Laser frequency multiplication method and device based on temperature active following compensation

Abstract

The application provides a laser frequency doubling method and device based on temperature active following compensation. The method comprises the following steps: establishing a functional relationship between input fundamental frequency light power and corresponding first crystal temperature, and fitting to obtain a characteristic curve; for the current power of the input fundamental frequency light, determining the corresponding first crystal temperature through the characteristic curve; adjusting the frequency doubling crystal temperature in a certain temperature interval above and below the first crystal temperature with an accurate temperature difference interval, detecting and recording the output frequency doubling light power of the frequency doubling crystal at different temperatures; selecting the temperature corresponding to the maximum output frequency doubling light power as the second crystal temperature corresponding to the current power of the input fundamental frequency light; and based on the second crystal temperature corresponding to the current power, actively following and compensating the frequency doubling crystal temperature, and controlling the frequency doubling crystal temperature at the second crystal temperature. The application effectively realizes active following compensation of the frequency doubling crystal temperature, improves the control accuracy, and enhances the stability of the system.

Description

Technical Field

[0001] This invention relates to the field of laser frequency doubling technology, and more specifically, to a laser frequency doubling method and apparatus based on active temperature following compensation. Background Technology

[0002] Laser frequency doubling technology is one of the main techniques for converting laser light to shorter wavelengths. It utilizes the nonlinear optical effects of optical media under strong radiation fields to generate new frequencies, thereby broadening the range of laser wavelengths. Currently, laser frequency doubling technology can be applied not only in the research fields of quantum optics, laser spectroscopy, and nonlinear optics to experimentally prepare lasers of different wavelengths, but it has also reached a practical level, with commercially available devices and apparatus, and has a very wide range of applications.

[0003] During frequency doubling, the noncritical phase angle of the frequency doubling crystal often corresponds to a specific temperature. Changes in the ambient temperature can affect the optimal phase matching conditions of the frequency doubling crystal, leading to a decrease in frequency doubling efficiency and severely restricting the laser system from maintaining efficient and stable output. In the prior art, it has been proposed to compensate for the change in frequency doubling efficiency caused by temperature changes by actively following the temperature change of the crystal angle before laser pulse emission (see Zhao Runchang, Li Ping, Li Hai, Zhang Junwei, Geng Yuanchao, Li Zhijun, Su Jingqin. Crystal angle following third frequency doubling efficiency control technology. High Power Laser and Particle Beams, 2014, 26(10):204-207).

[0004] However, in practical applications, on the one hand, the frequency doubling efficiency of a crystal is extremely sensitive to angle, thus requiring very high precision in angle adjustment. Furthermore, the introduction of an angle adjustment device increases the degree of freedom in the laser system, affecting its stability. On the other hand, different laser powers need to be adjusted to meet the application requirements of different scenarios. This adjustment of the laser cavity power alters the heat absorbed by the crystal for the input fundamental and frequency-doubled light, leading to changes in the crystal's internal temperature. Therefore, during frequency doubling, active temperature compensation is necessary to balance the impact of the cavity power. Summary of the Invention

[0005] This invention provides a laser frequency doubling method and apparatus based on active temperature following compensation. At least three temperature monitoring points are set at the non-light-transmitting position of the frequency doubling crystal to facilitate more accurate detection of the crystal's actual temperature and real-time feedback for temperature compensation. A functional relationship between the input fundamental frequency light and the crystal temperature is established and a characteristic curve is fitted. When the laser power changes, the temperature compensation method for a certain characteristic point is as follows: First, the first crystal temperature T is initially determined based on the characteristic curve of the input fundamental frequency light power and the first crystal temperature. Then, within the range of T±ΔT, the crystal temperature is adjusted with an adjustment accuracy of 0.005~0.02℃, and the corresponding output frequency-doubled light power P is recorded. This process continues until the crystal temperature and output frequency-doubled light power are measured at all temperature points within the T±ΔT range. The second crystal temperature T0 corresponding to the maximum output frequency-doubled light power Pmax within the T±ΔT range is calculated. The temperature compensation device sends a command to the temperature control device to control the frequency doubling crystal temperature at the second crystal temperature T0, thus realizing active temperature following compensation of the frequency doubling system during dynamic changes in laser power. When changes in ambient temperature cause changes in the input fundamental frequency optical power or the output frequency harmonic optical power, the above method can be used to achieve active temperature tracking compensation, further improving the environmental adaptability of the device.

[0006] In a first aspect, the present invention provides a laser frequency doubling method based on active temperature following compensation, characterized in that the method includes:

[0007] Establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fit the characteristic curve.

[0008] For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve;

[0009] Within a certain temperature range above and below the temperature of the first crystal, the temperature of the frequency doubling crystal is adjusted with precise temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is detected and recorded.

[0010] The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the second crystal temperature corresponding to the current power of the input fundamental frequency optical power;

[0011] Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

[0012] Secondly, the present invention also provides a laser frequency doubling method based on active temperature following compensation, characterized in that the method includes:

[0013] Establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fit the characteristic curve.

[0014] For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve;

[0015] Determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal;

[0016] When the frequency doubling crystal is controlled at the upper limit temperature, the upper limit control parameters corresponding to the temperature control device are recorded.

[0017] When the frequency doubling crystal is controlled at the lower limit temperature, the corresponding lower limit control parameters of the temperature control device are recorded.

[0018] This causes the control parameters of the temperature control device to change from the lower limit control parameter to the upper limit control parameter, while simultaneously detecting and recording the output frequency-doubled optical power;

[0019] The control parameter corresponding to the maximum value of the output frequency-doubled optical power is selected as the precise control parameter, and the frequency-doubled crystal temperature corresponding to the precise control parameter is measured as the second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0020] Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

[0021] Thirdly, the present invention also provides a laser frequency doubling device based on active temperature following compensation, characterized in that the device comprises: a fundamental frequency light generator, a frequency doubling crystal, a characteristic curve acquisition unit, a characteristic curve reading unit, a temperature control device, a power detection and recording unit, and a temperature compensation device; wherein

[0022] The fundamental frequency light generator is used to generate input fundamental frequency light that is input to the frequency doubling crystal;

[0023] The feature curve acquisition unit is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve, and store the feature curve.

[0024] The characteristic curve reading unit is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve;

[0025] The temperature control device is used to measure the temperature of the frequency doubling crystal and adjust the temperature of the frequency doubling crystal at precise temperature difference intervals within a certain temperature range above and below the temperature of the first crystal.

[0026] The power detection and recording unit is used to detect and record the output frequency-doubled optical power of the frequency-doubled crystal at different frequency-doubled crystal temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0027] The temperature compensation device is used to actively follow and compensate the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal at the second crystal temperature.

[0028] Fourthly, the present invention also provides a laser frequency doubling device based on active temperature following compensation, characterized in that the device comprises: a fundamental frequency light generator, a frequency doubling crystal, a characteristic curve acquisition unit, a characteristic curve reading unit, a temperature range setting unit, a temperature control device, a control parameter adjustment unit, a power detection and recording unit, and a temperature compensation device; wherein

[0029] The fundamental frequency light generator is used to generate input fundamental frequency light that is input to the frequency doubling crystal;

[0030] The feature curve acquisition unit is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve, and store the feature curve.

[0031] The characteristic curve reading unit is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve;

[0032] The temperature range setting unit is used to determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal.

[0033] The temperature control device is used to measure the temperature of the frequency doubling crystal and record the upper limit control parameter corresponding to the temperature control device when the frequency doubling crystal is controlled at the upper limit temperature, and record the lower limit control parameter corresponding to the temperature control device when the frequency doubling crystal is controlled at the lower limit temperature.

[0034] The control parameter adjustment unit is used to change the control parameter of the temperature control device from the lower limit control parameter to the upper limit control parameter;

[0035] The power detection and recording unit is used to detect and record the output frequency-doubled optical power, and select the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter.

[0036] The temperature control device is also used to measure the frequency doubling crystal temperature corresponding to the precise control parameters as a second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0037] The temperature compensation device is used to actively follow and compensate the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal at the second crystal temperature.

[0038] The present invention provides a laser frequency doubling method and apparatus based on active temperature following compensation: First, by establishing a relationship function between the frequency doubling crystal temperature and the frequency doubling optical signal, the present invention achieves active temperature following compensation in the frequency doubling system, improving the temperature control accuracy of the frequency doubling crystal and enhancing the system stability; Second, in the active temperature following compensation mechanism of the frequency doubling crystal, the present invention can meet the active temperature following compensation requirements of the frequency doubling crystal when the laser operates at different powers, and the laser system can quickly reach a steady state during power switching, realizing precise dynamic control of the frequency doubling system; Third, the laser frequency doubling method and apparatus based on active temperature following compensation provided by the present invention can meet the requirements of operation under different ambient temperatures. Fourth, the invention adopts a multi-point measurement method for crystal temperature to address the uneven frequency doubling efficiency caused by the non-uniformity of crystal temperature distribution. Using multi-point measurement to obtain the average temperature can improve the accuracy of temperature measurement. Fifth, considering that the temperature adjustment in the process of determining the second crystal temperature is all indirect adjustment of the temperature control device, in order to further save the time in determining the second crystal temperature, the invention can also directly adjust the control parameters of the temperature control device to find the maximum output frequency doubling optical power to determine the precise control parameters. Finally, the frequency doubling crystal temperature corresponding to the precise control parameters is measured as the second crystal temperature corresponding to the current power of the input fundamental frequency light. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart of a laser frequency doubling method based on active temperature following compensation provided by an embodiment of the present invention;

[0041] Figure 2 yes Figure 1 A flowchart illustrating the specific method of step S101 in the embodiment;

[0042] Figure 3 This is a graph showing the functional relationship between the frequency doubling crystal temperature and the output frequency doubling optical power provided in the embodiments of the present invention;

[0043] Figure 4This is a graph showing the functional relationship between the input fundamental frequency optical power and the temperature of the first crystal, provided in an embodiment of the present invention.

[0044] Figure 5 This is a flowchart of another laser frequency doubling method based on active temperature following compensation provided in an embodiment of the present invention;

[0045] Figure 6 This is a graph showing the functional relationship between the control parameters and the output frequency-doubled optical power provided in the embodiments of the present invention;

[0046] Figure 7 This is a schematic diagram of a laser frequency doubling device based on active temperature following compensation provided in an embodiment of the present invention;

[0047] Figure 8 This is a schematic diagram of another laser frequency doubling device based on active temperature following compensation provided in an embodiment of the present invention;

[0048] Figure 9 yes Figure 7 or Figure 8 A schematic diagram of the internal structure of the fundamental frequency optical generator in the embodiment;

[0049] Figure 10 yes Figure 7 or Figure 8 A schematic diagram of the internal structure of the temperature control device in the embodiment;

[0050] Figure 11 yes Figure 7 or Figure 8 A schematic diagram of the internal structure of the power detection and recording unit in the embodiment;

[0051] Figure 12 yes Figure 8 A schematic diagram of the internal structure of the control parameter adjustment unit in the embodiment. Detailed Implementation

[0052] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Invention Overview

[0054] As mentioned above, this invention provides a laser frequency doubling method and apparatus based on active temperature following compensation, which realizes active temperature following compensation during the frequency doubling process, improves the temperature control accuracy of the frequency doubling crystal, and enhances the stability of the system; it can meet the active temperature following compensation requirements of the frequency doubling crystal under different power levels, and the laser system can quickly reach a steady state during power switching, realizing precise dynamic control of the frequency doubling system.

[0055] Exemplary methods

[0056] Figure 1This is a flowchart of a laser frequency doubling method based on active temperature following compensation provided in an embodiment of the present invention.

[0057] Laser frequency doubling utilizes nonlinear crystals, specifically the second-order nonlinear effect of a frequency-doubling crystal under the influence of a strong laser. This allows a laser beam with frequency ω to be transformed into output frequency-doubled light with a frequency of 2ω after passing through the frequency-doubling crystal; or it can induce second-harmonic oscillation, such as transforming a 1.06-micrometer laser beam into 0.532-micrometer green light after passing through a frequency-doubling crystal. Frequency doubling technology expands the wavelength range of laser light. Generally, the incident laser beam is called the input fundamental frequency light, and the laser beam output from the frequency-doubling crystal after frequency doubling is called the output frequency-doubled light. For example, the laser beam with frequency ω and the 1.06-micrometer laser mentioned above are the input fundamental frequency light; the laser beam with frequency 2ω and the 0.532-micrometer laser are the output frequency-doubled light.

