Multi-pass amplifier pump online monitoring and early warning device and method

Abstract

The present application relates to a kind of multi-pass amplifier pump online monitoring early warning device and method, including multi-pass amplifier, first pump source, first pump source imaging system, second pump source, second pump source imaging system, also including pump source online monitoring system, the pump source online monitoring imaging system is sequentially provided with collimating system, imaging system and CCD along the direction of light path, the transmission light of first reflector or second reflector enters the pump source online monitoring imaging system, the pump source online monitoring imaging system monitors first pump source or second pump source according to the transmission light signal, and early warning.The present application can effectively monitor early warning to pump source light spot data, and then guarantee the reliability of multi-pass amplifier use performance.

Description

Technical Field

[0001] This invention relates to an online monitoring and early warning device and method for multi-pass amplifier pumps. Background Technology

[0002] Since the introduction of chirped laser pulse amplification (CPA), the peak power of lasers has advanced by leaps and bounds, with laser pulse peak power reaching several PW (10¹⁵ W) and laser intensity reaching 10²² W / cm². 2 These types of strong-field lasers are widely used in laser-plasma interactions.

[0003] Common CPA (Cyclic Polarization) techniques are as follows: An oscillator generates an ultrashort pulse (pulse width typically on the order of picoseconds or femtoseconds) as a seed source. This pulse is then time-stretched by a stretcher to obtain a long pulse (pulse width on the order of tens of picoseconds to nanoseconds, the specific length depending on the final energy to be amplified). An amplifier system amplifies the stretched long pulse to obtain a high-energy pulse. Finally, a compressor minimizes the pulse's time scale (returning it to the order of the seed source pulse width) to obtain a high-peak-power, high-field laser pulse. When the energy exceeds ten millijoules, limitations imposed by the regenerating cavity mode size and damage threshold necessitate multi-pass amplification for further laser amplification. However, in multi-pass amplification, the quality of the amplified laser spot is severely affected by the pump and seed spot quality. Furthermore, to achieve good conversion efficiency, extremely high pump energy flux densities are required, placing stringent demands on the pump source's spot quality, necessitating high uniformity.

[0004] However, in actual operation of pumped lasers, the pump source energy decreases with increasing usage time, which inevitably affects the amplifier's output energy. Furthermore, the internal optical components of the pump source may be damaged due to prolonged use, leading to a deterioration of the pump source's output beam. This has a significant impact on the multi-pass amplifier's output beam, causing it to become uneven and potentially damaging the amplifier's optical components. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide an online monitoring and early warning device and method for multi-pass amplifier pumps, which can effectively monitor and warn of pump source spot data, thereby ensuring the reliability of the multi-pass amplifier's performance.

[0006] Based on the same inventive concept, this invention has two independent technical solutions:

[0007] 1. A multi-pass amplifier pump online monitoring and early warning device, comprising a multi-pass amplifier, a first pump source, a first pump source imaging system, a second pump source, and a second pump source imaging system, wherein the light emitted from the first pump source passes through the first pump source imaging system and is reflected by a first mirror to the gain medium of the multi-pass amplifier, and the light emitted from the second pump source passes through the second pump source imaging system and is reflected by a second mirror to the gain medium of the multi-pass amplifier.

[0008] The system includes an online monitoring and imaging system for pump sources. This system comprises a collimation system, an imaging system, and a CCD arranged sequentially along the optical path. Transmitted light from the first or second reflecting mirror enters the online monitoring and imaging system for pump sources.

[0009] The pump source online monitoring and imaging system monitors and provides early warning for the first or second pump source based on the transmitted light, including performing the following operations:

[0010] The minimum resolution of the acquired image is obtained by acquiring the image through the CCD, and the pump source online monitoring imaging system is debugged based on the minimum resolution and the CCD resolution.

[0011] Through the aforementioned debugging, the light spot data thresholds of the CCD acquired image are set, including the light spot size threshold, the light spot position threshold, and the light spot energy threshold;

[0012] Based on the light spot data threshold and the light spot data collected by the CCD, the pump source is monitored and warned.

