Ultra-stable laser tuning system and laser tuning method

Abstract

The present application provides an ultra-stable laser tuning system and a laser tuning method, which relate to the field of ultra-stable laser technology. The system integrates a laser, a frequency shift unit, a PDH frequency stabilization control unit and an ultra-stable cavity, and can achieve large-scale high-precision tuning of ultra-stable lasers. Specifically, in the present application, an acousto-optic modulator and an electro-optic modulator are additionally introduced when performing ultra-stable laser tuning, which will not increase additional locking noise and out-of-loop drift, ensuring that the performance indicators of the ultra-stable laser are maintained. In addition, high-precision tuning of the ultra-stable laser can be achieved by changing the frequency of the acousto-optic modulator, and large-scale tuning of the ultra-stable laser can be achieved by changing the frequency of the electro-optic modulator, which has the effect of achieving large-scale, high-precision frequency tuning without dead zones.

Description

Technical Field

[0001] The present application relates to the field of ultra-stable laser technology, and in particular to an ultra-stable laser tuning system and a laser tuning method. Background Art

[0002] Ultrastable lasers play a vital role in the fields of precision science and high-end technology applications. This type of laser is known for its excellent frequency stability and accuracy. It is a key technology for realizing a variety of applications such as laser precision control of atoms, precision measurement, long-distance quantum communication, and optical clock servo. These applications have extremely high requirements for the tunable range and accuracy of laser frequency. It is necessary to perform a large range of frequency adjustment at the order of hundreds of megahertz (MHz) or even gigahertz (GHz), and simultaneously achieve high-precision tuning at the level of Hertz (Hz), millihertz (mHz), and even microhertz (μHz). Since the frequency stability of an ultrastable laser depends mainly on the length of its resonant cavity, the design of the resonant cavity usually needs to work at the inflection point temperature to obtain the best temperature characteristics. Although this temperature control strategy helps to improve frequency stability, it also limits the laser frequency range in which the cavity length can be adjusted, which is usually at the order of MHz. Therefore, ultrastable lasers need to be frequency tuned over a large range and with high precision.

[0003] In order to achieve wide range and high precision tuning of ultra-stable laser frequency, an additional laser is introduced in the prior art, and its frequency is locked to the ultra-stable laser through the offset frequency locking technology. This method requires an additional laser frequency locking control system and the use of a narrow linewidth laser, resulting in a complex system structure and high cost. In addition, locking the offset frequency of the additional laser to the ultra-stable laser will introduce additional noise and out-of-loop drift, increase the locking noise and out-of-loop drift of the system, and deteriorate the performance indicators of the ultra-stable laser. Summary of the invention

[0004] In view of the above problems, the present application provides an ultra-stable laser tuning system and a laser modulation method, including:

[0005] In a first aspect, the present application provides an ultra-stable laser tuning system, the ultra-stable laser tuning system comprising: a laser, a frequency shift unit, a PDH frequency stabilization control unit and an ultra-stable cavity;

[0006] The laser is used to generate narrow line width laser, and the narrow line width laser is input into the frequency shift unit; the frequency shift unit includes a first electro-optic modulator EOM1, a second electro-optic modulator EOM2, a first acousto-optic modulator AOM1 and a second acousto-optic modulator AOM2;

[0007] The narrow linewidth laser is divided into two paths after being modulated by the first acousto-optic modulator AOM1, the first path of laser is output as an optical signal, and the second path of laser is processed by the second acousto-optic modulator AOM2, the first electro-optic modulator EOM1 and the second electro-optic modulator EOM2;

[0008] The frequency shift unit is used to input the processed second laser into the ultra-stable cavity, the processed second laser resonates in the ultra-stable cavity, and an error signal is generated in the optical coupling control part according to the resonance result;

[0009] The PDH frequency stabilization control unit is used to control the laser and the first acousto-optic modulator AOM1 to compensate the frequency by detecting the error signal until the output frequency of the laser is locked on the resonance frequency of the ultra-stable optical cavity.

[0010] Optionally, the frequency shift unit is specifically used to generate an adjustable frequency sideband using the first electro-optical modulator EOM1, and the adjustable frequency sideband is used for frequency tuning to achieve wide range frequency tuning;

[0011] The AOM2 is used to adjust the frequency of the second laser to achieve high-precision tuning of the laser.

