Rydberg atom microwave electric field measurement system and method

Abstract

The invention discloses a Rydberg atom microwave electric field measurement system which comprises a detection unit, a laser unit and a reference unit. The detection unit comprises a narrow linewidth detection laser, an optical fiber type acousto-optic modulator, a first optical fiber collimator, a first half slide, a first beam splitter prism, a reflector, a first atomic gas chamber, a first electrode plate, a first semi-reflecting and semi-transmitting mirror and a balanced photoelectric detector; the laser unit comprises a second optical fiber collimator, a second half slide, a first microwave anechoic chamber, a second atomic gas chamber, a second semi-reflecting and semi-transmitting mirror, a photoelectric detector, a PID (Proportion Integration Differentiation) controller, a narrow linewidth coupling laser, a third half slide and a polarization splitting prism; the reference unit comprises a fourth half slide, a second beam splitter prism, a second microwave anechoic chamber, a second electrode plate and a third atomic gas chamber; the invention further discloses a measuring method. The influence of an environmental electromagnetic field is reduced, the signal-to-noise ratio of the microwave electric field intensity measured by a superheterodyne scheme is improved, and the stability of the system is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of quantum precision measurement, and in particular relates to a Rydberg atom microwave electric field measurement system and a measurement method. Background Art

[0002] Rydberg atoms have a large electric dipole moment and can precisely measure microwave electric fields at room temperature. They have broad application prospects in terahertz imaging, radar, communications and other fields.

[0003] Currently, the best solution for measuring microwave electric fields of Rydberg atoms is the superheterodyne method, but it is greatly disturbed by environmental electromagnetic waves, resulting in poor stability of the system and inability to perform long-term stable measurements.

[0004] In addition, the fluctuation of the local field in the superheterodyne method will also cause the drift of the optimal measurement point, affecting the sensitivity of measuring the microwave electric field. Summary of the invention

[0005] In view of the above deficiencies in the prior art, one of the objectives of the present invention is to provide a Rydberg atom microwave electric field measurement system.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a Rydberg atomic microwave electric field measurement system, which mainly includes three parts: a detection unit, a laser unit and a reference unit; the detection unit includes a fiber-optic acousto-optic modulator, a first fiber-optic collimator, a first half-glass and a first beam splitter prism which are sequentially arranged on a laser output optical path of a narrow line width detection laser; a reflector, a first atomic gas chamber wrapped by a first electrode plate, a first half-reflective half-mirror and a balanced photoelectric detector are sequentially arranged on an optical path separated by the first beam splitter prism; a third atomic gas chamber is arranged on another optical path separated by the first beam splitter prism; the laser unit includes a second optical path which is secondarily arranged on another laser output optical path of the narrow line width detection laser The invention also comprises a second optical fiber collimator, a second half glass slide, a second atomic gas chamber wrapped in a first microwave darkroom, a second half-reflective half-mirror and a photoelectric detector, and also comprises a narrow linewidth coupling laser and a second half glass slide and a polarization beam splitter prism which are sequentially arranged on the laser output light path of the narrow linewidth coupling laser, the second half-reflective half-mirror is located on a light path separated by the polarization beam splitter prism, and a PID controller is connected between the photoelectric detector and the narrow linewidth coupling laser; the reference unit comprises a third half glass slide and a second beam splitter prism which are located on another light path separated by the polarization beam splitter prism, and a third atomic gas chamber which is located between the first beam splitter prism and the second beam splitter prism and is wrapped by the second microwave darkroom and the second electrode plate.