[0058] When a fundamental frequency light of a certain power is frequency-doubled in a fixed frequency-doubled crystal, the output frequency-doubled light power varies depending on the crystal temperature and / or angle. In other words, the crystal temperature and angle affect the output frequency-doubled light power. To maintain a consistently high and stable output frequency-doubled light power, this invention first determines the approximate optimal crystal temperature corresponding to a certain frequency-doubled crystal at a given incident angle for different power input fundamental frequency light. Given the current power of the input fundamental frequency light, a precise optimal crystal temperature is further determined within a certain temperature range above and below the approximate optimal crystal temperature. Based on this precise optimal crystal temperature, the frequency-doubled crystal temperature is actively compensated to maintain it within the precise optimal crystal temperature range. When the current power changes, the precise optimal crystal temperature is promptly and accurately located within a small range near the corresponding approximate optimal crystal temperature.

[0059] Figure 1 The illustrated embodiment includes the following steps:

[0060] S101: Establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fit the characteristic curve.

[0061] The first crystal temperature is the approximate optimal temperature, meaning that at this temperature, the input fundamental frequency light of this power, after passing through the frequency doubling crystal, can achieve a greater output frequency-doubled light power than at other temperatures under the same conditions. The same conditions refer to the same type of frequency doubling crystal and the same angle.

[0062] A frequency doubling crystal is a type of nonlinear optical crystal used for the frequency doubling effect. Generally, the frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

[0063] This step involves first determining the corresponding first crystal temperature of a certain frequency doubling crystal for input fundamental frequency light of different powers, then establishing a functional relationship between the input fundamental frequency light power and the first crystal temperature, and finally fitting it to the characteristic curve corresponding to the frequency doubling crystal.

[0064] Therefore, different frequency doubling crystals have different characteristic curves. When the frequency doubling crystal is replaced, it is necessary to re-establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fit it to obtain its corresponding characteristic curve.

[0065] Specifically, such as Figure 2 As shown, step S101, which obtains the characteristic curve corresponding to the frequency doubling crystal, further includes the following steps:

[0066] S201: Input a certain power of fundamental frequency light into the frequency doubling crystal.

[0067] Preferably, the input fundamental frequency light of a certain power is collimated and focused at the center of the frequency doubling crystal. Collimation and focusing at the center of the frequency doubling crystal can achieve the best output effect.

[0068] S202: Adjust the temperature of the frequency doubling crystal within the specified operating temperature range of the frequency doubling crystal at rough temperature difference intervals, and record the output frequency doubling optical power of the frequency doubling crystal at different temperatures.

[0069] The specified operating temperature range of the frequency doubling crystal is the temperature range within which the frequency doubling crystal is stable and can produce frequency-doubled light. For example, if frequency doubling crystal A is stable in the range of -30℃ to 50℃, then its specified operating temperature range is -30℃ to 50℃.

[0070] The approximate temperature difference interval is 0.5 to 2°C, preferably 1°C. For example, assuming the specified operating temperature range of the frequency doubling crystal is -30°C to 50°C, the output frequency doubling optical power is measured starting from -30°C. The frequency doubling crystal temperature is adjusted every 1°C, and then the output frequency doubling optical power at -29°C, -28°C, -27°C...49°C, and 50°C is measured and recorded sequentially.

[0071] Preferably, in order to obtain an accurate correspondence between temperature and output frequency-doubled optical power, the time for each temperature adjustment and recording, as well as the detection time for the output frequency-doubled optical power, shall not exceed 1ms.

[0072] Preferably, the temperature of the frequency doubling crystal is regulated by a heating furnace, a semiconductor temperature controller, a heat pump, or a refrigeration compressor.

[0073] Preferably, the temperature is measured at multiple non-light-transmitting points of the frequency doubling crystal to obtain multiple temperatures, and the average value is taken as the temperature of the frequency doubling crystal. For example, at least three temperature monitoring points are set at the non-light-transmitting positions of the frequency doubling crystal to facilitate more accurate detection of the actual temperature of the crystal and real-time feedback to the temperature compensation device. Since the temperature at the light-transmitting position of the frequency doubling crystal is higher due to the input fundamental frequency light irradiation, setting the temperature monitoring points at the non-light-transmitting positions helps to obtain a more accurate temperature of the frequency doubling crystal. For example, the temperature of the crystal surface can be detected by attaching a thermal coupler to the crystal surface, or by using a far-infrared thermal imager. After measuring the temperatures at multiple temperature monitoring points, the average value is calculated to obtain a more accurate crystal temperature.

[0074] Preferably, the detection and recording of the output frequency-doubled optical power can be achieved by using a beam splitter to separate the output frequency-doubled optical signal after passing through the frequency-doubled crystal at a certain ratio; filtering and attenuating the separated optical signal to obtain a low-power pure optical signal, which is used as the frequency-doubled optical signal to be detected; and measuring and recording the power of the frequency-doubled optical signal to be detected to obtain the actual output frequency-doubled optical power.

[0075] For example, a beam splitter is used to separate the output frequency-doubled optical signal into a beam with 1% intensity; the separated optical signal is filtered and attenuated to remove noise signals and obtain a low-power pure optical signal, which is used as the frequency-doubled optical signal to be detected. The power of the frequency-doubled optical signal to be detected is measured and recorded, and the actual output frequency-doubled optical power is calculated according to the beam splitting ratio and filtering efficiency.

[0076] S203: Select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the first crystal temperature corresponding to the current power of the input fundamental frequency light.

[0077] It should be noted that the current power mentioned below refers to the current power of the input fundamental frequency light.

[0078] Figure 3 The graph shows the functional relationship between the frequency doubling crystal temperature and the output frequency doubling optical power of an 82W input fundamental frequency light. The horizontal axis represents the frequency doubling crystal temperature, and the vertical axis represents the output frequency doubling optical power. As can be seen from the graph, the output frequency doubling optical power varies at different frequency doubling crystal temperatures for an 82W input fundamental frequency light. A series of frequency doubling crystal temperatures and output frequency doubling optical powers were obtained with a rough temperature difference interval of 1℃. For example, point 130 corresponds to 219℃, point 110 corresponds to 220℃, and point 140 corresponds to 221℃. By roughly adjusting the frequency doubling crystal temperature, it was measured that when the frequency doubling crystal temperature is 220℃, i.e., point 110, the maximum output frequency doubling optical power is 42.9W. Therefore, 220℃ is the first crystal temperature for an 82W input fundamental frequency light (i.e., the roughly optimal crystal temperature for obtaining a larger output frequency doubling optical power).

[0079] S204: Input fundamental frequency light of different powers is sequentially input into the frequency doubling crystal at certain power intervals to obtain a first crystal temperature corresponding to different input fundamental frequency light powers.

[0080] For example, input fundamental frequency light with powers of 72W, 76W, 80W, 84W and 88W is sequentially input into the frequency doubling crystal, and the first crystal temperature corresponding to these five input fundamental frequency light powers is obtained through steps S202 and S203.

[0081] S205: Based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, curve fitting is performed to establish a functional relationship and obtain the characteristic curve.

[0082] Specifically, based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, a functional relationship is established using curve fitting software, and the following is fitted: Figure 4 The characteristic curve shown is represented by the input fundamental frequency optical power on the horizontal axis and the temperature of the first crystal on the vertical axis.

[0083] Fitting is the process of connecting a series of points on a plane with a smooth curve. Because there are countless possible curves, there are various fitting methods. The fitted curve can generally be represented by a function, and different functions have different names for the fitted curve.

[0084] Common fitting methods include least squares curve fitting, and in MATLAB, polyfit can be used to fit polynomials. Fitting, interpolation, and approximation are the three fundamental tools of numerical analysis. In layman's terms, their differences are: fitting is based on a known set of points, approximating them as a whole; interpolation is based on a known set of points that completely passes through them; and approximation is based on a known curve or set of points, using approximation to make the constructed function infinitely close to them.

[0085] S102: For the current power of the input fundamental frequency light, determine its corresponding first crystal temperature through the characteristic curve.

[0086] For example, the current power is 82W, from such Figure 4 The characteristic curve shown can be read as point 110, and its corresponding vertical axis indicates that the temperature of the first crystal is 220℃.

[0087] When the laser frequency doubling device is working, after the current power of the input fundamental frequency light changes, the first crystal temperature corresponding to the current power, i.e. the rough optimal crystal temperature, can be easily and quickly read from the characteristic curve in real time without having to perform the series of measurements and records mentioned above.

[0088] S103: Adjust the temperature of the frequency doubling crystal within a certain temperature range above and below the temperature of the first crystal with precise temperature difference intervals, and detect and record the output frequency doubling optical power of the frequency doubling crystal at different temperatures.

[0089] Specifically, based on the specified operating temperature range of the frequency doubling crystal, a certain temperature range above and below the temperature of the first crystal is set. This certain temperature range typically fluctuates by 1°C. For example, assuming the specified operating temperature range of the frequency doubling crystal is -30°C to 50°C, then the certain temperature range above and below the temperature of the first crystal cannot exceed -30°C to 50°C; if the temperature of the first crystal is 25°C, then the certain temperature range above and below the temperature of the first crystal is 24°C to 26°C.

[0090] The precise temperature difference interval is 0.005 to 0.02℃, and preferably, the precise temperature difference interval is 0.01℃.

[0091] S104: Select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light.

[0092] For example, assuming the current power of 50W corresponds to a first crystal temperature of 25℃, and the temperature range above and below the first crystal temperature is 24℃ to 26℃, then the first crystal temperature is adjusted from 24℃ to 26℃ in increments of 0.01℃. The output frequency-doubled optical power corresponding to these 200 first crystal temperatures (24℃, 24.01℃, 24.02℃...25.98℃, 25.99℃ and 30℃) is detected and recorded. The maximum value of 25W, corresponding to 24.78℃, is selected as the second crystal temperature.

[0093] For example, from Figure 4 From this, we can deduce that the temperature of the first crystal corresponding to the current power of 82W is 220℃. Figure 3 As shown, taking ΔT as 1℃, the temperature range of 220℃±1℃ is 219℃~221℃. Adjusting the temperature sequentially from 219℃ to 221℃ in 0.01℃ increments, and detecting the output frequency-doubled optical power, the maximum output frequency-doubled optical power is found to be 43W, corresponding to a frequency-doubled crystal temperature of 220.45℃. Figure 3 The midpoint is 120°C, meaning the temperature of the second crystal is 220.45°C.

[0094] S105: Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, actively follow and compensate the temperature of the frequency doubling crystal to control the temperature of the frequency doubling crystal at the second crystal temperature.

[0095] Regardless of the factors affecting the temperature change of the frequency doubling crystal, the temperature of the frequency doubling crystal will be actively compensated in real time to the temperature of the second crystal to ensure that the maximum output frequency doubling optical power is generated under the current frequency doubling crystal and current angle conditions. For example, when the external ambient temperature of the frequency doubling crystal changes, the temperature of the frequency doubling crystal is actively compensated to control the temperature of the frequency doubling crystal at the temperature of the second crystal.

[0096] When the current power of the input fundamental frequency light changes, the first crystal temperature corresponding to the current power is first read directly from the characteristic curve in real time. Then, steps S102 to S105 are executed again. That is, the second crystal temperature is determined within a more precise small range (a certain temperature range above and below the first crystal temperature) using a smaller temperature interval (precise temperature difference interval). The advantage of this invention is that it eliminates the need to spend time searching for the second crystal temperature over a large range during device operation. Instead, the first crystal temperature corresponding to different input fundamental frequency light powers is predetermined, and the second crystal temperature is determined directly within a small range, greatly saving the determination time of the second crystal temperature, improving the accuracy of frequency doubling crystal temperature control, and enhancing system stability. At the same time, when the input fundamental frequency light power changes, the second crystal temperature is obtained in the shortest time to meet the active following compensation requirement of the frequency doubling crystal temperature under different input fundamental frequency light powers. The laser system can quickly reach a steady state during power switching, realizing precise dynamic control of the frequency doubling system. Based on the second crystal temperature, that is, the precise optimal crystal temperature, the frequency doubling crystal temperature is actively followed and compensated in real time, which can meet the working requirements under different ambient temperatures and improve the environmental adaptability of the device.

[0097] Figure 5 This is a flowchart of another laser frequency doubling method based on active temperature following compensation provided in an embodiment of the present invention.

[0098] This embodiment and Figure 1The difference in the embodiments lies in the determination of the second crystal temperature. Considering that the determination of the second crystal temperature involves indirectly adjusting the frequency doubling crystal temperature by directly adjusting the control parameters of the temperature control device and detecting changes in the crystal temperature, multiple feedback cycles may be required to stabilize the frequency doubling crystal temperature at a predetermined value, resulting in a long adjustment time each time. Since the control parameters of the temperature control device and the frequency doubling crystal temperature exhibit a linear relationship within a small range when the ambient temperature is relatively stable for a short period, the corresponding frequency doubling crystal temperature can be indirectly calculated by adjusting the control parameters of the temperature control device. To further save time in determining the second crystal temperature, this embodiment uses direct adjustment of the control parameters to find the maximum output frequency doubling optical power to determine the precise control parameters. Finally, the frequency doubling crystal temperature measured under the precise control parameters is taken as the second crystal temperature corresponding to the current power of the input fundamental frequency light, as detailed in steps S503 to S507. This embodiment does not require precise detection and control of the specific values ​​of the frequency doubling crystal temperature at each temperature interval or detection of the corresponding output frequency doubling optical power; it only needs to record the output frequency doubling optical power corresponding to each control parameter.

