Fiber stretcher and frequency-tunable all-fiber ultrashort pulse laser

Abstract

The present invention relates to an ultrashort pulse laser, and more specifically to an optical fiber stretcher and a frequency-adjustable all-fiber ultrashort pulse laser, in order to solve the problems of existing femtosecond pulse lasers in adjusting the repetition frequency, such as complex structure, large volume, poor integration, and small adjustment frequency range. The technical solution adopted by the present invention is: an optical fiber stretcher, comprising a piezoelectric ceramic plate; a fixed plate and a force-bearing plate symmetrically arranged along the y-axis; a first amplifier plate and a second amplifier plate symmetrically arranged along the x-axis, and the first amplifier plate and the second amplifier plate are T-shaped structures; a first connecting plate arranged between the fixed plate and the first amplifier plate, a second connecting plate arranged between the fixed plate and the second amplifier plate, a third connecting plate arranged between the force-bearing plate and the second amplifier plate, and a fourth connecting plate arranged between the force-bearing plate and the first amplifier plate. The present invention also provides a frequency-adjustable all-fiber ultrashort pulse laser.

Description

Technical Field

[0001] The present invention relates to an ultrashort pulse laser, in particular to an optical fiber stretcher and a frequency-adjustable all-fiber ultrashort pulse laser. Background Art

[0002] Mode-locked ultrashort pulse lasers have low noise and stable power. The periodic pulse signals they generate have rich, equally spaced frequency components in the frequency domain, making them applicable to many precision measurement fields. Ultrashort pulse lasers can achieve long-distance, high-precision distance measurement, helping small satellites achieve 10 -8 It can also achieve high-precision frequency transmission, helping underwater detector groups to achieve 10 -11 It can also be used for clock synchronization at the order of 1000 MHz and for the generation of THz radar signals and detection of hazardous chemical gases.

[0003] When a mode-locked laser is used as a signal source, its repetition frequency often needs to be precisely controlled. r =c / l (where c is the speed of light and l is the length of the laser's resonant cavity). Controlling the laser's repetition rate depends on controlling the length of the laser's resonant cavity. Because the resonant cavity of an ultrashort pulse laser is susceptible to external interference, its pulse repetition rate is easily affected by the external environment.

[0004] As a high-precision signal source, pulse lasers usually require automatic control technology to control their repetition frequency. At the same time, a resonant cavity length adjustment mechanism is added to the laser. The automatic control circuit drives the adjustment mechanism according to the frequency difference between the laser and the reference source to ensure that the laser's repetition frequency is highly stable. However, in order to enable the mode-locked laser to match the operating frequency of the automatic control system, the laser's operating frequency needs to be adjusted over a large range. Generally, the following two methods are used to adjust the repetition frequency of femtosecond pulse lasers:

[0005] 1. Adding spatial optical structures to the laser, such as optical delay lines, will cause mechanical drift in the spatial optical path and will also be affected by temperature drift, mechanical vibration and external disturbances, making it impossible for the laser to work stably for a long time and inconvenient to work outside the laboratory environment. In addition, the laser with a spatial optical path adjusts the cavity length of the laser by adjusting the distance between each device in the spatial optical path, but this will make the laser structure complicated and the volume larger, making it inconvenient for integration. At the same time, the spatial optical path will move after a period of time, which greatly reduces the long-term stability of the laser.

[0006] 2. Eliminating the spatial optical structure, the laser adopts an all-fiber structure, which offers excellent stability and a compact size. However, to adjust the cavity length, the traditional approach is to attach the optical fiber to a piezoelectric ceramic and drive the piezoelectric ceramic to stretch the fiber. However, due to the limitations of the piezoelectric ceramic's adjustment capabilities and the fiber's elastic range, the cavity length can only be adjusted within a few tens of microns, enabling only kHz-level frequency adjustment. Summary of the Invention

[0007] The present invention aims to solve the problem that when adjusting the repetition frequency of existing femtosecond pulse lasers, if a structure in which spatial light is added is adopted, the structure will become complicated, the volume will become larger, the integration will be inconvenient, and the stability will be poor; or if an all-fiber structure is adopted, the adjustment frequency range will be small. The present invention provides an optical fiber stretcher and a frequency-adjustable all-fiber ultrashort pulse laser.

