Delay-adjustable fiber ring and frequency-adjustable crystal cavity mirror pulse laser

Abstract

The present invention provides a delay-adjustable fiber ring and a frequency-adjustable crystal cavity mirror pulse laser, primarily addressing the problems of existing pulse lasers with a small frequency adjustment range and low frequency adjustment accuracy. The delay-adjustable fiber ring includes a fiber stretcher, an optical fiber, a first phase shifter, a wavelength division multiplexer, and a polarization beam splitter. The fiber stretcher is a cylindrical structure, with the optical fiber wrapped around its sidewalls, and its two ends connected to the first phase shifter and the wavelength division multiplexer, respectively. The polarization beam splitter is disposed at the output ends of the wavelength division multiplexer and the first phase shifter, with the output ends of the wavelength division multiplexer and the first phase shifter being perpendicular to each other. Furthermore, the frequency-adjustable crystal cavity mirror pulse laser provided by the present invention includes a delay-adjustable fiber ring, a polarization controller, and a position-adjustable crystal cavity mirror, which are sequentially arranged.

Description

Technical Field

[0001] The invention relates to a frequency-adjustable picosecond pulse laser, in particular to a delay-adjustable optical fiber ring and a frequency-adjustable crystal cavity mirror pulse laser. Background Art

[0002] Picosecond lasers can achieve periodic pulses through mode locking or gain switching techniques. The pulse length is usually in picoseconds (10 -12 seconds) and femtoseconds (10 -15 The theoretical basis of this technology is to introduce fixed-period modulation into the laser resonator, thereby utilizing the gain and nonlinear effects within the cavity to generate fixed-period pulses. These pulses can produce pulse signals of various shapes, such as Gaussian or hyperbolic secant pulses. Furthermore, these pulses can have extremely short durations, even reaching the femtosecond level.

[0003] When a pulsed laser is used as a signal source, its repetition frequency f needs to be precisely controlled. r Because f 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 a pulsed laser is susceptible to external interference, the pulse repetition rate is easily affected by the external environment.

[0004] When a pulsed laser is used as a high-precision signal source, a resonant cavity length adjustment mechanism is usually added to the laser. Its repetition frequency is controlled by an automatic control circuit. 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 rate is highly stable. However, in order to match the operating frequency of the automatic control system with the mode-locked laser, the laser's operating frequency needs to be adjusted over a large range. The following two methods are generally used to adjust the repetition frequency of a femtosecond pulsed laser:

[0005] 1. Incorporating a spatial optical path within the laser, such as an optical delay line, is a method for achieving this. This optical delay line uses a stepper motor to control a reflector mounted on a guide rail. However, stepper motors have low precision, achieving adjustment accuracy on the order of millimeters at best. Furthermore, the movement of stepper motors is transmitted via gears, and the gaps between the gears result in poor repeatability of the optical delay line, resulting in low control accuracy for the entire system and, consequently, low frequency adjustment precision.

[0006] 2. The mechanical adjustment mechanism is removed, and all components in the laser are connected to the base plate. This method has good stability and a small size. However, to adjust the cavity length of the resonant cavity, the resonant cavity reflector needs to be attached to the piezoelectric ceramic. The position of the reflector is adjusted by driving the piezoelectric ceramic to achieve the cavity length adjustment of the resonant cavity. However, this method is limited by the adjustment capability of the piezoelectric ceramic. The cavity length adjustment range of the resonant cavity is no more than tens of microns, and it can only achieve frequency adjustment in the kHz range. Summary of the Invention

