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

Abstract

The present application discloses an active early warning method and related device for mode-locked failure of a mode-locked oscillator, which can be used in the field of ultrafast laser mode locking. In this method, the mode-locked threshold currents corresponding to multiple working points when they reach the mode-locked threshold and the current mode-locked current corresponding to the current working point when they reach the mode-locked threshold are obtained; if the difference between the current mode-locked current corresponding to the current working point and the mode-locked threshold current corresponding to the current working point is greater than or equal to a first threshold, the current working point is switched from the first working point to the second working point; if the difference between the current mode-locked current corresponding to the second working point and the mode-locked threshold current corresponding to the second working point is greater than or equal to the first threshold, a maintenance early warning message is output; if the difference between the current mode-locked current corresponding to the second working point and the mode-locked threshold current is less than the first threshold, the first working point is marked as a damaged point. In this way, before mode-locked failure, the degradation of the mode-locked state can be detected in a timely manner and the cause of the degradation can be determined.

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 are attracting attention in numerous fields, including optical communications, super-resolution imaging and spectroscopy, biomedicine, and precision machining. In particular, laser processing allows for ultra-precise processing without affecting surrounding materials. However, laser processing applications require long-term, stable, and reliable operation 24 / 7. Technologies for generating stable, high-quality picosecond and even femtosecond laser pulses are also attracting increasing attention.

[0003] The semiconductor saturable absorber mirror (SESAM), a stable, reliable, and simple passive mode-locking device, has become the most common method for achieving picosecond or femtosecond ultrashort pulses in mode-locked oscillators. The causes of mode-locking failure (i.e., loss of lock) in SESAM-based mode-locked oscillators can be categorized into two main types: one is due to the SESAM itself. This is because the SESAM must withstand strong laser intensity within a small working area (i.e., the working point). After prolonged operation, this point can become damaged, leading to performance degradation and loss of lock, rendering the mode-locked oscillator inoperable. The other is due to other components within the mode-locked oscillator. These include decreased pump source (LD) power, changes in the spatial coupling system between the fiber focuser and the SESAM, which attenuates the laser reflected from the SESAM and coupled back to the gain fiber, and decreased performance within the mode-locked oscillator, resulting in increased intracavity losses. However, the existing method for solving the problem of mode-locking failure in SESAM mode-locked oscillators is to passively monitor changes in the mode-locking state and passively replace a new operating point after detecting loss of lock or actively replace the operating point after a period of operation. It is impossible to distinguish whether the loss of lock is caused by damage to the SESAM's own operating point or performance degradation of other components of the mode-locked oscillator. It is also impossible to determine whether the SESAM's own operating point has reached the end of 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 deterioration of the mode-locked state, and avoid the loss of lock phenomenon, 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 early warning method and related devices for mode-locked failure of a mode-locked oscillator, which can provide active early warning for the cause of mode-locked failure of a SESAM mode-locked oscillator.

[0006] The embodiments of this application disclose the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides an active early warning method for mode-locked failure of a mode-locked oscillator, which is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror. The method includes:

[0008] Obtaining 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;

[0009] If a difference between a current mode-locking current corresponding to the current operating point and a mode-locking threshold current corresponding to the current operating point is greater than or equal to a first threshold, switching the current operating point from the first operating point to the second operating point;

[0010] 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 a first threshold, outputting maintenance warning information;

[0011] If a difference between a current mode-locking current corresponding to the second operating point and a mode-locking threshold current corresponding to the second operating point is smaller than a first threshold, the first operating point is marked as a damaged point.

[0012] Optionally, the outputting maintenance warning information includes:

[0013] Switching the current working point from the second working point to the first working point;

[0014] Increase the current to keep the mode-locked oscillator operating;

[0015] If the difference between the increased current and the mode-locking threshold current corresponding to the first operating point exceeds a second threshold, a maintenance warning message is output; the second threshold is greater than the first threshold.