[0008] The technical solution adopted in the present invention is:

[0009] An optical fiber stretcher, which is special in that:

[0010] including a piezoelectric ceramic block;

[0011] A fixed plate and a load-bearing plate are symmetrically arranged along the y-axis;

[0012] A first amplifying plate and a second amplifying plate are symmetrically arranged along the x-axis, and the first amplifying plate and the second amplifying plate are T-shaped structures arranged facing each other;

[0013] a first connecting plate disposed between the fixed plate and the first amplifying plate, a second connecting plate disposed between the fixed plate and the second amplifying plate, a third connecting plate disposed between the force-bearing plate and the second amplifying plate, and a fourth connecting plate disposed between the force-bearing plate and the first amplifying plate;

[0014] The second connecting plate and the third connecting plate are structurally symmetrical along the y-axis, and the first connecting plate and the fourth connecting plate are structurally symmetrical along the y-axis; the second connecting plate and the first connecting plate are structurally symmetrical along the x-axis; and the third connecting plate and the fourth connecting plate are structurally symmetrical along the x-axis;

[0015] The second connecting plate and the fixed plate, the fixed plate and the first connecting plate, the first connecting plate and the first amplifying plate, the first amplifying plate and the fourth connecting plate, the fourth connecting plate and the force-bearing plate, the force-bearing plate and the third connecting plate, the third connecting plate and the second amplifying plate, and the second amplifying plate and the second connecting plate are connected to form a cylinder with an x-direction rectangular groove through eight flexible sheets arranged along the x-direction, and the outer surface of the cylinder is used for winding the optical fiber;

[0016] The piezoelectric ceramic block is arranged in the x-direction rectangular groove, and its two ends respectively support the inner end surface of the fixing plate and the force-bearing plate.

[0017] Furthermore, the elongation Δl of the optical fiber can be calculated according to the following formula (1):

[0018] Δl=n(2πΔy+4(Δx-Δy)) (1)

[0019] Where n is the number of turns of the optical fiber wound around the outer surface of the cylinder; Δy is the displacement of the first amplifying plate relative to the second amplifying plate in the y-axis direction, and Δy is calculated according to the formula Δy = Δx·cotθ, Δx is the elongation of the piezoelectric ceramic block, and the angle θ is defined as: the angle between the line a connecting the center points of the flexible plates at both ends of any connecting plate and the elongation direction b of the piezoelectric ceramic block.

[0020] Furthermore, a thread groove is provided on the outer side of the cylinder to limit the movement of the optical fiber.

[0021] Furthermore, the diameter D of the cylinder is greater than 20 mm, so as to prevent excessive bending loss of the optical fiber.

[0022] Furthermore, positioning holes are symmetrically provided on the fixing plate and the force-bearing plate along the x-axis.

[0023] The present invention also discloses a frequency-adjustable all-fiber ultrashort pulse laser, which is special in that:

[0024] The invention comprises a first pump light source and a second pump light source installed outside a shell, and a fiber resonant cavity installed inside the shell, wherein the fiber resonant cavity comprises a saturable absorption reflector, an optical fiber and an output mirror arranged in sequence, wherein both ends of the optical fiber are connected to the saturable absorption reflector and the output mirror respectively, and the first pump light source and the second pump light source are connected to the saturable absorption reflector and the output mirror respectively through transmission optical fibers, wherein the pump light of the laser is coupled into the fiber resonant cavity via the saturable absorption reflector through the first pump light source, or the pump light of the laser is coupled into the fiber resonant cavity via the output mirror through the second pump light source; the invention also comprises the fiber stretcher; and the middle section of the optical fiber is coiled on the outer side surface of the cylindrical body of the fiber stretcher.

[0025] Furthermore, in order to prevent the operation of the optical fiber stretcher from affecting the stability of other devices, a first optical fiber fixing structure and a second optical fiber fixing structure are respectively provided on the outer side of the thread groove. The first optical fiber fixing structure and the second optical fiber fixing structure are mounted on the housing and are used to compress the optical fiber wound on the outer side of the cylinder.

