A cavity-stabilized disk laser with dynamically adjustable cavity length and a control method thereof

Abstract

The present invention relates to the field of laser technology, and provides a cavity-stabilized disk laser with dynamically adjustable cavity length and a method thereof, comprising: a laser optical path, comprising an end mirror, a first reflector, a disk laser crystal and a plurality of reflectors arranged in sequence along the optical path direction, wherein the end mirror is connected to a first piezoelectric control mirror frame and is arranged on an electric displacement platform, and the first reflector is connected to a second piezoelectric control mirror frame; a calibration optical path, used for calibrating the beam directivity at the disk laser crystal, the end mirror and the first reflector, when the disk laser crystal is working, the curvature changes, resulting in a change in the radius of the laser spot in the cavity at the disk, the position of the laser spot at the disk is changed by adjusting the electric displacement platform to translate the end mirror, and the adjustment will cause the beam directivity of the laser optical path to change, and the first piezoelectric control mirror frame and the second piezoelectric control mirror frame are assisted in adjusting the beam directivity of the laser optical path.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a cavity-stabilized disk laser with dynamically adjustable cavity length and a control method thereof. Background Art

[0002] Since its advent, laser technology has been continuously developing, and solid-state lasers have been widely used in basic scientific research, industrial processing, and people's livelihood medical fields. Traditional solid-state lasers have serious thermal effects that limit the improvement of output laser parameters, hindering their further development. In order to improve the thermal management capabilities of solid-state lasers, slab lasers, fiber lasers, and disk lasers have been developed from traditional rod lasers. Compared with slab lasers and fiber lasers, disk lasers have the advantages of high peak power, high energy, and high beam quality.

[0003] Conventional disk lasers usually require a lot of experimental optimization and comparison of cavity types in order to keep the laser output in the fundamental transverse mode, so that the curvature of the disk laser crystal changes when heated and always works within the stable range, and the laser spot radius at the disk meets the mode matching requirements to keep the output laser in the fundamental transverse mode. In addition, the hot air effect generated by the air in front of the disk laser crystal when it is working will affect the directivity of the beam in the cavity and reduce the efficiency and stability of the laser. Summary of the invention

[0004] Some embodiments of the present application provide a cavity-stabilized disk laser with dynamically adjustable cavity length, including:

[0005] A laser optical path, comprising an end mirror, a first reflecting mirror, a disk laser crystal and a plurality of reflecting mirrors arranged in sequence along the optical path direction, wherein the end mirror is connected to a first piezoelectrically controlled mirror frame and is arranged on an electric displacement platform, the first reflecting mirror is connected to a second piezoelectrically controlled mirror frame, the yaw and pitch angles of the end mirror are adjusted by the first piezoelectrically controlled mirror frame, the displacement of the end mirror is adjusted by the electric displacement platform, and the yaw and pitch angles of the first reflecting mirror are adjusted by the second piezoelectrically controlled mirror frame;

[0006] The calibration optical path is used to calibrate the light beam directivity at the disk laser crystal, the end mirror and the first reflector. When the disk laser crystal is working, the curvature changes, resulting in a change in the radius of the laser spot in the cavity at the disk. The radius of the laser spot at the disk laser crystal is changed by adjusting the electric displacement platform to translate the position of the end mirror. The adjustment will cause the light beam directivity of the laser optical path to change. The first piezoelectric control mirror frame and the second piezoelectric control mirror frame are assisted in adjusting the light beam directivity of the laser optical path.

[0007] In some embodiments, the calibration optical path includes: an initial optical path, a reference optical path, and a detection optical path;

[0008] Among them, the initial optical path includes the laser emitted from the first laser light source passing through the spectroscope and the laser optical path and then entering the detector; the reference optical path includes the laser emitted from the second laser light source passing through the spectroscope and then entering the detector; the detection optical path includes the laser emitted from the second laser light source passing through the spectroscope and the laser optical path and then entering the detector.

[0009] In some embodiments, the path of the detection light path from the beam splitter to the detector overlaps with the initial light path, and the initial light path, the reference light path and the detection light path coincide at the center of the light spot of the detector.

[0010] In some embodiments, the calibration optical path includes:

[0011] The zoom lens is used to adjust the size of the light spot of the initial light path and the detection light path on the detector by adjusting the focal length of the zoom lens.

[0012] In some embodiments, the wavelength of the laser emitted by the first laser light source, the wavelength of the laser emitted by the second laser light source, the wavelength of the laser output by the laser light path and the wavelength of the pump light used by the laser are different.

