systems.

<FIG> illustrates an example of a method for determining a measurable parameter in an atomic sensor system.

The present invention relates generally to sensor systems, and specifically to an atomic sensor system. The atomic sensor system can be implemented in any of a variety of applications that require very precise measurements, such as in an inertial navigation system (INS) for aerospace aviation. The atomic sensor system is configured to provide a very precise measurement of a measurable parameter of an external stimulus. The atomic sensor system can correspond to any of a variety of nuclear magnetic resonance (NMR) or electron paramagnetic resonance (EPR) sensors, such as a gyroscope or magnetometer, or any of a variety of other types of atomic sensors (e.g., electrometer or accelerometer). Therefore, the measurable parameter can correspond to measurement of rotation about one or more sensitive axes and/or scalar or vector measurements of an external magnetic field.

The atomic sensor system includes an optical source (e.g., laser(s)) and a plurality of sensor cell systems. The optical source is configured to provide an optical beam including a pump beam and a probe beam to each of the sensor cell systems. As described herein, the term "sensor cell system" refers to a cell that is formed as a sensing media or encloses the sensing media in a volume therein. Such sensing media can thus be interactive with the at least one optical beam. As an example, the sensing media can be any of a variety of different type of polarizable spin systems. For example, the sensing media can correspond to vapors that can include any of alkali metal vapor (e.g., rubidium (Rb) or cesium (Cs)), gyromagnetic isotopes or other vapor that can exhibit spin, and/or buffer gases (e.g., nitrogen), such as based on the sensing application for the type of the sensor system and the parameter that is intended to be measured. As another example, the sensing media can include solid materials, such as can be optically probed for defect sensing, or can include any of a variety of liquids, plasma, or Bose-Einstein Condensate (BEC) that can be optically interactive, as well as additional ancillary materials to facilitate, modify, or improve optical interaction and/or sensing performance. As another example, the sensor cell systems can also include a magnetic field generator that is configured to generate a magnetic field (alternating current (AC) and/or direct current (DC)) in the volume therein.

The optical beam includes a pump beam that is provided through each of the sensor cell systems, such as to facilitate precession of alkali metal atoms based on the pump beam and the respective magnetic field. In accordance with the invention, the optical beam also includes a probe beam that is provided through each of the sensor cell systems to be provided as a detection beam exiting each of the respective sensor cell systems. The detection beam can have an optical characteristic (e.g., Faraday rotation or amplitude) that is indicative of the measurable parameter. In accordance with the invention, the optical beam corresponds to a single optical beam that is provided to each of the sensor cell systems, and implements the functions of both a pump beam and a probe beam. By providing the optical beam to each of the sensor cell systems, such that each of the sensor cell systems shares the functions provided by the optical beam, a significantly more simplistic atomic sensor can be realized by reducing optical componentry.

The atomic sensor system also includes a detection system that is configured monitor the detection beam associated with each of the sensor cell systems. The detection system can include a plurality of photodetectors (e.g., photodiodes) that are configured to monitor the detection beam associated with each of the sensor cell systems. Therefore, the detection system can include a processor that is configured to determine the measurable parameter based on monitoring the optical characteristic associated with each of the detection beams. As another example, the detection system can include one or more additional photodetectors, such as a feedback photodetector to monitor an intensity of the optical beam to control an optical characteristic (e.g., power) associated with the optical beam in a feedback manner.

The arrangement of the sensor cell systems can be provided in the atomic sensor system in a variety of ways. As an example, the sensor cell systems can be arranged in a 1xN array, such that the arrangement of sensor cell systems is in-line to reduce a form-factor for a compact sensor package. As another example, the sensor cell systems can be arranged in a tetrahedral arrangement to provide for measurement of a gradient (e.g., a magnetic field gradient) across the three-dimensional arrangement of the sensor cell systems.

The quantity of the sensor cell systems can be provided in the atomic sensor system in a variety of ways, as well. For example, the atomic sensor system can include a pair of sensor cell systems that are arranged and oriented approximately the same. Therefore, one of the sensor cell systems can be redundant with respect to the other sensor cell system to facilitate calibration and/or to cancel bias errors (e.g., based on different scale-factors). As another example, the atomic sensor system can include three sensor cell systems that are arranged to provide for three orthogonal sensitive axes. Therefore, the atomic sensor system arranged as an NMR or EPR gyroscope can determine motion about three orthogonal axes, or the atomic sensor system arranged as an NMR or EPR magnetometer can determine vector three-dimensional vector components of the external magnetic field. One or more additional sensor cell systems can be included to provide redundancy for calibrating and/or error cancelation in the three-axis arrangement.

<FIG> illustrates an example block diagram of an atomic sensor system <NUM>. The atomic sensor system <NUM> can be implemented in any of a variety of applications that require very precise measurements, such as in an INS for aerospace aviation. The atomic sensor system <NUM> is configured to provide a very precise measurement of a measurable parameter of an external stimulus. As an example, the atomic sensor system <NUM> can correspond to any of a variety of NMR or EPR sensors, such as a gyroscope, magnetometer, electrometer, accelerometer, clock, etc..