[0026] Furthermore, the first optical fiber fixing structure and the second optical fiber fixing structure both adopt an arc-shaped pressing plate, the arc-shaped surface of the arc-shaped pressing plate is adapted to the outer side surface of the cylinder, and an elastic member is further provided between the arc-shaped pressing plate and the optical fiber.

[0027] Furthermore, in order to protect the piezoelectric ceramic block from being damaged by the reaction force generated by the fixed plate and the force-bearing plate during extension, a first gasket is arranged between the piezoelectric ceramic block and the fixed plate, and a second gasket is arranged between the piezoelectric ceramic block and the force-bearing plate. The thickness of the first gasket and the second gasket are both 0.1 to 3 mm, and the materials of the first gasket and the second gasket are both metal, ceramic or organic materials.

[0028] The fixing plate and the force-bearing plate are both symmetrically provided with positioning holes along the x-axis for fixing the optical fiber stretcher on the housing; or the fixing plate and the force-bearing plate are fixed on the housing by bonding.

[0029] Furthermore, the total length of the optical fiber is 100 mm to 2500 mm, and more than 30% of the optical fiber is coiled on the outer side of the cylinder, thereby increasing the adjustment range of the laser repetition frequency.

[0030] The optical fiber includes a gain fiber segment and a single-mode polarization-maintaining fiber segment. The gain fiber segment accounts for 15% to 100% of the total length of the optical fiber. The gain fiber segment is made of rare-earth-doped polarization-maintaining fiber. The gain fiber segment is used to amplify the optical signal, while the single-mode polarization-maintaining fiber segment is used to adjust the resonant cavity length. The gain fiber segment and the single-mode polarization-maintaining fiber segment jointly balance the dispersion and gain within the resonant cavity.

[0031] Compared with the prior art, the present invention has the following beneficial effects.

[0032] 1. The present invention employs a fiber stretcher with a simple structure and ingenious design. Under the action of a bias voltage, stress is generated at both ends of the piezoelectric ceramic block. Since the fixed plate, the force-bearing plate, and the first and second amplifier plates are connected by flexible sheets, the thrust generated by the piezoelectric ceramic block is simultaneously transmitted to the fixed and force-bearing plates, causing them to displace. The fixed and force-bearing plates then transmit the thrust to the flexible mechanism in the fiber stretcher, generating stress within the mechanism. The elasticity of the material then causes the first and second amplifier plates in the fiber stretcher to displace, increasing the diameter of the fiber stretcher and stretching the optical fiber wound thereon. Furthermore, the fiber stretcher (excluding the gasket and piezoelectric ceramic block) is made from a single metal block by wire cutting, resulting in excellent mechanical stability, maintaining stability even in a vibrating environment. Furthermore, assembly requires only wrapping the optical fiber around the stretcher, making assembly simple.

[0033] 2. The present invention adopts a frequency-adjustable all-fiber ultrashort pulse laser. By setting a fiber stretcher in the laser, the laser cavity length can be changed by stretching the fiber, ensuring that the laser cavity length can be adjusted by a maximum of 0.1%, that is, the laser repetition frequency adjustment range reaches 0.1%. For example, for a laser with a repetition frequency of 200MHz, the repetition frequency adjustment range can reach a maximum of 200kHz, which is an order of magnitude higher than the general solution of directly stretching the optical fiber with piezoelectric ceramics.

[0034] At the same time, all optical components in the laser are connected by optical fibers and are packaged in The cylindrical hollow tube allows the entire laser to withstand mechanical shocks of at least one gravitational acceleration. All components are connected by optical fiber, ensuring a stable optical path. Even if the laser housing deforms due to temperature fluctuations, this does not affect the laser's stability, thus preventing the influence of the external environment.

