Dynamic thermal focal length controllable module and disc laser

Abstract

The invention relates to the technical field of lasers, and discloses a dynamic thermal focal length controllable module and a disc laser, and the dynamic thermal focal length controllable module comprises a deformable mirror which is arranged on a light path of emergent laser after being pumped by a laser crystal and is used for generating a compensation surface shape conjugated with aberration of the laser crystal; the imaging assembly is arranged on a reflection light path of the deformable mirror, and light intensity distribution of the emergent laser is obtained by measuring the emergent laser reflected by the deformable mirror; and the closed-loop control module calculates the variable quantity of the deformable mirror according to the light intensity distribution, adjusts the deformable mirror according to the variable quantity, and compensates the thermally induced surface shape error of the laser crystal. According to the invention, the deformable mirror is used as a phase compensation element, and the comprehensive aberration generated by a transmission element is converted into the surface shape error of a single reflecting surface for characterization based on the self-adaptive optical principle. The surface shape of the deformable mirror is changed in a piezoelectric mode, it is ensured that the surface type of the deformable mirror can accurately correct wavefront distortion, introduced by the surface type, of the disc laser crystal, and the problem of error accumulation in multi-interface interference measurement is solved.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a dynamic thermal focus controllable module and a disk laser. Background Art

[0002] The thickness of disk laser crystals is usually in the hundreds of microns, and is used to solve the performance degradation problem caused by thermal effects (such as thermal lens effect and thermal stress) of traditional bulk laser crystals when operating at high power. The thermal lens effect of disk laser crystals will cause the multiple incident Gaussian beams to produce cumulative wavefront distortion, which will significantly reduce the laser beam quality and affect the output power and stability.

[0003] At present, interferometers are used to measure the wavefront distribution of Gaussian beams passing through disk laser crystals, calculate the thermal focal length of disk laser crystals, and compensate the surface shape of disk laser crystals according to the thermal focal length to improve the beam quality of the output laser. However, when traditional interferometers measure multi-interface optical systems, the mutual interference of reflected light from each interface will lead to the accumulation of measurement errors.

[0004] Therefore, this method has certain limitations and needs to be further optimized or combined with other measurement methods to improve the beam quality. Summary of the invention

[0005] The purpose of the present invention is to provide a dynamic thermal focus controllable module and a disk laser, which can solve at least one of the above-mentioned technical problems. The specific solution is as follows: According to a specific embodiment disclosed in the present invention, the first aspect of the present invention discloses a dynamic thermal focus controllable module, comprising: A deformable mirror is arranged on the optical path of the laser emitted after being pumped by the laser crystal, and is used to generate a compensation surface shape conjugate with the aberration of the laser crystal; An imaging component is arranged on the reflection light path of the deformable mirror, and obtains the light intensity distribution of the outgoing laser by measuring the outgoing laser reflected by the deformable mirror; The closed-loop control module calculates the variation of the deformable mirror according to the light intensity distribution, and adjusts the deformable mirror according to the variation to compensate for the thermally induced surface error of the laser crystal.

[0006] Preferably, the imaging assembly comprises: a beam splitter and a camera; The beam splitter divides the outgoing laser reflected by the deformable mirror into a first reflected light and a first transmitted light, and the camera is used to obtain the light intensity distribution of the first reflected light or the first transmitted light.

[0007] Preferably, the closed-loop control module comprises: A data processing unit, which uses a Zernike polynomial to fit the light intensity distribution, compares the fitted light intensity distribution with the Gaussian beam, and obtains a voltage amount that needs to be applied to the deformable mirror; The piezoelectric control unit drives the deformation of the deformable mirror according to the voltage, so that the light intensity of the outgoing laser reflected by the deformable mirror presents a Gaussian distribution.

[0008] Preferably, the closed-loop control module further includes: an amplification module for enhancing the driving signal of the piezoelectric control unit.

[0009] Preferably, the camera is a CMOS image sensor; and the deformable mirror is a piezoelectric deformable mirror.

[0010] Preferably, it also includes: a wavefront sensing component, which transmits detection light to the deformable mirror, receives the detection light reflected by the deformable mirror, and obtains the wavefront phase distribution of the detection light.