[0099] Among them, steps S501, S502 and S508 are... Figure 1 Steps S101, S102, and S105 in the illustrated embodiments are the same.

[0100] This embodiment includes the following steps:

[0101] S501: Establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fit the characteristic curve;

[0102] S502: For the current power of the input fundamental frequency light, determine its corresponding first crystal temperature through the characteristic curve;

[0103] S503: Determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal;

[0104] S504: When the frequency doubling crystal is controlled at the upper limit temperature, record the upper limit control parameters corresponding to the temperature control device;

[0105] S505: When the frequency doubling crystal is controlled at the lower limit temperature, record the lower limit control parameter corresponding to the temperature control device;

[0106] S506: The control parameters of the temperature control device are changed from the lower limit control parameter to the upper limit control parameter, while the output frequency-doubled optical power is detected and recorded.

[0107] S507: Select the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter, and measure the frequency-doubled crystal temperature corresponding to the precise control parameter as the second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0108] S508: Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, actively follow and compensate the temperature of the frequency doubling crystal to control the temperature of the frequency doubling crystal at the second crystal temperature.

[0109] For example, from Figure 4 The characteristic curve shown indicates that the first crystal temperature corresponding to the current power of 82W is 220℃. A heating furnace is used to adjust the temperature of the frequency doubling crystal, and the control parameter is current. A certain temperature range centered on the first crystal temperature of 220℃ is selected as 219℃~221℃, with an upper limit temperature of 221℃ and a lower limit temperature of 219℃; for example... Figure 6 As shown, when the frequency doubling crystal is controlled at the lower limit temperature of 219°C, the lower limit control parameter corresponding to the temperature control device is recorded as 2.19A; when the frequency doubling crystal is controlled at the upper limit temperature of 221°C, the upper limit control parameter corresponding to the temperature control device is recorded as 2.21A; the current of the heating furnace is continuously changed from the lower limit control parameter 2.19A to the upper limit control parameter 2.21A, while the output frequency doubling optical power is detected and recorded; the current corresponding to the maximum value of the output frequency doubling optical power of 43W, 2.204A, is selected as the precise control parameter, i.e., point 120 in the figure, and the temperature of the frequency doubling crystal corresponding to the precise control parameter of 2.204A, 220.45°C, is measured as the second crystal temperature corresponding to the current power of the input fundamental frequency light; based on the second crystal temperature of 220.45°C corresponding to the current power of the input fundamental frequency light of 82W, the temperature of the frequency doubling crystal is actively followed and compensated to control the temperature of the frequency doubling crystal at the second crystal temperature of 220.45°C. During the active follow-up compensation process, it is necessary to measure the temperature of the frequency doubling crystal in real time and adjust the control parameters to ensure that the temperature of the frequency doubling crystal is not affected by the external environment.

[0110] In addition to continuously varying the control parameters of the temperature control device from the lower limit to the upper limit, as in the example above, to determine the precise control parameters, the interval between the upper and lower limit control parameters can be divided into multiple intervals. Preferably, the interval between the upper and lower limit control parameters is divided into 100 to 200 intervals, such as dividing the interval between the lower limit control parameter 2A and the upper limit control parameter 4A into 200 intervals. This allows the control parameters of the temperature control device to change sequentially from the lower limit control parameter 2A to the upper limit control parameter 4A at intervals of 2A, 2.01A, 2.02A...4.99A, 4A, while simultaneously measuring the output frequency-doubled optical power.

[0111] Other methods for finding local extrema, such as the bisection method or the traversal method, can also be used to quickly determine the control parameters corresponding to the maximum output frequency-doubled optical power.

[0112] Preferably, the adjustment and recording time of the control parameters and the detection time of the output frequency-doubled optical power each time do not exceed 1ms.

[0113] Specifically, when a heating furnace is used to adjust the temperature of the frequency doubling crystal, the control parameter is the current or the resistance of the heating wire; when a semiconductor temperature controller is used to adjust the temperature of the frequency doubling crystal, the control parameter is the current; when a heat pump or a compressor is used to adjust the temperature of the frequency doubling crystal, the control parameter is the duty cycle of the heat pump or compressor's operating and stopping signals, or it can be the control of its operating power.

[0114] Preferably, based on the specified operating temperature range of the frequency doubling crystal, an upper limit temperature and a lower limit temperature of a certain temperature range centered on the temperature of the first crystal are determined.

[0115] When the current power of the input fundamental frequency light changes, steps S502 to S508 are executed again.

[0116] In addition to the above technical features and Figure 1 The embodiments shown are different. Figure 1 All other technical features of the illustrated embodiment are the same in this embodiment.

[0117] Exemplary device

[0118] Accordingly, embodiments of the present invention also provide a laser frequency doubling device based on active temperature following compensation. Figure 7 This is a schematic diagram of a laser frequency doubling device 100 based on active temperature following compensation provided in an embodiment of the present invention, wherein straight lines represent signal transmission, dashed lines represent beam transmission, and arrows represent the transmission direction, as shown below. Figure 7 As shown, the device 100 provided in this embodiment includes:

[0119] The system includes a fundamental frequency optical generator 109, a frequency doubling crystal 101, a characteristic curve acquisition unit 102, a characteristic curve reading unit 103, a temperature control device 104, a power detection and recording unit 105, a temperature compensation device 106, and a temperature range setting unit 107; wherein:

[0120] The fundamental frequency light generator 109 is used to generate input fundamental frequency light that is input to the frequency doubling crystal 101;

[0121] The frequency doubling crystal 101 is a type of nonlinear optical crystal used for the frequency doubling effect. Generally, the frequency doubling crystal 101 is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

[0122] The feature curve acquisition unit 102 is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve, and store the feature curve. The feature curve can be stored in the memory in a functional manner, or other values ​​between detection points can be calculated based on the detection points using interpolation and stored in the memory.

[0123] Fitting is the process of connecting a series of points on a plane with a smooth curve. Because there are countless possible curves, there are various fitting methods. The fitted curve can generally be represented by a function, and different functions have different names for the fitted curve.

[0124] Common fitting methods include least squares curve fitting, and in MATLAB, polyfit can be used to fit polynomials. Fitting, interpolation, and approximation are the three fundamental tools of numerical analysis. In layman's terms, their differences are: fitting is based on a known set of points, approximating them as a whole; interpolation is based on a known set of points that completely passes through them; and approximation is based on a known curve or set of points, using approximation to make the constructed function infinitely close to them.

[0125] For different frequency doubling crystals, the corresponding characteristic curves are different. The characteristic curve acquisition unit 102 is also used to re-establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature for different frequency doubling crystals 101, and fit the corresponding characteristic curves.

[0126] Specifically, the feature curve acquisition unit 102 includes a feature curve fitting module.

[0127] The fundamental frequency optical generator 109 is used to input a certain power of fundamental frequency light into the frequency doubling crystal 101, such as... Figure 9As shown, the fundamental frequency light generator 109 includes a laser for emitting fundamental frequency light and a collimating focusing lens 1121, which is used to collimate and focus the input fundamental frequency light of a certain power at the center of the frequency doubling crystal 101. The substrate of the collimating focusing lens 1121 is generally fused silica material, and the lenses can be plano-convex lenses or crescent lenses. The lens design can be monolithic, multi-element, or aspherical. By using the fundamental frequency light generator 109 to collimate and focus the input fundamental frequency light of a certain power at the center of the frequency doubling crystal, the best output effect can be obtained.

[0128] The temperature control device 104 is used to adjust the temperature of the frequency doubling crystal 101 within the specified operating temperature range of the frequency doubling crystal 101 by a rough temperature difference interval. Preferably, the temperature control device 104 is a heating furnace, a semiconductor temperature controller, a heat pump or a refrigeration compressor, and the rough temperature difference interval is 0.5 to 2°C.

[0129] Specifically, the temperature range setting unit 107 is used to set a certain temperature range above and below the temperature of the first crystal based on the operating temperature range specified by the frequency doubling crystal 101. The specified operating temperature range of the frequency doubling crystal is the temperature range within which the frequency doubling crystal is stable and can generate frequency-doubled light output. For example, if the frequency doubling crystal A is stable in the range of -30℃ to 50℃, then its specified operating temperature range is -30℃ to 50℃.

[0130] The approximate temperature difference interval is 0.5 to 2°C, preferably 1°C. For example, assuming the frequency doubling crystal 101 has a specified operating temperature range of -30°C to 50°C, the power detection and recording unit 105 starts measuring the output frequency doubling optical power from -30°C. The temperature control device 104 adjusts the temperature of the frequency doubling crystal every 1°C. Then, the power detection and recording unit 105 sequentially measures and records the output frequency doubling optical power at -29°C, -28°C, -27°C...49°C, and 50°C.

[0131] Preferably, in order to obtain an accurate correspondence between temperature and output frequency-doubled optical power, the time for each temperature adjustment and recording, as well as the detection time for the output frequency-doubled optical power, shall not exceed 1ms.

[0132] like Figure 10 As shown, the temperature control device 104 includes multiple temperature measurement modules 124 and an averaging module 114; wherein

[0133] To avoid the influence of the laser on the temperature measurement module 124, the plurality of temperature measurement modules 124 are respectively attached to the surface of the plurality of non-light-transmitting parts of the frequency doubling crystal 101 for measuring the temperature of the frequency doubling crystal 101;

[0134] The averaging module 114 averages the multiple temperatures obtained by the multiple temperature measurement modules to obtain a more accurate temperature as the temperature of the frequency doubling crystal 101.

[0135] For example, at least three temperature monitoring points are provided at the non-light-transmitting positions of the frequency doubling crystal 101 to facilitate more accurate detection of the crystal's actual temperature and real-time feedback to the temperature compensation device 106. Since the input fundamental frequency light irradiation causes a higher temperature at the light-transmitting position of the frequency doubling crystal, setting the temperature monitoring points at the non-light-transmitting positions helps obtain a more accurate temperature reading for the frequency doubling crystal. For example, a thermal coupler can be attached to the crystal surface to detect the crystal surface temperature, or a far-infrared thermal imager can be used to detect the crystal surface temperature. After measuring the temperatures at multiple temperature monitoring points, the averaging module 114 performs an average to obtain a more accurate crystal temperature.

[0136] The power detection and recording unit 105 is used to record the output frequency-doubled optical power of the frequency-doubled crystal 101 at different temperatures, and selects the temperature corresponding to the maximum value of the output frequency-doubled optical power as the first crystal temperature corresponding to the current power of the input fundamental frequency light.

[0137] Figure 3 A graph showing the functional relationship between the frequency doubling crystal temperature and the output frequency doubling light power for an input fundamental frequency light of 82W is presented. The horizontal axis represents the frequency doubling crystal temperature, and the vertical axis represents the output frequency doubling light power. As can be seen from the graph, the output frequency doubling light power varies at different frequency doubling crystal temperatures for an input fundamental frequency light of 82W. A series of frequency doubling crystal temperatures and output frequency doubling light powers are obtained with a rough temperature difference interval of 1℃. For example, point 130 corresponds to 219℃, point 110 corresponds to 220℃, and point 140 corresponds to 221℃. The temperature control device 104 roughly adjusts the frequency doubling crystal temperature. It is measured that when the frequency doubling crystal temperature is 220℃, i.e., point 110, the maximum output frequency doubling light power is 42.9W. Therefore, 220℃ is the first crystal temperature for an input fundamental frequency light of 82W (i.e., the roughly optimal crystal temperature for obtaining a larger output frequency doubling light power).

[0138] like Figure 11 As shown, the power detection and recording unit 105 includes: a beam splitter 1321, a filtering and attenuation device 1322, and a detector 1323; wherein:

[0139] The beam splitter 1321 is used to split the frequency-doubled optical signal output after passing through the frequency-doubled crystal 101 into two or more beams according to a certain ratio. The beam splitter is a type of coated glass. One or more thin films are coated on the surface of the optical glass. When a beam of light is projected onto the coated glass, it is split into two or more beams through reflection and refraction. Generally, they are divided into cubic and planar types.

[0140] The filtering and attenuation device 1322 is used to filter and attenuate the separated optical signal to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected.

[0141] The detector 1323 is used to measure and record the power of the frequency-doubled optical signal to be detected to obtain the actual output frequency-doubled optical power.