[0013] Furthermore, the pump source online monitoring imaging system also includes a beam-shrinking system, which is disposed between the collimation system and the imaging system.

[0014] Furthermore, the imaging system of the pump source online monitoring imaging system adopts a spherical lens, and the imaging magnification of the spherical lens is ≤10 times.

[0015] Furthermore, corresponding to the first pump source and the second pump source, a first pump source online monitoring imaging system and a second pump source online monitoring imaging system are respectively provided. The collimation system of the first pump source online monitoring imaging system is a first lens, and the distance between the first lens and the first reflector is equal to the distance between the multi-pass amplifier gain medium and the first reflector. The collimation system of the second pump source online monitoring imaging system is a second lens, and the distance between the second lens and the second reflector is equal to the distance between the multi-pass amplifier gain medium and the second reflector.

[0016] Furthermore, the beam-shrinking system of the pump source online monitoring imaging system consists of a third lens and a fourth lens, with a beam-shrinking ratio greater than 1 and less than 5.

[0017] 2. A monitoring and early warning method using the above-mentioned device, comprising the following steps:

[0018] Step 1: Acquire images using the CCD, and based on the clarity analysis of the acquired images, debug the pump source online monitoring imaging system;

[0019] Step 2: Set the light spot data threshold of the CCD-acquired image through debugging;

[0020] Step 3: Based on the light spot data threshold and the light spot data collected by the CCD, monitor and issue early warnings for the pump source.

[0021] Further, step 1 includes the following steps:

[0022] Step 1.1: Obtain the frequency domain curve of the light spot using the CCD;

[0023] Step 1.2: Based on the frequency domain curve of the light spot, obtain the minimum resolution of the CCD-acquired image;

[0024] Step 1.3: Compare the minimum resolution of the CCD-acquired image with the CCD resolution of the pump source online monitoring system. If the ratio is greater than 0.5, the image clarity is deemed to meet the requirements, and proceed to Step 2; otherwise, adjust the pump source online monitoring imaging system until the image clarity meets the requirements.

[0025] Further, in step 1.1, the frequency domain curve of the light spot is obtained by the following method:

[0026] Step 1.1.1: Place a light-blocking hard card within 0-5cm in front of the pump source output port to block half of the light spot and obtain the light spot image;

[0027] Step 1.1.2: Process the collected light spot image, draw a straight line through the center of the light spot, and sample the data on the straight line to obtain the intensity curve;

[0028] Step 1.1.3: Differentiate the obtained intensity curve to obtain a linear rate of change graph;

[0029] Step 1.1.4: Perform a Fourier transform on the linear rate of change graph to obtain the modulation transfer function curve, which is the frequency domain distribution curve.

[0030] Further, in step 2, the light spot data thresholds of the CCD-acquired image include a light spot size threshold, a light spot position threshold, and a light spot energy threshold, which are obtained through the following method:

[0031] The CCD in the pump online monitoring system records n data points, including the spot size A, spot position B, and spot energy C in each data point.

[0032] Calculate the average values ​​of the three data points: spot size A, spot position B, and spot energy C. Set the upper threshold values ​​of spot size, spot position, and spot energy as 110% of their respective average values. Set the lower threshold values ​​of spot size, spot position, and spot energy as 90% of their respective average values.

[0033] Furthermore, step 3 specifically includes the following steps:

[0034] Step 3.1: Before turning on the pump source, place a light-blocking plate in front of the multi-pass amplifier gain medium to prevent the light from the pump source from entering the multi-pass amplifier gain medium;

[0035] Step 3.2: Use the spot data collected by the CCD to obtain the value of the spot size; when the value of the spot size is between the upper threshold and the lower threshold of the spot size, it indicates that the divergence angle of the pump source is normal, and proceed to step 3.3; otherwise, stop the operation and check the pump source.