[0011] Preferably, the wavefront sensing assembly comprises: a detection light source, a collimating lens group and a wavefront sensor; The detection light emitted by the detection light source is collimated by the collimating lens group and then incident on the deformable mirror as parallel light, and is received by the wavefront sensor after being reflected by the deformable mirror.

[0012] According to the specific embodiments disclosed in the present invention, the second aspect of the present invention discloses a disk laser with controllable dynamic thermal focus, comprising: the above-mentioned controllable dynamic thermal focus module, a seed light source module and a multi-pass pumping module; The outgoing light beam of the seed light source module is M 2 =1 fundamental mode light; The laser crystal of the multi-pass pump module is a disk laser crystal; The deformable mirror of the dynamic thermal focus controllable module is arranged on the laser light path emitted from the multi-pass pumping module, and the deformable mirror and the laser light path have an included angle.

[0013] Compared with the prior art, the above solution of the embodiment disclosed in the present invention has at least the following beneficial effects: The present invention uses a deformable mirror as a phase compensation element, and based on the principle of adaptive optics, converts the comprehensive aberration generated by the transmission element (disk laser crystal) into a surface error of a single reflection surface for characterization. The surface shape of the deformable mirror is changed by piezoelectric means, and through continuous monitoring and adjustment, it is ensured that the surface shape of the deformable mirror can accurately correct the wavefront distortion introduced by the surface shape of the disk laser crystal, thereby solving the error accumulation problem in multi-interface interferometry and ensuring the beam quality of the output laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the disclosure of the present invention, and together with the specification, are used to explain the principles disclosed in the present invention. Obviously, the drawings described below are only some embodiments disclosed in the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings: Figure 1 A schematic diagram of an optical path of a dynamic thermal focus controllable module provided by an embodiment of the present invention; Figure 2 A schematic diagram of an optical path of a disk laser with controllable dynamic thermal focus provided by an embodiment of the present invention; Figure 3 A schematic diagram of a closed-loop control module provided in an embodiment of the present invention.

[0015] Reference numerals: 1: Dynamic thermal focus controllable module; 2: Multi-pass pump module; 3: Seed light source module; 4. Laser crystal; 1-1: Deformable mirror; 1-2 Imaging component; 1-3: Wavefront sensing component; 1-2-1: beam splitter; 1-2-2: CMOS image sensor; 1-3-1: wavefront sensor; 1-4-1: data processing unit; 1-4-2: piezoelectric control unit; 1-4-3: amplification module. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages disclosed in the present invention clearer, a dynamic thermal focus controllable module and a disk laser disclosed in the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments disclosed in the present invention, not all of the embodiments. Based on the embodiments disclosed in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection disclosed in the present invention.

[0017] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0018] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0019] It should be understood that although the terms first, second, third, etc. may be used to describe in the embodiments of the present application, these should not be limited to these terms. These terms are only used to distinguish. For example, without departing from the scope of the embodiments of the present application, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0020] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or device. In the absence of more restrictions, the elements defined by the sentence "comprises a" do not exclude the presence of other identical elements in the product or device including the elements.

[0021] The following is combined with Figure 1-3 Alternative embodiments of the present invention are described in detail.

[0022] Example 1 like Figure 1 As shown, according to a specific embodiment of the present invention, the present invention provides a dynamic thermal focus controllable module, comprising: The deformable mirror 1-1 is arranged on the optical path of the laser light emitted after being pumped by the laser crystal 4, and is used to generate a compensation surface shape conjugate with the aberration of the laser crystal 4; An imaging component 1-2 is arranged on the reflection light path of the deformable mirror 1-1, and obtains the light intensity distribution of the outgoing laser by measuring the outgoing laser reflected by the deformable mirror 1-1; The closed-loop control module calculates the variation of the deformable mirror 1 - 1 according to the light intensity distribution, and adjusts the deformable mirror 1 - 1 according to the variation to compensate for the thermally induced surface error of the laser crystal 4 .

[0023] In this embodiment, the deformable mirror 1 - 1 is used to reflect the light beam emitted by the laser crystal, and then the imaging component is used to introduce the light beam carrying the surface information of the laser crystal into different measurement optical paths.

[0024] Specifically, the light intensity distribution of the beam of light is measured using an imaging component. The imaging component 1-2 includes: a beam splitter 1-2-1 and a camera.

