CN113572022B - Laser frequency stabilization system based on improved double-path digital phase-locked amplifier - Google Patents
Laser frequency stabilization system based on improved double-path digital phase-locked amplifier Download PDFInfo
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Abstract
The invention belongs to the technical field of laser frequency stabilization, and particularly discloses a laser frequency stabilization system based on an improved double-path digital phase-locked amplifier. The method gets rid of the limitation that the frequency stabilization of the laser depends on manual phase adjustment, and improves the intelligent degree of the frequency stabilization system. Meanwhile, due to the existence of a negative feedback loop in the phase-locked amplifier, the problem of error signal jitter caused by phase jitter in the working process of the system can be reduced, and the quality of an error signal is improved.
Description
Technical Field
The invention belongs to the technical field of laser frequency stabilization, and particularly relates to a laser frequency stabilization system based on an improved double-path digital phase-locked amplifier. Laser frequency stabilization is achieved using an improved two-way digital lock-in amplifier.
Background
The laser has the characteristics of good monochromaticity and strong coherence, and has wide application in the fields of precision metering, gravitational wave detection, information science and the like. However, the frequency stability of the conventional free-running laser is poor, and after a passive frequency stabilization (temperature control, constant current source drive and the like) design is adopted, the frequency drift still cannot meet the requirement of modern precision measurement on the laser frequency stability, so that certain measures must be taken to actively improve the laser frequency stability in order to improve the long-term precision of the laser frequency.
The existing laser frequency stabilization methods are various, and some of the existing laser frequency stabilization methods need to generate an error signal by means of modulating the laser frequency (with an internal modulation or an external modulation), and then achieve the purpose of laser frequency stabilization by using a method of extracting the error signal from noise by using a phase-locked amplifier. However, in the current method for extracting the error signal, a single-path lock-in amplifier is generally used to extract the error signal, and the phase is adjusted while the magnitude of the error signal is observed until the peak value of the error signal is observed to be the maximum by naked eyes, so as to determine the phase optimum point. The manual phase adjustment has certain subjectivity and no real-time property, and the problem of amplitude jitter of an error signal caused by phase jitter in the frequency stabilization process cannot be solved. In addition, although the traditional dual-output digital correlation demodulator can acquire the amplitude and the phase of a signal, the output amplitude is always a positive value and has no directivity, and the traditional dual-output digital correlation demodulator cannot be directly used for laser frequency stabilization.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a laser frequency stabilization system based on an improved double-path digital phase-locked amplifier, which can directly extract the magnitude of an error signal and simultaneously directly output a phase quantity by improving the double-path digital phase-locked amplifier, and adjust a reference signal in real time by utilizing the phase quantity to enable the error signal to be always in a theoretical value, thereby improving the signal-to-noise ratio of the error signal and achieving the aim of improving the frequency stabilization precision.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme.
A laser frequency stabilization system based on an improved two-way digital phase-locked amplifier comprises: the device comprises a laser, a saturated absorption spectrum generation optical path unit, a photoelectric detector, a trans-impedance amplifier, an ADC (analog to digital converter), an improved two-way digital phase-locked amplifier, a first frequency synthesizer, a digital adder, a triangular wave generator, a DAC (digital to analog converter) and an addition circuit;
the laser emits laser, and the laser generates a saturated absorption spectrum optical signal through a saturated absorption spectrum generation optical path unit; the photoelectric detector receives a saturated absorption spectrum optical signal and converts the saturated absorption spectrum optical signal into a saturated spectrum current signal, the saturated spectrum current signal is converted into a voltage signal which can be collected by the ADC through the trans-impedance amplifier, and the voltage signal is converted into a saturated spectrum digital signal through the ADC and then enters the improved two-way digital phase-locked amplifier;
the improved double-path digital phase-locked amplifier extracts an error signal and phase information in a saturation spectrum digital signal and outputs the error signal to a digital PID circuit to obtain a feedback control voltage digital signal; meanwhile, negative feedback is formed by the phase information in the improved two-way digital phase-locked amplifier, and the phase difference is dynamically adjusted to be 0 degree all the time;
when an initial frequency stabilizing point is determined, the frequency scanning range of the laser is narrowed until only an error signal of a target spectrum peak can be observed, at the moment, three input ends of the digital adder are respectively input into the first frequency synthesizer to generate a modulation signal, a frequency sweeping signal generated by the triangular wave generator and an error signal output by the improved two-way digital phase-locked amplifier, and then the initial frequency stabilizing point voltage is determined by combining a bias point of laser frequency and is transmitted to the adding circuit;
the feedback control voltage digital signal is converted into an analog voltage signal through a DAC and then is sent to an addition circuit, and the addition circuit outputs a frequency stabilization voltage signal according to the received initial frequency stabilization point voltage and the feedback control voltage; and realizing the frequency stabilization of the laser by using the frequency stabilization voltage signal.
