Kerr lens mode-locked self-starting-based solid laser

Abstract

The invention belongs to the field of solid-state lasers, and particularly discloses a Kerr lens mode-locked self-starting-based solid-state laser which comprises a laser generating unit used for generating laser and a mode-locked regulation and control unit arranged on a laser emergent light path. And the mode-locked regulation and control unit comprises a half-wave plate, a polaroid and a target reflector which are sequentially arranged along a preset light path, and is used for regulating and controlling the light intensity of the laser reflected back to the laser generation unit in a polarization state regulation mode and triggering the mode-locked state of the Kerr lens in a light disturbance mode. According to the invention, the Kerr lens mode locking state can be effectively triggered, a traditional mechanical disturbance mode is abandoned, all-optical active triggering is realized, and the operation convenience and long-term operation stability of the laser are greatly improved; in addition, a user can adjust the laser system to an optimal mode-locking trigger state, and the success rate and repeatability of mode-locking self-starting of the Kerr lens are remarkably improved.

Description

Technical Field

[0001] This application belongs to the field of solid-state laser technology, and more specifically, relates to a solid-state laser based on Kerr lens mode-locking self-starting. Background Technology

[0002] Ultrafast laser technology, as an important development direction in the field of lasers, plays a key role in scientific research, industry and medicine with its extremely high peak power and extremely narrow pulse width. The core of achieving its ultrashort pulse lies in mode-locking technology.

[0003] Currently, the mature generation of femtosecond-level pulses mainly relies on passive mode-locking mechanisms. This mechanism depends on the saturable absorption effect, which is a selective absorption characteristic for light intensity. That is, the loss is large for weak light and small for strong light (pulse peak), thus selecting and amplifying the pulse in competition. The specific technical implementation has mainly developed into two mainstream schemes: one is based on a physical saturable absorber, represented by a semiconductor saturable absorber mirror (SESAM). This scheme integrates a semiconductor absorption structure with a mirror. Although the technology is mature, its operating wavelength is limited by the semiconductor material itself, resulting in poor universality. More importantly, the SESAM itself is prone to irreversible optical damage during high-power operation, which limits the output power and increases the cost. The second is Kerr lens mode-locking (KLM) based on a virtual saturable absorber. It cleverly utilizes the Kerr nonlinear effect of the laser gain medium (such as Ti:sapphire crystal). When a high-intensity pulsed beam passes through, the refractive index of the medium exhibits a distribution that is high at the center and low at the edges, equivalent to an instantaneous focusing lens (i.e., a Kerr lens). Through careful design of the resonant cavity, this self-focusing effect is made to benefit only high-intensity mode-locked pulses (good mode matching, low loss) and detrimental to low-intensity continuous background light (mode mismatch, high loss), thus achieving pulse selection and compression similar to a saturable absorber. Due to this "virtual" characteristic, the KLM scheme does not require the fabrication of specific absorber materials and naturally possesses significant advantages such as a high damage threshold, large modulation depth, low cost, and the ability to generate shorter pulses.

[0004] However, existing Kerr lens mode-locking technology has several drawbacks: it is extremely sensitive to the adjustment precision of the resonant cavity, typically cannot be self-activated, and in practice relies heavily on mechanical disturbances applied by technicians to trigger the Kerr lens mode-locking state, making operation complex. Furthermore, long-term mechanical vibration can easily lead to optical path deviation and poor optical path stability, which severely hinders its large-scale application in industrial environments requiring high reliability.

[0005] Therefore, how to realize a solid-state laser based on Kerr lens mode-locking self-starting has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to realize a solid-state laser based on Kerr lens mode-locking self-starting, aiming to solve the problems of optical path offset and poor optical path stability caused by mechanical perturbation to start Kerr lens mode-locking in traditional Kerr lens mode-locking lasers.

[0007] To achieve the above objectives, in a first aspect, this application provides a solid-state laser based on Kerr lens mode-locking self-starting, comprising: A laser generating unit for generating laser light, and a mode-locking control unit arranged in the laser output optical path; The mode-locking control unit includes a half-wave plate, a polarizer, and a target reflector arranged sequentially along a preset optical path. It is used to control the intensity of the laser light reflected back to the laser generating unit by adjusting the polarization state, thereby triggering the mode-locking state of the Kerr lens in the form of optical perturbation.