[0016] Optionally, before switching the current operating point from the first operating point to the second operating point, the method further includes:

[0017] Get the switching order of multiple working points;

[0018] Switching the current working point from the first working point to the second working point includes:

[0019] Based on a switching sequence of a plurality of working points, the current working point is switched from a first working point to a second working point; the second working point is located next in sequence to the first working point.

[0020] Optionally, marking the first working point as a damaged point includes:

[0021] In the switching sequence of the plurality of working points, the first working point is deleted.

[0022] Optionally, after obtaining the mode-locking threshold currents corresponding to when the plurality of operating points reach the mode-locking state, and the current mode-locking current corresponding to when the current operating point reaches the mode-locking threshold, the method further includes:

[0023] 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 time of the current operating point is greater than or equal to the target time, the current operating point is switched from the first operating point to the second operating point.

[0024] In a second aspect, an embodiment of the present application provides an active early warning device for mode-locked oscillator mode-locked failure, 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;

[0025] The acquisition module is used to acquire the mode-locking threshold currents corresponding to when multiple working points of the semiconductor saturable absorber mirror reach the mode-locking state, and the current mode-locking current corresponding to when the current working point reaches the mode-locking threshold;

[0026] The switching module is configured to switch the current operating point from the first operating point to the second operating point when a difference between a current mode-locking current corresponding to the current operating point and a mode-locking threshold current corresponding to the current operating point is greater than or equal to a first threshold;

[0027] The early warning module is configured to output maintenance early warning information when a difference between a current mode-locking current corresponding to the second operating point and a mode-locking threshold current corresponding to the second operating point is greater than or equal to a first threshold;

[0028] The marking module is configured to mark the first operating point as a damaged point when a difference between a current mode-locking current corresponding to the second operating point and a mode-locking threshold current corresponding to the second operating point is less than a first threshold.

[0029] Optionally, the early warning module includes: a switching unit and an early warning unit;

[0030] The switching unit is configured to switch the current operating point from the second operating point to the first operating point;

[0031] 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-locked threshold current corresponding to the first operating point exceeds a second threshold, a maintenance early warning message is output; the second threshold is greater than the first threshold.

[0032] In a third aspect, an embodiment of the present application provides a laser system, comprising: a seed master control, a power supply system, a motor system, and a mode-locked oscillator based on a semiconductor saturable absorber mirror; the semiconductor saturable absorber mirror has a plurality of pre-set operating points;

[0033] 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 the motion mechanism of the motor system is implanted in a semiconductor saturable absorber mirror, wherein the semiconductor saturable absorber mirror is the mode-locked device of the mode-locked oscillator;

[0034] The seed master controls the motor system to move or rotate according to a target position; controls the power supply system to apply current to a diode pump source in the mode-locked oscillator, wherein the diode pump source provides pump light to the mode-locked oscillator in response to the current, and the 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, thereby generating picosecond or femtosecond ultrashort laser pulses;

[0035] The seed master is used to monitor the mode-locked state of the mode-locked oscillator and control the current output of the power supply system; obtain the mode-locked threshold current corresponding to when multiple operating points stored in the seed master reach the mode-locked state, and obtain the current mode-locked current corresponding to when the current operating point reaches the mode-locked threshold;

[0036] When a difference between a current mode-locking current corresponding to the current operating point and a 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 the first operating point to the second operating point;

[0037] 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 controller outputs maintenance warning information;

[0038] When a difference between a current mode-locking current corresponding to the second working point and a mode-locking threshold current corresponding to the second working point is smaller than a first threshold, the seed master marks the first working point as a damaged point.

[0039] Optionally, the seed master includes an analog-to-digital conversion input port;

[0040] The seed master is specifically used to: monitor the power supply system and obtain the analog current signal corresponding to when the current working point reaches the locking mode threshold; convert the analog current signal into a digital signal through the analog-to-digital conversion input port to obtain the current locking mode current.

[0041] Optionally, the multiple working points are arranged in a ring or line.

