Differential detection dual-color laser frequency stabilization method and system coexisting with multiple lamb-dips and lamb-peaks

Abstract

This invention provides a differential probe dual-color laser frequency stabilization method and system with multiple interactions of coexisting Lamb-dips and Lamb-peaks. Based on the multiple interactions between a multi-frequency laser and a quantum resonance system in a Doppler-free configuration, by setting the relative polarization directions and Raman phases of the pump and probe beams that propagate in opposite directions and coincidentally, resonance signals in the form of coexisting Lamb-dips and Lamb-peaks are obtained. Subtracting these two signals yields a quantum resonance signal with Doppler-free broadening eliminated. This invention obtains a Doppler-free spectral signal with coexisting Lamb-dips and Lamb-peaks and improved contrast, ultimately resulting in a significantly improved signal-to-noise ratio of the Doppler-free quantum resonance signal. This signal can be used for precise spectral measurements and laser frequency stabilization, enabling compact, miniaturized laser sources with ultra-low frequency noise. The system's size and power consumption are greatly reduced, while robustness is improved, resulting in a higher signal-to-noise ratio resonance signal and achieving ultra-high-performance laser frequency stabilization.

Description

Technical Field

[0001] This invention relates to the field of precision measurement, such as quantum frequency standards and precision spectroscopy, specifically a differential detection technology in which lamb-dips and lamb-peaks coexist. Background Technology

[0002] Lasers, especially semiconductor lasers, typically have free-running linewidths greater than MHz, and their frequencies fluctuate significantly due to factors such as temperature and drive current. This limits the performance potential and application range of laser-based precision measurement systems. Their linewidths can usually be narrowed using external cavity methods, such as external cavity diode lasers (ECDLs) based on Littrow or Littman structures. Frequency fluctuations can be suppressed by laser frequency stabilization, locking the laser frequency to a more stable reference frequency, such as by using the PDH (Pound-Drever-Hall) method to lock the transmission peak center of a high-Q Fabry-Perot (FP) cavity or a transition line in a highly stable quantum system.

[0003] Currently, laser frequency stabilization using FP cavities can achieve ultra-narrow linewidth (≤Hz) lasers, but it suffers from medium- to long-term frequency drift. Furthermore, its large size, sensitivity to vibration, and high cost limit its miniaturization applications. Laser frequency stabilization via quantum resonance systems can solve these problems. Commonly used stabilization methods include saturated absorption spectroscopy (SAS), polarization polarization spectroscopy, modulation transfer spectroscopy (MTS), and dual-color atomic vapor laser lock (DAVLL). These methods lock the laser frequency to the resonant signal of the quantum system using a narrow linewidth resonant signal.

[0004] Among these methods, dual-color laser frequency stabilization requires a large external magnetic field, and the unidirectional quantum resonance system causes a certain degree of Doppler broadening in the linewidth of the resonance signal, which is not conducive to obtaining high-frequency stability laser frequency stabilization. Saturated absorption spectroscopy requires not only pump and probe beams that propagate in opposite directions and coincide in space, but also spatially separated reference beams, resulting in a complex optical path and making miniaturization difficult using micro-atomic gas cells. Polarization-polarized spectroscopy typically provides a higher signal-to-noise ratio (SNR) for the discrimination signal than saturated absorption spectroscopy, but suffers from zero-point drift, causing a slow shift in laser frequency. Modulation-transfer spectroscopy provides a very high SNR for the discrimination signal and is the mainstream method for high-performance laser frequency stabilization. However, because it requires separate frequency or phase modulation of the pump beam, this is usually achieved using a large and power-consuming external modulator, such as an electro-optic modulator (EOM) or an acousto-optic modulator (AOM), which limits its miniaturization applications. The raw spectral signals obtained by current mainstream laser frequency stabilization methods cannot completely eliminate the background signal of Doppler broadening. Modulation and demodulation techniques are required to obtain Doppler-free error signals. While this is sufficient for laser frequency stabilization, it is insufficient for precise spectral measurements. When measuring the resonant transition frequency of a quantum system using a Doppler-free error signal obtained through modulation and demodulation, the zero-crossing point and drift of the error signal are closely related to the modulation and demodulation parameters, leading to measurement errors. Furthermore, frequency stabilization methods using light intensity detection, such as modulation-transfer spectroscopy, suffer from significant common-mode noise due to their intensity-based detection methods. This includes laser intensity noise (AM noise), amplitude noise caused by amplitude jitter from absorption spectral line conversion (FM-AM noise), and detector noise, which limits further improvements in the frequency stability of laser frequency stabilization systems. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a differential detection dual-color laser frequency stabilization method and system with multiple Lamb-dips and Lamb-peaks coexisting. The differential signal obtained eliminates the background of Doppler broadening, which can be used for precision spectral measurement and laser frequency locking, resulting in a laser frequency stabilization system with ultra-low frequency noise, compact structure, and miniaturization.

