Raman laser carrier sideband ratio feedback control system and control method thereof

Abstract

The application relates to a Raman laser carrier sideband ratio feedback control system and a control method thereof. The system is used for controlling an IQ modulator of a cold atom interferometer laser system. The control system comprises an F-P resonant cavity, which is used for receiving Raman laser output by the IQ modulator, and simultaneously adjusting the cavity length of the F-P resonant cavity in real time, so as to identify and output transmitted light of different frequency components to a photoelectric detector. The photoelectric detector is used for detecting the transmitted light of different frequency components, so as to output intensity signals of different frequency components to a calculation module. The calculation module is used for collecting the intensity signals of different frequency components, and calculating and outputting the Raman laser carrier sideband ratio to a feedback control module. The feedback control module is used for performing error feedback control on the IQ modulator according to the Raman laser carrier sideband ratio and a preset carrier sideband ratio expected value, so as to realize the locking control of the Raman laser carrier sideband ratio. The application can improve the measurement accuracy and long-term stability of the cold atom interferometer laser system.

Description

Technical Field

[0001] This application relates to the field of atomic interferometry precision measurement technology, specifically to a Raman laser carrier sideband ratio feedback control system and its control method. Background Technology

[0002] Cold atom interferometry has developed rapidly in the past 20 years and has been widely used in precision measurement physics and fundamental physics research, achieving fruitful results in the measurement of inertial quantities such as gravitational acceleration, gravitational gradient, and angular velocity.

[0003] The basic working principle of cold atom interferometer for measuring inertial quantities is as follows: the temperature of the atomic cluster is cooled to the micro Kelvin level using a laser; then, the cold atomic cluster is interfered with using a π / 2-π-π / 2 Raman laser; the atomic cluster is then irradiated with a probe light to make it emit fluorescence, and the fluorescence emitted by the atomic cluster is collected and focused onto a photodetector, thereby realizing the detection of the atomic interference result; finally, the phase of the atomic interference fringes is extracted, and the inertial quantity to be measured is calculated.

[0004] Raman lasers used in cold atom interferometers are typically generated by modulating a single-frequency laser using an IQ modulator (single-sideband modulator). Because IQ modulators are highly susceptible to environmental factors such as temperature and stress, the carrier-to-sideband ratio of the Raman laser generated by an IQ modulator is easily affected by these factors, resulting in noise and long-term drift. This noise and long-term drift can directly affect the phase of the interference fringes in a cold atom interferometer, thereby impacting the measurement accuracy and long-term stability of the instrument. Summary of the Invention

[0005] Based on the above description, this application provides a Raman laser carrier sideband ratio feedback control system and its control method, which can reduce the influence of environmental factors on Raman lasers and improve the measurement accuracy and long-term stability of cold atom interferometer laser systems.

[0006] According to the first aspect, this application provides a Raman laser carrier sideband ratio feedback control system for controlling the IQ modulator of a cold atom interferometer laser system. The control system includes an FP resonant cavity, a photodetector, a calculation module, and a feedback control module.

[0007] The FP resonant cavity is used to receive the Raman laser output by the IQ modulator, and at the same time adjust the cavity length of the FP resonant cavity in real time to identify and output transmitted light of different frequency components to the photodetector.

[0008] The photodetector is used to detect the transmitted light of different frequency components, so as to output the intensity signals of different frequency components to the calculation module.

[0009] The calculation module is used to collect the intensity signals of the different frequency components, calculate the Raman laser carrier sideband ratio, and output it to the feedback control module.

[0010] The feedback control module is used to perform error feedback control on the IQ modulator based on the Raman laser carrier sideband ratio and a preset expected value of the carrier sideband ratio, so as to achieve locking control of the Raman laser carrier sideband ratio.

[0011] In one or more embodiments, the FP resonant cavity includes a body and a cavity length control unit connected to each other. The cavity length control unit is used to receive a scanning voltage signal to control the length of the body to vary linearly, so that the body transmits transmitted light of different frequency components according to the Raman laser.

[0012] In one or more embodiments, the body includes a cavity and two endoscopes, the cavity being connected between the two endoscopes, and the cavity length control unit being connected between the cavity and either of the endoscopes.

