Pulse width monitoring system and method based on frequency multiplication

Abstract

According to the pulse width monitoring system and method based on frequency multiplication, pulse width is monitored through frequency multiplication, high time resolution and sensitivity are achieved, even weak pulse signals can be detected through appropriate signal amplification, the measurement process is achieved through a small amount of laser beam splitting, a main laser beam cannot be affected, and the measurement accuracy is high. The laser pulse width can be monitored in real time, and the running state of the laser can be fed back in real time.

Description

Technical Field

[0001] The present invention relates to the field of laser monitoring, and particularly to a pulse width monitoring system and method based on frequency doubling. Background Art

[0002] With the rapid development of laser technology, laser pulse width monitoring plays an important role in many high-precision fields, such as laser physics, communication, medicine, military, and scientific research. Laser pulse width monitoring is a technology for analyzing the output characteristics of a laser by measuring the pulse width of a laser signal. The width of a laser pulse has a direct impact on the performance, stability, and application effect of a laser system. Therefore, accurately monitoring the laser pulse width is crucial for the optimization and application of laser technology.

[0003] Traditional laser pulse width monitoring methods usually rely on the measurement techniques of photodetectors or fast oscilloscopes. When facing extremely short time scales (such as picosecond or femtosecond pulses), the measurement accuracy and time delay are often limited. High-precision measurement equipment has high requirements for hardware, and the cost of the equipment is expensive. And when it is required that the equipment can capture laser signals in real time and accurately measure the pulse width, traditional systems often face difficulties in capturing rapidly changing signals. Especially when the pulse frequency is very high, it is difficult to guarantee the accuracy of real-time monitoring. Summary of the Invention

[0004] The present invention provides a pulse width monitoring system and method based on frequency doubling, which can solve the problems of large space, complex setup, and difficult adjustment caused by directly monitoring the pulse width using an autocorrelator in the prior art.

[0005] A pulse width monitoring system based on frequency doubling includes:

[0006] A laser;

[0007] A pulse width adjustment module for changing the pulse width of the laser emitted by the laser and detecting the changed laser pulse width;

[0008] A power attenuation module arranged behind the laser along the laser incident direction for changing the polarization state of the laser;

[0009] A second harmonic generation module arranged behind the power attenuation module along the laser incident direction for performing frequency doubling conversion on the laser to be measured to generate a second harmonic;

[0010] A power receiving module for receiving the second harmonic power;

[0011] A monitoring terminal connected to the pulse width adjustment block and the power receiving module, obtaining the laser pulse width and the corresponding second harmonic power information, and performing fitting to establish a relationship diagram between the two, so as to realize monitoring the laser pulse width through the frequency doubling information.

[0012] Preferably, the power attenuation module includes a half-wave plate and a polarization beam splitter prism.

[0013] Preferably, the width adjustment module includes two mirrors and an autocorrelator. The laser beam to be measured passes through the polarization beam splitter prism. A part of it is reflected to the mirror and finally reflected into the autocorrelator, and the other part is incident on the second harmonic generation module.

[0014] Preferably, the second harmonic generation module includes a positive lens, a frequency doubling crystal, and a harmonic beam splitter prism arranged in sequence along the incident direction. Among them, the positive lens is used to focus the laser, and the harmonic beam splitter prism forms a 45° angle with the laser incident angle, and reflects the second harmonic light after passing through the frequency doubling crystal into the power receiving module.

[0015] Preferably, the frequency doubling crystal is installed on a position adjustment seat.

[0016] Preferably, the size of the focused spot of the positive lens is:

[0017]

[0018] where λ is the wavelength of the laser to be measured, f is the focal length of the positive lens, and D is the diameter of the laser to be measured.

[0019] Preferably, the power receivable module is a power meter.