[0007] In order to solve the problems of small frequency adjustment range and low frequency adjustment accuracy in existing pulse lasers, the present invention provides a delay-adjustable optical fiber ring and a frequency-adjustable crystal cavity mirror pulse laser.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A delay-adjustable optical fiber ring, comprising an optical fiber stretcher, an optical fiber, a first phase shifter, a wavelength division multiplexer and a polarization beam splitter; the optical fiber stretcher is a cylindrical structure, the optical fiber is wound on the side wall of the optical fiber stretcher, and its two ends are respectively connected to the first phase shifter and the wavelength division multiplexer; the polarization beam splitter is arranged at the output ends of the wavelength division multiplexer and the first phase shifter, and the output ends of the wavelength division multiplexer and the first phase shifter are perpendicular to each other; the optical fiber stretcher comprises a first piezoelectric ceramic block; a first force-bearing plate and a second force-bearing plate symmetrically arranged along the y-axis; a first amplifying plate and a second amplifying plate symmetrically arranged along the x-axis, and the first amplifying plate and the second amplifying plate are T-shaped structures arranged facing each other; a first connecting plate arranged between the first force-bearing plate and the first amplifying plate; a second connecting plate arranged between the first force-bearing plate and the second amplifying plate; a third connecting plate arranged between the second force-bearing plate and the second amplifying plate; a fourth connecting plate arranged between the second force-bearing plate and the first amplifying plate; the second connecting plate and the third connecting plate are symmetrical along the y-axis structure, the first The 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; the third connecting plate and the fourth connecting plate are structurally symmetrical along the x-axis; the second connecting plate and the first force-bearing plate, the first force-bearing 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 second force-bearing plate, the second 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 respectively connected to form a cylinder with a rectangular groove inside through eight flexible plates arranged along the X-direction, the length direction of the rectangular groove is the x-axial direction, and the width direction is the y-axis direction; the first piezoelectric ceramic block is arranged in the rectangular groove, and the displacement generated by the first piezoelectric ceramic block is transmitted to the first force-bearing plate and the second force-bearing plate respectively, and the first force-bearing plate and the second force-bearing plate transmit the displacement to the first amplifying plate and the second amplifying plate, so that the length of the optical fiber wound on the optical fiber stretcher changes, thereby realizing frequency adjustment.

[0010] Furthermore, the elongation Δl of the optical fiber is calculated as follows:

[0011] Δl=p(2πΔy+4(Δx-Δy))

[0012] Δy=Δx·cotθ

[0013] Where p is the number of turns of the optical fiber wound around the optical fiber stretcher, Δy is the displacement of the first amplifying plate relative to the second amplifying plate in the y-axis direction, Δx is the elongation of the first piezoelectric ceramic block, and θ is 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.

[0014] Furthermore, it also includes a continuous light laser, which is arranged on one side of the incident surface of the polarization beam splitter, and the optical axis of the continuous light laser is coaxial with the optical axis of the wavelength division multiplexer.

[0015] Furthermore, a thread groove is provided on the side wall of the optical fiber stretcher, and the optical fiber is wound on the optical fiber stretcher through the thread groove.

[0016] Furthermore, the optical fiber includes a common transmission optical fiber and a gain optical fiber, the gain optical fiber is wound on the optical fiber stretcher, and the common transmission optical fiber is used to connect the gain optical fiber and the first phase shifter, and the gain optical fiber and the wavelength division multiplexer respectively.

[0017] Furthermore, a first gasket and a second gasket are provided between the first piezoelectric ceramic block and the first force-bearing plate and the second force-bearing plate.

[0018] At the same time, the present invention also provides a frequency-adjustable crystal cavity mirror pulse laser, comprising a polarization controller, a position-adjustable crystal cavity mirror, and a delay-adjustable optical fiber ring, wherein the delay-adjustable optical fiber ring, the polarization controller, and the position-adjustable crystal cavity mirror are arranged in sequence; the polarization controller comprises a wave plate, a second phase shifter, and a polarizer arranged in sequence;

[0019] The position-adjustable crystal cavity mirror includes a second piezoelectric ceramic block; a first strain plate and a second strain plate symmetrically arranged along the y-axis, and the first strain plate and the second strain plate are T-shaped structures arranged opposite to each other; a first support plate and a second support plate symmetrically arranged along the x-axis, and the first support plate and the second support plate are trapezoidal structures arranged opposite to each other; a first connecting plate arranged between the first strain plate and the first support plate, a second connecting plate arranged between the first support plate and the second strain plate, a third connecting plate arranged between the second strain plate and the second support plate, and a fourth connecting plate arranged between the second support plate and the first strain plate; the second connecting plate and the third connecting plate are symmetrical along the x-axis structure, and the first connecting plate and the fourth connecting plate are symmetrical along the x-axis structure; the second connecting plate and the first connecting plate are symmetrical along the y-axis structure, and the third connecting plate and the fourth connecting plate are symmetrical along the y-axis structure; the first strain The plate and the first connecting plate, the first connecting plate and the first supporting plate, the first supporting plate and the second connecting plate, the second connecting plate and the second strain plate, the second strain plate and the third connecting plate, the third connecting plate and the second supporting plate, the second supporting plate and the fourth connecting plate, and the fourth connecting plate and the first strain plate are respectively connected by eight flexible sheets arranged along the X direction to form a plate-like structure with a rectangular groove provided inside, wherein the length direction of the rectangular groove is the x-axial direction and the width direction is the y-axis direction; a coated crystal is provided on the first supporting plate or the second supporting plate; the second piezoelectric ceramic block is arranged in the rectangular groove, and the displacement generated by the second piezoelectric ceramic block is transmitted to the first strain plate and the second strain plate respectively, and the first strain plate and the second strain plate transmit the displacement to the first supporting plate and the second supporting plate, so that the displacement of the coated crystal changes, thereby realizing frequency adjustment.