[0042] Compared with the existing technology, this application has the following beneficial effects:

[0043] In the embodiments of the present application, on the one hand, before mode locking fails, degradation of the mode locking state can be promptly detected by comparing the current mode locking current with the mode locking threshold current, and the corresponding working point can be marked as a damaged point to avoid performance degradation of the mode locking oscillator during continued use, which would bring risks to laser applications based on this type of mode locking oscillator, such as batch defective products when an ultrafast laser light source is used for laser processing. 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 determined whether the degradation of the mode locking state is caused by damage to the working point of the SESAM itself or by other components of the mode locking oscillator outside the SESAM. This allows the cause of the degradation of the mode locking state of the mode locking oscillator to be identified, and the working point can be replaced in a targeted manner or system maintenance warning information can be actively output, providing a suitable active warning method to avoid unpredictable loss of lock. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0045] Figure 1 A structural diagram of a semiconductor saturable absorber mirror provided in an embodiment of the present application;

[0046] Figure 2 A schematic diagram of a mode-locked oscillator with an optical fiber structure provided in an embodiment of the present application;

[0047] Figure 3 A flow chart of an active early warning method for mode-locked failure of a mode-locked oscillator provided in an embodiment of the present application;

[0048] Figure 4 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;

[0049] Figure 5 A structural diagram of a laser system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0050] The active early warning method and related device for mode-locked oscillator mode-locked failure provided in the present application can be used in the field of laser mode-locked. The above is only an example and does not limit the application field of the active early warning method and related device for mode-locked oscillator mode-locked failure provided in the present application.

[0051] The terms "first", "second", "third" and "fourth" in the specification, claims and drawings of this application are used to distinguish different objects rather than to limit a specific order.

[0052] In the embodiments of this application, words such as "as an example" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described in the embodiments of this application as "as an example" or "for example" should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "as an example" or "for example" is intended to present the relevant concepts in a concrete manner.

[0053] The terms used in the implementation section of this application are only used to explain the specific embodiments of this application and are not intended to limit this application.

[0054] As mentioned above, with the increasing application of ultrashort pulse lasers, technologies that can generate stable and high-quality picosecond and even femtosecond pulse lasers are attracting more and more attention.

[0055] Saturable absorption mirrors (SAMs) are generally used to generate short laser pulses and are passively mode-locked devices. Due to their simple structure and easy installation, they are currently widely used to generate ultrashort pulses. Materials used for SAMs include dyes, absorbing crystals, and semiconductors. Semiconductor Saturable Absorber Mirrors (SESAMs) stand out from other materials due to their low cost, high damage threshold, and short output pulse width, making them the mainstream SAM material in the market.

[0056] SESAM consists of a saturable absorber (SA) and a reflector, such as Figure 1As shown in the figure, the saturable absorber (01) and the single crystal layer (02) of the reflector are both grown on a gallium arsenide (GaAs) substrate (03). SESAMs can be used in wide-spectrum laser cavities. As laser light oscillates within the cavity, it continuously passes through the SA. The SA's absorption coefficient for light decreases with increasing incident light intensity. When absorption reaches saturation, absorption ceases and pulses are emitted. This process can also be described as follows: in low-light conditions, the SESAM absorbs and accumulates energy; in strong light conditions, the SESAM's optical loss decreases, its transmittance increases, and it reaches a "saturated" state, instantly releasing the absorbed energy. Therefore, utilizing this saturated absorption characteristic of the SESAM, it is possible to Q-switched and mode-lock the laser, achieving ultrashort pulse output in the picosecond or even femtosecond range.

[0057] See also Figure 2 This figure is a schematic diagram of a fiber-structured mode-locked oscillator provided in 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 (WDM) 500, a coupled focuser (Fiber Focuser) 600, an isolator (Isolator, ISO) 700, and a semiconductor saturable absorber mirror (SESAM) 800.

[0058] Among them, LD is used to generate a laser light source and provide a pump source for the mode-locked oscillator; CFBG is used to control the spectrum of the mode-locked oscillator and also acts as a reflector at one end 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, used to absorb the pump light provided by the LD and convert the pump light into laser; the coupling focuser 600 is used to convert the fiber light into spatial output and focus it onto the SESAM; the ISO is used to protect the mode-locked oscillator, reduce the impact of the return light on the mode-locked oscillator, and output part of the light to the photodiode (PD) detector. The PD is used to convert the mode-locked laser pulse signal into an electrical signal so that the seed master can judge the laser mode-locking status in real time based on the electrical signal.

