Active early warning method for mode locking failure of mode-locked oscillator and related device

Abstract

The invention discloses an active early warning method for mode locking failure of a mode-locked oscillator and a related device, which can be used in the field of mode locking of an ultrafast laser, in the method, corresponding mode-locked threshold current when a plurality of working points reach a mode-locked threshold and corresponding current mode-locked current when a current working point reaches the mode-locked threshold are acquired; if the difference value between the current mode locking current corresponding to the current working point and the mode locking threshold current corresponding to the current working point is greater than or equal to a first threshold value, switching the current working point from the first working point to a second working point; if the difference value between the current mode locking current corresponding to the second working point and the mode locking threshold current corresponding to the second working point is greater than or equal to a first threshold value, outputting maintenance early warning information; and if the difference value between the current mode locking current corresponding to the second working point and the mode locking threshold current is smaller than a first threshold value, marking the first working point as a damaged point. Therefore, before the mode locking fails, the deterioration condition of the mode locking state can be found in time, and the deterioration reason can be judged.

Description

Technical Field

[0001] The present application relates to the technical field of ultrafast laser mode locking, and in particular to an active early warning method and related device for mode locking failure of a mode-locked oscillator. Background Art

[0002] Picosecond or femtosecond ultrashort pulse lasers have an ultrashort time scale (10 -12 ~10 -15 ) and extremely high peak power have attracted attention in many fields such as optical communications, super-resolution imaging and spectroscopy, biomedicine and precision machining. Especially in the field of laser processing, the processing will not affect the surrounding materials in the spatial range involved, thus achieving "ultra-fine" processing. However, in laser processing applications, the laser needs to work stably and reliably for a long time, 7*24 hours. How to generate stable and high-quality picosecond or even femtosecond pulse laser technology is also attracting more and more attention.

[0003] Semiconductor saturable absorber mirror (SESAM), as a stable, reliable and simple passive mode-locking device, has become the most commonly used method for mode-locked oscillators to obtain picosecond or femtosecond ultrashort pulses. The reasons for the failure of mode-locking (i.e., loss of lock) of SESAM mode-locked oscillators are mainly divided into two categories: one is the SESAM itself, that is, since SESAM needs to withstand strong laser intensity on a small working area (i.e., working point), the working point is damaged after long-term operation, and the performance is degraded after damage, resulting in loss of lock and the mode-locked oscillator cannot work normally; the other is other device reasons of the mode-locked oscillator, such as the power reduction of the pump source (LD) used in the mode-locked oscillator, the change in the angle of the spatial coupling system of the coupling focuser (Fiber Focuser) and SESAM, which leads to the attenuation of the laser reflected by SESAM and coupled back to the gain fiber, and the performance of the device in the mode-locked oscillator is degraded, resulting in an increase in the cavity loss. However, the existing method of solving the problem of mode-locking failure of SESAM mode-locked oscillators is to passively monitor changes in the mode-locking state, passively replace a new working point after detecting loss of lock, or actively replace the working point after working for a period of time. It is impossible to distinguish whether the loss of lock is caused by damage to the SESAM's own working point or performance degradation of other components of the mode-locked oscillator. It is also impossible to determine whether the SESAM's own working point has reached its service life, making it difficult to actively maintain or replace the mode-locked oscillator in a targeted manner.

[0004] Therefore, how to determine the cause of the loss of lock of the mode-locked oscillator and take corresponding treatment measures, actively predict the degradation of the mode-locked state, and avoid the loss of lock, has become a problem that needs to be solved to ensure the stable and reliable operation of the mode-locked oscillator. Summary of the invention

[0005] Based on the above problems, the present application provides an active warning method and related device for mode-locking failure of a mode-locked oscillator, which can actively warn of the reasons for mode-locking failure of a SESAM mode-locked oscillator.

[0006] The embodiments of the present application disclose the following technical solutions: In a first aspect, an embodiment of the present application provides an active warning method for mode-locking failure of a mode-locked oscillator, which is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror. The method includes: Obtain the mode-locking threshold current corresponding to when a plurality of operating points of the semiconductor saturable absorber mirror reach the mode-locking state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold; If the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is greater than or equal to a first threshold, then switch the current operating point from a first operating point to a second operating point; If the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is greater than or equal to the first threshold, then output a maintenance warning message; If the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is less than the first threshold, then mark the first operating point as a damaged point.

[0007] Optionally, the outputting the maintenance warning message includes: Switch the current operating point from the second operating point to the first operating point; Increase the current so that the mode-locked oscillator continues to operate; If the difference between the increased current and the mode-locking threshold current corresponding to the first operating point exceeds a second threshold, then output a maintenance warning message; the second threshold is greater than the first threshold.

[0008] Optionally, before switching the current operating point from the first operating point to the second operating point, the method further includes: Obtain the switching order of a plurality of operating points; The switching the current operating point from the first operating point to the second operating point includes: Based on the switching order of a plurality of operating points, switch the current operating point from the first operating point to the second operating point; the second operating point is in the next position of the first operating point.

