CN118783237A - Ultra-stable laser tuning system and laser tuning method - Google Patents
Ultra-stable laser tuning system and laser tuning method Download PDFInfo
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Abstract
The application provides an ultra-stable laser tuning system and a laser tuning method, which relate to the technical field of ultra-stable laser, the system integrates a laser, a frequency shifting unit, a PDH frequency stabilizing control unit and an ultra-stable cavity, and can realize large-range high-precision tuning of ultra-stable laser. Specifically, in the application, an acousto-optic modulator and an electro-optic modulator are additionally introduced when the ultra-stable laser tuning is performed, extra locking noise and ring outward drift movement are not added, so that the performance index of the ultra-stable laser is ensured to be maintained.
Description
Technical Field
The application relates to the technical field of ultra-stable laser, in particular to an ultra-stable laser tuning system and a laser tuning method.
Background
In the fields of precision science and high-end technology application, an ultra-stable laser plays a vital role. Such lasers are known for their excellent frequency stability and accuracy, and are key technologies for achieving laser precision atomic regulation, precision measurement, remote quantum communication, and light Zhong Cifu applications. These applications place extremely high demands on the tunable range and accuracy of laser frequencies, requiring a wide range of frequency tuning on the order of hundred megahertz (MHz) and even gigahertz (GHz), and at the same time achieving high accuracy tuning on the order of hertz (Hz), millihertz (MHz) and even micro hertz (μhz). Since the frequency stability of an ultrastable laser is mainly dependent on its cavity length, the design of the cavity generally needs to operate at the inflection point temperature to obtain the best temperature characteristics. Such a temperature control strategy, while helping to improve frequency stability, also limits the cavity length adjustable laser frequency range, i.e., typically on the order of MHz. Therefore, the ultra-stable laser needs to be frequency-tuned in a wide range and with high accuracy.
In the prior art, in order to realize large-range and high-precision tuning of the ultra-stable laser frequency, an additional laser is introduced, and the frequency of the additional laser is locked to the ultra-stable laser through a frequency deviation locking technology. According to the method, a laser frequency locking control system is additionally arranged, a narrow linewidth laser is used, the system structure is complex, the cost is high, and additional noise and extra-loop drift are introduced when the additional laser frequency is locked to the ultra-stable laser, so that the locking noise and the extra-loop drift of the system are increased, and the performance index of the ultra-stable laser is deteriorated.
Disclosure of Invention
In view of the above problems, the present application provides an ultrastable laser tuning system and a laser modulation method, including:
In a first aspect, the present application provides an ultrastable laser tuning system comprising: the device comprises a laser, a frequency shifting unit, a PDH frequency stabilization control unit and an ultra-stable cavity;
The laser is used for generating narrow linewidth laser and inputting the narrow linewidth laser into the frequency shifting unit; the frequency shifting unit comprises a first electro-optical modulator EOM1, a second electro-optical 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 then is 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 EOM 2;
the frequency shifting unit is used for inputting 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 a resonance result;
the PDH frequency stabilization control unit is used for controlling 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.
Optionally, the frequency shifting unit is specifically configured to generate an adjustable frequency sideband by using the first electro-optical modulator EOM1, where the adjustable frequency sideband is used for frequency tuning, so as to implement wide-range frequency tuning;
And the AOM2 is used for adjusting the frequency of the second path of laser so as to realize high-precision tuning of the laser.
Optionally, the frequency shift unit is further configured to:
Scanning the frequency of the laser, and selecting a target frequency point in a transmission signal displayed on the photoelectric detector according to the output frequency;
determining the frequency shift polarity according to the target frequency point;
And performing positive frequency shift or negative frequency shift operation according to the frequency shift polarity.
Optionally, the system further comprises a control module, which is used for decomposing according to the tuning amount of the frequency after judging the frequency shift polarity;
The frequency shift unit is specifically configured to change the modulation frequency of the EOM1 based on the decomposed tuning amount to implement large-range tuning and change the modulation frequency of the AOM2 to implement high-precision tuning.
Optionally, the frequency shift unit is specifically configured to change the modulation frequency of the EOM1 by using a high-frequency DDS frequency synthesizer to implement 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, so that high-precision frequency tuning of the ultra-stable laser is realized.