[0007] The second purpose of the present invention is to provide a microwave electric field measurement method based on the Rydberg atom differential heterodyne method to solve the problems of poor stability and low sensitivity of the traditional heterodyne method for measuring the microwave electric field, and to eliminate the influence of local field jitter and environmental electromagnetic field through the differential heterodyne method to improve the sensitivity of measuring the microwave electric field.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a method for measuring the microwave electric field of a Rydberg atom, comprising the following steps:

[0009] S1, turn on the narrow linewidth detection laser, a detection laser beam emitted by the narrow linewidth detection laser enters the fiber collimator after frequency shifting by the fiber acousto-optic modulator and becomes spatial light, enters the first beam splitter prism after polarization rotation by the first half glass slide, and after the detection laser is split by the first beam splitter prism, the half-power laser is reflected by the reflector and enters the first atomic gas chamber, and after being absorbed by the first atomic gas chamber, it is transmitted from the first half-reflecting half-mirror into one of the detection target surfaces of the balanced photodetector;

[0010] S2, another laser beam of the narrow linewidth detection laser enters the second fiber collimator and becomes spatial light, and enters the second atomic gas chamber after being polarized by the second half glass slide; the narrow linewidth coupling laser is turned on, and the laser emitted by the narrow linewidth coupling laser is polarized by the third half glass slide, and one of the laser beams passes through the polarization splitter prism and the second half-reflective half-mirror and interacts with the laser beam emitted by the narrow linewidth detection laser in the second atomic gas chamber; due to the EIT effect, the transmitted detection laser is finally collected by the photodetector, and the frequency of the coupled laser is locked to the peak value of the EIT signal collected by the photodetector through the feedback of the PID controller;

[0011] S3, the locked coupling laser is reflected by the polarization beam splitter prism and then rotated by the polarization of the fourth half glass slide, and then split into two by the second beam splitter prism, one beam passes through the second beam splitter prism and then reflects from the first half-reflective half-mirror lens and then interacts with the detection laser in the first atomic gas chamber, the other beam is reflected by the second beam splitter prism and then enters the third atomic gas chamber, interacts with one of the detection lasers reflected by the first beam splitter prism in the third atomic gas chamber, and finally the detection laser passes through the second beam splitter prism and enters another target surface of the balanced photodetector;

[0012] S4, applying the same voltage to the first electrode plate and the second electrode plate respectively, so that an electric field is generated between the electrode plates;

[0013] S5, the entire measurement system is placed in a microwave electric field, and the intensity of the signal microwave electric field can be directly measured by a balanced photoelectric detector.

[0014] Further, the step S4 is specifically as follows:

[0015] S41, applying a voltage V1 and a frequency ω1 to the first electrode plate, and the electric field frequency ω1 satisfies With the rubidium 85 atomic energy level nD 5 / 2 -(n+1)P 3 / 2 The intervals are equal, and the frequency of the fiber-optic acousto-optic modulator is scanned Δ P The transmission spectrum U(Δ P ) and do a bimodal fit, adjusting the value of V1 so that

[0016] S42, use a standard signal generator to apply a signal with a power of P1 and a frequency of ω1 to the standard antenna, and calculate the electric field strength at the first atomic gas chamber: η is the free space impedance, g is the gain of the horn antenna, α is the loss between the microwave source and the antenna, P1 is the output power of the signal generator, and D is the distance from the antenna to the laser in the atomic gas chamber. Read the amplitude V0 of the balanced photodetector at this time and calculate

[0017] Further, the step S5 is specifically as follows: placing the measurement system in a microwave electric field with a frequency of ω1, and reading the signal amplitude V of the balanced photodetector s , then the microwave electric field intensity is E s = k × V s .

[0018] Furthermore, in step S1, the narrow linewidth detection laser is tuned to lock the laser frequency to the 5S 1 / 2 -5P 3 / 2 energy level, where 5 is the principal quantum number, S and P represent orbital angular momentum, and 1 / 2 and 3 / 2 represent total angular momentum; in step S2, the narrow linewidth coupled laser is tuned to lock the laser frequency at 85 atoms of 5P 3 / 2 -nD 5 / 2 , where n is the principal quantum number, P and D represent orbital angular momentum, and 3 / 2 and 5 / 2 represent total angular momentum.