[0009] Optionally, the marking the first operating point as a damaged point includes: Delete the first operating point in the switching order of a plurality of operating points.

[0010] Optionally, after obtaining the mode-locking threshold current corresponding to when multiple operating points reach the mode-locked state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold, the method further includes: If the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is less than a first threshold, and the usage duration of the current operating point is greater than or equal to a target duration, then switch the current operating point from a first operating point to a second operating point.

[0011] In a second aspect, an embodiment of the present application provides an active early warning device for mode-locking failure of a mode-locked oscillator, which is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror. The device includes: an acquisition module, a switching module, an early warning module, and a marking module; The acquisition module is used to acquire the mode-locking threshold current corresponding to when multiple operating points of the semiconductor saturable absorber mirror reach the mode-locked state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold; The switching module is used to switch the current operating point from a first operating point to a second operating point when the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is greater than or equal to the first threshold; The early warning module is used to output a maintenance early warning message when the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is greater than or equal to the first threshold; The marking module is used to mark the first operating point as a damaged point when the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is less than the first threshold.

[0012] Optionally, the early warning module includes: a switching unit and an early warning unit; The switching unit is used to switch the current operating point from the second operating point to the first operating point; The early warning unit is used to increase the current to enable the mode-locked oscillator to continue operating; if the difference between the increased current and the mode-locking threshold current corresponding to the first operating point exceeds a second threshold, then output a maintenance early warning message; the second threshold is greater than the first threshold.

[0013] In a third aspect, an embodiment of the present application provides a laser system, the system includes: a seed master control, a power supply system, a motor system, and a mode-locked oscillator based on a semiconductor saturable absorber mirror; there are multiple preset operating points on the semiconductor saturable absorber mirror; The seed master, the power supply system, and the mode-locked oscillator are electrically connected in sequence; the motor system is electrically connected to the seed master, and a moving mechanism of the motor system is implanted with a semiconductor saturable absorber mirror, where the semiconductor saturable absorber mirror is a mode-locking device of the mode-locked oscillator; The seed master controls the motor system to move or rotate to a target position; controls the power supply system to apply a current to a diode pump source in the mode-locked oscillator, and the diode pump source provides pump light for the mode-locked oscillator in response to the current. A gain medium in the mode-locked oscillator converts the absorbed pump light into laser light, so that the laser light interacts with the semiconductor saturable absorber mirror to achieve mode locking and generate picosecond or femtosecond ultrashort laser pulses; The seed master is configured to monitor the mode-locking state of the mode-locked oscillator and control the current output of the power supply system; obtain the mode-locking threshold current corresponding to when multiple operating points stored in itself reach the mode-locking state, and obtain the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold; When the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is greater than or equal to a first threshold, the seed master drives the motor system to switch the current operating point from a first operating point to a second operating point; When the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is greater than or equal to the first threshold, the seed master outputs a maintenance warning message; When the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is less than the first threshold, the seed master marks the first operating point as a damaged point.

[0014] Optionally, the seed master includes an analog-to-digital conversion input port; The seed master is specifically configured to: monitor the power supply system, and obtain an analog current signal corresponding to when the current operating point reaches the mode-locking threshold; convert the analog current signal into a digital signal through the analog-to-digital conversion input port to obtain the current mode-locking current.

[0015] Optionally, the multiple operating points are arranged in a ring or a line.

[0016] Compared with the prior art, the present application has the following beneficial effects: In the embodiments of the present application, on the one hand, before the mode locking fails, the deterioration of the mode locking state can be detected in time by comparing the current mode locking current with the mode locking threshold current, and the corresponding operating point is marked as a damaged point, so as to prevent the performance of the mode locking oscillator from degrading during continuous use and bringing risks to laser applications based on this type of mode locking oscillator. For example, when an ultrafast laser source is used for laser processing, batch unqualified products may occur. On the other hand, when the mode locking state of the first operating point deteriorates, the mode locking state of the second operating point is detected. By comparing the mode locking states of different operating points, it can be determined whether the deterioration of the mode locking state is caused by the damage of the SESAM's own operating point or other components of the mode locking oscillator outside the SESAM. The cause of the deterioration of the mode locking state of the mode locking oscillator can be discriminated, and the operating point can be replaced or a proactive warning message for system maintenance can be output actively, providing a suitable proactive warning method to avoid unpredictable unlocking phenomena. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 FIG. is a structural diagram of a semiconductor saturable absorber mirror provided by an embodiment of the present application; Figure 2 FIG. is a schematic diagram of a mode locking oscillator with an optical fiber structure provided by an embodiment of the present application; Figure 3 FIG. is a flowchart of a proactive warning method for mode locking failure of a mode locking oscillator provided by an embodiment of the present application; Figure 4 FIG. is a schematic diagram of a proactive warning device for mode locking failure of a mode locking oscillator provided by an embodiment of the present application; Figure 5 FIG. is a structural diagram of a laser system provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] A proactive warning method and related device for mode locking failure of a mode locking oscillator provided by the present application can be used in the field of laser mode locking. The above is only an example and does not limit the application field of a proactive warning method and related device for mode locking failure of a mode locking oscillator provided by the present application.