[0008] Optionally, the half-wave plate is located at the laser emission port of the laser generating unit and is used to adjust the polarization state of the incident laser. The polarizer is located on the transmission optical path of the half-wave plate and is used to split the incident laser light after polarization state adjustment to obtain P-polarized light and S-polarized light. The target reflector is used to reflect incident P-polarized or S-polarized light back to the laser generating unit.

[0009] Optionally, when the target reflector is located on the reflected light path of the polarizer, the target reflector is used to reflect the incident S-polarized light back to the laser generating unit.

[0010] Optionally, when the target reflector is located in the transmission optical path of the polarizer, the target reflector is used to reflect the incident P-polarized light back to the laser generating unit.

[0011] Optionally, the polarizer is a thin-film polarizer.

[0012] Optionally, the target reflector is a plane reflector.

[0013] Optionally, the laser generating unit includes a laser pump source, a pump optical coupling system, and a resonant cavity arranged sequentially. The pump light coupling system is used to couple the pump light emitted from the laser pump source into the resonant cavity; The resonant cavity is used to repeatedly amplify the pump light in the laser gain medium through an internal preset optical path structure to generate laser light, and output the laser light to the mode-locking control unit.

[0014] Optionally, the resonant cavity includes a beam splitter, a laser gain medium, a first concave mirror, and a second concave mirror disposed on the reflection path of the beam splitter, a first planar mirror disposed on the reflection path of the first concave mirror, a second planar mirror disposed on the reflection path of the first planar mirror, and a laser output mirror disposed on the reflection path of the second planar mirror; the second concave mirror and the laser output mirror serve as two end mirrors of the resonant cavity. The beam splitter is used to transmit the incident pump light onto the laser gain medium to induce stimulated emission in the laser gain medium, and is also used to reflect the laser generated in the resonant cavity to the second concave reflector. The first concave reflector and the second concave reflector are used to change the cavity mode distribution of the resonant cavity so that the oscillating laser inside the cavity is focused on the laser gain medium. The first and second planar reflectors are used to fold the laser transmission optical path within the resonant cavity; The laser output mirror is used to output a portion of the laser light reflected from the second planar mirror from inside the cavity to outside the cavity.

[0015] Optionally, the resonant cavity further includes an aperture; the aperture is placed at the front end of the second concave mirror to improve the diffraction loss within the resonant cavity.

[0016] Optionally, the beam splitter is a dichroic mirror.

[0017] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: (1) This application provides a solid-state laser based on Kerr lens mode-locking self-starting. A controllable optical reflection path is formed by a mode-locking control unit introduced outside the resonant cavity of the laser generating unit. This allows the continuous light emitted from the laser generating unit to undergo polarization state adjustment and beam splitting after passing through a half-wave plate, a polarizer, and a target mirror. The corresponding polarized light output by beam splitting is accurately reflected back into the resonant cavity. This reflected light serves as a seed perturbation, which can effectively trigger the Kerr lens mode-locking state. This eliminates the traditional mechanical perturbation method and realizes active triggering of the entire optical system, greatly improving the ease of operation and long-term stability of the laser.

[0018] (2) This application provides a solid-state laser based on Kerr lens mode-locking self-starting. By rotating the half-wave plate in the mode-locking control unit, the intensity of the laser light reflected back into the cavity can be continuously adjusted, thereby enabling the user to adjust the laser system to the optimal mode-locking trigger state, which significantly improves the success rate and repeatability of Kerr lens mode-locking self-starting. Attached Figure Description

[0019] Figure 1 This is one of the structural schematic diagrams of a solid-state laser based on Kerr lens mode-locking self-starting provided in the embodiments of this application; Figure 2 This is the second schematic diagram of the solid-state laser based on Kerr lens mode-locking self-starting provided in the embodiments of this application; Figure 3 This is the third schematic diagram of the solid-state laser based on Kerr lens mode-locking self-starting provided in the embodiments of this application.