[0013] In some embodiments, it also includes:

[0014] A piezoelectric controller is electrically connected to the first piezoelectric-controlled mirror frame, the electric displacement platform and the second piezoelectric-controlled mirror frame to synchronously or asynchronously control the displacement and / or yaw and pitch angles of the first piezoelectric-controlled mirror frame, the electric displacement platform and the second piezoelectric-controlled mirror frame.

[0015] In some embodiments, it also includes:

[0016] A central control unit is connected to the piezoelectric controller and the detector, and is configured to adjust the control instructions of the piezoelectric controller according to the light spot conditions output by the detector.

[0017] The present application also provides a method for controlling a laser according to any one of the above embodiments,

[0018] During the operation of the laser, the pitch and tilt angles of the end mirror are regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the pitch and tilt angles of the first reflector are regulated by the second piezoelectric control mirror frame, so that the initial optical path, the reference optical path, and the detection optical path coincide at the center of the light spot of the detector;

[0019] When the size of the detection spot of the detection light path on the detector changes, adjusting the focal length of the zoom lens to determine the direction and size of the curvature change of the disk laser crystal;

[0020] Based on the direction and magnitude of the curvature change of the disc laser crystal, the pitch and tilt angles and displacements of the end mirror are again regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the pitch and tilt angles of the first reflector are regulated by the second piezoelectric control mirror frame, so that the initial optical path, the reference optical path, and the detection optical path coincide at the center of the light spot of the detector.

[0021] In some embodiments, an initialization calibration step is also included, including:

[0022] Calibrate the relationship between the first driving voltage and the offset angle of the first piezoelectric control mirror frame; and / or;

[0023] Calibrate the relationship between the second driving voltage and the offset angle of the second piezoelectric controlled mirror frame; and / or;

[0024] Calibrate the relationship between the third driving voltage and the displacement distance of the electric displacement platform; and / or;

[0025] The relationship between the fourth driving voltage and the focal length of the zoom lens is calibrated.

[0026] In some embodiments, the step of controlling the pitch angle and displacement of the end mirror by the electric displacement platform and the first piezoelectric control mirror frame, and controlling the pitch angle of the first reflector by the second piezoelectric control mirror frame, comprises:

[0027] The light spot condition output by the detector is displayed by a central control unit, and the control instructions of the piezoelectric controller are adjusted based on the light spot condition, so that the pitch and tilt angles and displacement of the end mirror are regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the pitch and tilt angles of the first reflecting mirror are regulated by the second piezoelectric control mirror frame.

[0028] Compared with the related art, the above solution of the embodiment of the present application has at least the following beneficial effects:

[0029] The present invention is to weaken the influence of the change of the self-curvature caused by the thermal effect of the disk laser crystal on the properties of the resonant cavity, and proposes a disk laser that can change the cavity length of the resonant cavity in real time and its control method. The external calibration optical path is used to measure the direction and size of the change of the curvature of the disk laser crystal in real time, and guide the direction and size of the change of the cavity length, so that the laser output laser maintains a good beam quality. At the same time, in order to overcome the influence of the hot air wedge effect of the disk laser itself and the movement of the electric displacement platform on the directivity of the beam in the resonant cavity, the external calibration optical path is used with the piezoelectric mirror frame in the cavity and the computer image recognition and piezoelectric control software to form a closed-loop system, and the piezoelectric mirror frame in the cavity is adjusted in real time to ensure the stable operation of the disk laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0031] Figure 1 A schematic diagram of the laser optical path structure of a disk laser provided in some embodiments of the present application;

[0032] Figure 2 A schematic diagram of the overall optical path structure of a disk laser provided in some embodiments of the present application;

[0033] Figure 3 A schematic flow chart of a disk laser control method provided in some embodiments of the present application.

[0034] Description of reference numerals:

[0035] Output mirror 1, fifth reflector 2, heat sink 3, disk laser crystal 4, third reflector 5, sixth reflector 6, fourth reflector 7, second reflector 8, end mirror 9, first piezoelectric controlled mirror frame 91, first reflector 10, second piezoelectric controlled mirror frame 101, electric displacement platform 11, second laser light source 12, first fixed focus lens 13, second fixed focus lens 14, beam splitter 15, fourth focus lens 16, detector 17, zoom lens 18, beam splitter plane mirror 19, third fixed focus lens 20, first laser light source 21, first silver-coated reflector 22, fourth silver-coated reflector 23, second silver-coated reflector 24, third silver-coated reflector 25, fifth silver-coated reflector 26, piezoelectric controller 27, central control unit 28. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The disk laser crystal (hereinafter referred to as the disk) is not only used as a gain medium in the laser construction process, but also as a folding mirror or end mirror in the resonant cavity. Its front surface is coated with a high-reflection film for the output laser wavelength and the pump light wavelength, and its rear surface is coated with a high-transmittance film for the output laser wavelength and the pump light wavelength. Depending on the different surface shapes of the disk, it is usually equivalent to a plane mirror or a spherical reflector with different curvature radii in the resonant cavity design. Although the disk technology has efficient thermal management capabilities, during the operation of the laser, as the pump power increases, the surface shape of the disk will still change to a certain extent, affecting the performance of the resonant cavity.