[0036] Step 3.3: Obtain the spot position using the spot data acquired by the CCD. When the value of the spot position is between the upper threshold and the lower threshold of the spot position, it indicates that the pump source directivity is normal, and proceed to step 3.4; otherwise, stop the operation and check the pump source.

[0037] Step 3.4: Obtain the spot energy using the spot data acquired by the CCD. When the spot energy value is between the upper threshold and the lower threshold of spot energy, it indicates that the pump source output energy is normal, and proceed to step 3.5; otherwise, stop the operation and check the pump source.

[0038] Step 3.5: Remove the light-blocking plate and run the multi-pass amplifier normally.

[0039] The beneficial effects of the above technical solution are as follows:

[0040] This invention includes an online pump source monitoring system. The online pump source monitoring imaging system comprises a collimation system, an imaging system, and a CCD sequentially arranged along the optical path. Transmitted light from the first or second reflecting mirror enters the online pump source monitoring imaging system. Based on the transmitted light signal, the online pump source monitoring imaging system monitors and provides early warning for the first or second pump source. Images are acquired through the CCD of the online pump source monitoring system. Based on the clarity analysis of the acquired images, the online pump source monitoring system is adjusted. Through adjustment, a light spot data threshold is set for the CCD-acquired images. Based on the light spot data threshold, the pump source is monitored and warned. This invention can effectively monitor and warn of pump source light spot data. When the light spot data exceeds the light spot data threshold, the multi-pass amplifier stops operating, and the pump source is checked, thereby effectively ensuring the reliability of the multi-pass amplifier's performance.

[0041] The pump source online monitoring imaging system of this invention comprises, sequentially along the optical path, a collimation system, a beam-shrinking system, an imaging system, and a CCD. The imaging system employs a spherical lens with an imaging magnification ≤10x. The collimation system is a first lens, and the distance between the first lens and either the first or second reflecting mirror is the same as the distance between the multi-pass amplifier gain medium and either the first or second reflecting mirror. The beam-shrinking system consists of a second and a third lens, with a beam-shrinking ratio greater than 1 and less than 5. Through the structural design of the above-described pump source online monitoring imaging system, this invention effectively ensures the reliability of pump source monitoring.

[0042] This invention obtains the frequency domain curve of a light spot using a CCD in an online pump source monitoring system. Based on the frequency domain curve, it obtains the minimum resolution of the image acquired by the CCD in the online pump source monitoring system. The minimum resolution of the acquired image is compared with the CCD resolution of the online pump source monitoring system. If the ratio is greater than 0.5, the image clarity is deemed to meet the requirements, and the process proceeds to step 2. Otherwise, the online pump source monitoring system is adjusted until the image clarity meets the requirements. The frequency domain curve of the light spot is obtained as follows: a light-blocking hard card is placed within 0-5 cm in front of the pump source output port, blocking half of the light spot, resulting in a light spot image. The acquired light spot image is processed, and a straight line is drawn through the center of the light spot. Data on this straight line is sampled to obtain an intensity curve. The derivative of the obtained intensity curve is calculated to obtain a linear rate of change graph. A Fourier transform is performed on the linear rate of change graph to obtain the modulation transfer function curve, which is the frequency domain distribution curve. The present invention uses the above method to debug the pump source online monitoring system. After debugging, the light spot data threshold is set to effectively ensure the accuracy of pump source monitoring.

[0043] The CCD-acquired image spot data thresholds of the pump source online monitoring system of this invention include spot size thresholds, spot position thresholds, and spot energy thresholds. Specifically, these thresholds are obtained through the following method: The CCD in the pump online monitoring system records n data points, including spot size A, spot position B, and spot energy C for each data point. The average values ​​of spot size A, spot position B, and spot energy C are calculated. 110% of each average value is set as the upper threshold for spot size, upper threshold for spot position, and upper threshold for spot energy, respectively. 90% of each average value is set as the lower threshold for spot size, lower threshold for spot position, and lower threshold for spot energy, respectively. This invention obtains the spot size threshold, spot position threshold, and spot energy threshold using the above method, effectively ensuring the accuracy and reliability of pump source monitoring. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the online monitoring and early warning device for the multi-pass amplifier pump of the present invention;

