A laser remote frequency stabilization device based on shared variables

Abstract

The application discloses a kind of laser remote frequency stabilization device based on shared variable, it is related to laser frequency stabilization technical field.The structure of the present application is: laser (1), optical fiber (2) is connected before and after, optical fiber (2) and frequency reference light (3) are connected with laser beam combiner (4) respectively, laser beam combiner (4), electric detector (5), frequency counter (6), data publishing end (7), network (8), data receiving end (9) and laser (1) are sequentially connected.Compared with the similar frequency stabilization device of prior art, the present application can realize long-distance laser frequency stabilization, and has good transmission performance, low cost, high scalability, and can be widely used in laser frequency stabilization technical field.

Description

Technical Field

[0001] This invention relates to the field of laser frequency stabilization technology, specifically to a laser remote frequency stabilization device based on shared variables, which can achieve efficient sharing of high-precision laser frequency references and can be used for laser precision spectral measurement. Background Technology

[0002] Lasers, due to their excellent monochromaticity, have important applications in many fields. Semiconductor lasers, in particular, typically have linewidths of only tens of kHz, but their center frequency can vary by tens of MHz or even tens of GHz per hour during free operation, significantly impacting their accuracy. Laser frequency stabilization increases the stability of the laser's center frequency and also narrows the laser linewidth, thereby greatly improving the laser's performance. In laser frequency stabilization technology, the frequency reference used to lock the laser frequency plays a crucial role. After stabilization, the laser center frequency changes with the frequency reference source. Considering that servo control introduces some instability, the frequency reference source provides an upper limit to the achievable stability of the laser center frequency.

[0003] Currently, there are three main types of frequency references used for laser frequency stabilization: The first type uses the central frequency of atomic or molecular transitions as the frequency reference. Under shielded external field influences, this frequency reference remains unchanged, and its linewidth is the linewidth of the transition energy level. The second type uses optical etalons as the frequency reference, represented by optical cavities and wavelength meters. The linewidth of an optical cavity depends on its fineness and free spectral path. Wavelength meters perform relative measurements, and their measurement accuracy is more easily affected by the reference standard; they are also called calibration sources. Because this type of reference is affected by ambient temperature, the laser locked to this type of reference will drift with the drift of the optical cavity or wavelength meter. The third type of frequency reference is an optical comb. An optical comb is a tool that converts microwave frequency standards into optical frequency standards, and its frequency accuracy can be referenced to a microwave clock reference. Among these three types of frequency references, using the atomic and molecular transition center frequency or an optical cavity as a frequency reference means that a single transition center frequency or an optical cavity can only provide a frequency reference for one optical frequency. Therefore, a single device does not have the ability to be shared. In contrast, high-precision wavelength meters and optical combs are more expensive and can provide frequency references for lasers with wavelength ranges up to hundreds of nanometers, thus having higher sharing value.

[0004] Traditional reference frequency sharing methods involve simultaneously deploying an optical fiber and a data line. The laser light to be stabilized is transmitted through the fiber to the location of the frequency reference. Because the laser and the reference light have similar frequencies, their combined beam is detected by a photodetector. The photodetector detects the frequency difference between the two beams, known as the beat frequency signal. This beat frequency signal is transmitted back to the laser via the data line, ensuring this frequency difference remains constant, thus stabilizing the laser frequency. Unlike short-range frequency stabilization systems, the beat frequency signal attenuates over long distances, and the attenuation varies at different frequencies. While some signal processing can improve long-distance transmission performance, it doesn't change the inherent attenuation characteristic with distance. Therefore, a high strength of the original beat frequency signal is still required.

[0005] To compensate for the attenuation problem of beat frequency signals as radio frequency signals, digital signal transmission is an excellent solution. A program written in C, Python, or LabVIEW on the computer at the frequency reference location publishes the beat frequency as a shared variable. This variable is transmitted over a network, allowing the computer at the laser location to directly use it. This method of transmitting digital signals over a network has strong anti-interference and anti-attenuation properties. The transmission rate depends only on the data type definition of the shared variable and does not change with the magnitude of the beat frequency. Using the beat frequency as a shared variable, the size of the variable is only a few tens of bits, resulting in fast transmission speed. Publishing shared variables is simple, low-cost, and allows for the simultaneous publication of multiple network variables, offering excellent scalability. Therefore, it is very suitable for long-distance sharing of frequency references in laser frequency stabilization, significantly reducing costs.

[0006] In summary, by publishing shared variables and transmitting signals over a network, the laser frequency can be locked to a distant frequency reference. This invention does not require high strength of the original beat frequency signal, and the solution is simple, low-cost, and highly scalable. It achieves long-distance laser frequency stabilization through the sharing of laser frequency references, making the sharing of laser frequency references more convenient. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem of transmitting beat frequency signals for frequency stabilization in long-distance laser frequency stabilization, and to provide a laser remote frequency stabilization device based on shared variables.