[0012] Optionally, the frequency shifting unit is further used for:

[0013] Scanning the frequency of the laser, and selecting a target frequency point in the transmission signal displayed on the photodetector according to the output frequency;

[0014] Determining the polarity of the frequency shift according to the target frequency point;

[0015] A positive frequency shift or a negative frequency shift operation is performed according to the polarity of the frequency shift.

[0016] Optionally, the system further comprises a control module, which is used to decompose the frequency according to the tuning amount after determining the polarity of the frequency shift;

[0017] The frequency shift unit is specifically used to change the modulation frequency of the EOM1 based on the decomposed tuning amount to achieve wide-range tuning and change the modulation frequency of the AOM2 to achieve high-precision tuning.

[0018] Optionally, the frequency shift unit is specifically used to change the modulation frequency of the EOM1 using a high-frequency DDS frequency synthesizer to achieve wide-range frequency tuning of the ultra-stable laser;

[0019] The modulation frequency of the AOM2 is changed by a low-frequency DDS frequency synthesizer to achieve high-precision frequency tuning of the ultra-stable laser.

[0020] Optionally, the system also includes a frequency display and control unit for displaying the output frequency of the ultra-stable laser tuning system in real time and receiving external instructions to accurately control the modulation frequencies of the EOM1 and the AOM2 by adjusting the frequency control register of the DDS, thereby achieving wide-range precise tuning of the ultra-stable laser frequency.

[0021] In a second aspect, the present application provides an ultra-stable laser tuning method, the ultra-stable laser tuning method comprising:

[0022] Generate narrow linewidth laser, and input the narrow linewidth laser into a frequency shift unit, wherein the frequency shift unit includes a first electro-optic modulator EOM1, a second electro-optic modulator EOM2, a first acousto-optic modulator AOM1, and a second acousto-optic modulator AOM2;

[0023] The narrow linewidth laser is divided into two paths after being modulated by the first acousto-optic modulator AOM1, the first path of laser is output as an optical signal, and the second path of laser is processed by the second acousto-optic modulator AOM2, the first electro-optic modulator EOM1 and the second electro-optic modulator EOM2;

[0024] Inputting the processed second laser into an ultrastable cavity, wherein the processed second laser resonates with the ultrastable cavity in the ultrastable cavity, and generating an error signal in the optical coupling control part according to the resonance result;

[0025] The error signal is detected, and the laser and the first acousto-optic modulator AOM1 are controlled to compensate the frequency until the output frequency of the laser is locked on the resonance frequency of the ultra-stable optical cavity.

[0026] Optionally, before inputting the processed second laser into the ultrastable cavity, the method further includes:

[0027] Scanning the frequency of the laser, and selecting a target frequency point in the transmission signal displayed on the photodetector according to the output frequency;

[0028] Determining the polarity of the frequency shift according to the target frequency point;

[0029] A positive frequency shift or a negative frequency shift operation is performed according to the polarity of the frequency shift.

[0030] Optionally, after determining the polarity of the frequency shift, the method further includes:

[0031] Decomposed according to the amount of tuning of the frequency;

[0032] Based on the decomposed tuning amount, the modulation frequency of the EOM1 is changed to achieve wide-range tuning, and the modulation frequency of the AOM2 is changed to achieve high-precision tuning.

[0033] Optionally, the changing the modulation frequency of the EOM1 based on the decomposed tuning amount to achieve wide-range tuning and the changing the modulation frequency of the AOM2 to achieve high-precision tuning includes:

[0034] Using a high-frequency DDS frequency synthesizer to change the modulation frequency of the EOM1 to achieve a wide range of frequency tuning of the ultra-stable laser;

[0035] A low-frequency DDS frequency synthesizer is used to change the modulation frequency of the AOM2 to achieve high-precision frequency tuning of the ultra-stable laser.