Optionally, the system further includes a frequency display and control unit, configured to display an output frequency of the ultrastable laser tuning system in real time, and receive an external instruction, and accurately control modulation frequencies of the EOM1 and the AOM2 by adjusting a frequency control register of the DDS, so as to implement large-scale accurate tuning of the ultrastable laser frequency.
In a second aspect, the present application provides an ultrastable laser tuning method, including:
generating narrow-line-width laser, and inputting the narrow-line-width laser into a frequency shifting unit, wherein the frequency shifting unit comprises a first electro-optical modulator EOM1, a second electro-optical 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 then is 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 EOM 2;
Inputting the processed second path of laser into an ultra-stable cavity, wherein the processed second path of laser resonates with the ultra-stable cavity in the ultra-stable cavity, and an error signal is generated in an optical coupling control part according to a resonance result;
Detecting the error signal, and controlling the laser and the first acousto-optic modulator AOM1 to compensate frequency; until the output frequency of the laser is locked to the resonant frequency of the ultra-stable optical cavity.
Optionally, before the second processed laser is input into the ultra-stable cavity, the method further includes:
Scanning the frequency of the laser, and selecting a target frequency point in a transmission signal displayed on the photoelectric detector according to the output frequency;
determining the frequency shift polarity according to the target frequency point;
And performing positive frequency shift or negative frequency shift operation according to the frequency shift polarity.
Optionally, after determining the polarity of the shift frequency, the method further comprises:
decomposing according to the tuning amount of the frequency;
and changing the modulation frequency of the EOM1 based on the decomposed tuning amount to realize large-range tuning and changing the modulation frequency of the AOM2 to realize high-precision tuning.
Optionally, the 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:
changing the modulation frequency of the EOM1 by using a high-frequency DDS frequency synthesizer to realize the wide-range frequency tuning of the ultra-stable laser;
and changing the modulation frequency of the AOM2 by using a low-frequency DDS frequency synthesizer to realize high-precision frequency tuning of the ultra-stable laser.
The application provides an ultra-stable laser tuning system. The system comprises a laser, a frequency shifting unit, a PDH frequency stabilizing control unit and an ultra-stable cavity, wherein the laser is used for generating narrow linewidth laser and inputting the narrow linewidth laser into the frequency shifting unit; the frequency shifting unit comprises a first electro-optical modulator EOM1, a second electro-optical 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 then is 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 EOM 2; the frequency shifting unit is used for inputting 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 a resonance result; the PDH frequency stabilization control unit is used for controlling 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. By adopting the system scheme, the high-efficiency and accurate laser frequency stabilization control system is realized, and the system combines a laser, a frequency shifting unit, a PDH frequency stabilization control unit and an 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: an acousto-optic modulator and an electro-optic modulator are additionally introduced during the ultra-stable laser tuning, extra locking noise and ring outward drift movement are not added, so that the performance index of the ultra-stable laser is ensured to be maintained.
Drawings
In order to more clearly illustrate this embodiment or the technical solutions of the prior art, the drawings that are required for the description of the embodiment or the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of an ultrastable laser tuning system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a transmission signal according to an embodiment of the present application;
FIG. 3 is a schematic diagram of another ultrastable laser tuning system according to an embodiment of the present application;
Fig. 4 is a flowchart of an ultrastable laser tuning method according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Fig. 1 is a schematic structural diagram of an ultrastable laser tuning system according to an embodiment of the present application. Referring to fig. 1, an ultrastable laser tuning system provided in an embodiment of the present application may include: the device comprises a laser 10, a frequency shifting unit 11, a PDH frequency stabilization control unit 12 and an ultra-stable cavity 13.
Wherein the laser 10 is a narrow linewidth laser, which is a laser capable of producing very narrow linewidth laser light. The spectral linewidth of a narrow linewidth laser is narrower than that of a conventional wide linewidth laser, and thus higher time resolution and frequency resolution can be achieved. The narrow linewidth laser provided in the embodiment of the application is specifically used for outputting laser with frequency f, and after the laser is processed by the frequency shift unit 11, two paths of laser are obtained, wherein the first path of laser is used as final output light of the ultra-stable laser. The second laser is used as reference light for ultra-stable laser locking.
