Apparatus for automatically adjusting mode ratio of solid state laser and method for adjusting mode ratio thereof

Abstract

This invention provides a device and method for automatically adjusting the mode ratio of a solid-state laser. The device first measures the beam radius of the output laser at the output mirror position and the cavity length of the resonant cavity using a measurement module to obtain test data. Then, a displacement control module adjusts the cavity length of the resonant cavity based on the preset mode ratio of the solid-state laser and the test data to control the beam radius of the output laser in the laser crystal. This ensures that the absolute value of the difference between the actual mode ratio and the preset mode ratio is less than or equal to 0.01, thereby improving the conversion efficiency and output laser power of the solid-state laser. Furthermore, the device for automatically adjusting the mode ratio of a solid-state laser provided by this invention features a simple structure, stability, reliability, and high control precision, enabling rapid and accurate adjustment of the solid-state laser's mode ratio as needed.

Description

[0001] A device and method for automatically adjusting the mode ratio of a solid-state laser. Technical Field

[0002] This invention relates to the field of solid-state laser technology, and in particular to a device and method for automatically adjusting the mode ratio of a solid-state laser. Background Technology

[0003] With the rapid development of solid-state laser technology, diode-pumped solid-state lasers have been widely used in industry, scientific research, biology, and medicine due to their advantages such as simple structure, small size and weight, high conversion efficiency, and good stability. For diode-face-pumped solid-state lasers, matching the output laser spot radius with the pump light spot radius is a crucial aspect of solid-state laser structure design and a key factor in improving output power and conversion efficiency. It is generally believed that solid-state lasers with a mode ratio (the ratio of the output laser spot radius to the pump light spot radius in the laser crystal) between 0.8 and 1.5 exhibit higher output power and conversion efficiency.

[0004] However, due to the thermal lensing effect of solid-state lasers, the spot radius of the output laser in the laser crystal changes with the pump power, which in turn changes the mode ratio of the solid-state laser, reduces the efficiency of the solid-state laser, and limits the further improvement of the output power of the solid-state laser.

[0005] Therefore, in the design of solid-state lasers, how to adjust the laser parameters under different pump powers and change the spot radius of the output laser in the laser crystal so as to keep the mode ratio of the solid-state laser within a suitable error range is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide an apparatus and method for automatically adjusting the mode ratio of a solid-state laser, thereby solving the technical problem that existing solid-state lasers are unable to maintain the mode ratio within a suitable error range under different pump powers.

[0007] To solve the above-mentioned technical problems, the present invention provides a device for automatically adjusting the mode ratio of a solid-state laser, comprising:

[0008] A pump module is used to generate pump light and couple it into the resonant cavity;

[0009] The resonant cavity, which is optically connected to the pump module, includes an input mirror, a laser crystal, and an output mirror that are optically connected in sequence, with the incident end face of the laser crystal being closely attached to the input mirror;

[0010] The measurement module is set close to the output end face of the output mirror and is used to measure the laser spot radius and cavity length of the resonant cavity at the output mirror position to obtain test data.

[0011] The displacement control module, electrically connected to the measurement module, is used to adjust the cavity length of the resonant cavity according to the preset mode ratio of the solid-state laser and the test data, so that the absolute value of the difference between the actual mode ratio of the solid-state laser and the preset mode ratio is less than or equal to 0.01.

[0012] Preferably, the pump module is located near the incident side of the input mirror, and the pump module includes a pump source, a transmission optical fiber, and a coupling lens group;

[0013] One end of the transmission fiber is fused to the pump source, and the coupling lens group is located between the transmission fiber and the input mirror.

[0014] Preferably, the pump source is a laser diode, and the coupling lens group includes two focusing lenses arranged parallel to each other.

[0015] Preferably, the input mirror is a concave mirror, the incident plane of the input mirror is coated with a pump light antireflection film, and the exit concave surface of the input mirror is coated with a laser high reflectivity film. The laser high reflectivity film is used to reflect the output laser emitted by the stimulated output of the laser crystal. The output mirror is a concave mirror, and the transmittance of the output mirror to the output laser is 2% to 30%.