[0013] In one or more embodiments, the calculation module is used to output the scanning voltage signal to the cavity length control unit; and / or

[0014] The cavity length control unit is made of piezoelectric ceramic.

[0015] In one or more embodiments, the intensity signal of the frequency component is characterized in the form of a voltage signal; the calculation module includes:

[0016] The identification unit is used to identify the effective voltage peak value from the real-time acquired voltage signal according to a preset voltage threshold.

[0017] The classification and calculation unit is used to classify the effective voltage peak value and determine the Raman laser carrier sideband ratio based on the classification result.

[0018] In one or more embodiments, the Raman laser carrier sideband ratio is determined according to the following calculation formula, including:

[0019] p = v He / v Le

[0020] v He =(v 1H +v 2H +...+v nH ) / n

[0021] v Le =(v 1L +v 2L +...+v mL ) / m

[0022] Among them, v 1H v 2H ... v nH These represent n effective voltage peak values ​​that are greater than the average peak value; v 1L v 2L ... v mL These represent m effective voltage peaks that are less than the peak-to-average value; the peak-to-average value is the average of the peak values ​​of all effective voltage peaks; v He This represents the average of all effective voltage peak values ​​greater than the peak average, used to characterize the intensity of the Raman laser carrier; v Le denoted as the average of all effective voltage peak values ​​less than the peak average, used to characterize the intensity of the sidebands in the Raman laser; p represents the Raman laser carrier sideband ratio.

[0023] In one or more embodiments, the feedback control module includes:

[0024] An error calculation unit is used to compare the Raman laser carrier sideband ratio with a preset expected value of the carrier sideband ratio to obtain an error signal;

[0025] The PID control unit is used to calculate the error signal using the PID algorithm, obtain the bias signal, and output it to the bias voltage control terminal of the IQ modulator to control the IQ modulator to modulate the single-frequency laser, so that the intensity ratio of the carrier to the sideband in the output Raman laser is locked.

[0026] According to a second aspect, this application provides a control method for a Raman laser carrier sideband ratio feedback control system according to any of the foregoing embodiments, comprising:

[0027] The FP resonant cavity generates transmitted light of different frequency components from the input Raman laser, and the cavity length of the FP resonant cavity is adjusted in real time to identify and output transmitted light of different frequency components to the photodetector.

[0028] The photodetector detects the transmitted light of different frequency components and outputs the intensity signals of the different frequency components to the calculation module.

[0029] The intensity signals of the different frequency components are collected by the calculation module, and the Raman laser carrier sideband ratio is calculated.

[0030] The feedback control module performs error feedback control on the IQ modulator based on the Raman laser carrier sideband ratio and the preset expected value of the carrier sideband ratio, so as to achieve the locking control of the Raman laser carrier sideband ratio.

[0031] In one or more embodiments, the intensity signal of the frequency component is characterized in the form of a voltage signal; the step of acquiring the voltage signal through a calculation module and calculating the Raman laser carrier sideband ratio includes:

[0032] Based on a preset voltage threshold, the effective voltage peak value is identified from the real-time acquired voltage signal.

[0033] Calculate the peak average of all the effective voltage peaks, and take the effective voltage peaks that are greater than the peak average as the first voltage peak, and the effective voltage peaks that are less than the peak average as the second voltage peak;

[0034] Calculate the first average value of all first voltage peaks and the second average value of all second voltage peaks, and use the ratio of the first average value to the second average value as the Raman laser carrier sideband ratio.

[0035] In one or more embodiments, the step of performing error feedback control of the IQ modulator based on the Raman laser carrier sideband ratio and a preset expected carrier sideband ratio value includes:

[0036] The error signal is obtained by comparing the Raman laser carrier sideband ratio with the preset expected value of the carrier sideband ratio.

[0037] The error signal is processed using a PID algorithm to obtain a bias signal, which is then output to the bias voltage control terminal of the IQ modulator to control the IQ modulator to modulate a single-frequency laser, thereby locking the intensity ratio of the carrier to the sideband in the output Raman laser.

