A system and method for achieving precise laser frequency stabilization

Abstract

The present invention discloses a system and method for achieving precise laser frequency stabilization. The system includes a laser, an atomic gas chamber, a photodetector, an A / D conversion module, a phase-locked amplifier, a DDS signal generator, a PID controller, and a D / A conversion module. The phase-locked amplifier performs phase-sensitive detection based on the detection signal and the sinusoidal signal generated by the DDS signal generator, and outputs two phase-sensitive detection signals to the frequency stabilization module. The frequency stabilization module adds the signal curves and searches for the zero point, obtains the voltage value of the frequency stabilization point and outputs it to the PID controller. The output signal of the PID controller is added to the sinusoidal modulation signal and output to the laser via the D / A conversion module to achieve frequency stabilization control of the laser generated by the laser. The present invention eliminates the frequency stabilization point deviation caused by the power change during the laser frequency sweep process, and solves the problem of error between the true voltage value of the laser frequency stabilization point and the found voltage value.

Description

Technical Field

[0001] The present invention relates to a system and method for achieving precise laser frequency stabilization, and belongs to the technical field of laser frequency stabilization. Background Art

[0002] Laser frequency stabilization technology stabilizes the laser frequency at a reference frequency and maintains good stability. It is indispensable in applied research fields such as atomic magnetometers and gravimeters. In atomic magnetometers, lasers are affected by factors such as temperature fluctuations, external magnetic fields, and mechanical vibration, resulting in frequency and power drift, which is detrimental to improving the sensitivity of the atomic magnetometer. Therefore, to improve the laser frequency stability and ensure the sensitivity of the atomic magnetometer, it is necessary to improve the laser frequency stabilization performance.

[0003] There are various laser frequency stabilization techniques, including saturation absorption stabilization, modulation spectrum stabilization, and dual-color laser stabilization. To miniaturize atomic magnetometers, a sawtooth-wave sweep of the laser current is often used to obtain the phase-sensitive detection zero point. However, this current sweep increases the power, causing a deviation between the phase-sensitive detection zero point and the true zero point. Therefore, eliminating this deviation during laser frequency stabilization is an urgent issue. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology, and propose a system and method for achieving precise laser frequency stabilization. By using a triangular wave signal to find the stable frequency point, the problem of deviation between the phase-sensitive detection zero point and the true zero point in traditional laser frequency stabilization technology is solved, and stable frequency control of the laser generated by the laser is achieved.

[0005] The technical solution of the present invention is:

[0006] A system for achieving precise laser frequency stabilization, comprising a laser, an atomic gas chamber, a photodetector, an A / D conversion module, a lock-in amplifier, a DDS signal generator, a PID controller, a D / A conversion module, and a frequency stabilization module;

[0007] The laser is modulated according to the input signal to generate a laser signal of corresponding frequency;

[0008] The atomic gas chamber receives the laser signal and generates a light signal with an absorption peak;

[0009] The photoelectric detector converts the light signal output by the atomic gas chamber into a voltage signal and inputs it into the A / D conversion module;

[0010] The A / D conversion module performs analog-to-digital conversion on the voltage signal and outputs the digital signal to the lock-in amplifier and PID controller;

[0011] The DDS signal generator generates a sinusoidal modulation signal and a sinusoidal reference signal with the same frequency;

[0012] The lock-in amplifier performs phase-sensitive detection after demodulation based on the received digital signal and the sinusoidal reference signal, and sequentially obtains two phase-sensitive detection signal curves, which are output to the frequency stabilization module;

[0013] The frequency stabilization module has two working states. In the initial state, a triangular wave is generated and output. After receiving two phase-sensitive detection signal curves, the module enters the second state, superimposes the two phase-sensitive detection signal curves, obtains the zero point of the superimposed curve as the true laser frequency stabilization point, and outputs the voltage value of the laser frequency stabilization point to the PID controller.

[0014] When receiving the triangular wave signal, the PID controller directly sends the triangular wave signal to the D / A conversion module; when receiving the voltage value of the laser frequency stabilization point and the current voltage value of the laser, the PID controller performs PID control to generate and output the laser frequency stabilization signal;

[0015] The D / A conversion module performs digital-to-analog conversion on the output signal of the PID controller and the sinusoidal modulation signal generated by the DDS signal generator and then sends the converted signal to the laser.

[0016] Furthermore, when the PID controller receives the voltage value of the laser frequency stabilization point and the current voltage value of the laser, it performs PID control, and the control target is that the laser voltage is equal to the laser frequency stabilization point voltage; through multiple rounds of control, the laser signal frequency output by the laser is stabilized.

[0017] Furthermore, the frequency stabilization module generates and outputs a triangular wave in an initial state. The triangular wave signal is composed of a sawtooth wave signal from low to high and a sawtooth wave signal from high to low. The absolute values ​​of the slopes of the two sawtooth wave signals are the same.