[0008] The objective of this invention is achieved as follows:

[0009] The system includes a laser, optical fiber, frequency reference beam, laser beam combiner, photodetector, frequency counter, data transmitter, network, and data receiver. This device solves the problems of signal attenuation and environmental interference when transmitting beat signals over long distances. It can be used to lock the laser frequency to a long-distance frequency reference, greatly increasing the sharing range of high-precision frequency references and can be widely used in the field of laser frequency stabilization technology.

[0010] Specifically:

[0011] This device includes a laser, optical fiber, frequency reference light, laser beam combiner, photodetector, frequency counter, data transmitter, network, and data receiver.

[0012] The connection relationship is:

[0013] The laser and optical fiber are connected front and back. The optical fiber and the frequency reference light are respectively connected to the laser beam combiner. The laser beam combiner, the electrical detector, the frequency counter, the data transmitter, the network, the data receiver and the laser 1 are connected in sequence.

[0014] The laser emitted from the laser is coupled into the optical fiber and transmitted remotely. After passing through a laser beam combiner with the frequency reference light, they are detected together by a photodetector. The photodetector signal is transmitted to a frequency counter, which measures and obtains the frequency value of the beat frequency signal. The data publishing end obtains this value and publishes it as a shared variable. It is then transmitted to the data receiving end via the network, generating a feedback signal that is transmitted to the laser, thus locking the laser frequency to the frequency reference light.

[0015] Compared with existing similar frequency stabilization devices, the present invention has the following advantages and positive effects:

[0016] It can achieve long-distance laser frequency stabilization, with good transmission performance, low cost, and high scalability, and can be widely used in the field of laser frequency stabilization technology. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention, in which:

[0018] 1—Laser;

[0019] 2—Fiber optic cable;

[0020] 3—Frequency reference light;

[0021] 4—Laser beam combiner;

[0022] 5—Photodetector;

[0023] 6—Frequency Counter

[0024] 7—Data publishing terminal;

[0025] 8—Network;

[0026] 9—Data receiving end. Detailed Implementation

[0027] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to specific implementation examples. It should be understood that the specific implementation examples described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0028] I. Structure of a Laser Remote Frequency Stabilization Device Based on Shared Variables

[0029] 1. Overall

[0030] like Figure 1 This device includes a laser 1, an optical fiber 2, a frequency reference beam 3, a laser beam combiner 4, a photodetector 5, a frequency counter 6, a data transmitter 7, a network 8, and a data receiver 9.

[0031] The connection relationship is:

[0032] Laser 1 and fiber 2 are connected front and back. Fiber 2 and frequency reference light 3 are respectively connected to laser beam combiner 4. Laser beam combiner 4, electrical detector 5, frequency counter 6, data transmitter 7, network 8, data receiver 9 and laser 1 are connected in sequence.

[0033] Laser 1 emits laser light that couples into fiber 2. After remote transmission, the laser light and frequency reference light 3 pass through laser beam combiner 4 and are detected by photodetector 5. The signal from photodetector 5 is transmitted to frequency counter 6. After measurement, the frequency value of the beat frequency signal is obtained. Data publishing terminal 7 obtains the value and publishes it as a shared variable. It is transmitted to data receiving terminal 9 through network 8, generating a feedback signal that is transmitted to laser 1, thereby locking the laser frequency to frequency reference light 3.

[0034] Working mechanism:

[0035] The frequency of the laser emitted by laser 1 is f l (t) The laser is coupled into fiber 2, and after long-distance transmission, it coincides with the frequency reference light 3, where the frequency of the frequency reference light 3 is f. c The reference light frequency can be assumed to remain constant over time, and f l (t) and f c The two laser beams are similar in size. After they overlap, they are detected together by photodetector 5. The frequency of the superimposed laser beams after overlap can be approximated by the combined frequency f. c +f l Partial sum and difference frequencies |f c -f lThe difference frequency is represented by the superposition of two beams. Since the combined frequency is relatively large, it is the optical frequency; the bandwidth of photodetector 5 cannot cover the optical frequency, so photodetector 5 can only detect the difference frequency, i.e., the beat frequency signal of the two beams, with a frequency of f. b =|f c -f l |A sinusoidal signal. By counting the frequency of the signal from the photodetector 5 using the frequency counter 6, f can be obtained. b The value of f is constantly changing and unstable when the laser 1 frequency is not locked. The frequency counter 6 transmits this value to the data publishing terminal 7, typically a computer or other instrument with computer capabilities. This value is published as a shared variable using Python, C, or LabVIEW, and then transmitted back to the data receiving terminal 9 at the location of laser 1 via network 8. The shared variable, f, is then accessed in real-time by a program consistent with the published shared variable, such as Python, C, or LabVIEW. b Since the network transmits 8 bytes of data, the received value is not affected by signal attenuation during transmission, and the delay is very small, on the order of microseconds. The data receiver 9, receiving the shared variable, converts the feedback signal into a voltage and transmits it to the laser 1 using proportional-integral-derivative (PID) control, causing f to... b The frequency f tends to stabilize over time, thus achieving the desired laser frequency. l The stability of (t).

