An alkali metal cell temperature control method based on light-thermal deflection

Abstract

A kind of alkali metal cell temperature control method based on light thermal deflection, by the relationship between light thermal deflection angle and alkali metal cell refractive index, combined with the different alkali metal atomic number density will bring different alkali metal cell refractive index, realize the measurement and control of alkali metal cell temperature.The present application is based on optical method for temperature measurement, not by platinum resistance to alkali metal cell outside single point indirect measurement.Not only avoid the influence of monitoring point environmental noise, but also avoid the interference of low-frequency electromagnetic noise to atomic ensemble in the process of temperature measurement signal transmission.Compared with existing non-contact temperature measurement method, the precision of the present application is higher.The measured information is the information of the whole temperature field in the cell, not the temperature information of the cell surface measured by infrared temperature measurement method and other technologies.At the same time, the detection beam is far detuned, which does not destroy the polarization of atoms, ensuring real-time and accuracy.This method has great practical value for quantum precision measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of quantum precision measurement and sensing, and in particular to a kind of alkali metal cell temperature control method based on light thermal deflection, the optical method is measured the change of the optical path of detection beam through alkali metal atom cell with temperature, the thermodynamic temperature of the alkali metal cell inside the measured region can be directly obtained, so as to realize the real-time in-situ measurement and control of the temperature of alkali metal cell inside. BACKGROUND

[0002] The ultra-high sensitivity atomic spin measurement system has the characteristics of high theoretical accuracy, small volume and low cost, and is the development direction of future ultra-high sensitivity quantum precision measurement, and has wide application prospects in navigation, geological exploration and frontier scientific research. The alkali metal cell is the sensitive core of the atomic spin inertial measurement system. When preparing the alkali metal cell, alkali metal atoms and inert gas atoms are simultaneously filled into a square or circular glass cell. The temperature of the alkali metal cell directly determines the number density and average thermal motion velocity of the alkali metal gaseous atoms, and becomes one of the main factors affecting the stability and sensitivity of the atomic spin inertial measurement system. Moreover, the atomic ensemble is extremely sensitive to low-frequency magnetic field noise, so it is also necessary to ensure that the low-frequency magnetic field interference introduced during the temperature control process is as small as possible. These requirements make some conventional temperature control techniques unable to be used in the temperature control of the alkali metal cell.

[0003] The most widely used scheme for temperature control of the alkali metal cell at present is the platinum resistance temperature measurement method, which can be divided into platinum resistance four-wire direct current temperature measurement and platinum resistance alternating current bridge temperature measurement. However, these two temperature measurement methods can only measure and control the temperature of a single point on the outer wall of the alkali metal cell, and cannot reflect the real temperature of the atomic ensemble inside the cell, and also introduce low-frequency magnetic field noise. In summary, it is of great significance to realize high-precision measurement and stable control of the temperature of the atomic ensemble inside the alkali metal cell. The present application proposes a kind of cell temperature control method based on light thermal deflection, which can provide guidance and reference for the measurement and control of similar cells. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a kind of alkali metal cell temperature control method based on light thermal deflection, which can directly obtain the thermodynamic temperature of the alkali metal cell inside the measured region by measuring the change of the optical path of detection beam through alkali metal atom cell with temperature, so as to realize the real-time in-situ measurement and control of the temperature of alkali metal cell inside.

[0005] The technical solution of the present application is as follows:

[0006] The alkali metal cell temperature control method based on the light-thermal deflection, characterized in that, the pumping light beam is irradiated along the z-axis to the alkali metal cell, and the detection light beam is irradiated along the angle of θ to the x-axis through the alkali metal cell, due to the change of the relative refractive index σ2 of the atomic ensemble with the temperature, the propagation direction of the light will change, the optical path of the detection light through the atomic ensemble changes, which is shown as the different position coordinates (x, y) of the detection light beam through the alkali metal cell on the light beam position detector. The relative refractive index σ2 of the atomic ensemble can be determined by (x, y), the alkali metal atomic number density n can be determined by σ2, the internal temperature T of the alkali metal cell can be determined by n, and the heating of the alkali metal cell is controlled by T, so as to realize the control of the temperature of the alkali metal cell.