[0020] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is the laser generating unit; 11 is the laser pump source; 12 is the pump optical coupling system; 13 is the resonant cavity; 131 is the beam splitter; 132 is the laser gain medium; 133 is the first concave mirror; 134 is the second concave mirror; 135 is the first planar mirror; 136 is the second planar mirror; 137 is the laser output mirror; 138 is the aperture; 2 is the mode-locking control unit; 21 is the half-wave plate; 22 is the polarizer; 23 is the target mirror. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] The terms "first" and "second," etc., used in the specification and claims of this application are used to distinguish different objects, not to describe a specific order of objects. For example, "first plane mirror" and "second plane mirror," etc., are used to distinguish different plane mirrors, not to describe a specific order of plane mirrors.

[0023] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0024] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0025] To address the issue of mechanical disturbance, existing technologies have proposed a scheme using optical feedback for self-starting. This scheme uses a fixed external cavity mirror to feed a portion of the emitted laser back into the resonant cavity, replacing mechanical disturbance with optical disturbance. However, once the feedback optical path is determined, the intensity of the light fed back into the cavity is fixed and cannot be adjusted in real time or continuously. In practical applications, due to factors such as ambient temperature fluctuations and mirror thermal drift, the optimal triggering conditions for mode-locking can dynamically change. A fixed feedback light intensity cannot consistently match the optimal triggering threshold, resulting in uncertainty in the success rate and repeatability of mode-locking startup, thus limiting its application in industrial scenarios with higher reliability requirements.

[0026] Therefore, in order to overcome the various technical defects mentioned above in the prior art, this application proposes a solid-state laser based on Kerr lens mode-locking self-starting as described below.

[0027] The embodiments of this application are described below with reference to the accompanying drawings.

[0028] Figure 1 This is one of the structural schematic diagrams of a solid-state laser based on Kerr lens mode-locking self-starting provided in the embodiments of this application, such as... Figure 1 As shown, the laser includes: A laser generating unit 1 for generating laser light, and a mode-locking control unit 2 arranged in the laser output optical path; The mode-locking control unit 2 includes a half-wave plate 21, a polarizer 22 and a target reflector 23 arranged sequentially along a preset optical path. It is used to control the intensity of the laser reflected back to the laser generating unit 1 by adjusting the polarization state, and to trigger the mode-locking state of the Kerr lens in the form of optical perturbation.

[0029] Specifically, in the embodiments of this application, the solid-state laser based on Kerr lens mode-locking self-starting can include two main parts: an internal structure and an external structure. The internal structure is the laser generating unit 1 that generates laser light; the external structure is the mode-locking control unit 2 arranged on the laser output path of the laser generating unit.

[0030] In the embodiments of this application, an external structure of the mode-locking control unit 2 is introduced to form a controllable optical reflection path for applying a disturbance to initiate the mode-locking of the Kerr lens. Specifically, the mode-locking control unit 2 may include a half-wave plate 21, a polarizer 22, and a target reflector 23 arranged sequentially along a preset optical path. In a specific embodiment, the laser generated by the laser generating unit 1 is emitted into the mode-locking control unit 2. The polarization direction of the input laser is changed by the half-wave plate 21, and the polarizer 22 performs polarization selection, transmitting the target polarized light to the target reflector 23 so that the generated reflected light can be reflected back to the laser generating unit 1 along the original path. Thus, by rotating the half-wave plate to control the polarization state, the intensity of the light reflected back into the resonant cavity of the laser generating unit 1 can be continuously adjusted, triggering the mode-locking state of the Kerr lens in the form of optical disturbance.