[0036] 2. Functional components

[0037] 1) Laser 1

[0038] It is a commonly used instrument used to output laser light.

[0039] 2) Fiber optic 2

[0040] It is a commonly used optical component and an effective light transmission tool.

[0041] 3) Frequency reference light 3

[0042] Light that can be used as a frequency standard, such as optical combs and lasers that are already locked to a frequency standard.

[0043] 4) Laser beam combiner

[0044] It is a commonly used optical component used to combine different laser beam paths, such as: semi-transparent and semi-reflective mirrors, polarizing beam splitters, beam splitters, etc.

[0045] 5) Photodetector 5

[0046] It is a commonly used component for laser power measurement. When detecting two laser beams with different frequencies, if the difference frequency is within the detector's measurement bandwidth, the beat frequency signal of the two laser beams can be measured.

[0047] 6) Frequency counter 6

[0048] It is a commonly used component, and is an electronic measuring instrument specifically designed to measure the frequency of the signal being measured.

[0049] 7) Data publishing terminal 7

[0050] It is a control terminal that can acquire signals and publish shared variables through Python, C language or LabVIEW, etc., and is mostly a computer or a PXI chassis with integrated computer functions.

[0051] 8) Network 8

[0052] It is a commonly used component for information transmission, reception, and sharing platforms, which can be wired or wireless networks.

[0053] 9) Data receiving end 9

[0054] It is a control terminal that can receive network information and output control signals based on the received information. The receiving method is determined by the publishing method, and it is mostly a computer or a PXI chassis that integrates computer functions. II. Specific Implementation Methods

[0056] In practical implementation, laser 1 is a continuous laser, and the frequency reference light 5 is an optical comb. Laser 1 needs to maintain a stable frequency within the optical comb's spectral range, and the laser 1 and the optical comb should be located at a considerable distance. The laser output from laser 1 is coupled into optical fiber 2. After long-distance transmission through optical fiber 2, the laser output from laser 1 is introduced to the location of the optical comb. The output light from the optical comb and the output light from the optical fiber pass through laser combiner 4 to make the optical paths coincide. The adjustment device required for coinciding is a common technique for optical path adjustment. After coinciding, the laser is detected by photodetector 5. The detection bandwidth of photodetector 5 is greater than half the repetition frequency of the optical comb, ensuring that the beat frequency signal of the two beams is detected. The beat frequency signal is measured by frequency counter 6 to obtain the beat frequency, which is then transmitted to data publishing terminal 7. Here, a computer with software such as C, Python, or LabVIEW installed can be used as the data publishing terminal. The beat frequency value is set as a shared variable, and the data publishing terminal 8 and data receiving terminal 9 are connected via network 9. Here, a computer with software installed to publish shared variables acts as data receiver 9. It calls the shared variables, generates a feedback signal through digital-to-analog conversion, and inputs it to laser 1 to keep the beat frequency value unchanged. This locks the output laser frequency of laser 1 to the optical comb, thereby stabilizing the laser frequency.

[0057] Those skilled in the art to which this invention pertains may make necessary modifications or substitutions to the specific embodiments described, such as using different laser frequency references, unlisted laser beam combining methods, and software for publishing shared variables, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A laser remote frequency stabilization device based on shared variables, characterized in that: It includes a laser (1), an optical fiber (2), a frequency reference beam (3), a laser beam combiner (4), a photodetector (5), a frequency counter (6), a data transmitter (7), a network (8), and a data receiver (9); The connection relationship is: The laser (1) and the optical fiber (2) are connected front and back. The optical fiber (2) and the frequency reference light (3) are connected to the laser beam combiner (4) respectively. The laser beam combiner (4), the electrical detector (5), the frequency counter (6), the data transmitter (7), the network (8), the data receiver (9) and the laser (1) are connected in sequence. The laser emitted from the laser (1) is coupled into the optical fiber (2). After being transmitted remotely, it passes through the laser beam combiner (4) along with the frequency reference light (3) and is detected by the photodetector (5). The photodetector (5) transmits the signal to the frequency counter (6). After measurement, the frequency value of the beat frequency signal is obtained. The data publishing end (7) obtains the value and publishes it as a shared variable. It is transmitted to the data receiving end (9) through the network (8) and generates a feedback signal that is transmitted to the laser (1), thereby locking the laser frequency to the frequency reference light (3).

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