[0019] The beneficial effects of the present invention are:

[0020] (1) Reduce the impact of environmental electromagnetic fields, improve the signal-to-noise ratio of the superheterodyne scheme to measure microwave electric field strength, and enhance the stability of the system;

[0021] (2) Eliminate the movement of the optimal measurement point caused by local field drift and improve the measurement sensitivity of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the measurement system of the present invention.

[0023] The figures are marked as follows: 01—narrow linewidth detection laser, 02—fiber acousto-optic modulator, 03—first fiber collimator, 04—first half glass slide, 05—first beam splitter prism, 06—reflector, 07—first atomic gas chamber, 08—first electrode plate, 09—first semi-reflective and semi-mirror, 10—balanced photodetector, 11—second fiber collimator, 12—second half glass slide, 13—first microwave darkroom, 14—second atomic gas chamber, 15—second semi-reflective and semi-mirror, 16—photodetector, 17—PID controller, 18—narrow linewidth coupled laser, 19—third half glass slide, 20—polarization beam splitter prism, 21—fourth half glass slide, 22—second beam splitter prism, 23—second microwave darkroom, 24—second electrode plate, 25—third atomic gas chamber. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Example 1

[0026] Reference Figure 1 As shown, a Rydberg atom microwave electric field measurement system disclosed in the present invention mainly includes three parts: a detection unit, a laser unit and a reference unit.

[0027] The detection unit includes a fiber-optic acousto-optic modulator 02, a first fiber-optic collimator 03, a first half-glass slide 04 and a first beam splitter prism 05, which are arranged in sequence on a laser output optical path of a narrow linewidth detection laser 01; a reflector 06, a first atomic gas chamber 07 wrapped by a first electrode plate 08, a first half-reflective half-mirror 09 and a balanced photodetector 10 are arranged in sequence on an optical path separated by the first beam splitter prism 05; a third atomic gas chamber 25 is arranged on another optical path separated by the first beam splitter prism 05.

[0028] The narrow linewidth detection laser 01 is used to generate a 780-nanometer detection laser; the fiber-optic acousto-optic modulator 02 is used to adjust the frequency of the detection laser; the first fiber collimator 03 is used to collimate the laser into spatial light; the first half-glass slide 04 is used to change the polarization direction of the detection laser; the first beam splitter prism 05 is used to split the 780-nanometer detection laser into two; the reflector 06 is used to reflect the detection laser; the first atomic gas chamber 07 is used to provide rubidium 85 atoms; the first electrode plate 08 is used to provide a local field; the first half-reflective half-mirror 09 is used to transmit the detection laser and reflect the 480-nanometer coupled laser; and the balanced photodetector 10 is used to detect the transmitted detection laser and make a difference.

[0029] The laser unit includes a second fiber collimator 11, a second half glass slide 12, a second atomic gas chamber 14 wrapped in a first microwave darkroom 13, a second half-reflective half-mirror 15 and a photodetector 16, which are arranged on another laser output optical path of the narrow linewidth detection laser 01. It also includes a narrow linewidth coupling laser 18 and a third half glass slide 19 and a polarization beam splitter prism 20 which are arranged in sequence on the laser output optical path of the narrow linewidth coupling laser 18. The second half-reflective half-mirror 15 is located on an optical path separated by the polarization beam splitter prism 20. A PID controller 17 is connected between the photodetector 16 and the narrow linewidth coupling laser 18.

[0030] The second fiber collimator 11 is used to convert the laser collimation into spatial light; the second half glass slide 12 is used to change the polarization direction of the detection laser; the first microwave darkroom 13 is used to shield the electromagnetic waves in the environment; the second atomic gas chamber 14 is used to provide rubidium 85 atoms; the second half-reflective half-mirror 15 is used to transmit the detection laser and reflect the coupling laser; the photodetector 16 is used to detect the transmitted detection laser; the PID controller 17 is used to provide feedback control to lock the laser frequency of 480 nanometers; the narrow linewidth coupling laser 18 is used to generate coupling laser; the third half glass slide 19 is used to change the polarization direction of the coupling laser; and the polarization splitter prism 20 is used to split the coupling laser into two.