[0038] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0039] In the aforementioned Raman laser carrier sideband ratio feedback control system and its control method, by employing a FP resonant cavity with real-time cavity length variation for Raman laser frequency discrimination, the transmitted light of different frequency components in the Raman laser can be clearly separated. The intensity signals of different frequency components are detected by a photodetector. Then, the Raman laser carrier sideband ratio is calculated by a calculation module. Simultaneously, the feedback control module performs error feedback control of the IQ modulator based on the calculated Raman laser carrier sideband ratio and the expected value of the carrier sideband ratio, thereby achieving locked control of the Raman laser carrier sideband ratio. This effectively reduces the drift problem of the carrier sideband ratio of the Raman laser generated by the IQ modulator caused by environmental factors, and helps to improve the measurement accuracy and long-term stability of the cold atom interferometer. Attached Figure Description

[0040] Figure 1 A schematic diagram of the control principle of a Raman laser carrier sideband ratio feedback control system provided in an embodiment of this application;

[0041] Figure 2 This is a schematic diagram of a scanning voltage signal in one embodiment of this application;

[0042] Figure 3 This is a schematic diagram of the voltage signal collected in real time by the calculation module in one embodiment of this application;

[0043] Figure 4 A schematic flowchart illustrating a control method for a Raman laser carrier sideband ratio feedback control system provided in an embodiment of this application;

[0044] Figure 5 This is a flowchart illustrating step S30 of an embodiment of this application;

[0045] Figure 6 This is a flowchart illustrating step S40 of an embodiment of this application.

[0046] Explanation of reference numerals in the attached figures:

[0047] FP resonant cavity 10, body 11, cavity 111, cavity mirror 112, cavity length control unit 12;

[0048] Photodetector 20;

[0049] Solving module 30;

[0050] Feedback control module 40;

[0051] IQ modulator 100. Detailed Implementation

[0052] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0054] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. In the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if the connected circuits, units, units, etc., have the transmission of electrical signals or data between them.

[0055] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0056] See Figure 1 , Figure 1 This illustration shows a schematic diagram of a Raman laser carrier sideband ratio feedback control system according to one embodiment of this application. This Raman laser carrier sideband ratio feedback control system is used to control the IQ modulator 100 of a cold atom interferometer laser system. The control system of this embodiment includes an FP resonant cavity 10, a photodetector 20, a calculation module 30, and a feedback control module 40. The FP resonant cavity 10 receives the Raman laser output from the IQ modulator 100 and simultaneously adjusts the cavity length of the FP resonant cavity in real time to identify and output transmitted light of different frequency components to the photodetector 20. The photodetector 20 detects the transmitted light of different frequency components and outputs the intensity signals of different frequency components to the calculation module 30. The calculation module 30 collects the intensity signals of different frequency components, calculates the Raman laser carrier sideband ratio, and outputs it to the feedback control module 40. The feedback control module 40 performs error feedback control on the IQ modulator 100 based on the Raman laser carrier sideband ratio and a preset expected carrier sideband ratio value to achieve locked control of the Raman laser carrier sideband ratio.

[0057] It should be noted that the IQ modulator 100 is used to modulate a single-frequency laser to output a Raman laser. The Raman laser has two frequency components: a carrier component and a sideband component. The input of the FP resonator 10 is connected to the output of the IQ modulator 100, and the output of the FP resonator 10 is connected to the input of the photodetector 20. The photodetector 20 is electrically connected to the calculation module 30, and the calculation module 30 is electrically connected to the feedback control module 40. In this embodiment, the calculation module 30 can be a computing device, and the feedback control module 40 can be a controller. Furthermore, different cavity lengths of the FP resonator 10 result in different frequencies of the transmitted light output. Therefore, when receiving Raman laser light, the FP resonator 10 can perform frequency discrimination by adjusting its cavity length in real time, enabling the transmission of light with different frequency components.