Further, the improved two-way digital phase-locked amplifier comprises a second frequency synthesizer, a third frequency synthesizer, two low-pass filters and two digital multipliers; the second frequency synthesizer generates a reference sine demodulation signal, the signal is multiplied by an input saturation spectrum digital signal through a digital multiplier and then filtered through a low-pass filter, and an error signal, namely an I-path signal, is extracted;
the third frequency synthesizer generates a reference cosine demodulation signal, and the signal is multiplied by an input saturated spectrum digital signal through another digital multiplier and then filtered through another low-pass filter to obtain a Q-path signal;
and calculating phase information according to the I path signal and the Q path signal, feeding the phase information back to phase input ports of the second frequency synthesizer and the third frequency synthesizer, and dynamically adjusting the phase to 0 degree to maximize an output error signal.
And further, the device also comprises a PC, the error signal and the phase are transmitted to the PC through a serial port, and the data are displayed in the PC in real time.
Further, the digital signal processing process is realized in an FPGA, namely, the improved two-way digital phase-locked amplifier, the digital PID circuit, the first frequency synthesizer, the second frequency synthesizer, the third frequency synthesizer and the triangular wave generator are realized through the FPGA.
Further, the laser driving circuit comprises a voltage-current converter which is used for generating the driving current of the laser according to the frequency stabilization voltage signal.
Furthermore, a Faraday isolator is arranged between the laser and the saturated absorption spectrum generation light path unit, and the laser is connected with a temperature control module.
Further, the saturated absorption spectrum generation optical path unit comprises a first beam splitter, a half-wave plate, a polarization beam splitter, a reflector pair, a second beam splitter and a cesium bulb, wherein laser is divided into frequency stabilization light and experimental light through the first beam splitter, the frequency stabilization light is divided into strong pumping light and weak light through the half-wave plate and the polarization beam splitter in sequence, and the strong pumping light is opposite to the detection light at the cesium bulb after the direction of the strong pumping light is adjusted through the first reflector pair to generate a saturated absorption spectrum signal; the weak light is split into reference light and detection light by the second beam splitter and received by the photodetector.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention improves the two-way digital phase-locked amplifier, so that the two-way digital phase-locked amplifier can simultaneously acquire an error signal and a phase, a feedback loop can be formed in the phase-locked loop according to the phase, and the phase difference of the two is dynamically adjusted to be 0 degree all the time. The limitation of manual adjustment is eliminated, and the intelligent degree of the frequency stabilization system is improved. Meanwhile, due to the existence of a negative feedback loop in the phase-locked amplifier, the problem of error signal jitter caused by phase jitter in the working process of a system can be reduced, and the stability of the error signal is improved.
(2) The phase difference extracted by the improved two-way digital phase-locked amplifier can form a feedback loop inside, and can be transmitted to a PC through a serial port function and displayed in real time through the PC. Compared with a method for observing the amplitude of the error signal, the method is more intuitive, and even if an internal feedback loop of the phase-locked amplifier is closed, the phase can still be more intuitively adjusted manually.