[0142] For example, the output frequency-doubled optical signal is split into a beam with 1% intensity using a beam splitter 1321; the filtering and attenuation device 1322 filters and attenuates the split optical signal to remove noise signals and obtain a low-power pure optical signal, which is used as the frequency-doubled optical signal to be detected; the detector 1323 measures and records the power of the frequency-doubled optical signal to be detected, and calculates the actual output frequency-doubled optical power according to the beam splitting ratio and filtering efficiency.

[0143] The fundamental frequency light generator 109 is also used to sequentially input the input fundamental frequency light of different powers into the frequency doubling crystal 101 at certain power intervals, and the temperature control device 104 and the power detection and recording unit 105 obtain the first crystal temperature corresponding to different input fundamental frequency light powers.

[0144] The characteristic curve fitting module is used to perform curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, establish a functional relationship, and obtain the characteristic curve.

[0145] The characteristic curve reading unit 103 is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve.

[0146] For example, the current power is 82W, and the characteristic curve reading unit 103 reads from... Figure 4 The characteristic curve shown can be read as point 110, and its corresponding vertical axis indicates that the temperature of the first crystal is 220℃.

[0147] When the device 100 is in operation, after the current input fundamental frequency optical power changes, the first crystal temperature corresponding to the current power, i.e. the rough optimal crystal temperature, can be easily and quickly read from the characteristic curve in real time, without the need to perform the above series of measurements and records.

[0148] The temperature control device 104 is also used to measure the temperature of the frequency doubling crystal and adjust the temperature of the frequency doubling crystal 101 within a certain temperature range above and below the first crystal temperature with a precise temperature difference interval. The precise temperature difference interval is 0.005 to 0.02℃.

[0149] The power detection and recording unit 105 is used to detect and record the output frequency-doubled optical power of the frequency-doubled crystal 101 at different temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light.

[0150] For example, assuming the current power is 50W, the characteristic curve reading unit 103 reads from the characteristic curve that the first crystal temperature corresponding to the current power of 50W is 25℃, and the temperature range above and below the first crystal temperature is 24℃~26℃. Then the temperature control device 104 adjusts the first crystal temperature from 24℃ to 26℃ in intervals of 0.01℃. The power detection and recording unit 105 detects and records the output frequency doubling optical power corresponding to 200 first crystal temperatures, namely 24℃, 24.01℃, 24.02℃...25.98℃, 25.99℃ and 30℃, and selects the maximum value of 25W, corresponding to 24.78℃, as the second crystal temperature.

[0151] For example, the characteristic curve reading unit 103 reads from... Figure 4 From this, we can deduce that the temperature of the first crystal corresponding to the current power of 82W is 220℃. Figure 3 As shown, taking ΔT as 1℃, the temperature range of 220℃±1℃ is 219℃~221℃. With intervals of 0.01℃, the temperature control device 104 adjusts the temperature sequentially from 219℃ to 221℃. The power detection and recording unit 105 detects the output frequency-doubled optical power, obtaining a maximum output frequency-doubled optical power of 43W, corresponding to a frequency-doubled crystal temperature of 220.45℃. Figure 3 The midpoint is 120°C, meaning the temperature of the second crystal is 220.45°C.

[0152] The temperature compensation device 106 is used to actively follow and compensate the temperature of the frequency doubling crystal 101 based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal 101 at the second crystal temperature.

[0153] Regardless of the factors affecting the temperature change of the frequency doubling crystal, the temperature of the frequency doubling crystal will be actively compensated by the temperature compensation device 106 in real time to the second crystal temperature, so as to ensure that the maximum output frequency doubling optical power is generated under the current frequency doubling crystal and current angle conditions. For example, the temperature compensation device 106 is also used to actively compensate the temperature of the frequency doubling crystal 101 when the external ambient temperature of the frequency doubling crystal 101 changes, and control the temperature of the frequency doubling crystal 101 at the second crystal temperature.

[0154] The device 100 further includes a triggering unit 108, which is used to re-trigger the following operation when the current power of the input fundamental frequency light changes:

[0155] The characteristic curve reading unit 103 determines the corresponding first crystal temperature for the current power of the input fundamental frequency light through the characteristic curve;

[0156] The temperature control device 104 measures the temperature of the frequency doubling crystal 101 and adjusts the temperature of the frequency doubling crystal 101 within a certain temperature range above and below the temperature of the first crystal with precise temperature difference intervals.

[0157] The power detection and recording unit 105 detects and records the output frequency-doubled optical power of the frequency-doubled crystal 101 at different temperatures, and selects the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light; and

[0158] The temperature compensation device 106 actively follows and compensates the temperature of the frequency doubling crystal 101 based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and controls the temperature of the frequency doubling crystal 101 at the second crystal temperature.

[0159] When the current power of the input fundamental frequency light changes, the characteristic curve reading unit 103 first reads the first crystal temperature corresponding to the current power directly from the characteristic curve in real time, and then activates the trigger unit 108. That is, within a more precise small range (a certain temperature range above and below the first crystal temperature), the second crystal temperature is determined using a smaller temperature interval (precise temperature difference interval). The advantage of this device is that it eliminates the need to spend time searching for the second crystal temperature over a large range during device operation. Instead, the first crystal temperature corresponding to different input fundamental frequency light powers is predetermined, and the second crystal temperature is determined directly within a small range, greatly saving the determination time of the second crystal temperature, improving the control accuracy of the frequency doubling crystal temperature, and enhancing the stability of the system. At the same time, when the input fundamental frequency light power changes, the second crystal temperature is obtained in the shortest time to meet the active following compensation requirement of the frequency doubling crystal temperature under different input fundamental frequency light powers. The laser system can quickly reach a steady state during power switching, realizing precise dynamic control of the frequency doubling system. Based on the second crystal temperature, that is, the precise optimal crystal temperature, the frequency doubling crystal temperature is actively followed and compensated in real time, which can meet the working requirements under different ambient temperatures and improve the environmental adaptability of the device.

[0160] This invention also provides another laser frequency doubling device based on active temperature following compensation. Figure 8 This is a schematic diagram of a laser frequency doubling device 200 based on active temperature following compensation provided in an embodiment of the present invention, wherein straight lines represent signal transmission, dashed lines represent beam transmission, and arrows represent the transmission direction.

[0161] This device 200 and Figure 7The difference in device 100 lies in the determination of the second crystal temperature. Considering that the determination of the second crystal temperature is achieved by directly adjusting the control parameters of the temperature control device 104 and detecting changes in the crystal temperature to indirectly adjust the frequency doubling crystal temperature, multiple feedback cycles may be required to stabilize the frequency doubling crystal temperature at a predetermined value, resulting in a long adjustment time each time. Since the control parameters of the temperature control device 104 and the frequency doubling crystal temperature exhibit a linear relationship within a small range when the ambient temperature is relatively stable for a short period, the corresponding frequency doubling crystal temperature can be indirectly calculated by adjusting the control parameters of the temperature control device 104 through the control parameter adjustment unit 202. To further save time in determining the second crystal temperature, this device 200 uses the control parameter adjustment unit 202 to directly adjust the control parameters to find the maximum output frequency doubling optical power to determine the precise control parameters. Finally, the temperature control device 104 measures the corresponding frequency doubling crystal temperature under the precise control parameters as the second crystal temperature corresponding to the current power of the input fundamental frequency light. The device 200 does not require the temperature control device 104 to accurately detect and control the specific values ​​of the temperature of the frequency doubling crystal 101 at each temperature interval, nor does it require the power detection and recording unit 105 to detect the output frequency doubling optical power corresponding to the temperature of the frequency doubling crystal. Instead, it only requires the power detection and recording unit 105 to detect the output frequency doubling optical power corresponding to each control parameter.

[0162] like Figure 8 As shown, the device 200 provided in this embodiment includes: a fundamental frequency optical generator 109, a frequency doubling crystal 101, a characteristic curve acquisition unit 102, a characteristic curve reading unit 103, a temperature range setting unit 107, a temperature control device 104, a control parameter adjustment unit 202, a power detection and recording unit 105, and a temperature compensation device 106; wherein:

[0163] The fundamental frequency light generator 109 is used to generate input fundamental frequency light that is input to the frequency doubling crystal 101.

[0164] The frequency doubling crystal 101 is a type of nonlinear optical crystal used for the frequency doubling effect. Generally, the frequency doubling crystal 101 is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

[0165] The feature curve acquisition unit 102 is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve, and store the feature curve.

[0166] The characteristic curve acquisition unit 102 is also used to re-establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature for different frequency doubling crystals 101, and fit the corresponding characteristic curve.

[0167] Specifically, the feature curve acquisition unit 102 includes a feature curve fitting module. The fundamental frequency light generator 109 is used to input a certain power of input fundamental frequency light into the frequency doubling crystal 101, such as... Figure 9 As shown, the fundamental frequency light generator 109 includes a laser for emitting fundamental frequency light and a collimating focusing lens 1121, which is used to collimate and focus the input fundamental frequency light of a certain power at the center of the frequency doubling crystal 101. The substrate of the collimating focusing lens 1121 is generally fused silica material, and the lens can be a plano-convex lens or a crescent lens. The lens design can be monolithic, multi-element, or aspherical.

[0168] The temperature control device 104 is used to adjust the temperature of the frequency doubling crystal 101 within the specified operating temperature range of the frequency doubling crystal 101 by a rough temperature difference interval. The temperature control device 104 is a heating furnace, a semiconductor temperature controller, a heat pump or a refrigeration compressor, and the rough temperature difference interval is 0.5 to 2°C.

[0169] The power detection and recording unit 105 is used to record the output frequency-doubled optical power of the frequency-doubled crystal 101 at different temperatures, and selects the temperature corresponding to the maximum value of the output frequency-doubled optical power as the first crystal temperature corresponding to the current power of the input fundamental frequency light. The time for each temperature adjustment and recording, as well as the detection time of the output frequency-doubled optical power, does not exceed 1ms.

[0170] like Figure 11 As shown, the power detection and recording unit 105 includes: a beam splitter 1321, a filtering and attenuation device 1322, and a detector 1323; wherein:

[0171] The beam splitter 1321 is used to split the frequency-doubled optical signal output after passing through the frequency-doubled crystal 101 into two or more beams according to a certain ratio. The beam splitter is a type of coated glass. One or more thin films are coated on the surface of the optical glass. When a beam of light is projected onto the coated glass, it is split into two or more beams through reflection and refraction. Generally, they are divided into cubic and planar types.

[0172] The filtering and attenuation device 1322 is used to filter and attenuate the separated optical signal to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected.

[0173] The detector 1323 is used to measure and record the power of the frequency-doubled optical signal to be detected to obtain the actual output frequency-doubled optical power.

[0174] The fundamental frequency light generator 109 is also used to sequentially input the input fundamental frequency light of different powers into the frequency doubling crystal 101 at certain power intervals, and the temperature control device 104 and the power detection and recording unit 105 obtain the first crystal temperature corresponding to different input fundamental frequency light powers.

[0175] The characteristic curve fitting module is used to perform curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, establish a functional relationship, and obtain the characteristic curve.

[0176] The characteristic curve reading unit 103 is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve;

[0177] The temperature range setting unit 107 is used to determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal.

[0178] Specifically, the temperature range setting unit 107 is used to determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal, based on the operating temperature range specified by the frequency doubling crystal 101.

[0179] The temperature control device 104 is used to measure the temperature of the frequency doubling crystal and record the upper limit control parameters corresponding to the temperature control device 104 when the frequency doubling crystal 101 is controlled at the upper limit temperature, and record the lower limit control parameters corresponding to the temperature control device 104 when the frequency doubling crystal 101 is controlled at the lower limit temperature.

[0180] The temperature control device 104 is a heating furnace, a semiconductor temperature controller, a heat pump, or a refrigeration compressor; wherein when a heating furnace is used to adjust the temperature of the frequency doubling crystal 101, the control parameter is current or resistance; when a semiconductor temperature controller is used to adjust the temperature of the frequency doubling crystal 101, the control parameter is current; when a heat pump or a compressor is used to adjust the temperature of the frequency doubling crystal 101, the control parameter is duty cycle, or it can be controlling its operating power.

[0181] like Figure 10 As shown, the temperature control device 104 includes multiple temperature measurement modules 124 and an averaging module 114; wherein

[0182] The plurality of temperature measurement modules 124 are respectively attached to the surface of the plurality of non-light-transmitting parts of the frequency doubling crystal 101, and are used to measure the temperature of the frequency doubling crystal 101;

[0183] The averaging module 114 takes the average of the multiple temperatures obtained by the multiple temperature measurement modules as the temperature of the frequency doubling crystal 101.

[0184] The control parameter adjustment unit 202 is used to change the control parameter of the temperature control device 104 from the lower limit control parameter to the upper limit control parameter;

[0185] Specifically, such as Figure 12As shown, the control parameter adjustment unit 202 includes an interval division module 212 and an interval adjustment module 222; wherein

[0186] The interval division module 212 is used to divide the interval between the upper limit control parameter and the lower limit control parameter into multiple intervals. Preferably, the interval between the upper limit control parameter and the lower limit control parameter is divided into 100 to 200 intervals.

