Cavity length control device and method for femtosecond pulse synchronous pump optical parametric oscillator

Abstract

The invention belongs to the field of optical parametric oscillators, and particularly discloses a cavity length control device and method for a femtosecond pulse synchronous pump optical parametric oscillator, and a temperature control element is arranged on a metal bottom plate and used for adjusting the temperature of the metal bottom plate; and the temperature controller is electrically connected with the temperature control element and is used for adjusting the temperature of the temperature control element according to the characteristic parameters of the light output by the optical parametric oscillator so as to adjust the temperature of the metal bottom plate to adjust the cavity length of the optical parametric oscillator. The temperature of the temperature control element is accurately adjusted through the temperature controller, fine control over the temperature of the metal bottom plate is achieved, then fine control over the length of the metal bottom plate is achieved, small changes of the length of the metal bottom plate can be directly reflected to changes of the cavity length, and therefore high-precision adjustment of the cavity length is achieved; and compared with expensive devices such as piezoelectric ceramics and precise stepping motors, the manufacturing cost and the maintenance difficulty are reduced, and meanwhile, the overall performance and stability of the system are improved.

Description

Technical Field

[0001] The invention belongs to the field of optical parametric oscillators, and in particular relates to a cavity length control device and method for a femtosecond pulse synchronously pumped optical parametric oscillator. Background Art

[0002] People have invented optical parametric oscillators by using the parametric transformation process of lasers in nonlinear optical media, which converts high-frequency pump light into two low-frequency signal lights and idler lights. Femtosecond optical parametric oscillators have many advantages in generating ultrashort laser pulses, mainly in the following aspects: a wider parametric gain bandwidth, which supports the generation of laser pulses narrower than pump pulses; the generation of ultrashort pulses of two different wavelengths, signal light and idler light; and a wide wavelength tuning range. At present, optical parametric oscillators synchronously pumped by femtosecond pulse lasers are important ultrafast coherent light sources for generating mid-infrared lasers, and have important application value in the fields of gas detection, laser processing, space optical communications, and precision spectral analysis.

[0003] Since the cavity length of the femtosecond synchronously pumped optical parametric oscillator needs to match the cavity length of the pump source, this requires that the cavity length of the femtosecond synchronously pumped optical parametric oscillator can be precisely controlled. Traditional methods for controlling the cavity length of optical parametric oscillators mostly use mechanical adjustment methods, such as building a cavity mirror in the cavity on piezoelectric ceramics and other devices, and using piezoelectric ceramics and other components to change the cavity length. However, these methods often have some disadvantages, such as limited accuracy and range of cavity length adjustment, and high cost. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a cavity length control device and method for a femtosecond pulse synchronously pumped optical parametric oscillator, which improves the cavity length adjustment accuracy of the optical parametric oscillator and reduces the cost.

[0005] In a first aspect, the technical solution of the present invention provides a cavity length control device for a femtosecond pulse synchronously pumped optical parametric oscillator, wherein the optical path element of the optical parametric oscillator is built on a metal base plate, and the device includes a temperature control element and a temperature control controller; A temperature control element is arranged on the metal bottom plate and is used to adjust the temperature of the metal bottom plate; The temperature control controller is electrically connected to the temperature control element and is used to adjust the temperature of the temperature control element according to the characteristic parameters of the output light of the optical parametric oscillator, thereby adjusting the temperature of the metal bottom plate to adjust the cavity length of the optical parametric oscillator.

[0006] In an optional embodiment, the temperature control element is an electric heating film attached to the bottom surface of the metal base plate.

[0007] In an optional embodiment, the characteristic parameter of the output light of the optical parametric oscillator is the power or central wavelength of the output idler laser.

[0008] In an optional implementation, a temperature sensor is provided on the metal bottom plate, and the temperature sensor is electrically connected to the temperature control controller.

[0009] In a second aspect, the technical solution of the present invention provides a method for controlling the cavity length of a femtosecond pulse synchronously pumped optical parametric oscillator, wherein the optical path element of the optical parametric oscillator is built on a metal base plate, comprising the following steps: A temperature control element is arranged on the metal bottom plate, and the temperature control element is electrically connected to a temperature control controller; The temperature control controller adjusts the temperature of the temperature control element according to the characteristic parameters of the output light of the optical parametric oscillator, and further adjusts the temperature of the metal bottom plate to adjust the cavity length of the optical parametric oscillator.

