A mode-locked laser and a position adjusting device and method for a saturable absorber thereof

Abstract

The application discloses a mode-locked laser and a position adjusting device and method of a saturable absorber of the mode-locked laser. The adjusting device comprises an absorber, a heat sink sheet, a driving device and a control device arranged in sequence along a laser transmission direction; the absorber is used for mode-locking the laser; the absorber is attached to one side surface of the heat sink sheet, the other side surface of the heat sink sheet is fixedly connected with an output end of the driving device, an input end of the driving device is electrically connected with the control device, the control device controls the driving device to drive the heat sink sheet to move based on a preset corresponding relationship, so as to drive the absorber to move, and the trajectory of a light spot formed by the laser on the absorber is a spiral line. The surface utilization rate and the point exchange efficiency of the saturable absorber of the mode-locked laser are improved, and the service life of the mode-locked laser is prolonged.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a mode-locked laser and a device and method for adjusting the position of its saturable absorber. Background Technology

[0002] Passive mode-locked lasers exhibit significant technological advantages and broad application prospects in high-precision fiber optic sensing technology, high-capacity high-speed wavelength division multiplexing fiber optic communication systems, and high-power lasers.

[0003] In a passively mode-locked laser, the absorber is a key component for establishing pulsed laser oscillations from optical noise. These absorbers are made of semiconductor materials, graphene, or micro / nanostructured materials. Under strong light irradiation, these materials are susceptible to photothermal damage or ionization damage caused by high peak power. Since damage to the surface of a saturable absorber is typically a very small point, the remaining large area is a usable normal region. To fully utilize each saturable absorber, the entire surface material can be fully utilized by changing the position of the laser's point of application.

[0004] Currently, the laser action point position is usually moved by rotating or translating the absorber, or by implanting a multi-channel optical switch in the laser resonant cavity to switch the absorber. The former generally scans a circular or straight point-switching trajectory on the surface of the absorber, while the latter requires more alignment positions and is difficult to arrange multiple optical fibers closely on the same absorber. Due to the limited number of trajectory points, it will result in low surface utilization and point-switching rate of the absorber, and the lifespan of the mode-locked laser will not be maximized. Summary of the Invention

[0005] This invention provides a mode-locked laser and a position adjustment device and method for its saturable absorber, in order to solve the problem of surface utilization of the saturable absorber in the mode-locked laser, thereby extending the service life of the mode-locked laser.

[0006] To achieve the above objectives, one embodiment of the present invention provides a position adjustment device for a saturable absorber of a mode-locked laser, comprising: an absorber, a heat sink, a driving device, and a control device arranged sequentially along the laser transmission direction; the absorber is used to mode-lock the laser; the absorber is attached to one side surface of the heat sink, the other side surface of the heat sink is fixedly connected to the output end of the driving device, the input end of the driving device is electrically connected to the control device, and the control device controls the driving device to drive the heat sink to move based on a preset correspondence, thereby driving the absorber to move, so that the trajectory left by the laser spot on the absorber is a spiral.

[0007] Optionally, the spiral can be an equidistant Archimedean spiral.

[0008] Optionally, the driving device includes a dual-motor drive assembly, which includes a first motor, a second motor, and a displacement stage. The surface of the displacement stage is fixedly connected to the other side surface of the heat sink. The first motor is used to drive the displacement stage to move along a first direction, and the second motor is used to drive the displacement stage to move along a second direction. The first direction and the second direction are perpendicular to each other.

[0009] Optionally, the driving device includes a translational-rotation assembly, which includes a third motor and a displacement stage, as well as a gear and a rack. The displacement stage is fixed on the gear, and the other side surface of the displacement stage is fixedly connected to the heat sink. The third motor is used to drive the gear to rotate, wherein the initial position of the laser spot on the absorber is offset from the center of the absorber.

[0010] Optionally, the driving device includes a translational-rotation assembly, which includes a third motor and a displacement stage, as well as a worm gear and a worm. The displacement stage is fixed on the worm gear, and the other side surface of the displacement stage is fixedly connected to the heat sink plate. The third motor is used to drive the worm gear or worm to rotate, wherein the initial position of the laser spot on the absorber is offset from the center of the absorber.

[0011] Optionally, the drive device also includes a planetary reducer drive assembly, which includes a fourth motor, a fifth motor, a gear, a rack, a sun gear, multiple planet gears, and a displacement stage. The inner surface of the gear is provided with a first meshing tooth that meshes with the meshing teeth of the planet gears. The meshing teeth of the sun gear mesh with the meshing teeth of the planet gears. The outer surface of the gear is provided with a second meshing tooth that meshes with the meshing teeth of the rack. The fourth motor is used to drive the sun gear to rotate, and the fifth motor is used to drive the rack to move. One side surface of the displacement stage is connected to each planet gear, and the other side surface of the displacement stage is fixedly connected to the heat sink.