[0042] Conventional disk lasers usually require a lot of experimental optimization and comparison of the cavity type in order to keep the laser output in the fundamental transverse mode, so that the curvature of the disk laser crystal changes when heated and always works within the stable range. At the same time, the laser spot size at the disk needs to meet the mode matching requirements to keep the output laser in the fundamental transverse mode. The hot air effect generated by the air in front of the disk laser crystal when it is working will affect the directivity of the light beam in the cavity, reducing the efficiency and stability of the laser. At the same time, the change in the radius of curvature of the disk crystal when it is working will make the laser spot size at the disk not meet the mode matching requirements. The above problems have caused troubles for the stable output of high-quality fundamental transverse mode by the laser.

[0043] To this end, the present invention provides a disk laser with dynamically adjustable cavity length and its adjustment method. The main method is to install the end mirror in the resonant cavity of the disk laser on a slowly moving electric displacement platform. The end mirror is a 0° plane reflector. The end mirror is controlled by a computer and an electric displacement platform. It is translated in real time according to the change of the radius of curvature at the disk to control the overall cavity length of the disk laser resonant cavity, ensuring that the laser always maintains a good fundamental transverse mode output. At the same time, an external optical path is used to calibrate the pitch and yaw positions of the electric adjustable mirror frame in the resonant cavity and the end mirror installed at the electric displacement platform, so as to maintain the directivity of the optical path in the resonant cavity when the electric displacement platform is translated and the disk laser crystal produces a hot air wedge effect, thereby ensuring the stability of the light output of the disk laser.

[0044] The present application is described in detail below with reference to the accompanying drawings.

[0045] The present invention is based on a stable cavity disk laser. When the disk laser is working, the disk laser crystal will be affected by the thermal effect and will produce certain deformation. Combined with the changes in other physical parameters of the disk laser crystal when heated, the disk laser crystal can be equivalent to a convex reflector or a concave reflector in the cavity when working. When the disk laser crystal is heated, the equivalent curvature of the equivalent spherical reflector will change synchronously with the output laser power or pump power. This change is dynamic and monotonic. Normally, when the diameter of the laser spot at the disk is 0.7-0.8 times the diameter of the pump spot, the laser output of the laser is a good fundamental transverse mode with good beam quality. When the laser spot at the disk exceeds this range, the output laser tends to evolve into a high-order mode or becomes a high-order mode. When the radius of curvature of the spherical reflector in the resonant cavity of the disk laser changes, the diameter of the laser spot at the disk will also change accordingly. When the ratio of the spot diameter at the disk to the pump spot diameter exceeds the above range, the quality of the output laser beam will deteriorate and it will be impossible to maintain a stable fundamental transverse mode output. In addition to the change in the radius of curvature of the spherical reflector in the resonant cavity affecting the size of the laser spot at the disk, the cavity length of the resonant cavity is also a key parameter affecting the size of the laser spot at the disk. Therefore, in order to ensure that the disk laser can achieve stable fundamental transverse mode spot output and overcome the change in the size of the laser spot at the disk caused by the thermal effect of the disk crystal, the present invention places an end mirror in the resonant cavity of the disk laser on an electric displacement platform, and the electric displacement platform is parallel to the direction of the light path incident to the end mirror. During the operation of the laser, the end mirror in the resonant cavity is translated by the electric displacement platform to adjust the length of the resonant cavity, overcome the influence of the thermal lens effect of the disk laser crystal on the size of the laser spot at the disk, and keep the output laser spot in the fundamental transverse mode state.

