Electrometer sensor control system

Abstract

One embodiment includes an electrometer system including a sensor cell containing alkali metal atoms therein and a probe laser configured to generate a probe beam, the probe beam being provided to pass through the sensor cell. The system also includes a combination laser configured to generate a combined beam, the combined beam being provided to pass through the sensor cell and capable of combining with the probe beam provided to pass through the sensor cell to produce a Rydberg energy state of the alkali metal atoms, the probe beam exiting the sensor cell as a detection beam. The system further includes a sensor control system configured to monitor the detection beam and detect an external signal based on monitoring the phase of the detection beam.

Description

[Technical field]

[0001] The present invention relates generally to sensor systems, and more particularly to electrometer sensor control systems. [Background technology]

[0002] Electric field measurements by electrometers have many useful applications. Detectable electric fields can include DC electric fields, and AC electric fields (e.g., radio frequency (RF) fields that may correspond to communication signals). Detection of electric fields can be implemented for anti-spoofing and / or counter-jamming capabilities in electronic warfare environments. For example, if a jamming or spoofing signal can be detected, the jamming or spoofing signal can be filtered or demodulated to provide a desired baseband signal without unwanted or hostile interference. As an example, multiple antennas arranged in an array can provide directional detection of a signal, such as to provide a detectable directionality of a signal source. Summary of the Invention

[0003] One embodiment includes an electrometer system including a sensor cell having an alkali metal atom therein and a probe laser configured to generate a probe beam, the probe beam being provided to pass through the sensor cell, and a combination laser configured to generate a combined beam, the combined beam being provided to pass through the sensor cell and capable of combining with the probe beam provided to pass through the sensor cell to produce a Rydberg energy state of the alkali metal atom, the probe beam exiting the sensor cell as a detection beam, and the system further includes a sensor control system configured to monitor the detection beam and detect an external signal based on monitoring a phase of the detection beam.

[0004] Another example includes a method for detecting an external signal via an electrometer system. The method includes illuminating a probe beam in a first direction through a sensor cell containing an alkali metal atom, and illuminating a combined beam through the sensor cell collinearly and anti-parallel to the probe beam to produce a Rydberg energy state of the alkali atom. The method also includes providing a split signal having a predetermined frequency through the sensor cell to produce a pair of Autler-Townes frequency spectrum transmission peaks for the Rydberg energy state associated with the alkali metal atom. The method further includes monitoring a phase of a detection beam relative to at least one of the pair of Autler-Townes frequency spectrum transmission peaks to detect the external signal, the detection beam corresponding to the probe beam exiting the sensor cell.

[0005] Another example includes an electrometer system. The system includes a probe laser configured to generate a probe beam and a combined laser configured to generate a combined beam provided to pass through the sensor cell. The system also includes a split signal generator configured to generate a split signal having a predetermined frequency that passes through the sensor cell to produce a pair of Outler-Townes frequency spectrum transmission peaks associated with the alkali metal atom. The system further includes a sensor control system configured to split the probe beam into a first probe beam and a second probe beam that are each provided to pass through the sensor cell as a combined light beam and exit the sensor cell as a detection beam. The first and second probe beams can have individual frequencies approximately equal to the frequencies associated with the respective pair of Outler-Townes frequency spectrum transmission peaks. The combined light beam and the combined beam can produce a Rydberg energy state of the alkali metal atom. The sensor control system can be further configured to monitor a phase of the detection beam relative to at least one of the Outler-Townes frequency spectrum transmission peaks to detect an external signal. [Brief description of the drawings]

[0006] [Figure 1] 1 shows an exemplary diagram of an electrometer system. [Diagram 2] 2 shows another exemplary diagram of an electrometer system. [Diagram 3] 1 shows an exemplary diagram of light detection. [Figure 4] 2 illustrates another example of an electrometer system. [Diagram 5] 1 illustrates an example method for detecting an external signal via an electrometer system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The present invention generally relates to a sensor system, and more particularly to an electrometer sensor control system. The electrometer system may include a sensor cell containing an alkali metal atomic vapor enclosed therein. The electrometer system also includes a probe laser and at least one combined laser configured to generate a probe beam and at least one respective combined beam. Each of the probe beam and combined beam(s) may be provided to pass through the sensor cell via a set of optics such that the probe beam and combined beam(s) may be arranged collinearly and anti-parallel to each other. For example, the probe beam and combined beam(s) may be tuned to respective frequencies to produce Rydberg energy states of the alkali metal vapor.

[0008] The electrometer system also includes a split signal generator configured to generate a split signal having a predetermined frequency and a predetermined amplitude that passes through the sensor cell. As an example, the split signal generator can provide a split signal to split a frequency spectrum transmission peak corresponding to a Rydberg energy state of an alkali metal atom into a pair of Outler-Townes frequency spectrum transmission peaks for the Rydberg energy state associated with the alkali metal atom, such as where the frequency of the split signal is approximately equal to the energy difference between the Rydberg energy state and a second Rydberg energy state. The split signal can be set to a frequency that corresponds to the frequency of an external signal desired to be detected by the electrometer system, for example.

[0009] The electrometer system further includes a sensor control system configured to monitor the phase of the detection beam to detect the external signal. The sensor control system can split the probe beam into multiple probe beams. The first probe beam can be implemented to lock the frequency of the probe laser. The second and third probe beams can be modulated to have a frequency approximately equal to the Outler-Townes frequency spectrum transmission peak and combined to provide a combined probe beam that passes through the sensor cell. The combined probe beam exiting the sensor cell can correspond to the detection beam, and the detection beam can be combined with the fourth probe beam. The sensor control system can include multiple photodetectors that can monitor the intensities of the first, second, and third probe beams, and the combined probe beam, as well as the combination of the detection beam and the fourth probe beam. Thus, the photodetectors can be implemented to cancel power fluctuations, phase fluctuations, and frequency fluctuations of the separate probe beams. Additionally, the signal provided by the photodetector may be implemented to resolve phase changes of the second and third probe beams relative to the Outler-Townes frequency spectrum transparency peak to identify a change in the Outler-Townes frequency spectrum transparency peak corresponding to the presence of an external signal.