[0059] The reasons for SESAM mode-locking failure (i.e., loss of lock) can be divided into two main categories: one is the SESAM itself, that is, because the SESAM needs to withstand strong laser intensity in a small working area (i.e., the working point), the working point is easily damaged after long-term operation, resulting in failure of the entire laser system; the other is other components in the mode-locked oscillator besides the SESAM, such as the power drop of the pump source (LD) used in the mode-locked oscillator, the change in the angle of the spatial coupling system between the coupling focuser (fiber focuser) and the SESAM, which leads to the attenuation of the laser reflected and coupled back to the gain fiber by the SESAM, and the performance degradation of internal components leading to increased intracavity loss.

[0060] Currently, a new operating point is usually replaced passively after SESAM lock loss is detected. On the one hand, there is no early warning of potential problems, which brings risks to laser applications based on this type of mode-locked oscillator, such as batch-level defective products when ultrafast laser light sources are used for laser processing. On the other hand, it is impossible to distinguish whether the SESAM lock loss is caused by the SESAM itself or by external factors, and it is impossible to determine whether the SESAM's own operating point has reached its service life, making it difficult to perform targeted maintenance or replacement of the mode-locked oscillator.

[0061] In view of this, an embodiment of the present application provides an active early warning method for mode-locked 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-locked threshold currents corresponding to multiple operating points of the semiconductor saturable absorber mirror when they reach the mode-locked threshold, as well as the current mode-locked current corresponding to the current operating point when it reaches the mode-locked threshold, are obtained; then, if the difference between the current mode-locked current corresponding to the current operating point and the mode-locked threshold current corresponding to the current operating point is greater than or equal to a first threshold, the current operating point is switched from the first operating point to the second operating point; finally, if the difference between the current mode-locked current corresponding to the second operating point and the mode-locked threshold current corresponding to the second operating point is greater than or equal to the first threshold, a maintenance early warning message is output; if the difference between the current mode-locked current corresponding to the second operating point and the mode-locked threshold current corresponding to the second operating point is less than the first threshold, the first operating point is marked as a damaged point.

[0062] Therefore, on the one hand, before the mode-locking fails, the deterioration of the mode-locking state can be discovered in time by comparing the current mode-locking current with the mode-locking threshold current, and the corresponding working point can be marked as a damaged point to avoid the performance degradation of the mode-locked oscillator during continued use, which will bring risks to laser applications based on this type of mode-locked oscillator, such as batch defective products when ultrafast laser light sources are used for laser processing; 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 determined whether the deterioration of the mode-locking state is caused by damage to the SESAM's own working point or by system reasons outside the SESAM. The working point can be replaced in a targeted manner or system maintenance warning information can be actively output, providing a suitable active warning method to avoid unpredictable loss of lock.

[0063] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0064] See also Figure 3 , which is a flow chart of an active early warning method for mode-locked failure of a mode-locked oscillator provided in an embodiment of the present application. The method is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror, and the method includes:

[0065] S301: Obtaining mode-locking threshold currents corresponding to when multiple operating points of a semiconductor saturable absorber mirror reach a mode-locking state, and a current mode-locking current corresponding to when a current operating point reaches a mode-locking threshold.

[0066] Specifically, the seed master can determine the mode-locked state of the mode-locked oscillator through phase-locking. Before the laser system leaves the factory, it can scan the mode-locked threshold current of the diode pump source LD when each operating point of the SESAM reaches the mode-locked state, and store the corresponding relationship between the operating point and the mode-locked threshold current. During the power-on self-test of the mode-locked oscillator or during manual self-test, the mode-locked threshold current corresponding to multiple operating points reaching the mode-locked state can be obtained through current scanning.