The frequency shift unit 11 includes a first electro-optical modulator EOM1, a second electro-optical modulator EOM2, a first acousto-optic modulator AOM1, and a second acousto-optic modulator AOM2, and is configured to process the second path of laser, and input the processed second path of laser to the PDH frequency stabilization control unit. After generating the narrow linewidth laser, the narrow linewidth laser is input into the frequency shift unit 11, a first electro-optical modulator EOM1 in the frequency shift unit 11 processes the laser, then outputs two paths of laser through an optical fiber beam splitter, wherein the first path is used as final output light of the ultra-stable laser, and the second path is used as reference light locked by the ultra-stable laser. The AOM1 may be 1550 nm AOM1, i.e. the operating wavelength is 1550 nm, and further the optical splitter is 1550 nm.
After the first path of laser and the second path of laser are obtained, the second path of laser is modulated in the frequency shift unit 11 through the AOM 2. An acousto-optic modulator can modulate light by generating periodically varying refractive indices in a medium by ultrasonic waves. The specific modulation parameters (e.g., modulation frequency, modulation depth, etc.) will depend on the application requirements. The second light is then re-modulated by EOM 1. Electro-optic modulators modulate the phase, intensity, or polarization state of light by changing the refractive index of a material. In particular, the first electro-optic modulator EOM1 is configured to generate a fixed frequency sideband. This is typically accomplished by applying a Radio Frequency (RF) signal to EOM1 that causes symmetric sidebands to appear in the spectrum of the laser. The spacing 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 are also set according to the application requirements. And the laser modulated by the EOM1 enters the EOM2 to carry out radio frequency electro-optic phase modulation. This modulation scheme allows for high frequency (rf range) phase modulation of optical signals, and is commonly used in the fields of optical communications, sensing, quantum information, and the like. The phase of the light can be precisely controlled by rf electro-optic phase modulation, which is critical for experiments or applications requiring highly accurate phase control. The second electro-optic modulator EOM2 is in particular used for generating an adjustable frequency sideband for frequency tuning. Like EOM1, EOM2 also produces sidebands by applying RF signals, but here the RF signal frequency is adjustable, allowing fine control of the sideband frequency.
By combining EOM1 or AOM2 in the frequency shifting unit, accurate control and adjustment of laser frequency can be realized, and sidebands for PDH frequency locking can be generated.
And the second path of laser processed by the frequency shifting unit enters the ultra-stable cavity 13 through a space optical path of the optical coupling control part, the processed second path of laser resonates in the ultra-stable cavity, an error signal is generated in the optical coupling control part according to a resonance result, and the PDH frequency stabilizing control unit is used for controlling 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.
After the second path of laser processed by the frequency shifting unit enters the PDH frequency stabilization control unit, frequency stabilization processing is needed by utilizing a PDH frequency stabilization technology. And performing frequency error detection on the processed second path of laser and the ultra-stable cavity to obtain detuning information, and tuning the laser frequency generated by the laser based on the detuning information until the PDH frequency stabilization control unit locks the output frequency of the laser on the resonance frequency of the ultra-stable optical cavity.
The following describes a procedure of performing frequency stabilization processing in the PDH frequency stabilization control unit in connection with a specific embodiment.
Firstly, scanning a second path of laser processed by the adjusting unit, and checking a signal of transmitted light through a photoelectric detector in the scanning process, wherein 3 frequency points can be observed on the photoelectric detector, as shown in fig. 2, fig. 2 is a schematic diagram of the transmitted signal provided by the embodiment of the application, and symmetrical sidebands can be generated on two sides of the original laser frequency due to the modulation effect of EOM1 or AOM 2. The difference between the frequency of these sidebands and the original laser frequency is equal to the modulation frequency of the modulator. Wherein the 1 st frequency point is the result of the superposition of the original laser frequency and one 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. forward shift frequency); the 2 nd frequency point is the original laser frequency without modulation. However, in PDH frequency stabilization control, this frequency point is not generally selected directly, since it does not contain information generated by modulation, which is detrimental to frequency stabilization and locking; the 3 rd frequency bin is the result of the superposition of the original laser frequency with another sideband frequency generated by EOM or AOM modulation. In contrast to the 1 st frequency point, if this frequency point is selected, the output laser frequency will be slightly lower (i.e. negative shift frequency) than the resonance frequency of the bistable cavity due to the subtraction of the modulation frequency.