[0020] A method for monitoring the pulse width based on frequency doubling includes the following steps:

[0021] S1. Change the polarization state of the laser emitted by the laser and attenuate the power of the laser;

[0022] S2. Obtain the pulse width information of the laser beam;

[0023] S3. Incident the laser beam with attenuated power on the frequency doubling crystal, emit the second harmonic light into the power meter, and obtain the second harmonic information;

[0024] S4. Fit the second harmonic information and the pulse width information, establish a second harmonic - pulse width relationship diagram, and realize the monitoring of the pulse width through frequency doubling.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: By monitoring the pulse width through frequency doubling, it has high time resolution and sensitivity. Even a weak pulse signal can be detected through appropriate signal amplification. The measurement process is achieved through a small amount of laser beam splitting and will not affect the main laser beam. It can realize the real-time monitoring of the laser pulse width and can provide real-time feedback on the operating state of the laser. Brief Description of the Drawings

[0026] Figure 1 It is a structural block diagram of the pulse width monitoring system;

[0027] Figure 2 It is a flowchart of the pulse width monitoring method. Specific implementation manner

[0028] The following combines with the attached drawings to describe in detail a specific implementation manner of the present invention. However, it should be understood that the protection scope of the present invention is not limited by the specific implementation manner.

[0029] As Figure 1 shown, a pulse width monitoring system based on frequency doubling provided by an embodiment of the present invention includes a laser, a pulse width adjustment module, a power attenuation module, a second harmonic generation module, and a power receiving module;

[0030] The laser is fixedly arranged along the direction of the optical path to be measured;

[0031] The pulse width adjustment module changes the second-order dispersion of the laser through an external control software to change the pulse width of the laser, and measures the changed laser pulse width through an autocorrelator. The external control is a prior art, so it will not be elaborated here;

[0032] The power attenuation module includes a half-wave plate and a polarization beam splitter prism. The half-wave plate and the polarization beam splitter prism are fixedly arranged in sequence along the incident direction of the laser to be measured behind the laser, and are used to attenuate the power of the laser by changing the polarization state of the laser;

[0033] The above-mentioned wave plate and polarization beam splitter prism are both arranged along the central axis of the laser beam to be measured, so that a part of the laser beam to be measured is reflected to the mirror after passing through the polarization beam splitter prism, passes through two mirrors, and is directly incident into the autocorrelator, and the other part of the beam is directly incident on the lens, and the angle of the wave plate is adjusted to make the power of the laser to be measured within the threshold range acceptable by the crystal;

[0034] The second harmonic generation module includes a positive lens, a frequency doubling crystal, and a harmonic beam splitter. The positive lens, the frequency doubling crystal, and the harmonic beam splitter are fixedly arranged in sequence along the incident direction of the laser to be measured behind the polarization beam splitter prism, and are used to perform frequency doubling conversion on the laser to be measured, generate a second harmonic, and filter out the light of the remaining wavelengths;

[0035] The power receiving module includes a power meter, which is used to receive the power of the second harmonic generated by frequency doubling, and obtain the relationship between the power of the second harmonic and the pulse width through data analysis, so as to monitor the change of the pulse width through the power of the second harmonic;

[0036] The positive lens is fixedly arranged along the laser incident direction behind the wave plate, and is used to focus the laser. The size of the focused spot is:

[0037]

[0038] wherein, λ is the wavelength of the laser to be measured, f is the focal length of the positive lens, and D is the diameter of the laser to be measured;

[0039] The frequency doubling crystal is installed on a position adjustment base. The frequency doubling crystal is fixed behind the positive lens, and its specific position is adjusted through the position adjustment base to achieve the optimal frequency doubling efficiency. Among them, the position adjustment base is a conventional structure, so it will not be elaborated here.

[0040] The harmonic beam splitter is fixedly placed at the incident position of 45° along the laser incident direction. After the laser to be measured passes through the frequency doubling crystal, the frequency doubled light is reflected into the power meter, and the fundamental frequency light is projected onto the absorption plate.

[0041] Embodiment 2

[0042] As Figure 2 shown, on the basis of Embodiment 1, this embodiment proposes a pulse width monitoring method based on frequency doubling, which specifically includes the following steps:

[0043] S1. Change the polarization state of the laser emitted by the laser and attenuate the power of the laser.