[0012] Optionally, the drive device includes a planetary reducer drive assembly, which includes a fourth motor, a fifth motor, a gear, a worm gear, a sun gear, multiple planet gears, and a displacement stage. The inner surface of the gear is provided with a first meshing tooth that meshes with the meshing teeth of the planet gears. The meshing teeth of the sun gear mesh with the meshing teeth of the planet gears. The outer surface of the gear is provided with a second meshing tooth that meshes with the meshing teeth of the worm gear. The fourth motor is used to drive the sun gear to rotate, and the fifth motor is used to drive the worm gear to move. One side surface of the displacement stage is connected to each planet gear, and the other side surface of the displacement stage is fixedly connected to the heat sink.

[0013] To achieve the above objective, a method for adjusting the position of a saturable absorber in a mode-locked laser is provided according to a second aspect of the present invention. The method is implemented based on the position adjustment device for a saturable absorber in a mode-locked laser according to any embodiment of the present invention. The method includes the following steps: obtaining a preset correspondence between the position of the displacement stage driven by the driving device and the position of the laser spot; controlling the driving device to drive the heat sink sheet to move based on the preset correspondence, so as to drive the absorber to move, so that the trajectory left by the laser spot on the absorber is a spiral.

[0014] Optionally, obtaining the preset correspondence between the position of the driving displacement stage of the driving device and the position of the laser spot includes: obtaining the surface area of ​​the absorber and the diameter of the laser spot of the mode-locked laser; calculating the outermost diameter of the spiral based on the surface area and the diameter of the laser spot; calculating the number of spiral turns based on the diameter of the laser spot and the outermost diameter of the spiral; calculating the spiral arm distance based on the number of spiral turns; calculating the spiral function coefficient based on the spiral arm distance; calculating the total circumference of the spiral based on the spiral function coefficient and the number of spiral turns; calculating the number of laser spot action points based on the laser spot diameter and the total circumference of the spiral, and obtaining the position of each laser spot action point; and fitting the preset correspondence between the position of the driving displacement stage of the driving device and the position of each laser spot action point.

[0015] To achieve the above objectives, a third aspect of the present invention provides a mode-locked laser, including a position adjustment device for the saturable absorber of the mode-locked laser as proposed in any embodiment of the present invention.

[0016] According to embodiments of the present invention, a mode-locked laser and a method and apparatus for adjusting the position of its saturable absorber are provided. The adjustment apparatus includes: an absorber, a heat sink, a driving device, and a control device arranged sequentially along the laser transmission direction. The absorber is used to mode-lock the laser. The absorber is attached to one surface of the heat sink, and the other surface of the heat sink is fixedly connected to the output end of the driving device. The input end of the driving device is electrically connected to the control device. The control device controls the driving device to move the heat sink based on a preset correspondence, thereby driving the absorber to move, so that the trajectory left by the laser spot on the absorber is a spiral. This improves the surface utilization rate and spot-changing efficiency of the saturable absorber in the mode-locked laser and extends the service life of the mode-locked laser.

[0017] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a position adjustment device for a mode-locked laser saturable absorber according to an embodiment of the present invention;

[0020] Figure 2 This is a motion trajectory diagram of the switching of the point of action in a spiral provided according to an embodiment of the present invention;

[0021] Figure 3 It is a motion trajectory diagram of the switching of the point of action on the circular line in the existing technology;

[0022] Figure 4 This is a schematic diagram of a dual-motor drive assembly provided according to an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the position change of the absorber when the point of action A is switched to the point of action B in the dual-motor drive assembly, according to an embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram of a translation and rotation assembly provided according to an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of another translation and rotation component provided according to an embodiment of the present invention;

[0026] Figure 8 This is a schematic diagram of a planetary reducer drive assembly provided according to an embodiment of the present invention;

[0027] Figure 9 This is a schematic diagram of another planetary reducer drive assembly provided according to an embodiment of the present invention;

[0028] Figure 10 This is a flowchart of a method for adjusting the position of a saturable absorber in a mode-locked laser according to an embodiment of the present invention;

[0029] Figure 11 This is a flowchart of a method for adjusting the position of a saturable absorber in a mode-locked laser according to a specific embodiment of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] Figure 1 This is a schematic diagram of a position adjustment device for a mode-locked laser saturable absorber provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the position adjustment device for the saturable absorber of the mode-locked laser proposed in this embodiment includes: an absorber 2, a heat sink 3, a driving device 4, and a control device 5 arranged sequentially along the transmission direction of the laser 1. The absorber 2 is used to mode-lock the laser 1. The absorber 2 is attached to one side surface of the heat sink 3, and the other side surface of the heat sink 3 is fixedly connected to the output end 42 of the driving device 4. The input end 41 of the driving device 4 is electrically connected to the control device 5. The control device 5 controls the driving device 4 to drive the heat sink 3 to move based on a preset correspondence, thereby driving the absorber 2 to move, so that the trajectory left by the laser spot formed by the laser 1 on the absorber 2 is a spiral.

[0033] For example, laser 1 is output from a mode-locked laser and is a sequence of equally spaced laser pulses.