[0031] Here, it's important to explain that the reason the reflected light returning to the cavity can effectively trigger the Kerr lens mode-locking state is due to the underlying physical mechanism. This mechanism involves introducing the necessary initial intensity fluctuations and phase modulation within the resonant cavity through controllable optical feedback, thereby initiating the nonlinear evolution process from continuous light to pulsed light. Specifically, before mode-locking, the solid-state laser operates in continuous light mode, and the optical field within the cavity is uniform in time and space. The polarized light injected from outside the cavity interferes with the existing continuous light, altering the temporal and spatial intensity distribution of the light within the cavity. This creates slightly higher intensity "peaks" on the uniform background light, which become the initial seeds for pulse formation. The laser gain medium exhibits a Kerr nonlinear effect, with its refractive index proportional to the light intensity. Therefore, when these intensity "peaks" pass through the laser gain medium, they exhibit a stronger self-focusing effect—the Kerr lens effect—due to their higher local intensity. These peaks are preferentially amplified in each round-trip oscillation, while the background light is suppressed. At the same time, the dispersion and nonlinear effects (self-phase modulation) of the medium work together to continuously compress the time-domain width of the pulse, eventually forming a stable femtosecond-level ultrashort pulse, thus realizing the mode-locked state of the Kerr lens.

[0032] It should also be noted that, on the one hand, the solid-state laser structure provided in this application can decouple the two stages of "mode-locking condition achievement" and "mode-locking state triggering". Here, in this application embodiment, it is necessary to first ensure that the design of the laser generation unit resonant cavity (such as concave mirrors, apertures, and other optical path structures) meets the Kerr lens mode-locking conditions, and then provide a trigger signal through external optical feedback. This decoupling design allows the laser to overcome its fatal defect of not being able to stably self-start while maintaining the advantages of high power and narrow pulse width of traditional KLM lasers.

[0033] On the other hand, unlike the existing technology that uses a fixed mirror for single-intensity light feedback, this application introduces a controllable optical feedback path based on polarization modulation. Specifically, this path consists of a half-wave plate, a polarizer, and a mirror in sequence. The key is that by rotating the half-wave plate, the intensity of the seed perturbation light fed back into the resonant cavity can be continuously and precisely adjusted, thereby achieving active and optimized control of the mode-locking triggering process.

[0034] The solid-state laser of this application embodiment forms a controllable optical reflection path through a mode-locking control unit introduced outside the resonant cavity of the laser generating unit. This allows the continuous light emitted from the laser generating unit to undergo polarization state adjustment and beam splitting after passing through a half-wave plate, a polarizer, and a target mirror. The corresponding polarized light output from the beam splitting is then accurately reflected back into the resonant cavity. This reflected light serves as a seed perturbation, which can effectively trigger the mode-locking state of the Kerr lens. This eliminates the traditional mechanical perturbation method and achieves fully optical active triggering, greatly improving the ease of operation and long-term operational stability of the laser.

[0035] The solid-state laser of this application embodiment can continuously adjust the intensity of the laser light reflected back into the cavity by rotating the half-wave plate in the mode-locking control unit, thereby enabling the user to adjust the laser system to the optimal mode-locking trigger state, which significantly improves the success rate and repeatability of Kerr lens mode-locking self-starting.

[0036] Based on the above embodiments, as an optional embodiment, the half-wave plate 21 is located at the laser emission port of the laser generating unit 1 and is used to adjust the polarization state of the incident laser. Polarizer 22 is located in the transmission light path of half-wave plate 21 and is used to split the incident laser after polarization state adjustment to obtain P-polarized light and S-polarized light. The target reflector 23 is used to reflect the incident P-polarized light or S-polarized light back to the laser generating unit 1.

[0037] Specifically, in the embodiments of this application, the external structure of the resonant cavity consists of a half-wave plate 21, a polarizer 22, and a target reflector 23. The half-wave plate 21 is located at the laser emission port of the laser generating unit 1 and is used to adjust the polarization state of the incident laser. Rotating the half-wave plate 21 changes the angle between its optical axis and the linearly polarized light emitted from the cavity, thereby changing the polarization direction of the linearly polarized light. When it passes through the polarizer 22, it is split into two components: S-polarized and P-polarized light. The proportion of these components is determined by the angle between the half-wave plate and the linearly polarized light emitted from the cavity. The target reflector 23 is arranged with its reflecting surface perpendicular to the incident light, allowing the incident P-polarized or S-polarized light to return along its original path. Specifically, the return light path first passes through the polarizer, then the half-wave plate, and finally through the output mirror of the laser generating unit 1 before returning to its resonant cavity for optical perturbation. Specifically, the polarizer 22 can be a thin-film polarizer or a polarizing beam splitter, etc.; the target reflector can be a plane reflector, a concave reflector, or other reflectors that can ensure that the incident light returns along its original path.