[0036] The present application provides an ultra-stable laser tuning system. The system includes a laser, a frequency shift unit, a PDH frequency stabilization control unit and an ultra-stable cavity, wherein the laser is used to generate a narrow linewidth laser, and the narrow linewidth laser is input into the frequency shift unit; the frequency shift unit includes a first electro-optic modulator EOM1, a second electro-optic modulator EOM2, a first acousto-optic modulator AOM1 and a second acousto-optic modulator AOM2; the narrow linewidth laser is modulated by the first acousto-optic modulator AOM1 and divided into two paths, the first path of laser is output as an optical signal, and the second path of laser is processed by the second acousto-optic modulator AOM2, the first electro-optic modulator EOM1 and the second electro-optic modulator EOM2; the frequency shift unit is used to input the processed second path of laser into the ultra-stable cavity, the processed second path of laser resonates in the ultra-stable cavity, and an error signal is generated in the optical coupling control part according to the resonance result; the PDH frequency stabilization control unit is used to control the laser and the first acousto-optic modulator AOM1 to compensate the frequency by detecting the error signal until the output frequency of the laser is locked on the resonant frequency of the ultra-stable optical cavity. By adopting the above system solution, an efficient and accurate laser frequency stabilization control system is realized. The system combines the laser, the frequency shift unit, the PDH frequency stabilization control unit and the ultra-stable cavity, and realizes the accurate control of the ultra-stable laser frequency through a carefully designed modulation process. The system has the following beneficial effects: when performing ultra-stable laser tuning, an acousto-optic modulator and an electro-optic modulator are additionally introduced, which will not increase the additional locking noise and out-of-loop drift, ensuring that the performance indicators of the ultra-stable laser are maintained. In addition, by changing the frequency of the acousto-optic modulator, the ultra-stable laser can be tuned with high precision, and by changing the frequency of the electro-optic modulator, the ultra-stable laser can be tuned over a wide range, which has the effect of realizing a wide range of high-precision frequency tuning without dead zones. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in this embodiment or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 A schematic diagram of the structure of an ultra-stable laser tuning system provided in an embodiment of the present application;

[0039] Figure 2 A schematic diagram of a transmission signal provided in an embodiment of the present application;

[0040] Figure 3 A schematic diagram of the structure of another ultra-stable laser tuning system provided in an embodiment of the present application;

[0041] Figure 4 A flow chart of an ultra-stable laser tuning method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] Figure 1 A schematic diagram of the structure of an ultra-stable laser tuning system provided in an embodiment of the present application. Figure 1 As shown, the ultra-stable laser tuning system provided in the embodiment of the present application may include: a laser 10, a frequency shift unit 11, a PDH frequency stabilization control unit 12, and an ultra-stable cavity 13.

[0044] The laser 10 is a narrow linewidth laser, which is a laser that can produce extremely narrow linewidth lasers. Compared with traditional wide linewidth lasers, narrow linewidth lasers have narrower spectral linewidths, and therefore can achieve higher time resolution and frequency resolution. The narrow linewidth laser provided in the embodiment of the present application is specifically used to output a laser with a frequency of f, and after being processed by the frequency shifting unit 11, two lasers are obtained, wherein the first laser is used as the final output light of the ultra-stable laser. The second laser is used as a reference light for ultra-stable laser locking.

[0045] The frequency shift unit 11 includes a first electro-optic modulator EOM1, a second electro-optic modulator EOM2, a first acousto-optic modulator AOM1 and a second acousto-optic modulator AOM2, which are used to process the second laser and input the processed second laser into the PDH frequency stabilization control unit. After generating narrow linewidth laser, the narrow linewidth laser is input into the frequency shift unit 11. The first acousto-optic modulator AOM1 in the frequency shift unit 11 processes the laser and then outputs two lasers through a fiber beam splitter. The first light is used as the final output light of the ultra-stable laser, and the second light is used as the reference light for locking the ultra-stable laser. The AOM1 can be a 1550 nm AOM1, that is, the working wavelength is 1550 nanometers. Further, the fiber beam splitter is also 1550 nm.

[0046] After obtaining the first laser and the second laser, the second laser is first modulated by AOM2 in the frequency shift unit 11. The acousto-optic modulator can generate a periodically changing refractive index in the medium through ultrasonic waves, thereby modulating the light. The specific modulation parameters (such as modulation frequency, modulation depth, etc.) will be determined according to the application requirements. Subsequently, the second light is modulated again by EOM1. The electro-optic modulator modulates the phase, intensity or polarization state of light by changing the refractive index of the material. Specifically, the first electro-optic modulator EOM1 is used to generate fixed frequency sidebands. This is usually achieved by applying a radio frequency (RF) signal to EOM1, which causes symmetrical sidebands to appear in the spectrum of the laser. The interval between these sidebands and the main laser frequency is equal to the frequency of the RF signal. Similar to AOM2, the specific modulation parameters of EOM1 will also be set according to application requirements. The laser modulated by EOM1 enters EOM2 for radio frequency electro-optic phase modulation. This modulation method allows high-frequency (RF range) phase modulation of optical signals, which is commonly used in optical communications, sensing, quantum information and other fields. The phase of light can be precisely controlled by RF electro-optic phase modulation, which is essential for experiments or applications that require high-precision phase control. The second electro-optic modulator EOM2 is specifically used to generate adjustable frequency sidebands for frequency tuning. Similar to EOM1, EOM2 also generates sidebands by applying an RF signal, but here the RF signal frequency is adjustable, allowing fine control of the sideband frequency.