[0016] Preferably, the laser crystal includes a rare-earth-doped laser crystal, and the measurement module includes a CCD camera.

[0017] Preferably, the displacement control module includes an electric displacement platform controller and a high-precision electric displacement platform. The electric displacement platform controller is electrically connected to the high-precision electric displacement platform and the measurement module, respectively. The input mirror and the output mirror are both fixed on the high-precision electric displacement platform.

[0018] Accordingly, the present invention also provides an adjustment method for automatically adjusting the mode ratio of a solid-state laser using any of the above-mentioned devices, the adjustment method comprising:

[0019] S10 provides a device for automatically adjusting the mode ratio of a solid-state laser and determining the pump power and preset mode ratio of the pump module;

[0020] S20, the measurement module measures the laser spot radius at the output mirror position under the current pump power and the initial cavity length of the resonant cavity at this time to obtain test data;

[0021] S30, the displacement control module adjusts the cavity length of the resonant cavity according to the preset mode ratio and test data, so that the absolute value of the difference between the actual mode ratio of the solid-state laser and the preset mode ratio is less than or equal to 0.01.

[0022] Preferably, step S30 specifically includes:

[0023] S301, the equivalent radius of curvature of the input mirror is calculated based on the initial cavity length, the radius of curvature of the output mirror, the wavelength of the output laser, and the spot radius of the output laser at the position of the output mirror under the current pump power.

[0024] S302, the target cavity length that meets the preset mode ratio is calculated based on the preset mode ratio, the spot radius of the pump light in the laser crystal, the equivalent radius of curvature of the input mirror, the radius of curvature of the output mirror, and the wavelength of the output laser.

[0025] S303, the displacement control module controls the high-precision electric displacement platform to adjust the cavity length of the resonant cavity from the initial cavity length to the target cavity length.

[0026] Preferably, in step S301, the formula for calculating the equivalent radius of curvature of the input mirror is as follows:

[0027] ;

[0028] in, R ′ is the equivalent radius of curvature of the input mirror. L cav R1 is the initial cavity length, and R2 is the radius of curvature of the output mirror. λ The wavelength of the output laser, ω This is the laser spot radius at the output mirror position under the current pump power.

[0029] Preferably, in step S302, the formula for calculating the target cavity length is as follows:

[0030] ;

[0031] in, L cav ′ represents the target cavity length. r For preset mode ratio, ω p The radius of the pump light spot in the laser crystal is denoted as .

[0032] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides a device and method for automatically adjusting the mode ratio of a solid-state laser. The device first measures the beam radius of the output laser at the output mirror position and the cavity length of the resonant cavity using a measurement module to obtain test data. Then, a displacement control module adjusts the cavity length of the resonant cavity based on the preset mode ratio of the solid-state laser and the test data to control the beam radius of the output laser in the laser crystal. This ensures that the absolute value of the difference between the actual mode ratio and the preset mode ratio of the solid-state laser is less than or equal to 0.01, thereby improving the conversion efficiency and output laser power of the solid-state laser. Furthermore, the device for automatically adjusting the mode ratio of a solid-state laser provided by this invention features a simple structure, stability, reliability, and high control precision, enabling rapid and accurate adjustment of the solid-state laser mode ratio as needed. Attached Figure Description

[0033] Figure 1 A schematic diagram of the frame of the device for automatically adjusting the mode ratio of a solid-state laser provided in an embodiment of the present invention;

[0034] Figure 2 A connection diagram of the device for automatically adjusting the mode ratio of a solid-state laser provided in an embodiment of the present invention;

[0035] Figure 3 A flowchart illustrating the method for automatically adjusting the mode ratio of a solid-state laser according to an embodiment of the present invention;

[0036] In the figure: 100 - Device for automatically adjusting the mode ratio of the solid-state laser; 10 - Pump module; 11 - Pump source; 12 - Transmission fiber; 13 - Coupled lens group; 20 - Resonant cavity; 21 - Input mirror; 22 - Laser crystal; 23 - Output mirror; 30 - Measurement module; 40 - Displacement control module; 41 - High-precision electric displacement platform; 42 - Electric displacement platform controller. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] The purpose of this invention is to address the shortcomings of existing technologies by providing a device for automatically adjusting the mode ratio of a solid-state laser, which can achieve the adjustment of the mode ratio of a solid-state laser.