[0046] The specific optical path diagram is as follows Figure 1As shown, some embodiments of the present application provide a cavity-stabilized disk laser with dynamically adjustable cavity length, comprising: a laser optical path, comprising an end mirror 9, a first reflector 10, a disk laser crystal 4, a plurality of reflectors and an output mirror 1 arranged in sequence along the optical path direction, the optical path from the end mirror 9 to the output mirror 1 constitutes a resonant cavity of the disk laser, the number, position and parameters of the plurality of reflectors vary slightly depending on the cavity design, in the embodiment given in the present application, the plurality of reflectors include a second reflector 8, a third reflector 5, a fourth reflector 7, a fifth reflector 2 and a sixth reflector 6; wherein the second reflector 8 is a concave reflector, and the third reflector 5 is a convex reflector. In order to adjust the resonant cavity, the end mirror 9 is connected to the first piezoelectric control mirror frame 91 and is arranged on the electric displacement platform 11, and the first reflector 10 is connected to the second piezoelectric control mirror frame 101. The yaw angle and pitch angle of the end mirror 9 are adjusted by the first piezoelectric control mirror frame 91, the displacement of the end mirror 9 is adjusted by the electric displacement platform 11, and the yaw angle and pitch angle of the first reflector 10 are adjusted by the second piezoelectric control mirror frame 101. The present invention is applicable to a stable cavity disk laser, so the cavity length is usually longer, the 0° end mirror 9 and the 0° first reflector 10 are both plane reflectors and the laser spot at their positions is larger, so these two mirrors are selected for piezoelectric control, which is not easy to cause component damage.

[0047] Specifically, the output mirror 1 is a 0° output mirror, the fourth reflector 7, the fifth reflector 2, and the sixth reflector 6 are 0° reflectors in the resonant cavity; the disk laser crystal 4 is placed on the heat sink 3 of the disk laser crystal, and the heat sink 3 is mostly made of diamond, silicon carbide, copper tungsten and other materials; the disk laser crystal 4 widely uses Yb:YAG, Yb:KGW, Yb:CALGO, Yb:LuScO3, Ho:YAG, Ho:KYW, Tm:YAG, Tm:KYW, Cr:ZnSe and Tm:LLF and other materials; the third reflector 5 is a convex reflector in the resonant cavity; the second reflector 8 is a concave reflector in the resonant cavity; the end mirror 9 is a 0° reflector in the resonant cavity, and is also the end mirror in the resonant cavity; the first reflector 10 is a 0° reflector in the resonant cavity. When the disk laser is working, the hot air in front of the disk laser crystal 4 will produce a hot air wedge effect, resulting in poor directivity of the beam in the cavity. In addition, although the mechanical parts of the electric displacement platform will be parallel to the light path incident to the 0° reflector 9 during the cavity adjustment. However, during the translation of the electric displacement stage 11, due to the directivity of the mechanical parts and other issues, its movement direction will inevitably produce a certain small angle with the direction of the light path, thereby affecting the directivity of the light beam in the cavity. In order to ensure the stability of the directivity of the light beam in the cavity, the 0° reflector 9 is installed on the first piezoelectric control mirror frame 91, and the 0° reflector 10 is installed on the second piezoelectric control mirror frame 101, and the pitch and yaw angles are adjusted by external voltage control to suppress the change of the light beam direction in the cavity.

[0048] Among them, the output mirror 1 is a 0° output mirror in the disk laser resonant cavity, which is used to partially reflect the laser incident at 0° and output the laser in the cavity at the same time; the fifth reflector 2 is a 0° plane reflector in the disk laser resonant cavity, which is used to fully reflect the laser incident at 0°; the heat sink 3 is a heat sink for the disk laser crystal, which is mostly made of diamond, silicon carbide, copper tungsten and other materials; the disk laser crystal 4 widely uses Yb:YAG, Yb:KGW, Yb:CALGO, Yb:LuScO3, Ho:YAG, Ho:KYW, Tm:YAG, Tm:KYW, Cr:ZnSe and materials such as Tm:LLF; the third reflector 5 is a convex reflector in the disc laser resonant cavity, which is used to expand the divergence angle of the incident laser and reflect the seed light at the same time; the sixth reflector 6 is a 0° plane reflector in the disc laser resonant cavity, which is used to fully reflect the laser incident at 0°; the fourth reflector 7 is a 0° plane reflector in the disc laser resonant cavity, which is used to fully reflect the laser incident at 0°; the second reflector 8 is a concave reflector in the disc laser resonant cavity, which is used to reduce the divergence angle of the incident laser and reflect the seed light at the same time; the end mirror 9 is a 0° plane reflector in the disc laser resonant cavity, which is installed on the piezoelectric control mirror frame, which is used to fully reflect the laser incident at 0°; the first reflector 10 is a 0° plane reflector in the disc laser resonant cavity, which is installed on the piezoelectric control mirror frame, which is used to fully reflect the laser incident at 0°; the electric displacement platform 11 is an electric displacement platform, which is connected to the piezoelectric controller and is used to translate the position of a piezoelectric control mirror frame 91 fixed thereon in real time.