[0067] For example, N working points (working point 1, working point 2, ..., working point N) are pre-set in SESAM. First, working point 1 is used as the current working point, the LD current is slowly increased, and the electrical signal obtained by the PD is used to determine whether the mode is stably locked. The current I1 when the stable mode-locking state is just reached is recorded as the mode-locking threshold current corresponding to working point 1; then, working points 2 to working point N are used as the current working points in turn, and the above steps are repeated. The current I2 when the stable mode-locking state is just reached is recorded as the mode-locking threshold current corresponding to working point 1. N They are respectively recorded as the mode-locking threshold currents corresponding to working point 2 to working point N, thereby obtaining the mode-locking threshold current corresponding to each working point when it reaches the mode-locking threshold.

[0068] 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 the system can be read to obtain the corresponding mode-locking threshold current when each operating point reaches the mode-locking threshold; on the other hand, the LD current is slowly increased to make the laser system reach the mode-locking state, and the current I is monitored when the stable mode-locking state is just reached. 1，k , recorded as the current mode-locking current corresponding to the current operating point.

[0069] 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, execute step S303; if not, execute step S301.

[0070] Specifically, the first threshold ΔI1 can be pre-set according to actual needs. Taking working point 1 as the current working point as an example, 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 less than the first threshold, that is, I 1，k -I1<ΔI1, it means that the current mode-locking state has not deteriorated and the current working point can continue to be used. At this time, step S301 is executed to monitor the mode-locking state in real time. 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, that is, I 1，k If -I1≥ΔI1, it indicates that the current mode-locking state is deteriorated. In this case, step S303 may be executed to further analyze the cause of the deterioration of the mode-locking state.

[0071] Optionally, in I 1，kIn the case of -I1<ΔI1, it is possible to further determine whether the usage time of the current working point is greater than or equal to the preset target time. If the usage time of the current working point exceeds the target time, the current working point can be switched from the first working point to the second working point. For example, if the target time is set to 1000 hours and the current working point is working point 1, then after monitoring that the usage time of working point 1 exceeds 1000 hours, the current working point can be switched from working point 1 to working point 2; after monitoring that the usage time of working point 2 also exceeds 1000 hours, the current working point can be switched from working point 2 to working point 3, until it is switched to working point N; after monitoring that the usage time of working point N also exceeds 1000 hours, the current working point can be switched from working point N to working point 1, thereby realizing the recycling of each working point in SESAM.

[0072] Therefore, by recycling the various working points in the SESAM, it is possible to avoid a single location being subjected to high-energy-density laser irradiation for a long time, thereby reducing the risk of material aging or damage at each working point and extending the overall service life of the SESAM.

[0073] S303: Switch the current working point from the first working point to the second working point.

[0074] 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 and adjusting the switching point with precision machinery.

[0075] Optionally, each working point in the SESAM has a pre-set switching order, and the laser system may first obtain the switching order of the multiple working points, and then switch the current working point from the first working point to the second working point based on the switching order of the multiple working points, wherein the second working point is located next to the first working point.

[0076] For example, the work points can be numbered sequentially based on their physical arrangement order, and the order of their numbers can be used as the switching order. For example, the work points arranged in a circular or linear pattern can be numbered sequentially as work point 1, work point 2, ..., work point N. The switching order of the work points can be determined by ascending or descending order of numbers. If the order of descending numbers is used as the switching order of the work points, if the first work point is work point 2, then the second work point is work point 3. If the order of descending numbers is used as the switching order of the work points, if the first work point is work point 2, then the second work point is work point 1.

[0077] S304: Determine whether 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. If so, execute step S305; if not, execute step S306.

[0078] 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 If -I2<ΔI1, it means 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 cause of the deterioration should be damage to the working point. In this case, step S306 is executed.

[0079] 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 mode-locked state of the second working point has also deteriorated. In this case, it can be assumed that the first working point is not damaged. The degradation of the mode-locked state may be caused by external factors such as LD power drop, angle change of the spatial coupling system between the fiber focuser and the SESAM, which causes attenuation of the laser reflected and coupled back to the gain fiber by the SESAM, and performance degradation of devices within the mode-locked oscillator, which causes increased intracavity loss. In this case, step S305 can be executed.