[0039] Please see Figures 1 to 2 , Figure 1A schematic diagram of the frame of the device 100 for automatically adjusting the mode ratio of a solid-state laser provided in an embodiment of the present invention; Figure 2 A connection diagram of an apparatus 100 for automatically adjusting the mode ratio of a solid-state laser provided in an embodiment of the present invention; wherein, the apparatus 100 for automatically adjusting the mode ratio of a solid-state laser provided by the present invention includes:

[0040] Pump module 10 is used to generate pump light and couple it into the resonant cavity 20;

[0041] The resonant cavity 20 is optically connected to the pump module 10 and includes an input mirror 21, a laser crystal 22 and an output mirror 23 that are optically connected in sequence. The incident end face of the laser crystal 22 is set close to the input mirror 21.

[0042] The measurement module 30 is set close to the output end face of the output mirror 23 and is used to measure the laser spot radius and cavity length of the resonant cavity 20 at the position of the output mirror 23 to obtain test data.

[0043] The displacement control module 40 is electrically connected to the measurement module 30 and is used to adjust the cavity length of the resonant cavity 20 according to the preset mode ratio of the solid-state laser and the test data, so that the absolute value of the difference between the actual mode ratio of the solid-state laser and the preset mode ratio is less than or equal to 0.01.

[0044] In this embodiment of the invention, the pump module 10 is disposed near the incident side of the input mirror 21, and the pump module 10 includes a pump source 11, a transmission optical fiber 12 and a coupling lens group 13.

[0045] One end of the transmission fiber 12 is fused to the pump source 11, and the coupling lens group 13 is located between the transmission fiber 12 and the input mirror 21.

[0046] Specifically, pump source 11 is used to generate pump light; transmission fiber 12 is mainly responsible for efficiently transmitting the pump light to the focal position on the incident side of coupling lens group 13. In this process, its good optical transmission performance ensures that the pump light energy is lost as little as possible, thereby providing sufficient energy for laser generation.

[0047] Specifically, the coupling lens group 13 is used to focus the pump light transmitted through the transmission fiber 12 into the laser crystal 22. At this time, the size of the spot radius of the pump light in the laser crystal 22 can be precisely controlled by the coupling lens group 13.

[0048] Preferably, the pump source 11 is a laser diode; the coupling lens group 13 includes two focusing lenses arranged parallel to each other.

[0049] In this embodiment of the invention, the most important function of the resonant cavity 20 is to provide an optical feedback mechanism. When the laser medium (such as the laser crystal 22) achieves population inversion and generates stimulated emission under the action of pump light, initial photon emission occurs. These photons reflect back and forth within the resonant cavity 20, and each time they pass through the laser medium, they trigger more stimulated emission, causing the photon number to continuously increase. For example, in a simple resonant cavity 20 composed of two parallel mirrors, photons continuously travel back and forth between the two mirrors, much like in an "optical echo chamber," constantly interacting with the laser medium, thereby amplifying the optical signal and ultimately achieving laser oscillation. This optical feedback is one of the key conditions for generating laser light; only when the light can be effectively fed back and continuously amplified within the cavity can a stable laser output be formed.

[0050] Specifically, the input mirror 21 is a concave mirror, the incident plane of the input mirror 21 is coated with a pump light anti-reflection film, and the exit concave surface of the input mirror 21 is coated with a laser high reflectivity film. The laser high reflectivity film is used to reflect the output laser emitted by the laser crystal 22 under stimulation.