[0010] 1 shows an example diagram of an electrometer system 100. Electrometer system 100 can be implemented in any of a variety of applications, such as for detecting external electromagnetic signals of any frequency.

[0011] The electrometer system 100 includes a sensor cell 102, which may be configured as a sealed glass vessel containing a vapor of alkali metal atoms. By way of example, the alkali metal vapor may be rubidium (Rb), or any of a variety of other types of alkali metals (e.g., cesium (Cs)). As described herein, the alkali metal vapor may be excited into a Rydberg state, making the alkali metal vapor substantially insensitive (e.g., nearly transparent) to absorption of photons of light of a particular frequency. The electrometer system 100 also includes a probe beam OPT. PRB and at least one respective combined beam OPT CPL and at least one combined laser 106 configured to generate a combined beam OPT. CPL are relative to each other and the probe beam opt PRB In the example of FIG. 1, the probe beam OPT can include a first combined beam and a second combined beam that are tuned to different frequencies. PRB is provided to the sensor control system 108. The sensor control system 108 controls the probe beam OPT as described in more detail herein. PRB In the example of FIG. 1, the sensor control system 108 is configured to split the probe beam OPT PRB Combined probe beam OPT including multiple (e.g., pair) split versions of CMB As an example, a combined probe beam OPT can be generated. CMB can include a first probe beam and a second probe beam, the first probe beam and the second probe beam having respective frequencies approximately equal to and on either side of the Rydberg transition frequency of the alkali metal atoms.

[0012] In the example shown in Figure 1, a combined probe beam OPT CMB and combined beam OPT CPL is a combination probe beam OPT CMB and combined beam OPTCPL are each collimated (e.g., via an optical system) and are provided collinearly and anti-parallel to each other to pass through the sensor cell 102 via an optical system (not shown). CMB and combined beam OPT CPL can be tuned to individual frequencies to produce Rydberg energy states of the alkali metal vapor such that the alkali metal vapor is excited into the Rydberg energy state. CMB is the detection beam OPT DET can be emitted from the sensor cell 102 as

[0013] The electrometer system 100 also receives a split signal RF SPL The split signal generator 110 is configured to generate a split signal RF SPL may be a radio frequency (RF) signal provided to pass through the sensor cell 102 at a predetermined frequency and a predetermined amplitude. As an example, the split signal generator 110 may generate a split signal RF SPL to produce a pair of Outler-Townes frequency spectrum transmission peaks associated with alkali metal atoms. SPL can be set to a frequency corresponding to the frequency of an external signal desired to be detected by the electrometer system. CMB The pair can include a first probe beam and a second probe beam having respective frequencies approximately equal to respective frequencies of a transmission peak in the frequency spectrum of the Outler-Townes pair.

[0014] The sensor control system 108 controls the detection beam OPT DET Monitor the external signal RF EXT The sensor control system 108 is configured to detect the detection beam OPT DET By monitoring the phase of the combined probe beam OPTCMB Probe beam OPT PRB The sensor control system 108 may include a photodetector capable of detecting the respective phase shifts of the split version of RF for each pair of Outler-Townes frequency spectrum transparency peaks. Thus, the sensor control system 108 may determine a change in the pair of Outler-Townes frequency spectrum transparency peaks that corresponds to the presence of an external signal. As a result, the split signal RF SPL An external signal RF having a frequency approximately equal to that of EXT As described in more detail herein, the sensor control system 108 controls the probe beam OPT PRB by monitoring the optical signal provided from the split of the detection beam to substantially cancel noise sources in the phase measurement (e.g., by canceling power fluctuations, phase fluctuations, and frequency fluctuations of the separate probe beams) and optimizing the detection beam to a pair of Outler-Townes frequency spectrum transparency peaks. DET The phase of can be calculated.

[0015] 2 shows another exemplary diagram of an electrometer system 200. The electrometer system 200 receives an external signal RF EXT The present invention can be practiced in any of a variety of applications in which detection of

[0016] The electrometer system 200 includes a sensor cell 202, which may be configured as a sealed glass vessel containing an alkali metal vapor. The electrometer system 200 also includes a probe beam OPT. PRB and a probe laser 204 configured to generate a first combined beam OPT CPL1 and the second combined beam OPT CPL2 and a pair of coupled lasers 206 (e.g., including a first coupled laser and a second coupled laser) configured to generate a probe beam OPT. PRB is provided to the sensor control system 210. The sensor control system 210 controls the probe beam OPT as described in more detail herein. PRB1. The sensor control system 210 is configured to split the probe beam OPT into multiple different beams, similar to that described above in the example of FIG. PRB A combined probe beam OPT including a first probe beam and a second probe beam corresponding to a split version of CMB It is possible to generate a combined probe beam OPT. CMB The first and second probe beams forming the probe beam can have respective frequencies approximately equal to and on either side of the Rydberg transition frequency of the alkali metal atoms, e.g., approximately aligned with a pair of Outler-Townes frequency spectrum transmission peaks.