(3) When the system is used for frequency stabilization, when an external signal is used for modulating a laser, an additional phase-locked loop circuit is not needed to be used for synchronizing the phases of a reference signal and a modulation signal, so that the flexibility of the frequency stabilization system is improved while the circuit design is simplified.
Drawings
The invention is described in further detail below with reference to the figures and specific embodiments.
FIG. 1 is a schematic diagram of the system of the present invention;
fig. 2 is an optical path configuration diagram of a saturated absorption spectrum generation optical path unit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an improved two-way digital lock-in amplifier according to an embodiment of the present invention;
in the above figures, 1 laser; 2, a saturated absorption spectrum generation optical path unit; 21 a first beam splitter; 22 half-wave plates; 23 a polarizing beam splitter; 24 mirror pairs; 25 a second beam splitter; 26 cesium bubbles; 3, a photoelectric detector; 4, a transimpedance amplifier; 5 ADC; 6 improved two-way digital phase-locked amplifier; 61 a second frequency synthesizer; 62 a third frequency synthesizer; 63 a low-pass filter; a 64-digit multiplier; 7 a first frequency synthesizer; an 8 digital adder; 9 a triangular wave generator; 10 DAC; 11 an addition circuit; a 12 Faraday isolator; 13 a pressure-to-flow converter; 14 temperature control module.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention.
Referring to fig. 1, the present invention provides a laser frequency stabilization system based on an improved two-way digital lock-in amplifier 6, which includes: the device comprises a laser 1, a saturated absorption spectrum generation optical path unit 2, a photoelectric detector 3, a trans-impedance amplifier 4, an ADC5, a modified two-way digital phase-locked amplifier 6, a first frequency synthesizer 7, a digital adder 8, a triangular wave generator 9, a DAC10 and an adding circuit 11;
the laser 1 emits laser, and the laser generates a saturated absorption spectrum optical signal through the saturated absorption spectrum generation optical path unit 2; the photoelectric detector 3 receives the saturated absorption spectrum optical signal and converts the saturated absorption spectrum optical signal into a saturated spectrum current signal, the saturated spectrum current signal is converted into a voltage signal which can be collected by the ADC5 through the trans-impedance amplifier 4, and the voltage signal is converted into a saturated spectrum digital signal through the ADC5 and then enters the improved two-way digital phase-locked amplifier 6;
the improved double-path digital phase-locked amplifier 6 extracts an error signal and phase information in the saturation spectrum digital signal and outputs the error signal to a digital PID circuit to obtain a feedback control voltage digital signal; meanwhile, negative feedback is formed by the phase information in the improved two-way digital phase-locked amplifier 6, and the phase difference is dynamically adjusted to be 0 degree all the time;
when an initial frequency stabilizing point is determined, the frequency scanning range of the laser 1 is narrowed until only an error signal of a target spectrum peak can be observed, at this time, three input ends of the digital adder 8 are respectively input into the first frequency synthesizer 7 to generate a modulation signal, a frequency sweeping signal generated by the triangular wave generator 9 and an error signal output by the improved two-way digital phase-locked amplifier 6, and then an initial frequency stabilizing point voltage is determined by combining a bias point of laser frequency and is transmitted to the adding circuit 11;
the feedback control voltage digital signal is converted into an analog voltage signal through a DAC10 and then is sent to an addition circuit 11, and the addition circuit 11 outputs a frequency stabilization voltage signal according to the received initial frequency stabilization point voltage and the feedback control voltage; the frequency stabilization of the laser 1 is realized by the frequency stabilization voltage signal.
The system comprises a DFB laser 1 (distributed feedback laser 1), a Faraday isolator 12, a saturated absorption spectrum generation optical path unit 2, a balanced photoelectric detector 3, a transimpedance amplifier 4, an ADC5 circuit, a DAC10 circuit, a temperature control module 14, a pressure-current converter 13, an FPGA chip, an improved two-way digital phase-locked amplifier 6 realized by FPGA, a digital PID, a first frequency synthesizer 7, a second frequency synthesizer 61, a third frequency synthesizer 62(DDS) and the like. The saturated absorption spectrum generation optical path unit 2 comprises a Beam Splitter (BS), a half-wave plate 22, a polarization beam splitter 23(PBS), a mirror pair 24, and a cesium bulb 26.