When the 1 st frequency point (forward shift frequency) is selected, the output frequency (f out) is the resonant frequency of the ultra-stable cavity (f fp) minus the modulation frequency of AOM2 (f s1) plus the modulation frequency of EOM1 (f s2). I.e., f out=ffp-fs1+fs2;
When the 3 rd frequency point (negative shift frequency) is selected, the output frequency (f out) is the resonant frequency of the ultra-stable cavity (f fp) minus the modulation frequency of AOM2 (f s1) and minus the modulation frequency of EOM1 (f s2). I.e. f out=ffp-fs1-fs2.
After the frequency point is selected, the laser signal modulated by EOM2 is led into the ultra-stable cavity through a space optical path. The ultra-stable cavity acts as a high precision optical resonator that enhances and feeds back the input laser signal to produce a reflected optical signal. These reflected optical signals contain important information of the frequency mismatch between the laser and the ultra-stable cavity. The photodetectors are responsible for capturing these reflected light signals and converting them into electrical signals. Then, frequency detuning information between the laser and the ultra-stable cavity can be extracted from these electrical signals by a phase demodulation technique. After processing, the information forms an error signal which accurately reflects the deviation between the current laser frequency and the ultra-stable cavity resonance frequency. To correct this deviation, the error signal needs to be further processed.
First, high-frequency noise in the error signal can be removed by the low-pass filter, and a low-frequency part of the error signal is reserved, so that more accurate deviation information is obtained. The filtered error signal is then fed into a proportional-integral circuit (PI circuit). The PI circuit generates a control signal according to the magnitude and duration of the error signal, and the magnitude and direction of the 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 piezoceramic or acousto-optic modulator of the laser. The piezoelectric ceramic fine-tunes the output frequency of the laser through a small displacement, while the acousto-optic modulator can realize a larger adjustment by changing the frequency of the optical signal. Under the combined action of the two, the output frequency of the laser gradually approaches to the resonance frequency of the ultra-stable cavity, and finally stable locking of the laser frequency is realized.
Through the feedback control process described above, the output frequency of the narrow linewidth laser is gradually adjusted to coincide 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 realized.
The above-mentioned embodiment of the present application further includes a control module, which is used to implement accurate control of the laser frequency, so that the output frequency of the narrow linewidth laser is gradually adjusted to be consistent with the resonance frequency of the ultra-stable optical cavity.
In particular, in PDH frequency stabilization control systems, it is often necessary to decompose and perform corresponding frequency adjustments according to the polarity of the frequency shift and the amount of tuning required. In the PDH frequency stabilization control system, the polarity of frequency mismatch (i.e., the direction of frequency deviation) between the laser and the ultra-stable cavity needs to be determined by a phase demodulation technique. This is typically achieved by comparing the phase difference between the reflected light signal and the reference signal.
Once the polarity of the shift is determined, this tuning task needs to be resolved according to the amount of tuning required. Typically, a wide range of frequency adjustment is achieved by the EOM, as it can rapidly change the phase or frequency of the optical signal, suitable for fast, wide range tuning. The high-precision tuning is finished by the AOM, so that the AOM can realize accurate control of the frequency of the optical signal and is suitable for fine adjustment. In the application, a part larger than the resolution of the high-frequency DDS frequency synthesizer realizes large-scale tuning by changing the modulation frequency f s2 of the EOM1, and a part smaller than the resolution of the high-frequency DDS frequency synthesizer realizes high-precision tuning by changing the modulation frequency f s1 of the AOM2, as shown in fig. 3, fig. 3 is a schematic structural diagram of another ultra-stable laser tuning system provided by the embodiment of the application, and the ultra-stable laser tuning system further comprises a high-frequency DDS (direct digital frequency synthesizer) frequency synthesizer and a low-frequency DDS frequency synthesizer which are respectively used for changing the modulation frequencies of the EOM and the AOM so as to realize large-scale and high-precision tuning.
Extensive tuning with EOM 1: a high frequency DDS frequency synthesizer is used to change the modulation frequency of EOM1, the modulated frequency being denoted by f s2. The DDS frequency synthesizer is able to quickly generate accurate, stable frequency signals, which is critical to achieving a wide range of tuning of EOM 1. The modulation frequency of the EOM1 can be controlled by adjusting the frequency output of the DDS, so that the laser frequency can be adjusted in a large range.