The atomic sensor system <NUM> includes an optical source <NUM> (e.g., a laser or optical fiber) and a plurality N of sensor cell systems <NUM>, where N is greater than one. The optical source <NUM> is configured to provide a respective optical beam OPT that is provided to each of the sensor cell systems <NUM> through a set of optics <NUM>. As an example, the optical beam includes a pump beam and a probe beam having appropriate frequencies and/or polarizations. As an example, the optics <NUM> can include an assortment of lenses, collimators, beamsplitters, mirrors, and/or a variety of other optical components to direct the optical beam(s) OPT to each of the sensor cell systems <NUM>. Additionally, while the optical beam OPT can propagate in free space, the optics <NUM> can include optical propagation media, such that optical beam OPT can propagate in an optical fiber, a waveguide, and/or other optical coupling components (e.g., grating out-couplers, integrated turning mirrors, photonic wire bonding, etc.). For example, the atomic sensor system <NUM> can be implemented in a photonics integrated circuit (PIC) or a planar lightwave circuit that includes the optics <NUM> integrated therein.

The sensor cell systems <NUM> can each include sensing media enclosed in a volume therein. As an example, the sensing media can be optically interactive with the optical beam OPT. As an example, each of the sensor cell systems <NUM> can include a magnetic field generator (not shown). The magnetic field generator can be configured to generate a magnetic field (alternating current (AC) and/or direct current (DC)) in the volume of the respective one of the sensor cell systems <NUM>. As described herein, the direction of the magnetic field through the volume of the sensor cell system <NUM> can dictate a sensitive axis of the respective sensor cell system <NUM>. For example, all of the sensor cell systems <NUM> can be fabricated approximately the same, and can be provided in the atomic sensor system <NUM> in different physical orientations with respect to each other to define different magnetic field directions, and therefore different sensitive axes. As an example and as described in greater detail herein, the different physical orientations may or may not be orthogonal to form a basis set for providing three-dimensional sensing of the measurable parameter.

The optical beam OPT includes a pump beam that is provided through each of the sensor cell systems <NUM>, such as to facilitate precession of alkali metal atoms provided as the sensing media within based on the pump beam and the respective magnetic field. The optical beam OPT includes a probe beam that is provided through each of the sensor cell systems <NUM> to be provided as a detection beam exiting each of the respective sensor cell systems <NUM>. In the example of <FIG>, the detection beams are demonstrated as OPTDET1 through OPTDETN corresponding respectively to the first through Nth sensor cell systems <NUM>. The detection beams OPTDET1 through OPTDETN can each have an optical characteristic (e.g., Faraday rotation or amplitude) that is indicative of the measurable parameter, as provided by the respective one of the sensor cell systems <NUM>. In accordance with the invention, the optical beam OPT corresponds to a single optical beam that is provided to each of the sensor cell systems <NUM>, and can implement the functions of both a pump beam and a probe beam. By providing the optical beam OPT to each of the sensor cell systems <NUM>, such that each of the sensor cell systems <NUM> shares the functions provided by the optical beam OPT, a significantly more simplistic atomic sensor can be realized by reducing optical componentry, as described in greater detail herein.

In the example of <FIG>, the atomic sensor system <NUM> also includes a detection system <NUM> that is configured to determine the measurable parameter, demonstrated as a signal MP. The detection system <NUM> includes a plurality of photodetectors (e.g., photodiodes) <NUM> that are configured to monitor the detection beams OPTDET1 through OPTDETN associated with the respective sensor cell systems <NUM>. Therefore, the detection system <NUM> can include a processor that is configured to determine the measurable parameter MP based on monitoring the optical characteristic associated with each of the detection beams OPTDET1 through OPTDETN. As another example, the detection system can include one or more additional photodetectors <NUM>, such as a feedback photodetector to monitor an intensity of the optical beam(s) OPT to control an optical characteristic (e.g., power) associated with the optical beam(s) OPT in a feedback manner.

The arrangement of the atomic sensor system <NUM> is not limited to the example of <FIG> or the following examples described herein. For example, additional components can be implemented in the atomic sensor system <NUM>. As an example, the atomic sensor system <NUM> can include heating elements, such as to maintain the vapor pressure of the sensing media (e.g., alkali metal atoms) in the sensor cell systems <NUM>, as well as temperature monitoring systems for the sensor cell systems <NUM>. Therefore, the heating elements and the temperature monitoring systems can cooperate to maintain a consistent temperature in the volume of the sensor cell systems <NUM> to provide for proper operation of the atomic sensor system <NUM>. For example, the heating elements and/or temperature monitors can be implemented as part of the atomic sensor system <NUM> or can be local to each of the sensor cell systems <NUM>. As yet another example, the atomic sensor system <NUM> can include magnetic shielding components to avoid magnetic field noise and/or crosstalk between the sensor cell systems <NUM>, as well as to suppress external magnetic fields. As an example, the magnetic shielding components can be deposited on substrate materials within the sensor cell systems <NUM>, or can be arranged external to and between the sensor cell systems <NUM>. For example, the magnetic shielding materials can include any of a variety of shielding materials (e.g., a high-µ material).

As described herein, the arrangement of the sensor cell systems <NUM> can be provided in the atomic sensor system <NUM> in a variety of ways. As an example, the sensor cell systems <NUM> can be arranged in a 1xN array, such that the arrangement of sensor cell systems <NUM> is in-line to reduce a form-factor for a compact sensor package. In this example, the optical beam OPT can be provided along the array parallel to the in-line arrangement of the sensor cell systems <NUM>, with the optics <NUM> being configured to tap a portion of the optical beam OPT to each of the sensor cell systems <NUM> along the in-line arrangement of the array. As another example, the sensor cell systems <NUM> can be arranged in a tetrahedral arrangement to provide for measurement of a gradient (e.g., a magnetic field gradient) across the three-dimensional arrangement of the sensor cell systems <NUM>.