[0007]

[0008] Wherein n(T) represents the function of the alkali metal atomic number density n with respect to the internal temperature T of the alkali metal cell, n A And n B are the constants of the two different alkali metals themselves;

[0009]

[0010] Wherein c is the speed of light, n is the alkali metal atomic number density, r e is the classical radius of electron, f is the oscillator strength, D(w) is the dispersion curve, and w is the detection light frequency;

[0011] y=ltanβ+dtanα

[0012] Wherein l is the side length of the alkali metal cell, d is the distance between the alkali metal cell and the light beam position detector, α is the angle of the detection light beam incident to the alkali metal cell, and β is the refraction angle of the detection light beam incident to the alkali metal cell.

[0013]

[0014] Wherein σ2 represents the relative refractive index of the atomic ensemble, and σ1 represents the refractive index of the surrounding environment.

[0015] Since the alkali metal cell used is an axisymmetric structure, the expression of x is the same as that of y.

[0016] (x, y) is used as the sensitive signal of the internal temperature T of the alkali metal cell, and the high-precision measurement and high-precision control of the alkali metal cell temperature based on the light-thermal deflection detection are realized through PID control.

[0017] The detection light beam is a far-detuned detection light beam, so as to avoid destroying the polarization of the alkali metal atoms and ensure the real-time and accuracy of the alkali metal cell temperature detection based on the light-thermal deflection.

[0018] The detection light beam comes from a detection laser, the detection light beam emitted by the detection laser sequentially passes through a detection optical system, a magnetic shielding system, a three-dimensional active magnetic compensation coil, and an oven, and is incident on the alkali metal cell. The detection light beam emitted from the alkali metal cell deviates from the center due to a change in the optical path and is input to a position detector, which is connected to the oven through a computer and a heating circuit control system in sequence.

[0019] The pumping light beam comes from a pumping laser, and the pumping light beam emitted by the pumping laser sequentially passes through a pumping optical system, a magnetic shielding system, a three-dimensional active magnetic compensation coil, and an oven, and is incident on the alkali metal cell.

[0020] The position detector uses a CCD camera or a four-quadrant PD detector.

[0021] The method comprises the following steps:

[0022] Step S1, starting the ultra-high sensitivity atomic spin precision measurement system;

[0023] Step S2, performing magnetic field compensation to place the high-sensitivity atomic spin precision measurement system in a normal working state;

[0024] Step S3, using a detection laser to pass through the center of the alkali metal cell to be measured;

[0025] Step S4, detecting that the detection laser irradiates on a high-precision position detector after passing through the alkali metal cell;

[0026] Step S5, since the number density of the atomic ensemble in the alkali metal cell changes with temperature, the refractive index in the cell changes, and the change in the refractive index of the alkali metal cell will cause the laser beam passing through the cell to deviate from the center, and the coordinates (x, y) of the deviation of the light beam from the center are obtained through the high-precision position detector;

[0027] Step S6, obtaining the relative refractive index σ2 of the atomic ensemble through the coordinates (x, y), the side length l of the alkali metal cell, and the distance d of the high-precision position detector from the cell;

[0028] Step S7, calculating the number density n of alkali metal atoms through the relative refractive index σ2 of the atomic ensemble, and then obtaining T according to the relationship between the number density n of alkali metal atoms and the temperature T in the cell;

[0029] Step S8, taking the coordinates (x, y) of the deviation of the detection laser from the center as the sensitive signal of the temperature T in the alkali metal cell, and comparing the temperature T in the cell calculated by the computer based on the detection with a preset cell temperature, and performing closed-loop control on the temperature of the oven through a heating circuit control system, thereby realizing high-precision measurement and control of the temperature of the alkali metal cell based on light-heat deflection temperature measurement.