The DFB laser 1 is driven by a pressure-flow converter 13, an external temperature control module 14 is used for setting temperature, laser sequentially passes through a Faraday isolator 12 and a saturated absorption spectrum generation light path unit 2 to irradiate the input end of a photoelectric detector 3, the output end of the photoelectric detector 3 is connected with the input port of an ADC5 (digital-to-analog conversion chip) through a transimpedance amplifier 4, the output of the ADC5 is connected with an FPGA (field programmable gate array), the FPGA outputs digital signals to control the output of a DAC10 (digital-to-analog conversion chip), the output of the DAC10 is connected with an adding circuit 11 and a direct current bias point, the adding circuit is added with a pressure-flow conversion input end, and the output of the pressure-flow conversion circuit drives the DFB laser 1 to output laser, so that a frequency stabilizing loop is formed.
Referring to fig. 2, the optical path structure of the saturated absorption spectrum generating optical path unit 2 of the present invention will be described in further detail.
The saturated absorption spectrum generation optical path unit 2 comprises a first beam splitter 21, a half-wave plate 22, a polarization beam splitter 23, a reflector pair 24, a second beam splitter 25 and a cesium bulb 26, wherein laser is divided into frequency stabilization light and experimental light through the first beam splitter 21, the frequency stabilization light is divided into strong pumping light and weak light through the half-wave plate 22 and the polarization beam splitter 23 in sequence, and the strong pumping light is opposite to detection light at the cesium bulb 26 after the direction of the strong pumping light is adjusted through the first reflector pair 24 to generate a saturated absorption spectrum signal; the weak light is split into reference light and detection light by the second beam splitter 25 and received by the photodetector 3.
Specifically, the laser light S is split by one BS (splitting ratio 9:1) into experimental light and laser light participating in frequency stabilization. The polarization of the frequency-stabilized light is adjusted through a half-wave plate 22, so that the laser light passing through a polarization beam splitter 23PBS is divided into pump light and weak light, the irradiation direction of the pump light is adjusted through a graphic reflector and the PBS, and finally the pump light and the detection light are emitted in a cesium bubble 26 in an opposite mode to generate a saturated absorption spectrum signal. The weak light is split into reference light and detection light by the second beam splitter 25 (splitting ratio 50:50) and received by the balanced detector. Adjusting the driving current of the laser 1 to be close to an absorption peak, turning on a sweep frequency switch of the laser 1, saturating cesium atoms with pumping light, and generating saturated absorption spectrum signals due to the lamb effect when the detection light passes through the saturated cesium atoms.
The improved two-way digital lock-in amplifier 6 of the present invention is described in further detail with reference to fig. 3.
The improved two-way digital lock-in amplifier 6 comprises a second frequency synthesizer 61, a third frequency synthesizer 62, two low-pass filters 63 and two digital multipliers 64; wherein, the second frequency synthesizer 61 generates a reference sine demodulation signal, the signal is multiplied by an input saturation spectrum digital signal through a digital multiplier 64 and then filtered 63 through a low-pass filter, and an error signal, namely an I-path signal, is extracted;
the third frequency synthesizer 62 generates a reference cosine demodulation signal, and the signal is multiplied by an input saturated spectrum digital signal through another digital multiplier 64 and then filtered 63 through another low-pass filter to obtain a Q-path signal;
and calculating phase information according to the I path signal and the Q path signal, feeding the phase information back to phase input ports of the second frequency synthesizer 61 and the third frequency synthesizer 62, and dynamically adjusting the phase to 0 degrees to maximize an output error signal.
Specifically, let the laser modulation frequency be f0Sampling frequency of fsLet fs＝N*f0(N>2), the signal collected by the ADC5 is expressed as
Where N (k) is gaussian noise, k represents a sampling point, N is the number of sampling points in a signal period, a (k) is signal amplitude, and θ (k) is phase information.