[0006] The technical solution adopted by this invention to solve its technical problem is: a differential detection dual-color laser frequency stabilization method with coexistence of Lamb-dips and Lamb-peaks. Based on the multiple interactions between a multi-frequency laser and a quantum resonance system in a Doppler broadening-free configuration, by setting the relative polarization directions and Raman phases of the pump and probe light that propagate in opposite directions and overlap spatially, resonance signals in the form of simultaneously existing Lamb-dips (absorption reduction) and Lamb-peaks (absorption enhancement) are obtained. Subtracting the two yields a quantum resonance signal that eliminates Doppler broadening. Specifically, the method includes the following steps:

[0007] 1) Provide a multi-frequency laser beam, the frequency components of which include f1 and f2, and the frequency interval is the splitting of the two ground state energy levels;

[0008] 2) The laser interacts with the quantum resonance system multiple times. The interaction adopts a Doppler broadening-free configuration, that is, the laser is split into pump light and probe light that propagate in opposite directions and overlap in space, and act on the quantum resonance system at the same time.

[0009] 3) By setting the relative polarization direction of the pump light and the probe light using a waveplate and setting the relative Raman phase of the pump light and the probe light using a mirror, the dark state prepared by the pump light and the two dark states prepared by the two polarization components of the probe light will undergo interference expansion and interference destruction respectively, thus obtaining an interaction configuration in which Lamb-dips (absorption reduction) and Lamb-peaks (absorption enhancement) coexist.

[0010] 4) After the probe light interacts with the quantum resonance system, the transmitted light is spatially and polarized, and its orthogonal polarization components are detected to obtain the Lamb-dips and Lamb-peaks signals that exist simultaneously.

[0011] 5) Subtract the Lamb-dips signal from the Lamb-peaks signal to obtain the differential signal.

[0012] Step 4) uses a balanced detector with two detection ports to detect the orthogonal polarization components of the transmitted light after spatial and polarization separation.

[0013] In step 5), the Lamb-dips signal and the Lamb-peaks signal are subtracted from each other using the differential output terminal of the balanced detector to obtain the differential signal.

[0014] The quantum resonance system described uses H, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, He, Ne, Ar, Kr, or Xe particles.

[0015] This invention also provides a differential detection dual-color laser frequency stabilization system with coexistence of Lamb-dips and Lamb-peaks, comprising a multi-frequency laser system, a high-reflectivity device, a quantum resonance system, a spatial and polarization separation device, and a detection device. The multi-frequency laser system generates dual-frequency laser light, which serves as pump light. Under the action of the high-reflectivity device, the dual-frequency laser light interacts multiple times with the quantum resonance system in a Doppler-free configuration. The transmitted light of the pump light, under the action of a polarizer and a mirror, becomes spatially reversed, coincident, and polarized at a certain angle as detection light. The detection light is incident on the quantum resonance system and interacts with it, generating Lamb-dips and Lamb-peaks respectively. The spatial and polarization separation device obtains the Lamb-dips and Lamb-peaks signals. The detection device captures the Lamb-dips and Lamb-peaks signals and performs differential analysis to obtain a differential signal used for laser frequency locking.