[0047] The frequency shift unit can achieve accurate control and adjustment of the laser frequency and generate sidebands for PDH frequency locking by combining EOM1 or AOM2.

[0048] The second laser beam processed by the frequency shift unit enters the ultra-stable cavity 13 through the spatial optical path of the optical coupling control part. The processed second laser beam resonates in the ultra-stable cavity, and an error signal is generated in the optical coupling control part according to the resonance result. The PDH frequency stabilization control unit is used to control the laser and the first acousto-optic modulator AOM1 to compensate the frequency by detecting the error signal until the output frequency of the laser is locked on the resonant frequency of the ultra-stable optical cavity.

[0049] When the second laser beam processed by the frequency shift unit enters the PDH frequency stabilization control unit, it is necessary to use the PDH frequency stabilization technology for frequency stabilization processing. First, the frequency error detection of the processed second laser beam and the ultra-stable cavity is performed to obtain detuning information, and then the laser frequency generated by the laser is tuned based on the detuning information until the PDH frequency stabilization control unit locks the output frequency of the laser to the resonance frequency of the ultra-stable optical cavity.

[0050] The process of performing frequency stabilization processing in the PDH frequency stabilization control unit is introduced below in conjunction with a specific embodiment.

[0051] First, the second laser beam processed by the adjustment unit is scanned. During the scanning process, the signal of the transmitted light is checked by a photoelectric detector. Three frequency points can be observed on the photoelectric detector, such as Figure 2 As shown, Figure 2 A transmission signal schematic diagram provided for an embodiment of the present application, due to the modulation effect of EOM1 or AOM2, symmetrical sidebands will be generated on both sides of the original laser frequency. The difference between the frequency of these sidebands and the original laser frequency is equal to the modulation frequency of the modulator. Among them, the first frequency point is the result of the superposition of the original laser frequency and a sideband frequency generated by EOM1 or AOM2 modulation. If this frequency point is selected, since the modulation frequency of EOM1 or AOM2 is added to the original frequency, the output laser frequency will be slightly higher than the resonance frequency of the ultra-stable cavity (i.e., positive frequency shift); the second frequency point is the unmodulated original laser frequency. However, in PDH frequency stabilization control, this frequency point is usually not directly selected because it does not contain the information generated by the modulation, which is not conducive to frequency stability and locking; the third frequency point is the result of the superposition of the original laser frequency and another sideband frequency generated by EOM or AOM modulation. In contrast to the first frequency point, due to the subtraction effect of the modulation frequency, if this frequency point is selected, the output laser frequency will be slightly lower than the resonance frequency of the ultra-stable cavity (i.e., negative frequency shift).

[0052] When the first frequency point (positive frequency shift) is selected, the output frequency (f out ) is the resonant frequency of the ultrastable cavity (f fp ) minus the modulation frequency of AOM2 (f s1) plus the modulation frequency of EOM1 (f s2 ). That is, f out =f fp -f s1 +f s2 ;

[0053] When the third frequency point (negative frequency shift) is selected, the output frequency (f out ) is the resonant frequency of the ultrastable cavity (f fp ) minus the modulation frequency of AOM2 (f s1 ) minus the modulation frequency of EOM1 (f s2 ). That is, f out =f fp -f s1 -f s2 .

[0054] After selecting the frequency point, the laser signal modulated by EOM2 is introduced into the ultrastable cavity through the spatial optical path. As a high-precision optical resonator, the ultrastable cavity will enhance and feedback the input laser signal to generate a reflected light signal. These reflected light signals contain important information about the frequency detuning between the laser and the ultrastable cavity. The photodetector is responsible for capturing these reflected light signals and converting them into electrical signals. Subsequently, the frequency detuning information between the laser and the ultrastable cavity can be extracted from these electrical signals through phase demodulation technology. After processing, this information will form an error signal, which accurately reflects the deviation between the current laser frequency and the resonant frequency of the ultrastable cavity. In order to correct this deviation, the error signal needs to be further processed.