[0020] Furthermore, the displacement δy of the coated crystal is calculated as follows:

[0021] δy=0.5×δx×cotγ

[0022] Wherein, δx is the elongation of the second piezoelectric ceramic block, and γ is the angle between the line n connecting the hinge center points at both ends of any connecting plate and the elongation direction m of the second piezoelectric ceramic block.

[0023] Furthermore, a first bonding plate and a second bonding plate are respectively provided between the second piezoelectric ceramic block and the first strain plate and the second strain plate. The first bonding plate and the first strain plate are connected through a first flexible plate, and the second bonding plate and the second strain plate are connected through a second flexible plate.

[0024] Furthermore, the phase delay amount of the second phase shifter is selected in the range of 0 to π, and the coating reflectivity of the coated crystal is in the range of 0 to 99%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention sequentially connects a delay-adjustable fiber ring, a polarization controller, and a position-adjustable crystal mirror to form a pulsed laser resonant cavity. The delay-adjustable fiber ring and position-adjustable crystal mirror each enable two levels of optical path adjustment, for a total of four levels of optical path adjustment, enabling wide-range, high-precision optical path adjustment.

[0027] 2. The fiber stretcher of the present invention has a simple structure, which reduces the cost of adjusting the laser cavity length. The flexible sheet used in the fiber stretcher uses the elasticity of the material to give some structures in the fiber stretcher motion characteristics. The deformation of the elastic body realizes the transmission of force and motion, realizes the stretching of the optical fiber on the fiber stretcher, and thus changes the laser cavity length. The fiber stretcher can ensure 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%, thereby achieving a wide range of adjustment. For example, the repetition frequency adjustment range of a laser with a repetition frequency of 100MHz can reach up to 100kHz, which is an order of magnitude higher than that of conventional piezoelectric ceramic direct stretching optical fiber.

[0028] 3. The delay-adjustable fiber ring of the present invention is also provided with a continuous light laser. The continuous light laser is an additional continuous laser coupled into the optical fiber. After the continuous laser enters the optical fiber, the nonlinear phase shift within the optical fiber can be adjusted over a large range, thereby achieving fine frequency adjustment of the laser frequency. The pulse frequency of the laser can be adjusted with mHz accuracy, thereby achieving high-precision adjustment.

[0029] 4. The present invention utilizes a position-adjustable crystal cavity mirror at one end of the laser resonator. This mirror primarily comprises a coated crystal and a position adjustment mechanism. The position adjustment mechanism is simple in structure. The flexible sheet utilizes the elasticity of the material to impart motion to a portion of the component. Force and motion are transmitted through elastic deformation, enabling position adjustment of the coated crystal and varying the laser cavity length. This provides the laser with a kHz-scale adjustment range and Hz-scale adjustment accuracy, thus enabling wide-ranging adjustment.

[0030] 5. The coated crystal of the present invention can adjust the nonlinear phase shift in the laser with higher precision by applying a control voltage, so that the frequency of the laser can be adjusted more finely, and the adjustment accuracy reaches the μHz level. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of the frequency-adjustable crystal cavity mirror pulse laser of the present invention;

[0032] Figure 2 This is a schematic structural diagram of the delay-adjustable optical fiber ring of the present invention;

[0033] Figure 3 This is a schematic structural diagram of the position-adjustable crystal cavity mirror of the present invention.