[0016] As a preferred embodiment, in the multi-frequency laser system, the microwave signal generated by the microwave signal source and the current provided by the DC power supply are connected to the microwave port and DC port of the bias coupler (Bias-Tee), respectively, driving the semiconductor laser to generate dual-color laser light. The dual-color laser light, after passing through a depolarization beam splitter, enters the quantum resonance system as pump light. The high-reflectivity device employs a pair of mirrors positioned on either side of the quantum resonance system. The pump light repeatedly enters the quantum resonance system under the action of the mirrors to increase the effective optical path of the interaction. The transmitted light of the pump light passes through a quarter-wave plate and the mirrors to obtain probe light that is spatially opposite, coincident, and polarized at a certain angle, and is incident on... The quantum resonance system interacts with the probe light, which has two orthogonal polarization components, namely parallel and perpendicular polarization components. These components interact with the quantum resonance system and generate lamb-dips and lamb-peaks, respectively. The transmitted light of the probe light is separated from the pump light, which is spatially opposite and coincident, by a depolarization beam splitter. Then, it passes through a quarter-wave plate and a half-wave plate in sequence, and is polarized by a polarization beam splitter. The parallel polarization component is detected by the detection device, resulting in a resonance signal with reduced absorption (lamb-dips), while the perpendicular polarization component is detected by the detection device, resulting in a resonance signal with enhanced absorption (lamb-dips). Finally, a differential signal is obtained.

[0017] As another preferred option, the high-reflectivity device is replaced by an FP cavity, which consists of two opposing cavity mirrors and is positioned on both sides of the quantum resonance system.

[0018] As a third preferred option, the probe light is replaced by a beam splitter obtained by depolarization beam splitting, and the half-wave plate is adjusted to make it at a certain angle with the polarization direction of the pump light.

[0019] As a fourth preferred embodiment, the spatial positions of the pump light and the probe light are interchanged, and the polarization conversion and differential detection are placed after the beam splitter; after passing through the electro-optic modulator, the pump light is incident on the quantum resonance system and interacts with it multiple times, during which four-wave mixing and modulation transfer occur, so that the probe light that has interacted with the quantum resonance system contains the modulation signal. The frequency discrimination signal can be obtained through coherent demodulation technology, thereby stabilizing the laser frequency.

[0020] The beneficial effects of this invention are:

[0021] 1. The interaction configuration of coexisting Lamb-dips and Lamb-peaks, based on pump light and probe light propagating in opposite directions and spatially overlapping, obtains a Doppler broadened spectral signal with enhanced contrast by setting the relative polarization direction and Raman phase;

[0022] 2. By subtracting the Lamb-dips and Lamb-peaks signals to obtain a differential signal, the background signal of Doppler broadening is significantly suppressed, leaving only the Doppler-free quantum resonance signal with an extremely narrow linewidth close to the natural linewidth. This differential signal has an increased amplitude relative to the Lamb-dips and Lamb-peaks signals, and the common-mode noise of the system is suppressed. Ultimately, the signal-to-noise ratio of the Doppler-free quantum resonance signal is greatly improved, which can be used for precise spectral measurement and laser frequency stabilization, realizing a compact, miniaturized laser source with ultra-low frequency noise.

[0023] 3. Employing a flexible frequency locking method, it can achieve locking of monochromatic or dual-frequency lasers without the need for a bulky and power-consuming external modulator. Dual-frequency lasers can be generated by directly modulating the laser drive current. Doppler-free quantum resonance signals can be obtained by scanning the laser drive current. When a frequency discrimination signal (error signal) is needed, a low-frequency (~MHz) modulation signal can be applied to the laser drive current terminal, which can be obtained through mature modulation and demodulation techniques. This greatly reduces the size and power consumption of the frequency stabilization system while improving its robustness.