[0020] The terms "first", "second", "third", and "fourth", etc. in the description, claims, and drawings of the present application are used to distinguish different objects, rather than to limit a specific order.

[0021] In the embodiments of the present application, words such as "as an example" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "as an example" or "for example" in the embodiments of the present application should not be construed as being more preferred or more advantageous than other embodiments or design solutions. Rather, the use of words such as "as an example" or "for example" is intended to present related concepts in a specific manner.

[0022] The terms used in the embodiments section of the present application are only used to explain the specific embodiments of the present application and are not intended to limit the present application.

[0023] As mentioned above, with the increasingly widespread application of ultrashort pulse lasers, the technology capable of generating stable and high-quality picosecond and even femtosecond pulsed lasers has attracted more and more attention.

[0024] A saturable absorption mirror (SAM) is generally used to generate short-pulse lasers and is a passive mode-locking device. Due to its simple structure and convenient installation, it has been widely used in generating ultrashort pulses. The materials of the saturable absorption mirror mainly include dyes, absorption crystals, and semiconductors, etc. Among them, the semiconductor saturable absorber mirror (SESAM) has the characteristics of low cost, high damage threshold, and short output pulse width, and stands out in the competition with other materials and becomes the mainstream saturable absorption mirror in the market.

[0025] SESAM consists of a saturable absorber (SA) and a mirror, as Figure 1 shown. Among them, the saturable absorber 01 and the single crystal layer 02 of the mirror are both grown on the gallium arsenide GaAs substrate 03. SESAM can be used in a wide-spectrum laser cavity. When the laser oscillates in the cavity, it will always pass through the SA. The absorption coefficient of the SA for light decreases as the incident light intensity increases. When the absorption reaches saturation, it stops absorbing and emits a pulse. This process can also be described as follows: in the case of weak light, SESAM absorbs and accumulates energy; in the case of strong light, the optical loss of SESAM becomes smaller and the transmittance increases, reaching the "saturated" state, and the energy absorbed can be instantaneously released. Thus, by utilizing this saturable absorption characteristic of SESAM, Q-switching mode-locking of the laser can be achieved, and ultrashort pulse output in the picosecond or even femtosecond range can be realized.

[0026] See Figure 2, this figure is a schematic diagram of a mode-locked oscillator with an optical fiber structure provided by an embodiment of the present application. The mode-locked oscillator uses a SESAM to conveniently and stably achieve laser mode locking. The mode-locked oscillator includes: a diode pump source (Laser Diode, LD) 100, a beam splitter (Beam Splitter, BS) 200, a chirped fiber Bragg grating (Chirped Fiber Bragg Grating, CFBG) 300, a gain fiber 400, a wavelength division multiplexer (Wavelength Division Multiplexer, WDM) 500, a fiber focuser 600, an isolator (Isolator, ISO) 700, and a semiconductor saturable absorber mirror (SESAM) 800.

[0027] Among them, the LD is used to generate a laser light source and provide a pump source for the mode-locked oscillator; the CFBG is used to control the spectrum of the mode-locked oscillator and at the same time serves as one end mirror of the mode-locked oscillator, reflecting most of the light reaching here back and outputting a small part of the light to the ISO; the gain fiber 400 can be a 6 / 125-YSF fiber, which is used to absorb the pump light provided by the LD and convert the pump light into laser light; the fiber focuser 600 is used to convert the fiber light into spatial output and focus it on the SESAM; the ISO is used to protect the mode-locked oscillator, reduce the influence of the returned light on the mode-locked oscillator, and output part of the light to a photodiode (Photodiode, PD) probe. The PD is used to convert the mode-locked laser pulse signal into an electrical signal, so that the seed master can judge the mode-locking state of the laser in real time according to the electrical signal.

[0028] The reasons for the failure of SESAM mode locking (i.e., loss of lock) are mainly divided into two categories: one is the reason of the SESAM itself, that is, since the SESAM needs to withstand a strong laser intensity on a small working area (i.e., the working point), the working point is easily damaged after long-term operation, resulting in the failure of the entire laser system; the other is the reason of other devices in the mode-locked oscillator except the SESAM, such as the power reduction of the pump source (LD) used in the mode-locked oscillator, the change in the angle of the spatial coupling system of the fiber focuser (Fiber Focuser) and the SESAM resulting in the attenuation of the laser reflected and coupled back to the gain fiber by the SESAM, and the increase in the intracavity loss due to the degradation of the performance of the internal devices.