[0051] The pump light antireflection coating on the incident surface of the input mirror 21 primarily reduces reflection loss of the pump light as it enters the input mirror 21. The laser high-reflectivity coating on the exit surface of the input mirror 21 mainly reflects the output laser light generated by the stimulated output of the laser crystal 22. Inside the resonant cavity 20, the laser crystal 22 generates output laser light after being excited by the pump light. This output laser light propagates within the resonant cavity 20. When it reaches the exit surface of the input mirror 21, the laser high-reflectivity coating reflects the output laser light back into the resonant cavity 20, causing the output laser light to continuously travel back and forth within the resonant cavity 20. This achieves light gain amplification, ultimately forming a stable laser output.

[0052] In this embodiment of the invention, the laser crystal 22 includes a rare earth-doped laser crystal, preferably an Nd:YLF crystal; the Nd:YLF crystal has natural birefringence, which gives it unique advantages in certain specific laser applications, such as the ability to use its birefringence to achieve functions such as laser polarization control and frequency conversion.

[0053] In this embodiment of the invention, the output mirror 23 is a concave mirror, and the transmittance of the output laser by the output mirror 23 is 2% to 30%. When the concave mirror is used as the output mirror 23, it can focus or collimate the laser. If designed properly, the concave mirror can change the degree of laser divergence, converging the originally divergent laser into a specific area, or adjusting the converged laser into a parallel beam output.

[0054] Specifically, the output mirror 23 has a transmittance of 2% to 30% for the output laser. This range of transmittance can effectively control the output energy of the laser. Lower transmittance means that most of the laser will continue to be reflected and amplified within the resonant cavity 20, with only a small amount of laser being output. This allows the laser to accumulate sufficient energy within the cavity, achieving higher intracavity power. For applications requiring high power density (such as laser-induced breakdown spectroscopy), this low transmittance setting can achieve higher energy gain within the cavity. Higher transmittance, on the other hand, allows for more laser output, making it suitable for scenarios where the output power requirement is not particularly high, but a certain intensity of laser light is needed for direct external applications (such as laser displays).

[0055] In this embodiment of the invention, the measurement module 30 includes a CCD camera. The CCD camera is a digital camera that uses a charge-coupled device (CCD) as its photosensitive element, and consists of an array of numerous neatly arranged MOS capacitors. When light shines on the CCD, photon energy is absorbed by the semiconductor, generating electron-hole pairs. The electrons are collected in the capacitors by the electric field, forming charge packets. The magnitude of the charge is proportional to the intensity of the incident light. Under the control of external circuitry, these charge packets are transferred and read out sequentially in a certain order. The charge signals are then converted into digital signals by an analog-to-digital converter, ultimately forming an image.

[0056] Specifically, the CCD camera is placed close to the output mirror 23, which can measure the size of the laser spot radius of the output laser located at the position of the output mirror 23 in real time.

[0057] In this embodiment of the invention, the displacement control module 40 includes an electric displacement platform controller 42 and a high-precision electric displacement platform 41. The electric displacement platform controller 42 is electrically connected to the high-precision electric displacement platform 41 and the measurement module 30, respectively. The input mirror 21 and the output mirror 23 are both fixed on the high-precision electric displacement platform 41.

[0058] Please continue reading. Figure 2The automatic adjustment device 100 for the mode ratio of a solid-state laser provided in this embodiment of the invention adjusts the mode ratio of the solid-state laser as follows: the pump light emitted from the pump source 11 enters the laser crystal 22 through the coupling lens group 13, and the size of the spot radius of the pump light entering the laser crystal 22 can be controlled by the coupling lens group 13; the output laser generated by the laser crystal 22 is emitted through the output mirror 23; the size of the spot radius of the output laser is measured by a CCD camera closely attached to the output mirror 23, and the equivalent radius of curvature of the input mirror 21 and the length of the resonant cavity 20 to be adjusted are obtained according to the theory of the resonant cavity 20; finally, the length of the resonant cavity 20 is adjusted by an electric displacement platform to control the size of the spot radius of the output laser in the laser crystal 22, thereby achieving the purpose of automatically adjusting the mode ratio of the solid-state laser under different pump powers.