[0024] 4. This invention has good compatibility and can be combined with other spectroscopic techniques, such as modulation transfer spectroscopy and polarization polarization spectroscopy, to obtain resonant signals with higher signal-to-noise ratios and achieve ultra-high performance laser frequency stabilization. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the principle of the present invention.

[0026] Figure 2 is a schematic diagram of four devices of the present invention.

[0027] Figure 3 This invention relates to the energy level configuration and its corresponding laser field schematic diagram, wherein (a) is a schematic diagram of a 2-level energy configuration and its corresponding laser field, and (b) is a schematic diagram of a 3-level energy configuration and its corresponding laser field.

[0028] Figure 4 The present invention relates to dual-frequency pump light and dual-frequency probe light and 87 Lamb-dips (solid lines) and Lamb-peaks (dashed lines) signal diagrams obtained from the single-action configuration of Rb atomic bubbles.

[0029] Figure 5 This is a signal diagram of Lamb-dips (solid line) and Lamb-peaks (dashed line) obtained by the configuration of the dual-frequency pump light and dual-frequency probe light interacting with 87Rb atomic bubbles multiple times according to the present invention.

[0030] Figure 6 This is a differential signal diagram of single-action (gray line) and multiple-action (black line) Doppler-free signal obtained by the present invention.

[0031] Among them, 1-laser system, 2-depolarization beam splitter, 3-reflector 1, 4-quantum resonance system, 5-reflector 2, 6-quarter-wave plate 1, 7-reflector 3, 8-quarter-glass plate 2, 9-half-wave plate, 10-polarization beam splitter, 11-detector 1, 12-detector 2, 13-electronic subtractor, 14-polarizer, 15-FP cavity mirror 1, 16-FP cavity mirror 2, 17-half-wave plate 1, 18-reflector 4, 19-reflector 5, 20-quarter-glass plate, 21-half-wave plate 2, 22-modulator. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention includes, but is not limited to, the following embodiments.

[0033] The quantum resonance system described in this invention can utilize H, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, He, Ne, Ar, Kr, and Xe particles; this invention uses lasers and... 87 The present invention is described using a laser frequency stabilization device achieved through Rb atom interactions as an example. However, the present invention is not limited thereto and its scope of application covers all the above configurations.

[0034] The present invention comprises a multi-frequency laser system, a high-reflectivity device, a quantum resonance system, a spatial and polarization separation device, and a detection device. The multi-frequency laser system generates dual-frequency lasers with frequency components f1 and f2, respectively. The dual-frequency lasers interact multiple times with the quantum resonance system in a Doppler-free configuration. The probe light undergoes spatial and polarization separation to obtain Lamb-dips and Lamb-peaks signals, which are then used to obtain differential signals through a balanced detector differential channel for laser frequency locking.

[0035] This invention provides a differential detection method with multiple interactions, comprising the following steps: First, a multi-frequency laser beam is generated, the frequency components of which include f1 and f2. In a Doppler broadening-free configuration, the laser beam is split into a pump beam and a probe beam that propagate in opposite directions and coincide in space, simultaneously interacting multiple times with the quantum resonance system. The relative polarization directions of the pump beam and the probe beam are set by a waveplate, and their relative Raman phases are set by a mirror, causing the dark state prepared by the pump beam and the two dark states prepared by the two polarization components of the probe beam to undergo interference expansion and interference destructive, respectively, resulting in an interaction configuration where Lamb-dips (absorption reduction) and Lamb-peaks (absorption enhancement) coexist. The transmitted light after the probe beam interaction, after spatial and polarization separation, is then detected by a balanced detector to obtain both Lamb-dips and Lamb-peaks signals. By subtracting the Lamb-dips signal and the Lamb-peaks signal from the differential output of the balanced detector, a differential signal is obtained. Compared with the Lamb-dips and Lamb-peaks signals, this differential signal eliminates the background signal of Doppler broadening and retains only the Doppler-free quantum resonance signal with a narrower linewidth. The amplitude of the Doppler-free resonance signal is increased, and the common-mode noise of the system is significantly suppressed.