A sinusoidal demodulation signal output from a second frequency synthesizer 61(DDS)
Multiplied by s (k) by a digital multiplier 64, using a sum and difference equation
The product of the two obtained according to the above expression has a difference frequency term
And the frequency multiplication term
The frequency multiplication term is filtered after passing through a low-pass filter 63, and only the difference frequency term output is left
Because of the fact that
Is a fixed digital value, which may be 1, where i (k) is e (k), e (k) represents the error signal, and θ (k) is the phase difference between the reference signal and the input signal.
On the other hand, when s (k) and
after multiplication, the product is passed through a low-pass filter 63, and the result is obtained by the same method
The input ports of the cordic IP core for sending I (k) and Q (k) into the FPGA can be obtained
Finally, θ (k) is fed back to the phase input ports of the second frequency synthesizer 61 and the third frequency synthesizer 62 inside the FPGA, and the phase θ (k) is dynamically adjusted to 0 ° (the characteristic of dynamically adjusting the phase difference between the input signal and the reference signal is an essential characteristic of improving the phase-locked amplifier from other phase-locked amplifiers, and this characteristic is particularly suitable for stabilizing the laser frequency), and then the output error signal e (k) is the maximum, and its value is a (k). In addition, the phase differences theta (k) and e (k) can be sent to a host end through a serial port, and data can be displayed in real time in a PC.
In the present invention, the first frequency synthesizer 7, the second frequency synthesizer 61, and the third frequency synthesizer 62 generate three sine signals having the same frequency and different phases, and the second frequency synthesizer 61 and the third frequency synthesizer 62 have a phase difference of 90 ° (generate sine and cosine signals, respectively).
The invention provides a novel digital phase-locked amplifier which is more intelligent and more suitable for laser frequency stabilization.
The following describes the specific implementation steps of the system in detail by taking saturation spectrum frequency stabilization as an example:
the laser 1 is driven, a light path is built by laser according to a path shown in fig. 2, the pump light and the detection light are overlapped at the cesium bubble 26 as much as possible, and meanwhile, the light intensities of the reference light and the detection light are adjusted to be the same as much as possible when the reference light and the detection light reach the balance photoelectric detector 3.
The pump light and the detection light with the same light intensity irradiate the balance photoelectric detector 3, at the moment, the frequency sweeping button of the laser 1 is turned on, and meanwhile, the driving current is slowly adjusted until 6 spectral peaks can be clearly seen on the oscilloscope.
The cesium atomic absorption power can be expressed as follows: pT(w)＝P0exp[-α(w)x]
Wherein, P0Is the incident light intensity, alpha (w) is the absorption coefficient, w is the laser frequency, and x is the length of the cesium atomic region through which the laser passes.
When the absorption is very small (. alpha. (w) x)<<1) P is obtained by Taylor's formulaT(w) an approximate formula PT(w)≈P0[1-α(w)x]. Further processing to obtain cesium atom absorption power DeltaP (w) ═ P0-PT(w)＝P0α(w)x。
The modulated absorption power Δ P to which Δ w (t) is added to the output frequency of the laser 1 at this time is represented as follows:
△P(w+△w(t))＝P0α(w+△w(t))x
and because the modulation amplitude Δ w (t) is small, much smaller than the laser frequency w, the above expression can be further developed by taylor's formula,
the expansion is as follows:
let Δ w (t) asin (wt), the expression of Δ P (w + Δw (t)) of the absorbed power at this time is as follows:
since the absorption coefficient α (w) of the cesium atom is of the lorentz type and has even symmetry, the odd-order differential has the characteristics of the same magnitude and the opposite direction on both sides of the transition point, and this characteristic can be used to stabilize the output frequency of the laser 1.