[0059] Please see Figures 1 to 3 This invention also provides a device 100 for automatically adjusting the mode ratio of a solid-state laser using any of the above-mentioned methods, and an adjustment method for automatically adjusting the mode ratio of a solid-state laser. According to the above-mentioned method for automatically adjusting the mode ratio of a solid-state laser, based on the theory of the laser resonator 20, the radius of the output laser spot at the position of the output mirror 23 is measured by a CCD camera under different pump powers, and the equivalent radius of curvature of the output mirror 23 is calculated. Then, the length of the resonator 20 that conforms to the preset mode ratio is calculated. The length of the resonator 20 between the input mirror 21 and the output mirror 23 is changed by a high-precision electric displacement platform to control the radius of the output laser spot in the laser crystal 22, ultimately achieving the purpose of automatically adjusting the mode ratio of the solid-state laser under different pump powers. The above-mentioned method for automatically adjusting the mode ratio of a solid-state laser includes the following steps:

[0060] S10 provides a device 100 for automatically adjusting the mode ratio of a solid-state laser and determines the pump power and preset mode ratio of the pump module 10.

[0061] Specifically, step S10 also includes:

[0062] First, an automatic adjustment device 100 for the mode ratio of a solid-state laser is provided, with the laser crystal 22 placed close to the input mirror 21. Then, the pump source 11 is turned on, and the pump power and preset mode ratio of the pump module 10 are determined.

[0063] Specifically, the relationship between the preset mode ratio, the spot radius of the output laser in the laser crystal 22, and the spot radius of the pump light in the laser crystal 22 satisfies formula (1) as follows:

[0064] (1);

[0065] in, r For preset mode ratio, ω l To determine the beam radius of the output laser in the laser crystal 22, ω p The radius of the pump light spot in the laser crystal 22 is denoted as .

[0066] Furthermore, since the pump light is shaped and enters the laser crystal 22 through the coupling lens group 13, the spot radius of the pump light in the laser crystal 22 is... ω p It can be controlled by the coupling lens group 13 and can be set to a fixed value.

[0067] S20, the measurement module 30 measures the laser spot radius at the position of the output mirror 23 under the current pump power and the initial cavity length of the resonant cavity 20 at this time to obtain test data.

[0068] Specifically, step S20 also includes:

[0069] First, the radius of the laser beam output at position 23 of the output mirror under the current pumping efficiency is measured using a CCD camera and denoted as [missing information]. ω And measure the distance between the input mirror 21 and the output mirror 23 at this time, which is the initial cavity length of the resonant cavity 20, denoted as . L cav .

[0070] S30, the displacement control module 40 adjusts the cavity length of the resonant cavity 20 according to the preset mode ratio and test data, so that the absolute value of the difference between the actual mode ratio of the solid-state laser and the preset mode ratio is less than or equal to 0.01.

[0071] Specifically, step S30 includes:

[0072] S301, the equivalent radius of curvature of the input mirror 21 is calculated based on the initial cavity length, the radius of curvature of the output mirror 23, the wavelength of the output laser, and the spot radius of the output laser at the position of the output mirror 23 under the current pump power.

[0073] Specifically, in step S301, the formula (2) for calculating the equivalent radius of curvature of the input mirror 21 is as follows:

[0074] (2);

[0075] in, R ′ is the equivalent radius of curvature of input mirror 21. L cav R1 is the initial cavity length, and R2 is the radius of curvature of the output mirror 23. λ The wavelength of the output laser, ω This is the laser spot radius at position 23 of the output mirror under the current pump power.