[0036] The Lamb-dips and Lamb-peaks present in this invention configuration can be deconstructed into coherent and incoherent interaction processes. The incoherent interaction process mainly includes the following aspects: A) Saturation absorption process: Pump and probe beams propagating in opposite directions and spatially overlapping pass through the atomic system. According to the Doppler effect, only the atoms whose velocity component is zero along the probe beam path exhibit zero Doppler frequency shift and resonant interaction with both the pump and probe beams. Because the relatively strong pump beam increases the excitation rate of the absorption transitions of these atoms to a level comparable to the relaxation rate, it significantly reduces the ground state population, thus reducing the absorption of the probe beam and forming de-Pppler broadened Lamb-dips. B) Optical pumping of atomic populations between hyperfine levels. In this invention configuration, optical pumping prevents atoms from leaking into a single hyperfine level of the ground state, allowing more atoms to participate in the interaction of the two-color light, significantly enhancing the Lamb-dips and Lamb-peaks signals. C) Optical polarization process of polarization-polarized leakage states. In this invention's configuration, the forward-propagating pump light pumps the atomic population to a polarized leakage state, while the backward-propagating probe light is strongly absorbed, forming Lamb-peaks. The coherent interaction process in this configuration involves interference expansion or destructive processes between the bright and dark states prepared by the pump light and the bright and dark states prepared by the probe light. This can be adjusted by the relative polarization directions of the pump and probe light, the relative Raman phases of the two-color light, and the position of the mirror.

[0037] This invention provides four differential detection systems that enable multiple actions by coexisting Lamb-dips and Lamb-peaks.

[0038] The first system configuration is shown in Figure 2(a). First, the microwave signal generated by the microwave signal source and the current provided by the DC power supply are connected to the microwave and DC ports of the bias coupler (Bias-Tee), respectively, to drive the semiconductor laser system (1) to generate a dual-color laser. After passing through the depolarization beam splitter (2), the dual-color laser is used as pump light to interact with the quantum resonance system (4). The number of interactions can be set by a pair of high-reflectivity mirrors (3) and (5) to increase the effective optical path of the interaction and obtain a quantum resonance signal with higher contrast and signal-to-noise ratio. Then, the transmitted light of the pump light passes through the quarter-wave plate 1 (6) and the mirror (7) to obtain spatially reversed, coincident probe light with a certain polarization angle. This probe light is incident on the quantum resonance system and interacts with it. The two orthogonal polarization components of the probe light, namely the parallel and perpendicular polarization components, interact with the quantum resonance system and generate Lamb-dips and Lamb-peaks, respectively. After the interaction, the transmitted light of the probe light is separated from the pump light that is spatially opposite and coincident by the depolarization beam splitter (2). Then, it is polarized by the quarter-wave plate (8), the half-wave plate (9) and the polarization beam splitter (10). Its parallel polarization component is detected by the detector (11) to obtain the resonance signal with reduced absorption (Lamb-dips). The vertical polarization component is detected by the detector (12) to obtain the resonance signal with enhanced absorption (Lamb-dips). Finally, the differential signal is obtained by the electronic subtractor (13) of the differential port of the balanced detector.