The invention takes the first-order differential method for frequency stabilization as an example, and at the moment, the main useful signal s (t) P generated by the saturation spectrum0xA α' (w) sin (wt), the remainder being represented by noise s (t). Converting the signal s (t) into a voltage signal, converting the voltage signal into a digital quantity through an ADC5, extracting an error signal e (k) and a phase difference theta (k) by utilizing the characteristic of extracting a weak signal of a phase-locked amplifier, outputting the error signal e (k) according to a flow chart of figure 3, sending the phase signal to a DDS phase adjusting port in the phase-locked loop to adjust the phase of a demodulation signal, and sending the e (k) and the theta (k) to a PC (personal computer) through a serial port to be displayed.
And (3) reducing the frequency scanning range of the laser 1 until the PC can only observe an error signal of a target spectrum peak, recording the digital quantity corresponding to the maximum value and the minimum value of the error signal, and summing the digital quantity and the minimum value to average the digital quantity and the digital quantity to be used as an initial point of the laser frequency.
And the error signal output by the improved double-path phase-locked amplifier is sent to a digital PID circuit to obtain the feedback control quantity.
The feedback control quantity and the modulation quantity are added by a digital adder 8 in the FPGA, and then the voltage quantity is output to an input port of the adding circuit 11 by a DAC10, the laser frequency initial point voltage is converted into a voltage quantity by another DAC10 chip and is output to the other input port of the adding circuit 11, and the output of the adding circuit 11 is the voltage quantity for frequency stabilization.
Step 7, converting into a frequency stabilizing current for driving the laser 1:
the frequency-stabilized voltage signal is sent to the input end of the voltage-current converter 13, and a driving current capable of stabilizing the frequency of the laser 1 is obtained through a 15-ohm conversion resistor.
The invention improves the two-way digital phase-locked amplifier, so that the two-way digital phase-locked amplifier can simultaneously acquire an error signal and a phase, a feedback loop can be formed in the phase-locked loop according to the phase, and the phase difference of the two is dynamically adjusted to be 0 degree all the time. The limitation of manual adjustment is eliminated, and the intelligent degree of the frequency stabilization system is improved. Meanwhile, the problem of error signal jitter caused by phase jitter in the working process of the system can be reduced due to the existence of a negative feedback loop in the phase-locked amplifier, and the stability of the error signal is improved.
Although the present invention has been described in detail in this specification with reference to specific embodiments and illustrative embodiments, it will be apparent to those skilled in the art that modifications and improvements can be made thereto based on the present invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (8)
1. Laser frequency stabilization system based on improved two-way digital lock-in amplifier, characterized in that includes: the device comprises a laser, a saturated absorption spectrum generation optical path unit, a photoelectric detector, a trans-impedance amplifier, an ADC (analog to digital converter), an improved two-way digital phase-locked amplifier, a first frequency synthesizer, a digital adder, a triangular wave generator, a DAC (digital to analog converter) and an addition circuit;
the laser emits laser, and the laser generates a saturated absorption spectrum optical signal through a saturated absorption spectrum generation optical path unit; the photoelectric detector receives a saturated absorption spectrum optical signal and converts the saturated absorption spectrum optical signal into a saturated spectrum current signal, the saturated spectrum current signal is converted into a voltage signal which can be collected by the ADC through the trans-impedance amplifier, and the voltage signal is converted into a saturated spectrum digital signal through the ADC and then enters the improved two-way digital phase-locked amplifier;
the improved double-path digital phase-locked amplifier extracts an error signal and phase information in a saturation spectrum digital signal and outputs the error signal to a digital PID circuit to obtain a feedback control voltage digital signal; meanwhile, negative feedback is formed by the phase information in the improved two-way digital phase-locked amplifier, and the phase difference is dynamically adjusted to be 0 degree all the time;
when an initial frequency stabilizing point is determined, the frequency scanning range of the laser is narrowed until only an error signal of a target spectrum peak can be observed, at the moment, three input ends of the digital adder are respectively input into the first frequency synthesizer to generate a modulation signal, a frequency sweeping signal generated by the triangular wave generator and an error signal output by the improved two-way digital phase-locked amplifier, and then the initial frequency stabilizing point voltage is determined by combining a bias point of laser frequency and is transmitted to the adding circuit;
the feedback control voltage digital signal is converted into an analog voltage signal through a DAC and then is sent to an addition circuit, and the addition circuit outputs a frequency stabilization voltage signal according to the received initial frequency stabilization point voltage and the feedback control voltage; and realizing the frequency stabilization of the laser by using the frequency stabilization voltage signal.