[0034] The absorber 2 is a key component for establishing pulsed laser oscillations amidst optical noise. The absorber 2 can be made of semiconductor materials, graphene, or micro / nanostructured materials. Under strong light irradiation, these materials are susceptible to photothermal damage or ionization by high peak power. For example, the absorber 2 can have a volume of 1.4 * 1.4 * 0.3 mm. 3A semiconductor saturable absorber mirror (SESAM) is used. SESAM is a nonlinear medium that can mode-lock the laser light emitted from a mode-locked laser. The absorption of laser light by the SESAM changes with the intensity of the light field. When the light field is weak, the SESAM absorbs light strongly; as the light intensity increases, the absorption weakens, reaching a certain value where absorption saturates and all light passes through. The SESAM can be attached to one side of the heat sink 3 to receive laser light 1, and the SESAM surface is perpendicular to the propagation direction of laser light 1. The diameter of the laser light spot on the SESAM surface is 12 μm. Because the surface is perpendicular to the propagation direction of laser light 1, the diameter of the laser light spot on the SESAM remains constant regardless of rotation or translation.

[0035] The heat sink 3 refers to a material whose temperature does not change with the amount of heat energy transferred to it. For example, a copper heat sink 3 can be selected, as it has high thermal conductivity and good heat dissipation. The side of the heat sink 3 closest to the laser emission direction is attached to the absorber 2, while the side away from the laser emission direction is fixedly connected to the output end 42 of the driving device 4. A fixed connection refers to a connection method where one component is fixed to another without any relative movement.

[0036] The drive unit 4 is used to drive various working mechanisms. For example, the drive unit 4 can be a motor to generate driving torque. The drive unit 4 has an input terminal 41 and an output terminal 42. The input terminal 41 of the drive unit 4 is electrically connected to the control unit 5, and the output terminal 42 is fixedly connected to the heat sink 3 on the side opposite to the laser emission direction 1. The electrical connection refers to connecting the circuits between the power supplies of each segment of the contact suspension to ensure the smooth flow of the circuit.

[0037] Control device 5 refers to a device capable of directly or indirectly receiving signals, making judgments as needed, and issuing action commands to drive device 4 and other equipment. For example, control device 5 can be a programmable logic controller (PLC) or a single-chip microcomputer (SCM); this embodiment does not impose specific limitations. Control device 5 controls drive device 4 to drive heat sink 3 to move based on a preset correspondence, wherein the preset correspondence refers to a pre-generated, mutually corresponding relationship.

[0038] It is understood that the control device 5 has a pre-stored preset correspondence. This preset correspondence is the relationship between the position of the absorber 2 driven by the drive device 4 and the point of action of the laser spot formed by the laser 1 on the absorber 2. The movement of the absorber 2 is controlled by this preset correspondence so that the laser spot forms a spiral trajectory on the absorber 2. For example, when the current laser spot is located at point A on the absorber 2, after a preset time (which can be set by the user, generally the lifespan of a point on the absorber 2), the laser spot needs to be moved to point B on the absorber 2. After another preset time, the laser spot needs to be moved to point C on the absorber 2, and so on, with points A, B, C... forming a spiral trajectory. Points A, B, C... can be ordered sequentially according to the spiral trajectory or randomly. To improve the efficiency of point changing, the absorber is moved along a spiral trajectory in this invention.

[0039] In one embodiment, the laser spot 1 can be moved, the absorber 2 can be moved, or both the laser spot 1 and the absorber 2 can be moved simultaneously. To ensure the reliability of the device, in this embodiment only the absorber 2 is moved. By pre-storing a preset correspondence in the control device 5, the drive device 4 is directly controlled to move the absorber 2, so that after the absorber 2 is used, the trajectory left by each laser spot on the absorber 2 is a spiral.

[0040] When the laser spot 1 moves from point A to point B, if point A is the starting point, it can start from the center point of the spiral, the end point of the spiral, or any other point on the spiral. The spiral can be counterclockwise or clockwise, and this invention does not make any specific limitation in this regard.

[0041] When the scattered random sorting is performed Figure 2 The diagram illustrates the trajectory of a point of action (A) transitioning to point of action (B) along a spiral. A Cartesian coordinate system is established with the spiral center as the origin. The coordinates of point A are (X1, Y1), and the coordinates of point B are (X2, Y2). When the point of action transitions from A to B, the straight-line distance that point A needs to move in the direction of the arrow is... Since the position of laser spot 1 remains unchanged, the control device 5 controls the drive device 4 to drive the absorber 2 to move a straight distance in the opposite direction of the arrow under the action of arc-shaped tangential force and radial force. This allows you to switch the point of application from A to B.