[0034] Figure 1: 1-delay adjustable fiber ring, 2-polarization controller, 3-position adjustable crystal cavity mirror, 11-fiber stretcher, 12-fiber, 13-first phase shifter, 14-wavelength division multiplexer, 15-polarization beam splitter, 16-continuous light laser, 17-pump laser, 21-wave plate, 22-second phase shifter, 23-polarizer, 31-coated crystal, 301-second piezoelectric ceramic block, 302-first strain plate, 303-second strain plate, 304-first hinge, 305-second hinge, 308-first connecting plate, 309-second connecting plate, 310-third Connecting plate, 311-fourth connecting plate, 316-first supporting plate, 317-second supporting plate, 318-first flexible plate, 319-second flexible plate, 320-first bonding plate, 321-second bonding plate, 401-first piezoelectric ceramic block, 402-first force-bearing plate, 403-second force-bearing plate, 404-first flexible sheet, 405-second flexible sheet, 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. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0036] The present invention provides a frequency-adjustable crystal cavity mirror pulse laser. This laser sequentially connects a delay-adjustable fiber ring, a polarization controller, and a position-adjustable crystal cavity mirror to form a resonant cavity. This resonant cavity is connected to a pump laser 17 to form a pulsed laser. The delay-adjustable fiber ring and the position-adjustable crystal cavity mirror each enable two levels of optical path adjustment, for a total of four levels of optical path adjustment, enabling high-precision adjustment of the optical path over a wide range.

[0037] like Figure 1 As shown in the figure, the frequency-adjustable crystal cavity mirror pulse laser of the present invention is mainly composed of three major units: a delay-adjustable fiber ring 1, a polarization controller 2, and a position-adjustable crystal cavity mirror 3. The laser light emitted by the delay-adjustable fiber ring 1 passes through the polarization controller 2 and is incident on the position-adjustable crystal cavity mirror 3. The position-adjustable crystal cavity mirror 3 reflects most of the laser light back and outputs part of it.

[0038] like Figure 1As shown, the delay-adjustable fiber ring 1 of the present invention includes a fiber stretcher 11, an optical fiber 12, a first phase shifter 13, a wavelength division multiplexer 14, a polarization beam splitter 15, and a continuous light laser 16. The fiber stretcher 11 is a cylindrical structure. The optical fiber 12 is wound around the sidewall of the fiber stretcher 11, with its ends connected to the first phase shifter 13 and the wavelength division multiplexer 14, respectively. The polarization beam splitter 15 is located at the output ends of the wavelength division multiplexer 14 and the first phase shifter 13, with the output ends of the wavelength division multiplexer 14 and the first phase shifter 13 perpendicular to each other. The optical fiber 12 is primarily composed of two types of optical fibers: a conventional transmission fiber and a gain fiber. The gain fiber accounts for more than 20% of the total length. The gain fiber is wound around the fiber stretcher 11, and the conventional transmission fiber is used to connect the gain fiber to the first phase shifter 13 and the gain fiber to the wavelength division multiplexer 14, respectively. A pump laser 17 directs pump light from the wavelength division multiplexer 14 into the optical fiber 12. The output ends of the first phase shifter 13 and the wavelength division multiplexer 14 are respectively directed to two perpendicular incident surfaces of the polarization beam splitter 15. The signal light of the continuous light laser 16 is incident on the third incident surface of the polarization beam splitter 15, which is opposite to the first phase shifter 13. The output laser light of the continuous light laser 16 is injected into the polarization beam splitter 15 and then enters the optical fiber 12 through the wavelength division multiplexer 14.

[0039] like Figure 1 As shown, the polarization controller 2 of the present invention is a phase adjustment mechanism. It includes a wave plate 21, a second phase shifter 22, and a polarizer 23, which are arranged in sequence. The phase delay of the second phase shifter 22 can be selected from 0 to π. The position-adjustable crystal cavity mirror 3 of the present invention includes a coated crystal 31 and a position adjustment mechanism. The coating reflectivity of the coated crystal 31 ranges from 0 to 99%. The coated crystal 31 is mounted on the position adjustment mechanism, and the displacement of the coated crystal 31 is adjusted by the position adjustment mechanism. The light output from the delay-adjustable fiber ring 1 passes through the wave plate 21, the second phase shifter 22, and the polarizer 23 in sequence, and is ultimately incident on the coated crystal 31 within the position-adjustable crystal cavity mirror 3. 90% of the light is reflected back from the coating layer of the coated crystal 31, and the remaining light is output.