[0030] The technical effect of the present application is as follows: the alkali metal cell temperature control method based on light-thermal deflection of the present application realizes the measurement and control of the temperature of the alkali metal cell by the relationship between the light-thermal deflection angle and the refractive index of the alkali metal cell, and the use of different alkali metal atomic number densities to bring different alkali metal cell refractive indexes. The present application measures the temperature based on an optical method, rather than indirectly measuring a single point outside the alkali metal cell by a platinum resistance. Not only the influence of the environmental noise of the monitoring point is avoided, but also the interference of low-frequency electromagnetic noise on the atomic ensemble in the temperature measurement signal transmission process is avoided. Compared with the existing non-contact temperature measurement method, the present application has higher precision. The measured information is the overall temperature field information of the cell, rather than the temperature information of the surface of the cell measured by the infrared temperature measurement method. At the same time, the detection beam is far detuned, which does not destroy the polarization of the atoms, ensuring the real-time and accuracy. This method has great practical value for quantum precision measurement. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structure schematic diagram of an ultrahigh-sensitivity atomic spin measurement system used in the alkali metal cell temperature control method based on light-thermal deflection of the present application. Figure 1 In the alkali metal cell temperature control method based on light-thermal deflection of the present application, the pumping light emitted by the pumping laser 1 irradiates the alkali metal cell 9 along the z-axis, and the detection light emitted by the detection laser 3 forms a light-thermal deflection angle θ with the x-axis after passing through the alkali metal cell 9 along the x-axis and enters the computer 10 through the high-precision position detector, and the computer 10 controls the oven through the heating circuit control system to realize the control of the temperature of the alkali metal cell.

[0032] Figure 2 is Figure 1 In the alkali metal cell temperature control method based on light-thermal deflection of the present application, the alkali metal cell and the high-precision position detector are combined. Figure 2 In the alkali metal cell temperature control method based on light-thermal deflection of the present application, l is the side length of the alkali metal cell, d is the distance between the alkali metal cell and the position detector, α is the angle of the detection light beam entering the alkali metal cell, and β is the refraction angle of the detection light beam entering the alkali metal cell.

[0033] The reference signs are listed as follows: 1-pumping laser, 2-pumping optical system, 3-detection laser, 4-detection optical system, 5-high-precision position detector (i.e. position detector), 6-magnetic shielding system, 7-three-dimensional active magnetic compensation coil, 8-oven, 9-alkali metal cell, 10-computer, 11-heating circuit control system, θ-light-thermal deflection angle. DETAILED DESCRIPTION

[0034] The present application will be described below in conjunction with the drawings Figures 1-2 ) and examples.

[0035] Figure 1It is a structure schematic diagram of an ultrahigh sensitivity atomic spin measurement system used in an alkali metal cell temperature control method based on light thermal deflection according to the present application. Figure 2 It is Figure 1 It is a combination structure schematic diagram of an alkali metal cell and a high-precision position detector. Figures 1-2 As shown in the figure, an alkali metal cell temperature control method based on light thermal deflection includes a pumping light beam irradiating the alkali metal cell along the z-axis, and a detection light beam passing through the alkali metal cell at an angle of θ with the x-axis. Since the relative refractive index σ2 of the atomic ensemble will change with temperature, the propagation direction of the light will change, and the optical path of the detection light passing through the atomic ensemble will change, which is manifested as the different position coordinates (x, y) of the detection light beam after passing through the alkali metal cell and being presented on the light beam position detector. Through (x, y), the relative refractive index σ2 of the atomic ensemble can be determined, through σ2, the alkali metal atomic number density n can be determined, through n, the internal temperature T of the alkali metal cell can be determined, and through T, the heating of the alkali metal cell can be controlled, thereby realizing the control of the temperature of the alkali metal cell.

[0036]

[0037] Where n(T) represents the function of the alkali metal atomic number density n with respect to the internal temperature T of the alkali metal cell, n A And n B are constants of the two different alkali metals themselves;

[0038]

[0039] Where c is the speed of light, n is the alkali metal atomic number density, r e is the classical radius of the electron, f is the oscillator strength, D(w) is the dispersion curve, and w is the detection light frequency;

[0040] y = l tan β + d tan α

[0041] Where l is the side length of the alkali metal cell, d is the distance from the alkali metal cell to the light beam position detector, α is the angle of incidence of the detection light beam on the alkali metal cell, and β is the refraction angle of the detection light beam on the alkali metal cell.

[0042]

[0043] Where σ2 represents the relative refractive index of the atomic ensemble, and σ1 represents the refractive index of the surrounding environment.