[0187] The interval adjustment module 222 is used to cause the control parameters of the temperature control device 104 to change sequentially from the lower limit control parameter to the upper limit control parameter according to the interval points of the interval, while the power detection and recording unit 105 measures the output frequency-doubled optical power. For example, the interval division module 212 divides the interval between the lower limit control parameter 2A and the upper limit control parameter 4A into 200 intervals, so that the control parameters of the temperature control device change sequentially from the lower limit control parameter 2A to the upper limit control parameter 4A according to the interval points 2A, 2.01A, 2.02A...4.99A, 4A, while the power detection and recording unit 105 measures the output frequency-doubled optical power.

[0188] like Figure 12 As shown, the control parameter adjustment unit 202 includes a continuous adjustment module 232, which is used to make the control parameters of the temperature control device 104 continuously change from the lower limit control parameter to the upper limit control parameter, while measuring the output frequency doubling optical power.

[0189] The power detection and recording unit 105 is used to detect and record the output frequency-doubled optical power, and select the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter.

[0190] The temperature control device 104 is also used to measure the temperature of the frequency doubling crystal 101 corresponding to the precise control parameters as a second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0191] The temperature compensation device 106 is used to actively follow and compensate the temperature of the frequency doubling crystal 101 based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal 101 at the second crystal temperature.

[0192] The temperature compensation device 106 is also used to actively follow and compensate the temperature of the frequency doubling crystal 101 when the external ambient temperature of the frequency doubling crystal 101 changes, and control the temperature of the frequency doubling crystal 101 at the temperature of the second crystal.

[0193] For example, the characteristic curve reading unit 103 reads from the characteristic curve that the temperature of the first crystal corresponding to the current power of 82W is 220℃, and uses a heating furnace to adjust the temperature of the frequency doubling crystal 101, with the control parameter being current. The temperature range setting unit 107 selects a certain temperature range centered on the first crystal temperature of 220℃ as 219℃~221℃, with an upper limit temperature of 221℃ and a lower limit temperature of 219℃; for example... Figure 6 As shown, when the frequency doubling crystal 101 is controlled at the lower limit temperature of 219°C, the lower limit control parameter corresponding to the temperature control device 104 is recorded as 2.19A; when the frequency doubling crystal 101 is controlled at the upper limit temperature of 221°C, the upper limit control parameter corresponding to the temperature control device 104 is recorded as 2.21A; the continuous adjustment module 232 causes the current of the heating furnace to continuously change from the lower limit control parameter 2.19A to the upper limit control parameter 2.21A, while the power detection and recording unit 105 detects and records the output frequency doubling optical power, and selects the output frequency doubling optical power. The maximum value of 43W, corresponding to a current of 2.204A, is used as the precise control parameter, i.e., point 120 in the figure. The temperature control device 104 measures the frequency doubling crystal temperature of 220.45℃ corresponding to the precise control parameter of 2.204A as the second crystal temperature corresponding to the current power of the input fundamental frequency light. Based on the second crystal temperature of 220.45℃ corresponding to the current power of the input fundamental frequency light of 82W, the temperature compensation device 106 actively follows and compensates the temperature of the frequency doubling crystal, controlling the temperature of the frequency doubling crystal at the second crystal temperature of 220.45℃. During the active following and compensation process, it is necessary to measure the temperature of the frequency doubling crystal 101 in real time and adjust the control parameters to ensure that the temperature of the frequency doubling crystal 101 is not affected by the external environment.

[0194] The device 200 further includes a triggering unit 108, which is used to re-trigger the following operation when the current power of the input fundamental frequency light changes:

[0195] The characteristic curve reading unit 103 determines the corresponding first crystal temperature for the current power of the input fundamental frequency light through the characteristic curve;

[0196] The temperature range setting unit 107 determines the upper and lower limits of a certain temperature range centered on the temperature of the first crystal.

[0197] When the temperature control device 104 measures the temperature of the frequency doubling crystal and controls the frequency doubling crystal at the upper limit temperature, it records the upper limit control parameter corresponding to the temperature control device; when the frequency doubling crystal is controlled at the lower limit temperature, it records the lower limit control parameter corresponding to the temperature control device.

[0198] The control parameter adjustment unit 202 causes the control parameter of the temperature control device to change from the lower limit control parameter to the upper limit control parameter;

[0199] The power detection and recording unit 105 detects and records the output frequency-doubled optical power, and selects the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter.

[0200] The temperature control device 104 measures the frequency doubling crystal temperature corresponding to the precise control parameters as a second crystal temperature corresponding to the current power of the input fundamental frequency light; and

[0201] The temperature compensation device 106 actively follows and compensates the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and controls the temperature of the frequency doubling crystal at the second crystal temperature.

[0202] It should be noted that although the operation of the laser frequency doubling method based on temperature active following compensation of the present invention is described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all of the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0203] Furthermore, although several units, modules, or sub-modules of the laser frequency doubling device based on active temperature following compensation have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules described above can be embodied in a single module. Conversely, the features and functions of a single module described above can be further divided and embodied by multiple modules.

[0204] While the spirit and principles of the invention have been described with reference to several specific embodiments, it should be understood that the invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that features in these aspects cannot be combined for benefit; such division is merely for ease of description. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0205] This invention provides:

[0206] 1. A laser frequency doubling method based on active temperature following compensation, characterized in that the method comprises:

[0207] Establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fit the characteristic curve.

[0208] For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve;

[0209] Within a certain temperature range above and below the temperature of the first crystal, the temperature of the frequency doubling crystal is adjusted with precise temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is detected and recorded.

[0210] The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the second crystal temperature corresponding to the current power of the input fundamental frequency optical power;

[0211] Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

[0212] 2. The laser frequency doubling method according to item 1, characterized in that the step of establishing the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fitting the characteristic curve, specifically includes:

[0213] A certain power of input fundamental frequency light is input into the frequency doubling crystal;

[0214] Within the specified operating temperature range of the frequency doubling crystal, the temperature of the frequency doubling crystal is adjusted at rough temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is recorded;

[0215] The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the first crystal temperature corresponding to the current power of the input fundamental frequency light;

[0216] Different power input fundamental frequency light is sequentially input into the frequency doubling crystal at certain power intervals to obtain a first crystal temperature corresponding to different input fundamental frequency light power;

[0217] The characteristic curve is obtained by performing curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures to establish a functional relationship.

[0218] 3. The laser frequency doubling method according to item 1 or item 2, characterized in that the time for each adjustment and recording of the temperature and the detection time of the output frequency-doubled optical power does not exceed 1ms.

[0219] 4. The laser frequency doubling method according to item 2, characterized in that the rough temperature difference interval is 0.5 to 2°C;

[0220] The precise temperature difference interval is 0.005 to 0.02℃.

[0221] 5. The laser frequency doubling method according to item 1 or 2, characterized in that the temperature of the frequency doubling crystal is adjusted by using a heating furnace, a semiconductor temperature controller, a heat pump or a refrigeration compressor.

[0222] 6. The laser frequency doubling method according to item 1 or item 2, characterized in that the method further comprises:

[0223] Based on the specified operating temperature range of the frequency doubling crystal, a certain temperature range is set above and below the temperature of the first crystal.

[0224] 7. The laser frequency doubling method according to item 1 or item 2, characterized in that the method further comprises:

[0225] For different frequency doubling crystals, the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature is re-established, and the corresponding characteristic curve is obtained by fitting.

[0226] 8. The laser frequency doubling method according to item 1 or 2, wherein the frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

[0227] 9. The laser frequency doubling method according to item 2, characterized in that the step of inputting a certain power of input fundamental frequency light into the frequency doubling crystal specifically comprises: collimating and focusing the certain power of input fundamental frequency light at the center of the frequency doubling crystal.

[0228] 10. The laser frequency doubling method according to item 1 or item 2, characterized in that the method further comprises:

[0229] A beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal into a certain proportion.

[0230] The separated optical signal is filtered and attenuated to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected.

[0231] The power of the frequency-doubled optical signal to be detected is measured and recorded to obtain the actual output frequency-doubled optical power.

[0232] 11. The laser frequency doubling method according to item 1 or item 2, characterized in that the method further comprises:

[0233] The temperature of the frequency doubling crystal is measured at multiple non-light-transmitting points to obtain multiple temperatures, and the average value of these values ​​is taken as the temperature of the frequency doubling crystal.

[0234] 12. The laser frequency doubling method according to item 1 or item 2, characterized in that the method further comprises:

[0235] When the external ambient temperature of the frequency doubling crystal changes, the temperature of the frequency doubling crystal is actively compensated to control the temperature of the frequency doubling crystal at the temperature of the second crystal.

[0236] 13. The laser frequency doubling method according to item 1 or item 2, characterized in that the method further comprises:

[0237] When the current power of the input fundamental frequency light changes, the following steps are repeated:

[0238] For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve;

[0239] Within a certain temperature range above and below the temperature of the first crystal, the temperature of the frequency doubling crystal is adjusted with precise temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is detected and recorded.

[0240] The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the second crystal temperature corresponding to the current power of the input fundamental frequency optical power;

[0241] Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

[0242] 14. A laser frequency doubling method based on active temperature following compensation, characterized in that the method includes:

[0243] Establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fit the characteristic curve.

[0244] For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve;

[0245] Determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal;

[0246] When the frequency doubling crystal is controlled at the upper limit temperature, the upper limit control parameters corresponding to the temperature control device are recorded.

[0247] When the frequency doubling crystal is controlled at the lower limit temperature, the corresponding lower limit control parameters of the temperature control device are recorded.

[0248] This causes the control parameters of the temperature control device to change from the lower limit control parameter to the upper limit control parameter, while simultaneously detecting and recording the output frequency-doubled optical power;

[0249] The control parameter corresponding to the maximum value of the output frequency-doubled optical power is selected as the precise control parameter, and the frequency-doubled crystal temperature corresponding to the precise control parameter is measured as the second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0250] Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

[0251] 15. The laser frequency doubling method according to claim 14, characterized in that the method further comprises:

[0252] The steps of changing the control parameters of the temperature control device from the lower limit control parameter to the upper limit control parameter, and simultaneously detecting and recording the output frequency-doubled optical power, specifically include:

[0253] The interval between the upper limit control parameter and the lower limit control parameter is divided into multiple intervals;

[0254] The control parameters of the temperature control device are changed sequentially from the lower limit control parameter to the upper limit control parameter at intervals within the range, while the output frequency-doubled optical power is measured.

[0255] 16. The laser frequency doubling method according to item 14 or 15, characterized in that the step of establishing the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fitting the characteristic curve specifically includes:

[0256] A certain power of input fundamental frequency light is input into the frequency doubling crystal;

[0257] Within the specified operating temperature range of the frequency doubling crystal, the temperature of the frequency doubling crystal is adjusted at rough temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is recorded;

[0258] The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the first crystal temperature corresponding to the current power of the input fundamental frequency light;

[0259] Different power input fundamental frequency light is sequentially input into the frequency doubling crystal at certain power intervals to obtain a first crystal temperature corresponding to different input fundamental frequency light power;

[0260] The characteristic curve is obtained by performing curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures to establish a functional relationship.

[0261] 17. The laser frequency doubling method according to item 14 or 15, characterized in that the adjustment and recording time of the control parameters and the detection time of the output frequency-doubled optical power each time do not exceed 1 ms.

[0262] 18. The laser frequency doubling method according to item 16, characterized in that the coarse temperature difference interval is 0.5 to 2°C;

[0263] The interval between the upper limit control parameter and the lower limit control parameter is divided into 100 to 200 intervals.

[0264] 19. The laser frequency doubling method according to item 14 or 15, characterized in that:

[0265] When a heating furnace is used to adjust the temperature of the frequency doubling crystal, the control parameter is current or resistance;

[0266] When a semiconductor temperature controller is used to adjust the temperature of the frequency doubling crystal, the control parameter is current;

[0267] When a heat pump or a compressor is used to regulate the temperature of the frequency doubling crystal, the control parameter is the duty cycle.

[0268] 20. The laser frequency doubling method according to claim 14 or 15, characterized in that the method further comprises:

[0269] Based on the specified operating temperature range of the frequency doubling crystal, the upper and lower limits of a certain temperature range centered on the temperature of the first crystal are determined.

[0270] 21. The laser frequency doubling method according to item 14 or 15, characterized in that the method further comprises:

[0271] For different frequency doubling crystals, the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature is re-established, and the corresponding characteristic curve is obtained by fitting.