[0035] 3. The present invention adopts a frequency-adjustable all-fiber ultrashort pulse laser. Apart from the optical fiber, the entire laser only has optical devices at both ends of the resonant cavity, which achieves the maximum simplification of the femtosecond laser and reduces the volume of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is an external structural diagram of a frequency-adjustable all-fiber ultrashort pulse laser according to the present invention.

[0037] Figure 2 This is a schematic diagram of a frequency-adjustable all-fiber ultrashort pulse laser according to the present invention.

[0038] Figure 3 This is a diagram of the internal structure of a frequency-adjustable all-fiber ultrashort pulse laser of the present invention.

[0039] Figure 4 This is a structural schematic diagram of a fiber stretcher in a frequency-adjustable all-fiber ultrashort pulse laser of the present invention.

[0040] Figure 5 The figure is a schematic structural diagram of the threaded groove on the outer side surface of the cylindrical body of a fiber stretcher in a frequency-adjustable all-fiber ultrashort pulse laser of the present invention.

[0041] In the picture:

[0042] 1-cover plate;

[0043] 2-housing, 3-optical fiber, 4-optical fiber stretcher; 21-saturable absorption reflector, 22-output mirror, 23-first pump light source, 24-second pump light source;

[0044] 31 - first optical fiber fixing structure, 32 - second optical fiber fixing structure, 33 - first pressing plate, 34 - second pressing plate, 35 - third pressing plate;

[0045] 401 - piezoelectric ceramic block, 402 - fixing plate, 403 - force-bearing plate, 408 - first connecting plate, 409 - second connecting plate, 410 - third connecting plate, 411 - fourth connecting plate, 416 - first amplifying plate, 417 - second amplifying plate, 418 - first gasket, 419 - second gasket, 420 - positioning hole;

[0046] 404 - first flexible hinge, 412 - second flexible hinge;

[0047] 424-thread groove. DETAILED DESCRIPTION

[0048] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are not intended to limit the present invention.

[0049] like Figure 1 、 Figure 2 and Figure 3 As shown, a frequency-adjustable all-fiber ultrashort pulse laser in this embodiment includes a cover plate 1 and a shell 2, wherein the shell 2 is used to support and fix various components in the laser.

[0050] A first pump light source 23 and a second pump light source 24 are provided outside the shell 2, and a fiber resonant cavity is provided inside the shell 2. The fiber resonant cavity includes a saturable absorption reflector 21 with a wavelength division multiplexing function, an optical fiber 3 and an output mirror 22 with a wavelength division multiplexing function arranged in sequence. The two ends of the optical fiber 3 are respectively connected to the saturable absorption reflector 21 and the output mirror 22, and a linear laser resonant cavity is built using the optical fiber 3. The first pump light source 23 and the second pump light source 24 are connected to the saturable absorber reflector 21 and the output mirror 22 respectively through transmission optical fibers, and are located on both sides of the resonant cavity. The pump light of the laser is coupled into the optical fiber resonant cavity through the first pump light source 23 via the saturable absorber reflector 21, or the pump light of the laser is coupled into the optical fiber resonant cavity through the second pump light source 24 via the output mirror 22. The wavelengths of the first pump light source and the second pump light source are both 980±10nm or 1480±10nm. The saturable absorber reflector 21 uses a saturable absorber reflector composite device SESAM operating at 1550nm, so that the laser can operate in a mode-locked state and generate femtosecond pulses. The output mirror 22 uses an output mirror composite device with wavelength division parameters of 980 / 1550nm or 1480 / 1550nm, an operating range of ±10nm, and an output ratio of 20%. The optical fiber stretcher 4 is also included and is made of metal, ceramic or ceramic.

[0051] In this embodiment, the total length of the optical fiber 3 is 445 mm, and 92% of the optical fiber is coiled on the outer side of the cylinder, thereby increasing the adjustment range of the laser repetition frequency.

[0052] The optical fiber 3 includes a gain fiber segment and a single-mode polarization-maintaining fiber segment. The gain fiber segment is 310 mm long, and the single-mode polarization-maintaining fiber segment is 135 mm long. The single-mode polarization-maintaining fiber segment is disposed within the resonant cavity and is used to connect the saturable absorber reflector 21 and the output mirror 22. The gain fiber segment is used to amplify the optical signal, and the single-mode polarization-maintaining fiber segment is used to adjust the resonant cavity length. The gain fiber segment and the single-mode polarization-maintaining fiber segment jointly balance dispersion and gain within the resonant cavity.