[0044] S2. Obtain the pulse width information of the laser beam.

[0045] S3. Incident the laser beam with attenuated power onto the frequency doubling crystal, emit the frequency doubled light into the power meter, and obtain the frequency doubling information of the frequency doubled light.

[0046] S4. Fit the frequency doubling information and the pulse width information to establish a frequency doubling - pulse width relationship diagram, and realize the monitoring of the pulse width through frequency doubling.

[0047] In subsequent use, the power meter obtains the frequency doubling information in real time, and through the frequency doubling - pulse width relationship diagram, the pulse width information of the laser can be obtained.

[0048] Monitoring the pulse width through frequency doubling has high time resolution and sensitivity. Even weak pulse signals can be detected through appropriate signal amplification. The measurement process is achieved through a small amount of laser beam splitting and will not affect the main laser beam. For pulses with extremely short pulse widths (femtoseconds or shorter), conventional electronic detection means cannot provide a fast enough response, while the frequency doubling technology can achieve indirect measurement through nonlinear optical effects. The system has a simple structure, is easy to operate, has few mechanical moving parts, high stability, and can realize real - time monitoring of the laser pulse width, and can provide real - time feedback on the operating state of the laser.

[0049] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit and basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0050] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A pulse width monitoring system based on frequency doubling, characterized in that: include: Lasers; A pulse width adjustment module, used to change the pulse width of the laser emitted by the laser and detect the changed laser pulse width; A power attenuation module is arranged behind the laser along the incident direction of the laser and is used to change the polarization state of the laser; The second harmonic generation module is arranged behind the power attenuation module along the laser incident direction, and is used to perform frequency doubling conversion on the laser to be tested to generate the second harmonic; A power receiving module, used for receiving second harmonic power; The monitoring terminal is connected to the pulse width adjustment block and the power receiving module to obtain the laser pulse width and the corresponding second harmonic power information, and to fit them to establish a relationship diagram between the two, so as to realize the monitoring of the laser pulse width through the frequency doubling information.

2. The pulse width monitoring system based on frequency doubling as claimed in claim 1, characterized in that: The power attenuation module includes a half wave plate and a polarization beam splitter prism.

3. The pulse width monitoring system based on frequency doubling as claimed in claim 2, characterized in that: The width adjustment module includes two reflectors and an autocorrelator. The laser beam to be measured passes through a polarization beam splitter prism, a part of which is reflected to the reflector and finally reflected into the autocorrelator, and the other part is incident to the second harmonic generation module.

4. The pulse width monitoring system based on frequency doubling as claimed in claim 1, characterized in that: The second harmonic production module includes a positive lens, a frequency doubling crystal and a harmonic beam splitter arranged in sequence along the incident direction, wherein the positive lens is used to focus the laser, and the harmonic beam splitter forms an angle of 45° with the laser incident angle, reflecting the frequency-doubled light after passing through the frequency doubling crystal into the power receiving module.

5. The pulse width monitoring system based on frequency doubling as claimed in claim 4, characterized in that: The frequency doubling crystal is installed on a position adjustment seat.

6. The pulse width monitoring system based on frequency doubling as claimed in claim 4, characterized in that: The focusing spot size of the positive lens is: Among them, λ is the wavelength of the laser to be measured, f is the focal length of the positive lens, and D is the diameter of the laser to be measured.

7. The pulse width monitoring system based on frequency doubling as claimed in claim 1, characterized in that: The power receiving module is a power meter.

8. A pulse width monitoring method based on frequency doubling, characterized in that: The steps include: S1, change the polarization state of the laser emitted by the laser to attenuate the laser power; S2, obtaining the pulse width information of the laser beam; S3, incident the laser beam after power attenuation onto a frequency doubling crystal to obtain frequency doubling information of the frequency doubling light; S4. Fit the frequency doubling information and the pulse width information, establish a frequency doubling-pulse width relationship diagram, and realize monitoring of the pulse width through the frequency doubling.

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