[0042] For example, Figure 3 This illustrates the motion trajectory of any point A on a circular line switching to point B in the prior art. Point A first moves clockwise along the inner circle of the circular line, and then moves sequentially to points A1, A2, ... An Point, then, point of action A n The laser beam moves from the inner circle to point B. Since the position of the laser spot 1 remains unchanged, the control device 5 controls the drive device 4 to drive the absorber 2 first, under the action of an arc-shaped tangential force, to move in the opposite direction to the trajectory of the point of application. Then, under the action of a radial force, the absorber 2 moves along the same path as the point of application A. n When the movement trajectory reverses, i.e., when the point of action switches from A to B, the absorber 2 needs to move twice in stages. (Reference) Figure 2 Compared to existing technologies, when the laser spot formed by laser 1 leaves a spiral trajectory on the absorber 2, the control device 5 controls the driving device 4 to drive the absorber 2 to move under the combined action of arc-shaped tangential force and radial force, thus improving the efficiency of point-switching. Furthermore, in existing technologies, the laser spot of 1 can only act on annular lines, and the positions in the intervals between annular lines cannot be utilized. In this embodiment of the invention, the laser spot of 1 acts on a spiral line. While satisfying the distance between adjacent action points, the spiral line can improve the surface utilization rate of the absorber 2 compared to annular lines.

[0043] It should be noted that the acquisition of the preset correspondence is described in the method embodiments below.

[0044] Therefore, the position adjustment device for the saturable absorber of the mode-locked laser proposed in the embodiment of the present invention arranges the absorber 2, the heat sink 3, the driving device 4 and the control device 5 in sequence along the transmission direction of the laser 1. The control device 5 controls the driving device 4 to drive the heat sink 3 to move based on a preset correspondence, so as to drive the absorber 2 to move. This makes the trajectory left by the light spot formed by the laser 1 on the absorber 2 a spiral line, which improves the surface utilization rate and spot switching efficiency of the absorber 2 of the mode-locked laser and extends the service life of the mode-locked laser.

[0045] Optionally, the spiral can be an equidistant Archimedean spiral.

[0046] An Archimedean spiral is the trajectory formed by a point moving away from a fixed point at a constant velocity while simultaneously rotating around that fixed point at a constant angular velocity. In other words, it's a trajectory formed by both uniform rotation and uniform linear motion. For example, an Archimedean spiral can be equidistant. When both the circumferential velocity of the uniform rotation and the linear velocity of the uniform linear motion are doubled, the shape of the Archimedean spiral remains unchanged. In this case, the Archimedean spiral is a constant-velocity spiral, and because it expands outwards at equal intervals in each rotation cycle, it can be called an equidistant Archimedean spiral.

[0047] This invention proposes a method of moving the laser application point along a spiral trajectory on the surface of a saturable absorber, achieving a high density of usable application point coordinates on the same saturable absorber. This maximizes the utilization of the saturable absorber material and extends the lifespan of the mode-locked laser. An equidistant Archimedean spiral is used as the trajectory for the mode-locked laser application point. An application point is reserved approximately every 50 μm of arc length along this trajectory, with the outermost ring having the most application points, decreasing in number towards the inner rings. This spiral trajectory is achieved through a combination of radial and tangential movement, typically implemented using a rotary motor and a reduction geared translational mechanism. The saturable absorber is installed at the moving point along this spiral trajectory, its plane always parallel to the spiral plane. The laser application point then moves along the spiral trajectory on the surface of the moving saturable absorber. The numerous usable application points densely distributed along the equidistant Archimedean spiral maximize the utilization of the limited area of ​​the saturable absorber surface material, thereby significantly increasing the lifespan of the mode-locked laser.

[0048] The following section details how mechanical mechanisms are implemented.

[0049] Figure 4 This is a schematic diagram of a dual-motor drive assembly provided in an embodiment of the present invention. The drive device 4 includes a dual-motor drive assembly 43, which includes a first motor 431, a second motor 432, and a displacement stage 433. The surface of the displacement stage 433 is fixedly connected to the other side surface of the heat sink 3. The first motor 431 is used to drive the displacement stage 433 to move along a first direction, and the second motor 432 is used to drive the displacement stage 433 to move along a second direction. The first direction and the second direction are perpendicular to each other.

[0050] The dual-motor drive assembly 43 is a drive device 4 that uses two motors as its core components. A motor is an electromagnetic device that converts or transmits electrical energy based on the law of electromagnetic induction. For example, refer to... Figure 1 and Figure 2 The first motor 431 and the second motor 432 can be stepper motors, which are electric motors that convert the electrical pulse signals generated by the laser 1 into corresponding angular or linear displacements. The displacement stage 433 is a device used to move the absorber 2. The first direction of movement is the direction in which the first motor 431 drives the displacement stage 433 to move along the longitudinal axis, that is, the displacement stage 433 moves along the Y-axis; the second direction of movement is the direction in which the second motor 432 drives the displacement stage 433 to move along the transverse axis, that is, the displacement stage 433 moves along the X-axis. The first direction and the second direction are perpendicular to each other, that is, the X-axis is perpendicular to the Y-axis.