[0040] like Figure 1 As shown, pump laser 17 couples pump light into optical fiber 12 via wavelength division multiplexer 14. The pump light is then converted into signal light within optical fiber 12. The signal light then travels through first phase shifter 13, is reflected by polarization beam splitter 15, and passes through wave plate 21, second phase shifter 22 with a phase delay of π / 6, and polarizer 23, ultimately reaching coated crystal 31. On the coated surface of the crystal, 90% of the signal is reflected back, leaving 10% as output light. The reflected light then returns along the original path, passes through polarization beam splitter 15, enters wavelength division multiplexer 14, and finally reaches optical fiber 12, completing a complete cycle.

[0041] like Figure 2 As shown, in the delay adjustable optical fiber ring 1 of the present invention, the slow axis of the wavelength division multiplexer 14 is placed in the horizontal direction, and the signal light is incident on the polarization beam splitter 15 along the horizontal polarization direction; the slow axis of the first phase shifter 13 is placed in the vertical direction, and the signal light is incident on the polarization beam splitter 15 along the vertical direction; the continuous light laser 16 is arranged on the side of the incident surface of the polarization beam splitter 15, and the optical axis of the continuous light laser 16 is coaxial with the optical axis of the wavelength division multiplexer 14, so that the signal light of the continuous light laser 16 is incident on the polarization beam splitter 15 along the horizontal direction.

[0042] To precisely adjust the phase delay of the adjustable-delay fiber ring 1, the light intensity of the continuous light laser 16 must be varied. To increase the phase delay, the light intensity of the continuous light laser 16 is reduced; to decrease the phase delay, the light intensity is increased. Therefore, the nonlinear phase shift within the optical fiber 12 can be adjusted by the continuous light laser 16, thereby achieving fine frequency regulation of the laser frequency and achieving high-precision control. To adjust the phase delay of the adjustable-delay fiber ring 1 over a wide range, the length of the optical fiber 12 loop wound around it must be adjusted using the fiber stretcher 11.

[0043] The specific structure of the optical fiber stretcher 11 of the present invention is as follows: the optical fiber stretcher 11 includes a first piezoelectric ceramic block 401; a first force-bearing plate 402 and a second force-bearing plate 403 symmetrically arranged along the y-axis; a first amplifying plate 416 and a second amplifying plate 417 symmetrically arranged along the x-axis, and the first amplifying plate 416 and the second amplifying plate 417 are T-shaped structures arranged opposite to each other; a first connecting plate 408 arranged between the first force-bearing plate 402 and the first amplifying plate 416, a second connecting plate 409 arranged between the first force-bearing plate 402 and the second amplifying plate 417, a third connecting plate 410 arranged between the second force-bearing plate 403 and the second amplifying plate 417, and a fourth connecting plate 411 arranged between the second force-bearing plate 403 and the first amplifying plate 416; the second connecting plate 409 and the third connecting plate 410 are symmetrical in structure along the y-axis, and the first connecting plate 408 and the fourth connecting plate 411 are symmetrical in structure along the y-axis; the second connecting plate 409 and the first connecting plate 408 is structurally symmetrical along the x-axis; 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 first force-bearing plate 402, the first force-bearing 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 second force-bearing plate 403, the second 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 respectively connected to form a cylinder with an x-direction rectangular groove through eight flexible plates arranged along the x-direction, the length direction of the rectangular groove is the x-axial direction, and the width direction is the y-axis direction, and a gain optical fiber is coiled on the outer side of the cylinder; the first piezoelectric ceramic block 401 is arranged in the x-direction rectangular groove, and its two ends respectively support the inner end faces of the first force-bearing plate 402 and the second force-bearing plate 403. The displacement generated by the first piezoelectric ceramic block 401 is transmitted to the first force-bearing plate 402 and the second force-bearing plate 403 respectively, and the first force-bearing plate 402 and the second force-bearing plate 403 transmit the displacement to the first amplifying plate 416 and the second amplifying plate 417, so that the length of the optical fiber 12 wound on the optical fiber stretcher 11 changes, realizing cavity length adjustment of the order of hundreds of microns, that is, realizing frequency adjustment.