The quantity of the sensor cell systems <NUM> can be provided in the atomic sensor system <NUM> in a variety of ways, as well. For example, the atomic sensor system <NUM> can include a pair of sensor cell systems <NUM> that are arranged and oriented approximately the same. Therefore, one of the sensor cell systems <NUM> can be redundant with respect to the other sensor cell system to facilitate calibration and/or to cancel bias errors (e.g., based on different scale-factors). As another example, the atomic sensor system <NUM> can include three sensor cell systems <NUM> that are arranged to provide for three orthogonal sensitive axes. Therefore, the atomic sensor system <NUM> arranged as an atomic gyroscope can determine motion about three orthogonal axes, or the atomic sensor system <NUM> arranged as an atomic magnetometer can determine vector three-dimensional vector components of the external magnetic field. One or more additional sensor cell systems <NUM> can be included to provide redundancy for calibrating and/or error cancelation in the three-axis arrangement. Therefore, the atomic sensor system <NUM> can be arranged in a variety of ways to implement determination of the measurable parameter MP in a variety of ways.

<FIG> illustrates an example of an atomic sensor system <NUM>. As an example, the atomic sensor system <NUM> can correspond to any of a variety of atomic sensors, such as a gyroscope or magnetometer. The atomic sensor system <NUM> can correspond to the atomic sensor system <NUM> in the example of <FIG>. Therefore, reference is to be made to the example of <FIG> in the following description of the example of <FIG>.

The atomic sensor system <NUM> includes a laser <NUM> and a plurality N of sensor cell systems <NUM>, where N is greater than one. The laser <NUM> is configured to provide a respective an optical beam OPT that is provided to each of the sensor cell systems <NUM> (e.g. through the optics <NUM>). In the example of <FIG>, the sensor cell systems <NUM> are arranged in a 1xN array, such that the arrangement of sensor cell systems <NUM> is in-line along the X-axis to reduce a form-factor for a compact sensor package. Thus, the optical beam OPT is provided along the X-axis parallel to the in-line arrangement of the sensor cell systems <NUM>. The optical beam OPT is provided to each of the sensor cell systems <NUM> via a beamsplitter ("BS") <NUM> that can be arranged as part of the optics. In the example of <FIG>, the separate portions of the optical beam OPT are provided as OPT<NUM> through OPTN to each of the respective first through Nth sensor cell systems <NUM>. The beamsplitter <NUM> can be configured as a partially silvered mirror or can be arranged as a polarization beamsplitter, such that the optics can include polarizers (e.g., a half-wave plate) in the optical path of the optical beam OPT.

Therefore, the optical beams OPT<NUM> through OPTN can interact with the sensing media enclosed in a volume within each of the sensor cell systems <NUM>. In the example of <FIG>, each of the sensor cell systems <NUM> includes a magnetic field generator ("B-GEN <NUM>" through "B-GEN N") <NUM>. The magnetic field generator <NUM> is configured to generate a magnetic field (alternating current (AC) and/or direct current (DC)) in the volume of the respective one of the sensor cell systems <NUM>. As described herein, the direction of the magnetic field through the volume of the sensor cell system <NUM> can dictate a sensitive axis of the respective sensor cell system <NUM>.

The optical beams OPT<NUM> through OPTN are configured to provide the functions of both a pump beam and a probe beam. For example, the optical beams OPT<NUM> through OPTN can be provided through each of the sensor cell systems <NUM> to facilitate precession of alkali metal atoms provided as the sensing media within based on respective magnetic field. The optical beams OPT<NUM> through OPTN are also provided as respective detection beams exiting each of the respective sensor cell systems <NUM>. In the example of <FIG>, the detection beams are demonstrated as OPTDET1 through OPTDETN corresponding respectively to the first through Nth sensor cell systems <NUM>. The detection beams OPTDET1 through OPTDETN can each have an optical characteristic (e.g., Faraday rotation or amplitude) that is indicative of the measurable parameter, as provided by the respective one of the sensor cell systems <NUM>. By providing the optical beam OPT to each of the sensor cell systems <NUM>, such that each of the sensor cell systems <NUM> shares the pump and probe beam functionality provided by the optical beam OPT, a significantly more simplistic atomic sensor can be realized by reducing optical componentry. Particularly, the associated bill of materials and form-factor of the atomic sensor system <NUM> can be significantly reduced relative to other atomic sensors that include multiple sensor cell systems.

In the example of <FIG>, the atomic sensor system <NUM> includes a plurality N of photodetectors (e.g., photodiodes) <NUM> that are configured to monitor the detection beams OPTDET1 through OPTDETN associated with the respective sensor cell systems <NUM>. The photodetectors <NUM> can be implemented in a detection system (e.g., the detection system <NUM>) that can include a processor configured to determine the measurable parameter based on monitoring the optical characteristic associated with each of the detection beams OPTDET1 through OPTDETN. Additionally, in the example of <FIG>, the atomic sensor system <NUM> includes a feedback photodetector ("FDBK PHOTODETECTOR") <NUM> that is configured to monitor an optical characteristic of the optical beam OPT. For example, the feedback photodetector <NUM> can monitor the intensity of the optical beam OPT to control the power associated with the optical beam OPT in a feedback manner.