[0045] Figure 2 This is the optical path diagram of a multi-pass amplifier;

[0046] Figure 3 This is a schematic diagram of the pump source online monitoring and imaging system according to Embodiment 1 of the present invention;

[0047] Figure 4 This is a schematic diagram of the pump source online monitoring and imaging system according to Embodiment 2 of the present invention;

[0048] Figure 5 This is a flowchart of the process for obtaining the frequency domain curve of the light spot according to the present invention;

[0049] Figure 6 It is a modulation function curve;

[0050] Figure 7 It is a pixel-to-line pair conversion diagram;

[0051] Figure 8 This is a flowchart of the pump source monitoring and early warning system of the present invention. Detailed Implementation

[0052] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described preferred embodiments, and the scope of the present invention is defined by the claims.

[0053] In the description of this invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance; those skilled in the art can understand the specific meaning of the above terms in this invention as appropriate.

[0054] Example 1

[0055] Multi-pass amplifier pump online monitoring and early warning device

[0056] like Figure 2 As shown, the multi-pass amplifier consists of reflectors 1-7 and an amplifier gain medium 10. The light emitted from the first pump source passes through the first pump source imaging system and is reflected by the first reflector M1 to the multi-pass amplifier gain medium 10. The light emitted from the second pump source passes through the second pump source imaging system and is reflected by the second reflector M2 to the multi-pass amplifier gain medium 10. The first reflector M1 and the second reflector M2 respectively direct the light from the first pump source and the second pump source onto the amplifier gain medium 10 in the multi-pass amplifier from opposite directions.

[0057] The specific optical path of the multi-pass amplifier is as follows: The seed source enters the multi-pass amplifier, first passing through mirror 1, where the optical path is deflected by 90°, and then reflected into mirror 2. After passing through mirror 2, the beam is deflected for the first time through gain medium 10. After passing through gain medium 10, it is deflected by mirror 3 and then through mirror 4. After passing through mirror 4, it passes through gain medium 10 a second time. After passing through gain medium 10, it passes through mirror 5 and is deflected by mirror 6. Mirror 6 deflects the beam and it passes through gain medium 10 a third time. After passing through gain medium 10, it passes through mirror 7 and is finally output. The laser optical path resets at the center position after passing through gain medium 10 three times.

[0058] The first pump source and the second pump source pump the gain medium 10 from both ends in a double-sided manner. The first pump source, after passing through lenses 101 and 102 of the first pump source imaging system, is reflected by the first reflecting mirror M1 and enters the gain medium 10. The light spot at the laser output port of the first pump source (0-5cm) is imaged onto the gain medium 10 by the first pump source imaging system. The second pump source, after passing through lenses 103 and 104 of the second pump source imaging system, is reflected by the second reflecting mirror and enters the gain medium 10. The light spot at the laser output port of the second pump source (0-5cm) is imaged onto the gain medium 10 by the second pump source imaging system.

[0059] The above multi-pass amplifier structure and optical path principle are existing technologies.

[0060] This embodiment is applicable when the diameter of the light spot transmitted by the first reflecting mirror M1 is less than 25mm.

[0061] like Figure 1 , Figure 2 As shown, corresponding to the first pump source and the second pump source, the present invention also includes a first pump source online monitoring system and a second pump source online monitoring system. The pump source online monitoring imaging system is provided with a collimation system, an imaging system and a CCD sequentially along the optical path direction. The transmitted light from the first reflector M1 or the second reflector M2 enters the pump source online monitoring imaging system. The pump source online monitoring imaging system monitors and provides early warning for the first pump source or the second pump source based on the transmitted light signal, including performing the following operations:

[0062] The minimum resolution of the acquired image is obtained by acquiring the image through the CCD, and the pump source online monitoring imaging system is debugged based on the minimum resolution and the CCD resolution.