[0044] In order to protect the first piezoelectric ceramic block 401 from being damaged by the reaction force generated by the first force-bearing plate 402 and the second force-bearing plate 403 during extension, a first gasket 418 and a second gasket 419 are inserted between the first piezoelectric ceramic block 401, the first force-bearing plate 402, and the second force-bearing plate 403, respectively. They can be made of ceramic, metal, or organic materials, with a thickness of approximately 0.1 to 3 mm and a square or hemispherical shape. In the example of the present invention, a square metal sheet with a thickness of 1 mm is selected. At the same time, a thread groove is also provided on the side wall of the optical fiber stretcher 11 of the present invention, and the optical fiber 12 is wound around the optical fiber stretcher 11 through the thread groove.

[0045] Under the influence of the bias voltage, the first piezoelectric ceramic block 401 stretches at both ends, generating thrust in both directions. Because the first and second force-bearing plates 402, 403 are in close contact with the first piezoelectric ceramic block 401 via the first and second gaskets 418, 419, the thrust generated by the first piezoelectric ceramic block 401 is simultaneously transmitted to the first and second force-bearing plates 402, 403, causing them to displace, thereby generating stress within the fiber stretcher 11. The flexible sheet within the fiber stretcher 114 then transmits this stress to the first and second amplifying plates 416, 417, causing them to displace, thereby increasing the diameter of the fiber stretcher 11. By adjusting its own diameter, the fiber stretcher 11 stretches the length of the optical fiber 12 wrapped around it, thereby adjusting the laser cavity length and thus achieving a wide range of modulation of the laser pulse repetition rate.

[0046] In the present invention, the flexible plates on both sides of the first connecting plate 408, the second connecting plate 409, the third connecting plate 410, and the fourth connecting plate 411 are staggered in the y-axis direction, that is, the first flexible plate 404 and the second flexible plate 405 are staggered in the y-axis direction. The first amplifying plate 416 and the second amplifying plate 417 move in a direction perpendicular to the extension of the first piezoelectric ceramic block 401 and generate displacements in opposite directions. The magnitude of the relative displacement Δy between them is mainly determined by Figure 2 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 extension direction b of the first piezoelectric ceramic block 401. Since the displacement of the first piezoelectric ceramic block 401 is approximately 0.1% of its total length, Δy and Δx have an approximately linear relationship: Δy / Δx = cotθ. At this point, the elongation Δl of the optical fiber 12 is calculated as follows: Δl = p(2πΔy + 4(Δx - Δy)), where p is the number of turns of the optical fiber 12 wrapped around the fiber stretcher 11, Δy is the displacement of the first amplifying plate 416 relative to the second amplifying plate 417 in the y-axis direction, and Δx is the elongation of the first piezoelectric ceramic block 401.

[0047] In the example of the present invention, the elongation of the first piezoelectric ceramic block 401 is 40μm, and the angle θ is 45 degrees. Therefore, the displacements of the first amplifier plate 416 and the second amplifier plate 417 are 40μm×cot45°=40μm respectively. At this time, it can be approximately considered that its diameter has increased by 40μm. The deformation of the fiber stretcher 11 will cause the optical fiber 12 wound on it to elongate. The elongation of the optical fiber 12 is Δl=hπΔx=2.5π×40μm=314.2μm, and the adjustment bandwidth reaches the order of 1kHz. To further adjust the optical path of the optical fiber 12 ring, it can be achieved by adjusting the light power entering the optical fiber 12 from the continuous light laser 16. When the power of the continuous light entering the optical fiber 12 increases, it will consume more pump light. As a result, the pulse in the optical fiber 12 obtains a smaller gain, thereby reducing the peak power of the pulse. The refractive index of the optical fiber 12 is related to the intensity (I) of the signal light: n f =n f0 +n2I, where n f0 Where n is the refractive index at low power, and n2 is the nonlinear coefficient of optical fiber 12, the optical path length can be reduced. Conversely, reducing the optical power entering optical fiber 12 increases the optical path length. This device achieves an optical path length adjustment range of the order of 1 μm, with an adjustment bandwidth of up to 100 kHz.