[0039] The resonant signal described differs from the Lamb-dips signal obtained by the traditional Doppler broadening configuration. Our configuration, through differential detection of the parallel and perpendicular polarization components of the probe light, can simultaneously obtain both Lamp-dips and Lamp-peaks signals. The dual-frequency pump light and dual-frequency probe light interact with the 87Rb atomic bubble in a single (multiple) interaction, simultaneously obtaining Lamp-dips and Lamp-peaks signals as shown below. Figure 4 and Figure 5 As shown, Figure 4 The transition lines in the spectrum, from left to right, correspond to: |5 2 S 1 / 2 F = 1 & 2 > → |5 2 P 1 / 2 , F′=1>,|5 2 S 1 / 2 F = 1 & 2 > → |5 2 P 1 / 2 F′=2>, the middle part is the crossover resonance signal between the two. Figure 5 Mid-spectral line transitions and Figure 4The corresponding signals are the same. The Lamb-dips and Lamb-peaks signals, by finely adjusting the quarter-wave plate (8) and the half-wave plate (9), can have their Doppler broadening background signals made identical. By balancing the electronic subtractor (13) at the differential port of the detector, a differential signal eliminating the Doppler background is obtained, such as... Figure 6 As shown, Figure 6 Mid-spectral line transitions and Figure 4 The corresponding characters are the same. Figure 6 The transition lines in the spectrum, from left to right, correspond to: |5 2 S 1 / 2 F = 1 & 2 > → |5 2 P 1 / 2 , F′=1>,|5 2 S 1 / 2 F = 1 & 2 > → |5 2 P 1 / 2 F′=2>, with the cross-over signal between the two in the middle.

[0040] The laser described can generate single-frequency or dual-frequency lasers. When generating a single-frequency laser, its frequency is f1; in this case, the quantum resonance system 4 is a two-level system, such as... Figure 3 As shown in (a), there is a ground state: |g>, an excited state: |e>, and the laser frequency is locked to the transition frequency f of the two-level quantum resonance system. ge When dual-frequency lasers are generated, their frequencies are f1 and f2, respectively, as shown in the example. Figure 3 (b) The three-level quantum resonance system interacts, coupling the transitions from the two ground states to the common excited state, namely |g1>→|e> and |g2>→|e>. This dual-frequency laser can be obtained by directly modulating the multicolor light output from a semiconductor laser with microwaves. The two sidebands in the output multicolor light constitute the desired dual-frequency laser, and their frequency interval is the energy level interval between the two ground states: f g12 When the microwave frequency is f g12 At / (2k) (where k is a positive integer), the dual-frequency laser consists of ±k-level sidebands. This laser frequency stabilization system locks the laser carrier (0th level) frequency at the midpoint of the two resonant transition frequencies of the 3-level quantum resonance system, i.e., (f g1e +f g2e ) / 2; when the microwave frequency is f g12 When k = 2k-1 (where k is a positive integer), the dual-frequency laser consists of a 0th-order and a +k (or -k)-order sideband. This laser frequency stabilization system locks the laser carrier (0th-order sideband) frequency to one of the two resonant transition frequencies of the three-level quantum resonance system, i.e., f. g2e (f g1e ).

[0041] The interaction between dual-frequency lasers and the three-level quantum resonance system serves two purposes: firstly, to prevent the atomic population from leaking into other energy levels of the ground state, thereby increasing the atomic population involved in the interaction; and secondly, because the dual-color pump light can form a larger proportion of CPT dark states, which interact with the probe light, resulting in interference expansion or depletion, depending on the relative polarization direction and Raman phase of the dual-color pump and probe light. This can further increase the contrast of the Lamb-dips and Lamb-peaks signals, obtain a differential signal with a higher signal-to-noise ratio, and achieve a laser frequency stabilization device with better frequency stability.

[0042] The second system configuration is shown in Figure 2(b). This system is similar to the first scheme, except that it uses an FP cavity, which consists of two highly reflective cavity mirrors, FP cavity mirror 1 (15) and FP cavity mirror 2 (16), allowing multiple interactions to overlap spatially. The FP cavity used in this scheme will further increase the number of laser-quantum resonance system interactions, the utilization rate of the quantum resonance system, and the effective optical path of the interactions, significantly improving the contrast and signal-to-noise ratio of the quantum resonance signal.