[0010] In an optional implementation, the temperature control controller adjusts the temperature of the temperature control element according to the characteristic parameters of the output light of the optical parametric oscillator, and then adjusts the temperature of the metal base plate to adjust the cavity length of the optical parametric oscillator, specifically including: Obtaining characteristic parameters of output light from an optical parametric oscillator; Check whether the characteristic parameters meet the requirements; If not, based on the pre-constructed correspondence between the output light characteristic parameter value and the metal base plate temperature, the target metal base plate temperature is determined according to the current output light characteristic parameter value; The temperature of the temperature control element is adjusted according to the target metal base plate temperature to adjust the cavity length of the optical parametric oscillator.

[0011] In an optional embodiment, the method further comprises the following steps: A temperature sensor is arranged on the metal bottom plate, and the temperature sensor is electrically connected to a temperature control controller; The temperature controller detects the temperature of the metal bottom plate in real time according to the temperature sensor; Detect whether the real-time detection temperature of the metal bottom plate reaches the target metal bottom plate temperature; If reached, stop adjusting the temperature of the temperature control element.

[0012] In an optional embodiment, the characteristic parameter of the output light of the optical parametric oscillator is the power or central wavelength of the output idler laser.

[0013] In an optional embodiment, the temperature control element is an electric heating film attached to the bottom surface of the metal base plate.

[0014] The present invention provides a cavity length control device and method for a femtosecond pulse synchronously pumped optical parametric oscillator, which has the following beneficial effects compared to the prior art: a temperature control element is arranged on a metal bottom plate, and the temperature of the metal bottom plate is adjusted by adjusting the temperature of the temperature control element, thereby changing the length of the metal bottom plate and adjusting the length of the optical path cavity on the metal bottom plate. The present invention uses a temperature control controller to accurately adjust the temperature of the temperature control element, thereby achieving fine control of the temperature of the metal bottom plate, thereby achieving fine control of the length of the metal bottom plate, and since the optical path element of the optical parametric oscillator is arranged on the metal bottom plate, a slight change in the length of the metal bottom plate can be directly reflected in the change of the cavity length, thereby achieving high-precision adjustment of the cavity length. The temperature control controller can quickly respond to changes in the characteristic parameters of the output light of the optical parametric oscillator, and adjust the temperature of the temperature control element in real time, thereby achieving rapid and stable control of the cavity length. Compared with the traditional mechanical adjustment method, the present invention uses a temperature control method to control the cavity length, which can effectively reduce the influence of external factors such as ambient temperature and humidity on the stability of the cavity length, and improve the environmental adaptability and reliability of the optical parametric oscillator. At the same time, through the integrated design of temperature control elements and temperature control controllers, the cavity length control structure of the optical parametric oscillator is simplified. Compared with expensive devices such as piezoelectric ceramics and precision stepper motors, the manufacturing cost and maintenance difficulty are reduced, while the overall performance and stability of the system are improved. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 It is a schematic structural diagram of a cavity length control device for a femtosecond pulse synchronously pumped optical parametric oscillator provided in an embodiment of the present invention.

[0016] Figure 2 The present invention provides a schematic flow chart of a method for controlling the cavity length of a femtosecond pulse synchronously pumped optical parametric oscillator.

[0017] Figure 3 This is a diagram of eight-hour power stability.

[0018] Figure 4 This is a schematic diagram showing the change in idle laser output power with base plate temperature when the pump power is 1.7W.

[0019] Figure 5 This is a schematic diagram of the change in the central wavelength of the output idler laser with the temperature of the base plate.

[0020] Figure 6This is a schematic diagram of the output spectrum of the femtosecond synchronous pump optical parametric oscillator at different metal base plate temperatures.