[0038] It should be noted that, in the embodiments of this application, the same disturbance effect can be achieved by selecting either S-polarized light or P-polarized light to return to the resonant cavity of the laser generating unit 1, and the specific method can be determined by the constructed optical path structure.

[0039] Based on the above embodiments, as an optional embodiment, the polarizer 22 is a thin-film polarizer.

[0040] In the embodiments of this application, a thin-film polarizer is selected as the beam splitting element, utilizing the orthogonality of polarization states to achieve optical path separation and controllable feedback. A thin-film polarizer is a polarization beam splitter based on optical interference thin films. Its design principle is that, for incident light at a specific wavelength and incident angle, it has extremely high transmittance (>95%) for P-polarized light (polarization direction parallel to the incident plane) and extremely high reflectance (>95%) for S-polarized light (polarization direction perpendicular to the incident plane).

[0041] The solid-state laser of this application uses a thin-film polarizer as a beam splitter in a controllable optical path based on polarization modulation. Its high transmittance and high reflectance can reduce the light energy loss of the laser reflected back to the laser generation unit. At the same time, its high polarization extinction ratio can accurately control the return light power and the laser output power, improve the stability of Kerr lens mode-locking, and enhance the laser output efficiency.

[0042] Based on the above embodiments, as an optional embodiment, the target reflector 23 is a plane reflector. In the embodiments of this application, by using a plane reflector to reflect the polarized light transmitted from the polarizer 22, the reflected light can return along its original path to the resonant cavity of the laser generating unit 1, ensuring a simple reflected light path structure and low device cost.

[0043] The solid-state laser of this application embodiment constructs a mode-locking control unit by introducing an optical path design of a half-wave plate, a polarizer, and a target mirror, forming an effective set of controllable optical feedback paths based on polarization control. By rotating the half-wave plate to change the polarization direction of the feedback light, and combined with the polarization selection characteristics of the thin-film polarizer, the light intensity in the feedback cavity can be continuously and accurately controlled, realizing active and continuous control of the feedback intensity, which greatly improves the success rate and repeatability of Kerr lens mode-locking self-starting.

[0044] Continue to refer to Figure 1 As shown, based on the above embodiments, as an optional embodiment, when the target reflector 23 is located on the reflected light path of the polarizer 22, the target reflector 23 is used to reflect the incident S-polarized light back to the laser generating unit 1.

[0045] Specifically, in the embodiments of this application, depending on the different settings of the optical path structure, different polarized light can be selected as optical disturbance signals to be reflected back to the laser generating unit 1. When the rotating half-wave plate 21 changes the polarization direction of the incident linearly polarized light, it is split into two components, S-polarized and P-polarized, after passing through the polarizer 22. When the target reflector 23 is located on the reflected light path of the polarizer 22, after the polarization state is adjusted by the aforementioned half-wave plate 21, the light is split by the polarizer 22. The P-polarized light is transmitted, while the S-polarized light is perpendicularly reflected to the optical reflector. The target reflector 23 can then reflect the incident S-polarized light back to the laser generating unit 1.

[0046] The solid-state laser of this application embodiment, by placing the target reflector in the reflected optical path of the polarizer, can select S-polarized light as an optical perturbation signal to trigger the mode-locking state of the Kerr lens, thereby improving the flexibility and reliability of the internal optical path structure of the mode-locking control unit.

[0047] Figure 2 This is the second schematic diagram of the solid-state laser based on Kerr lens mode-locking self-starting provided in the embodiments of this application, as shown below. Figure 2 As shown, based on the above embodiments, as an optional embodiment, when the target reflector 23 is located on the transmission optical path of the polarizer 22, the target reflector 23 is used to reflect the incident P-polarized light back to the laser generating unit 1.