[0029] Currently, it is usually necessary to passively replace the working point after detecting the SESAM unlocking. On the one hand, it is impossible to give an early warning of potential problems, which brings risks to laser applications based on this type of mode-locked oscillator. For example, batch unqualified products may occur when an ultrafast laser source is used for laser processing. On the other hand, it is impossible to distinguish whether the SESAM unlocking is due to its own reasons or external reasons of the SESAM, and it is impossible to judge whether the working point of the SESAM itself has reached the service life, making it difficult to maintain or replace the mode-locked oscillator targeted.

[0030] In view of this, the embodiment of the present application provides an active warning method for mode-locking failure of a mode-locked oscillator, which is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror. In this method, first, the mode-locking threshold current corresponding to when multiple working points of the semiconductor saturable absorber mirror reach the mode-locking threshold, and the current mode-locking current corresponding to when the current working point reaches the mode-locking threshold are obtained; then, if the difference between the current mode-locking current corresponding to the current working point and the mode-locking threshold current corresponding to the current working point is greater than or equal to the first threshold, the current working point is switched from the first working point to the second working point; finally, if the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold, a maintenance warning message is output; if the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is less than the first threshold, the first working point is marked as a damaged point.

[0031] Thus, on the one hand, before the mode-locking failure, it is possible to timely detect the deterioration of the mode-locking state by comparing the current mode-locking current with the mode-locking threshold current, and mark the corresponding working point as a damaged point, so as to avoid the performance degradation of the mode-locked oscillator during continuous use, which brings risks to laser applications based on this type of mode-locked oscillator. For example, batch unqualified products may occur when an ultrafast laser source is used for laser processing. On the other hand, in the case of the deterioration of the mode-locking state of the first working point, the mode-locking state of the second working point is detected. By comparing the mode-locking states of different working points, it is possible to judge whether the deterioration of the mode-locking state is caused by the damage of the working point of the SESAM itself or the system reasons external to the SESAM, and it is possible to replace the working point targeted or actively output a system maintenance warning message, providing a suitable active warning method to avoid unpredictable unlocking phenomena.

[0032] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0033] See Figure 3 , which is a flowchart of an active early warning method for mode-locking failure of a mode-locked oscillator provided by an embodiment of the present application. This method is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror. The method includes: S301: Obtain the mode-locking threshold current corresponding to when multiple operating points of the semiconductor saturable absorber mirror reach the mode-locking state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold.

[0034] Specifically, the seed master can determine the mode-locking state of the mode-locked oscillator through a phase-locked manner. Before the laser system leaves the factory, the mode-locking threshold current of the diode pump source LD can be scanned when each operating point of the SESAM reaches the mode-locking state, and the corresponding relationship between the operating point and the mode-locking threshold current can be stored. When the mode-locked oscillator performs a power-on self-check or a manual self-check process, the mode-locking threshold current corresponding to when multiple operating points reach the mode-locking state can be obtained through a current scanning method.

[0035] For example, N operating points (operating point 1, operating point 2,..., operating point N) are preset in the SESAM. First, use operating point 1 as the current operating point, slowly increase the LD current, and determine whether stable mode-locking is achieved through the electrical signal obtained by the PD. Record the current I1 when just reaching the stable mode-locking state as the mode-locking threshold current corresponding to operating point 1; then, sequentially use operating points 2 to N as the current operating point, repeat the above steps, and record the currents I2 to I N respectively as the mode-locking threshold currents corresponding to operating points 2 to N, so as to obtain the mode-locking threshold currents corresponding to when each operating point reaches the mode-locking threshold.

[0036] During the operation of the laser system, on the one hand, the corresponding relationship between the operating point and the mode-locking threshold current stored in itself can be read to obtain the mode-locking threshold current corresponding to when each operating point reaches the mode-locking threshold; on the other hand, slowly increase the LD current to make the laser system reach the mode-locking state, and monitor the current I 1，k , which is recorded as the current mode-locking current corresponding to the current operating point.

[0037] S302: Determine whether the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is greater than or equal to a first threshold. If so, perform the steps of S303; if not, perform the steps of S301.

[0038] Specifically, the first threshold ΔI1 can be preset according to actual needs. Taking operating point 1 as the current operating point as an example, if the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is less than the first threshold, that is, I 1，k- If I1 < ΔI1, it indicates that the current mode-locking state has not deteriorated, and the current operating point can continue to be used. At this time, perform the steps of S301 to monitor the mode-locking state in real time; if the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is greater than or equal to the first threshold, that is, I 1，k - If I1 ≥ ΔI1, it indicates that the current mode-locking state has deteriorated. At this time, the steps of S303 can be executed to further analyze the reasons for the deterioration of the mode-locking state.