[0017] In the example in Figure 2, the combined probe beam OPT CMB is provided to the sensor cell 202 via an optical system generally designated 212. Similarly, the combined beam OPT CPL1 , OPT CPL2 is provided to a beam splitter 214 (e.g., a polarizing beam splitter), which outputs the combined beam OPT CPL1 , OPT CPL2 is reflected into the sensor cell 202 and combined with the probe beam OPT CMB The detection beam OPT is monitored by the sensor control system 210. DET In the example of FIG. 2, the combined beam OPT CPL1 , OPT CPL2 Although shown separately, additional optics are used to OPT the combined beam. CPL1 , OPT CPL2 can be provided as collinear with respect to each other. Similarly, the combined probe beam OPT CMB can correspond to two probe beams provided collinearly with respect to each other. As described in more detail herein, the probe beam OPT PRB and combined beam OPT CPL1 , OPT CPL2 can be tuned to individual frequencies to produce Rydberg energy states in the alkali metal vapor.

[0018] Based on the arrangement of the beam splitter 214, the probe beam is OPTO PRB and combined beam(s) OPT CPL 2, as shown at 214 in the example of FIG. PRB and combined beam(s) OPT CPL may be provided to pass through the sensor cell 202 in such a manner that the combined probe beam OPT CMB along a particular axis within the sensor cell 202; and a collimating optical system 216 (e.g., a lens) that can collimate the combined beam OPT. CPL1 , OPT CPL2 and a collimating optics 218 (e.g., a lens) that can collimate the combined probe beam OPT along a particular axis within the sensor cell 202. CMB and combined beam OPT CPL1 , OPT CPL2 Alternatively, the electrometer system 200 may include a combined probe beam OPT. CMB and combined beam OPT CPL1 , OPT CPL2 The combined probe beam OPT can include focusing optics for focusing each of the combined probe beams OPT to be co-located at a measurement point within the sensor cell 202. CMB is set up to excite the alkali metal vapor to the first excited state, and the combined beam OPT CPL1 , OPT CPL2 The frequency of the probe beam OPT is set to stimulate the excited alkali metal vapor into a Rydberg energy state and thus into electromagnetically induced transparency. As a result, the alkali metal atoms in the Rydberg energy state are PRB may be transparent to absorption by light at frequencies approximately

[0019] The electrometer system 200 receives a split signal RF SPL The split signal generator 220 is configured to generate a split signal RF SPL may be an RF signal provided to pass through the sensor cell 202 at a predetermined frequency and a predetermined amplitude. SPL split signal RF so as to give rise to a pair of Outler-Townes frequency spectrum transparency peaks associated with alkali metal atoms when the frequency of Rydberg is approximately equal to the energy difference between the Rydberg energy state and the second Rydberg energy state. SPL It is possible to provide a split signal RF SPL may be set, for example, to a frequency corresponding to the frequency of an external signal desired to be detected by the electrometer system.

[0020] The sensor control system 210 controls the detection beam OPT DET Monitor the external signal RF EXT The sensor control system 210 is configured to detect the probe beam OPT at the input and output of the sensor cell 202. PRB The optical fiber optics may include a plurality of optical detectors capable of monitoring different split versions (including combinations thereof) of the detection beam OPT. DET By monitoring the phase of the combined probe beam OPT CMB Probe beam OPT PRB The individual phase shifts of the split versions of can be detected for each pair of Outler-Townes frequency spectrum transmission peaks. Thus, the sensor control system 108 controls the combined probe beam OPT CMB Split probe beam OPT PRB Based on the relative phase shift of the first and second versions of the signal, it is possible to determine the change in the frequency spectrum transparency peak of a pair of Outler-Townes filters corresponding to the presence of an external signal. As a result, the split signal RF SPL An external signal RF having a frequency approximately equal to that of EXTIn addition, as described in more detail herein, the sensor control system 210 can detect the probe beam OPT PRB by monitoring the optical signal provided from the split of the detection beam to substantially cancel noise sources in the phase measurement (e.g., by canceling power fluctuations, phase fluctuations, and frequency fluctuations of the separate probe beams) and optimizing the detection beam to a pair of Outler-Townes frequency spectrum transparency peaks. DET The phase of can be calculated.

[0021] 3 shows an exemplary diagram 300 of optical detection. Diagram 300 shows an energy state diagram 302, a detection beam OPT plotted as a function of frequency detuning (in megahertz) from the |1> to |2> energy level transition frequency. DET Graph 304 showing the percentage change in transmission of the detection beam OPT plotted as a function of frequency detuning (in megahertz) from the |1> to |2> energy level transition frequency. DET 3 includes a graph 306 illustrating a phase shift of .Diagram 300 may correspond to light detection in electrometer system 200. Accordingly, in the following description of the example of FIG.

[0022] The energy state diagram 302 shows the first energy state (e.g., ground state) |1> that an alkali metal atom can start in. As an example, if the alkali metal atom is rubidium, the first energy state is |5S 1 / 2 > Combined probe beam OPT CMB In response to, a population of alkali metal atoms can be excited to a first excited state |2>. As an example, a combined probe beam OPT CMB The first and second probe beams forming |5P| may have respective wavelengths centered at about 780 nanometers. Thus, the first excited state |2> of the rubidium atom is |5P| 3 / 2 The first combined beam OPT CPL1In response to the first combined beam OPT, the excited population of alkali metal atoms can be further excited to a second excited state |3>. CPL1 The second excited state |3> is |5D 5 / 2 The second combined beam OPT may have a wavelength of about 776 nanometers. CPL2 In response to the excitation, the excited population of alkali metal atoms is further excited to the first Rydberg energy state |4>, which is excited by the probe beam OPT PRB Furthermore, as mentioned above, the split signal RF SPL may be provided to the sensor cell 202, resulting in a quantum superposition of alkali metal atoms in a first Rydberg energy state |4> and a second Rydberg energy state |5>. SPL When the first Rydberg energy state, |4>, has a frequency approximately equal to the energy difference between the first Rydberg energy state, |5>, a pair of Outler-Townes transparency peaks in the frequency spectrum can be well-defined and detectable.