[0048] like Figure 3 As shown, the structure of the position-adjustable crystal cavity mirror 3 of the present invention is similar to that of the optical fiber stretcher 11, and mainly includes a coated crystal 31 and a position adjustment mechanism. The position adjustment mechanism can adjust the position of the coated crystal 31, thereby changing the laser cavity length. The position-adjustable crystal cavity mirror 3 includes a second piezoelectric ceramic block 301, which is a phase-shifting piezoelectric ceramic block; a first strain plate 302 and a second strain plate 303 symmetrically arranged along the y-axis, and the first strain plate 302 and the second strain plate 303 are T-shaped structures arranged opposite to each other; a first support plate 316 and a second support plate 317 symmetrically arranged along the x-axis, and the first support plate 316 and the second support plate 317 are trapezoidal structures arranged opposite to each other; a first connecting plate 308 arranged between the first strain plate 302 and the first support plate 316, and arranged A second connecting plate 309 is provided between the first supporting plate 316 and the second strain plate 303, a third connecting plate 310 is provided between the second strain plate 303 and the second supporting plate 317, and a fourth connecting plate 311 is provided between the second supporting plate 317 and the first strain plate 302; the second connecting plate 309 and the third connecting plate 310 are structurally symmetrical along the x-axis, and the first connecting plate 308 and the fourth connecting plate 311 are structurally symmetrical along the x-axis; the second connecting plate 309 and the first connecting plate 308 are structurally symmetrical along the y-axis, and the third connecting plate 310 and the fourth connecting plate 311 are structurally symmetrical along the y-axis.

[0049] The first strain plate 302 and the first connecting plate 308, the first connecting plate 308 and the first supporting plate 316, the first supporting plate 316 and the second connecting plate 309, the second connecting plate 309 and the second strain plate 303, the second strain plate 303 and the third connecting plate 310, the third connecting plate 310 and the second supporting plate 317, the second supporting plate 317 and the fourth connecting plate 311, and the fourth connecting plate 311 and the first strain plate 302 are connected by eight flexible pieces arranged along the X direction to form a rectangular parallelepiped with a rectangular groove therein. The length direction of the rectangular groove is the x-axis direction and the width direction is the y-axis direction. The coated crystal 31 is provided on the first supporting plate 316 or the second supporting plate 317. The second piezoelectric ceramic block 301 is arranged in the rectangular groove. The displacement generated by the second piezoelectric ceramic block 301 is transmitted to the first strain plate 302 and the second strain plate 303 respectively. The first strain plate 302 and the second strain plate 303 transmit the displacement to the first support plate 316 and the second support plate 317, so that the displacement of the coated crystal 31 changes, thereby achieving cavity length adjustment of the order of 10 μm and an adjustment bandwidth of the order of 10 kHz.

[0050] The present invention applies a control voltage across the coated crystal 31. When the control voltage is applied across the coated crystal 31, the lattice constant inside the coated crystal 31 changes due to the voltage, thereby changing the refractive index inside the crystal and thus changing the optical path inside the laser. When the voltage across the coated crystal 31 is several tens of volts, it is approximately assumed that the refractive index of the coated crystal 31 changes linearly with the internal electric field strength, that is, n c =n0 + aE, where n0 is the crystal's refractive index in the absence of an electric field, E is the electric field strength, and a is the constant corresponding to the primary electro-optic effect. When the crystal thickness reaches the millimeter level, cavity length adjustment on the order of 0.1 μm can be achieved. Due to the low parasitic capacitance within the crystal, a response bandwidth on the order of 10 MHz is easily achieved.

[0051] When the second piezoelectric ceramic block 301 is displaced, the first support plate 316 and the second support plate 317 move in a direction perpendicular to the extension of the second piezoelectric ceramic block 301 and displace in opposite directions. The displacement δy of each support plate relative to the second piezoelectric ceramic block 301 is mainly determined by Figure 3The angle γ in the equation is the angle between the line n connecting the center points of the flexible hinges at either end of any connecting plate and the extension direction m of the second piezoelectric ceramic block 301. Therefore, the flexible plates on both sides of the first connecting plate 308, the second connecting plate 309, the third connecting plate 310, and the fourth connecting plate 311 need to be staggered in the y-axis direction, that is, the first hinge 304 and the second hinge 305 are staggered in the y-axis direction. Since the displacement of the second piezoelectric ceramic block 301 is approximately 0.1% of its total length, δx and δy have an approximately linear relationship: δy / δx = 0.5cotγ. In this example, the extension of the second piezoelectric ceramic block 301 is 9μm, and the angle θ is 25 degrees. Therefore, the displacements of the first support plate 316 and the second support plate 317 are δy = 0.5×δx×cotγ = 0.5×9μm×cot25° = 19μm, which is also the displacement of the coated crystal 31.