[0018] Furthermore, the system first generates and outputs a triangular wave signal by the frequency stabilization module, the PID controller directly outputs the triangular wave signal, and performs digital-to-analog conversion together with the sinusoidal modulation signal of the DDS signal generator through the D / A conversion module. Then, the triangular wave signal scans the laser, and the sinusoidal modulation signal is output to the laser. The frequency-changing laser shows an absorption peak after passing through the atomic gas chamber.

[0019] A method for achieving precise laser frequency stabilization, applied to a system for achieving precise laser frequency stabilization, comprises:

[0020] S1: After the triangle wave signal is sinusoidally modulated, it is input to the laser through D / A conversion;

[0021] S2: The laser emitted by the laser outputs a light signal with an absorption peak after passing through the atomic gas chamber. The light signal is converted into a voltage signal by the photodetector, and the voltage signal is transmitted to the lock-in amplifier module through A / D conversion;

[0022] S3: The lock-in amplifier module demodulates the received voltage signal based on the sinusoidal reference signal, and then performs phase-sensitive detection to obtain two phase-sensitive detection signal curves in sequence;

[0023] S4: superimposing the two phase-sensitive detection signal curves, and finding the zero point of the superimposed curve, wherein the zero point voltage is used as the actual laser frequency stabilization point voltage value;

[0024] S5: Input the voltage value of the laser frequency stabilization point and the current voltage value of the laser into the PID controller. The PID controller compares the voltage value of the laser frequency stabilization point and the current voltage value of the laser. If they are not equal, PID control is performed and a laser frequency stabilization signal is output. The laser frequency stabilization signal and the sinusoidal modulation signal are D / A converted and input into the laser. The laser emitted by the laser outputs a light signal with an absorption peak after passing through the atomic gas chamber. The light signal is converted into a voltage signal by a photodetector.

[0025] S6: Repeat step S5 until the laser frequency stabilization point voltage value and the laser current voltage value are equal, and the laser outputs a stable laser signal.

[0026] Furthermore, the phase-locked amplifier module demodulates the received voltage signal based on the sinusoidal reference signal, and then performs phase-sensitive detection to obtain two phase-sensitive detection signal curves in sequence. The first phase-sensitive detection signal curve is a curve obtained by performing phase-sensitive detection on the laser signal generated by scanning the laser with a sawtooth wave signal from low to high in the first half of the triangular wave signal, and the second phase-sensitive detection signal curve is a curve obtained by performing phase-sensitive detection on the laser signal generated by scanning the laser with a sawtooth wave signal from high to low in the second half of the triangular wave signal, and the atomic gas chamber, photodetector, and A / D conversion module.

[0027] Furthermore, the control target of the PID control is that the laser voltage is equal to the laser frequency stabilization point voltage.

[0028] Furthermore, the triangular wave signal is sinusoidally modulated and input into the laser through D / A conversion. The specific method is as follows: the frequency stabilization module generates a triangular wave signal, and the DDS signal generator generates a sinusoidal modulation signal; the triangular wave signal is input into the PID controller, and the PID controller directly outputs the triangular wave signal, and after adding it to the sinusoidal modulation signal, it is converted into digital-to-analog through the D / A conversion module and then input into the laser.

[0029] Furthermore, during the entire operation of the method, the DDS signal generator always generates a sinusoidal modulation signal and a sinusoidal reference signal with the same frequency for modulation and demodulation of the signal.

[0030] The advantages of the present invention compared with the prior art are:

[0031] The laser precise frequency stabilization system and method proposed in the present invention sweeps the laser through a triangular wave, obtains a new signal curve by superimposing two phase-sensitive detection curves, and searches for the zero point, thereby eliminating the frequency stabilization point deviation caused by power changes during the laser frequency sweep process, and solving the problem of error between the true voltage value of the laser frequency stabilization point and the found voltage value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0033] Figure 1 This is a schematic diagram of the structure of a system for achieving precise laser frequency stabilization according to an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of a phase-sensitive detection curve generated by a triangular wave frequency sweep according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of a new signal curve generated by superimposing two phase-sensitive detection curves according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0037] The present invention proposes a system for achieving precise laser frequency stabilization, such as Figure 1 As shown, it includes a laser, an atomic gas chamber, a photodetector, an A / D conversion module, a lock-in amplifier, a DDS signal generator, a PID control module, a D / A conversion module, and a frequency stabilization module.

[0038] The DDS signal generator generates a sinusoidal modulation signal and a sinusoidal reference signal. The sinusoidal modulation signal is added to the triangle wave signal to modulate the laser signal. The sinusoidal reference signal is input into a lock-in amplifier for demodulation by the lock-in amplifier module.