[0039] Optionally, when I 1，k - I1 < ΔI1, it can further be determined whether the usage duration of the current operating point is greater than or equal to a preset target duration. If the usage duration of the current operating point exceeds the target duration, the current operating point can be switched from the first operating point to the second operating point. For example, if the target duration is set to 1000 hours and the current operating point is operating point 1, then after monitoring that the usage duration of operating point 1 exceeds 1000 hours, the current operating point can be switched from operating point 1 to operating point 2; after monitoring that the usage duration of operating point 2 also exceeds 1000 hours, the current operating point can be switched from operating point 2 to operating point 3 until it is switched to operating point N; after monitoring that the usage duration of operating point N also exceeds 1000 hours, the current operating point can be switched from operating point N to operating point 1, thereby realizing the cyclic use of each operating point in the SESAM.

[0040] Thus, by cyclically using each operating point in the SESAM, the risk of material aging or damage at a single location due to long-term exposure to high-energy-density laser irradiation can be avoided, thereby reducing the risk of material aging or damage at each operating point and extending the overall service life of the SESAM.

[0041] S303: Switch the current operating point from the first operating point to the second operating point.

[0042] As an example, the current operating point can be switched from the first operating point to the second operating point by driving a stepper motor to adjust the point change with precision machinery.

[0043] Optionally, each operating point in the SESAM has a preset switching order. The laser system can first obtain the switching order of multiple operating points, and then based on the switching order of multiple operating points, switch the current operating point from the first operating point to the second operating point. Among them, the second operating point is in the next position after the first operating point.

[0044] For example, according to the physical arrangement order of multiple working points, each working point can be numbered in sequence, and the sorting of the numbers can be used as the switching order of the working points. For example, if multiple working points arranged in a ring or a line are numbered as working point 1, working point 2,..., working point N in sequence, the order of the numbers from small to large or from large to small can be used as the switching order of the working points. When the order of the numbers from small to large is used as the switching order of the working points, if the first working point is working point 2, then the second working point is working point 3; when the order of the numbers from large to small is used as the switching order of the working points, if the first working point is working point 2, then the second working point is working point 1.

[0045] S304: Determine whether the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold. If so, execute the steps of S305; if not, execute the steps of S306.

[0046] Specifically, taking working point 2 as the second working point as an example, if the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is less than the first threshold, that is, I 2，k -I2 < ΔI1, it indicates that the mode-locking state of the second working point has not deteriorated, and only the mode-locking state of the first working point has deteriorated. The reason for the deterioration should be that the working point is damaged. At this time, execute the steps of S306.

[0047] If the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold, that is, I 2，k -I2 ≥ ΔI1, it indicates that the mode-locking state of the second working point has also deteriorated. At this time, it can be considered that the first working point is not damaged, and the reason for the deterioration of the mode-locking state may be external reasons of SESAM such as a decrease in LD power, a change in the angle of the spatial coupling system of the Fiber Focuser and SESAM resulting in a decrease in the laser reflected by SESAM and coupled back to the gain fiber, and a decrease in the performance of the devices in the mode-locking oscillator resulting in an increase in the intracavity loss. The steps of S305 can be executed.

[0048] S305: Output a maintenance warning message.

[0049] Specifically, if the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold, that is, I 2，k- If I2 ≥ ΔI1, it indicates that the deterioration of the mode-locking state is caused by system reasons outside the SESAM. At this time, a maintenance warning message can be output to prompt the maintenance personnel to arrange time to maintain the laser system, check and repair the LD power, the angle of the Fiber Focuser and the spatial coupling system of the SESAM, and the performance of the devices inside the mode-locking oscillator, so as to improve the problem of the deterioration of the mode-locking state.

[0050] As an example, in the case of I 2，k - I2 ≥ ΔI1, since the current operating point is not damaged, the LD current can be increased at the current operating point to improve the energy of the diode pump source, compensate for the deterioration of the mode-locking state caused by system reasons outside the SESAM, enable the mode-locking oscillator to continue to operate, and record the occurrence time of I 1，k - I1 ≥ ΔI1 as a prompt message for the start of the deterioration of the mode-locking state. The maintenance personnel can flexibly arrange the time to maintain the laser system by viewing the prompt message.

[0051] If the difference between the increased current and the mode-locking threshold current I1 corresponding to the first operating point exceeds the preset second threshold ΔI2, it indicates that the stable operation of the laser system cannot be maintained for a long time by increasing the current. At this time, a maintenance warning message can be output to prompt the maintenance personnel to arrange time to maintain the laser system as soon as possible, check and repair the LD power, the angle of the Fiber Focuser and the spatial coupling system of the SESAM, and the performance of the devices inside the mode-locking oscillator, so as to improve the problem of the deterioration of the mode-locking state. Among them, the second threshold ΔI2 > the first threshold ΔI1.

[0052] Thus, when the difference between the increased current and the mode-locking threshold current corresponding to the first operating point exceeds the second threshold, the maintenance warning message is output, avoiding frequent alarms of the system when the mode-locking state just starts to deteriorate, but outputting the maintenance warning message when the deterioration degree is relatively serious and there is a real need for maintenance, thereby reducing the maintenance frequency and maintenance cost.