High precision tuning using AOM 2: the modulation frequency of AOM2 is changed by a low frequency DDS frequency synthesizer. Because the AOM is sensitive to frequency change of the optical signal, accurate control of the modulation frequency of the AOM2 can be realized by using the low-frequency DDS. Thus, the AOM2 can be used to fine tune the laser frequency to achieve high precision frequency stabilization control, and the modulated frequency is denoted by f s1.
The tuning process described above can achieve efficient control of laser frequency by combining the tuning capabilities of the EOM and AOM. The EOM is used for large-range rough adjustment, the AOM is used for high-precision fine adjustment, and the EOM and the AOM are mutually complemented, so that the tuning efficiency of the whole system is improved. The modulation frequencies of the EOM and the AOM are precisely controlled by using the DDS frequency synthesizer, so that the tuning accuracy is ensured. The high-frequency DDS is used for EOM to realize large-scale tuning, the low-frequency DDS is used for AOM to realize high-precision tuning, and the tuning range and the tuning precision can be flexibly adjusted according to the requirement by the tuning strategy of ensuring the frequency stabilization precision of the whole system. Modulation frequencies of the EOM and the AOM can be conveniently adjusted by changing the frequency output of the DDS, so that the laser frequency can be flexibly controlled.
In summary, by combining the tuning capabilities of the EOM and AOM and using the DDS frequency synthesizer to precisely control their modulation frequencies, efficient, precise and flexible control of the laser frequency can be achieved, which is important for PDH frequency stabilization control systems.
The process of tuning the frequency of the ultrastable laser is described below by way of one example. In this example, a low frequency DDS with a system clock of 200MHz is used to drive AOM2 with a frequency control bit number of up to 48 bits, providing a frequency control accuracy of about 0.7 μHz. Assuming that a positive shift of 1.2GHz is to be achieved, a frequency control register of the high frequency DDS is first set according to the target shift amount f shift using the formula f s2=fshift+fs1. In this example, the frequency control register of the high frequency DDS is set to 1533916891 so that the output frequency f s2 of the EOM1 reaches 1249999999.650754Hz. Then, the frequency that the low frequency DDS needs to output is calculated using the formula f s1=fs2-fshift and set to 49999999.650754Hz. Thus, by the synergistic effect of EOM1 and AOM2, frequency tuning with an accuracy better than 1 μhz is achieved.
If a negative shift of 1.2GHz is to be achieved, the above formula can be used for calculation and setting as well. For negative shift, the frequency control register of the high frequency DDS is set using equation f s2=fshift-fs1, resulting in the output frequency f s2 of EOM 1. Then, the frequency that the low frequency DDS needs to output is calculated using formula f s1=fshift-fs2. In this example, the frequency control register of the high frequency DDS is set to 1411203540 to bring the output frequency f s2 of the EOM1 to 1149999999.906868Hz. The output frequency of the low frequency DDS is set to 50000000.093132Hz. By this method, frequency tuning with an accuracy better than 1 μhz is also achieved.
In the above embodiments, it is described how to achieve a wide range and high precision tuning of the ultra-stable laser frequency by combining modulation frequency adjustment of EOM (electro-optical modulator) and AOM (acousto-optic modulator), and using a high frequency DDS and a low frequency DDS frequency synthesizer. However, a complete laser frequency stabilization system requires not only precise coordination of the hardware components, but also a unit that can monitor and flexibly control the components in real time.
For this purpose, a frequency display and control unit is introduced, which plays a crucial role in this system. The main functions of this unit are in two ways: firstly, the output frequency of the ultra-stable laser tuning system can be displayed in real time, and visual frequency state information is provided for operators; and secondly, the device can receive an external instruction, and the modulation frequencies of the EOM1 and the AOM2 are precisely controlled by adjusting a frequency control register of the DDS, so that precise control of the ultra-stable laser frequency is realized.
Specifically, the frequency display and control unit calculates modulation frequencies of the EOM1 and the AOM2 in real time by reading the value of the frequency control register of the DDS, and calculates the output frequency of the ultrastable laser according to the modulation frequencies. It then displays this frequency value on a user interface for reference by the operator. Meanwhile, an operator can also input frequency adjustment instructions through a user interface, and after the instructions are received by the frequency display and control unit, the instructions are converted into corresponding DDS frequency control register values and written into the DDS, so that the accurate adjustment of the EOM1 and AOM2 modulation frequencies is realized.