[0272] 22. The laser frequency doubling method according to item 14 or 15, wherein the frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

[0273] 23. The laser frequency doubling method according to item 16, characterized in that the step of inputting a certain power of input fundamental frequency light into the frequency doubling crystal specifically comprises: collimating and focusing the certain power of input fundamental frequency light at the center of the frequency doubling crystal.

[0274] 24. The laser frequency doubling method according to item 14 or 15, characterized in that the method further comprises:

[0275] A beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal into a certain proportion.

[0276] The separated optical signal is filtered and attenuated to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected.

[0277] The power of the frequency-doubled optical signal to be detected is measured and recorded to obtain the actual output frequency-doubled optical power.

[0278] 25. The laser frequency doubling method according to claim 14 or 15, characterized in that the method further comprises:

[0279] The temperature of the frequency doubling crystal is measured at multiple non-light-transmitting points to obtain multiple temperatures, and the average value of these values ​​is taken as the temperature of the frequency doubling crystal.

[0280] 26. The laser frequency doubling method according to item 14 or 15, characterized in that the method further comprises:

[0281] When the external ambient temperature of the frequency doubling crystal changes, the temperature of the frequency doubling crystal is actively compensated to control the temperature of the frequency doubling crystal at the temperature of the second crystal.

[0282] 27. The laser frequency doubling method according to item 14 or 15, characterized in that the method further comprises:

[0283] When the current power of the input fundamental frequency light changes, the following steps are repeated:

[0284] For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve;

[0285] Determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal;

[0286] When the frequency doubling crystal is controlled at the upper limit temperature, the upper limit control parameters corresponding to the temperature control device are recorded.

[0287] When the frequency doubling crystal is controlled at the lower limit temperature, the corresponding lower limit control parameters of the temperature control device are recorded.

[0288] This causes the control parameters of the temperature control device to change from the lower limit control parameter to the upper limit control parameter, while simultaneously detecting and recording the output frequency-doubled optical power;

[0289] The control parameter corresponding to the maximum value of the output frequency-doubled optical power is selected as the precise control parameter, and the frequency-doubled crystal temperature corresponding to the precise control parameter is measured as the second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0290] Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

[0291] 28. The laser frequency doubling method according to claim 14 or 15, characterized in that the method further comprises:

[0292] The steps of changing the control parameters of the temperature control device from the lower limit control parameter to the upper limit control parameter, and simultaneously detecting and recording the output frequency-doubled optical power, specifically include:

[0293] This causes the control parameters of the temperature control device to continuously change from the lower limit control parameter to the upper limit control parameter, while simultaneously measuring the output frequency-doubled optical power.

[0294] 29. A laser frequency doubling device based on active temperature following compensation, characterized in that the device comprises: a fundamental frequency light generator, a frequency doubling crystal, a characteristic curve acquisition unit, a characteristic curve reading unit, a temperature control device, a power detection and recording unit, and a temperature compensation device; wherein...

[0295] The fundamental frequency light generator is used to generate input fundamental frequency light that is input to the frequency doubling crystal;

[0296] The feature curve acquisition unit is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve, and store the feature curve.

[0297] The characteristic curve reading unit is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve;

[0298] The temperature control device is used to measure the temperature of the frequency doubling crystal and adjust the temperature of the frequency doubling crystal at precise temperature difference intervals within a certain temperature range above and below the temperature of the first crystal.

[0299] The power detection and recording unit is used to detect and record the output frequency-doubled optical power of the frequency-doubled crystal at different frequency-doubled crystal temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0300] The temperature compensation device is used to actively follow and compensate the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal at the second crystal temperature.

[0301] 30. The laser frequency doubling device according to item 29, wherein the characteristic curve acquisition unit includes a characteristic curve fitting module;

[0302] The fundamental frequency optical generator inputs a certain power of input fundamental frequency light into the frequency doubling crystal;

[0303] The temperature control device is also used to adjust the temperature of the frequency doubling crystal within the specified operating temperature range of the frequency doubling crystal at rough temperature difference intervals.

[0304] The power detection and recording unit is also used to record the output frequency-doubled optical power of the frequency-doubled crystal at different temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the first crystal temperature corresponding to the current power of the input fundamental frequency light.

[0305] The fundamental frequency light generator is also used to sequentially input the input fundamental frequency light of different powers into the frequency doubling crystal at certain power intervals, and the temperature control device and the power detection and recording unit obtain the first crystal temperature corresponding to different input fundamental frequency light powers;

[0306] The characteristic curve fitting module is used to perform curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, establish a functional relationship, and obtain the characteristic curve.

[0307] 31. The laser frequency doubling device according to item 29 or 30, characterized in that the time for each adjustment and recording of the temperature and the detection time of the output frequency-doubled optical power does not exceed 1 ms.

[0308] 32. The laser frequency doubling device according to item 30, characterized in that the coarse temperature difference interval is 0.5 to 2°C;

[0309] The precise temperature difference interval is 0.005 to 0.02℃.

[0310] 33. The laser frequency doubling device according to claim 29 or 30, wherein the temperature control device is a heating furnace, a semiconductor temperature controller, a heat pump or a refrigeration compressor.

[0311] 34. The laser frequency doubling device according to item 29 or 30, characterized in that the device further comprises: a temperature range setting unit, which is used to set a certain temperature range above and below the temperature of the first crystal based on the specified operating temperature range of the frequency doubling crystal.

[0312] 35. The laser frequency doubling device according to item 29 or 30, characterized in that the characteristic curve acquisition unit is further used to re-establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature for different frequency doubling crystals, and fit the corresponding characteristic curve.

[0313] 36. The laser frequency doubling device according to claim 29 or 30, wherein the frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

[0314] 37. The laser frequency doubling device according to claim 30, characterized in that the fundamental frequency light generator includes a collimating focusing lens, which is used to collimate and focus the input fundamental frequency light of a certain power at the center of the frequency doubling crystal.

[0315] 38. The laser frequency doubling device according to claim 29 or 30, characterized in that the power detection and recording unit comprises: a beam splitter, a filtering and attenuation device, and a detector; wherein

[0316] The beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal according to a certain ratio;

[0317] The filtering and attenuation device is used to filter and attenuate the separated optical signal to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected.

[0318] The detector is used to measure and record the power of the frequency-doubled optical signal to be detected to obtain the actual output frequency-doubled optical power.

[0319] 39. The laser frequency doubling device according to claim 29 or 30, characterized in that the temperature control device comprises a plurality of temperature measurement modules and an averaging module; wherein

[0320] The multiple temperature measurement modules are respectively attached to the surface of multiple non-light-transmitting parts of the frequency doubling crystal, and are used to measure the temperature of the frequency doubling crystal;

[0321] The averaging module takes the average of the multiple temperatures obtained by the multiple temperature measurement modules as the temperature of the frequency doubling crystal.

[0322] 40. The laser frequency doubling device according to item 29 or 30, characterized in that the temperature compensation device is further used to actively follow and compensate the temperature of the frequency doubling crystal when the external ambient temperature of the frequency doubling crystal changes, and control the temperature of the frequency doubling crystal at the temperature of the second crystal.

[0323] 41. The laser frequency doubling device according to claim 29 or 30, characterized in that the device further comprises a triggering unit for re-triggering when the current power of the input fundamental frequency light changes:

[0324] The characteristic curve reading unit determines the corresponding first crystal temperature for the current power of the input fundamental frequency light through the characteristic curve;

[0325] The temperature control device measures the temperature of the frequency doubling crystal and adjusts the temperature of the frequency doubling crystal at precise temperature difference intervals within a certain temperature range above and below the first crystal temperature.

[0326] The power detection and recording unit detects and records the output frequency-doubled optical power of the frequency-doubled crystal at different frequency-doubled crystal temperatures, and selects the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light; and

[0327] The temperature compensation device actively follows and compensates the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, thereby controlling the temperature of the frequency doubling crystal at the second crystal temperature.

[0328] 42. A laser frequency doubling device based on active temperature following compensation, characterized in that the device comprises: a fundamental frequency light generator, a frequency doubling crystal, a characteristic curve acquisition unit, a characteristic curve reading unit, a temperature range setting unit, a temperature control device, a control parameter adjustment unit, a power detection and recording unit, and a temperature compensation device; wherein...

[0329] The fundamental frequency light generator is used to generate input fundamental frequency light that is input to the frequency doubling crystal;

[0330] The feature curve acquisition unit is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve, and store the feature curve.

[0331] The characteristic curve reading unit is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve;

[0332] The temperature range setting unit is used to determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal.

[0333] The temperature control device is used to measure the temperature of the frequency doubling crystal and record the upper limit control parameter corresponding to the temperature control device when the frequency doubling crystal is controlled at the upper limit temperature, and record the lower limit control parameter corresponding to the temperature control device when the frequency doubling crystal is controlled at the lower limit temperature.

[0334] The control parameter adjustment unit is used to change the control parameter of the temperature control device from the lower limit control parameter to the upper limit control parameter;

[0335] The power detection and recording unit is used to detect and record the output frequency-doubled optical power, and select the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter.

[0336] The temperature control device is also used to measure the frequency doubling crystal temperature corresponding to the precise control parameters as a second crystal temperature corresponding to the current power of the input fundamental frequency light;

[0337] The temperature compensation device is used to actively follow and compensate the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal at the second crystal temperature.

[0338] 43. The laser frequency doubling device according to claim 42, characterized in that the control parameter adjustment unit comprises an interval division module and an interval adjustment module; wherein...

[0339] The interval division module is used to divide the interval between the upper limit control parameter and the lower limit control parameter into multiple intervals;

[0340] The interval adjustment module is used to make the control parameters of the temperature control device change sequentially from the lower limit control parameter to the upper limit control parameter according to the interval points of the interval, while measuring the output frequency doubling optical power.

[0341] 44. The laser frequency doubling device according to item 42 or 43, characterized in that the characteristic curve acquisition unit includes a characteristic curve fitting module;

[0342] The fundamental frequency optical generator is used to input a certain power of fundamental frequency optical light into the frequency doubling crystal;

[0343] The temperature control device is also used to adjust the temperature of the frequency doubling crystal within the specified operating temperature range of the frequency doubling crystal at rough temperature difference intervals.

[0344] The power detection and recording unit is also used to record the output frequency-doubled optical power of the frequency-doubled crystal at different temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the first crystal temperature corresponding to the current power of the input fundamental frequency light.

[0345] The fundamental frequency light generator is also used to sequentially input the input fundamental frequency light of different powers into the frequency doubling crystal at certain power intervals, and the temperature control device and the power detection and recording unit obtain the first crystal temperature corresponding to different input fundamental frequency light powers;

[0346] The characteristic curve fitting module is used to perform curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, establish a functional relationship, and obtain the characteristic curve.

[0347] 45. The laser frequency doubling device according to item 42 or 43, characterized in that the adjustment and recording time of the control parameters and the detection time of the output frequency-doubled optical power each time do not exceed 1 ms.

[0348] 46. ​​The laser frequency doubling device according to item 44, characterized in that the coarse temperature difference interval is 0.5 to 2°C;

[0349] The interval between the upper limit control parameter and the lower limit control parameter is divided into 100 to 200 intervals.

[0350] 47. The laser frequency doubling device according to claim 42 or 43, characterized in that the temperature control device is a heating furnace, a semiconductor temperature controller, a heat pump, or a refrigeration compressor; wherein...

[0351] When a heating furnace is used to adjust the temperature of the frequency doubling crystal, the control parameter is current or resistance;

[0352] When a semiconductor temperature controller is used to adjust the temperature of the frequency doubling crystal, the control parameter is current;

[0353] When a heat pump or a compressor is used to regulate the temperature of the frequency doubling crystal, the control parameter is the duty cycle.

[0354] 48. The laser frequency doubling device according to item 42 or 43, characterized in that the temperature range setting unit is used to determine the upper limit temperature and the lower limit temperature of a certain temperature range centered on the temperature of the first crystal, based on the operating temperature range specified by the frequency doubling crystal.

[0355] 49. The laser frequency doubling device according to item 42 or 43, characterized in that the characteristic curve acquisition unit is further used to re-establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature for different frequency doubling crystals, and fit the corresponding characteristic curve.

[0356] 50. The laser frequency doubling device according to claim 42 or 43, wherein the frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

[0357] 51. The laser frequency doubling device according to claim 44, characterized in that the fundamental frequency light generator includes a collimating focusing lens, which is used to collimate and focus the input fundamental frequency light of a certain power at the center of the frequency doubling crystal.

[0358] 52. The laser frequency doubling device according to claim 42 or 43, characterized in that the power detection and recording unit comprises: a beam splitter, a filtering and attenuation device, and a detector; wherein

[0359] The beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal according to a certain ratio;

[0360] The filtering and attenuation device is used to filter and attenuate the separated optical signal to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected.

[0361] The detector is used to measure and record the power of the frequency-doubled optical signal to be detected to obtain the actual output frequency-doubled optical power.