[0023] Graph 304 shows the detection beam OPT plotted as a function of frequency detuning (in megahertz) from the |1> to |2> transition frequency. DET 3, the graph 304 is centered at zero frequency detuning, which exhibits a transparency peak, generally indicated at 308, corresponding to electromagnetically induced transparency between states |1>, |2>, and |3>.

[0024] Combined probe beam OPT CMB , Combined Beam OPT CPL1 , OPT CPL2 , and the split signal RF SPL Based on the positional interaction of the alkali metal atom with |4>, the alkali metal atom may exhibit a transition between the first and second Rydberg states |4> and |5>. Thus, the split signal RF SPLApplication of the split signal RF may result in a pair of Outler-Townes transparency peaks, generally indicated at 310. In the example of FIG. 3, the Outler-Townes transparency peaks are SPL Based on the frequency of the optical fiber, the Outler-Townes transmission peak 310 is located approximately equal to the transmission peak at zero detuning and detuned approximately +15 MHz and -15 MHz on either side of the transmission peak at zero detuning. DET is shown to have a much larger transmission peak at zero detuning, and thus the alkali metal vapor is able to achieve a combined probe beam OPT at each of the two detuning frequencies, approximately +15 MHz and -15 MHz from the transmission peak at zero detuning. CMB It is possible for the optical fiber to be substantially insensitive to absorption of photons of light.

[0025] Graph 306 shows the detection beam OPT plotted as a function of frequency detuning (in megahertz) from the |1> to |2> transition frequency. DET 3, graph 306 is aligned with graph 304 with respect to frequency detuning. Thus, as shown in graph 306, there is a phase shift of approximately zero at each of the transparency peaks 308 associated with electromagnetically induced transparency between states |1>, |2>, and |3>, and the Outler-Townes transparency peaks 310. However, with very small changes in the split field, the individual Outler-Townes transparency peaks 310 will shift in frequency, causing the detection beam OPT DET experiences a significant phase shift. Therefore, as described herein, the sensor control system 210 controls the detection beam OPT DET The phase of the external signal RF EXT The device is configured to detect

[0026] As mentioned above, the combined probe beam OPT CMB The first and second probe beams forming the combined probe beam OPT are each tuned to a frequency associated with the Outler-Townes transmission peak 310. Thus, in the example of FIG.CMB The first and second probe beams forming the Rydberg energy state 308 may be tuned to frequencies of about +15 MHz and about −15 MHz, respectively, detuned from the transmission peak 308 associated with the first Rydberg energy state. EXT In response to, the Outler-Townes transmission peak 310 can move (e.g., outward) relative to the detuning shown in graph 306 and thus can be further detuned from the frequency of the transmission peak 308. As a result, the detection beam OPT DET is the external signal RF EXT Thus, the sensor control system 210 can control the detection beam OPT DET Based on monitoring the phase of the external signal RF EXT The presence of can be determined.

[0027] Figure 4 shows another example of an electrometer system 400. The electrometer system 400 may correspond to a portion of the electrometer system 200 in the example of Figure 2. Therefore, in the following description of the example of Figure 4, reference is made to the example of Figure 3.

[0028] The electrometer system 400 includes a sensor cell 402, which may be configured as a sealed glass vessel containing an alkali metal vapor. The electrometer system 400 also includes a probe beam OPT. PRB and a probe laser 404 configured to generate a first combined beam OPT CPL1 and a first combined laser 406 configured to generate a first combined beam OPT CPL2 and a second coupled laser 408 configured to generate a probe beam OPT. PRB is provided to a sensor control system 410. The sensor control system 410 may, for example, control the probe beam OPT based on a set of optical systems. PRB into a number of different beams.

[0029] Probe beam OPT PRBis the first probe beam OPT PRB1 is provided to a first acousto-optic modulator (AOM) 412 to generate a second probe beam OPT PRB2 and a third probe beam OPT PRB3 and a fourth probe beam OPT PRB4 The first AOM 412 provides a probe beam OPT PRB is shifted by an amount Δ1 to obtain the first probe beam OPT PRB1 The first probe beam OPT is configured to provide PRB1 is provided to a saturation spectroscopy element ("SAT SPEC (saturation spectroscopy)") 420, which may correspond to a sensor cell containing the same alkali metal atom (e.g., Rb) as the sensor cell 402 and an associated spectroscopic detection system (e.g., including a first photodetector). Thus, the saturation spectroscopy element 420 detects the probe beam OPT PRB 404 to generate a tuning signal T that is provided to the probe laser 404 to cause frequency locking of the probe beam OPT PRB The frequency of is expressed as follows: p,0 can be locked to

[0030]

number

[0031] Here, ω p,1 is the first probe beam OPT PRB1 and is therefore the transition frequency to the first excited state of the alkali metal atom, Δ1 is the frequency shift provided by the first AOM 412.

[0032] The second AOM414 is the probe beam OPT. PRBis shifted by an amount Δ2 to obtain the second probe beam OPT PRB2 Similarly, the third AOM 416 is configured to provide a probe beam OPT PRB is shifted by an amount Δ3 to obtain the third probe beam OPT PRB3 Thus, as an example, a second probe beam OPT responsive to the second acousto-optic modulator 414 is PRB2 Frequency ω p,2 , and a third probe beam OPT responsive to a third acousto-optic modulator 416 PRB3 Frequency ω p,3 can be expressed as follows, respectively:

[0033]

number

[0034]

number

[0035] where Δ2 is the frequency shift provided by the second AOM 414, Δ3 is the frequency shift provided by the third AOM 416. Second and third probe beam OPT PRB2 , OPT PRB3 are the second and third probe beams OPT PRB2 , OPT PRB3 Combined probe beam OPT CMB A second probe beam OPT is also provided to a beam combiner 422 configured to form a second probe beam OPT PRB2 is provided to a second photodetector (e.g., photodiode) 424, which detects the third probe beam OPT PRB3 is provided to a third photodetector 426. The second photodetector 424 detects the second probe beam OPT PRB2 and a third photodetector 426 is configured to generate a second detection signal V2 corresponding to the intensity of the third probe beam OPT PRB3The second and third detection signals V2, V3 correspond to the intensities of the respective second and third probe beams OPT PRB2 , OPT PRB3 The combined probe beam OPT can be implemented as a feedback to control the intensity of the combined probe beam to substantially cancel the output intensity related noise. CMB are collinear second and third probe beams OPT PRB2 , OPT PRB3 2 (e.g., launched into a fiber) is provided through the sensor cell 402 (e.g., via a set of optics) in a manner similar to that described above in the corresponding example of FIG. CMB is the detection beam OPT DET 402 as emanating from the sensor cell 402.

[0036] The fourth AOM418 is the probe beam OPT. PRB is shifted by an amount Δ4 to obtain the fourth probe beam OPT PRB4 As an example, a fourth probe beam OPT in response to the fourth AOM 418 is configured to provide PRB4 Frequency ω p,4 can be expressed as follows:

[0037]

number

[0038] where Δ4 is ​​the frequency shift provided by the fourth AOM 418. In the example of Figure 4, the fourth probe beam OPT PRB4 is the fourth probe beam OPT PRB4 The combined probe beam OPT is split to be provided to a fourth photodetector 430 which generates a fourth detection signal V4 corresponding to the intensity of the combined probe beam OPT. CMB is provided to a fifth photodetector 432 which generates a fifth detection signal V5 corresponding to the intensity of the combined probe beam OPTPRBCMB. In addition, a fourth probe beam OPT PRB4is the fourth probe beam OPT PRB4 Detect beam OPT DET In combination with the output beam OPT OUT The output beam OPT is provided to a beam combiner 434 configured to provide an output beam OPT. OUT is the output beam OPT OUT The sixth detection signal V6 corresponds to the intensity of the reflected light from the sixth photodetector 436.

[0039] In the example in Figure 4, the combined beam OPT CPL1 , OPT CPL2 is the combined beam OPT CPL1 , OPT CPL2 The collinear beam OPT CPL3 The collinear beams are then combined into a beam combiner 438. CPL3 is combined with the beam splitter 214 (e.g., via the beam splitter 214 in the example of FIG. 2) CMB 4. The combined beam OPT is provided to pass through the sensor cell 402 in a manner that is collinear and antiparallel to the CMB and collinear beam OPT CPL3 can excite an alkali metal atom to the first Rydberg energy state |4> as described above in the example of Figure 3. In the example of Figure 4, the collinear beam OPT CPL3 For ease of explanation, we use the detection beam OPT as an example. DET Although shown separately, the associated optics are collinear beam OPT CPL3 and detection beam OPT DET can be provided collinearly and anti-parallel.

[0040] The sensor control system 410 receives an external signal RF EXT The voltage V5 can be expressed as a beat note signal as follows:

[0041]

number

[0042] Here, E p,2 is the second probe beam OPT PRB2 is the electric field of E p,3 is the third probe beam OPT PRB3 is the electric field of φ2 path is the second probe beam OPT PRB2 is the phase of the optical path of φ3 path is the third probe beam OPT PRB3 is the phase of the optical path.

[0043] In Equation 5, the sum term in the argument of the cosine quickly averages out to zero in time, but the difference frequency can be tracked. Therefore, Equation 5 can be rewritten as

[0044]

number

[0045] In the example of FIG. 4, the sensor control system 410 receives a reference signal V REF As an example, the reference signal V REF can have the same frequency as the fifth detection signal V5. Therefore, the fifth detection signal V5 can be used as a beat note signal comparison with the reference signal V REF Compared with signal path φ2 path -φ3 path Therefore, the difference between the phases of the fifth detection signal V5 and the reference signal V REF Based on the comparison with the signal path φ2 path -φ3 path The phase difference can be elucidated.

[0046] The sixth detection signal V6 can be expressed as follows:

[0047]

number

[0048] Here, E' p,2 is the detection beam OPT DET A second probe beam OPT, such as that occurring at PRB2 is the decaying electric field of E' p,3 is the detection beam OPT DET A third probe beam OPT, such as that occurring at PRB3 is the electric field of φ cell is the phase change resulting from the sensor cell 402, φ2 R is the detection beam OPT DET The second probe beam OPT to one of the Outler-Townes transmission peaks, such as occurs in PRB2 is the phase of φ3 R is the detection beam OPT DET A third probe beam OPT to the other of the Outler-Townes transmission peaks, such as occurs in PRB3 is the phase of E p,4 is the fourth probe beam OPT PRB4 is the electric field of φ4 PATH is the fourth probe beam OPT PRB4 is the phase of the optical path.

[0049] Similar to what was discussed above with respect to the fifth detected signal V5, in Equation 7, the sum term in the cosine argument quickly averages to zero in time, but the difference frequency can be tracked. Thus, Equation 7 can be rewritten as:

[0050]

number

[0051] In evaluating Equation 8, E p,4 Therefore, as long as the equation Δ2-Δ4 ≠ Δ3-Δ4 is ​​valid, E'p,2 and E' p,3 The value of E' can be identified. p,2 and E' p,3 The values ​​of Δ can be fed back as approximately equal values ​​to control the value of the frequency shift Δ1. Thus, the Outler-Townes transmission peaks 310 can be maintained at approximately equal magnitudes and therefore symmetrical about the transmission peak 308 of the first Rydberg energy state. This allows the detection beam OPT DET In determining the phase difference, the frequency variation can be cancelled.