[0021] In the figure, 1-optical path element, 2-metal base plate, 3-temperature control element, 4-temperature control controller. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] In view of the fact that the current methods for controlling the cavity length of optical parametric oscillators mostly use mechanical adjustment means, such as using piezoelectric ceramics to adjust the position of a single cavity mirror to change the cavity length, there are problems such as adjustment accuracy and range, resulting in limited cavity length adjustment accuracy and high cost. This embodiment provides a cavity length control device for a femtosecond pulse synchronously pumped optical parametric oscillator, wherein a temperature control element 3 is arranged on a metal base plate 2, and a temperature control controller 4 adjusts the temperature of the temperature control element 3 according to the characteristic parameters of the output light of the optical parametric oscillator, and then adjusts the temperature of the metal base plate 2 to adjust the cavity length of the optical parametric oscillator. This embodiment uses a temperature-controlled metal base plate 2 to replace expensive devices such as piezoelectric ceramics and precision stepping motors to adjust the cavity length of the optical parametric oscillator, thereby achieving the effect of accurately adjusting the cavity length while reducing costs.

[0025] Figure 1 is a schematic diagram of the structure of a cavity length control device for a femtosecond pulse synchronously pumped optical parametric oscillator provided by an embodiment of the present invention, such as Figure 1 As shown, the optical path element 1 of the optical parametric oscillator is built on a metal base plate 2, and a temperature control element 3 is arranged on the metal base plate 2, and the temperature control element 3 is used to adjust the temperature of the metal base plate 2. The temperature control element 3 is electrically connected to a temperature control controller 4, and the temperature control controller 4 adjusts the temperature of the temperature control element 3 according to the characteristic parameters of the output light of the optical parametric oscillator, and then adjusts the temperature of the metal base plate 2 to adjust the cavity length of the optical parametric oscillator.

[0026] In this embodiment, the optical parametric oscillator is built on a metal base plate 2, and a temperature control element 3 is added to the metal base plate 2 to precisely control the cavity length of the optical parametric oscillator using the thermal expansion and contraction principle of metal materials. The principle of using temperature to control the cavity length: Most solid materials show a relationship of thermal expansion and contraction with temperature changes, and the change in the length of the material with temperature can be measured by the linear expansion coefficient. The linear expansion coefficient of some common metal materials is often 10 -6 / ℃ level, when the temperature changes by 1℃, the length of a 1-meter material changes by micrometer level. The current temperature control board can achieve 0.001℃ temperature control, and the corresponding material elongation is in the nanometer level. This nanometer-level length precision regulation can meet the requirements of the femtosecond synchronous pump optical parametric oscillator for cavity length accuracy.

[0027] In an optional embodiment, the temperature control element 3 is an electric heating film attached to the bottom surface of the metal base plate 2, and the characteristic parameter of the output light of the optical parametric oscillator is the power or central wavelength of the output idler laser.

[0028] During the specific implementation, the optical parametric oscillator is built on the metal base plate 2, and the cavity length is roughly determined. The linear expansion coefficient of the metal base plate 2 is known, and its elongation can be experimentally measured with temperature. According to the repetition frequency of the pump source, the cavity length of the synchronously pumped optical parametric oscillator is roughly determined. A temperature control element is added to the metal base plate 2 to control and adjust the temperature of the metal base plate 2. For example, an electric heating film is attached to the metal base plate 2, and a temperature control controller 4 is used to control the temperature of the electric heating film. The temperature of the metal base plate 2 is controlled to achieve precise control of the cavity length of the optical parametric oscillator. The relationship curve between the output laser power or the central wavelength and the temperature is measured to determine the temperature value set when the desired wavelength is output, thereby realizing a temperature-controlled synchronously pumped optical parametric oscillator.

[0029] It should be noted that the accuracy of some temperature control devices can reach 0.001 degrees Celsius, and the thermal expansion and contraction of metal materials can achieve nanometer-level precision control of the cavity length. Therefore, the temperature-controlled metal base plate 2 can be used to replace expensive devices such as piezoelectric ceramics and precision stepping motors to control the cavity length of the optical parametric oscillator, thereby achieving the effect of precisely controlling the cavity length while reducing costs.

[0030] In an optional embodiment, a temperature sensor is provided on the metal bottom plate 2 , and the temperature sensor is electrically connected to the temperature control controller 4 . The temperature control controller 4 controls the operating state of the temperature control element 3 according to the temperature fed back by the temperature sensor.