[0362] 53. The laser frequency doubling device according to claim 42 or 43, characterized in that the temperature control device comprises a plurality of temperature measurement modules and an averaging module; wherein

[0363] The multiple temperature measurement modules are respectively attached to the surface of multiple non-light-transmitting parts of the frequency doubling crystal, and are used to measure the temperature of the frequency doubling crystal;

[0364] The averaging module takes the average of the multiple temperatures obtained by the multiple temperature measurement modules as the temperature of the frequency doubling crystal.

[0365] 54. The laser frequency doubling device according to item 42 or 43, characterized in that the temperature compensation device is further used to actively follow and compensate the temperature of the frequency doubling crystal when the external ambient temperature of the frequency doubling crystal changes, and control the temperature of the frequency doubling crystal at the temperature of the second crystal.

[0366] 55. The laser frequency doubling device according to claim 42 or 43, characterized in that the device further comprises a triggering unit for re-triggering when the current power of the input fundamental frequency light changes:

[0367] The characteristic curve reading unit determines the corresponding first crystal temperature for the current power of the input fundamental frequency light through the characteristic curve;

[0368] The temperature range setting unit determines the upper and lower limits of a certain temperature range centered on the temperature of the first crystal.

[0369] When the temperature control device measures the temperature of the frequency doubling crystal and controls the frequency doubling crystal at the upper limit temperature, it records the upper limit control parameter corresponding to the temperature control device; when the frequency doubling crystal is controlled at the lower limit temperature, it records the lower limit control parameter corresponding to the temperature control device.

[0370] The control parameter adjustment unit causes the control parameter of the temperature control device to change from the lower limit control parameter to the upper limit control parameter;

[0371] The power detection and recording unit detects and records the output frequency-doubled optical power, and selects the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter.

[0372] The temperature control device measures the frequency doubling crystal temperature corresponding to the precise control parameters as a second crystal temperature corresponding to the current power of the input fundamental frequency light; and

[0373] The temperature compensation device actively follows and compensates the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, thereby controlling the temperature of the frequency doubling crystal at the second crystal temperature.

[0374] 56. The laser frequency doubling device according to claim 42 or 43, characterized in that the control parameter adjustment unit includes a continuous adjustment module, which is used to continuously change the control parameter of the temperature control device from the lower limit control parameter to the upper limit control parameter, while measuring the output frequency doubling optical power.

Claims

1. A laser frequency doubling method based on active temperature following compensation, characterized in that, The method includes: A functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature is established, and a characteristic curve is obtained by fitting. The first crystal temperature is a rough optimal temperature, that is, the temperature at which the output frequency-doubled optical power reaches its maximum value when the temperature is adjusted at a rough temperature difference interval within the specified operating temperature range of the frequency-doubled crystal under the current power of the input fundamental frequency optical power. For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve; Within a certain temperature range above and below the temperature of the first crystal, the temperature of the frequency doubling crystal is adjusted with precise temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is detected and recorded. The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the second crystal temperature corresponding to the current power of the input fundamental frequency optical power; Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

2. The laser frequency doubling method according to claim 1, characterized in that, The step of establishing a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fitting the characteristic curve, specifically includes: A certain power of input fundamental frequency light is input into the frequency doubling crystal; Within the specified operating temperature range of the frequency doubling crystal, the temperature of the frequency doubling crystal is adjusted at rough temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is recorded; The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the first crystal temperature corresponding to the current power of the input fundamental frequency light; Different power input fundamental frequency light is sequentially input into the frequency doubling crystal at certain power intervals to obtain a first crystal temperature corresponding to different input fundamental frequency light power; The characteristic curve is obtained by performing curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures to establish a functional relationship.

3. The laser frequency doubling method according to claim 1 or 2, characterized in that, The time for each temperature adjustment and recording, as well as the detection time for the output frequency-doubled optical power, shall not exceed 1ms.

4. The laser frequency doubling method according to claim 2, characterized in that, The approximate temperature difference interval is 0.5~2℃; The precise temperature difference interval is 0.005~0.02℃.

5. The laser frequency doubling method according to claim 1 or 2, characterized in that, The temperature of the frequency doubling crystal is regulated by a heating furnace, a semiconductor temperature controller, a heat pump, or a refrigeration compressor.

6. The laser frequency doubling method according to claim 1 or 2, characterized in that, The method further includes: Based on the specified operating temperature range of the frequency doubling crystal, a certain temperature range is set above and below the temperature of the first crystal.

7. The laser frequency doubling method according to claim 1 or 2, characterized in that, The method further includes: For different frequency doubling crystals, the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature is re-established, and the corresponding characteristic curve is obtained by fitting.

8. The laser frequency doubling method according to claim 1 or 2, characterized in that, The frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

9. The laser frequency doubling method according to claim 2, characterized in that, The specific steps of inputting a certain power of input fundamental frequency light into the frequency doubling crystal are as follows: collimating and focusing the input fundamental frequency light of a certain power at the center of the frequency doubling crystal.

10. The laser frequency doubling method according to claim 1 or 2, characterized in that, The method further includes: A beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal into a certain proportion. The separated optical signal is filtered and attenuated to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected. The power of the frequency-doubled optical signal to be detected is measured and recorded to obtain the actual output frequency-doubled optical power.

11. The laser frequency doubling method according to claim 1 or 2, characterized in that, The method further includes: The temperature of the frequency doubling crystal is measured at multiple non-light-transmitting points to obtain multiple temperatures, and the average value of these values ​​is taken as the temperature of the frequency doubling crystal.

12. The laser frequency doubling method according to claim 1 or 2, characterized in that, The method further includes: When the external ambient temperature of the frequency doubling crystal changes, the temperature of the frequency doubling crystal is actively compensated to control the temperature of the frequency doubling crystal at the temperature of the second crystal.

13. The laser frequency doubling method according to claim 1 or 2, characterized in that, The method further includes: When the current power of the input fundamental frequency light changes, the following steps are repeated: For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve; Within a certain temperature range above and below the temperature of the first crystal, the temperature of the frequency doubling crystal is adjusted with precise temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is detected and recorded. The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the second crystal temperature corresponding to the current power of the input fundamental frequency optical power; Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

14. A laser frequency doubling method based on active temperature following compensation, characterized in that, The method includes: A functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature is established, and a characteristic curve is obtained by fitting. The first crystal temperature is a rough optimal temperature, that is, the temperature at which the output frequency-doubled optical power reaches its maximum value when the temperature is adjusted at a rough temperature difference interval within the specified operating temperature range of the frequency-doubled crystal under the current power of the input fundamental frequency optical power. For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve; Determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal; When the frequency doubling crystal is controlled at the upper limit temperature, the upper limit control parameters corresponding to the temperature control device are recorded. When the frequency doubling crystal is controlled at the lower limit temperature, the corresponding lower limit control parameters of the temperature control device are recorded. This causes the control parameters of the temperature control device to change from the lower limit control parameter to the upper limit control parameter, while simultaneously detecting and recording the output frequency-doubled optical power; The control parameter corresponding to the maximum value of the output frequency-doubled optical power is selected as the precise control parameter, and the frequency-doubled crystal temperature corresponding to the precise control parameter is measured as the second crystal temperature corresponding to the current power of the input fundamental frequency light; Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

15. The laser frequency doubling method according to claim 14, characterized in that, The method further includes: The steps of changing the control parameters of the temperature control device from the lower limit control parameter to the upper limit control parameter, and simultaneously detecting and recording the output frequency-doubled optical power, specifically include: The interval between the upper limit control parameter and the lower limit control parameter is divided into multiple intervals; The control parameters of the temperature control device are changed sequentially from the lower limit control parameter to the upper limit control parameter at intervals within the range, while the output frequency-doubled optical power is measured.

16. The laser frequency doubling method according to claim 14 or 15, characterized in that, The step of establishing a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, and fitting the characteristic curve, specifically includes: A certain power of input fundamental frequency light is input into the frequency doubling crystal; Within the specified operating temperature range of the frequency doubling crystal, the temperature of the frequency doubling crystal is adjusted at rough temperature difference intervals, and the output frequency doubling optical power of the frequency doubling crystal at different temperatures is recorded; The temperature corresponding to the maximum value of the output frequency-doubled optical power is selected as the first crystal temperature corresponding to the current power of the input fundamental frequency light; Different power input fundamental frequency light is sequentially input into the frequency doubling crystal at certain power intervals to obtain a first crystal temperature corresponding to different input fundamental frequency light power; The characteristic curve is obtained by performing curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures to establish a functional relationship.

17. The laser frequency doubling method according to claim 14 or 15, characterized in that, The adjustment and recording time of the control parameters and the detection time of the output frequency-doubled optical power shall not exceed 1ms each time.

18. The laser frequency doubling method according to claim 16, characterized in that, The approximate temperature difference interval is 0.5~2℃; The interval between the upper limit control parameter and the lower limit control parameter is divided into 100 to 200 intervals.

19. The laser frequency doubling method according to claim 14 or 15, characterized in that: When a heating furnace is used to adjust the temperature of the frequency doubling crystal, the control parameter is current or resistance; When a semiconductor temperature controller is used to adjust the temperature of the frequency doubling crystal, the control parameter is current; When a heat pump or a compressor is used to regulate the temperature of the frequency doubling crystal, the control parameter is the duty cycle.

20. The laser frequency doubling method according to claim 14 or 15, characterized in that, The method further includes: Based on the specified operating temperature range of the frequency doubling crystal, the upper and lower limits of a certain temperature range centered on the temperature of the first crystal are determined.

21. The laser frequency doubling method according to claim 14 or 15, characterized in that, The method further includes: For different frequency doubling crystals, the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature is re-established, and the corresponding characteristic curve is obtained by fitting.

22. The laser frequency doubling method according to claim 14 or 15, characterized in that, The frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

23. The laser frequency doubling method according to claim 16, characterized in that, The specific steps of inputting a certain power of input fundamental frequency light into the frequency doubling crystal are as follows: collimating and focusing the input fundamental frequency light of a certain power at the center of the frequency doubling crystal.

24. The laser frequency doubling method according to claim 14 or 15, characterized in that, The method further includes: A beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal into a certain proportion. The separated optical signal is filtered and attenuated to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected. The power of the frequency-doubled optical signal to be detected is measured and recorded to obtain the actual output frequency-doubled optical power.

25. The laser frequency doubling method according to claim 14 or 15, characterized in that, The method further includes: The temperature of the frequency doubling crystal is measured at multiple non-light-transmitting points to obtain multiple temperatures, and the average value of these values ​​is taken as the temperature of the frequency doubling crystal.

26. The laser frequency doubling method according to claim 14 or 15, characterized in that, The method further includes: When the external ambient temperature of the frequency doubling crystal changes, the temperature of the frequency doubling crystal is actively compensated to control the temperature of the frequency doubling crystal at the temperature of the second crystal.

27. The laser frequency doubling method according to claim 14 or 15, characterized in that, The method further includes: When the current power of the input fundamental frequency light changes, the following steps are repeated: For the current power of the input fundamental frequency light, its corresponding first crystal temperature is determined by the characteristic curve; Determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal; When the frequency doubling crystal is controlled at the upper limit temperature, the upper limit control parameters corresponding to the temperature control device are recorded. When the frequency doubling crystal is controlled at the lower limit temperature, the corresponding lower limit control parameters of the temperature control device are recorded. This causes the control parameters of the temperature control device to change from the lower limit control parameter to the upper limit control parameter, while simultaneously detecting and recording the output frequency-doubled optical power; The control parameter corresponding to the maximum value of the output frequency-doubled optical power is selected as the precise control parameter, and the frequency-doubled crystal temperature corresponding to the precise control parameter is measured as the second crystal temperature corresponding to the current power of the input fundamental frequency light; Based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, the frequency doubling crystal temperature is actively compensated to control the frequency doubling crystal temperature at the second crystal temperature.

28. The laser frequency doubling method according to claim 14 or 15, characterized in that, The method further includes: The steps of changing the control parameters of the temperature control device from the lower limit control parameter to the upper limit control parameter, and simultaneously detecting and recording the output frequency-doubled optical power, specifically include: This causes the control parameters of the temperature control device to continuously change from the lower limit control parameter to the upper limit control parameter, while simultaneously measuring the output frequency-doubled optical power.