[0043] The third system configuration is shown in Figure 2(c). The interaction configuration of the light and quantum system in this system is similar to that of the first system. The difference of this system is that: (1) the probe light is obtained by a depolarization beam splitter (2), which is beneficial to independently control and adjust the polarization and intensity of the pump light and the probe light, and simplifies the optical path adjustment; (2) the probe light is obtained at a certain angle to the polarization direction of the pump light by adjusting the half-wave plate. Its parallel and perpendicular polarization are used to obtain Lamp-dips and Lamp-peaks signals, respectively. The differential signal is obtained by using the differential port of the balanced detector. After modulation and demodulation, the frequency discrimination signal is obtained for laser frequency locking.

[0044] The fourth system configuration is shown in Figure 2(d). This system is similar to the third system, except that: (1) the spatial positions of the pump light and the probe light are interchanged, and polarization conversion and differential detection are placed after the depolarization beam splitter (2); (2) after the pump light is modulated by the electro-optic modulator (22), it is incident on the quantum resonance system and interacts with it multiple times. During this process, four-wave mixing and modulation transfer occur, so that the probe light that has interacted with the quantum resonance system contains the modulation signal. The frequency discrimination signal can be obtained through coherent demodulation technology, thereby stabilizing the laser frequency. This system combines differential detection and modulation transfer spectroscopy with the coexistence of Lamb-dips and Lamb-peaks, which can obtain a resonance signal with a higher signal-to-noise ratio and achieve ultra-high performance laser frequency stabilization.

Claims

1. A differential detection dual-color laser frequency stabilization method with coexistence of Lamb-dips and Lamb-peaks, characterized in that... Includes the following steps: Based on the multiple interactions between a multi-frequency laser and a quantum resonance system in a Doppler broadening-free configuration, by setting the relative polarization directions and Raman phases of the pump and probe beams that propagate in opposite directions and coincidentally, resonance signals in the form of Lamb-dips and Lamb-peaks are obtained simultaneously. Subtracting the two yields a quantum resonance signal free of Doppler broadening. The specific steps include: 1) Provide a multi-frequency laser beam, the frequency components of which include f1 and f2, and the frequency interval is the splitting of the two ground state energy levels; 2) The laser interacts with the quantum resonance system multiple times. The interaction adopts a Doppler broadening-free configuration, that is, the laser is split into pump light and probe light that propagate in opposite directions and overlap in space, and act on the quantum resonance system at the same time. 3) By setting the relative polarization direction of the pump light and the probe light using a waveplate, and setting the relative Raman phase of the pump light and the probe light using a mirror, the dark state prepared by the pump light and the two dark states prepared by the two polarization components of the probe light will undergo interference expansion and interference destructive, respectively, to obtain an interaction configuration in which Lamb-dips and Lamb-peaks coexist. 4) After the probe light interacts with the quantum resonance system, the transmitted light is spatially and polarized, and its orthogonal polarization components are detected to obtain the Lamb-dips and Lamb-peaks signals that exist simultaneously. 5) Subtract the Lamb-dips signal from the Lamb-peaks signal to obtain the differential signal.

2. The differential detection dual-color laser frequency stabilization method with coexistence of Lamb-dips and Lamb-peaks according to claim 1, characterized in that: Step 4) uses a balanced detector with two detection ports to detect the orthogonal polarization components of the transmitted light after spatial and polarization separation.

3. The differential detection dual-color laser frequency stabilization method with coexistence of Lamb-dips and Lamb-peaks according to claim 1, characterized in that: In step 5), the Lamb-dips signal and the Lamb-peaks signal are subtracted from each other using the differential output terminal of the balanced detector to obtain the differential signal.