[0044] Since the alkali metal cell used is an axisymmetric structure, the expression of x is the same as that of y.

[0045] The (x, y) is taken as a sensitive signal of the alkali metal cell internal temperature T, and the high-precision measurement and control of the alkali metal cell temperature based on the light-thermal deflection detection are realized through PID control (PID, Proportional Integral Derivative).

[0046] The detection light beam comes from a detection laser 3, and the detection light beam emitted by the detection laser 3 sequentially passes through a detection optical system 4, a magnetic shielding system 6, a three-dimensional active magnetic compensation coil 7, and an oven 8 to be incident on the alkali metal cell 9. The detection light beam emitted from the alkali metal cell 9 forms a light-thermal deflection angle θ with the x-axis and is input to a position detector 5. The position detector 5 is sequentially connected to the oven 8 through a computer 10 and a heating circuit control system 11. The pump light beam comes from a pump laser 1, and the pump light beam emitted by the pump laser 1 sequentially passes through a pump optical system 2, the magnetic shielding system 6, the three-dimensional active magnetic compensation coil 7, and the oven 8 to be incident on the alkali metal cell 9. The position detector 5 adopts a CCD camera or a four-quadrant PD detector.

[0047] The method comprises the following steps: step S1, starting an ultra-high-sensitivity atomic spin precision measurement system; step S2, performing magnetic field compensation to make the high-sensitivity atomic spin precision measurement system in a normal working state; step S3, using a detection laser to pass through the center of a to-be-measured alkali metal cell; step S4, detecting that the detection laser is irradiated on a high-precision position detector after passing through the alkali metal cell; step S5, because the atomic ensemble density in the alkali metal cell changes with temperature, the refractive index of the cell changes, and the change of the alkali metal cell refractive index will cause the laser beam passing through the alkali metal cell to deviate from the center, and the coordinates (x, y) of the light beam deviation from the center are obtained through the high-precision position detector; step S6, obtaining the relative refractive index σ2 of the atomic ensemble through the coordinates (x, y) and the distance d of the high-precision position detector from the cell; step S7, calculating the alkali metal atomic number density n through the relative refractive index σ2 of the atomic ensemble, and then obtaining T according to the relationship between the alkali metal atomic number density n and the alkali metal cell internal temperature T; and step S8, taking the coordinates (x, y) of the detection laser deviation from the center as a sensitive signal of the alkali metal cell internal temperature T, comparing the alkali metal cell internal temperature T obtained by the computer through detection and calculation with a preset cell temperature, and performing closed-loop control on the temperature of the oven through a heating circuit control system, so as to realize the high-precision measurement and control of the alkali metal cell temperature based on the light-thermal deflection detection.

[0048] The application discloses an alkali metal cell temperature control method based on light thermal deflection, and aims at the temperature measurement and control of an alkali metal cell.

[0049] Step S1, starting an ultra-high sensitivity atomic spin measurement system, heating the alkali metal cell 9, and making alkali metal atoms reach a polarization stable state;

[0050] Step S2, using a three-dimensional active magnetic compensation coil 7 to perform magnetic field compensation, so that the ultra-high sensitivity atomic spin inertial measurement system is in a normal working state;

[0051] The alkali metal cell 9 filled with K (potassium) and Rb (rubidium) alkali metal atoms is installed in an oven 8, the oven 8 is driven by a heating circuit control system 11, the temperature of the oven 8 can be changed by changing the setting value of the heating circuit control system 11, and then the temperature of the alkali metal cell 9 can be changed. The ultra-high sensitivity atomic spin measurement system adopts the three-dimensional magnetic compensation coil 7 to perform magnetic field compensation. The laser output by the pumping laser 1 passes through the pumping optical system 2, realizes power stabilization and frequency stabilization of the pumping light, expands the spot diameter, changes the pumping laser direction and converts the pumping light into circularly polarized light, and then the pumping light is irradiated onto the alkali metal cell 9. The magnetic shielding system 6 shields the external magnetic field, and provides an extremely weak magnetic field environment for the ultra-high sensitivity atomic spin measurement system;