29. A laser frequency doubling device based on active temperature following compensation, characterized in that, The device includes: a fundamental frequency optical generator, a frequency doubling crystal, a characteristic curve acquisition unit, a characteristic curve reading unit, a temperature control device, a power detection and recording unit, and a temperature compensation device; wherein... The fundamental frequency light generator is used to generate input fundamental frequency light that is input to the frequency doubling crystal; The feature curve acquisition unit is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve and store the feature curve, wherein the first crystal temperature is a rough optimal temperature, that is, the temperature at which the output frequency doubled optical power reaches the maximum value when the temperature is adjusted at a rough temperature difference interval within the specified operating temperature range of the frequency doubled crystal under the current power of the input fundamental frequency optical power. The characteristic curve reading unit is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve; The temperature control device is used to measure the temperature of the frequency doubling crystal and adjust the temperature of the frequency doubling crystal at precise temperature difference intervals within a certain temperature range above and below the temperature of the first crystal. The power detection and recording unit is used to detect and record the output frequency-doubled optical power of the frequency-doubled crystal at different frequency-doubled crystal temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light; The temperature compensation device is used to actively follow and compensate the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal at the second crystal temperature.

30. The laser frequency doubling device according to claim 29, characterized in that, The feature curve acquisition unit includes a feature curve fitting module; The fundamental frequency optical generator inputs a certain power of input fundamental frequency light into the frequency doubling crystal; The temperature control device is also used to adjust the temperature of the frequency doubling crystal within the specified operating temperature range of the frequency doubling crystal at rough temperature difference intervals. The power detection and recording unit is also used to record the output frequency-doubled optical power of the frequency-doubled crystal at different temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the first crystal temperature corresponding to the current power of the input fundamental frequency light. The fundamental frequency light generator is also used to sequentially input the input fundamental frequency light of different powers into the frequency doubling crystal at certain power intervals, and the temperature control device and the power detection and recording unit obtain the first crystal temperature corresponding to different input fundamental frequency light powers; The characteristic curve fitting module is used to perform curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, establish a functional relationship, and obtain the characteristic curve.

31. The laser frequency doubling device according to claim 29 or 30, characterized in that, The time for each temperature adjustment and recording, as well as the detection time for the output frequency-doubled optical power, shall not exceed 1ms.

32. The laser frequency doubling device according to claim 30, characterized in that, The approximate temperature difference interval is 0.5~2℃; The precise temperature difference interval is 0.005~0.02℃.

33. The laser frequency doubling device according to claim 29 or 30, characterized in that, The temperature control device is a heating furnace, a semiconductor temperature controller, a heat pump, or a refrigeration compressor.

34. The laser frequency doubling device according to claim 29 or 30, characterized in that, The device further includes a temperature range setting unit, which is used to set a certain temperature range above and below the temperature of the first crystal based on the operating temperature range specified by the frequency doubling crystal.

35. The laser frequency doubling device according to claim 29 or 30, characterized in that, The characteristic curve acquisition unit is also used to re-establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature for different frequency doubling crystals, and fit the corresponding characteristic curve.

36. The laser frequency doubling device according to claim 29 or 30, characterized in that, The frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

37. The laser frequency doubling device according to claim 30, characterized in that, The fundamental frequency light generator includes a collimating and focusing lens, which is used to collimate and focus the input fundamental frequency light of a certain power at the center of the frequency doubling crystal.

38. The laser frequency doubling device according to claim 29 or 30, characterized in that, The power detection and recording unit includes: a beam splitter, a filtering and attenuation device, and a detector; wherein... The beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal according to a certain ratio; The filtering and attenuation device is used to filter and attenuate the separated optical signal to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected. The detector is used to measure and record the power of the frequency-doubled optical signal to be detected to obtain the actual output frequency-doubled optical power.

39. The laser frequency doubling device according to claim 29 or 30, characterized in that, The temperature control device includes multiple temperature measurement modules and an averaging module; wherein The multiple temperature measurement modules are respectively attached to the surface of multiple non-light-transmitting parts of the frequency doubling crystal, and are used to measure the temperature of the frequency doubling crystal; The averaging module takes the average of the multiple temperatures obtained by the multiple temperature measurement modules as the temperature of the frequency doubling crystal.

40. The laser frequency doubling device according to claim 29 or 30, characterized in that, The temperature compensation device is also used to actively follow and compensate the temperature of the frequency doubling crystal when the external ambient temperature of the frequency doubling crystal changes, and control the temperature of the frequency doubling crystal at the temperature of the second crystal.

41. The laser frequency doubling device according to claim 29 or 30, characterized in that, The device further includes a triggering unit for re-triggering when the current power of the input fundamental frequency light changes: The characteristic curve reading unit determines the corresponding first crystal temperature for the current power of the input fundamental frequency light through the characteristic curve; The temperature control device measures the temperature of the frequency doubling crystal and adjusts the temperature of the frequency doubling crystal at precise temperature difference intervals within a certain temperature range above and below the first crystal temperature. The power detection and recording unit detects and records the output frequency-doubled optical power of the frequency-doubled crystal at different frequency-doubled crystal temperatures, and selects the temperature corresponding to the maximum value of the output frequency-doubled optical power as the second crystal temperature corresponding to the current power of the input fundamental frequency light; as well as The temperature compensation device actively follows and compensates the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, thereby controlling the temperature of the frequency doubling crystal at the second crystal temperature.

42. A laser frequency doubling device based on active temperature following compensation, characterized in that, The device includes: a fundamental frequency optical generator, a frequency doubling crystal, a characteristic curve acquisition unit, a characteristic curve reading unit, a temperature range setting unit, a temperature control device, a control parameter adjustment unit, a power detection and recording unit, and a temperature compensation device; wherein... The fundamental frequency light generator is used to generate input fundamental frequency light that is input to the frequency doubling crystal; The feature curve acquisition unit is used to establish a functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature, fit the feature curve and store the feature curve, wherein the first crystal temperature is a rough optimal temperature, that is, the temperature at which the output frequency doubled optical power reaches the maximum value when the temperature is adjusted at a rough temperature difference interval within the specified operating temperature range of the frequency doubled crystal under the current power of the input fundamental frequency optical power. The characteristic curve reading unit is used to determine the corresponding first crystal temperature based on the current power of the input fundamental frequency light through the characteristic curve; The temperature range setting unit is used to determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal. The temperature control device is used to measure the temperature of the frequency doubling crystal and record the upper limit control parameter corresponding to the temperature control device when the frequency doubling crystal is controlled at the upper limit temperature, and record the lower limit control parameter corresponding to the temperature control device when the frequency doubling crystal is controlled at the lower limit temperature. The control parameter adjustment unit is used to change the control parameter of the temperature control device from the lower limit control parameter to the upper limit control parameter; The power detection and recording unit is used to detect and record the output frequency-doubled optical power, and select the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter. The temperature control device is also used to measure the frequency doubling crystal temperature corresponding to the precise control parameters as a second crystal temperature corresponding to the current power of the input fundamental frequency light; The temperature compensation device is used to actively follow and compensate the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, and control the temperature of the frequency doubling crystal at the second crystal temperature.

43. The laser frequency doubling device according to claim 42, characterized in that, The control parameter adjustment unit includes an interval division module and an interval adjustment module; wherein The interval division module is used to divide the interval between the upper limit control parameter and the lower limit control parameter into multiple intervals; The interval adjustment module is used to make the control parameters of the temperature control device change sequentially from the lower limit control parameter to the upper limit control parameter according to the interval points of the interval, while measuring the output frequency doubling optical power.

44. The laser frequency doubling device according to claim 42 or 43, characterized in that, The feature curve acquisition unit includes a feature curve fitting module; The fundamental frequency optical generator is used to input a certain power of fundamental frequency optical light into the frequency doubling crystal; The temperature control device is also used to adjust the temperature of the frequency doubling crystal within the specified operating temperature range of the frequency doubling crystal at rough temperature difference intervals. The power detection and recording unit is also used to record the output frequency-doubled optical power of the frequency-doubled crystal at different temperatures, and select the temperature corresponding to the maximum value of the output frequency-doubled optical power as the first crystal temperature corresponding to the current power of the input fundamental frequency light. The fundamental frequency light generator is also used to sequentially input the input fundamental frequency light of different powers into the frequency doubling crystal at certain power intervals, and the temperature control device and the power detection and recording unit obtain the first crystal temperature corresponding to different input fundamental frequency light powers; The characteristic curve fitting module is used to perform curve fitting based on multiple input fundamental frequency optical powers and their corresponding first crystal temperatures, establish a functional relationship, and obtain the characteristic curve.

45. The laser frequency doubling device according to claim 42 or 43, characterized in that, The adjustment and recording time of the control parameters and the detection time of the output frequency-doubled optical power shall not exceed 1ms each time.

46. ​​The laser frequency doubling device according to claim 44, characterized in that, The approximate temperature difference interval is 0.5~2℃; The interval between the upper limit control parameter and the lower limit control parameter is divided into 100 to 200 intervals.

47. The laser frequency doubling device according to claim 42 or 43, characterized in that, The temperature control device is a heating furnace, a semiconductor temperature controller, a heat pump, or a refrigeration compressor; in When a heating furnace is used to adjust the temperature of the frequency doubling crystal, the control parameter is current or resistance; When a semiconductor temperature controller is used to adjust the temperature of the frequency doubling crystal, the control parameter is current; When a heat pump or a compressor is used to regulate the temperature of the frequency doubling crystal, the control parameter is the duty cycle.

48. The laser frequency doubling device according to claim 42 or 43, characterized in that, The temperature range setting unit is used to determine the upper and lower limits of a certain temperature range centered on the temperature of the first crystal, based on the operating temperature range specified by the frequency doubling crystal.

49. The laser frequency doubling device according to claim 42 or 43, characterized in that, The characteristic curve acquisition unit is also used to re-establish the functional relationship between the input fundamental frequency optical power and its corresponding first crystal temperature for different frequency doubling crystals, and fit the corresponding characteristic curve.

50. The laser frequency doubling device according to claim 42 or 43, characterized in that, The frequency doubling crystal is one or more of LBO, BBO, KDP, DKDP, ADP, and DCDA.

51. The laser frequency doubling device according to claim 44, characterized in that, The fundamental frequency light generator includes a collimating and focusing lens, which is used to collimate and focus the input fundamental frequency light of a certain power at the center of the frequency doubling crystal.

52. The laser frequency doubling device according to claim 42 or 43, characterized in that, The power detection and recording unit includes: a beam splitter, a filtering and attenuation device, and a detector; wherein... The beam splitter is used to separate the frequency-doubled optical signal output after passing through the frequency-doubled crystal according to a certain ratio; The filtering and attenuation device is used to filter and attenuate the separated optical signal to obtain a low-power pure optical signal, which is then used as the frequency-doubled optical signal to be detected. The detector is used to measure and record the power of the frequency-doubled optical signal to be detected to obtain the actual output frequency-doubled optical power.

53. The laser frequency doubling device according to claim 42 or 43, characterized in that, The temperature control device includes multiple temperature measurement modules and an averaging module; wherein The multiple temperature measurement modules are respectively attached to the surface of multiple non-light-transmitting parts of the frequency doubling crystal, and are used to measure the temperature of the frequency doubling crystal; The averaging module takes the average of the multiple temperatures obtained by the multiple temperature measurement modules as the temperature of the frequency doubling crystal.

54. The laser frequency doubling device according to claim 42 or 43, characterized in that, The temperature compensation device is also used to actively follow and compensate the temperature of the frequency doubling crystal when the external ambient temperature of the frequency doubling crystal changes, and control the temperature of the frequency doubling crystal at the temperature of the second crystal.

55. The laser frequency doubling device according to claim 42 or 43, characterized in that, The device further includes a triggering unit for re-triggering when the current power of the input fundamental frequency light changes: The characteristic curve reading unit determines the corresponding first crystal temperature for the current power of the input fundamental frequency light through the characteristic curve; The temperature range setting unit determines the upper and lower limits of a certain temperature range centered on the temperature of the first crystal. When the temperature control device measures the temperature of the frequency doubling crystal and controls the frequency doubling crystal at the upper limit temperature, it records the upper limit control parameter corresponding to the temperature control device; when the frequency doubling crystal is controlled at the lower limit temperature, it records the lower limit control parameter corresponding to the temperature control device. The control parameter adjustment unit causes the control parameter of the temperature control device to change from the lower limit control parameter to the upper limit control parameter; The power detection and recording unit detects and records the output frequency-doubled optical power, and selects the control parameter corresponding to the maximum value of the output frequency-doubled optical power as the precise control parameter. The temperature control device measures the frequency doubling crystal temperature corresponding to the precise control parameters as the second crystal temperature corresponding to the current power of the input fundamental frequency light; as well as The temperature compensation device actively follows and compensates the temperature of the frequency doubling crystal based on the second crystal temperature corresponding to the current power of the input fundamental frequency light, thereby controlling the temperature of the frequency doubling crystal at the second crystal temperature.

56. The laser frequency doubling device according to claim 42 or 43, characterized in that, The control parameter adjustment unit includes a continuous adjustment module, which is used to make the control parameters of the temperature control device continuously change from the lower limit control parameter to the upper limit control parameter, while measuring the output frequency doubling optical power.

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