[0048] Specifically, in the embodiments of this application, the target reflector 23 can also be placed in the transmission optical path of the polarizer 22. Thus, when the half-wave plate 21 is rotated to change the polarization direction of the incident ray-polarized light, it is split into two components, S-polarized and P-polarized, after passing through the polarizer 22. When the target reflector 23 is located in the transmission optical path of the polarizer 22, after the polarization state is adjusted by the half-wave plate 21, the light is split by the polarizer 22. The S-polarized light is reflected, while the P-polarized light is perpendicularly transmitted to the target reflector 23, which can then reflect the incident P-polarized light back into the laser generating unit 1.

[0049] The solid-state laser of this application embodiment, by placing the target reflector in the transmission optical path of the polarizer, can select P-polarized light as an optical perturbation signal to trigger the mode-locking state of the Kerr lens, thereby improving the flexibility and reliability of the internal optical path structure of the mode-locking control unit.

[0050] Figure 3 This is the third schematic diagram of the solid-state laser based on Kerr lens mode-locking self-starting provided in the embodiments of this application, as shown below. Figure 3 As shown, in the embodiments of this application, the laser generating unit 1 includes a laser pump source 11, a pump optical coupling system 12 and a resonant cavity 13 arranged sequentially. Pump light coupling system 12 is used to couple the pump light emitted from laser pump source 11 into resonant cavity 13; The resonant cavity 13 is used to repeatedly amplify the pump light in the laser gain medium through the internal preset optical path structure to generate laser light, and output the laser light to the mode-locked control unit 2.

[0051] Specifically, in the embodiments of this application, the laser generating unit 1 can be composed of a laser pump source 11, a pump light coupling system 12, and a resonant cavity 13 arranged sequentially. The laser pump source 11 can provide the energy required to generate population inversion in the laser gain medium in the resonant cavity 13; the pump light coupling system 12 can couple the pump light into the laser gain medium, so that the laser gain medium obtains the energy required to generate stimulated emission, and the stimulated emission light oscillates back and forth in the resonant cavity 13 to achieve optical amplification and output continuous light.

[0052] In a specific embodiment of this application, the pump light is coupled into the laser gain medium within the resonant cavity 13 via the pump light coupling system 12, achieving population inversion and generating stimulated emission. The stimulated emission light signal oscillates back and forth within the resonant cavity 13, achieving optical amplification and outputting continuous light. When the light intensity within the cavity increases to a certain level, a Kerr lens effect is generated on the laser gain medium within the resonant cavity 13, reaching the mode-locking condition. At this point, part of the emitted continuous light acts as a disturbance and is reflected back into the resonant cavity 13 by the target reflector 23 in the external mode-locking control unit 2, thereby achieving Kerr lens mode-locking. Simultaneously, by controlling the light polarization state through the mode-locking control unit 2 and rotating the external half-wave plate 21, the intensity of the reflected light back into the resonant cavity 13 can be controlled, further increasing the probability of Kerr lens mode-locking.

[0053] The solid-state laser of this application embodiment, through the introduction of a laser pump source, a pump optical coupling system, and a resonant cavity structure design, can effectively meet the conditions for Kerr lens mode-locking, enabling the laser to maintain the advantages of high power and narrow pulse width of KLM.

[0054] Continue to refer to Figure 3 As shown in the embodiment of this application, the resonant cavity 13 includes a beam splitter 131, a laser gain medium 132, a first concave reflector 133 arranged sequentially, a second concave reflector 134 disposed on the reflection optical path of the beam splitter, a first planar reflector 135 disposed on the reflection optical path of the first concave reflector 133, a second planar reflector 136 disposed on the reflection optical path of the first planar reflector 135, and a laser output mirror 137 disposed on the reflection optical path of the second planar reflector 136; the second concave reflector 134 and the laser output mirror 137 serve as two end mirrors of the resonant cavity 13. The beam splitter 131 is used to transmit the incident pump light onto the laser gain medium 132 so that the laser gain medium 132 generates stimulated emission, and is also used to reflect the laser generated in the resonant cavity 13 to the second concave reflector 134. The first concave mirror 133 and the second concave mirror 134 are used to change the cavity mode distribution of the resonant cavity 13 so that the oscillating laser in the cavity is focused on the laser gain medium 132. The first plane mirror 135 and the second plane mirror 136 are used to fold the laser transmission optical path within the resonant cavity 13; The laser output mirror 137 is used to output the portion of the laser reflected from the second planar mirror 136 from inside the cavity to outside the cavity.