In this way, the frequency display and control unit not only improves the automation degree 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 according to the needs so as to meet the requirements of different experiments and applications. Meanwhile, the frequency information displayed in real time provides an important reference basis for operators, and helps the operators to better master the running state of the system.
The foregoing embodiments describe an ultrastable laser tuning system, and the present application also provides a corresponding ultrastable laser tuning method for the ultrastable laser tuning system, and the following describes an ultrastable laser tuning method provided by the embodiment of the present application with reference to a specific embodiment, as shown in fig. 4, and fig. 4 is a flowchart of an ultrastable laser tuning method provided by the embodiment of the present application:
S401, generating narrow-line-width laser, and inputting the narrow-line-width laser into a frequency shifting unit, wherein the frequency shifting unit comprises a first electro-optical modulator EOM1, a second electro-optical modulator EOM2, a first acousto-optic modulator AOM1 and a second acousto-optic modulator AOM2;
S402, the narrow linewidth laser is modulated by the first acousto-optic modulator AOM1 and then 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 EOM 2;
S403, inputting the processed second path of laser into an ultra-stable cavity, wherein the processed second path of laser resonates with the ultra-stable cavity in the ultra-stable cavity, and an error signal is generated in an optical coupling control part according to a resonance result;
S404, detecting the error signal, and controlling the laser and the first acousto-optic modulator AOM1 to compensate frequency; until the modulation frequency after the output of the laser is locked at the resonance frequency of the ultra-stable optical cavity.
In an implementation method of the embodiment of the present application, before the second laser after the treatment is input into the ultra-stable cavity, the method further includes:
Scanning the frequency of the laser, and selecting a target frequency point in a transmission signal displayed on the photoelectric detector according to the output frequency;
determining the frequency shift polarity according to the target frequency point;
And performing positive frequency shift or negative frequency shift operation according to the frequency shift polarity.
In an implementation method of the embodiment of the present application, after determining the polarity of the frequency shift, the method further includes:
decomposing according to the tuning amount of the frequency;
and changing the modulation frequency of the EOM1 based on the decomposed tuning amount to realize large-range tuning and changing the modulation frequency of the AOM2 to realize high-precision tuning.
In an implementation method of the embodiment of the present application, the changing the modulation frequency of the EOM1 based on the decomposed tuning amount to implement tuning in a large range and changing the modulation frequency of the AOM2 to implement tuning in high precision includes:
changing the modulation frequency of the EOM1 by using a high-frequency DDS frequency synthesizer to realize the wide-range frequency tuning of the ultra-stable laser;
And changing the modulation frequency of the AOM2 by using a low-frequency DDS frequency synthesizer to realize high-precision frequency tuning of the ultra-stable laser.
The specific implementation process of the ultra-stable laser tuning method is realized based on the ultra-stable laser tuning system in the above embodiment, and the specific implementation process is not described here again.
Compared with the prior art adopting a scheme of adding a laser frequency locking control system, the method and the system for tuning the ultra-stable laser frequency have the following advantages that the effect of realizing large-range high-precision ultra-stable laser tuning is achieved:
1. The high-low frequency DDS drive is adopted, and the frequency tuning of ultra-stable light in a large range, high precision and no dead zone is realized by matching with an acousto-optic modulator and an electro-optic modulator.
2. No extra locking noise and ring outward drift movement are introduced, and the performance index of the ultra-stable laser is ensured not to be deteriorated.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
It should be further noted that, in the present specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for the apparatus and device embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for relevant points. The apparatus and device embodiments described above are merely illustrative, wherein elements illustrated as separate elements may or may not be physically separate, and elements presented as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
The foregoing is only one specific embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present application should be included in the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims (10)
1. An ultra-stable laser tuning system is characterized in that, the ultra-stable laser tuning system comprises: the device comprises a laser, a frequency shifting unit, a PDH frequency stabilization control unit and an ultra-stable cavity;
The laser is used for generating narrow linewidth laser and inputting the narrow linewidth laser into the frequency shifting unit; the frequency shifting unit comprises a first electro-optical modulator EOM1, a second electro-optical 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 then is 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 EOM 2;
the frequency shifting unit is used for inputting 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 a resonance result;
the PDH frequency stabilization control unit is used for controlling 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 of claim 1, wherein the frequency shifting unit is specifically configured to generate an adjustable frequency sideband with the first electro-optic modulator EOM1, the adjustable frequency sideband being configured for frequency tuning to achieve a wide range of frequency tuning;
And the AOM2 is used for adjusting the frequency of the second path of laser so as to realize high-precision tuning of the laser.