[0051] For example, if Figure 4When the point of action A is switched to the point of action B, since the position of the laser spot 1 remains unchanged, the control device 5 needs to control the first motor 431 and the second motor 432 in the drive device 4. The two motors drive the displacement stage 433 to move along the horizontal and vertical axes, thereby driving the absorber 2 to move under the action of arc-shaped tangential force and radial force. The movement method can be referred to Figure 2 The positional change of absorber 2 is as follows Figure 5 As shown. Therefore, this embodiment of the invention enables dual motors to drive the displacement stage 433 to move along both the horizontal and vertical axes. In other words, the motors can indirectly drive the absorber 2 on the heat sink 3, which is fixedly connected to the displacement stage 433, to move in both directions, thereby making the trajectory of the laser spot 1 on the surface of the absorber 2 an equidistant Archimedean spiral. The dual motor displacement satisfies... This type of method has a simple structure and high accuracy.

[0052] Figure 6 This is a schematic diagram of the translation and rotation assembly 44 provided in an embodiment of the present invention. The driving device 4 includes the translation and rotation assembly 44, which includes a third motor and a displacement stage, as well as a gear 443 and a rack 444. The displacement stage is fixed on the gear 443, and the other side surface of the displacement stage is fixedly connected to the heat sink 3. The third motor is used to drive the gear 443 to rotate. The initial position of the light spot formed by the laser 1 on the absorber 2 is offset from the center of the absorber 2.

[0053] Among them, the translation and rotation assembly 44 is a drive device 4 that can realize the translation and rotation of the displacement stage. Gear 443 refers to a mechanical element with gears 443 continuously meshing on its rim to transmit motion and power. Rack 444 is a special gear with teeth distributed on a rack-shaped body; rack 444 can be a spur rack or a helical rack. For example, rack 444 can be a spur rack corresponding to the teeth in gear 443. For example, if... Figure 6 When the point of action A is switched to the point of action B, since the position of the laser spot 1 remains unchanged, the control device 5 needs to control the third motor in the drive device 4 to drive the gear 443 to rotate. This, in turn, causes the absorber 2 in the displacement stage fixed on the gear 443 to rotate due to the arc-shaped tangential force. In addition, the rotating gear 443 can move horizontally along the rack 444 due to the radial force. The absorber 2 moves under the combined action of the arc-shaped tangential force and the radial force. The position change of the absorber 2 is as follows: Figure 6 As shown.

[0054] It should be noted that if the initial position of the laser spot formed by laser 1 on the absorber 2 is the center of the absorber 2, then under the combined action of arc-shaped tangential force and radial force, the laser spot formed by laser 1 will always be a straight line on the absorber 2. Furthermore, the laser spots on this straight line are arranged on the surface of the absorber 2 with the initial point as the center and in a direction parallel to the rack 444. Therefore, it is necessary to deviate the initial position of the laser spot formed by laser 1 on the absorber 2 from the center of the absorber 2. For example, this deviation can be made during the initial installation of the position adjustment device for the mode-locked laser absorber. Thus, this embodiment of the invention achieves the use of a motor to drive the gear 443 to rotate under the combined action of arc-shaped tangential force and radial force, thereby making the trajectory of the laser spot on the surface of the absorber 2 an equidistant Archimedean spiral. This type of point-changing method enables equipment miniaturization, reduces the impact of vibration on point-changing accuracy, and improves point-changing efficiency.

[0055] Figure 7 This is a schematic diagram of another translational-rotation component 45 provided in an embodiment of the present invention. The driving device 4 includes a translational-rotation component 45, which includes a third motor and a displacement stage, as well as a worm gear 453 and a worm 454. The displacement stage is fixed on the worm gear 453, and the other side surface of the displacement stage is fixedly connected to the heat sink 3. The third motor is used to drive the worm gear 453 or the worm 454 to rotate. The initial position of the light spot formed by the laser 1 on the absorber 2 is offset from the center of the absorber 2.

[0056] The worm gear 453 and worm 454 are used to transmit motion and power between two intersecting shafts. The two parts mesh continuously during transmission, and the teeth in the worm gear 453 and worm 454 correspond to each other. When the worm gear 453 rotates, it can drive the worm 454 to rotate; similarly, when the worm 454 rotates, it can drive the worm gear 453 to rotate. For example, when the third motor drives the worm gear 453 to rotate, it can drive the absorber 2 in the displacement stage fixed on the worm gear 453 to rotate due to the action of an arcuate tangential force. In addition, the rotating worm gear 453 can move horizontally along the worm 454 due to the action of a radial force. Thus, this embodiment of the invention achieves the use of a single motor to drive the worm gear 453 or worm 454 to rotate. The worm gear 453 rotates under the combined action of arcuate tangential force and radial force, thereby making the trajectory of the laser spot 1 on the surface of the absorber 2 an equidistant Archimedean spiral. The specific spiral trajectory can be found in [reference needed]. Figure 6 This type of contact point replacement method enables equipment miniaturization, reduces the impact of vibration on contact point replacement accuracy, and improves contact point replacement efficiency.