[0063] Through the aforementioned debugging, the light spot data thresholds of the CCD acquired image are set, including the light spot size threshold, the light spot position threshold, and the light spot energy threshold;

[0064] Based on the light spot data threshold and the light spot data collected by the CCD, the pump source is monitored and warned.

[0065] The first pump source online monitoring system and the second pump source online monitoring system are identical. Taking the first pump source online monitoring system as an example, the first pump source online monitoring system is equipped with a collimation system, an imaging system, and a CCD sequentially along the optical path. The optical path is received by the CCD after passing through the pump imaging system. All imaging systems use ordinary spherical lenses. Ordinary spherical lenses are economical, durable, have a high damage threshold, and are widely applicable and easy to promote. However, because spherical lenses have aberrations, and the shorter the focal length, the greater the aberration, the less clear the image becomes. When the imaging magnification is ≤10x, the required image clarity can be achieved. In this embodiment, the imaging system uses spherical lenses, and the imaging magnification of the spherical lenses is ≤10x. The CCD used in the imaging system is a commercial industrial camera. This invention uses an acceptable pixel size of less than 2.5mm. This type of CCD is inexpensive, easy to promote, and has a high damage threshold.

[0066] like Figure 3As shown, in specific implementation, the first pump source online monitoring system is provided with a collimation system, an imaging system, and a CCD along the optical path. The collimation system is the first lens 301, and the imaging system is the second lens 302. After the beam passes through lens 101 and lens 102, it is deflected by the first reflecting mirror M1 and passes through the gain medium 10. The light leaks from behind the first reflecting mirror M1 and passes through the first lens 301. The distance between the first lens 301 and the first reflecting mirror M1 is the same as the distance between the gain medium 10 and the first reflecting mirror M1. The laser spot size and the laser spot divergence angle at the first lens 301 are the same as those on the gain medium 10. Since the first pump source imaging system of the first pump source images the spot at a certain point within 0-5cm of the outlet of the first pump source 1 onto the gain medium 10, the spot at the first lens 301 at this time is the image formed by the first pump source imaging system of the first pump source at a certain point within 0-5cm of the outlet of the first pump source. The light beam is collimated by the first lens 301, adjusting the divergence angle introduced by lenses 101 and 102 in the first pump source imaging system to obtain a parallel beam. The collimated beam then enters the imaging system, which consists of a second lens 302. The imaging system images the beam at the first lens 301. Since the image at the first lens 301 is located 0-5cm from the first pump source output port, the second lens 302 ultimately obtains an image at a specific location within 0-5cm of the first pump source output port. The image after passing through the imaging system is finally recorded in the CCD 303.

[0067] Example 2:

[0068] Multi-pass amplifier pump online monitoring and early warning device

[0069] The difference between Example 2 and Example 1 is that the pump source online monitoring imaging system is provided with a collimation system, a beam-shrinking system, an imaging system and a CCD in sequence along the optical path, that is, a beam-shrinking system is added.

[0070] like Figure 4 As shown, the collimation system is lens 201, and the beam-shrinking system consists of a third lens 202 and a fourth lens 203, with a beam-shrinking ratio greater than 1 and less than 5. The beam collimated by lens 201 is then shrunken by the beam-shrinking system before entering the imaging system, which consists of lens 204. The imaging system images the beam at lens 201. Since point 201 is the image of a location 0-5cm from the output port of the first pump source 1, lens 204 ultimately obtains the image of that location. The image after passing through the imaging system is finally recorded in CCD 205.

[0071] Example 3:

[0072] Monitoring and early warning method using the online monitoring and early warning device for multi-pass amplifier pumps according to Embodiment 1 or Embodiment 2

[0073] like Figure 8 As shown, the monitoring and early warning method of the multi-pass amplifier pump online monitoring and early warning device includes the following steps:

[0074] Step 1: Acquire images using the CCD sensor of the pump source online monitoring system, and debug the pump source online monitoring system based on the clarity analysis of the acquired images.