[0031] The above describes in detail an embodiment of a cavity length control device for a femtosecond pulse synchronously pumped optical parametric oscillator. Based on the cavity length control device method for a femtosecond pulse synchronously pumped optical parametric oscillator described in the above embodiment, an embodiment of the present invention also provides a cavity length control method for a femtosecond pulse synchronously pumped optical parametric oscillator corresponding to the device.

[0032] Figure 2 FIG. 1 is a flow chart of a method for controlling the cavity length of a femtosecond pulse synchronously pumped optical parametric oscillator provided in an embodiment of the present invention. In this embodiment, an optical path element 1 of the optical parametric oscillator is built on a metal base plate 2. Figure 2 As shown, the method includes the following steps.

[0033] S1, a temperature control element 3 is arranged on the metal bottom plate 2, and the temperature control element 3 is electrically connected to a temperature control controller 4.

[0034] S2, the temperature control controller 4 adjusts the temperature of the temperature control element 3 according to the characteristic parameters of the output light of the optical parametric oscillator, and further adjusts the temperature of the metal bottom plate 2 to adjust the cavity length of the optical parametric oscillator.

[0035] In this embodiment, a temperature control element 3 is arranged on the metal bottom plate 2, and the temperature of the metal bottom plate 2 is adjusted by adjusting the temperature of the temperature control element 3, thereby changing the length of the metal bottom plate 2 and adjusting the length of the optical path cavity on the metal bottom plate 2. In this embodiment, the temperature of the temperature control element 3 is precisely adjusted by the temperature control controller 4 to achieve fine control of the temperature of the metal bottom plate 2, thereby achieving fine control of the length of the metal bottom plate 2. Since the optical path element 1 of the optical parametric oscillator is arranged on the metal bottom plate 2, a slight change in the length of the metal bottom plate 2 can be directly reflected in the change of the cavity length, thereby achieving high-precision adjustment of the cavity length. The temperature control controller 4 can quickly respond to the change of the characteristic parameters of the output light of the optical parametric oscillator, and adjust the temperature of the temperature control element 3 in real time, thereby achieving fast and stable control of the cavity length. Compared with the traditional mechanical adjustment method, the temperature control method of this embodiment is used to control the cavity length, which can effectively reduce the influence of external factors such as ambient temperature and humidity on the stability of the cavity length, and improve the environmental adaptability and reliability of the optical parametric oscillator. At the same time, through the integrated design of the temperature control element 3 and the temperature control controller 4, the cavity length control structure of the optical parametric oscillator is simplified, and compared with expensive devices such as piezoelectric ceramics and precision stepper motors, the manufacturing cost and maintenance difficulty are reduced, while the overall performance and stability of the system are improved.

[0036] In this embodiment, the temperature control controller 4 adjusts the temperature of the temperature control element 3 according to the characteristic parameters of the optical parametric oscillator output light, and then adjusts the temperature of the metal base plate 2 to adjust the cavity length of the optical parametric oscillator, which specifically includes the following steps.

[0037] Step 1: Obtain characteristic parameters of the output light of the optical parametric oscillator.

[0038] In this embodiment, the temperature control controller 4 determines whether the cavity length of the optical parametric oscillator meets the requirements based on the characteristic parameters of the output light. If the characteristic parameters of the output light meet the requirements, it means that the cavity length of the optical parametric oscillator meets the requirements. On the contrary, if the characteristic parameters of the output light do not meet the requirements, it means that the cavity length of the optical parametric oscillator needs to be adjusted to output the output light whose characteristic parameters meet the requirements.

[0039] In this embodiment, the characteristic parameter of the optical parametric oscillator output light is the power or center wavelength of the output idler laser, that is, the temperature controller 4 adjusts the temperature of the metal base plate 2 according to the power or center wavelength of the output idler laser, thereby adjusting the cavity length of the optical parametric oscillator. The principle of determining whether the cavity length of the optical parametric oscillator meets the requirements based on the characteristic parameter of the output light will be described in detail later and will not be repeated here.

[0040] Step 2: Check whether the characteristic parameters meet the requirements.

[0041] Step 3: if not, based on the pre-constructed correspondence between the output light characteristic parameter value and the temperature of the metal bottom plate 2 , determine the target metal bottom plate 2 temperature according to the current output light characteristic parameter value.