[0057] Figure 8This is a schematic diagram of the planetary reducer drive assembly 46 provided in an embodiment of the present invention. The drive device 4 further includes the planetary reducer drive assembly 46, which includes a fourth motor, a fifth motor, a gear 463, a rack 464, a sun gear 465, multiple planet gears 466, and a displacement stage. The inner surface of the gear 463 is provided with a first meshing tooth 4631, which meshes with the meshing teeth of the planet gears 466. The meshing teeth of the sun gear 465 mesh with the meshing teeth of the planet gears 466. The outer surface of the gear 463 is provided with a second meshing tooth 4632, which meshes with the meshing teeth of the rack 464.

[0058] The planetary reducer drive assembly 46 is a power transmission mechanism. A gear 463 with fewer teeth on the drive shaft meshes with a larger gear 463 on the output shaft to achieve speed reduction. The sun gear 465 is the central gear in the planetary gear train, and the planet gears 466 are located around the outer ring of the sun gear 465. There can be multiple planet gears 466. For example, there can be three planet gears 466. When the sun gear 465 rotates, it drives the multiple outer planet gears 466 to revolve around the sun gear 465; when one of the outer planet gears 466 rotates, it drives the sun gear 465 and the remaining planet gears 466 to rotate.

[0059] The fourth motor is used to drive the sun gear 465 to rotate, and the fifth motor is used to drive the rack 464 to move. One side surface of the displacement stage is connected to each planet gear 466, and the other side surface of the displacement stage is fixedly connected to the heat sink 3.

[0060] This embodiment adds a planetary reducer to the gear and rack embodiment. For example, when the fourth motor operates, it drives the sun gear 465 to rotate, which in turn drives multiple planetary gears 466 around the sun gear 465 to revolve in the same direction as the sun gear 465. This causes the absorber 2 in the displacement platform connected to the planetary gears 466 to rotate due to the arc-shaped tangential force. Simultaneously, the fifth motor drives the rack 464 to move, allowing the gear 463 to move radially on the rack 464 with a speed reduction effect. In other words, while moving the absorber 2 via the gear and rack, the planetary gears 466 in the planetary reducer also cause the absorber 2 to rotate. This allows for precise adjustment of the absorber 2's position, further improving the surface utilization and switching efficiency of the absorber 2. This type of structure is small in size, has a large transmission range, low noise, and minimal impact on switching accuracy.

[0061] Figure 9This is a schematic diagram of another planetary reducer drive assembly 47 provided in an embodiment of the present invention. The drive device 4 further includes a planetary reducer drive assembly 47, which includes a fourth motor, a fifth motor, a worm gear 471, a worm 472, a sun gear, multiple planet gears, and a displacement stage. The inner surface of the worm gear 471 is provided with a first meshing tooth 4711, which meshes with the meshing teeth of the planet gears. The meshing teeth of the sun gear mesh with the meshing teeth of the planet gears. The outer surface of the worm gear 471 is provided with a second meshing tooth 4712, which meshes with the meshing teeth of the worm 472.

[0062] This embodiment replaces the gears and racks with worm gears and worms in the previous embodiment. The working principle is basically the same as the gear and rack embodiment. For example, the worm gear teeth mesh with the teeth in the worm 472, and the fifth motor can drive the worm 472 to rotate, thereby causing the worm gear 471 to move radially under the action of radial force. This type of structure is small in size, has a large transmission range, low noise, and minimal impact on the switching accuracy.

[0063] It should be noted that in the four implementation methods mentioned above, the tooth width of the gear rack, the diameter of the gear, the tooth width of the meshing teeth of the worm gear, the diameter of the worm gear, and the tooth width and diameter of planetary gears, sun gears, etc., can all be determined based on the actual situation such as the diameter of the laser spot, the size of the absorber, and the utilization rate of the absorber. The laser exiting the target port will strike the absorber (SESAM mirror) whose motion trajectory is an Archimedean spiral, thereby achieving the point-changing operation. The number of points of action can be completely determined by the number of spiral coils. Generally speaking, the number of points of action increases towards the outermost coil. Therefore, by controlling the number of trajectory coils within a reasonable range, the influence of the inner coils on the point-changing accuracy can be ignored, increasing reliability.

[0064] Figure 10 This is a flowchart of a method for adjusting the position of a mode-locked laser saturable absorber according to an embodiment of the present invention. This adjustment method can be implemented based on a position adjustment device for a mode-locked laser saturable absorber provided in any embodiment of the present invention. Specifically, as shown... Figure 10 and Figure 11 As shown, the method includes:

[0065] S101. Obtain the preset correspondence between the position of the drive displacement stage and the position of the laser spot.

[0066] S1011. Obtain the surface area of ​​the absorber and the laser spot diameter of the mode-locked laser.

[0067] For example, when the volume of the absorber is 1.4*1.4*0.3mm 3 At that time, its surface area was 1.4*1.4mm. 2 Furthermore, the diameter of the laser spot can be represented by w.

[0068] S1012. Calculate the outermost diameter of the spiral based on the surface area and the diameter of the laser spot.