[0055] First, a low-pass filter can be used to remove high-frequency noise from the error signal and retain its low-frequency part, thereby obtaining more accurate deviation information. Next, the filtered error signal is sent to a proportional integral circuit (PI circuit). The PI circuit generates a control signal based on the size and duration of the error signal. The size and direction of this control signal are precisely calculated to ensure that the deviation of the laser frequency can be effectively compensated. Finally, this control signal is fed back to the piezoelectric ceramic or acousto-optic modulator of the laser. Piezoelectric ceramics fine-tune the output frequency of the laser through tiny displacements, while the acousto-optic modulator can achieve larger adjustments by changing the frequency of the optical signal. Under the joint action of the two, the output frequency of the laser will gradually approach the resonant frequency of the ultra-stable cavity, and finally achieve stable locking of the laser frequency.

[0056] Through the above feedback control process, the output frequency of the narrow linewidth laser is gradually adjusted to be consistent with the resonance frequency of the ultra-stable optical cavity. When the laser frequency is stably locked on the resonance frequency of the optical cavity, the output of the ultra-stable laser is achieved.

[0057] As mentioned above, in order to gradually adjust the output frequency of the narrow linewidth laser to be consistent with the resonant frequency of the ultra-stable optical cavity, the frequency needs to be tuned. The ultra-stable laser tuning system introduced in the embodiment of the present application also includes a control module for realizing precise control of the laser frequency.

[0058] Specifically, in a PDH frequency stabilization control system, it is usually necessary to decompose and perform corresponding frequency adjustments according to the polarity of the frequency shift and the required tuning amount. In a PDH frequency stabilization control system, it is first necessary to determine the polarity of the frequency detuning between the laser and the ultra-stable cavity (i.e., the direction of the frequency deviation) through phase demodulation technology. This is usually achieved by comparing the phase difference between the reflected light signal and the reference signal.

[0059] Once the polarity of the frequency shift is determined, the tuning task needs to be broken down according to the amount of tuning required. Typically, large-scale frequency adjustments are performed by the EOM because it can quickly change the phase or frequency of the optical signal, which is suitable for fast, large-scale tuning. High-precision tuning is performed by the AOM because the AOM can achieve precise control of the optical signal frequency, which is suitable for fine tuning. In this application, the part that is larger than the resolution of the high-frequency DDS frequency synthesizer is achieved by changing the modulation frequency f of the EOM1. s2 To achieve a wide range of tuning, the part that is smaller than the resolution of the high-frequency DDS frequency synthesizer is adjusted by changing the modulation frequency f of AOM2. s1 To achieve high precision tuning, such as Figure 3 As shown, Figure 3 A schematic diagram of the structure of another ultra-stable laser tuning system provided in an embodiment of the present application, wherein the ultra-stable laser tuning system also includes a high-frequency DDS (direct digital frequency synthesizer) frequency synthesizer and a low-frequency DDS frequency synthesizer, which are respectively used to change the modulation frequencies of the EOM and the AOM to achieve wide-range and high-precision tuning.

[0060] Using EOM1 for wide range tuning: Use a high-frequency DDS frequency synthesizer to change the modulation frequency of EOM1. The modulated frequency is expressed by f s2 The DDS frequency synthesizer can quickly generate accurate and stable frequency signals, which is essential for achieving a wide range of tuning of EOM1. By adjusting the frequency output of the DDS, the modulation frequency of EOM1 can be controlled, thereby achieving a wide range of adjustment of the laser frequency.

[0061] High-precision tuning using AOM2: The modulation frequency of AOM2 is changed by a low-frequency DDS frequency synthesizer. Since AOM is more sensitive to the frequency change of the optical signal, the use of low-frequency DDS can achieve precise control of the modulation frequency of AOM2. In this way, AOM2 can be used to fine-tune the laser frequency to achieve high-precision frequency stabilization control. The modulated frequency is expressed by f s1express.