[0080] S305: Output maintenance warning information.

[0081] 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 factors external to the SESAM. In this case, a maintenance warning message can be output to prompt maintenance personnel to schedule time to maintain the laser system. They can check and repair the LD power, the spatial coupling system angle of the fiber focuser and SESAM, and the performance of the devices in the mode-locked oscillator, thereby improving the problem of deterioration of the mode-locking state.

[0082] As an example, in I 2，k In the case of -I2≥ΔI1, since the current working point is not damaged, the LD current can be increased at the current working point to increase the energy of the diode pump source, compensate for the deterioration of the mode-locked state caused by system reasons outside the SESAM, and make the mode-locked oscillator continue to work, and record I 1，k The occurrence time of -I1≥ΔI1 serves as a prompt message indicating that the locking state has begun to deteriorate. Maintenance personnel can flexibly arrange the time for laser system maintenance by viewing the prompt message.

[0083] If the difference between the increased current and the mode-locking threshold current I1 corresponding to the first operating point exceeds a preset second threshold ΔI2, it indicates that increasing the current is no longer sufficient to maintain stable operation of the laser system. In this case, a maintenance warning message can be output to prompt maintenance personnel to schedule maintenance on the laser system as soon as possible. The system should inspect and repair the LD power, the spatial coupling system angle of the Fiber Focuser and SESAM, and the performance of the components within the mode-locked oscillator, thereby improving the problem of deteriorating mode-locking conditions. The second threshold ΔI2 is greater than the first threshold ΔI1.

[0084] Therefore, the maintenance warning information is output only when the difference between the increased current and the locking threshold current corresponding to the first working point exceeds the second threshold, avoiding frequent system alarms when the locking state just begins to deteriorate. Instead, the maintenance warning information is output only when the degree of degradation is more serious and there is a real need for maintenance, thereby reducing the maintenance frequency and maintenance costs.

[0085] Optionally, in I 2，k When -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 from the second operating point back to the first operating point, and the first operating point can continue to be used to perform the mode locking operation.

[0086] S306: Mark the first working point as a damaged point.

[0087] As an example, the first working point can be deleted from the switching sequence of multiple working points to mark it as a damaged point. Specifically, although the first working point has not experienced mode locking failure, its mode locking state has deteriorated. Continued use may lead to a decline in laser light source performance, increasing the probability of batch-specific defective products. Before the first working point's mode locking fails, the first working point is marked as a damaged point and deleted from the switching sequence. This allows the first working point to be skipped during the recycling of various working points in the SESAM, and the working point with deteriorated mode locking state is no longer used, significantly reducing the risk of batch-specific defective products during laser processing.

[0088] Optionally, the laser system can also transmit the information about the damage of the first working point to the human-computer interaction system, so that relevant staff can timely grasp the status information of each working point in the SESAM.

[0089] 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.

[0090] Therefore, in the embodiment 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 resulting in batch defective products when used for laser processing; on the other hand, when the locking mode state of the first working point deteriorates, the locking mode state of the second working point is detected. By comparing the locking mode states of different working points, it can be determined whether the deterioration of the locking mode state is caused by damage to the working point of the SESAM itself, or by system reasons outside the SESAM. The working point can be replaced in a targeted manner or system maintenance warning information can be actively output, providing a suitable active warning method to avoid unpredictable loss of lock.

[0091] See also Figure 4 , this figure is a schematic diagram of an active early warning device for mode-locked failure of a mode-locked oscillator provided by an embodiment of the present application. The device is applied to a mode-locked oscillator based on a semiconductor saturable absorber mirror. The device includes: an acquisition module 401, a switching module 402, an early warning module 403, and a marking module 404;

[0092] An acquisition module 401 is configured to acquire mode-locking threshold currents corresponding to when multiple operating points of the semiconductor saturable absorber mirror reach a mode-locking state, and a current mode-locking current corresponding to when a current operating point reaches a mode-locking threshold;

[0093] a switching module 402 configured to switch the current operating point from the first operating point to the second operating point when a difference between a current mode-locking current corresponding to the current operating point and a mode-locking threshold current corresponding to the current operating point is greater than or equal to a first threshold;

[0094] An early warning module 403 is configured to output maintenance early warning information when a difference between a current mode-locking current corresponding to the second operating point and a mode-locking threshold current corresponding to the second operating point is greater than or equal to a first threshold;

[0095] The marking module 404 is configured to mark the first operating point as a damaged point if a difference between a current mode-locking current corresponding to the second operating point and a mode-locking threshold current corresponding to the second operating point is less than a first threshold.