[0031] The reference unit includes a fourth half glass 21 and a second beam splitter prism 22 located on another light path split by the polarization beam splitter prism 20 , and a third atomic gas chamber 25 located between the first beam splitter prism 05 and the second beam splitter prism 22 and surrounded by a second microwave darkroom 23 and a second electrode plate 24 .

[0032] The fourth half glass slide 21 is used to change the polarization direction of the coupled laser; the second beam splitter prism 22 is used to split the 480-nanometer coupled laser into two; the second microwave darkroom 23 is used to shield electromagnetic waves in the environment; the second electrode plate 24 is used to provide a local field; and the third atomic gas chamber 25 is used to provide rubidium 85 atoms.

[0033] Example 2

[0034] The present invention proposes a microwave electric field measurement method using a Rydberg atom differential heterodyne method, and the working process is as follows.

[0035] (1) Turn on the narrow linewidth detection laser 01 and lock its frequency to the 5S of the rubidium 85 atom. 1 / 2 -5P 3 / 2Energy level 5 is the principal quantum number, S and P represent orbital angular momentum, 1 / 2 and 3 / 2 represent total angular momentum, and a beam of locked 780-nanometer detection laser enters the first fiber collimator 03 and becomes spatial light after frequency shifting by the fiber acousto-optic modulator 02, and enters the first beam splitter prism 05 after polarization rotation by the first half glass slide 04. After the detection laser is split by the first beam splitter prism 05, half of the power laser is reflected by the reflector 06 and enters the first atomic gas chamber 07. After being absorbed by the rubidium atomic gas chamber, i.e. the first atomic gas chamber 07, it is transmitted from the first half-reflective half-mirror 09 into one of the detection target surfaces of the balanced photodetector 10.

[0036] (2) After the narrow linewidth detection laser 01 is locked, another beam of the detection laser enters the second fiber collimator 11 and becomes spatial light. After the polarization rotation of the second half glass slide 12, it enters the second atomic gas chamber 14. The narrow linewidth coupling laser 18 is turned on and the laser frequency is tuned to be within the frequency range of 5P of the rubidium 85 atom. 3 / 2 -nD 5 / 2 n is the principal quantum number, P and D represent orbital angular momentum, 3 / 2 and 5 / 2 represent scanning between total angular momentum energy levels, and the laser emitted by the narrow linewidth coupling laser 18 is polarized and rotated by the third half glass slide 19, and one of the laser beams passes through the polarization beam splitter prism 20 and the second half-reflective half-mirror 15, and then interacts with a laser beam emitted by the narrow linewidth detection laser 01 in the rubidium atomic gas chamber, i.e., the second atomic gas chamber 14. Due to the EIT effect, the transmitted detection laser is finally collected by the photodetector 16. The frequency of the coupling laser is locked to the peak value of the EIT signal collected by the photodetector 16 through the feedback of the PID controller 17.

[0037] (3), the locked coupling laser is reflected by the polarization beam splitter prism 20 and then rotated by the polarization of the fourth half glass 21, and then split into two by the second beam splitter prism 22. One beam passes through the second beam splitter prism 22 and then reflects from the first half-reflective half-mirror 09 and then interacts with the detection laser in the first atomic gas chamber 07. The other beam is reflected by the second beam splitter prism 22 and then enters the third atomic gas chamber 25, where it interacts with one of the detection lasers reflected by the first beam splitter prism 05. Finally, the detection laser passes through the second beam splitter prism 22 and then enters another target surface of the balanced photodetector 10.