[0062] The above tuning process can achieve efficient control of the laser frequency by combining the tuning capabilities of EOM and AOM. Among them, EOM is used for large-range coarse tuning, while AOM is used for high-precision fine tuning. The two complement each other and improve the tuning efficiency of the entire system. The DDS frequency synthesizer is used to accurately control the modulation frequency of EOM and AOM to ensure the accuracy of tuning. High-frequency DDS is used for EOM to achieve large-range tuning, and low-frequency DDS is used for AOM to achieve high-precision tuning, ensuring the frequency stability accuracy of the entire system. This tuning strategy can flexibly adjust the tuning range and accuracy as needed. By changing the frequency output of DDS, the modulation frequency of EOM and AOM can be easily adjusted, thereby achieving flexible control of the laser frequency.

[0063] In summary, by combining the tuning capabilities of EOM and AOM and using DDS frequency synthesizer to accurately control their modulation frequencies, efficient, accurate and flexible control of the laser frequency can be achieved, which is very important for the PDH frequency stabilization control system.

[0064] The following is an example of how to tune the frequency of an ultra-stable laser. In this example, a low-frequency DDS with a system clock of 200MHz is used to drive the AOM2. The frequency control bit number is up to 48 bits, providing a frequency control accuracy of about 0.7μHz. Assuming that a positive frequency shift of 1.2GHz is to be achieved, the target frequency shift amount f is first shift , using the formula f s2 =f shift +f s1 To set the frequency control register of the high-frequency DDS. In this example, the frequency control register of the high-frequency DDS is set to 1533916891, so that the output frequency f of EOM1 s2 Then, using the formula f s1 =f s2 -f shift To calculate the frequency that the low-frequency DDS needs to output, and set it to 49999999.650754Hz. In this way, through the synergy of EOM1 and AOM2, frequency tuning with an accuracy better than 1μHz is achieved.

[0065] If you want to achieve a negative frequency shift of 1.2 GHz, you can also use the above formula to calculate and set it. For negative frequency shift, use the formula f s2 =f shift -f s1 To set the frequency control register of the high-frequency DDS, get the output frequency of EOM1. Then, use the formula f s1 =f shift -fs2 To calculate the frequency that the low-frequency DDS needs to output. In this example, the frequency control register of the high-frequency DDS is set to 1411203540, making the output frequency f of EOM1 s2 The output frequency of the low-frequency DDS is set to 50000000.093132 Hz. In this way, frequency tuning with an accuracy better than 1 μHz is also achieved.

[0066] In the above embodiment, it is introduced how to achieve a wide range and high precision tuning of the ultra-stable laser frequency by combining the modulation frequency adjustment of EOM (electro-optic modulator) and AOM (acousto-optic modulator), and using high-frequency DDS and low-frequency DDS frequency synthesizers. However, a complete laser frequency stabilization system requires not only the precise coordination of these hardware components, but also a unit that can monitor and flexibly control these components in real time.

[0067] Therefore, a frequency display and control unit is introduced, which plays a vital role in this system. The main functions of this unit are twofold: first, it can display the output frequency of the ultra-stable laser tuning system in real time, providing operators with intuitive frequency status information; second, it can receive external instructions and accurately control the modulation frequency of EOM1 and AOM2 by adjusting the frequency control register of DDS, thereby achieving precise control of the ultra-stable laser frequency.

[0068] Specifically, the frequency display and control unit calculates the modulation frequency of EOM1 and AOM2 in real time by reading the value of the frequency control register of the DDS, and calculates the output frequency of the ultra-stable laser accordingly. Then, it displays this frequency value on the user interface for the operator's reference. At the same time, the operator can also input frequency adjustment instructions through the user interface. After these instructions are received by the frequency display and control unit, they will be converted into the corresponding DDS frequency control register value and written into the DDS, thereby realizing the precise adjustment of the modulation frequency of EOM1 and AOM2.

[0069] In this way, the frequency display and control unit not only improves the automation of the laser frequency stabilization system, but also greatly enhances the flexibility and controllability of the system. Operators can adjust the laser frequency at any time as needed to meet the needs of different experiments and applications. At the same time, the real-time displayed frequency information also provides an important reference for operators, helping them to better understand the operating status of the system.