[0053] Optionally, in the case of I 2，k - I2 ≥ ΔI1, it can be determined that the first operating point is not damaged. Therefore, before increasing the LD current, the current operating point can be switched back from the second operating point to the first operating point, and the mode-locking operation can be continued using the first operating point.

[0054] S306: Mark the first operating point as a damaged point.

[0055] As an example, the first working point can be deleted in the switching sequence of multiple working points to mark the first working point as a damaged point. Specifically, although the first working point does not have the problem of mode locking failure, its mode locking state has deteriorated. If it continues to be used, the performance of the laser light source may be reduced, increasing the probability of batch defective products. Before the mode locking of the first working point fails, the first working point is marked as a damaged point and deleted in the switching sequence, so that in the process of recycling the various working points in SESAM, the first working point can be skipped, and the working point with deteriorated mode locking state is no longer used, thereby greatly reducing the risk of batch defective products when used for laser processing.

[0056] Optionally, the laser system can also transmit the information of the damage of the first working point to the human-computer interaction system, so that the relevant staff can timely grasp the status information of each working point in the SESAM.

[0057] After marking the first working point as a damaged point, the laser system will continue to work with the second working point as the current working point, so that the laser system maintains relatively good mode locking performance.

[0058] Therefore, in the embodiments of the present application, on the one hand, before the locking mode fails, the deterioration of the locking mode state can be discovered in time by comparing the current locking mode current with the locking mode threshold current, and the corresponding working point can be marked as a damaged point to avoid continued use leading to batch defective products during laser processing; on the other hand, when the locking mode state of the first working point is deteriorated, the locking mode state of the second working point is detected, and by comparing the locking mode states of different working points, it can be determined whether the locking mode state is deteriorated due to damage to the working point of SESAM itself, or due to system reasons outside SESAM, so that the working point can be replaced in a targeted manner or system maintenance warning information can be actively output, and a suitable active warning method can be provided to avoid unpredictable loss of lock.

[0059] See also Figure 4 , which is a schematic diagram of an active early warning device for mode-locked failure of a mode-locked oscillator provided in an embodiment of the present application, the device is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror, and the device includes: an acquisition module 401, a switching module 402, an early warning module 403 and a marking module 404; An acquisition module 401 is used to acquire a mode-locking threshold current corresponding to when multiple working points of the semiconductor saturable absorber mirror reach a mode-locking state, and a current mode-locking current corresponding to when the current working point reaches the mode-locking threshold; A switching module 402, configured to switch the current working point from the first working point to the second working point when the difference between the current mode-locking current corresponding to the current working point and the mode-locking threshold current corresponding to the current working point is greater than or equal to the first threshold; The warning module 403 is used to output a maintenance warning message when the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold; The marking module 404 is used to mark the first working point as a damaged point when the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is less than the first threshold.

[0060] Thus, on the one hand, before the mode-locking fails, by comparing the current mode-locking current with the mode-locking threshold current, the deterioration of the mode-locking state can be detected in time, and the corresponding working point can be marked as a damaged point to avoid batch unqualified products during laser processing due to continued use; on the other hand, when the mode-locking state of the first working point deteriorates, the mode-locking state of the second working point is detected. By comparing the mode-locking states of different working points, it can be judged whether the deterioration of the mode-locking state is caused by the damage of the working point of the SESAM itself or by the system reason outside the SESAM. It can replace the working point targeted or actively output a system maintenance warning message, provide a suitable active warning method, and avoid unpredictable unlocking phenomena.

[0061] Optionally, the warning module 403 includes a switching unit and a warning unit; wherein, the switching unit is used to switch the current working point from the second working point to the first working point; the warning unit is used to increase the current to make the mode-locking oscillator continue to work; if the difference between the increased current and the mode-locking threshold current corresponding to the first working point is the second threshold, a maintenance warning message is output; the second threshold is greater than the first threshold.

[0062] Optionally, the marking module 404 is specifically used to delete the first working point in the switching order of multiple working points when the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is less than the first threshold.

[0063] In some embodiments, the obtaining module 401 is further used to: obtain the switching order of multiple working points; the switching module 402 is specifically used to switch the current working point from the first working point to the second working point based on the switching order of multiple working points; the second working point is located in the next position of the first working point.

[0064] In some embodiments, the switching module 402 is further used to: switch the current working point from the first working point to the second working point when the difference between the current mode-locking current corresponding to the current working point and the mode-locking threshold current corresponding to the current working point is less than the first threshold, and the usage duration of the current working point is greater than or equal to the target duration.

[0065] See Figure 5, This figure is a structural diagram of a laser system provided by an embodiment of the present application. The system includes: a seed master 10, a power supply system 20, a motor system 30, and a mode-locked oscillator 40 based on a semiconductor saturable absorber mirror; wherein, a plurality of working points are preset on the semiconductor saturable absorber mirror.