[0076] Furthermore, the equivalent radius of curvature of input mirror 21 R The calculation formula (2) for ′ is derived from the theory of laser resonator 20; when the pump power is selected, the size of the laser spot radius at the position of output mirror 23 is measured. ω and the initial cavity length of resonant cavity 20 L cav Then, the equivalent radius of curvature of input mirror 21 can be calculated. R The specific derivation process is as follows:

[0077] According to the theory of laser resonator 20, the size of the laser spot radius at the output mirror 23 position is... ω It can be expressed as follows (4):

[0078] (4);

[0079] The equivalent radius of curvature of the input mirror 21 can be derived from the above formula. R The formula for calculating ′ is:

[0080] (2).

[0081] S302, the target cavity length that meets the preset mode ratio is calculated based on the preset mode ratio, the spot radius of the pump light in the laser crystal 22, the equivalent radius of curvature of the input mirror 21, the radius of curvature of the output mirror 23, and the wavelength of the output laser.

[0082] Specifically, in step S302, the formula (3) for calculating the target cavity length is as follows:

[0083] (3);

[0084] in, L cav ′ represents the target cavity length. r For preset mode ratio, ω p The radius of the pump light spot in the laser crystal 22 is denoted as .

[0085] Since the laser crystal 22 is closely attached to the input mirror 21, the radius of the output laser spot within the laser crystal 22 can be approximated as the radius of the output laser spot at the input mirror 21. Based on the theory of the laser resonator 20 and the definition of laser mode ratio, the size of the output laser spot radius at the input mirror 21 is... ω l It can be expressed as follows (5):

[0086] (5);

[0087] The target cavity length that meets the preset mode ratio can be derived from formula (5). L cav ′:

[0088] (3).

[0089] S303, the displacement control module 40 controls the high-precision electric displacement platform 41 to adjust the cavity length of the resonant cavity 20 from the initial cavity length to the target cavity length.

[0090] Specifically, by substituting the target cavity length into formula (5), the radius of the output laser spot within the laser crystal 22 can be calculated. ω l Then, the actual mode ratio of the solid-state laser can be calculated according to formula (1). At this time, the absolute value of the difference between the actual mode ratio and the preset mode ratio is less than or equal to 0.01, which indicates that the above-mentioned automatic adjustment method of the solid-state laser mode ratio has high control accuracy and can quickly and accurately adjust the solid-state laser mode ratio according to the needs.

[0091] S304, change the pump power and repeat steps S10 to S30. This allows for the automatic calculation and adjustment of the length of the resonant cavity 20 based on different pump powers, thereby controlling the size of the laser spot radius in the laser crystal 22. ω l This allows for the adjustment of the mode ratio of the solid-state laser.

[0092] The technical solution of the present invention will now be described in conjunction with specific embodiments.

[0093] Example 1:

[0094] Please see Figures 1 to 3 Embodiment 1 of the present invention first provides a device 100 for automatically adjusting the mode ratio of a solid-state laser, comprising:

[0095] Pump module 10 is used to generate pump light and couple it into the resonant cavity 20;

[0096] The resonant cavity 20 is optically connected to the pump module 10 and includes an input mirror 21, a laser crystal 22 and an output mirror 23 that are optically connected in sequence. The incident end face of the laser crystal 22 is set close to the input mirror 21.

[0097] The measurement module 30 is set close to the output end face of the output mirror 23 and is used to measure the laser spot radius and cavity length of the resonant cavity 20 at the position of the output mirror 23 to obtain test data.

[0098] The displacement control module 40 is electrically connected to the measurement module 30 and is used to adjust the cavity length of the resonant cavity 20 according to the preset mode ratio of the solid-state laser and the test data, so that the absolute value of the difference between the actual mode ratio of the solid-state laser and the preset mode ratio is less than or equal to 0.01.

[0099] In Embodiment 1 of the present invention, the pump module 10 is disposed near the incident side of the input mirror 21. The pump module 10 includes a pump source 11, a transmission optical fiber 12 and a coupling lens group 13. One end of the transmission optical fiber 12 is fused to the pump source 11, and the coupling lens group 13 is located between the transmission optical fiber 12 and the input mirror 21.