[0039] The lock-in amplifier performs phase-sensitive detection based on the detection signal and the sinusoidal signal generated by the DDS signal generator, according to the triangular wave frequency sweep, generates two phase-sensitive detection signal curves, and outputs them to the frequency stabilization module.

[0040] The frequency stabilization module adds the two phase-sensitive detection signal curves to obtain a new signal curve, uses the new signal curve to find the zero point, obtains the zero point as the true laser frequency stabilization point, and outputs the voltage value of the laser frequency stabilization point to the PID controller.

[0041] The PID controller receives the voltage value of the stable frequency point to perform laser frequency stabilization control, and outputs the laser stable frequency signal, which is added to the sinusoidal modulation signal generated by the DDS signal generator and then output to the laser through the D / A conversion module.

[0042] A method for achieving precise laser frequency stabilization, the specific steps are as follows:

[0043] (1) Generate a triangle wave signal and a sinusoidal modulation signal, convert the two signals into digital-to-analog signals, and send them to the laser;

[0044] (2) The triangle wave signal scans the laser. First, the first half of the triangle wave signal is as follows: Figure 2 The middle line segment ① shows a sawtooth wave signal from low to high, which is output to the laser with a sinusoidal modulation signal. After the laser with frequency changes passes through the atomic gas chamber, an absorption peak will appear, as shown in Figure 2 As shown in the middle line segment ②, after the absorption peak signal is converted into digital form, it is combined with the sinusoidal reference signal for phase-sensitive detection to obtain the phase-sensitive detection signal, as shown in Figure 2 As shown in the middle line segment ③, the first phase-sensitive detection curve is obtained and stored;

[0045] (3) The second half of the triangle wave signal is a sawtooth wave signal from high to low, such as Figure 2 As shown in the middle line ④, when the sinusoidal modulation signal is output to the laser, an absorption peak appears, such as Figure 2 As shown in the middle line segment ⑤, after the absorption peak signal is converted into digital form, it is combined with the sinusoidal reference signal for phase-sensitive detection to obtain a phase-sensitive detection signal, and the second phase-sensitive detection curve is obtained and stored, as shown in FIG. Figure 2 As shown by the midline segment ⑥;

[0046] (4) Add the phase-sensitive detection curves obtained in step (2) and step (3) to obtain a new phase-sensitive detection curve and find the zero point of the curve. The zero point is used as the stable frequency point to obtain the stable frequency point voltage value. The laser stable frequency point is obtained by adding the two phase-sensitive detection signal curves because the zero point voltage value found in the first half of the triangle wave is lower than the true value, such as Figure 3 As shown in the midpoints ① and ②, the zero-point voltage value found in the second half of the triangle wave is higher than the true value, such as Figure 3 As shown in the midpoints ③ and ④, the absolute value of the slope of the first half of the triangle wave is the same as that of the second half of the triangle wave, and the power of the scanning current change is also approximately the same. The two signal curves are superimposed to generate a new signal curve, such as Figure 3 As shown in the middle curve ⑤, the zero point corresponding to the phase-sensitive detection is the real zero point, that is, the stable frequency point, such as Figure 3As shown in the midpoint ⑥.

[0047] (5) The voltage value of the frequency stabilization point and the voltage value of the laser at the current moment are input into the PID controller. The controller outputs the laser frequency stabilization signal, which is added to the sinusoidal modulation signal of the DDS signal generator, and then digital-to-analog converted and output to the laser;

[0048] (6) Repeat step (5) until the laser control voltage is equal to the true frequency stabilization point voltage, at which point the laser frequency is stable.

[0049] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for achieving precise laser frequency stabilization, characterized in that: Including laser, atomic gas chamber, photodetector, A / D conversion module, lock-in amplifier, DDS signal generator, PID controller, D / A conversion module, frequency stabilization module; The laser is modulated according to the input signal to generate a laser signal of corresponding frequency; The atomic gas chamber receives the laser signal and generates a light signal with an absorption peak; The photoelectric detector converts the light signal output by the atomic gas chamber into a voltage signal and inputs it into the A / D conversion module; The A / D conversion module performs analog-to-digital conversion on the voltage signal and outputs the digital signal to the lock-in amplifier and PID controller; The DDS signal generator generates a sinusoidal modulation signal and a sinusoidal reference signal with the same frequency; The lock-in amplifier performs phase-sensitive detection after demodulation based on the received digital signal and the sinusoidal reference signal, and sequentially obtains two phase-sensitive detection signal curves, which are output to the frequency stabilization module; The frequency stabilization module has two working states. In the initial state, a triangular wave is generated and output. After receiving two phase-sensitive detection signal curves, the module enters the second state, superimposes the two phase-sensitive detection signal curves, obtains the zero point of the superimposed curve as the true laser frequency stabilization point, and outputs the voltage value of the laser frequency stabilization point to the PID controller. When receiving the triangular wave signal, the PID controller directly sends the triangular wave signal to the D / A conversion module; when receiving the voltage value of the laser frequency stabilization point and the current voltage value of the laser, the PID controller performs PID control to generate and output the laser frequency stabilization signal; The D / A conversion module performs digital-to-analog conversion on the output signal of the PID controller and the sinusoidal modulation signal generated by the DDS signal generator and then sends the converted signal to the laser.