[0075] Specifically, the steps include the following:

[0076] Step 1.1: Obtain the frequency domain curve of the light spot using the CCD in the pump source online monitoring system;

[0077] In step 1.1, the frequency domain curve of the light spot is obtained using the following method.

[0078] Step 1.1.1: Place a light-blocking hard card within 0-5cm in front of the pump source output port, blocking half of the light spot, to obtain a light spot pattern. For example... Figure 5 As shown, Figure ① is the light spot pattern when it is not blocked. A hard card with flat edges is placed 0-5cm in front of the pump source output port to block half of the light spot, resulting in the light spot pattern ②.

[0079] Step 1.1.2: Process the acquired light spot image by drawing a straight line through the center of the light spot and sampling the data along the line to obtain the intensity curve. For example... Figure 5 As shown in Figure ②, the data of the light spot collected in Figure ② is processed. As shown in Figure ③, a straight line is drawn at the center of the light spot, and the data on the sampling line is used to obtain an intensity curve as shown in Figure ④.

[0080] Step 1.1.3: Differentiate the obtained intensity curve to obtain a linear rate of change graph. For example... Figure 5 As shown, the derivative of the obtained intensity curve is used to obtain the linear rate of change graph ⑤.

[0081] Step 1.1.4: Perform a Fourier transform on the linear rate of change graph to obtain the modulation transfer function curve, which is the frequency domain distribution curve. For example... Figure 5 As shown, the obtained linear rate of change is subjected to Fourier transform to obtain the modulation transfer function (MTF) curve (Figure 6), which is the frequency domain distribution curve.

[0082] Step 1.2: Based on the frequency domain curve of the light spot, obtain the minimum resolution of the CCD image acquired by the pump source online monitoring system;

[0083] Figure 6This is a modulation transfer function (MTF) curve, where the horizontal axis represents spatial frequency and the vertical axis represents the MTF value. Spatial frequency describes the spatial variation of pixel grayscale in an image, and the unit of spatial frequency in the graph is line pairs per millimeter (lp / mm). The MTF value can be understood as the ratio of the contrast of the output image to the contrast of the input image, i.e., the ratio of the contrast of the image before and after passing through the imaging system in the pump source online monitoring system. The spatial frequency corresponding to 1 / 10 of the maximum MTF value is the minimum resolution of the acquired image. The values ​​are converted to the same unit based on the CCD's resolution and then compared.

[0084] Step 1.3: Compare the minimum resolution of the CCD-acquired image with the CCD resolution of the pump source online monitoring system. If the ratio is greater than 0.5, the image clarity is deemed to meet the requirements, and proceed to Step 2; otherwise, debug the pump source online monitoring system and return to Step 1.1. Debugging the pump source online monitoring system refers to adjusting the distance between the second lens 302 or lens 204 and the CCD.

[0085] Figure 7 The pixel-to-line pair conversion diagram is calculated as follows.

[0086] The image has a total of X1*X2 pixels and an area of ​​Y1*Y2 square millimeters.

[0087] The number of pixels per square millimeter is X1*X2 / Y1*Y2.

[0088] Each millimeter width contains 100 pixels.

[0089] The number of line pairs per millimeter width is

[0090] Step 2: Set the threshold for the light spot data of the CCD image acquired by the pump source online monitoring system through debugging.

[0091] The threshold values ​​for the light spot data in the CCD-acquired images of the pump source online monitoring system include the light spot size threshold, the light spot location threshold, and the light spot energy threshold, which are obtained through the following methods.

[0092] The CCD in the pump online monitoring system records n data points (60 data points in this embodiment). For each data point, the light spot size A, light spot position B, and light spot energy C are recorded. The average value of the three data points A, B, and C is calculated. 110% of each average value is set as the upper threshold for light spot size, upper threshold for light spot position, and upper threshold for light spot energy, respectively. 90% of each average value is set as the lower threshold for light spot size, lower threshold for light spot position, and lower threshold for light spot energy, respectively.