[0066] The seed master 10, the power supply system 20, and the mode-locked oscillator 40 are electrically connected in sequence; the motor system 30 is electrically connected to the seed master 10, and the moving mechanism of the motor system 30 is implanted into the semiconductor saturable absorber mirror, and the semiconductor saturable absorber mirror is a mode-locking device of the mode-locked oscillator 40.

[0067] The seed master 10 controls the motor system 30 to move or rotate according to the target position; controls the power supply system 20 to apply current to the diode pump source LD in the mode-locked oscillator 40, and the diode pump source LD provides pump light for the mode-locked oscillator 40 in response to the current. The gain medium in the mode-locked oscillator 40 converts the absorbed pump light into laser light, so that the laser light interacts with the semiconductor saturable absorber mirror to achieve mode locking and generate picosecond or femtosecond ultrashort laser pulses.

[0068] Exemplarily, the seed master 10 may have an FPGA (Field-Programmable Gate Array) master board.

[0069] The seed master 10 can communicate with the laser master or the upper computer through a serial port or other communication methods to receive control instructions; the seed master 10 can also be communicatively connected to the screen through a serial port or other communication methods to display information such as the operating status and working parameters of the laser system through the screen.

[0070] The seed master 10 can indicate the working status of the laser system through the I / O output port and control the current start or stop of the power supply system 20.

[0071] The seed master 10 converts its own digital signal into an analog signal through a digital-to-analog conversion output port (DA output) to control the current setting value and temperature setting value of the power supply system 20.

[0072] The seed master 10 converts the analog signals of the working current and working temperature obtained by monitoring the power supply system 20 into digital signals through an analog-to-digital conversion input port (AD input), so as to facilitate the monitoring of the current and temperature provided by the power supply system 20. Thus, after obtaining the analog current signal corresponding to the mode-locking threshold when the current working point is reached, the analog current signal can be converted into a digital signal to obtain the current mode-locking current.

[0073] The seed master 10 monitors the mode-locking signal formed by the PD through the Phase-Locked Loop (PLL) inside the FPGA. The PLL determines whether the mode-locking signal is stable. After the mode-locking signal is stable, the PLL can output a low-level locking signal.

[0074] The power supply system 20 may include a constant current source and a temperature controller. Among them, the constant current source is used to control the current output to the LD to ensure that the LD operates within the set current range; the temperature controller is used to control the temperature of the LD to keep the temperature of the LD within the optimal operating temperature range.

[0075] The motor system 30 may include a stepper motor driver, a motor attenuator, and a stepper motor, which are used to control the mechanical structure of the SESAM to move and switch the working point.

[0076] Exemplarily, for other mechanical structures in the mode-locking oscillator 40, reference can be made to Figure 2 ; multiple working points in the semiconductor saturable absorber mirror can be arranged in a ring to facilitate the cyclic switching of the working points.

[0077] The seed master 10 is used to monitor the mode-locking state of the mode-locking oscillator 40 and control the current output of the power supply system 20; obtain the mode-locking threshold current corresponding to each of the multiple working points stored in itself when the mode-locking state is reached, and obtain the current mode-locking current corresponding to the current working point when the current working point reaches the mode-locking threshold. Among them, the current mode-locking current can be obtained by monitoring the power supply system 20.

[0078] When the difference between the current mode-locking current corresponding to the current working point and the mode-locking threshold current corresponding to the current working point is greater than or equal to the first threshold, the seed master drives the motor system to switch the current working point from the first working point to the second working point.

[0079] When the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold, the seed master outputs a maintenance warning message.

[0080] When the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is less than the first threshold, the seed master marks the first working point as a damaged point.

[0081] Therefore, in the embodiments of the present application, on the one hand, before the locking mode fails, the deterioration of the locking mode state can be discovered in time by comparing the current locking mode current with the locking mode threshold current, and the corresponding working point can be marked as a damaged point to avoid continued use leading to batch defective products during laser processing; on the other hand, when the locking mode state of the first working point is deteriorated, the locking mode state of the second working point is detected, and by comparing the locking mode states of different working points, it can be determined whether the locking mode state is deteriorated due to damage to the working point of SESAM itself, or due to system reasons outside SESAM, so that the working point can be replaced in a targeted manner or system maintenance warning information can be actively output, and a suitable active warning method can be provided to avoid unpredictable loss of lock.

[0082] It should be noted that each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments. The device and system embodiments described above are merely schematic, in which the units described as separate components may or may not be physically separated, and the components indicated as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0083] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. For example, the mode-locked oscillator may be as described in the present application. Figure 2 The mode-locked oscillator of the optical fiber structure shown can also be a mode-locked oscillator of a spatial optical path structure, etc.; the SESAM can be a ring-shaped switching structure, a linear switching structure, or a wavy switching structure, etc. Any changes or substitutions that can be easily thought of by a technician familiar with the technical field within the technical scope disclosed in this application should be included in the protection scope of this application. Therefore, the protection scope of this application should be based on the protection scope of the claims.