[0049] In order to ensure the stability of the directivity of the light beam in the cavity, the present application uses an extra-cavity calibration optical path to calibrate the directivity of the light beam at the disc, 0° reflector 9 and 0° reflector 10. When the directivity of the light beam in the cavity of the working disc laser changes, the extra-cavity calibration optical path is used to control and guide the offset of the piezoelectric mirror frame of 0° reflector 9 and 0° reflector 10, thereby assisting in adjusting the direction of the light path in the cavity.

[0050] like Figure 2 As shown, in order to guide the adjustment of the resonant cavity, the disk laser of the present application also includes a calibration optical path, which is used to calibrate the light beam directivity of the disk laser crystal 4, the end mirror 9 and the first reflector 10. When the disk laser crystal is working, the curvature changes, resulting in a change in the radius of the laser spot in the cavity at the disk. The radius of the laser spot at the disk is changed by adjusting the position of the end mirror of the electric displacement platform. At the same time, the adjustment will cause the light beam direction of the laser light path to change, and the first piezoelectric control mirror frame and the second piezoelectric control mirror frame are assisted in adjusting the light beam direction of the laser light path.

[0051] In some embodiments, the calibration optical path includes: an initial optical path, a reference optical path and a detection optical path; wherein the initial optical path includes the laser emitted from the first laser light source 21, which enters the laser optical path as described above through the spectroscope 15 and then returns to the detector 17, and the detector 17 is, for example, a camera or other spot detector; the reference optical path includes the laser emitted from the second laser light source 12, which enters the detector 17 through the spectroscope 15; the detection optical path includes the laser emitted from the second laser light source 12, which enters the laser optical path as described above through the spectroscope 15 and then returns to the detector 17.

[0052] In some embodiments, the path of the detection light path from the beam splitter 15 to the detector 17 overlaps with the initial light path, and the initial light path, the reference light path, and the detection light path coincide at the center of the light spot of the detector. In actual operation, the coincidence of the center of the light spot means that the directivity of the light beam does not change, indicating that the directivity of the light path is corrected. Specific experiments require designing a control algorithm based on a fixed light spot radius or designing a control algorithm based on a variable light spot radius to achieve the coincidence of the center of the light spot.

[0053] In some embodiments, the calibration optical path includes a zoom lens 18, which is used to adjust the spot size of the initial optical path and the detection optical path on the detector 17 by adjusting the focal length of the zoom lens 18.

[0054] In some embodiments, the laser wavelength emitted by the first laser light source 21, the laser wavelength emitted by the second laser light source 12 and the laser wavelength output by the laser optical path are different. To ensure that the optical information recognized by the detector 17 is accurate, the laser band and power of the first laser light source 21 and the second laser light source 12 should be appropriately selected to avoid overlap with the laser pump light and output laser band. Optionally, a bandpass filter can be used in front of the detector 17 to attenuate stray light, and the output laser power is appropriately selected during use to ensure clear imaging at the detector 17 without damaging the detector elements.

[0055] As above Figure 2As shown, the black light is the light beam in the laser resonant cavity, the gray light is the calibration light beam outside the resonant cavity, the initial light beam is emitted by the laser 21 light source, after being collimated by the third fixed focus lens 20, it is transmitted to the splitter plane mirror 19, and then transmitted through the splitter prism 15, the light beam passes through the zoom lens 18 and is reflected by the first silver-coated reflector 22 to the disk laser crystal 4, after being reflected by the disk laser crystal 4, it is incident on the second silver-coated reflector 24, after being reflected by the second silver-coated reflector 24, it is incident on the 0° end mirror 9 in the resonant cavity, after being reflected by the 0° end mirror 9 in the resonant cavity, it is incident on the third silver-coated reflector 25, after being reflected by the third silver-coated reflector 25, it is incident on the fourth silver-coated reflector 23 , after being reflected by the fourth silver-coated reflector 23, it is incident on the 0° first reflector 10 in the resonant cavity, after being reflected by the 0° first reflector 10 in the resonant cavity, it is incident on the fifth silver-coated reflector 26, and the fifth silver-coated reflector 26 is adjusted so that the initial light emitted by the laser 21 light source returns along the original path, passes through the 0° first reflector 10, the fourth silver-coated reflector 23, the third silver-coated reflector 25, the 0° end mirror 9, the second silver-coated reflector 24, the disk laser crystal 4, the first silver-coated reflector 22, and the zoom lens 18 in the above figure, and then is reflected by the beam splitter prism 15, and then is focused on the position of the detector 17 through the fourth fixed-focus lens 16. At this time, the position of the light spot at the detector 17 is the origin. This light spot is the initial light spot, and its position carries the initial position information of the disk laser crystal 4, the 0° end mirror 9 and the 0° first reflector 10 in the resonant cavity.