[0100] Specifically, the pump source 11 is an 808nm laser diode; the coupling lens group 13 includes two focusing lenses arranged parallel to each other. The pump light enters the laser crystal 22 after passing through the coupling lens group 13, and the beam radius of the pump light in the laser crystal 22 is controlled by the coupling lens group 13. ω p It is 0.2mm.

[0101] Specifically, the input mirror 21 is a concave mirror coated with an 808nm high-transmittance film and a 1053nm high-reflectance film, with a radius of curvature of 100mm; the laser crystal 22 is an Nd:YLF crystal with an end face size of 3mm×3mm and a crystal length of 10mm; the output mirror 23 is a concave mirror with a 15% transmittance at 1053nm, and a radius of curvature R2 of 150mm; the transmittance range of the output mirror 23 is 15%; the preset mode ratio of the solid-state laser is... r Set to 1; Output laser wavelength of the solid-state laser. λ The wavelength is 1053 nm; the distance between the input mirror 21 and the output mirror 23 is measured, which is the original cavity length of the resonant cavity 20. L cav In this example 1, the specific value is 50mm.

[0102] Specifically, the method for automatically adjusting the mode ratio of a solid-state laser in Embodiment 1 of the present invention includes the following steps:

[0103] Step 1: Set the initial power of pump source 11 to 10W and turn on pump source 11;

[0104] Step 2: Measure the radius of the laser spot output at position 23 of the output mirror using a CCD camera. ω It is 172μm;

[0105] Step 3: Based on the theory of laser resonator 20, the equivalent radius of curvature of input mirror 21 is calculated according to formula (2). R In this embodiment 1, the specific diameter is 53mm;

[0106] Step 4: According to the preset mode ratio set by the solid-state laser r Equivalent radius of curvature of input mirror 21 R The target cavity length that meets the set laser mode ratio is calculated and denoted as ′. L cav In this example, the specific diameter is 47mm.

[0107] Step 5: Adjust the distance between the input mirror 21 and the output mirror 23 through the electric displacement platform controller 42 and the high-precision electric displacement platform 41, that is, adjust the cavity length of the resonant cavity 20 to 47mm.

[0108] Step 6: Calculate the radius of the output laser spot within the laser crystal 22 according to formula (5). ω l Specifically, in this embodiment 1, the value is 202 μm;

[0109] Step 7: Calculate the actual mode ratio of the solid-state laser according to formula (1). r′ The value is 1.01. At this point, the absolute value of the difference between the actual mode ratio and the preset mode ratio is less than or equal to 0.01.

[0110] Step 8: Change the pump power and repeat steps 1 to 7. This allows for the automatic calculation and adjustment of the length of the resonant cavity 20 based on different pump powers, thereby controlling the beam radius of the output laser in the laser crystal 22. ω l Finally, the mode ratio of the solid-state laser was adjusted.

[0111] In summary, unlike existing technologies, the automatic solid-state laser mode ratio adjustment device 100 and its adjustment method provided by this invention are based on the theory of laser resonator 20. By measuring the spot radius of the output laser at the position of the output mirror 23, the equivalent radius of curvature of the input mirror 21 and the length of the resonator 20 that conforms to the set laser mode ratio are calculated. The length of the resonator 20 is adjusted by an electric displacement platform, thereby controlling the spot radius of the output laser in the laser crystal 22, thus achieving the adjustment of the solid-state laser mode ratio. The automatic solid-state laser mode ratio adjustment device 100 provided by this invention has a simple structure, is stable and reliable, has high control precision, and can quickly and accurately adjust the solid-state laser mode ratio according to requirements.

[0112] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0113] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An apparatus for automatically adjusting the mode-beam ratio of a solid state laser, characterized by, The device comprises: a pumping module for generating pumping light and coupling into the resonant cavity; the resonant cavity is optically connected with the pumping module and comprises an input mirror, a laser crystal and an output mirror which are sequentially optically connected, and the incident end surface of the laser crystal is arranged close to the input mirror; a measuring module arranged close to the exit end surface of the output mirror for measuring the spot radius of the output laser at the position of the output mirror and the cavity length of the resonant cavity to obtain test data; a displacement control module electrically connected with the measuring module for adjusting the cavity length of the resonant cavity according to the preset mode ratio of the solid-state laser and the test data, so that the absolute value of the difference between the actual mode ratio of the solid-state laser and the preset mode ratio is less than or equal to 0.