[0070] The above embodiment introduces an ultra-stable laser tuning system. The present application also provides a corresponding ultra-stable laser tuning method for the ultra-stable laser tuning system. The ultra-stable laser tuning method provided by the embodiment of the present application is introduced below in combination with a specific embodiment. Figure 4 , Figure 4 A flow chart of an ultra-stable laser tuning method provided in an embodiment of the present application:

[0071] S401, generating narrow linewidth laser, and inputting the narrow linewidth laser into a frequency shift unit, wherein the frequency shift unit includes a first electro-optic modulator EOM1, a second electro-optic modulator EOM2, a first acousto-optic modulator AOM1, and a second acousto-optic modulator AOM2;

[0072] S402, the narrow linewidth laser is divided into two paths after being modulated by the first acousto-optic modulator AOM1, the first path of laser is output as an optical signal, and the second path of laser is processed by the second acousto-optic modulator AOM2, the first electro-optic modulator EOM1 and the second electro-optic modulator EOM2;

[0073] S403, inputting the processed second laser into the ultra-stable cavity, wherein the processed second laser resonates with the ultra-stable cavity in the ultra-stable cavity, and generating an error signal in the optical coupling control part according to the resonance result;

[0074] S404, detecting the error signal, and controlling the laser and the first acousto-optic modulator AOM1 to compensate the frequency until the modulation frequency after the output of the laser is locked on the resonance frequency of the ultra-stable optical cavity.

[0075] In an implementation method of the embodiment of the present application, before inputting the processed second laser into the ultra-stable cavity, the method further includes:

[0076] Scanning the frequency of the laser, and selecting a target frequency point in the transmission signal displayed on the photodetector according to the output frequency;

[0077] Determining the polarity of the frequency shift according to the target frequency point;

[0078] A positive frequency shift or a negative frequency shift operation is performed according to the polarity of the frequency shift.

[0079] In an implementation method of an embodiment of the present application, after determining the polarity of the frequency shift, the method further includes:

[0080] Decomposed according to the amount of tuning of the frequency;

[0081] Based on the decomposed tuning amount, the modulation frequency of the EOM1 is changed to achieve wide-range tuning, and the modulation frequency of the AOM2 is changed to achieve high-precision tuning.

[0082] In an implementation method of an embodiment of the present application, the changing the modulation frequency of the EOM1 based on the decomposed tuning amount to achieve wide-range tuning and the changing the modulation frequency of the AOM2 to achieve high-precision tuning include:

[0083] Using a high-frequency DDS frequency synthesizer to change the modulation frequency of the EOM1 to achieve a wide range of frequency tuning of the ultra-stable laser;

[0084] A low-frequency DDS frequency synthesizer is used to change the modulation frequency of the AOM2 to achieve high-precision frequency tuning of the ultra-stable laser.

[0085] The specific implementation process of the ultra-stable laser tuning method is based on the ultra-stable laser tuning system in the above embodiment, and the specific implementation process will not be repeated here.

[0086] The ultra-stable laser frequency tuning method and system provided by the present invention can achieve the effect of large-scale high-precision ultra-stable laser tuning. Compared with the prior art solution of adding a laser frequency locking control system, it has the following advantages:

[0087] 1. Adopt high and low frequency DDS drive, match with acousto-optic modulator and electro-optic modulator, realize ultra-stable frequency tuning with large range, high precision and no dead zone.

[0088] 2. No additional locking noise and out-of-loop drift will be introduced, ensuring that the performance indicators of the ultra-stable laser will not deteriorate.

[0089] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0090] It should also be noted that the various embodiments in this specification are described in a progressive manner, and the same and similar parts between the various embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and apparatus embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiments. The device and apparatus embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components indicated as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0091] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An ultra-stable laser tuning system, characterized in that: The ultra-stable laser tuning system comprises: a laser, a frequency shift unit, a PDH frequency stabilization control unit and an ultra-stable cavity; The laser is used to generate narrow line width laser, and the narrow line width laser is input into the frequency shift unit; the frequency shift unit includes a first electro-optic modulator EOM1, a second electro-optic modulator EOM2, a first acousto-optic modulator AOM1 and a second acousto-optic modulator AOM2; The narrow linewidth laser is divided into two paths after being modulated by the first acousto-optic modulator AOM1, the first path of laser is output as an optical signal, and the second path of laser is processed by the second acousto-optic modulator AOM2, the first electro-optic modulator EOM1 and the second electro-optic modulator EOM2; The frequency shift unit is used to input the processed second laser into the ultra-stable cavity, the processed second laser resonates in the ultra-stable cavity, and an error signal is generated in the optical coupling control part according to the resonance result; The PDH frequency stabilization control unit is used to control the laser and the first acousto-optic modulator AOM1 to compensate the frequency by detecting the error signal until the output frequency of the laser is locked on the resonance frequency of the ultra-stable optical cavity.