As described above, the quantity N of the sensor cell systems <NUM> can be provided in the atomic sensor system <NUM> in a variety of ways. For example, the atomic sensor system <NUM> can include a pair of sensor cell systems <NUM> that are arranged and oriented approximately the same for redundancy to facilitate calibration and/or to cancel bias errors. As another example, the atomic sensor system <NUM> can include three sensor cell systems <NUM> that are arranged to provide for three orthogonal sensitive axes. Therefore, the atomic sensor system <NUM> arranged as an atomic gyroscope can determine motion about three orthogonal axes, or the atomic sensor system <NUM> arranged as an atomic magnetometer can determine vector three-dimensional vector components of the external magnetic field. One or more additional sensor cell systems <NUM> can be included to provide redundancy for calibrating and/or error cancelation in the three-axis arrangement. Therefore, the atomic sensor system <NUM> can be arranged in a variety of ways to implement determination of the measurable parameter MP in a variety of ways.

<FIG> illustrates an example of an atomic gyroscope system <NUM>. The atomic gyroscope system <NUM> is therefore configured to determine rotation about three orthogonal axes in three-dimensional space, as described in greater detail herein. As an example, the atomic gyroscope system <NUM> can be arranged as an NMR or EPR gyroscope. The atomic gyroscope system <NUM> can correspond to the atomic sensor system <NUM> in the example of <FIG>. Therefore, reference is to be made to the example of <FIG> in the following description of the example of <FIG>.

The atomic gyroscope system <NUM> includes a laser <NUM>, a first sensor cell system <NUM> ("SENSOR CELL SYSTEM X"), a second sensor cell system <NUM> ("SENSOR CELL SYSTEM Y"), and a third sensor cell system <NUM> ("SENSOR CELL SYSTEM Z"). The first sensor cell system <NUM> is associated with determining rotation about an X-axis, the second sensor cell system <NUM> is associated with determining rotation about a Y-axis, and the third sensor cell system <NUM> is associated with determining rotation about a Z-axis, with the X, Y, and Z axes being orthogonal with respect to each other. While the example of <FIG> demonstrates three sensor cell systems, one or more additional sensor cell systems can also be included. For example, an additional redundant sensor cell system can be provided for calibration or for error correction. As another example, the atomic gyroscope system <NUM> can include three additional redundant sensor cell systems, one for each of the X, Y, and Z axes, to provide calibration or error correction.

The laser <NUM> is configured to generate an optical beam OPT that is provided to each of the sensor cell systems <NUM>, <NUM>, and <NUM> (e.g. through the optics <NUM>). In the example of <FIG>, the sensor cell systems <NUM>, <NUM>, and <NUM> are arranged in a 1x3 array, such that the arrangement of sensor cell systems <NUM>, <NUM>, and <NUM> is in-line along the X-axis to reduce a form-factor for a compact sensor package. Thus, the optical beam OPT is provided along the X-axis parallel to the in-line arrangement of the sensor cell systems <NUM>, <NUM>, and <NUM>. The optical beam OPT is provided to each of the sensor cell systems <NUM>, <NUM>, and <NUM> via a beamsplitter <NUM> that can be arranged as part of the optics. In the example of <FIG>, the separate portions of the optical beam OPT are provided as OPTX, OPTY, and OPTZ to each of the respective first, second, and third sensor cell systems <NUM>, <NUM>, and <NUM>. The beamsplitter <NUM> can be configured as a partially silvered mirror or can be arranged as a polarization beamsplitter, such that the optics can include polarizers (e.g., a half-wave plate) in the optical path of the optical beam OPT.

Therefore, the optical beams OPTX, OPTY, and OPTZ can interact with the sensing media enclosed in a volume within each of the sensor cell systems <NUM>, <NUM>, and <NUM>. In the example of <FIG>, each of the sensor cell systems <NUM>, <NUM>, and <NUM> includes a magnetic field generator ("B-GEN X", "B-GEN Y", and "B-GEN Z") <NUM>. The magnetic field generator <NUM> is configured to generate a magnetic field (alternating current (AC) and/or direct current (DC)) in the volume of the respective one of the sensor cell systems <NUM>, <NUM>, and <NUM>. As described herein, the direction of the magnetic field through the volume of the sensor cell systems <NUM>, <NUM>, and <NUM> can dictate a sensitive axis of the respective sensor cell systems <NUM>, <NUM>, and <NUM>. For example, the different physical orientations of the sensor cell systems <NUM>, as well as the respective directions of the magnetic fields through the volume of the respective sensor cell systems <NUM>, <NUM>, and <NUM>, may or may not be orthogonal to form a basis set for providing three-dimensional sensing of the measurable parameter.

The optical beams OPTX, OPTY, and OPTZ are configured to provide the functions of both a pump beam and a probe beam. For example, the optical beams OPTX, OPTY, and OPTZ can be provided through each of the sensor cell systems <NUM>, <NUM>, and <NUM> to facilitate precession of alkali metal atoms provided as the sensing media within based on respective magnetic field. The optical beams OPTX, OPTY, and OPTZ are also provided as respective detection beams exiting each of the respective sensor cell systems <NUM>, <NUM>, and <NUM>. In the example of <FIG>, the detection beams are demonstrated as OPTDETX, OPTDETY, and OPTDETZ corresponding respectively to the first, second, and third sensor cell systems <NUM>, <NUM>, and <NUM>. The detection beams OPTDETX, OPTDETY, and OPTDETZ can each have an optical characteristic (e.g., Faraday rotation or amplitude) that is indicative of the rotation of the atomic gyroscope system <NUM> about the X-axis as provided by the sensor cell system <NUM>, about the Y-axis as provided by the sensor cell system <NUM>, and about the Z-axis as provided by the sensor cell system <NUM>, respectively.