[0025] In this embodiment, the beam splitter 1-2-1 is set on the optical path of the outgoing laser to split the light beam with aberration introduced by the surface of the disk laser crystal into transmitted light and reflected light. A camera is set on any optical path to measure the light intensity distribution of the light spot.

[0026] As an optional implementation, the camera uses a CMOS image sensor 1-2-2 to acquire a light intensity distribution image.

[0027] As an optional implementation, the deformable mirror adopts a piezoelectric deformable mirror. When different voltages are applied to the piezoelectric material, the local deformation of the mirror surface can be controlled, thereby correcting the wavefront distortion.

[0028] In this embodiment, the light intensity distribution information is obtained by measuring the light beam reflected by the deformable mirror, and the beam quality information of the laser beam is fitted according to the light intensity distribution. It is compared with the ideal Gaussian beam, and the amount of voltage required to be applied to the deformable mirror is calculated. The surface shape of the deformable mirror is adjusted to make the light intensity of the light beam Gaussian distributed, thereby forming a closed-loop control.

[0029] like Figure 3 As shown, the closed-loop control module includes: The data processing unit 1-4-1 uses a Zernike polynomial to fit the light intensity distribution, compares the fitted light intensity distribution with the Gaussian beam, and calculates the voltage that needs to be applied to the deformable mirror; The piezoelectric control unit 1-4-2 drives the deformation of the deformable mirror according to the voltage amount, so that the light intensity of the outgoing laser reflected by the deformable mirror presents a Gaussian distribution.

[0030] The amplification module 1-4-3 is used to enhance the driving signal of the piezoelectric control unit to ensure that the deformable mirror can obtain sufficient driving force to achieve the required deformation.

[0031] The entire process forms a closed-loop control system, which ensures that the surface shape of the deformable mirror can accurately correct the aberration introduced by the surface shape of the disk laser crystal through continuous monitoring and adjustment, thereby ensuring the beam quality of the output laser.

[0032] Example 2 Based on the introduction of the deformable mirror in Example 1, since the wavefront phase distribution of the light wave passing through the deformable mirror 1-1 is conjugate with the wavefront phase distribution passing through the disk crystal 4, the wavefront curvature radius of the laser crystal can be obtained by adding a wavefront sensor component, and the thermal focal length of the laser crystal can be further obtained.

[0033] like Figure 2As shown, the wavefront sensing component 1-3 includes: a detection light source, a collimating lens group and a wavefront sensor 1-3-1. The detection light emitted by the detection light source is collimated by the collimating lens group and then incident on the deformable mirror 1-1 as parallel light, and is received by the wavefront sensor 1-3-1 after being reflected by the deformable mirror 1-1.

[0034] Specifically, the wavefront sensor 1-3-1 is used to characterize the surface shape of the laser crystal in real time. When the light beam is incident on the wavefront sensor 1-3-1, the microlens array on the wavefront sensor 1-3-1 divides the light beam into many tiny sub-apertures. After passing through the microlens, each part of the light wave converges on the sub-aperture focus to form a sub-aperture spot array image; when the incident light wave is an ideal plane wave, a set of uniform and regularly distributed focuses will be obtained at the focus of the microlens array. When the incident light wave has wavefront distortion, the array image obtained at the focal plane of the microlens array will no longer be uniformly distributed, but will be offset from the focus of the aforementioned ideal wavefront; the offset is the wavefront slope, and the wavefront phase distribution of the light wave passing through the deformable mirror 1-1 can be reconstructed through the wavefront restoration algorithm based on the wavefront slope. Since the wavefront phase distribution of the light wave passing through the deformable mirror 1-1 is conjugate with the wavefront phase distribution passing through the disk crystal 4, the wavefront curvature radius of the laser crystal 4 is calculated, and then the thermal focal length of the disk crystal 4 is calculated.

[0035] Therefore, this embodiment measures the surface shape of the deformable mirror and converts the comprehensive aberration produced by the transmission element (disk laser crystal) into the surface shape error of a single reflection surface for characterization, thereby avoiding the problem of multi-interface errors introduced by traditional wavefront sensors or interferometers when measuring the surface shape of the disk laser crystal.

[0036] Example 3 The present invention also provides a device embodiment that is consistent with the above embodiment. The explanation based on the same name meaning is the same as the above embodiment, and has the same technical effect as the above embodiment, which will not be repeated here.