Claims

1. An active early warning method for mode-locking failure of a mode-locked oscillator, characterized in that, Applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror, the method includes: Obtaining the mode-locking threshold current corresponding to when multiple operating points of the semiconductor saturable absorber mirror reach the mode-locked state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold; If the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is greater than or equal to a first threshold, then switching the current operating point from a first operating point to a second operating point; If the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is greater than or equal to the first threshold, then outputting a maintenance warning message; If the difference between the current mode-locking current corresponding to the second operating point and the mode-locking threshold current corresponding to the second operating point is less than the first threshold, then marking the first operating point as a damaged point.

2. The method according to claim 1, wherein The outputting the maintenance warning message includes: Switching the current operating point from the second operating point to the first operating point; Increasing the current to enable the mode-locked oscillator to continue operating; If the difference between the increased current and the mode-locking threshold current corresponding to the first operating point exceeds a second threshold, then outputting a maintenance warning message; the second threshold is greater than the first threshold.

3. The method according to claim 1, wherein Before switching the current operating point from the first operating point to the second operating point, the method further includes: Obtaining the switching order of multiple operating points; The switching the current operating point from the first operating point to the second operating point includes: Based on the switching order of multiple operating points, switching the current operating point from the first operating point to the second operating point; the second operating point is in the next position after the first operating point.

4. The method according to claim 3, wherein The marking the first operating point as a damaged point includes: Deleting the first operating point in the switching order of multiple operating points.

5. The method according to claim 1, wherein After obtaining the mode-locking threshold current corresponding to when multiple operating points of the semiconductor saturable absorber mirror reach the mode-locked state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold, the method further includes: If the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is less than the first threshold, and the usage duration of the current operating point is greater than or equal to a target duration, then switching the current operating point from the first operating point to the second operating point.

6. An active early warning device for mode-locking failure of a mode-locked oscillator, characterized in that, Applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror, the device includes: an acquisition module, a switching module, a warning module, and a marking module; The acquisition module is configured to obtain the mode-locking threshold current corresponding to when multiple operating points of the semiconductor saturable absorber mirror reach the mode-locked state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold; The switching module is configured to switch the current operating point from a first operating point to a second operating point when the difference between the current mode-locking current corresponding to the current operating point and the mode-locking threshold current corresponding to the current operating point is greater than or equal to the first threshold; The warning module is used to output a maintenance warning message when the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold; The marking module is used to mark the first working point as a damaged point when the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is less than the first threshold.

7. The device according to claim 6, characterized in that, The warning module includes: a switching unit and a warning unit; The switching unit is used to switch the current working point from the second working point to the first working point; The warning unit is used to increase the current to enable the mode-locking oscillator to continue working; if the difference between the increased current and the mode-locking threshold current corresponding to the first working point exceeds the second threshold, output a maintenance warning message; the second threshold is greater than the first threshold.

8. A laser system, characterized in that, The system includes: a seed master control, a power supply system, a motor system, and a mode-locking oscillator based on a semiconductor saturable absorber mirror; a plurality of working points are preset on the semiconductor saturable absorber mirror; The seed master control, the power supply system, and the mode-locking oscillator are electrically connected in sequence; the motor system is electrically connected to the seed master control, and the moving mechanism of the motor system is implanted into the semiconductor saturable absorber mirror, where the semiconductor saturable absorber mirror is the mode-locking device of the mode-locking oscillator; The seed master control controls the motor system to move or rotate according to the target position; controls the power supply system to apply current to the diode pump source in the mode-locking oscillator, and the diode pump source provides pump light for the mode-locking oscillator in response to the current, and the gain medium in the mode-locking oscillator converts the absorbed pump light into laser light, so that the laser light interacts with the semiconductor saturable absorber mirror to achieve mode-locking and generate picosecond or femtosecond ultrashort laser pulses; The seed master control is used to monitor the mode-locking state of the mode-locking oscillator and control the current output of the power supply system; obtain the mode-locking threshold currents corresponding to when multiple working points stored in itself reach the mode-locking state, and obtain the current mode-locking current corresponding to when the current working point reaches the mode-locking threshold; When the difference between the current mode-locking current corresponding to the current working point and the mode-locking threshold current corresponding to the current working point is greater than or equal to the first threshold, the seed master control drives the motor system to switch the current working point from the first working point to the second working point; When the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is greater than or equal to the first threshold, the seed master control outputs a maintenance warning message; When the difference between the current mode-locking current corresponding to the second working point and the mode-locking threshold current corresponding to the second working point is less than the first threshold, the seed master control marks the first working point as a damaged point.

9. The system according to claim 8, characterized in that, The seed master control includes an analog-to-digital conversion input port; The seed master is specifically used for: monitoring the power supply system to obtain an analog current signal corresponding to when the current working point reaches the mode-locking threshold; converting the analog current signal into a digital signal through an analog-to-digital conversion input port to obtain the current mode-locking current.

10. The system according to claim 8, characterized in that, The multiple working points are arranged in a ring or a line.

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