2. A system for achieving precise laser frequency stabilization according to claim 1, characterized in that: When the PID controller receives the voltage value of the laser frequency stabilization point and the current voltage value of the laser, it performs PID control, and the control target is to make the laser voltage equal to the voltage of the laser frequency stabilization point; through multiple rounds of control, the frequency of the laser signal output by the laser is stabilized.

3. The system for achieving precise laser frequency stabilization according to claim 1, characterized in that: The frequency stabilization module generates and outputs a triangular wave in the initial state. The triangular wave signal consists of a sawtooth wave signal from low to high and a sawtooth wave signal from high to low. The absolute values ​​of the slopes of the two sawtooth wave signals are the same.

4. The system for achieving precise laser frequency stabilization according to claim 3, characterized in that: The system first generates and outputs a triangular wave signal by the frequency stabilization module. The PID controller directly outputs the triangular wave signal, and together with the sinusoidal modulation signal of the DDS signal generator, it undergoes digital-to-analog conversion through the D / A conversion module. Then, the triangular wave signal scans the laser, and the sinusoidal modulation signal is output to the laser. The frequency-changing laser exhibits an absorption peak after passing through the atomic gas chamber.

5. A method for achieving precise laser frequency stabilization, applied to the system for achieving precise laser frequency stabilization according to claim 1, characterized in that: include: S1: After the triangle wave signal is sinusoidally modulated, it is input to the laser through D / A conversion; S2: The laser emitted by the laser outputs a light signal with an absorption peak after passing through the atomic gas chamber. The light signal is converted into a voltage signal by the photodetector, and the voltage signal is transmitted to the lock-in amplifier module through A / D conversion; S3: The lock-in amplifier module demodulates the received voltage signal based on the sinusoidal reference signal, and then performs phase-sensitive detection to obtain two phase-sensitive detection signal curves in sequence; S4: superimposing the two phase-sensitive detection signal curves, and finding the zero point of the superimposed curve, wherein the zero point voltage is used as the actual laser frequency stabilization point voltage value; S5: Input the voltage value of the laser frequency stabilization point and the current voltage value of the laser into the PID controller. The PID controller compares the voltage value of the laser frequency stabilization point and the current voltage value of the laser. If they are not equal, PID control is performed and a laser frequency stabilization signal is output. The laser frequency stabilization signal and the sinusoidal modulation signal are D / A converted and input into the laser. The laser emitted by the laser outputs a light signal with an absorption peak after passing through the atomic gas chamber. The light signal is converted into a voltage signal by a photodetector. S6: Repeat step S5 until the laser frequency stabilization point voltage value and the laser current voltage value are equal, and the laser outputs a stable laser signal.

6. A method for achieving precise laser frequency stabilization according to claim 5, characterized in that: The phase-sensitive detection amplifier module demodulates the received voltage signal based on the sinusoidal reference signal, and then performs phase-sensitive detection to obtain two phase-sensitive detection signal curves in sequence. The first phase-sensitive detection signal curve is a curve obtained by performing phase-sensitive detection on the laser signal generated by scanning the laser with a sawtooth wave signal from low to high in the first half of the triangular wave signal. The second phase-sensitive detection signal curve is a curve obtained by performing phase-sensitive detection on the laser signal generated by scanning the laser with a sawtooth wave signal from high to low in the second half of the triangular wave signal.

7. The method for achieving precise laser frequency stabilization according to claim 5, characterized in that: The control target of PID control is to make the laser voltage equal to the laser frequency stabilization point voltage.

8. The method for achieving precise laser frequency stabilization according to claim 5, characterized in that: After the triangular wave signal is sinusoidally modulated, it is input into the laser through D / A conversion. The specific method is as follows: the frequency stabilization module generates a triangular wave signal, and the DDS signal generator generates a sinusoidal modulation signal; the triangular wave signal is input into the PID controller, and the PID controller directly outputs the triangular wave signal, and after adding it to the sinusoidal modulation signal, it is converted into digital-to-analog through the D / A conversion module and then input into the laser.

9. The method for achieving precise laser frequency stabilization according to claim 5, characterized in that: During the entire operation of the method, the DDS signal generator continuously generates a sinusoidal modulation signal and a sinusoidal reference signal with the same frequency for modulation and demodulation of the signal.

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