[0096] Therefore, 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 deteriorates, the locking mode state of the second working point is detected. By comparing the locking mode states of different working points, it can be determined whether the deterioration of the locking mode state is caused by damage to the working point of SESAM itself, or by system reasons outside SESAM. The working point can be replaced in a targeted manner or system maintenance warning information can be actively output, providing a suitable active warning method to avoid unpredictable loss of lock.

[0097] Optionally, the early warning module 403 includes a switching unit and an early warning unit; wherein, 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 so that the mode-locked oscillator continues to operate; if the difference between the increased current and the mode-locked threshold current corresponding to the first operating point is a second threshold, a maintenance early warning message is output; the second threshold is greater than the first threshold.

[0098] Optionally, the marking module 404 is specifically configured to delete the first operating point in the switching sequence of the plurality of operating points when a difference between a current mode-locking current corresponding to the second operating point and a mode-locking threshold current corresponding to the second operating point is less than a first threshold.

[0099] In some embodiments, the acquisition 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 next to the first working point.

[0100] 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 locking current corresponding to the current working point and the locking threshold current corresponding to the current working point is less than the first threshold, and the usage time of the current working point is greater than or equal to the target time.

[0101] See also Figure 5 , this figure is a structural diagram of a laser system provided in an embodiment of the present application, the system including: 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, the semiconductor saturable absorber mirror has multiple pre-set working points.

[0102] The seed master controller 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 controller 10 , and the motion mechanism of the motor system 30 is implanted with a semiconductor saturable absorber mirror, which is the mode-locked device of the mode-locked oscillator 40 .

[0103] The seed master 10 controls the motor system 30 to move or rotate according to the target position; the control power supply system 20 applies current to the diode pump source LD in the mode-locked oscillator 40. The diode pump source LD provides pump light to 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.

[0104] Exemplarily, the seed controller 10 may include an FPGA (Field-Programmable Gate Array) control board.

[0105] The seed master control 10 can communicate with the laser master control or host computer through a serial port or other communication methods to receive control instructions; the seed master control 10 can also be 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 on the screen.

[0106] The seed master control 10 can indicate the working status of the laser system through the I / O output port and control the current of the power supply system 20 to start or shut down.

[0107] The seed master controller 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 the temperature setting value of the power supply system 20 .

[0108] The seed master controller 10 converts the analog signals of the operating current and operating temperature obtained by monitoring the power supply system 20 into digital signals through the analog-to-digital conversion input port (AD input), so as to monitor the current and temperature provided by the power supply system 20. After obtaining the analog current signal corresponding to when the current operating point reaches the locking mode threshold, the analog current signal can be converted into a digital signal to obtain the current locking mode current.

[0109] The seed master controller 10 monitors the mode-locked signal formed by the PD through the FPGA internal phase-locked loop (PLL). The PLL determines whether the mode-locked signal is stable. After the mode-locked signal is stable, the PLL can output a low-level lock signal.

[0110] The power supply system 20 may include a constant current source and a temperature controller, wherein the constant current source is used to control the current output to the LD to ensure that the LD operates within a 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.

[0111] The motor system 30 may include a stepper motor driver, a motor attenuator, and a stepper motor, and is used to control the movement of the mechanical structure of the SESAM to switch the operating point.

[0112] For example, other mechanical structures in the mode-locked oscillator 40 can be found in Figure 2 ; Multiple working points in the semiconductor saturable absorber mirror can be arranged in a ring to facilitate cyclic switching of the working points.