[0093] The methods for obtaining the above-mentioned spot location, spot size, and spot energy value are as follows:

[0094] Take the image from the dark area as the background value, and subtract this background value from the data obtained by the CCD.

[0095] The three-dimensional planar image and the two-dimensional curve image of the light spot are obtained.

[0096] The spot size is obtained by taking the half-width at half-maximum of the peak intensity in the two-dimensional curve.

[0097] The XY coordinates of the light spot are obtained from the midpoint of the half-width and half-height.

[0098] The area of ​​the light spot is obtained from the half-width at half-maximum (HWHM). The total energy per unit time / the area of ​​the light spot = the energy density.

[0099] The total number of pixels is obtained from the half-width at half-maximum (WHM), and the average intensity is obtained by dividing the total intensity within the light spot by the total number of pixels.

[0100] Step 3: Based on the light spot data threshold, monitor and issue early warnings for the pump source.

[0101] Includes the following steps:

[0102] Step 3.1: Before turning on the pump source, place a light-blocking plate in front of the multi-pass amplifier gain medium to prevent the light from the pump source from entering the multi-pass amplifier gain medium;

[0103] Step 3.2: Use the spot data collected by the CCD of the pump online monitoring system to obtain the value of the spot size; when the value of the spot size is between the upper threshold and the lower threshold of the spot size, it indicates that the divergence angle of the pump source is normal, and proceed to step 3.3; otherwise, stop the operation and check the pump source.

[0104] Step 3.3: Obtain the spot position using the spot data acquired by the CCD. When the value of the spot position is between the upper threshold and the lower threshold of the spot position, it indicates that the pump source directivity is normal, and proceed to step 3.4; otherwise, stop the operation and check the pump source.

[0105] Step 3.4: Obtain the spot energy using the spot data acquired by the CCD. When the spot energy value is between the upper threshold and the lower threshold of spot energy, it indicates that the pump source output energy is normal, and proceed to step 3.5; otherwise, stop the operation and check the pump source.

[0106] Step 3.5: Remove the light-blocking plate and run the multi-pass amplifier normally.

[0107] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A multi-pass amplifier pump online monitoring and early warning device, comprising a multi-pass amplifier, a first pump source, a first pump source imaging system, a second pump source, and a second pump source imaging system, wherein the light emitted from the first pump source passes through the first pump source imaging system and is reflected by a first mirror to the gain medium of the multi-pass amplifier, and the light emitted from the second pump source passes through the second pump source imaging system and is reflected by a second mirror to the gain medium of the multi-pass amplifier, characterized in that: The system includes an online monitoring and imaging system for pump sources. This system comprises a collimation system, an imaging system, and a CCD arranged sequentially along the optical path. Transmitted light from the first or second reflecting mirror enters the online monitoring and imaging system for pump sources. The pump source online monitoring and imaging system monitors and provides early warning for the first or second pump source based on the transmitted light, including performing the following operations: The minimum resolution of the acquired image is obtained by acquiring the image through the CCD, and the pump source online monitoring imaging system is debugged based on the minimum resolution and the CCD resolution. Through the aforementioned debugging, the light spot data thresholds of the CCD acquired image are set, including the light spot size threshold, the light spot position threshold, and the light spot energy threshold; Based on the light spot data threshold and the light spot data collected by the CCD, the pump source is monitored and warned.

2. The online monitoring and early warning device for multi-pass amplifier pumps according to claim 1, characterized in that: The pump source online monitoring imaging system also includes a beam-shrinking system, which is located between the collimation system and the imaging system.

3. The online monitoring and early warning device for multi-pass amplifier pumps according to claim 1 or 2, characterized in that: The imaging system uses a spherical lens, and the magnification of the spherical lens is ≤10x.

4. The online monitoring and early warning device for multi-pass amplifier pumps according to claim 2, characterized in that: Corresponding to the first pump source and the second pump source, a first pump source online monitoring imaging system and a second pump source online monitoring imaging system are respectively provided. The collimation system of the first pump source online monitoring imaging system is a first lens, and the distance between the first lens and the first reflector is equal to the distance between the gain medium of the multi-pass amplifier and the first reflector. The collimation system of the second pump source online monitoring imaging system is the second lens, and the distance between the second lens and the second reflector is equal to the distance between the multi-pass amplifier gain medium and the second reflector.