[0038] (4) The same voltage is applied to the first electrode plate 08 and the second electrode plate 24, respectively, so that an electric field is generated between the electrode plates, and the electric field frequency ω1 satisfies With the rubidium 85 atomic energy level nD 5 / 2 -(n+1)P 3 / 2 The intervals are equal and n is the principal quantum number, which is the same as the value in step 2.

[0039] (5) The whole system is placed in a microwave electric field with a frequency of ω, and the intensity of the signal microwave electric field can be directly measured by the balanced photodetector 10.

[0040] A microwave electric field measurement method proposed in the present invention is described as follows.

[0041] (i) A voltage V1 and a frequency ω1 are applied to the first electrode plate 08. The value of the voltage ω1 is consistent with the ω1 in the above step 4, and the frequency Δ of the fiber acousto-optic modulator 02 is scanned. P The transmission spectrum U(Δ P ) and do a bimodal fit, adjusting the value of V1 so that

[0042] (ii) Use a standard signal generator to apply a signal with a power of P1 and a frequency of ω1 to the standard antenna, and calculate the electric field strength at the first atomic gas chamber 07 as: η is the free space impedance, g is the gain of the horn antenna, α is the loss between the microwave source and the antenna, P1 is the output power of the signal generator, and D is the distance from the antenna to the laser in the atomic gas chamber. Read the amplitude V0 of the balanced photodetector 10 at this time and calculate

[0043]

[0044] (iii) Place the measurement system in a microwave electric field with a frequency of ω1 and read the signal amplitude V of the balanced photodetector 10 s , then the microwave electric field intensity is E s = k × V s .

[0045] The above embodiments are only illustrative of the principles and effects of the present invention, as well as some embodiments of its application. For those skilled in the art, several modifications and improvements may be made without departing from the creative concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A Rydberg atom microwave electric field measurement system, characterized in that: The invention comprises a detection unit, a laser unit and a reference unit; the detection unit comprises a fiber-optic acousto-optic modulator (02), a first fiber-optic collimator (03), a first half-glass (04) and a first beam splitter (05) which are sequentially arranged on a laser output optical path of a narrow linewidth detection laser (01); a reflector (06), a first atomic gas chamber (07) wrapped by a first electrode plate (08), a first half-reflective half-mirror (09) and a balanced photodetector (10) are sequentially arranged on an optical path separated by the first beam splitter (05); a third atomic gas chamber (25) is arranged on another optical path separated by the first beam splitter (05); the laser unit comprises a second fiber-optic collimator (11), a second half-glass (12), a second half-mirror (13) wrapped by a first microwave darkroom (13) and a second half-mirror (14) which are sequentially arranged on another laser output optical path of the narrow linewidth detection laser (01). The invention relates to an atomic gas chamber (14), a second semi-reflective semi-mirror (15) and a photodetector (16), and also comprises a narrow linewidth coupling laser (18) and a third half glass slide (19) and a polarization beam splitter prism (20) which are sequentially arranged on the laser output light path of the narrow linewidth coupling laser (18), wherein the second semi-reflective semi-mirror (15) is located on a light path separated by the polarization beam splitter prism (20), and a PID controller (17) is connected between the photodetector (16) and the narrow linewidth coupling laser (18); the reference unit comprises a fourth half glass slide (21) and a second beam splitter prism (22) which are located on another light path separated by the polarization beam splitter prism (20), and a third atomic gas chamber (25) which is located between the first beam splitter prism (05) and the second beam splitter prism (22) and is wrapped by a second microwave darkroom (23) and a second electrode plate (24).