[0056] The laser emitted by the second laser light source 12 is expanded and collimated by the first fixed-focus lens 13 and the second fixed-focus lens 14, and then transmitted through the beam splitter prism 15, and then focused by the fourth fixed-focus lens 16 and imaged on the detector 17. This light spot is called the reference light spot; another part of the light is reflected by the beam splitter prism 15 and then incident on the first silver-coated reflector 22 through the zoom lens 18. The position of the second laser light source 12 and the angle of the beam splitter prism 15 are carefully adjusted so that this light beam coincides with the initial light beam and is also imaged at the position of the detector 17. This light spot is called the detection light spot. The pixel centers of the initial light spot, the reference light spot, and the detection light spot are extracted using image processing technology so that the pixel centers of the three light spots coincide at the position of the detector 17.

[0057] In some embodiments, a piezoelectric controller 27 is also included, and the piezoelectric controller 27 is electrically connected to the first piezoelectric-controlled mirror frame 91, the electric displacement platform 11 and the second piezoelectric-controlled mirror frame 101 to synchronously or asynchronously control the displacement and / or angle of the first piezoelectric-controlled mirror frame 91, the electric displacement platform 11 and the second piezoelectric-controlled mirror frame 101.

[0058] In some embodiments, a central control unit 28 is also included. The central control unit 28 is, for example, a computer, connected to the piezoelectric controller 27 and the detector 17, and configured to adjust the control instructions of the piezoelectric controller 27 according to the light spot conditions output by the detector 17. When the voltage parameter changes of the electric translation stage 11 and the first and second piezoelectric mirror frames are guided by the extracavity light beam, the piezoelectric controller 27 is connected to the central control unit 28, and the central control unit 28 presents the imaging light spot conditions at the detector 17 in real time, and uses image processing technology to close the loop and guide the piezoelectric controller to issue voltage instructions in real time.

[0059] Among them, the second laser light source 12 is used as a reference light and detection light laser light source, the first fixed-focus lens 13 is used for beam expansion and collimation of the calibration light; the second fixed-focus lens 14 is used for beam expansion and collimation of the calibration light; the beam splitter 15 is used for beam splitting; the fourth focal lens 16 is used for converging the initial calibration light, reference light and detection light; the detector 17 is a camera or other spot detector with high resolution and response speed, which is used to image the calibration spot, reference spot and detection spot; the zoom lens 18 is an electro-deformation driven zoom lens, which provides lenses with different focusing capabilities to cause different degrees of deflection of the incident parallel light; the beam splitter plane mirror 19 is used to realize 180° directional reflection of part of the light beam. , part of the light beam is transmitted; the third fixed-focus lens 20 is used to converge the laser output of the laser; the first laser light source 21 is a calibration light laser light source; the first silver-coated reflector 22, the fourth silver-coated reflector 23, the second silver-coated reflector 24, the third silver-coated reflector 25, and the fifth silver-coated reflector 26 are used to reflect the incident light; the piezoelectric controller 27 is connected to the central control unit 28 and the piezoelectric control device, and outputs a voltage to control the piezoelectric device after receiving the command issued by the central control unit 28; the central control unit 28 is, for example, a computer, connected to the detector and the piezoelectric control device, and is used for image processing and analysis of changes in the detection spot position and real-time closed-loop control of the piezoelectric device.

[0060] like Figure 3 As shown, the present application also provides a method for controlling a laser according to any one of the above embodiments, comprising the following method steps:

[0061] Step S102: During the operation of the laser, the yaw, pitch and displacement of the end mirror are regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the yaw and pitch of the first reflector are regulated by the second piezoelectric control mirror frame, so that the initial optical path, the reference optical path and the detection optical path coincide at the center of the light spot of the detector;

[0062] Step S104: when the initial light path, the reference light path and the detection light path do not overlap in the light spot of the detector, that is, when the radius of the detection light spot changes, adjusting the focal length of the zoom lens, observing the change of the radius of the detection light spot, so as to determine the direction and magnitude of the curvature change of the disk laser crystal;

[0063] Step S106: Based on the direction and magnitude of the curvature change of the disk laser crystal, the displacement and the yaw and pitch angles of the end mirror are again regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the yaw and pitch angles of the first reflector are regulated by the second piezoelectric control mirror frame, so that the initial optical path, the reference optical path and the detection optical path coincide at the center of the light spot of the detector.