[0055] Specifically, it can be understood that the cavity mode of a resonant cavity refers to a specific oscillation mode formed by the electromagnetic field within the cavity, and its characteristics are determined by the cavity shape, size, and operating frequency. The cavity mode distribution of a resonant cavity is mainly divided into transverse modes and longitudinal modes, corresponding to the spatial distribution and frequency characteristics of the light beam, respectively. Among them, the transverse mode describes the spatial distribution pattern of the light beam perpendicular to the propagation direction (cross-section), and the longitudinal mode describes the frequency distribution of the light beam along the propagation direction (axial direction).

[0056] In the embodiments of this application, the resonant cavity in the laser generating unit may specifically consist of a beam splitter 131, a laser gain medium 132, a first concave reflector 133 arranged sequentially, a second concave reflector 134 arranged on the reflection optical path of the beam splitter, a first planar reflector 135 arranged on the reflection optical path of the first concave reflector 133, a second planar reflector 136 arranged on the reflection optical path of the first planar reflector 135, and a laser output mirror 137 arranged on the reflection optical path of the second planar reflector 136.

[0057] Based on the above embodiments, as an optional embodiment, the beam splitter 131 is a dichroic mirror.

[0058] Specifically, in the embodiments of this application, the beam splitter 131 preferably employs a dichroic mirror. Through a multi-layer thin-film design, the dichroic mirror exhibits high reflectivity or transmittance for light of specific wavelengths, precisely separating the operating wavelength and auxiliary wavelengths (such as pump light) within the laser resonant cavity, thus preventing non-target wavelengths from interfering with the laser output. Simultaneously, by precisely controlling the reflection / transmission ratio, the dichroic mirror can also optimize the mode matching of the beam within the resonant cavity, further enhancing the monochromaticity and directionality of the laser output.

[0059] Furthermore, in the embodiments of this application, the beam splitter 131 is used to reflect the laser in the resonant cavity 13 and allows the pump light to pass through almost without loss; the laser gain medium 132 is used to generate stimulated emission and serves as the Kerr medium for generating Kerr lens mode-locking, and can specifically be a laser crystal.

[0060] Here, the first concave mirror 133 and the second concave mirror 134 can change the cavity mode distribution of the resonant cavity 13, so that the oscillating laser inside the cavity is focused on the laser gain medium 132; the first planar mirror 135 and the second planar mirror 136 can be used to fold the optical path of the resonant cavity and reduce the size of the laser; the laser output mirror 137 outputs part of the laser inside the resonant cavity 13 to the outside of the cavity, and together with the second concave mirror 134, it forms the two end mirrors of the resonant cavity.

[0061] In the embodiments of this application, during the oscillation of the laser, the laser generated by the laser gain medium 132 oscillates back and forth between the resonant cavity end mirrors composed of the second concave reflector 134 and the laser output mirror 137. The first concave reflector 133 and the second concave reflector 134 control the intracavity mode distribution, while the first planar reflector 135 and the second planar reflector 136 fold the optical path without altering the intracavity mode distribution. Part of the laser light is output outside the cavity through the laser output mirror 137, and the output laser power depends on the transmittance of the laser output mirror 137. The emitted laser light is reflected back into the cavity by the mode-locking control unit 2. When the intracavity light intensity increases to a certain level, a Kerr lens effect is generated on the laser gain medium, reaching the mode-locking condition. At this time, part of the emitted continuous light acts as a disturbance and is reflected back into the resonant cavity by the external reflector, achieving Kerr lens mode-locking. The mode-locked pulsed laser can finally be output through the mode-locking control unit 2.