In the example of <FIG>, the atomic gyroscope system <NUM> includes a first photodetector (e.g., photodiode) <NUM> that is configured to monitor the detection beam OPTDETX, a second photodetector <NUM> that is configured to monitor the detection beam OPTDETY, and a third photodetector <NUM> that is configured to monitor the detection beam OPTDETZ. The photodetectors <NUM>, <NUM>, and <NUM> can be implemented in a detection system (e.g., the detection system <NUM>) that can include a processor configured to determine the rotation of the atomic gyroscope system <NUM> based on monitoring the optical characteristic associated with each of the detection beams OPTDETX, OPTDETY, and OPTDETZ. Additionally, in the example of <FIG>, the atomic gyroscope system <NUM> includes a feedback photodetector <NUM> that is configured to monitor an optical characteristic of the optical beam OPT. For example, the feedback photodetector <NUM> can monitor the intensity of the optical beam OPT to control the power associated with the optical beam OPT in a feedback manner.

<FIG> illustrates an example diagram <NUM> of magnetic fields. The diagram <NUM> demonstrates a first magnetic field generator ("B-FIELD GENERATOR") <NUM>, a second magnetic field generator <NUM>, and a third magnetic field generator <NUM>. The diagram <NUM> also demonstrates a first Cartesian coordinate system <NUM>, a second Cartesian coordinate system <NUM>, and a third Cartesian coordinate system <NUM>. The Cartesian coordinate systems <NUM>, <NUM>, and <NUM> are not necessarily aligned to the Cartesian coordinate system demonstrated in the example of <FIG>. Each of the magnetic field generators <NUM>, <NUM>, and <NUM> can correspond to the magnetic field generators <NUM> of the respective sensor cell systems <NUM>, <NUM>, and <NUM> in the example of <FIG>. Therefore, reference is to be made to the example of <FIG> in the following description of the example of <FIG>.

The first Cartesian coordinate system <NUM> can correspond to the first magnetic field generator <NUM>. The first magnetic field generator <NUM> can have coils that are oriented in a manner to provide a magnetic field BX (e.g., in response to an AC and/or DC current). The magnetic field BX is demonstrated as being directed in the XY-plane, and thus having vector components both the -X-axis and the +Y-axis. Similarly, the second Cartesian coordinate system <NUM> can correspond to the second magnetic field generator <NUM>. The second magnetic field generator <NUM> can have coils that are oriented in a manner to provide a magnetic field BY (e.g., in response to an AC and/or DC current). The magnetic field BY is also demonstrated as also being directed in the XY-plane, but instead includes vector components in the +X-axis and the +Y-axis.

The third Cartesian coordinate system <NUM> can correspond to the third magnetic field generator <NUM>. The third magnetic field generator <NUM> can have coils that are oriented in a manner to provide a magnetic field BZ (e.g., in response to an AC and/or DC current). The magnetic field BZ is demonstrated as being directed in the YZ-plane, having vector components in the +Y-axis and the +Z-axis. Therefore, in the example of <FIG>, the magnetic field BZ is non-orthogonal with respect to the magnetic fields BX and BY. As an example, the detection system <NUM> can be programmed to determine the rotation or magnetic field component in the Z axis (orthogonal to the X-axis and the Y-axis) based on the non-orthogonal sensitive axis of the magnetic field BZ. Such an arrangement can provide for a simpler design with respect to parallel optical beams OPTX, OPTY, and OPTZ, and therefore parallel detection beams OPTDETX, OPTDETY, and OPTDETZ.

The arrangement of the magnetic fields BX, BY, and BZ can dictate the sensitive axes of each of the sensor cell systems <NUM>, <NUM>, and <NUM>. Based on the magnetic field vector of the magnetic field BX, the optical beam OPTX can be provided as the dual function of pump beam and probe beam. Additionally, the detection system (e.g., the detection system <NUM>) can determine rotation about the X-axis based on the optical characteristic of the detection beam OPTDETX based on identifying changes to the sensing media with respect to the X-axis. Similarly, based on the magnetic field vector of the magnetic field BY, the optical beam OPTY can be provided as the dual function of pump beam and probe beam. Additionally, the detection system can determine rotation about the Y-axis based on the optical characteristic of the detection beam OPTDETY based on identifying changes to the precession of the sensing media with respect to the Y-axis. Similarly, based on the magnetic field vector of the magnetic field BZ, the optical beam OPTZ can be provided as the dual function of pump beam and probe beam. Additionally, the detection system can determine rotation about the Z-axis based on the optical characteristic of the detection beam OPTDETZ based on identifying changes to the precession of the sensing media with respect to the Z-axis.

Referring to the example of <FIG>, the sensor cell systems <NUM>, <NUM>, and <NUM> can be fabricated approximately the same. In this example, the sensor cell systems <NUM>, <NUM>, and <NUM> can be physically oriented in different ways relative to each other to provide the different magnetic field vectors of the magnetic fields BX, BY, and BZ.

<FIG> illustrates an example of a sensor cell system <NUM>. The sensor cell system <NUM> can correspond to the each of the sensor cell systems <NUM>, <NUM>, and <NUM>. Therefore, reference is to be made to the example of <FIG> in the following description of the example of <FIG>.