[0064] When the disk laser is working, the first piezoelectric mirror frame 91 is first used to control the yaw angle and pitch angle of the 0° end mirror 9 and the 0° first reflector 10, so that the position of the detection spot always coincides with the center position of the initial spot and the reference spot, and the laser optical path is in a stable output state. Due to the influence of thermal effect, the position and size of the detection spot will change. At this time, by adjusting the focal length of the deformable mirror 18, the size of the detection spot will be observed to change. According to the change of the detection spot size, the direction and size of the curvature change of the disk laser crystal 4 can be determined. According to the direction and size of the curvature change of the disk laser crystal 4 and the properties of the laser resonant cavity, the 0° end mirror 9 on the electric displacement 11 is appropriately and slowly translated. At the same time, the first piezoelectric mirror frame 91 and the second piezoelectric mirror frame 101 are always used to control the yaw angle and pitch angle of the 0° end mirror 9 and the 0° first reflector 10, so that the position of the detection spot coincides with the center position of the calibration spot and the reference spot, thereby overcoming the influence of the poor beam quality caused by the thermal lens effect.

[0065] The present application utilizes the changes in the size of the detection light spot relative to itself and the changes in the relative positions to the initial light spot and the reference light spot to guide the changes in the focal length of the zoom lens 18 and the changes in the first and second piezoelectric mirror frames. The direction and size of the translation of the electric translation stage 11 are guided by the changes in the focal length of the zoom lens 18. During the entire operation of the laser, the first and second piezoelectric mirror frames always maintain a dynamically adjusted working state, thereby maintaining the stability of the directivity of the light beam in the cavity.

[0066] In some embodiments, an initialization calibration step is also included, and the initialization calibration step includes: calibrating the relationship between the first driving voltage and the offset angle of the first piezoelectric control mirror frame; calibrating the relationship between the second driving voltage and the offset angle of the second piezoelectric control mirror frame; calibrating the relationship between the third driving voltage and the displacement distance of the electric displacement platform; calibrating the relationship between the fourth driving voltage and the focal length of the zoom lens.

[0067] In some embodiments, the electric displacement platform and the first piezoelectric control mirror frame are used to control the yaw and pitch angles and displacements of the end mirror, and the second piezoelectric control mirror frame is used to control the yaw and pitch angles of the first reflector, including: displaying the light spot conditions output by the detector through a central control unit, and adjusting the control instructions of the piezoelectric controller based on the light spot conditions, thereby controlling the yaw and pitch angles and displacements of the end mirror through the electric displacement platform and the first piezoelectric control mirror frame, and controlling the yaw and pitch angles of the first reflector through the second piezoelectric control mirror frame.

[0068] In the initial state, the voltage of the electric displacement platform 11 is defined as 0, the voltage of the piezoelectric driver of the first and second piezoelectric mirror frames is 0, and the focal length of the zoom lens 18 is f1. Before the experiment, the relationship between the voltage and the focal length of the zoom lens, the driving voltage and the yaw and pitch change angles of the piezoelectric mirror frame, and the driving voltage and the displacement distance of the electric displacement platform are calibrated in advance. In the subsequent control process, the computer can give the control voltage according to the calibration situation, so that the optical path can be adjusted accurately and automatically.

[0069] The present invention can adjust the cavity length of the disk laser resonant cavity in real time, and has a system that stabilizes the directivity of the light beam in the resonant cavity. In order to make the curvature change of the disk crystal within the full power working range within the stable range, a large number of experiments are required to fix the laser resonant cavity at a suitable cavity length position. The present invention weakens the tedious and repetitive experimental operations by adjusting the cavity length of the resonant cavity in real time. In conventional disk lasers, the curvature change of the disk crystal within the full power working range is within the stable range. When the power is further increased, the curvature change range of the disk laser crystal exceeds the stable range, and the properties of the laser resonant cavity deteriorate. The present invention compensates for the influence of the change of the curvature radius of the disk crystal by adjusting the cavity length of the resonant cavity in real time. The interference optical path outside the cavity is used to stabilize the directivity of the light beam in the cavity in a real-time closed loop, so as to overcome the influence of the thermal lens effect and the hot air wedge effect of the disk crystal.

[0070] Finally, it should be noted that: each embodiment in this specification is described by way of example, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the 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.

[0071] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 of the present application.

Claims

1. A cavity-stabilized disk laser with dynamically adjustable cavity length, characterized in that ,include: A laser optical path, comprising an end mirror, a first reflecting mirror, a disk laser crystal and a plurality of reflecting mirrors arranged in sequence along the optical path direction, wherein the end mirror is connected to a first piezoelectrically controlled mirror frame and is arranged on an electric displacement platform, the first reflecting mirror is connected to a second piezoelectrically controlled mirror frame, the yaw and pitch angles of the end mirror are adjusted by the first piezoelectrically controlled mirror frame, the displacement of the end mirror is adjusted by the electric displacement platform, and the yaw and pitch angles of the first reflecting mirror are adjusted by the second piezoelectrically controlled mirror frame; The calibration optical path is used to calibrate the light beam directivity at the disk laser crystal, the end mirror and the first reflector. When the disk laser crystal is working, the curvature changes, resulting in a change in the radius of the laser spot in the cavity at the disk. The radius of the laser spot at the disk laser crystal is changed by adjusting the electric displacement platform to translate the position of the end mirror. The adjustment will cause the light beam directivity of the laser optical path to change. The first piezoelectric control mirror frame and the second piezoelectric control mirror frame are assisted in adjusting the light beam directivity of the laser optical path.