[0053] The gain fiber segment is a rare-earth-doped polarization-maintaining fiber with a spontaneous emission center of 1530 nm and positive dispersion. The transmission fiber is a single-mode polarization-maintaining fiber. In this embodiment, all single-mode polarization-maintaining fibers have negative dispersion.

[0054] To define the positions of the saturable absorber reflector 21 and the output mirror 22 on the housing 2, a first pressure plate 33 and a second pressure plate 34 are placed on their upper surfaces, respectively. Spacious space remains within the housing 2 for additional optical fiber components. A third pressure plate 35 is placed in the space provided to secure the components.

[0055] like Figure 4 As shown, the optical fiber stretcher 4 includes a piezoelectric ceramic block 401, and the piezoelectric ceramic block 401 is in the shape of a rectangular plate or a cylindrical plate;

[0056] A fixed plate 402 and a force-bearing plate 403 are symmetrically arranged along the y-axis;

[0057] A first amplifying plate 416 and a second amplifying plate 417 are symmetrically arranged along the x-axis, and the first amplifying plate 416 and the second amplifying plate 417 are T-shaped structures arranged facing each other;

[0058] a first connecting plate 408 disposed between the fixed plate 402 and the first amplifying plate 416 , a second connecting plate 409 disposed between the fixed plate 402 and the second amplifying plate 417 , a third connecting plate 410 disposed between the force-bearing plate 403 and the second amplifying plate 417 , and a fourth connecting plate 411 disposed between the force-bearing plate 403 and the first amplifying plate 416 ;

[0059] The second connecting plate 409 and the third connecting plate 410 are structurally symmetrical along the y-axis, and the first connecting plate 408 and the fourth connecting plate 411 are structurally symmetrical along the y-axis; the second connecting plate 409 and the first connecting plate 408 are structurally symmetrical along the x-axis; and the third connecting plate 410 and the fourth connecting plate 411 are structurally symmetrical along the x-axis.

[0060] The second connecting plate 409 and the fixed plate 402, the fixed plate 402 and the first connecting plate 408, the first connecting plate 408 and the first amplifying plate 416, the first amplifying plate 416 and the fourth connecting plate 411, the fourth connecting plate 411 and the force-bearing plate 403, the force-bearing plate 403 and the third connecting plate 410, the third connecting plate 410 and the second amplifying plate 417, and the second amplifying plate 417 and the second connecting plate 409 are connected to form a cylinder with an x-direction rectangular groove via eight flexible pieces arranged along the x-direction; the eight flexible pieces are all perpendicular to the circular end surface of the cylinder;

[0061] The piezoelectric ceramic block 401 is arranged in the x-direction rectangular groove, and its two ends respectively support the inner end surfaces of the fixing plate 402 and the force-bearing plate 403.

[0062] To prevent the operation of the fiber stretcher 4 from affecting the stability of other components, a first fiber securing structure 31 and a second fiber securing structure 32 are provided on either side of the cylindrical body. Both structures utilize curved pressure plates, each with the same curvature as the outer surface of the cylindrical body. An elastic member, such as rubber or a high-hardness sponge, is positioned between the curved pressure plate and the optical fiber. While the elastic member supports the optical fiber, the curved pressure plate presses against it to prevent damage.