The sensor cell system <NUM> is demonstrated in a perspective view. The sensor cell system <NUM> includes a housing <NUM> that is demonstrated in the example of <FIG> as substantially transparent to provide a view of the interior and to facilitate propagation of the optical beam, demonstrated at <NUM>, through the walls of the sensor cell system <NUM>. The transparency of the housing <NUM> depicted in the example of <FIG> for ease of demonstration, such that the housing <NUM> can only be transparent with respect to a given wavelength or band of the optical beam <NUM>. Alternatively, the housing <NUM> can include one or more transparent windows through which the optical beam <NUM> can propagate. Therefore, the optical beam <NUM> can interact with the sensing media enclosed therein. The sensor cell system <NUM> includes a primary coil <NUM> that is oriented at an angle within the volume of the sensor cell system <NUM>. The primary coil <NUM> can correspond to the magnetic field generator <NUM>, and therefore generate a magnetic field at an angle that is offset relative to the orthogonal walls of the sensor cell system <NUM>.

The sensor cell system <NUM> also includes secondary coils <NUM> and <NUM> that can provide additional magnetic fields. For example, the secondary coils <NUM> and <NUM> can be oriented in a variety of different vectors in the sensor cell <NUM> (e.g., parallel with, perpendicular to, or skewed with respect to the primary coil <NUM>) to provide a respective variety of secondary magnetic field directions. As an example, the secondary coils <NUM> and <NUM> can provide magnetic field adjustment in a feedback manner to accommodate internal or external perturbations associated with the respective magnetic field generator in the sensor cell system <NUM> (e.g., the respective one of the magnetic field generators <NUM>, <NUM>, and <NUM> in the example of <FIG>). For example, the secondary coils <NUM> and <NUM> can provide magnetic fields to modify the vector directions of the respective one of the magnetic fields BX, BY, and BZ that the magnetic field generator of the sensor cell system <NUM> is configured to provide. Therefore, the respective one of the magnetic fields BX, BY, and BZ can be corrected in a feedback manner and/or adjusted to change the vector of the respective one of the magnetic fields BX, BY, and BZ. As another example, the secondary coils <NUM> and <NUM> can provide AC magnetic fields, such as to facilitate precession of alkali metal vapor provided as the sensing media in the sensor cell <NUM>. Accordingly, the secondary coils <NUM> and <NUM> can provide a variety of different functions for providing secondary AC and/or DC magnetic fields within the volume of the sensor cell <NUM>.

<FIG> illustrates an example of a three-axis sensor cell arrangement <NUM>. The three-axis sensor cell arrangement <NUM> includes a first sensor cell system <NUM>, a second sensor cell system <NUM>, and a third sensor cell system <NUM>. As an example, each of the sensor cell systems <NUM>, <NUM>, and <NUM> can be fabricated approximately the same, and can each correspond to the sensor cell system <NUM>. Each of the sensor cell systems <NUM>, <NUM>, and <NUM> includes a primary coil <NUM> that is oriented at an angle within the volume of the respective sensor cell systems <NUM>, <NUM>, and <NUM>. Therefore, reference is to be made to the example of <FIG> in the following description of the example of <FIG>.

The first sensor cell system <NUM> can correspond to the sensor cell system <NUM> in the example of <FIG>, and can therefore be configured to determine rotation about the Y-axis. Thus, the magnetic field generator of the first sensor cell system <NUM> can be configured to provide the magnetic field vector BY. As a result, the detection beam OPTDETY corresponding to the optical beam OPTY can be monitored by the photodetector <NUM> of the detection system (e.g., the detection system <NUM>) to determine a change in the optical characteristic (e.g., Faraday rotation or amplitude) corresponding to rotation about the Y-axis.

The second sensor cell system <NUM> is demonstrated as rotated <NUM>° about the propagation path of the respective optical beams relative to the first sensor cell system <NUM>. The second sensor cell system <NUM> can correspond to the sensor cell system <NUM> in the example of <FIG>, and can therefore be configured to determine rotation about the X-axis. Thus, the magnetic field generator of the second sensor cell system <NUM> can be configured to provide the magnetic field vector BX. As a result, the detection beam OPTDETX corresponding to the optical beam OPTX can be monitored by the photodetector <NUM> of the detection system (e.g., the detection system <NUM>) to determine a change in the optical characteristic (e.g., Faraday rotation or amplitude) corresponding to rotation about the X-axis.

The third sensor cell system <NUM> is demonstrated as rotated about two-orthogonal axes relative to the first sensor cell system <NUM> and the second sensor cell system <NUM>. The third sensor cell system <NUM> can correspond to the sensor cell system <NUM> in the example of <FIG>, and can therefore be configured to determine rotation about the Z-axis. Thus, the magnetic field generator of the third sensor cell system <NUM> can be configured to provide the magnetic field vector BZ. As a result, the detection beam OPTDETZ corresponding to the optical beam OPTZ can be monitored by the photodetector <NUM> of the detection system (e.g., the detection system <NUM>) to determine a change in the optical characteristic (e.g., Faraday rotation or amplitude) corresponding to rotation about the Z-axis. Based on the rotation of the third sensor cell <NUM> about the two-orthogonal axes relative to the first sensor cell system <NUM> and the second sensor cell system <NUM>, the third sensor cell <NUM> can provide the magnetic field vector BZ as non-orthogonal with respect to the magnetic field vector BX and the magnetic field vector BY, similar to as described above in the example of <FIG> As such, the associated detection system (e.g., the detection system <NUM>) can implement a simpler design for determining rotation or magnetic field about three orthogonal axes based on parallel optical beams OPTX, OPTY, and OPTZ, and therefore parallel detection beams OPTX, OPTY, and OPTz.