2. A measurement method of the microwave electric field measurement system as claimed in claim 1, characterized in that: The steps include: S1, a beam of detection laser emitted by a narrow linewidth detection laser (01) enters a fiber collimator (03) and becomes spatial light after being frequency shifted by a fiber acousto-optic modulator (02), and enters a first beam splitter prism (05) after being polarized and rotated by a first half glass slide (04). After the detection laser is split by the first beam splitter prism (05), half of the power of the detection laser is reflected by a reflector (06) and enters a first atomic gas chamber (07). After being absorbed by the first atomic gas chamber (07), the detection laser is transmitted from a first half-reflecting half-mirror (09) and enters one of the detection target surfaces of a balanced photodetector (10); S2, another laser beam of the narrow linewidth detection laser (01) enters the second fiber collimator (11) and becomes spatial light, and enters the second atomic gas chamber (14) after being polarized and rotated by the second half glass slide (12); the laser beam emitted by the narrow linewidth coupling laser (18) passes through the third half glass slide (19) and is polarized and rotated, and one of the laser beams passes through the polarization splitter prism (20) and the second half-reflective half-mirror (15) and interacts with the laser beam emitted by the narrow linewidth detection laser (01) in the second atomic gas chamber (14); the transmitted detection laser beam is collected by the photodetector (16), and the frequency of the coupled laser beam is locked at a peak value through feedback from the PID controller (17); S3, the locked coupling laser is reflected by the polarization beam splitter prism (20) and then polarized by the fourth half glass slide (21), and then split into two by the second beam splitter prism (22), one beam passes through the second beam splitter prism (22) and then reflects by the first half-reflective half-mirror (09) and then interacts with the detection laser in the first atomic gas chamber (07), the other beam is reflected by the second beam splitter prism (22) and then enters the third atomic gas chamber (25), and interacts with one of the detection lasers reflected by the first beam splitter prism (05) in the third atomic gas chamber (25), and finally the detection laser passes through the second beam splitter prism (22) and then enters another target surface of the balanced photodetector (10); S4, applying the same voltage to the first electrode plate (08) and the second electrode plate (24) respectively, so that an electric field is generated between the electrode plates; S5, placing the entire measuring system in a microwave electric field, and measuring the intensity of the signal microwave electric field through a balanced photoelectric detector (10).

3. A Rydberg atom microwave electric field measurement method according to claim 2, characterized in that: The step S4 is specifically as follows: S41, applying a voltage V1 and a frequency ω1 to the first electrode plate (08), the electric field frequency ω1 satisfies ω1 and the atomic energy level nD of rubidium 85 5 / 2 -(n+1)P 3 / 2 The intervals are equal, and the frequency Δ of the fiber-optic acousto-optic modulator (02) is scanned. P The transmission spectrum U(Δ P ) and do a bimodal fit, adjusting the value of V1 so that S42, using a standard signal generator to apply a signal with a power of P1 and a frequency of ω1 to the standard antenna, and calculating the electric field strength at the first atomic gas chamber (07) as η is the free space impedance, g is the gain of the horn antenna, α is the loss between the microwave source and the antenna, P1 is the output power of the signal generator, and D is the distance from the antenna to the laser in the atomic gas chamber. Read the amplitude V0 of the balanced photodetector (10) at this time and calculate 4. A Rydberg atom microwave electric field measurement method according to claim 3, characterized in that: The step S5 is specifically as follows: placing the measurement system in a microwave electric field with a frequency of ω1, and reading out the signal amplitude V of the balanced photoelectric detector (10). s , then the microwave electric field intensity is E s = k × V s .

5. A Rydberg atom microwave electric field measurement method according to claim 2, 3 or 4, characterized in that: In step S1, the narrow linewidth detection laser (01) is tuned to lock the laser frequency to the 5S of the rubidium 85 atom. 1 / 2 -5P 3 / 2 energy level, wherein 5 is the principal quantum number, S and P represent orbital angular momentum, and 1 / 2 and 3 / 2 represent total angular momentum; in the step S2, the narrow linewidth coupled laser (18) is tuned and locked to the 5P of 85 atoms. 3 / 2 -nD 5 / 2 , where n is the principal quantum number, P and D represent orbital angular momentum, and 3 / 2 and 5 / 2 represent total angular momentum.

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