[0042] In this embodiment, the optical parametric oscillator is tested in advance to obtain the corresponding relationship between the output light characteristic parameter value of the optical parametric oscillator and the temperature of the metal bottom plate 2, and the corresponding relationship is stored in the memory. When it is detected that the output light characteristic parameter value does not meet the requirements, that is, it does not reach the target, it is necessary to adjust the temperature of the metal bottom plate 2, thereby adjusting the length of the metal bottom plate 2. Correspondingly, the cavity length of the optical parametric oscillator is adjusted. The temperature control controller 4 retrieves the stored corresponding relationship between the output light characteristic parameter value and the temperature of the metal bottom plate 2 from the memory, and determines the target temperature of the metal bottom plate 2 according to the corresponding relationship.

[0043] Step 4: adjusting the temperature of the temperature control element 3 according to the target temperature of the metal base plate 2 to adjust the cavity length of the optical parametric oscillator.

[0044] In this embodiment, after the temperature controller 4 obtains the target temperature of the metal base plate 2 , it controls the temperature control element 3 based on the target temperature to adjust the cavity length of the optical parametric oscillator.

[0045] In an optional embodiment, a temperature sensor is provided on the metal bottom plate 2, and the temperature sensor is electrically connected to the temperature control controller 4. The temperature control controller 4 detects the temperature of the metal bottom plate 2 in real time according to the temperature sensor; detects whether the real-time detected temperature of the metal bottom plate 2 reaches the target temperature of the metal bottom plate 2; if reached, stops adjusting the temperature of the temperature control element 3.

[0046] The following is an explanation of the effect of the temperature of the metal bottom plate 2 on the characteristic parameters of the output light in combination with the experiment. In the femtosecond synchronously pumped optical parametric oscillator: the wavelength of the pump source is 1032nm, the pulse width is 800fs, the repetition frequency is 80MHz, and the power is continuously adjustable from 0 to 10W; the optical parametric gain medium is a PPLN with a length of 2mm and a polarization period of 31.02μm; in order to broaden the spectrum, a dispersion and nonlinear control element ZnSe is added to the resonant cavity. The synchronously pumped optical parametric oscillator is single-resonant, the wavelength range of the cavity mirror coating is 2100nm-2500nm, and the output laser is an idler light, and the wavelength can be tuned in the range of 2100nm-2500nm. To achieve synchronous pumping, the cavity length of the optical parametric oscillator needs to match the repetition rate of the pump source.

[0047] In order to precisely control the cavity length, the optical parametric oscillator is built on a 650×440×15mm aluminum plate. At the same time, an electric heating film is laid on the surface of the aluminum plate to control the temperature of the bottom plate. The size of the electric heating film is 90mmx170mm / 12v12w. According to the repetition frequency of the pump source, the resonant cavity length of the optical parametric oscillator is roughly set to 1875mm, and then the cavity length of the optical parametric oscillator is finely controlled by controlling the bottom plate temperature.

[0048] In the test, the temperature control element used had an accuracy of 0.001°C. The experimental results are as follows: See also Figure 3 When the pump light power is 1.7W and the temperature of the optical parametric oscillator base plate is set to 29.681℃, the laser power output by the optical parametric oscillator evolves with time as shown in Figure 3 As shown, the power stability RMS = 0.82%. The results show that when the temperature fluctuation range of the metal base plate 2 is less than 0.001°C, the power RMS stability of the femtosecond optical parametric oscillator is less than one percent.

[0049] See also Figure 4 When the pump light power is 1.7W, the power of the output idler light can be changed by changing the temperature of the metal bottom plate 2. This is because the power of the output laser is often different under different cavity lengths. It can be said that the change in power reflects the change in cavity length.

[0050] See also Figure 5 When the pump light power is 1.7W, the central wavelength of the output idler light can be changed by changing the temperature of the metal bottom plate 2. Limited by the cavity mirror coating range, the maximum tuning range of the optical parametric oscillator output laser wavelength is 2.1-2.5 microns. Figure 5 It can be seen from the results in that the maximum tuning range of the wavelength can be achieved by adjusting the temperature of the metal base plate 2.

[0051] See also Figure 6 At different temperatures of the metal base plate 2, the spectrum of the output laser is as follows Figure 6 shown.