[0058] Specifically, the IQ modulator 100 modulates a single-frequency laser to output Raman laser light, which is then transmitted to the FP resonant cavity 10. The Raman laser light reflects back and forth within the FP resonant cavity 10, outputting transmitted light with different frequency components. This transmitted light is collected by the photodetector 20. The photodetector 20 detects the transmitted light with different frequency components, outputs intensity signals of these components, and transmits them to the calculation module 30. The calculation module 30 collects the intensity signals of different frequency components and calculates the Raman laser carrier sideband ratio. The feedback control module 40 compares the Raman laser carrier sideband ratio with a preset expected value. Furthermore, the feedback control module 40 performs error feedback control on the IQ modulator 100 based on the comparison result to lock the Raman laser carrier sideband ratio at the expected value.

[0059] Compared to related technologies that measure the Raman laser carrier sideband ratio by detecting the intensity of the laser beat frequency signal, this embodiment uses a real-time variable cavity length FP resonant cavity 10 to discriminate the Raman laser frequency. This can clearly separate the transmitted light of different frequency components in the Raman laser, and the intensity signals of different frequency components are detected by a photodetector 20. Then, the Raman laser carrier sideband ratio is calculated by the calculation module 30. At the same time, the feedback control module 40 performs error feedback control on the IQ modulator 100 based on the calculated Raman laser carrier sideband ratio and the expected value of the carrier sideband ratio, so as to achieve the locking control of the Raman laser carrier sideband ratio. This can effectively reduce the drift problem of the carrier sideband ratio of the Raman laser generated by the IQ modulator 100 due to environmental factors, which helps to improve the measurement accuracy and long-term stability of the cold atom interferometer.

[0060] Continue reading Figure 1 and combined Figure 2 , Figure 2 A schematic diagram of a scanning voltage signal is shown in one embodiment of this application.

[0061] In some embodiments, the FP resonant cavity 10 includes a body 11 and a cavity length control unit 12 connected to each other. The cavity length control unit 12 is used to receive a scanning voltage signal to control the length of the body 11 to change linearly, so that the body 11 transmits transmitted light of different frequency components according to the Raman laser.

[0062] It should be noted that body 11 refers to the optical FP resonant cavity structure. Cavity length control unit 12 refers to the structural unit used to control the length of body 11. Scanning voltage signal refers to a voltage signal that increases linearly. The length of body 11 is also the cavity length of FP resonant cavity 10.

[0063] Specifically, when the body 11 receives Raman laser, the cavity length control unit 12 receives an external scanning voltage signal to control the length of the body 11 to change linearly, so that the body 11 transmits transmitted light of different frequency components according to the Raman laser. In this way, by using the FP resonant cavity 10 with linear cavity length to discriminate the Raman laser, the various frequency components of the Raman laser can be clearly separated, thereby improving the frequency discrimination accuracy.

[0064] In some embodiments, the body 11 includes a cavity 111 and two endoscopes 112, the cavity 111 being connected between the two endoscopes 112, and the cavity length control unit 12 being connected between the cavity 111 and any one of the endoscopes 112.

[0065] Specifically, in this embodiment, both cavity mirrors 112 are reflectors, with the cavity mirror 112 closer to the photodetector 20 having low transmission. A cavity length control unit 12 is connected between the cavity body 111 and either cavity mirror 112, simultaneously forming a closed cavity for the entire FP resonant cavity 10. The cavity length of the FP resonant cavity 10 refers to the length along the optical axis between the two cavity mirrors 112. Thus, by connecting the cavity length control unit 12 between the cavity body 111 and one of the cavity mirrors 112, the distance between the cavity body 111 and that cavity mirror 112 can be adjusted, thereby adjusting the distance between the two cavity mirrors 112, i.e., adjusting the cavity length of the FP resonant cavity 10, which helps to achieve the frequency discrimination function of the FP resonant cavity 10 for Raman lasers.

[0066] In some embodiments, the cavity length control unit 12 is made of piezoelectric ceramic.

[0067] Specifically, when the piezoelectric ceramic receives an external scanning voltage signal, it can modulate its own length, thereby adjusting the distance between the two cavity mirrors 112, which in turn adjusts the length of the main body 11. Thus, by using piezoelectric ceramic in the cavity length control unit 12, the cavity length of the FP resonant cavity 10 can be flexibly adjusted, which helps to achieve the frequency discrimination function of the FP resonant cavity 10 for Raman lasers.