3. The ultra-stable laser tuning system of claim 1, wherein the frequency shifting unit is further configured to:
Scanning the frequency of the laser, and selecting a target frequency point in a transmission signal displayed on the photoelectric detector according to the output frequency;
determining the frequency shift polarity according to the target frequency point;
And performing positive frequency shift or negative frequency shift operation according to the frequency shift polarity.
4. The ultra-stable laser tuning system according to claim 3, further comprising a control module for decomposing according to the tuning amount of the frequency after judging the polarity of the frequency shift;
The frequency shift unit is specifically configured to change the modulation frequency of the EOM1 based on the decomposed tuning amount to implement large-range tuning and change the modulation frequency of the AOM2 to implement high-precision tuning.
5. The ultra-stable laser tuning system of claim 4, wherein the frequency shifting unit is specifically configured 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, so that high-precision frequency tuning of the ultra-stable laser is realized.
6. The ultra-stable laser tuning system according to any one of claims 1-5, further comprising 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, and precisely controlling the modulation frequencies of the EOM1 and the AOM2 by adjusting a frequency control register of the DDS, thereby realizing a wide-range precise tuning of the ultra-stable laser frequency.
7. A method of ultra-stable laser tuning, the method comprising:
generating narrow-line-width laser, and inputting the narrow-line-width laser into a frequency shifting unit, wherein the frequency shifting unit comprises a first electro-optical modulator EOM1, a second electro-optical 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 then is 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 EOM 2;
Inputting the processed second path of laser into an ultra-stable cavity, wherein the processed second path of laser resonates with the ultra-stable cavity in the ultra-stable cavity, and an error signal is generated in an optical coupling control part according to a resonance result;
Detecting the error signal, and controlling a laser and the first acousto-optic modulator AOM1 to compensate frequency; until the output frequency of the laser is locked to the resonant frequency of the ultra-stable optical cavity.
8. The method of claim 7, wherein before the introducing the processed second laser light into the ultra stable cavity, the method further comprises:
Scanning the frequency of the laser, and selecting a target frequency point in a transmission signal displayed on the photoelectric detector according to the output frequency;
determining the frequency shift polarity according to the target frequency point;
And performing positive frequency shift or negative frequency shift operation according to the frequency shift polarity.
9. The method of claim 8, wherein after determining the polarity of the shift, the method further comprises:
decomposing according to the tuning amount of the frequency;
and changing the modulation frequency of the EOM1 based on the decomposed tuning amount to realize large-range tuning and changing the modulation frequency of the AOM2 to realize high-precision tuning.
10. The method of claim 9, wherein the changing the modulation frequency of the EOM1 based on the decomposed tuning amount enables wide-range tuning and changing the modulation frequency of the AOM2 enables high-precision tuning comprises:
changing the modulation frequency of the EOM1 by using a high-frequency DDS frequency synthesizer to realize the wide-range frequency tuning of the ultra-stable laser;
and changing the modulation frequency of the AOM2 by using a low-frequency DDS frequency synthesizer to realize high-precision frequency tuning of the ultra-stable laser.
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| CN114865445A (en) * | 2021-02-04 | 2022-08-05 | 济南量子技术研究院 | Frequency-adjustable ultrastable laser generation method based on modulation sideband frequency locking and laser system |
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| US20240235156A1 (en) * | 2023-01-09 | 2024-07-11 | Government Of The United States Of America, As Represented By The Secretary Of Commerce | Ultra-stable integrated laser on silicon |
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| US20240235156A1 (en) * | 2023-01-09 | 2024-07-11 | Government Of The United States Of America, As Represented By The Secretary Of Commerce | Ultra-stable integrated laser on silicon |
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