01.

2. The apparatus for automatically adjusting the mode-beam ratio of a solid-state laser of claim 1, wherein, The pumping module is arranged close to the incident side of the input mirror, and the pumping module comprises a pumping source, a transmission optical fiber and a coupling lens group; wherein one end of the transmission optical fiber is fused with the pumping source, and the coupling lens group is located between the transmission optical fiber and the input mirror.

3. The apparatus for automatically adjusting the mode-beam ratio of a solid-state laser of claim 2, wherein, The pumping source is a laser diode, and the coupling lens group comprises two focusing lenses arranged in parallel.

4. The apparatus of claim 1, wherein the means for automatically adjusting the mode-beam ratio of the solid-state laser is further characterized by: The input mirror is a concave mirror, the incident plane of the input mirror is coated with a pumping light anti-reflection film, the exit concave surface of the input mirror is coated with a laser high-reflection film for reflecting the output laser excited and output by the laser crystal; the output mirror is a concave mirror, and the transmittance of the output mirror to the output laser is 2% to 30%.

5. The apparatus of claim 1, wherein, The laser crystal comprises a rare earth doped laser crystal, and the measuring module comprises a CCD camera.

6. The apparatus of claim 1, wherein, The displacement control module comprises an electric displacement platform controller and a high-precision electric displacement platform, the electric displacement platform controller is electrically connected with the high-precision electric displacement platform and the measuring module respectively, and the input mirror and the output mirror are fixed on the high-precision electric displacement platform.

7. A method for automatically adjusting the mode-beam ratio of a solid-state laser using the apparatus of any one of claims 1 to 6, characterized in that, The adjusting method comprises: S10, providing the device for automatically adjusting the mode ratio of the solid-state laser and determining the pumping power of the pumping module and the preset mode ratio; S20, measuring the spot radius of the output laser at the position of the output mirror under the current pumping power and the initial cavity length of the resonant cavity at this time by the measuring module to obtain the test data; S30, the displacement control module adjusts the cavity length of the resonant cavity according to the preset mode ratio and the test data, so that the absolute value of the difference between the actual mode ratio of the solid-state laser and the preset mode ratio is less than or equal to 0.

01.

8. The method of claim 7, wherein the step of automatically adjusting the mode-beam ratio of the solid-state laser is performed by a controller. The S30 step specifically comprises: S301, calculating the equivalent curvature radius of the input mirror according to the initial cavity length, the curvature radius of the output mirror, the wavelength of the output laser and the spot radius of the output laser at the position of the output mirror under the current pumping power; S302, calculating the target cavity length conforming to the preset mode ratio according to the preset mode ratio, the spot radius of the pumping light in the laser crystal, the equivalent curvature radius of the input mirror, the curvature radius of the output mirror and the wavelength of the output laser. S303, the displacement control module controls the high-precision electric displacement platform to adjust the cavity length of the resonant cavity from the initial cavity length to the target cavity length.

9. The method of claim 8, wherein the step of automatically adjusting the mode-beam ratio of the solid-state laser is performed by a controller. In the S301 step, the calculation formula of the equivalent curvature radius of the input mirror is as follows: ； wherein, R R1 is the effective curvature radius of the input mirror, L cav R2 is the curvature radius of the output mirror, λ λ is the wavelength of the output laser, ω R is the spot radius of the output laser at the output mirror position for the current pump power.

10. The method of claim 9, wherein the step of automatically adjusting the mode-beam ratio of the solid-state laser is performed by a controller. In the S302 step, the calculation formula of the target cavity length is as follows: ； wherein, L cav is the target cavity length, r is the preset mode ratio, ω p is the spot radius of the pump light in the laser crystal.

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