[0068] Continue reading 1 and Figure 2 In some embodiments, the calculation module 30 is used to output a scan voltage signal to the cavity length control unit 12. In this embodiment, the calculation module 30 outputs a scan voltage signal to the piezoelectric sensor to provide the voltage required by the piezoelectric sensor. In other embodiments, the scan voltage signal can be provided to the piezoelectric sensor through other external devices to control the FP resonant cavity 10 to change linearly.

[0069] See Figure 3 , Figure 3 A schematic diagram of the voltage signal acquired in real time by the calculation module in one embodiment of this application is shown.

[0070] In some embodiments, the intensity signal of the frequency component is characterized in the form of a voltage signal; the calculation module 30 includes:

[0071] The identification unit is used to identify the periodically changing effective voltage peak from the real-time acquired voltage signal according to a preset voltage threshold; the classification and calculation unit is used to classify the effective voltage peak and determine the Raman laser carrier sideband ratio based on the classification results.

[0072] It should be noted that the voltage threshold can be set according to actual needs; in this embodiment, no restriction is imposed. The calculation module 30 can employ a combination of hardware and software computing devices. Specifically, the identification unit, based on the real-time acquired voltage signal (i.e., intensity signal), identifies voltage peaks exceeding the voltage threshold as effective peaks and identifies periodically changing effective voltage peaks. The classification and calculation unit classifies the effective voltage peaks. Based on the classification result, which reflects the relative magnitude between the intensities of two frequency components, the Raman laser carrier sideband ratio is determined. In this way, the carrier and sideband components in the Raman laser generated by the IQ modulator 100 can be accurately identified and classified. Simultaneously, by setting the voltage threshold, the influence of background noise can be removed, improving the measurement accuracy of the Raman laser carrier sideband ratio.

[0073] In some embodiments, the Raman laser carrier sideband ratio is determined according to the following calculation formula, including:

[0074] p = v He / v Le (1)

[0075] v He =(v 1H +v 2H +...+v nH ) / n (2)

[0076] v Le =(v 1L +v 2L +...+ v mL ) / m (3)

[0077] Among them, v 1H v 2H ... v nH These represent n effective voltage peak values ​​that are greater than the average peak value; v 1L v 2L ... v mL These represent m effective voltage peaks that are less than the peak-to-average value; the peak-to-average value is the average of the peak values ​​of all effective voltage peaks; v He This represents the average of all effective voltage peak values ​​greater than the peak-to-average value, used to characterize the carrier intensity in Raman lasers; v Ledenoted by , represents the average of all effective voltage peak values ​​less than the peak average, used to characterize the intensity of sidebands in Raman lasers; p represents the Raman laser carrier-sideband ratio.

[0078] Specifically, such as Figure 3 As shown, by using a preset voltage threshold v0, all effective voltage peak values ​​v are determined. e Then calculate all effective voltage peak values ​​v e The average value, also known as the peak average value, is calculated using equation (2). Furthermore, the average value v of all effective voltage peaks greater than the peak average value is calculated. He This can characterize the intensity of the carrier wave in a Raman laser. Then, according to equation (3), the average value v of all effective voltage peak values ​​less than the peak average is calculated. Le The intensity of the sidebands in the Raman laser can be characterized. Finally, the intensity ratio of the Raman laser carrier to the sidebands is calculated according to equation (1). In this way, by averaging the peak value multiple times, the influence of acquisition noise in the peak signal can be reduced, and the measurement accuracy of the Raman laser carrier-sideband ratio can be improved.

[0079] In some embodiments, the feedback control module 40 includes:

[0080] The error calculation unit compares the Raman laser carrier sideband ratio with a preset expected value to obtain an error signal. The PID control unit uses a PID algorithm to calculate the error signal, obtains a bias signal, and outputs it to the bias voltage control terminal of the IQ modulator 100 to control the IQ modulator 100 to modulate the single-frequency laser, thereby locking the intensity ratio of the carrier to the sideband in the output Raman laser.

[0081] It should be noted that the feedback control module 40 can be a PID controller. The desired carrier sideband ratio can be set according to the actual situation, and this embodiment does not impose any restrictions.