[0052] In conclusion, Figure 3 It is shown that a highly stable synchronously pumped femtosecond optical parametric oscillator can be achieved by controlling the temperature of the metal base plate 2. Figure 4-Figure 6 This shows that the power and wavelength of the optical parametric oscillator can be tuned by controlling the temperature of the base plate. It can be seen that the base plate temperature control can replace expensive piezoelectric ceramics to achieve the functions of power stabilization and wavelength regulation.

[0053] The above disclosure is only a preferred embodiment of the present invention, but the present invention is not limited thereto. Any non-creative changes that can be thought of by a person skilled in the art, as well as several improvements and modifications made without departing from the principle of the present invention, should fall within the protection scope of the present invention.

Claims

1. A cavity length control device for a femtosecond pulse synchronously pumped optical parametric oscillator, wherein the optical path element of the optical parametric oscillator is built on a metal base plate, characterized in that: The device includes a temperature control element and a temperature control controller; A temperature control element is arranged on the metal bottom plate and is used to adjust the temperature of the metal bottom plate; The temperature control controller is electrically connected to the temperature control element and is used to adjust the temperature of the temperature control element according to the characteristic parameters of the output light of the optical parametric oscillator, thereby adjusting the temperature of the metal bottom plate to adjust the cavity length of the optical parametric oscillator.

2. The cavity length control device of a femtosecond pulse synchronously pumped optical parametric oscillator according to claim 1, characterized in that: The temperature control element is an electric heating film attached to the bottom surface of the metal base plate.

3. The cavity length control device of a femtosecond pulse synchronously pumped optical parametric oscillator according to claim 1, characterized in that: The characteristic parameter of the output light of the optical parametric oscillator is the power or central wavelength of the output idler laser.

4. The cavity length control device of a femtosecond pulse synchronously pumped optical parametric oscillator according to claim 1, characterized in that: A temperature sensor is arranged on the metal bottom plate, and the temperature sensor is electrically connected to the temperature control controller.

5. A method for controlling the cavity length of a femtosecond pulse synchronously pumped optical parametric oscillator, wherein the optical path element of the optical parametric oscillator is built on a metal base plate, characterized in that: The following steps are involved: A temperature control element is arranged on the metal bottom plate, and the temperature control element is electrically connected to a temperature control controller; The temperature control controller adjusts the temperature of the temperature control element according to the characteristic parameters of the output light of the optical parametric oscillator, and further adjusts the temperature of the metal bottom plate to adjust the cavity length of the optical parametric oscillator.

6. The cavity length control method of a femtosecond pulse synchronously pumped optical parametric oscillator according to claim 5, characterized in that: The temperature control controller adjusts the temperature of the temperature control element according to the characteristic parameters of the output light of the optical parametric oscillator, and then adjusts the temperature of the metal base plate to adjust the cavity length of the optical parametric oscillator, specifically including: Obtaining characteristic parameters of output light from an optical parametric oscillator; Check whether the characteristic parameters meet the requirements; If not, based on the pre-constructed correspondence between the output light characteristic parameter value and the metal base plate temperature, the target metal base plate temperature is determined according to the current output light characteristic parameter value; The temperature of the temperature control element is adjusted according to the target metal base plate temperature to adjust the cavity length of the optical parametric oscillator.

7. The cavity length control method of a femtosecond pulse synchronously pumped optical parametric oscillator according to claim 6, characterized in that: The method further comprises the following steps: A temperature sensor is arranged on the metal bottom plate, and the temperature sensor is electrically connected to a temperature control controller; The temperature controller detects the temperature of the metal bottom plate in real time according to the temperature sensor; Detect whether the real-time detection temperature of the metal bottom plate reaches the target metal bottom plate temperature; If reached, stop adjusting the temperature of the temperature control element.

8. The cavity length control method of a femtosecond pulse synchronously pumped optical parametric oscillator according to any one of claims 5 to 7, characterized in that: The characteristic parameter of the output light of the optical parametric oscillator is the power or central wavelength of the output idler laser.

9. The cavity length control method of a femtosecond pulse synchronously pumped optical parametric oscillator according to any one of claims 5 to 7, characterized in that: The temperature control element is an electric heating film attached to the bottom surface of the metal base plate.

Images