[0113] The seed master controller 10 is configured to monitor the mode-locked state of the mode-locked oscillator 40 and control the current output of the power supply system 20. The seed master controller 10 obtains the mode-locked threshold currents corresponding to when multiple operating points reach the mode-locked state, as well as the current mode-locked current corresponding to when the current operating point reaches the mode-locked threshold. The current mode-locked current can be obtained by monitoring the power supply system 20.

[0114] When the difference between the current locking current corresponding to the current working point and the 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.

[0115] 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 controller outputs maintenance warning information.

[0116] 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 smaller than the first threshold, the seed master marks the first working point as a damaged point.

[0117] Therefore, in the embodiment 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 deteriorates, the locking mode state of the second working point is detected. By comparing the locking mode states of different working points, it can be determined whether the deterioration of the locking mode state is caused by damage to the working point of the SESAM itself, or by system reasons outside the SESAM. The working point can be replaced in a targeted manner or system maintenance warning information can be actively output, providing a suitable active warning method to avoid unpredictable loss of lock.

[0118] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various 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 illustrative, wherein 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 can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art can understand and implement it without expending creative work.

[0119] The above is only a specific embodiment 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 fiber-structured mode-locked oscillator shown can also be a spatial optical path mode-locked oscillator, etc.; the SESAM can have a ring-shaped switching structure, a linear switching structure, a wavy switching structure, etc. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

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

2. The method according to claim 1, characterized in that Before switching the current working point from the first working point to the second working point, the method further includes: Get the switching order of multiple working points; Switching the current working point from the first working point to the second working point includes: Based on a switching sequence of a plurality of working points, the current working point is switched from a first working point to a second working point; the second working point is located next in sequence to the first working point.

3. The method according to claim 2, characterized in that The marking the first working point as a damaged point includes: In the switching sequence of the plurality of working points, the first working point is deleted.

4. The method according to claim 1, wherein After obtaining the mode-locking threshold currents corresponding to when multiple operating points of the semiconductor saturable absorber mirror reach a mode-locking 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 time of the current operating point is greater than or equal to the target time, the current operating point is switched from the first operating point to the second operating point.

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

6. A laser system, characterized in that: 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; the semiconductor saturable absorber mirror has a plurality of pre-set working points; 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 the motion mechanism of the motor system is implanted in a semiconductor saturable absorber mirror, wherein the semiconductor saturable absorber mirror is the mode-locked device of the mode-locked oscillator; The seed master controls the motor system to move or rotate according to a target position; controls the power supply system to apply current to a diode pump source in the mode-locked oscillator, wherein the diode pump source provides pump light to the mode-locked oscillator in response to the current, and the 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, thereby generating picosecond or femtosecond ultrashort laser pulses; The seed master is used to monitor the mode-locked state of the mode-locked oscillator and control the current output of the power supply system; obtain the mode-locked threshold current corresponding to when multiple operating points stored in the seed master reach the mode-locked state, and obtain the current mode-locked current corresponding to when the current operating point reaches the mode-locked threshold; When a difference between a current mode-locking current corresponding to the current operating point and a 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 the first operating point to the second operating point; When the difference between the current mode-locked current corresponding to the second operating point and the mode-locked threshold current corresponding to the second operating point is greater than or equal to a first threshold, the seed master switches the current operating point from the second operating point to the first operating point; increases the current to enable the mode-locked oscillator to continue operating; and outputs a maintenance warning message if the difference between the increased current and the mode-locked threshold current corresponding to the first operating point exceeds a second threshold; the second threshold is greater than the first threshold; When a difference between a current mode-locking current corresponding to the second working point and a mode-locking threshold current corresponding to the second working point is smaller than a first threshold, the seed master marks the first working point as a damaged point.

7. The system according to claim 6, characterized in that The seed master includes an analog-to-digital conversion input port; The seed master is specifically used to: monitor the power supply system and obtain the analog current signal corresponding to when the current working point reaches the locking mode threshold; convert the analog current signal into a digital signal through the analog-to-digital conversion input port to obtain the current locking mode current.

8. The system according to claim 6, wherein: The multiple working points are arranged in a ring or line shape.

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