[0052] Based on the detection signal V5, the formula φ2 path -φ3 path are the second and third probe beams OPT PRB2 , OPT PRB3 are known before being combined by the beam combiner 422. The second and third probe beams OPT PRB2 , OPT PRB3 are combined to form the combined beam OPT CMB After forming the formula φ2 path -φ3 path is equal to zero. Therefore, the term in the detection signal V6 that oscillates as Δ2-Δ3 is equal to the reference signal V REF The result is the beat in the electronic circuitry of the sensor control system 410 for φ2 R -φ3 R This will be determined.

[0053] external signal RF EXT If there is no split signal RF SPL is the formula φ2 R -φ3 R = 0. However, the external signal RF EXT When the outler-townes transmission peak 310 is present, it moves to either side (converging or diverging in the frequency spectrum), and therefore, φ R -φ3 R≠0. Any noise (such as frequency noise associated with the probe laser 404) that can shift the Outler-Townes transmission peak 310 in the same direction will be R -φ3 R is still zero, so it can be suppressed.

[0054] Therefore, the external signal RF EXT The amplitude modulation of the external signal RF results in a modulation of the separation of the Outler-Townes transparency peaks 310. As a result, the sensor control system 410 EXT φ2 R -φ3 R In addition, it is possible to detect non-zero values ​​of the external signal RF EXT is the known split signal RF in alkali atoms SPL When combined with the external signal RF, the phase and frequency modulation can be converted to amplitude modulation by the sensor control system 410. Thus, the sensor control system 410 receives the external signal RF EXT The signal characteristics can be identified.

[0055] In view of the structural and functional features discussed above, methods according to various embodiments of the present disclosure may be better understood with reference to Figure 5. It should be understood and appreciated that some aspects, according to the present disclosure, may occur in a different order and / or simultaneously with other aspects than as shown and described herein, and therefore the method of Figure 5 is not limited by the order shown. Furthermore, not all illustrated features are required to practice a method according to an embodiment of the present example.

[0056] FIG. 5 illustrates an example of an external signal (e.g., external signal RF) being applied through an electrometer system (e.g., electrometer system 100). EXT 5 shows an example of a method 500 for detecting a probe beam (e.g., a probe beam OPT). PRB ) is directed in a first direction through a sensor cell (e.g., sensor cell 102) that includes alkali metal atoms. At 504, a combined beam (e.g., combined beam OPTCPL ) is shone through the sensor cell collinearly and anti-parallel to the probe beam to induce Rydberg energy states in the alkali metal atoms. At 506, a split signal having a predetermined frequency (e.g., split signal RF SPL ) is provided through the sensor cell to produce a pair of Outler-Townes frequency spectrum transmission peaks associated with the alkali metal atoms. At 508, a detection beam (e.g., detection beam OPT DET ) is monitored relative to at least one of a pair of Outler-Townes frequency spectrum transparency peaks. The detection beam can correspond to a probe beam exiting the sensor cell.