[0063] In this embodiment, the fiber stretcher 4 is driven by a voltage signal. Its diameter increases as the driving voltage increases, thereby stretching the length of the optical fiber wrapped around its cylindrical exterior. Specifically, the fiber stretcher has a rectangular piezoelectric ceramic block 401 at its geometric center. Under the action of a bias voltage, the piezoelectric ceramic block 401 stretches at both ends, generating thrust in both directions. Because the fixed plate 402 and the force-bearing plate 403 are in close contact with the piezoelectric ceramic block 401 via the first and second gaskets 418 and 419, the thrust generated by the piezoelectric ceramic block 401 is simultaneously transmitted to the fixed plate 402 and the force-bearing plate 403, causing them to displace, thereby generating stress within the fiber stretcher 4. The flexible structure within the stretcher 4 then transmits this stress to the first and second amplifying plates 416 and 417, causing them to displace. This results in the fiber stretcher's diameter increasing. The fiber stretcher stretches the length of the optical fiber wrapped around its side by adjusting its own diameter to adjust the laser cavity length, thereby achieving the effect of adjusting the laser pulse repetition frequency.

[0064] In this embodiment, the optical fiber stretcher 4 can be made of a metal such as steel, aluminum-magnesium alloy, or copper alloy. Its diameter D is primarily determined by the total length c of the optical fiber wound thereon and the number n of turns of the optical fiber. The number of turns of the optical fiber 3 wound around the optical fiber stretcher 4 is n = m + 0.5, where m is a positive integer ≥ 1. In this embodiment, c = 445 mm. m is 2, i.e., n = 2.5. Thus, the diameter D can be calculated as c / n / π = 56.66 mm. The thickness of the optical fiber stretcher 4 is 0.9 to 1.1 times the thickness of the piezoelectric ceramic block 401. In this embodiment, the thickness of the piezoelectric ceramic block 401 and the thickness of the cylindrical optical fiber stretcher 4 are both 7 mm.

[0065] The elongation Δl of the optical fiber can be calculated according to the following formula:

[0066] Δl=n(2πΔy+4(Δx-Δy)) (1)

[0067] Wherein, n is the number of turns of the optical fiber coiled around the outer surface of the cylinder, Δy is the displacement of the first amplifying plate 416 relative to the second amplifying plate 417 in the y-axis direction, and Δy is calculated according to the formula Δy=Δx·cotθ, Δx is the elongation of the piezoelectric ceramic block 401, and the angle θ is defined as: the angle between the line a connecting the center points of the flexible plates at both ends of any connecting plate and the elongation direction b of the piezoelectric ceramic block 401.

[0068] The specific working principle of the optical fiber stretcher in this embodiment is as follows:

[0069] A piezoelectric ceramic block 401 is placed along one of the diameters of the fiber stretcher 4, with their geometric centers coinciding. A fixed plate 402 and a force-bearing plate 403 are positioned at either end of the piezoelectric ceramic block 401. When voltage is applied to the piezoelectric ceramic block 401, the block 401 extends in the direction indicated by the arrows in the figure, with the elongation length Δx. The thrust generated by the elongation of the piezoelectric ceramic block 401 is transmitted to the fiber stretcher 4 via the fixed plate 402 and the force-bearing plate 403, causing the block 401 to deform in the direction of its extension.

[0070] The eight flexible plates include four first flexible hinges 404 and four second flexible hinges 412. The internal stress generated by the deformation of the optical fiber stretcher 4 is transmitted by the four first flexible hinges 404 to the first connecting plate 408, the second connecting plate 409, the third connecting plate 410, and the fourth connecting plate 411. The first connecting plate 408, the second connecting plate 409, the third connecting plate 410, and the fourth connecting plate 411 then transmit the stress to the four second flexible hinges 412. Ultimately, the internal stress of the optical fiber stretcher 4 is transmitted to the first amplifying plate 416 and the second amplifying plate 417 via the four second flexible hinges 412, causing the first amplifying plate 416 and the second amplifying plate 417 to move in a direction perpendicular to the elongation of the piezoelectric ceramic block 401 and generate a displacement Δy in opposite directions. Since the first connecting plate 408, the second connecting plate 409, the third connecting plate 410, the fourth connecting plate 411, and the four pairs of flexible hinges at their ends are symmetrically distributed relative to the geometric center of the optical fiber stretcher 4, the magnitude of Δy is mainly determined by Figure 4 The angle θ in the equation is defined as the angle between the line a connecting the center points of the flexible hinges at either end of the connecting plate and the direction b of the piezoelectric ceramic block 401's extension. Since the displacement of the piezoelectric ceramic block 401 is approximately 0.1% of its total length, Δy and Δx have an approximately linear relationship: Δy / Δx = 0.5cotθ. When the elongation Δx of the piezoelectric ceramic block 401 is 40μm and the angle θ is 45 degrees, the displacement Δy of the first amplifying plate 416 relative to the second amplifying plate 417 is 40μm × cot45° = 40μm. This means that the fiber stretcher 4 extends by 40μm in the direction perpendicular to the extension of the piezoelectric ceramic block 401. At this point, the increase in its circumference can be roughly considered to be Δl = n(2πΔy + 4(Δx - Δy)) = 2.5π × 40μm = 314.2μm, which is also the elongation of the optical fiber.