By implementing the sensor cell systems <NUM>, <NUM>, and <NUM> as approximately identical sensor cell systems and manipulating the magnetic field vectors merely by physically orienting the sensor cell systems <NUM>, <NUM>, and <NUM> relative to each other, the fabrication of an associated atomic sensor system can be provided in a much more simplistic manner.

<FIG> illustrates an example of an atomic magnetometer system <NUM>. The atomic magnetometer system <NUM> is configured to determine a vector and intensity measurement of an external magnetic field in three-dimensional space, as described in greater detail herein. As an example, the atomic magnetometer system <NUM> can be arranged as an NMR or EPR magnetometer. The atomic magnetometer system <NUM> can correspond to the atomic sensor system <NUM> in the example of <FIG>. Therefore, reference is to be made to the example of <FIG> in the following description of the example of <FIG>.

The atomic magnetometer system <NUM> includes a laser <NUM>, a first sensor cell system <NUM> ("SENSOR CELL SYSTEM X"), a second sensor cell system <NUM> ("SENSOR CELL SYSTEM Y"), and a third sensor cell system <NUM> ("SENSOR CELL SYSTEM Z"). As an example, the sensor cell systems <NUM>, <NUM>, and <NUM> can each correspond to the sensor cell system <NUM> in the example of <FIG>. Therefore, each of the sensor cell systems <NUM>, <NUM>, and <NUM> can be fabricated approximately identically, as described above. The first sensor cell system <NUM> is associated with determining an X-axis component of the external magnetic field, the second sensor cell system <NUM> is associated with determining a Y-axis component of the external magnetic field, and the third sensor cell system <NUM> is associated with determining a Z-axis component of the external magnetic field, with the X, Y, and Z axes being orthogonal with respect to each other. While the example of <FIG> demonstrates three sensor cell systems, one or more additional sensor cell systems can also be included. For example, an additional redundant sensor cell system can be provided for calibration or for error correction. As another example, the atomic gyroscope system <NUM> can include three additional redundant sensor cell systems, one for each of the X, Y, and Z axes, to provide calibration or error correction.

The laser <NUM> is configured to generate an optical beam OPT that is provided to each of the sensor cell systems <NUM>, <NUM>, and <NUM> (e.g. through the optics <NUM>). In the example of <FIG>, the sensor cell systems <NUM>, <NUM>, and <NUM> are arranged in a 1x3 array, such that the arrangement of sensor cell systems <NUM>, <NUM>, and <NUM> is in-line along the X-axis to reduce a form-factor for a compact sensor package. Thus, the optical beam OPT is provided along the X-axis parallel to the in-line arrangement of the sensor cell systems <NUM>, <NUM>, and <NUM>. The optical beam OPT is provided is split via a beamsplitter <NUM> that can be arranged as part of the optics to provide optical beams OPTX, OPTY, and OPTz. The beamsplitter <NUM> can be configured as a partially silvered mirror or can be arranged as a polarization beamsplitter, such that the optics can include polarizers (e.g., a half-wave plate) in the optical path of the optical beam OPT.

In the example of <FIG>, each of the optical beams OPTX, OPTY, and OPTZ are provided through a quarter-wave plate <NUM> that is arranged between the beamsplitters <NUM> and the respective sensor cell systems <NUM>, <NUM>, and <NUM>. Therefore, the optical beams OPTX, OPTY, and OPTZ are circularly-polarized to provide optical beams OPTCX, OPTCY, and OPTCZ that are provided to the sensor cell systems <NUM>, <NUM>, and <NUM>. Therefore, the optical beams OPTCX, OPTCY, and OPTCZ can interact with the sensing media enclosed in a volume within each of the sensor cell systems <NUM>, <NUM>, and <NUM>. In the example of <FIG>, each of the sensor cell systems <NUM>, <NUM>, and <NUM> includes a magnetic field generator ("B-FIELD GENERATOR") <NUM>. The magnetic field generator <NUM> is configured to generate a magnetic field (alternating current (AC) and/or direct current (DC)) in the volume of the respective one of the sensor cell systems <NUM>, <NUM>, and <NUM>. As described herein, the direction of the magnetic field through the volume of the sensor cell systems <NUM>, <NUM>, and <NUM> can dictate a sensitive axis of the respective sensor cell systems <NUM>, <NUM>, and <NUM>, similar to as described above in the example of <FIG>.

As an example, the optical beams OPTCX, OPTCY, and OPTCZ are configured to provide the functions of both a pump beam and a probe beam. For example, the optical beams OPTCX, OPTCY, and OPTCZ can be provided through each of the sensor cell systems <NUM>, <NUM>, and <NUM> along the -Y-axis to facilitate precession of alkali metal atoms provided as the sensing media within based on respective magnetic field. In the example of <FIG>, the atomic magnetometer system <NUM> includes a retroreflector <NUM> that is configured to reflect the optical beams OPTCX, OPTCY, and OPTCZ back through the respective sensor cell systems <NUM>, <NUM>, and <NUM> along the +Y-axis. While the retroreflector <NUM> is demonstrated as a singular retroreflector, multiple retroreflectors <NUM>, one for each of the optical beams OPTCX, OPTCY, and OPTCZ, can instead be implemented. The optical beams OPTCX, OPTCY, and OPTCZ are thus provided in a propagation direction that is collinear with the optical beams OPTCX, OPTCY, and OPTCZ provided along the -Y-axis through the respective sensor cell systems <NUM>, <NUM>, and <NUM>. The optical beams OPTCX, OPTCY, and OPTCZ provided along the +Y-axis have a circular-polarization that is an opposite orientation of the collinear respective optical beams OPTCX, OPTCY, and OPTCZ provided along the -Y-axis.