4. The differential detection dual-color laser frequency stabilization method with coexistence of Lamb-dips and Lamb-peaks according to claim 1, characterized in that: The quantum resonance system described uses H, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, He, Ne, Ar, Kr, or Xe particles.

5. A differential detection dual-color laser frequency stabilization system employing the method described in claim 1, characterized in that: The differential probe dual-color laser frequency stabilization system, which allows for the coexistence of Lamb-dips and Lamb-peaks, includes a multi-frequency laser system, a high-reflectivity device, a quantum resonance system, a spatial and polarization separation device, and a detection device. The multi-frequency laser system generates dual-frequency laser light, which serves as pump light. Under the action of the high-reflectivity device, the dual-frequency laser light interacts multiple times with the quantum resonance system in an anti-Doppler configuration. The transmitted light of the pump light, under the action of a polarizer and a mirror, becomes spatially reversed, coincident, and polarized at a certain angle as probe light. The probe light is incident on the quantum resonance system and interacts with it, generating Lamb-dips and Lamb-peaks respectively. The spatial and polarization separation device obtains the Lamb-dips and Lamb-peaks signals. The detection device captures the Lamb-dips and Lamb-peaks signals and performs differential analysis to obtain a differential signal used for laser frequency locking.

6. The differential detection dual-color laser frequency stabilization system with coexistence of Lamb-dips and Lamb-peaks according to claim 5, characterized in that: In the aforementioned multi-frequency laser system, the microwave signal generated by the microwave signal source and the current provided by the DC power supply are connected to the microwave port and DC port of the bias coupler, respectively, driving the semiconductor laser to generate a dual-color laser. The dual-color laser, after passing through a depolarization beam splitter, serves as pump light into the quantum resonance system. The high-reflectivity device employs a pair of mirrors positioned on either side of the quantum resonance system. The pump light repeatedly enters the quantum resonance system under the influence of the mirrors to increase the effective optical path of the interaction. The transmitted light of the pump light passes through a quarter-wave plate and the mirrors to obtain probe light that is spatially opposite, coincident, and polarized at a certain angle. The probe light is directed to the quantum resonance system and interacts with it. The two orthogonal polarization components of the probe light, namely the parallel and perpendicular polarization components, interact with the quantum resonance system and generate Lamb-dips and Lamb-peaks, respectively. The transmitted light of the probe light is separated from the pump light, which is spatially opposite and coincident, by a depolarization beam splitter. Then, it passes through a quarter-wave plate and a half-wave plate in sequence, and is polarized by a polarization beam splitter. The parallel polarization component is detected by the detection device, resulting in a resonant signal with reduced absorption, while the perpendicular polarization component is detected by the detection device, resulting in a resonant signal with enhanced absorption. Finally, a differential signal is obtained.

7. The differential detection dual-color laser frequency stabilization system with coexistence of Lamb-dips and Lamb-peaks according to claim 6, characterized in that: The high-reflectivity device is replaced by an FP cavity, which consists of two opposing cavity mirrors and is positioned on both sides of the quantum resonance system.

8. The differential detection dual-color laser frequency stabilization system with coexistence of Lamb-dips and Lamb-peaks according to claim 7, characterized in that: The probe light is replaced by a beam splitter obtained by depolarization beam splitting, and the half-wave plate is adjusted to make it at a certain angle with the polarization direction of the pump light.

9. The differential detection dual-color laser frequency stabilization system with coexistence of Lamb-dips and Lamb-peaks according to claim 8, characterized in that: The spatial positions of the pump light and the probe light are interchanged, and polarization conversion and differential detection are placed after the beam splitter; After passing through an electro-optic modulator, the pump light is incident on the quantum resonance system and interacts with it multiple times. During this process, four-wave mixing and modulation transfer occur, so that the probe light that has interacted with the quantum resonance system contains the modulation signal. The discriminant signal is obtained through coherent demodulation technology, thereby stabilizing the laser frequency.

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