[0057] The above are examples of the present invention. Of course, it is not possible to describe every conceivable combination of elements or methods for purposes of describing the present invention, but one skilled in the art will recognize that many more combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. In addition, when the disclosure or claims recite "a," "an," "a first," or "another" element, or the equivalent thereof, it should be construed as including one or more such elements, and does not require or exclude two or more such elements. As used herein, the term "includes" means including but not limited to, and the term "including" means including but not limited to. The term "based on" means based at least in part on. The technical ideas that can be understood from the above-described embodiment will be described below as supplementary notes. [Appendix 1] 1. An electrometer system comprising: A sensor cell containing an alkali metal atom therein; a probe laser configured to generate a probe beam that is provided through the sensor cell; a combined laser configured to generate a combined beam, the combined beam being provided through the sensor cell to combine with the probe beam provided through the sensor cell to produce a Rydberg energy state of the alkali metal atom, the probe beam exiting the sensor cell as a detection beam; a sensor control system configured to monitor the detection beam and to detect an external signal based on monitoring a phase of the detection beam. [Appendix 2] 2. The system of claim 1, further comprising a split signal generator configured to generate a split signal having a predetermined frequency passing through the sensor cell, the split signal resulting in a pair of Outler-Townes frequency spectrum transparency peaks for the Rydberg energy state associated with the alkali metal atom, wherein the sensor control system is configured to detect the external signal based on a phase of the detection beam associated with at least one of the pair of Outler-Townes frequency spectrum transparency peaks. [Appendix 3] 2. The system of claim 1, wherein the sensor control system is configured to split the probe beam into a first probe beam and a second probe beam that are each fed through the sensor cell as a combined light beam, the first probe beam and the second probe beam having respective frequencies approximately equal to and on either side of a frequency spectrum transparency peak associated with the Rydberg energy state, and the detection beam corresponds to the combined light beam exiting the sensor cell. [Appendix 4] The sensor control system includes: a first photodetector configured to monitor a combined optical signal at an input of the sensor cell; and a second optical detector configured to monitor the detection beam at the output of the sensor cell, wherein the sensor control system is configured to compare the monitored combined optical signal to the monitored detection beam to eliminate relative signal path phase differences between the first probe beam and the second probe beam. [Appendix 5] 5. The system of claim 4, wherein the sensor control system further includes a reference signal generator configured to generate a reference signal, the monitored combined optical signal being compared to the reference signal to generate a first beat signal and the monitored detection beam being compared to the reference signal to generate a second beat signal, and the sensor control system is configured to compare the monitored combined optical signal to the monitored detection beam based on a comparison of the first beat signal and the second beat signal. [Appendix 6] 4. The system of claim 3, wherein the sensor control system is configured to split the probe beam into the first probe beam, the second probe beam, and a third probe beam, and the third probe beam is combined with the detection beam to determine power associated with the first and second probe beams to stabilize a frequency associated with a Rydberg energy state of the alkali metal atom. [Appendix 7] 4. The system of claim 3, further comprising a split signal generator configured to generate a split signal having a predetermined frequency that passes through the sensor cell to produce a pair of Outler-Townes frequency spectrum transparency peaks for a Rydberg energy state associated with the alkali metal atom, wherein the sensor control system is configured to detect the external signal based on the phase of the first and second probe beams relative to each pair of Outler-Townes frequency spectrum transparency peaks as provided in the detection beam. [Appendix 8] 2. The system of claim 1, wherein the combined beam is a first combined beam, the system further comprising a second combined beam, the first and second combined beams combining to form a combined combined beam provided to pass through the sensor cell for combining with the probe beam provided to pass through the sensor cell to produce a Rydberg energy state of the alkali metal atom. [Appendix 9] 2. The system of claim 1, further comprising an optical system configured to collimate the probe beam and the combined beam to provide the probe beam and the combined beam collinear and anti-parallel to one another, such that the sensor control system is configured to monitor the detection beam along an axis passing through the sensor cell to detect the external signal. [Appendix 10] 1. A method for detecting an external signal via an electrometer system, comprising: directing a probe beam in a first direction through a sensor cell containing alkali metal atoms; illuminating the sensor cell with a combined beam collinear and anti-parallel to the probe beam to generate Rydberg energy states of the alkali metal atoms; providing a split signal having a predetermined frequency passing through the sensor cell to produce a pair of Outler-Townes frequency spectrum transmittance peaks for the Rydberg energy states associated with the alkali metal atoms; and detecting the external signal by monitoring a phase of a detection beam relative to at least one of the pair of Outler-Townes frequency spectrum transparency peaks, the detection beam corresponding to the probe beam exiting the sensor cell. [Appendix 11] splitting the probe beam into a first probe beam and a second probe beam, each of which is provided to pass through the sensor cell as a combined light beam; and the detection beam corresponds to the combined light beam exiting the sensor cell; 11. The method of claim 10, further comprising setting the first probe beam and the second probe beam to have respective frequencies approximately equal to frequencies associated with Outler-Townes frequency spectrum transparency peaks of respective pairs. [Appendix 12] monitoring a combined optical signal at an input of the sensor cell; monitoring the detection beam at the output of the sensor cell; 12. The method of claim 11, further comprising comparing the monitored combined optical signal to the monitored detection beam to account for relative signal path phase differences between the first probe beam and the second probe beam. [Appendix 13] The step of comparing the monitored combined optical signal with the monitored detection beam further comprises the step of generating a reference signal, comparing the monitored combined optical signal with the reference signal to generate a first beat signal; comparing the monitored detection beam with the reference signal to generate a second beat signal; 13. The method of claim 12, comprising comparing the monitored combined optical signal to the monitored detection beam based on comparing the first beat signal and the second beat signal. [Appendix 14] splitting the probe beam into the first probe beam, the second probe beam, and a third probe beam; combining the third probe beam with the detection beam; determining powers associated with the first and second probe beams based on the monitored detection beam; stabilizing a frequency associated with the Rydberg energy state of the alkali metal atom based on the power associated with the first and second probe beams. [Appendix 15] irradiating the combined beam includes: combining the first combined beam and the second combined beam to generate a combined combined beam; 13. The method of claim 12, comprising providing the combined beam collinearly and anti-parallel to the probe beam through the sensor cell to produce Rydberg energy states of the alkali metal atoms. [Appendix 16] 1. An electrometer system comprising: A sensor cell containing an alkali metal atom therein; a probe laser configured to generate a probe beam; a combined laser configured to generate a combined beam that is provided through the sensor cell; a split signal generator configured to generate a split signal having a predetermined frequency that passes through the sensor cell to produce a pair of Outler-Townes frequency spectrum transmission peaks associated with the alkali metal atoms; and a sensor control system configured to split the probe beam into a first probe beam and a second probe beam, each of which is provided to pass through the sensor cell as a combined light beam and to exit the sensor cell as a detection beam, the first probe beam and the second probe beam having respective frequencies approximately equal to frequencies associated with respective pairs of Outler-Townes frequency spectrum transmission peaks, the combined light beam and the combined beam giving rise to Rydberg energy states of the alkali metal atoms, the sensor control system being further configured to monitor the detection beam and detect an external signal based on monitoring a phase of the detection beam relative to at least one of the Outler-Townes frequency spectrum transmission peaks. [Appendix 17] The sensor control system includes: a first photodetector configured to monitor a combined optical signal at an input of the sensor cell; and a second optical detector configured to monitor the detection beam at the output of the sensor cell, wherein the sensor control system is configured to compare the monitored combined optical signal to the monitored detection beam to eliminate relative signal path phase differences between the first probe beam and the second probe beam. [Appendix 18] 18. The system of claim 17, wherein the sensor control system further includes a reference signal generator configured to generate a reference signal, the monitored combined optical signal being compared to the reference signal to generate a first beat signal and the monitored detection beam being compared to the reference signal to generate a second beat signal, and the sensor control system is configured to compare the monitored combined optical signal to the monitored detection beam based on comparing the first beat signal and the second beat signal. [Appendix 19] 17. The system of claim 16, wherein the sensor control system is configured to split the probe beam into the first probe beam, the second probe beam, and a third probe beam, and the third probe beam is combined with the detection beam to determine power associated with the first and second probe beams to stabilize a frequency associated with a Rydberg energy state of the alkali metal atom. [Appendix 20] 17. The system of claim 16, wherein the combined beam is a first combined beam, the system further including a second combined beam, the first and second combined beams combining to form a combined combined beam provided through the sensor cell for combining with the probe beam provided through the sensor cell to produce a Rydberg energy state of the alkali metal atom.