[0071] To protect piezoelectric ceramic block 401 from damage by the reaction force generated by fixed plate 402 and force-bearing plate 403 during its extension, a first gasket 418 and a second gasket 419 are inserted between piezoelectric ceramic block 401 and fixed plate 402, and between piezoelectric ceramic block 401 and force-bearing plate 403, respectively. Both first gasket 418 and second gasket 419 can be made of metal, ceramic, or organic material, have a thickness of approximately 0.1 to 3 mm, and can be square or hemispherical in shape.

[0072] Furthermore, two positioning holes are added near the fixing plate 402 and the force-bearing plate 403, that is, a total of four positioning holes 420, which are used to fix the position of the entire optical fiber stretcher 4 on the housing 2, and screws are installed in the positioning holes 420 for fixing; or epoxy resin or other glue can be directly used to stick the fixing plate 402 or the force-bearing plate 403 to the position where it needs to be fixed, instead of these four positioning holes.

[0073] like Figure 5 As shown, in order to limit the movement of the optical fiber, a thread groove is further provided on the outer side of the cylinder. The fixing plate 402 is fixed to the all-fiber ultrashort pulse laser to be installed by screws.

[0074] The above descriptions are merely embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent structural transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied to other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. An optical fiber stretcher, characterized in that: comprising a piezoelectric ceramic block (401); A fixed plate (402) and a force-bearing plate (403) are symmetrically arranged along the y-axis; A first amplifying plate (416) and a second amplifying plate (417) are symmetrically arranged along the x-axis, and the first amplifying plate (416) and the second amplifying plate (417) are T-shaped structures; A first connecting plate (408) is provided between the fixing plate (402) and the first amplifying plate (416), a second connecting plate (409) is provided between the fixing plate (402) and the second amplifying plate (417), a third connecting plate (410) is provided between the force-bearing plate (403) and the second amplifying plate (417), and a fourth connecting plate (411) is provided between the force-bearing plate (403) and the first amplifying plate (416); The second connecting plate (409) and the third connecting plate (410) are structurally symmetrical along the y-axis, and the first connecting plate (408) and the fourth connecting plate (411) are structurally symmetrical along the y-axis; the second connecting plate (409) and the first connecting plate (408) are structurally symmetrical along the x-axis; and the third connecting plate (410) and the fourth connecting plate (411) are structurally symmetrical along the x-axis. The second connecting plate (409) and the fixed plate (402), the fixed plate (402) and the first connecting plate (408), the first connecting plate (408) and the first amplifying plate (416), the first amplifying plate (416) and the fourth connecting plate (411), the fourth connecting plate (411) and the force-bearing plate (403), the force-bearing plate (403) and the third connecting plate (410), the third connecting plate (410) and the second amplifying plate (417), and the second amplifying plate (417) and the second connecting plate (409) are connected to form a cylinder with an x-direction rectangular groove through eight flexible sheets arranged along the x-direction, and the outer side surface of the cylinder is used for winding the optical fiber (3); The piezoelectric ceramic block (401) is arranged in an x-direction rectangular groove, and its two ends respectively support the inner end surfaces of the fixing plate (402) and the force-bearing plate (403).