[0069] In this context, a spiral refers to a curve that rotates around a fixed point or axis and continuously contracts or expands. The Archimedean spiral is a two-dimensional spiral. When a point P moves at a constant speed along a moving ray OP, and this ray rotates around point O at a constant angular velocity, the trajectory of point P is called the "Archimedean spiral." Its polar equation is r = bθ. Its standard polar equation is r = bθ + a, where b is the Archimedean spiral coefficient, in mm / °, representing the increase (or decrease) in polar diameter for every 1° of rotation; θ is the polar angle, in degrees, representing the total number of degrees the Archimedean spiral has rotated; and a is the polar diameter when θ is θ₁, in mm.

[0070] The outermost diameter of a solenoid refers to the distance between two points on the outermost edge of an equidistant Archimedean solenoid, from the center. Generally, in an equidistant Archimedean solenoid, the number of points of action of the absorber increases towards the outermost edge. Therefore, by controlling the number of turns within a reasonable range, the influence of the inner turns on the switching accuracy can be ignored, increasing reliability. Based on these conditions, for example, the outermost diameter of the solenoid can be selected as d.

[0071] S1013. Calculate the number of spiral turns based on the laser spot diameter and the outermost diameter of the spiral.

[0072] For example, the number of spiral turns can be n, then the formula for calculating the number of spiral turns n is:

[0073] S1014. Calculate the helical arm distance based on the number of helical turns.

[0074] The arm spacing refers to the distance *t* between each arm of a spiral. In the Archimedean spiral, the arm spacing is 2πb, meaning that the shape of the Archimedean spiral remains unchanged when both the circumferential velocity and the linear velocity are doubled. For example, the arm spacing *t* can be expressed as...

[0075] S1015. Calculate the helical function coefficients based on the helical arm distance.

[0076] For example, the helical coefficient b can be expressed as

[0077] S1016. Calculate the total circumference of the helix based on the helix function coefficient and the number of helix turns.

[0078] For example, the total circumference S of the helix can be expressed as Typically, when n is large enough, r = bθ and r i Substituting b into the total circumference S of the helix, we can calculate...

[0079] S1017. Calculate the number of laser spot impact points based on the laser spot diameter and the total circumference of the spiral, and obtain the position of each laser spot impact point.

[0080] Considering the influence of laser spot size on the damage at the point of impact, the distance between adjacent points of impact is kept at approximately 50 μm. For example, the distance h between adjacent points can be 50 μm, and the number of points of impact can be c, which can then be expressed as... The position (x, y) of the point of application can be represented as:

[0081]

[0082] Substituting r = bθ, the position of the point of application (x, y) can be expressed as:

[0083]

[0084] S1018. Fit the preset correspondence between the position of the displacement stage driven by the driving device and the position of each laser spot action point.

[0085] S102. Based on the preset correspondence, the control drive device drives the heat sink sheet to move, thereby driving the absorber to move, so that the trajectory left by the laser spot on the absorber is a spiral.

[0086] For example, based on the preset correspondence between the position of the displacement stage driven by the driving device and the position of the laser spot, the control device can control the driving device to drive the heat sink to move, so that the absorber moves under the action of arc tangential force and radial force, so that the trajectory left by the laser spot on the absorber is a spiral.

[0087] For example, the surface area of ​​the absorber is 1.4*1.4mm. 2 Furthermore, the laser spot diameter w is 12μm, the outermost spiral diameter d is 1.2mm, and the number of spiral turns n can be freely set within the maximum range. When the number of spiral turns n is set to 4 turns, the arm distance t is calculated to be 0.15mm, the spiral coefficient b is b = 0.0239mm, and the total spiral circumference S is 7566.8μm. Since the distance between adjacent action points is kept at 50μm, the number of action points c can be obtained as 151. It can be seen that a large number of action points can be obtained with only a few turns, enabling 151 point changes for a single SESAM, thus improving the service life of the SESAM.

[0088] The adjustment device proposed in this invention eliminates the complex multi-channel switching collimation optical path, simplifies the structural design, overcomes the problem of a single trajectory at the scanning circumferential application point, and eliminates the complex switching procedure. The Archimedean spiral trajectory can achieve unidirectional movement under the action of the mechanical structure, which not only improves surface utilization and thus enhances the efficiency of the saturable absorber, but also improves the efficiency of point switching. Because the trajectory at the application point has a tendency to move, it reduces the impact on laser mode-locking stability during non-giant transition points, greatly improving the lifespan of the absorber.

[0089] This embodiment discloses a method for adjusting the position of a saturable absorber in a mode-locked laser. A position adjustment device for the saturable absorber is used to establish a preset correspondence between the position of the displacement stage driven by the driving device and the position of the laser spot. Based on this preset correspondence, the driving device is controlled to move the heat sink, thereby moving the absorber. This results in the laser spot leaving a spiral trajectory on the absorber, improving the surface utilization and spot-changing efficiency of the saturable absorber in the mode-locked laser and extending the lifespan of the mode-locked laser.