2. The cavity-stabilized disk laser with dynamically adjustable cavity length according to claim 1, characterized in that , The calibration optical path includes: an initial optical path, a reference optical path and a detection optical path; Among them, the initial optical path includes the laser emitted from the first laser light source passing through the spectroscope and the laser optical path and then entering the detector; the reference optical path includes the laser emitted from the second laser light source passing through the spectroscope and then entering the detector; the detection optical path includes the laser emitted from the second laser light source passing through the spectroscope and the laser optical path and then entering the detector.

3. The cavity-stabilized disk laser with dynamically adjustable cavity length according to claim 2, characterized in that , The path of the detection light path from the beam splitter to the detector overlaps with the initial light path, and the initial light path, the reference light path and the detection light path coincide at the center of the light spot of the detector.

4. The cavity-stabilized disk laser with dynamically adjustable cavity length according to claim 3, characterized in that , the calibration optical path includes: The zoom lens is used to adjust the size of the light spot of the initial light path and the detection light path on the detector by adjusting the focal length of the zoom lens.

5. The cavity-stabilized disk laser with dynamically adjustable cavity length according to claim 2, characterized in that , The wavelength of the laser emitted by the first laser light source, the wavelength of the laser emitted by the second laser light source, the wavelength of the laser output by the laser optical path and the wavelength of the pump light used by the laser are different from each other.

6. The cavity-stabilized disk laser with dynamically adjustable cavity length according to claim 2, characterized in that , also includes: A piezoelectric controller is electrically connected to the first piezoelectric-controlled mirror frame, the electric displacement platform and the second piezoelectric-controlled mirror frame to synchronously or asynchronously control the displacement and / or yaw and pitch angles of the first piezoelectric-controlled mirror frame, the electric displacement platform and the second piezoelectric-controlled mirror frame.

7. The cavity-stabilized disk laser with dynamically adjustable cavity length according to claim 6, characterized in that , also includes: A central control unit is connected to the piezoelectric controller and the detector, and is configured to adjust the control instructions of the piezoelectric controller according to the light spot conditions output by the detector.

8. A method for controlling a laser according to any one of claims 2 to 6, characterized in that , During the operation of the laser, the pitch and tilt angles of the end mirror are regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the pitch and tilt angles of the first reflector are regulated by the second piezoelectric control mirror frame, so that the initial optical path, the reference optical path, and the detection optical path coincide at the center of the light spot of the detector; When the size of the detection spot of the detection light path on the detector changes, adjusting the focal length of the zoom lens to determine the direction and size of the curvature change of the disk laser crystal; Based on the direction and magnitude of the curvature change of the disk laser crystal, the end mirror displacement and the pitch and roll angles are again regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the pitch and roll angles of the first reflector are regulated by the second piezoelectric control mirror frame, so that the initial optical path, the reference optical path, and the detection optical path coincide at the center of the light spot of the detector.

9. The laser control method according to claim 8, characterized in that , also includes initialization calibration steps, including: Calibrate the relationship between the first driving voltage and the offset angle of the first piezoelectric control mirror frame; and / or; Calibrate the relationship between the second driving voltage and the offset angle of the second piezoelectric controlled mirror frame; and / or; Calibrate the relationship between the third driving voltage and the displacement distance of the electric displacement platform; and / or; The relationship between the fourth driving voltage and the focal length of the zoom lens is calibrated.

10. The laser control method according to claim 8, characterized in that The method of controlling the pitch and tilt angle of the end mirror and the displacement by the electric displacement platform and the first piezoelectric control mirror frame, and controlling the pitch and tilt angle of the first reflector by the second piezoelectric control mirror frame, comprises: The light spot condition output by the detector is displayed by a central control unit, and the control instructions of the piezoelectric controller are adjusted based on the light spot condition, so that the pitch and tilt angles and displacement of the end mirror are regulated by the electric displacement platform and the first piezoelectric control mirror frame, and the pitch and tilt angles of the first reflecting mirror are regulated by the second piezoelectric control mirror frame.

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