The optical beams OPTCX, OPTCY, and OPTCZ provided along the +Y-axis exit the respective sensor cell systems <NUM>, <NUM>, and <NUM> as respective circularly-polarized detection beams exiting each of the respective sensor cell systems <NUM>, <NUM>, and <NUM>. In the example of <FIG>, the detection beams are demonstrated as OPTDETCX, OPTDETCY, and OPTDETCZ corresponding respectively to the first, second, and third sensor cell systems <NUM>, <NUM>, and <NUM>. The circularly-polarized detection beams OPTDETCX, OPTDETCY, and OPTDETCZ can each have an optical characteristic (e.g., Faraday rotation or amplitude) that is indicative of the vector component of the external magnetic field of the atomic magnetometer system <NUM> relative to the X-axis as provided by the sensor cell system <NUM>, relative to the Y-axis as provided by the sensor cell system <NUM>, and relative to the Z-axis as provided by the sensor cell system <NUM>, respectively.

The circularly-polarized detection beams OPTDETCX, OPTDETCY, and OPTDETCZ are each provided to the quarter-wave plates <NUM>. The quarter-wave plates <NUM> therefore convert the circularly-polarized detection beams OPTDETCX, OPTDETCY, and OPTDETCZ to linearly-polarized detection beams OPTDETX, OPTDETY, and OPTDETZ. In the example of <FIG>, the atomic magnetometer system <NUM> includes a first photodetector (e.g., photodiode) <NUM> that is configured to monitor the detection beam OPTDETX, a second photodetector <NUM> that is configured to monitor the detection beam OPTDETY, and a third photodetector <NUM> that is configured to monitor the detection beam OPTDETZ. The photodetectors <NUM>, <NUM>, and <NUM> can be implemented in a detection system (e.g., the detection system <NUM>) that can include a processor configured to determine the intensity and vector direction external magnetic field based on monitoring the optical characteristic associated with each of the detection beams OPTDETX, OPTDETY, and OPTDETZ. Additionally, similar to as described above in the example of <FIG>, the atomic magnetometer system <NUM> includes a feedback photodetector <NUM> that is configured to monitor an optical characteristic of the optical beam OPT. For example, the feedback photodetector <NUM> can monitor the intensity of the optical beam OPT to control the power associated with the optical beam OPT in a feedback manner.

In view of the foregoing structural and functional features described above, methods in accordance with various aspects of the present disclosure will be better appreciated with reference to <FIG>. While, for purposes of simplicity of explanation, the method of <FIG> is shown and described as executing serially, it is to be understood and appreciated that the present disclosure is not limited by the illustrated orders, as some aspects could, in accordance with the present disclosure, occur in different orders and/or concurrently with other aspects from that shown and described herein. Moreover, not all illustrated features may be required to implement method in accordance with an aspect of the present disclosure.

<FIG> illustrates an example of a method <NUM> for determining a measurable parameter in an atomic sensor system (e.g., the atomic sensor system <NUM>). At <NUM>, an optical beam (e.g., the optical beam OPT) is provided to a plurality of sensor cell systems (e.g., the sensor cell systems <NUM>) via optics (e.g., the optics <NUM>) to provide the optical beam to each of the sensor cell systems to provide interaction of the optical beam with sensing media in each of the respective sensor cell systems. The optical beam exits each of the sensor cell systems as a respective detection beam (e.g., the detection beams OPTDET). At <NUM>, the detection beam from each of the sensor cell systems is monitored to determine a measurable parameter based on an optical characteristic associated with the detection beam from each of the sensor cell systems.

Claim 1:
An atomic sensor system (<NUM>) comprising:
an optical source (<NUM>) configured to provide an optical beam (OPT) including a pump beam and a probe beam;
a plurality of sensor cell systems (<NUM>), each of the sensor cell systems comprising sensing media enclosed in a volume therein, the sensor cell systems comprising;
a first sensor cell system (<NUM>) including a first magnetic field generator (<NUM>) configured to generate a first magnetic field within the volume therein and in a first vector direction;
a second sensor cell system (<NUM>) including a second magnetic field generator (<NUM>) configured to generate a second magnetic field within the volume therein and in a second vector direction different from the first vector direction; and
a third sensor cell system (<NUM>) including a third magnetic field generator (<NUM>) configured to generate a third magnetic field within the volume therein and in a third vector direction different from the first and second vector directions;
optics (<NUM>) configured to provide the optical beam (OPT) to each of the sensor cell systems (<NUM>) to provide interaction of the optical beam with the sensing media in each of the respective sensor cell systems, the optical beam exiting each of the sensor cell systems as a respective detection beam; and
a detection system (<NUM>) comprising at least one photodetector (<NUM>) configured to receive the detection beam from each of the sensor cell systems and to determine a measurable parameter based on an optical characteristic associated with the detection beam from each of the sensor cell systems.