[0090] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0091] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A position adjustment device for a saturable absorber of a mode-locked laser, characterized in that, include: An absorber, a heat sink, a driving device, and a control device are arranged sequentially along the laser transmission direction. The absorber is used to mode-lock the laser; The absorber is attached to one side of the heat sink, and the other side of the heat sink is fixedly connected to the output end of the driving device. The input end of the driving device is electrically connected to the control device. The control device controls the driving device to drive the heat sink to move based on a preset correspondence, so as to drive the absorber to move, and the trajectory left by the laser spot on the absorber is a spiral. The spiral is an equidistant Archimedean spiral.

2. The position adjustment device for the saturable absorber of a mode-locked laser according to claim 1, characterized in that, The driving device includes a dual-motor drive assembly, which includes a first motor, a second motor, and a displacement stage. The surface of the displacement stage is fixedly connected to the other side surface of the heat sink. The first motor is used to drive the displacement stage to move along a first direction, and the second motor is used to drive the displacement stage to move along a second direction. The first direction and the second direction are perpendicular to each other.

3. The position adjustment device for the saturable absorber of a mode-locked laser according to claim 1, characterized in that, The driving device includes a translational-rotation assembly, which includes a third motor and a displacement stage, as well as a gear and a rack. The displacement stage is fixed on the gear, and the other side surface of the displacement stage is fixedly connected to the heat sink. The third motor is used to drive the gear to rotate. The initial position of the laser spot on the absorber is offset from the center of the absorber.

4. The position adjustment device for the saturable absorber of a mode-locked laser according to claim 1, characterized in that, The driving device includes a translational-rotation assembly, which includes a third motor and a displacement stage, as well as a worm gear and a worm. The displacement stage is fixed on the worm gear, and the other side surface of the displacement stage is fixedly connected to the heat sink plate. The third motor is used to drive the worm gear or the worm to rotate. The initial position of the laser spot on the absorber is offset from the center of the absorber.

5. The position adjustment device for the saturable absorber of a mode-locked laser according to claim 1, characterized in that, The driving device includes a planetary reducer drive assembly, which includes a fourth motor, a fifth motor, a gear, a rack, a sun gear, multiple planetary gears, and a displacement platform. The inner surface of the gear is provided with a first meshing tooth, which meshes with the meshing teeth of the planetary gears. The meshing teeth of the sun gear mesh with the meshing teeth of the planetary gears. The outer surface of the gear is provided with a second meshing tooth, which meshes with the meshing teeth of the rack. The fourth motor is used to drive the sun gear to rotate, and the fifth motor is used to drive the rack to move. One side surface of the displacement platform is connected to each of the planetary gears, and the other side surface of the displacement platform is fixedly connected to the heat sink.

6. The position adjustment device for the saturable absorber of a mode-locked laser according to claim 1, characterized in that, The driving device includes a planetary reducer drive assembly, which includes a fourth motor, a fifth motor, a worm gear, a worm, a sun gear, multiple planetary gears, and a displacement platform. The inner surface of the worm gear is provided with a first meshing tooth, which meshes with the meshing teeth of the planetary gears. The meshing teeth of the sun gear mesh with the meshing teeth of the planetary gears. The outer surface of the worm gear is provided with a second meshing tooth, which meshes with the meshing teeth of the worm. The fourth motor drives the sun gear to rotate, and the fifth motor drives the worm to move. One side surface of the displacement platform is connected to each of the planetary gears, and the other side surface of the displacement platform is fixedly connected to the heat sink.

7. A method for adjusting the position of a saturable absorber in a mode-locked laser, characterized in that, Based on the position adjustment device as described in any one of claims 1-6, the method includes the following steps: Obtain a preset correspondence between the position of the displacement stage driven by the driving device and the position of the laser spot; Based on a preset correspondence, the driving device is controlled to drive the heat sink sheet to move, thereby driving the absorber to move, so that the trajectory left by the laser spot on the absorber is a spiral.

8. The method for adjusting the position of the saturable absorber in a mode-locked laser according to claim 7, characterized in that, Obtaining the preset correspondence between the position of the drive displacement stage and the position of the laser spot includes: Obtain the surface area of ​​the absorber and the laser spot diameter of the mode-locked laser; Calculate the outermost diameter of the helix based on the surface area and the laser spot diameter; The number of spiral turns is calculated based on the laser spot diameter and the outermost diameter of the spiral. Calculate the helical arm distance based on the number of helical turns; Calculate the helical function coefficients based on the helical arm spacing; Calculate the total circumference of the helix based on the helical function coefficients and the number of helical turns; The number of laser spot impact points is calculated based on the laser spot diameter and the total circumference of the spiral, and the position of each laser spot impact point is obtained. The preset correspondence between the position of the displacement stage driven by the driving device and the position of each laser spot point is fitted.

9. A mode-locked laser, characterized in that, Includes the position adjustment device for the saturable absorber of a mode-locked laser as described in any one of claims 1-6.

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