2. The improved two-way digital lock-in amplifier based laser frequency stabilization system according to claim 1, wherein the improved two-way digital lock-in amplifier comprises a second frequency synthesizer, a third frequency synthesizer, two low pass filters and two digital multipliers; the second frequency synthesizer generates a reference sine demodulation signal, the signal is multiplied by an input saturation spectrum digital signal through a digital multiplier and then filtered through a low-pass filter, and an error signal, namely an I-path signal, is extracted;
the third frequency synthesizer generates a reference cosine demodulation signal, and the signal is multiplied by an input saturated spectrum digital signal through another digital multiplier and then filtered through another low-pass filter to obtain a Q-path signal;
and calculating phase information according to the I path signal and the Q path signal, feeding the phase information back to phase input ports of the second frequency synthesizer and the third frequency synthesizer, and dynamically adjusting the phase to 0 degree to maximize an output error signal.
3. The improved two-way digital lock-in amplifier based laser frequency stabilization system according to claim 1, further comprising a PC, wherein the error signal and the phase are transmitted to the PC through a serial port, and data are displayed in the PC in real time.
4. The laser frequency stabilization system based on the improved two-way digital phase-locked amplifier according to claim 2, wherein the digital signal processing process of the system is realized in an FPGA, that is, the improved two-way digital phase-locked amplifier, the digital PID circuit, the first frequency synthesizer, the second frequency synthesizer, the third frequency synthesizer and the triangular wave generator are realized by the FPGA.
5. The improved two-way digital lock-in amplifier based laser frequency stabilization system of claim 1, further comprising a voltage-to-current converter for generating a laser drive current according to the frequency stabilization voltage signal.
6. The laser frequency stabilization system based on the improved two-way digital lock-in amplifier is characterized in that the saturated absorption spectrum generation optical path unit comprises a first beam splitter, a half-wave plate, a polarization beam splitter, a reflector pair, a second beam splitter and a cesium bulb, wherein laser light is divided into frequency stabilization light and experimental light through the first beam splitter, the frequency stabilization light is divided into strong pump light and weak light through the half-wave plate and the polarization beam splitter in sequence, and the strong pump light is opposite to probe light at the cesium bulb after the direction of the strong pump light is adjusted through the reflector pair to generate a saturated absorption spectrum signal; the weak light is split into reference light and detection light by the second beam splitter and received by the photodetector.
7. The laser frequency stabilization system based on the improved two-way digital phase-locked amplifier as claimed in claim 1, wherein a faraday isolator is arranged between the laser and the saturated absorption spectrum generation optical path unit, and the laser is connected with a temperature control module.
8. The improved two-way digital lock-in amplifier based laser frequency stabilization system according to claim 2, wherein the three modulation signals generated by the first frequency synthesizer, the second frequency synthesizer and the third frequency synthesizer respectively have the same frequency and different phases.
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| CN104655588B (en) * | 2015-02-16 | 2017-08-25 | 中国科学院合肥物质科学研究院 | Frequency locker and its locking means based on tunable diode laser absorption spectrometry |
| CN107389603A (en) * | 2017-06-14 | 2017-11-24 | 北京航星网讯技术股份有限公司 | Gas sensor based on the adaptive a variety of environment of light signal strength |
| CN111256675B (en) * | 2020-01-19 | 2021-02-09 | 中国人民解放军国防科技大学 | Laser frequency stabilization system for nuclear magnetic resonance gyroscope |
| CN212626515U (en) * | 2020-07-01 | 2021-02-26 | 北京大学 | Locking system for DFB laser saturated absorption frequency stabilization |
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