2. The ultra-stable laser tuning system according to claim 1, characterized in that: The frequency shift unit is specifically used to generate an adjustable frequency sideband using the first electro-optical modulator EOM1, and the adjustable frequency sideband is used for frequency tuning to achieve wide range frequency tuning; The AOM2 is used to adjust the frequency of the second laser to achieve high-precision tuning of the laser.

3. The ultra-stable laser tuning system according to claim 1, characterized in that: The frequency shift unit is also used for: Scanning the frequency of the laser, and selecting a target frequency point in the transmission signal displayed on the photodetector according to the output frequency; Determining the polarity of the frequency shift according to the target frequency point; A positive frequency shift or a negative frequency shift operation is performed according to the polarity of the frequency shift.

4. The ultra-stable laser tuning system according to claim 3, characterized in that: The system also includes a control module for performing decomposition according to the tuning amount of the frequency after determining the polarity of the frequency shift; The frequency shift unit is specifically used to change the modulation frequency of the EOM1 based on the decomposed tuning amount to achieve wide-range tuning and change the modulation frequency of the AOM2 to achieve high-precision tuning.

5. The ultra-stable laser tuning system according to claim 4, characterized in that: The frequency shift unit is specifically used to change the modulation frequency of the EOM1 by using a high-frequency DDS frequency synthesizer to achieve a wide range frequency tuning of the ultra-stable laser; The modulation frequency of the AOM2 is changed by a low-frequency DDS frequency synthesizer to achieve high-precision frequency tuning of the ultra-stable laser.

6. The ultra-stable laser tuning system according to claim 5, characterized in that: The system also includes a frequency display and control unit for displaying the output frequency of the ultra-stable laser tuning system in real time and receiving external instructions to accurately control the modulation frequencies of the EOM1 and the AOM2 by adjusting the frequency control register of the DDS, thereby achieving wide-range and accurate tuning of the ultra-stable laser frequency.

7. An ultra-stable laser tuning method, characterized in that: The method comprises: Generate narrow linewidth laser, and input the narrow linewidth laser into a frequency shift unit, wherein the frequency shift unit includes a first electro-optic modulator EOM1, a second electro-optic modulator EOM2, a first acousto-optic modulator AOM1, and a second acousto-optic modulator AOM2; The narrow linewidth laser is divided into two paths after being modulated by the first acousto-optic modulator AOM1, the first path of laser is output as an optical signal, and the second path of laser is processed by the second acousto-optic modulator AOM2, the first electro-optic modulator EOM1 and the second electro-optic modulator EOM2; Inputting the processed second laser into an ultrastable cavity, wherein the processed second laser resonates with the ultrastable cavity in the ultrastable cavity, and generating an error signal in the optical coupling control part according to the resonance result; The error signal is detected, and the laser and the first acousto-optic modulator AOM1 are controlled to compensate the frequency until the output frequency of the laser is locked on the resonance frequency of the ultra-stable optical cavity.

8. The method according to claim 7, characterized in that Before inputting the processed second laser beam into the ultrastable cavity, the method further comprises: Scanning the frequency of the laser, and selecting a target frequency point in the transmission signal displayed on the photodetector according to the output frequency; Determining the polarity of the frequency shift according to the target frequency point; A positive frequency shift or a negative frequency shift operation is performed according to the polarity of the frequency shift.

9. The method according to claim 8, characterized in that After determining the polarity of the frequency shift, the method further includes: Decomposed according to the amount of tuning of the frequency; Based on the decomposed tuning amount, the modulation frequency of the EOM1 is changed to achieve wide-range tuning, and the modulation frequency of the AOM2 is changed to achieve high-precision tuning.

10. The method according to claim 9, characterized in that The method of changing the modulation frequency of the EOM1 based on the decomposed tuning amount to achieve wide-range tuning and changing the modulation frequency of the AOM2 to achieve high-precision tuning includes: Using a high-frequency DDS frequency synthesizer to change the modulation frequency of the EOM1 to achieve a wide range of frequency tuning of the ultra-stable laser; A low-frequency DDS frequency synthesizer is used to change the modulation frequency of the AOM2 to achieve high-precision frequency tuning of the ultra-stable laser.

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