Claims

1. 1. An electrometer system comprising: A sensor cell containing an alkali metal atom therein; a probe laser configured to generate a probe beam; a sensor control system configured to split the probe beam into a first probe beam and a second probe beam each provided to pass through the sensor cell as a combined probe beam, the first probe beam and the second probe beam having respective frequencies approximately equal to and on either side of a frequency spectrum transmission peak associated with a Rydberg energy state of the alkali metal atom; a combined laser configured to generate a combined beam, the combined beam being provided through the sensor cell and combining with the combined probe beam provided through the sensor cell to produce the Rydberg energy state of the alkali metal atom; the combined probe beam passes through the sensor cell and then exits the sensor cell as a detection beam; The sensor control system is configured to monitor the detection beam and detect an external signal based on monitoring a phase of the detection beam.

2. 2. The system of claim 1, further comprising a split signal generator configured to generate a split signal having a predetermined frequency passing through the sensor cell, the split signal resulting in a pair of Outler-Townes frequency spectrum transparency peaks for the Rydberg energy state associated with the alkali metal atom, and wherein the sensor control system is configured to detect the external signal based on a phase of the detection beam associated with at least one of the pair of Outler-Townes frequency spectrum transparency peaks.

3. The sensor control system includes: a first photodetector configured to monitor the combined probe beam at an input of the sensor cell; and a second photodetector configured to monitor the detection beam at the output of the sensor cell, wherein the sensor control system is configured to compare the monitored combined probe beam to the monitored detection beam to eliminate relative signal path phase differences between the first and second probe beams.

4. 4. The system of claim 3, wherein the sensor control system further includes a reference signal generator configured to generate a reference signal, the monitored combined probe beam being compared to the reference signal to generate a first beat signal and the monitored detection beam being compared to the reference signal to generate a second beat signal, and the sensor control system is configured to compare the monitored combined probe beam to the monitored detection beam based on a comparison of the first beat signal and the second beat signal.

5. 2. The system of claim 1, wherein the sensor control system is configured to split the probe beam into the first probe beam, the second probe beam, and a third probe beam, and the third probe beam is combined with the detection beam to determine powers associated with the first and second probe beams to stabilize a frequency associated with a Rydberg energy state of the alkali metal atom.

6. 2. The system of claim 1, further comprising a split signal generator configured to generate a split signal having a predetermined frequency that passes through the sensor cell to produce a pair of Outler-Townes frequency spectrum transmission peaks for a Rydberg energy state associated with the alkali metal atom, the sensor control system configured to detect the external signal based on a phase of the first and second probe beams relative to each pair of Outler-Townes frequency spectrum transmission peaks as provided in the detection beam.

7. 2. The system of claim 1, wherein the combined beam is a first combined beam, the system further comprising a second combined beam, the first and second combined beams being combined to form a combined combined beam that is provided through the sensor cell for combining with the combined probe beam that is provided through the sensor cell to produce a Rydberg energy state of the alkali metal atom.

8. 2. The system of claim 1 , further comprising an optical system configured to collimate the combined probe beam and the combined beam to provide the combined probe beam and the combined beam collinear and anti-parallel with respect to one another, such that the sensor control system is configured to monitor the detection beam along an axis passing through the sensor cell to detect the external signal.

9. 1. A method for detecting an external signal via an electrometer system, comprising: directing a probe beam in a first direction through a sensor cell containing alkali metal atoms; illuminating the sensor cell with a combined beam collinear and anti-parallel to the probe beam to generate Rydberg energy states of the alkali metal atoms; providing a split signal having a predetermined frequency passing through the sensor cell to produce a pair of Outler-Townes frequency spectrum transmittance peaks for the Rydberg energy states associated with the alkali metal atoms; and detecting the external signal by monitoring a phase of a detection beam relative to at least one of the pair of Outler-Townes frequency spectrum transparency peaks, the detection beam corresponding to the probe beam exiting the sensor cell after passing through the sensor cell.

10. splitting the probe beam into a first probe beam and a second probe beam, each of which is provided to pass through the sensor cell as a combined light beam; and the detection beam corresponds to the combined light beam exiting the sensor cell; 10. The method of claim 9, further comprising: setting the first probe beam and the second probe beam to have respective frequencies approximately equal to frequencies associated with respective pair of Outler-Townes frequency spectrum transparency peaks.

11. monitoring a combined optical signal at an input of the sensor cell; monitoring the detection beam at the output of the sensor cell; 11. The method of claim 10, further comprising: comparing the monitored combined optical signal to the monitored detection beam to account for relative signal path phase differences between the first probe beam and the second probe beam.

12. The step of comparing the monitored combined optical signal with the monitored detection beam further comprises the step of generating a reference signal, comparing the monitored combined optical signal with the reference signal to generate a first beat signal; comparing the monitored detection beam with the reference signal to generate a second beat signal; 12. The method of claim 11, comprising comparing the monitored combined optical signal to the monitored detection beam based on comparing the first beat signal and the second beat signal.

13. splitting the probe beam into the first probe beam, the second probe beam, and a third probe beam; combining the third probe beam with the detection beam; determining powers associated with the first and second probe beams based on the monitored detection beam; 12. The method of claim 11, further comprising: stabilizing a frequency associated with the Rydberg energy state of the alkali metal atom based on the power associated with the first and second probe beams.

14. irradiating the combined beam includes: combining the first combined beam and the second combined beam to generate a combined combined beam; 12. The method of claim 11, comprising providing the combined beam collinearly and anti-parallel to the probe beam passing through the sensor cell to produce Rydberg energy states of the alkali metal atoms.

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