[0052] Step S3, the detection laser 3 outputs detection light which passes through the detection optical system 4, realizes power stabilization and frequency stabilization of the detection light, and then passes through the alkali metal cell 9;

[0053] Step S4, a high-precision position detector 5 is arranged at a position with a distance of d from the alkali metal cell 9, and the detection laser irradiates on the high-precision position detector 5 after passing through the alkali metal cell 9;

[0054] Step S5, since the density of the atomic ensemble in the alkali metal cell 9 changes with the temperature, the relative refractive index σ2 of the atomic ensemble in the alkali metal cell 9 changes, and the change of the relative refractive index σ2 of the atomic ensemble causes the laser beam passing through the alkali metal cell 9 to deviate from the center, and the high-precision position detector 5 can obtain the coordinates (x, y) of the light beam deviation from the center;

[0055] Step S6, the refractive angle β of the detection light beam incident to the alkali metal cell is obtained through the coordinates (x, y), the side length l of the alkali metal cell and the distance d of the high-precision position detector from the alkali metal cell.

[0056] The relationship between the refractive angle β and the coordinates (x, y) is:

[0057] y = ltan beta + dtan alpha

[0058] Since the alkali metal cell used is an axisymmetric structure, the expression of x is the same as that of y

[0059] In step S7, the value of the relative refractive index sigma2 of the atomic ensemble can be obtained through the refraction angle beta, and the relationship between the refraction angle beta and the relative refractive index sigma2 of the atomic ensemble is as follows:

[0060]

[0061] Wherein, sigma2 is the relative refractive index of the atomic ensemble, and sigma1 is the refractive index of the surrounding environment.

[0062] In step S8, the alkali metal atomic number density n can be calculated through the relative refractive index sigma2 of the atomic ensemble, and the calculation formula is as follows:

[0063]

[0064] Wherein, c is the speed of light, n is the alkali metal atomic number density, r e is the classical radius of electron, f is the oscillator strength, D(w) is the dispersion curve, and w is the frequency of the detection laser.

[0065] In step S9, the temperature T of the alkali metal cell 9 is obtained according to the relationship between the alkali metal atomic number density n and the alkali metal cell temperature T.

[0066] The relationship between the alkali metal atomic number density n and the alkali metal cell temperature T is as follows:

[0067]

[0068] Wherein, n is the function of the alkali metal density n with respect to the temperature T, wherein T is the fitting obtained environment temperature felt by the gas, n A and n B are constants of different alkali metals themselves.

[0069] In step S10, the coordinates (x, y) of the detection laser deviating from the center are taken as the sensitive signal of the internal temperature of the alkali metal cell, the computer 10 compares the internal temperature of the alkali metal cell calculated by the detection with the preset cell temperature, and the temperature of the oven 8 is controlled in a closed loop through the heating circuit control system 11, so as to realize high-precision measurement and control of the temperature of the alkali metal cell 9 based on the light-heat deflection temperature measurement.

[0070] In summary, the inventors have verified the method described in the present application through experiments and theoretical verification, that is, the measurement and control of the temperature of the alkali metal cell through the light-heat deflection angle.

[0071] The content not described in detail in the specification of the present application belongs to the prior art known to the person skilled in the art. It is indicated here that the above description helps the person skilled in the art to understand the present application, but does not limit the protection scope of the present application. Any implementation of equivalent replacement, modification, improvement and / or deletion of the above description without departing from the essential content of the present application falls within the protection scope of the present application.

Claims

1. A method for alkali metal cell temperature control based on photothermal deflection, characterized by, The pumping light beam irradiates the alkali metal cell along the z-axis, and the detection light beam passes through the alkali metal cell at an angle of θ with the x-axis. Due to the change of the relative refractive index σ2 of the atomic ensemble with temperature, the propagation direction of the light changes, the optical path of the detection light passing through the atomic ensemble changes, and the position coordinates (x, y) of the detection light beam on the light beam position detector change. The relative refractive index σ2 of the atomic ensemble can be determined by (x, y), the number density n of the alkali metal atoms can be determined by σ2, the temperature T of the alkali metal cell can be determined by n, and the heating of the alkali metal cell can be controlled by T, thereby realizing the control of the temperature of the alkali metal cell.