[0082] Specifically, the error calculation unit compares the currently calculated Raman laser carrier sideband ratio with the preset expected carrier sideband ratio to obtain an error signal. The PID control unit then uses a PID algorithm to perform PID calculations on the error signal, obtaining a bias signal, which is output to the bias voltage control terminal of the IQ modulator 100. This controls the IQ modulator 100 to modulate the single-frequency laser, locking the intensity ratio of the two frequency components in the output Raman laser, thus locking the Raman laser carrier sideband ratio. In this way, through error feedback control, the drift problem of the carrier sideband ratio of the Raman laser generated by the IQ modulator 100 due to environmental factors can be effectively reduced, contributing to improved measurement accuracy and long-term stability of the cold atom interferometer.

[0083] Figure 4The diagram shows a flow chart of a control method for a Raman laser carrier sideband ratio feedback control system according to an embodiment of this application.

[0084] Continue reading Figure 1 and combined Figure 4 Based on the same inventive concept, one embodiment of this application provides a control method for a Raman laser carrier sideband ratio feedback control system, comprising:

[0085] S10: The input Raman laser is transmitted through the FP resonant cavity 10 to generate transmitted light of different frequency components, and then output to the photodetector 20.

[0086] S20. The photodetector 20 detects transmitted light of different frequency components and outputs intensity signals of different frequency components to the calculation module 30.

[0087] S30. The intensity signals of different frequency components are collected by the calculation module 30, and the Raman laser carrier sideband ratio is calculated.

[0088] S40. The feedback control module 40 performs error feedback control on the IQ modulator 100 based on the Raman laser carrier sideband ratio and the preset carrier sideband ratio expectation value, so as to achieve the locking control of the Raman laser carrier sideband ratio.

[0089] Specifically, the IQ modulator 100 modulates a single-frequency laser to output Raman laser light, which is then transmitted to the FP resonant cavity 10. The Raman laser light reflects back and forth within the FP resonant cavity 10, outputting transmitted light with different frequency components. This transmitted light is collected by the photodetector 20. The photodetector 20 detects the transmitted light with different frequency components, outputs intensity signals of these components, and transmits them to the calculation module 30. The calculation module 30 collects the intensity signals of different frequency components and calculates the Raman laser carrier sideband ratio. The feedback control module 40 compares the Raman laser carrier sideband ratio with a preset expected value. Furthermore, the feedback control module 40 performs error feedback control on the IQ modulator 100 based on the comparison result to lock the Raman laser carrier sideband ratio at the expected value.

[0090] Thus, by employing the FP resonant cavity 10 with real-time variable cavity length for Raman laser frequency discrimination, the transmitted light of different frequency components in the Raman laser can be clearly separated, and the intensity signals of different frequency components can be detected by the photodetector 20. Then, the Raman laser carrier sideband ratio is calculated by the calculation module 30. At the same time, the feedback control module 40 performs error feedback control on the IQ modulator 100 based on the calculated Raman laser carrier sideband ratio and the expected value of the carrier sideband ratio, so as to achieve the locking control of the Raman laser carrier sideband ratio. This can effectively reduce the drift problem of the carrier sideband ratio of the Raman laser generated by the IQ modulator 100 due to environmental factors, and help improve the measurement accuracy and long-term stability of the cold atom interferometer.

[0091] See Figure 5 , Figure 5 A flowchart illustrating step S30 of an embodiment of this application is shown.

[0092] In some embodiments, the intensity signal of the frequency component is represented in the form of a voltage signal. Step S30, that is, acquiring the voltage signal through the calculation module 30 and calculating the Raman laser carrier sideband ratio, includes:

[0093] S31. Identify the effective voltage peak value from the real-time acquired voltage signal according to the preset voltage threshold.

[0094] S32. Calculate the peak-to-peak average of all effective voltage peaks, and take the effective voltage peaks that are greater than the peak-to-peak average as the first voltage peak, and the effective voltage peaks that are less than the peak-to-peak average as the second voltage peak.