5. The online monitoring and early warning device for multi-pass amplifier pumps according to claim 2, characterized in that: The beam-contraction system of the pump source online monitoring imaging system consists of a third lens and a fourth lens, with a beam-contraction ratio greater than 1 and less than 5.

6. A method for online monitoring and early warning of a multi-pass amplifier pump based on the online monitoring and early warning device for the multi-pass amplifier pump according to claim 1, characterized in that, Includes the following steps: Step 1: Acquire images using the CCD, and based on the clarity analysis of the acquired images, debug the pump source online monitoring imaging system; Step 2: Set the light spot data threshold of the CCD-acquired image through debugging; Step 3: Based on the light spot data threshold and the light spot data collected by the CCD, monitor and issue early warnings for the pump source.

7. The method according to claim 6, characterized in that, Step 1 includes the following steps: Step 1.1: Obtain the frequency domain curve of the light spot using the CCD; Step 1.2: Based on the frequency domain curve of the light spot, obtain the minimum resolution of the CCD-acquired image; Step 1.3: Compare the minimum resolution of the CCD-acquired image with the CCD resolution of the pump source online monitoring system. If the ratio is greater than 0.5, the image clarity is deemed to meet the requirements, and proceed to Step 2; otherwise, adjust the pump source online monitoring imaging system until the image clarity meets the requirements.

8. The method according to claim 7, characterized in that, In step 1.1, the frequency domain curve of the light spot is obtained by the following method: Step 1.1.1: Place a light-blocking hard card within 0-5cm in front of the pump source output port to block half of the light spot and obtain the light spot image; Step 1.1.2: Process the collected light spot image, draw a straight line through the center of the light spot, and sample the data on the straight line to obtain the intensity curve; Step 1.1.3: Differentiate the obtained intensity curve to obtain a linear rate of change graph; Step 1.1.4: Perform a Fourier transform on the linear rate of change graph to obtain the modulation transfer function curve, which is the frequency domain distribution curve.

9. The method according to claim 6, characterized in that: In step 2, the light spot data thresholds of the CCD-acquired image include a light spot size threshold, a light spot position threshold, and a light spot energy threshold, which are obtained through the following method. The CCD in the pump online monitoring system records n data points, including the spot size A, spot position B, and spot energy C in each data point. Calculate the average values ​​of the three data points: spot size A, spot position B, and spot energy C. Set the upper threshold values ​​of spot size, spot position, and spot energy as 110% of their respective average values. Set the lower threshold values ​​of spot size, spot position, and spot energy as 90% of their respective average values.

10. The method according to claim 9, characterized in that, Step 3 specifically includes the following steps: Step 3.1: Before turning on the pump source, place a light-blocking plate in front of the multi-pass amplifier gain medium to prevent the light from the pump source from entering the multi-pass amplifier gain medium; Step 3.2: Use the spot data collected by the CCD to obtain the value of the spot size; when the value of the spot size is between the upper threshold and the lower threshold of the spot size, it indicates that the divergence angle of the pump source is normal, and proceed to step 3.3; otherwise, stop the operation and check the pump source. Step 3.3: Obtain the spot position using the spot data acquired by the CCD. When the value of the spot position is between the upper threshold and the lower threshold of the spot position, it indicates that the pump source directivity is normal, and proceed to step 3.4; otherwise, stop the operation and check the pump source. Step 3.4: Obtain the spot energy using the spot data acquired by the CCD. When the spot energy value is between the upper threshold and the lower threshold of spot energy, it indicates that the pump source output energy is normal, and proceed to step 3.5; otherwise, stop the operation and check the pump source. Step 3.5: Remove the light-blocking plate and operate the multi-pass amplifier normally.

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