2. The alkali metal cell temperature control method based on optical thermal deflection according to claim 1, wherein, where n(T) represents the alkali metal atomic number density n as a function of the temperature T inside the alkali metal cell, n A and n B are constants for the two different alkali metals themselves; where c is the speed of light, n is the alkali metal atomic number density, r e is the electron classical radius, f is the oscillator strength, D(w) is the dispersion curve, and w is the detection light frequency; y = l tan β + d tan α wherein l is the side length of the alkali metal cell, d is the distance between the alkali metal cell and the light beam position detector, α is the angle of incidence of the detection light beam on the alkali metal cell, and β is the refraction angle of the detection light beam on the alkali metal cell. Due to the axial symmetry of the alkali metal cell, the expression of x is the same as that of y wherein σ2 represents the relative refractive index of the atomic ensemble, and σ1 represents the refractive index of the surrounding environment.

3. The photothermal deflection based alkali vapor cell temperature control method of claim 1, wherein, The coordinates (x, y) of the detection laser deviating from the center are used as the sensitive signal of the temperature T of the alkali metal cell, and the high-precision measurement and control of the temperature of the alkali metal cell based on optical thermal deflection are realized through PID control.

4. The photothermal deflection based alkali vapor cell temperature control method of claim 1, wherein, The detection light beam is a far-detuned detection light beam to avoid destroying the polarization of the alkali metal atoms and ensure the real-time and accuracy of the detection of the temperature of the alkali metal cell based on optical thermal deflection.

5. The photothermal deflection based alkali vapor cell temperature control method of claim 1, wherein, The detection light beam comes from a detection laser, and the detection light beam emitted by the detection laser passes through a detection optical system, a magnetic shielding system, a three-dimensional active magnetic compensation coil, and an oven in sequence and then enters the alkali metal cell. The detection light beam emitted from the alkali metal cell passes through the alkali metal cell and enters a position detector. The position detector is connected to the oven through a computer and a heating circuit control system in sequence.

6. The photothermal deflection based alkali vapor cell temperature control method of claim 1, wherein, The pumping light beam comes from a pumping laser, and the pumping light beam emitted by the pumping laser passes through a pumping optical system, a magnetic shielding system, a three-dimensional active magnetic compensation coil, and an oven in sequence and then enters the alkali metal cell.

7. The photothermal deflection based alkali vapor cell temperature control method of claim 1, wherein, The position detector is a CCD camera or a four-quadrant PD detector.

8. The photothermal deflection based alkali vapor cell temperature control method of claim 1, wherein, The method comprises the following steps: Step S1, starting an ultra-high sensitivity atomic spin precision measurement system; Step S2, performing magnetic field compensation to make the high-sensitivity atomic spin precision measurement system in a normal working state; Step S3, using a detection laser to pass through the center of the alkali metal cell to be measured; Step S4, detecting the detection laser after it passes through the alkali metal cell and irradiates on a high-precision position detector; Step S5, due to the change of the number density of the atomic ensemble in the alkali metal cell with temperature, the refractive index of the alkali metal cell changes, and the change of the refractive index of the alkali metal cell causes the laser beam passing through the alkali metal cell to deviate from the center. The coordinates (x, y) of the light beam deviating from the center are obtained by the high-precision position detector. Step S6, the distance d and the distance l between the high-precision position detector and the gas chamber are used to obtain the refraction angle β of the detection light beam incident to the alkali metal gas chamber; Step S7, the value of the atomic ensemble relative refractive index σ2 is obtained through the refraction angle β, the alkali metal atomic number density n is calculated through the atomic ensemble relative refractive index σ2, and then T is obtained according to the relationship between the alkali metal atomic number density n and the alkali metal gas chamber internal temperature T; Step S8, the coordinates (x, y) of the detection laser deviating from the center are taken as the sensitive signal of the alkali metal gas chamber internal temperature T, the computer compares the alkali metal gas chamber internal temperature T obtained through detection and calculation with the preset gas chamber temperature, and the temperature of the oven is controlled in a closed loop through the heating circuit control system, so as to realize high-precision measurement and control of the alkali metal gas chamber temperature based on the light-heat deflection temperature measurement.

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