[0095] S33. Calculate the first average value of all first voltage peaks and the second average value of all second voltage peaks, and use the ratio of the first average value to the second average value as the Raman laser carrier sideband ratio.

[0096] Specifically, based on the real-time acquired voltage signal (i.e., intensity signal), voltage peaks exceeding the voltage threshold are taken as effective peaks to obtain periodically changing effective voltage peaks. Further, the average value of all effective voltage peaks, i.e., the peak average, is calculated. Effective voltage peaks exceeding the peak average are taken as first voltage peaks, and the average value v of all first voltage peaks is calculated according to equation (2). He This can characterize the intensity of the carrier wave in a Raman laser. The effective voltage peak value less than the average peak value is taken as the second voltage peak value, and the average value v of all second voltage peak values ​​is calculated according to equation (3). LeThe intensity of the sidebands in the Raman laser can be characterized. Finally, the Raman laser carrier-sideband ratio is calculated according to equation (1). In this way, the carrier and sideband components in the Raman laser generated by the IQ modulator 100 can be accurately identified and classified. At the same time, by setting the voltage threshold, the influence of background noise can be removed, and by averaging the peak multiple times, the influence of the acquisition noise in the peak signal can be reduced, thereby improving the measurement accuracy of the Raman laser carrier-sideband ratio.

[0097] See Figure 6 , Figure 6 A flowchart illustrating step S40 of an embodiment of this application is shown.

[0098] In some embodiments, step S40, namely controlling the IQ modulator 100 based on error signal feedback to achieve locked control of the Raman laser carrier sideband ratio, includes:

[0099] S41. Compare the Raman laser carrier sideband ratio with the preset expected value of the carrier sideband ratio to obtain the error signal;

[0100] S42. The error signal is processed using the PID algorithm to obtain the bias signal and output to the bias voltage control terminal of the IQ modulator 100 to control the IQ modulator 100 to modulate the single-frequency laser, so that the intensity ratio of the carrier to the sideband in the output Raman laser is locked.

[0101] Specifically, an error signal is obtained by comparing the currently calculated Raman laser carrier sideband ratio with a preset expected carrier sideband ratio. Further, a PID algorithm is used to perform PID calculations on the error signal to obtain a bias signal, which is then output to the bias voltage control terminal of the IQ modulator 100. This controls the IQ modulator 100 to modulate the single-frequency laser, locking the intensity ratio of the two frequency components in the output Raman laser, thus locking the Raman laser carrier sideband ratio. In this way, through error feedback control, the drift problem of the carrier sideband ratio of the Raman laser generated by the IQ modulator 100 due to environmental factors can be effectively reduced, contributing to improved measurement accuracy and long-term stability of the cold atom interferometer.

[0102] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A Raman laser carrier sideband ratio feedback control system, characterized by, The application discloses an IQ modulator for controlling a laser system of a cold atom interferometer, and the control system comprises an F-P resonant cavity, a photodetector, a calculation module and a feedback control module. The F-P resonant cavity is used for receiving Raman laser output by the IQ modulator, and simultaneously adjusting the cavity length of the F-P resonant cavity in real time, so as to identify and output transmitted light of different frequency components to the photodetector. The photodetector is used for detecting the transmitted light of different frequency components, so as to output intensity signals of different frequency components to the calculation module. The calculation module is used for collecting the intensity signals of different frequency components, and calculating and outputting a carrier-to-sideband ratio of the Raman laser to the feedback control module. The feedback control module is used for performing error feedback control on the IQ modulator according to the carrier-to-sideband ratio of the Raman laser and a preset carrier-to-sideband ratio expectation value, so as to realize the lock control of the carrier-to-sideband ratio of the Raman laser. The intensity signals of different frequency components are in the form of voltage signals; and the calculation module comprises: An identification unit is used for identifying effective voltage peaks from the real-time collected voltage signals according to a preset voltage threshold value. A classification and calculation unit is used for classifying the effective voltage peaks, and determining the carrier-to-sideband ratio of the Raman laser according to the classification result. The carrier-to-sideband ratio of the Raman laser is determined according to the following calculation formula, which comprises: p = v He / v Le v He = (v 1H + v 2H +... + v nH ) / n v Le = (v 1L + v 2L +... + v mL ) / m wherein v 1H , v 2H ,..., v nH represent n effective voltage peaks greater than the peak average value; v 1L , v 2L ,..., v mL represent m effective voltage peaks less than the peak average value; the peak average value is the peak average value of all effective voltage peaks; v He represents the average value of all effective voltage peaks greater than the peak average value, used to represent the intensity of the carrier in the Raman laser; and v Le represents the average value of all effective voltage peaks less than the peak average value, used to represent the intensity of the sideband in the Raman laser; p represents the Raman laser carrier-to-sideband ratio. The feedback control module comprises: An error calculation unit is used for comparing the carrier-to-sideband ratio of the Raman laser with the preset carrier-to-sideband ratio expectation value, so as to obtain an error signal. A PID control unit is used for performing operation on the error signal by using a PID algorithm, so as to obtain a bias signal and output the bias signal to a bias voltage control end of the IQ modulator, so as to control the IQ modulator to modulate single-frequency laser, and make the intensity ratio of the carrier to the sideband in the output Raman laser locked.