2. The optical fiber stretcher according to claim 1, wherein: The elongation Δl of the optical fiber can be calculated according to the following formula (1): Δl=n (2πΔy+4(Δx-Δy)) (1) Wherein, n is the number of turns of the optical fiber wound on the outer side of the cylinder, Δy is the displacement of the first amplifying plate (416) relative to the second amplifying plate (417) in the y-axis direction, and Δy is calculated according to the formula Δy=Δx·cotθ, Δx is the elongation of the piezoelectric ceramic block (401), and the angle θ is defined as: the angle between the line a connecting the center points of the flexible plates at both ends of any connecting plate and the elongation direction b of the piezoelectric ceramic block (401).

3. The optical fiber stretcher according to claim 1 or 2, characterized in that: A thread groove (424) is also provided on the outside of the cylinder for limiting the movement of the optical fiber (3).

4. The optical fiber stretcher according to claim 3, characterized in that: The diameter D of the cylinder is greater than 20 mm.

5. The optical fiber stretcher according to claim 4, characterized in that: Positioning holes (420) are symmetrically provided on the fixing plate (402) and the force-bearing plate (403) along the x-axis.

6. A frequency-tunable all-fiber ultrashort pulse laser, characterized by: The invention comprises a first pump light source (23) and a second pump light source (24) installed outside a housing (2), and a fiber resonant cavity installed in the housing (2), wherein the fiber resonant cavity comprises a saturable absorption reflector (21), an optical fiber (3) and an output mirror (22) arranged in sequence, wherein both ends of the optical fiber (3) are connected to the saturable absorption reflector (21) and the output mirror (22), respectively, and the first pump light source (23) and the second pump light source (24) are connected to the saturable absorption reflector (21) and the output mirror (22) respectively through transmission optical fibers, and the pump light of the laser is coupled to the fiber resonant cavity through the first pump light source (23) via the saturable absorption reflector (21), or the pump light of the laser is coupled to the fiber resonant cavity through the second pump light source (24) via the output mirror (22); and further comprises a fiber stretcher (4) as described in any one of claims 3 to 4; and the middle section of the optical fiber (3) is coiled on the outer side surface of the cylindrical body of the fiber stretcher (4).

7. The frequency-tunable all-fiber ultrashort pulse laser according to claim 6, characterized in that: A first optical fiber fixing structure (31) and a second optical fiber fixing structure (32) are respectively provided on the outside of the thread groove (424); the first optical fiber fixing structure (31) and the second optical fiber fixing structure (32) are mounted on the housing (2) and are used to compress the optical fiber (3) wound on the outer side of the cylinder.

8. The frequency-tunable all-fiber ultrashort pulse laser according to claim 7, characterized in that: The first optical fiber fixing structure (31) and the second optical fiber fixing structure (32) both adopt an arc-shaped pressing plate, the arc-shaped surface of the arc-shaped pressing plate is adapted to the outer side surface of the cylinder, and an elastic member is also provided between the arc-shaped pressing plate and the optical fiber.

9. The frequency-tunable all-fiber ultrashort pulse laser according to any one of claims 6 to 8, characterized in that: A first gasket (418) is provided between the piezoelectric ceramic block (401) and the fixed plate (402), and a second gasket (419) is provided between the piezoelectric ceramic block (401) and the force-bearing plate (403). The thickness of the first gasket (418) and the second gasket (419) are both 0.1 to 3 mm, and the materials of the first gasket (418) and the second gasket (419) are both metal, ceramic or organic materials. Positioning holes (420) are symmetrically provided on the fixing plate (402) and the force-bearing plate (403) along the x-axis for fixing the optical fiber stretcher (4) on the housing (2); or the fixing plate (402) and the force-bearing plate (403) are fixed to the housing (2) by bonding.

10. The frequency-tunable all-fiber ultrashort pulse laser according to claim 9, characterized in that: The total length of the optical fiber (3) is 100 mm to 2500 mm, and more than 30% of the optical fiber (3) is coiled on the outer side of the cylinder; The optical fiber (3) comprises a gain fiber segment and a single-mode polarization-maintaining fiber segment, and the gain fiber segment accounts for 15% to 100% of the total length of the optical fiber (3). The gain fiber segment adopts rare-earth-doped polarization-maintaining fiber.

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