[0037] Combination Figure 2 As shown, the present invention discloses a dynamic thermal focus controllable disk laser, comprising: a dynamic thermal focus controllable module 1, a seed light source module 3 and a multi-pass pumping module 2.

[0038] Among them, the outgoing beam of the seed light source module is M 2 =1, the laser crystal of the multi-pass pump module 2 that generates pump light is a disk laser crystal 4, which generates laser output under the joint action of the seed light. The dynamic thermal focus controllable module 1 is set on the laser light path emitted by the multi-pass pump module 2. In order to achieve the measurement of the emitted laser, the deformable mirror 1-1 has an angle with the laser light path. The positions and functions of the other multiple optical elements set to meet the laser output in the figure are not described in detail.

[0039] In this embodiment, the complex transmission wavefront measurement is converted into a relatively simple reflection surface shape measurement through the conjugate compensation characteristics of the deformable mirror. By measuring the deformable mirror, the thermal focal length of the disk crystal can be obtained by inversion, and the system error of the interferometer can be corrected, avoiding the problem of multi-interface errors introduced by traditional wavefront sensors or interferometers when measuring the surface shape of the disk laser crystal. It is also possible to calculate the light intensity distribution of the emitted laser, adjust the deformable mirror according to the change, compensate for the thermally induced surface shape error of the laser crystal, and improve the beam quality.

[0040] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0041] The above embodiments are only used to illustrate the technical solutions disclosed in the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments disclosed in the present invention.

Claims

1. A dynamic thermal focus controllable module, characterized in that: include: A deformable mirror is arranged on the optical path of the laser emitted after being pumped by the laser crystal, and is used to generate a compensation surface shape conjugate with the aberration of the laser crystal; An imaging component is arranged on the reflection light path of the deformable mirror, and obtains the light intensity distribution of the outgoing laser by measuring the outgoing laser reflected by the deformable mirror; A closed-loop control module calculates a change in the deformable mirror according to the light intensity distribution, and adjusts the deformable mirror according to the change to compensate for the thermally induced surface error of the laser crystal.

2. The dynamic thermal focus controllable module according to claim 1, characterized in that: The imaging assembly comprises: a beam splitter and a camera; The beam splitter divides the outgoing laser reflected by the deformable mirror into a first reflected light and a first transmitted light, and the camera is used to obtain the light intensity distribution of the first reflected light or the first transmitted light.

3. The dynamic thermal focus controllable module according to claim 1, characterized in that: Closed-loop control module, including: A data processing unit, which uses a Zernike polynomial to fit the light intensity distribution, compares the fitted light intensity distribution with the Gaussian beam, and obtains a voltage amount that needs to be applied to the deformable mirror; The piezoelectric control unit drives the deformation of the deformable mirror according to the voltage, so that the light intensity of the outgoing laser reflected by the deformable mirror presents a Gaussian distribution.

4. The dynamic thermal focus controllable module according to claim 3, characterized in that: The closed-loop control module further includes: an amplification module, which is used to enhance the driving signal of the piezoelectric control unit.

5. The dynamic thermal focus controllable module according to claim 2, characterized in that: The camera is a CMOS image sensor; the deformable mirror is a piezoelectric deformable mirror.

6. The dynamic thermal focus controllable module according to any one of claims 1 to 5, characterized in that: Also includes: The wavefront sensing component transmits detection light to the deformable mirror, receives the detection light reflected by the deformable mirror, and obtains the wavefront phase distribution of the detection light.

7. The dynamic thermal focus controllable module according to claim 6, characterized in that: The wavefront sensing component comprises: a detection light source, a collimating lens group and a wavefront sensor; The detection light emitted by the detection light source is collimated by the collimating lens group and then incident on the deformable mirror as parallel light, and is received by the wavefront sensor after being reflected by the deformable mirror.

8. A disk laser with controllable dynamic thermal focus, characterized in that: It comprises a dynamic thermal focus controllable module, a seed light source module and a multi-pass pumping module as described in any one of claims 1 to 7; The outgoing light beam of the seed light source module is M 2 =1 fundamental mode light; The laser crystal of the multi-pass pump module is a disk laser crystal; The deformable mirror of the dynamic thermal focus controllable module is arranged on the laser light path emitted from the multi-pass pumping module, and the deformable mirror and the laser light path have an included angle.

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