[0062] The solid-state lasers in this application include, but are not limited to, bulk solid-state lasers and disk lasers. They are applicable to laser crystals of various shapes, including but not limited to disk laser crystals and bulk solid-state laser crystals, and can meet different application requirements. For example, bulk solid-state lasers are suitable for industrial needs of compact structure and miniaturization, while disk lasers are suitable for industrial needs of high power and high beam quality.

[0063] Continue to refer to Figure 3 As shown, as an optional embodiment, the resonant cavity 13 further includes an aperture 138; the aperture 138 is placed at the front end of the second concave mirror 134 to improve the diffraction loss in the resonant cavity 13.

[0064] Specifically, in the embodiments of this application, depending on the mode distribution within the resonant cavity, apertures of different sizes can be placed at different positions within the cavity to increase the diffraction loss within the cavity, thereby assisting in mode-locking of the Kerr lens. The placement position is not restricted.

[0065] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0066] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0067] The directional terms mentioned in the embodiments of this application, such as "top", "bottom", "inner", "outer", "left", "right", etc., are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0068] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0069] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A solid-state laser based on Kerr lens mode-locking self-starting, characterized in that, include: A laser generating unit for generating laser light, and a mode-locking control unit arranged in the laser output optical path; The mode-locking control unit includes a half-wave plate, a polarizer, and a target reflector arranged sequentially along a preset optical path. It is used to control the intensity of the laser light reflected back to the laser generating unit by adjusting the polarization state, thereby triggering the mode-locking state of the Kerr lens in the form of optical perturbation.

2. The solid-state laser according to claim 1, characterized in that, The half-wave plate is located at the laser emission port of the laser generating unit and is used to adjust the polarization state of the incident laser. The polarizer is located on the transmission optical path of the half-wave plate and is used to split the incident laser light after polarization state adjustment to obtain P-polarized light and S-polarized light. The target reflector is used to reflect incident P-polarized or S-polarized light back to the laser generating unit.

3. The solid-state laser according to claim 2, characterized in that, When the target reflector is located on the reflected light path of the polarizer, the target reflector is used to reflect the incident S-polarized light back to the laser generating unit.

4. The solid-state laser according to claim 2, characterized in that, When the target reflector is located in the transmission path of the polarizer, the target reflector is used to reflect the incident P-polarized light back to the laser generating unit.

5. The solid-state laser according to claim 1, characterized in that, The polarizer is a thin-film polarizer.

6. The solid-state laser according to claim 5, characterized in that, The target reflector is a plane reflector.

7. The solid-state laser according to any one of claims 1-6, characterized in that, The laser generating unit includes a laser pump source, a pump optical coupling system, and a resonant cavity arranged sequentially. The pump light coupling system is used to couple the pump light emitted from the laser pump source into the resonant cavity; The resonant cavity is used to repeatedly amplify the pump light in the laser gain medium through an internal preset optical path structure to generate laser light, and output the laser light to the mode-locking control unit.

8. The solid-state laser according to claim 7, characterized in that, The resonant cavity includes a beam splitter, a laser gain medium, a first concave mirror, and a second concave mirror disposed on the reflected optical path of the beam splitter, a first planar mirror disposed on the reflected optical path of the first concave mirror, a second planar mirror disposed on the reflected optical path of the first planar mirror, and a laser output mirror disposed on the reflected optical path of the second planar mirror; the second concave mirror and the laser output mirror serve as the two end mirrors of the resonant cavity; The beam splitter is used to transmit the incident pump light onto the laser gain medium to induce stimulated emission in the laser gain medium, and is also used to reflect the laser generated in the resonant cavity to the second concave reflector. The first concave reflector and the second concave reflector are used to change the cavity mode distribution of the resonant cavity so that the oscillating laser in the cavity is focused on the laser gain medium. The first and second planar reflectors are used to fold the laser transmission optical path within the resonant cavity; The laser output mirror is used to output a portion of the laser light reflected from the second planar mirror from inside the cavity to outside the cavity.

9. The solid-state laser according to claim 8, characterized in that, The beam splitter is a dichroic mirror.

10. The solid-state laser according to claim 8, characterized in that, The resonant cavity also includes an aperture; the aperture is placed at the front end of the second concave mirror to improve the diffraction loss in the resonant cavity.

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