2. The Raman laser carrier band edge ratio feedback control system of claim 1, wherein, The F-P resonant cavity comprises a body and a cavity length control unit connected with each other, the cavity length control unit is used for receiving a scanning voltage signal, so as to control the length of the body to change linearly, and make the body transmit transmitted light of different frequency components according to the Raman laser.

3. The Raman laser carrier band edge ratio feedback control system of claim 2, wherein, The body comprises a cavity and two cavity mirrors, the cavity is connected between the two cavity mirrors, and the cavity length control unit is connected between the cavity and any one of the cavity mirrors.

4. The Raman laser carrier band edge ratio feedback control system of claim 2, wherein, The calculation module is used for outputting the scanning voltage signal to the cavity length control unit; and / or The cavity length control unit adopts a piezoelectric ceramic.

5. A control method of the Raman laser carrier band edge ratio feedback control system according to any one of claims 1 to 4, characterized by, The application discloses an IQ modulator for controlling a laser system of a cold atom interferometer, and the control system comprises an F-P resonant cavity, a photodetector, a calculation module and a feedback control module. The F-P resonant cavity is used for receiving Raman laser output by the IQ modulator, and simultaneously adjusting the cavity length of the F-P resonant cavity in real time, so as to identify and output transmitted light of different frequency components to the photodetector. The photodetector is used for detecting the transmitted light of different frequency components, so as to output intensity signals of different frequency components to the calculation module. The calculation module is used for collecting the intensity signals of different frequency components, and calculating and outputting a carrier-to-sideband ratio of the Raman laser to the feedback control module. The feedback control module is used for performing error feedback control on the IQ modulator according to the carrier-to-sideband ratio of the Raman laser and a preset carrier-to-sideband ratio expectation value, so as to realize the lock control of the carrier-to-sideband ratio of the Raman laser.

6. The control method of a Raman laser carrier band edge ratio feedback control system according to claim 5, characterized by, The intensity signals of the different frequency components are represented in the form of voltage signals; the intensity signals of the different frequency components are collected by the solving module, and a Raman laser carrier sideband ratio is solved, comprising: According to a preset voltage threshold, an effective voltage peak value is identified from the real-time collected voltage signals; A peak average value of all the effective voltage peak values is calculated, and an effective voltage peak value greater than the peak average value is taken as a first voltage peak value, and an effective voltage peak value less than the peak average value is taken as a second voltage peak value; A first average value of all the first voltage peak values and a second average value of all the second voltage peak values are calculated, and a ratio of the first average value to the second average value is taken as the Raman laser carrier sideband ratio.

7. The control method of the Raman laser carrier band edge ratio feedback control system according to claim 6, characterized by, The Raman laser carrier sideband ratio and a preset carrier sideband ratio expected value are compared to obtain an error signal; The error signal is operated by using a PID algorithm to obtain a bias signal and output to a bias voltage control end of the IQ modulator to control the IQ modulator to modulate a single-frequency laser, so that the intensity ratio of the carrier to the sideband in the output Raman laser is locked. ​

Images