[0052] In order to protect the second piezoelectric ceramic block 301 from being damaged by the reaction force generated by the first strain plate 302 and the second strain plate 303 during extension, a first bonding plate 320 and a second bonding plate 321 are inserted between the second piezoelectric ceramic block 301, the first strain plate 302 and the second strain plate 303 respectively. The first bonding plate 320 and the first strain plate 302 are connected by a first flexible plate 318, and the second bonding plate 321 and the second strain plate 303 are connected by a second flexible plate 319.

Claims

1. A delay-adjustable optical fiber ring, characterized by: It comprises an optical fiber stretcher (11), an optical fiber (12), a first phase shifter (13), a wavelength division multiplexer (14) and a polarization beam splitter (15); The optical fiber stretcher (11) is a cylindrical structure; the optical fiber (12) is wound on the side wall of the optical fiber stretcher (11); and its two ends are respectively connected to the first phase shifter (13) and the wavelength division multiplexer (14); the polarization beam splitter (15) is arranged at the output ends of the wavelength division multiplexer (14) and the first phase shifter (13), and the output ends of the wavelength division multiplexer (14) and the first phase shifter (13) are perpendicular to each other; The optical fiber stretcher (11) comprises a first piezoelectric ceramic block (401); A first force-bearing plate (402) and a second force-bearing plate (403) 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 arranged facing each other; A first connecting plate (408) is arranged between the first force-bearing plate (402) and the first amplifying plate (416); a second connecting plate (409) is arranged between the first force-bearing plate (402) and the second amplifying plate (417); a third connecting plate (410) is arranged between the second force-bearing plate (403) and the second amplifying plate (417); a fourth connecting plate (411) is arranged between the second 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; 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 first force-bearing plate (402), the first force-bearing 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 second force-bearing plate (403), the second 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 respectively connected to form a cylinder with a rectangular groove provided therein by eight flexible sheets arranged along the X direction, wherein the length direction of the rectangular groove is the x-axis direction and the width direction is the y-axis direction; The first piezoelectric ceramic block (401) is arranged in a rectangular groove, and the displacement generated by the first piezoelectric ceramic block (401) is transmitted to the first force-bearing plate (402) and the second force-bearing plate (403) respectively. The first force-bearing plate (402) and the second force-bearing plate (403) transmit the displacement to the first amplifying plate (416) and the second amplifying plate (417), so that the length of the optical fiber (12) wound on the optical fiber stretcher (11) changes.

2. The delay adjustable optical fiber ring according to claim 1, characterized in that: The elongation Δl of the optical fiber (12) is calculated as follows: Δl=p(2πΔy+4(Δx-Δy)) Δy=Δx·cotθ Wherein, p is the number of turns of the optical fiber (12) wound on the optical fiber stretcher (11), Δy is the displacement of the first amplifying plate (416) relative to the second amplifying plate (417) in the y-axis direction, Δx is the elongation of the first piezoelectric ceramic block (401), and θ is 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.

3. The delay adjustable optical fiber ring according to claim 1, characterized in that: It also includes a continuous light laser (16), which is arranged on one side of the incident surface of the polarization beam splitter (15), and the optical axis of the continuous light laser (16) is coaxial with the optical axis of the wavelength division multiplexer (14).

4. The delay adjustable optical fiber ring according to claim 1, wherein: A thread groove is provided on the side wall of the optical fiber stretcher (11), and the optical fiber (12) is wound around the optical fiber stretcher (11) through the thread groove.

5. The delay adjustable optical fiber ring according to claim 1, characterized in that: The optical fiber (12) includes a common transmission optical fiber and a gain optical fiber, the gain optical fiber is wound on the optical fiber stretcher (11), and the common transmission optical fiber is used to connect the gain optical fiber and the first phase shifter (13), and the gain optical fiber and the wavelength division multiplexer (14).

6. The delay adjustable optical fiber ring according to claim 1, characterized in that: A first gasket (418) and a second gasket (419) are respectively provided between the first piezoelectric ceramic block (401) and the first force-bearing plate (402) and the second force-bearing plate (403).

7. A frequency-adjustable crystal cavity mirror pulse laser, characterized in that: The invention comprises a polarization controller (2), a position-adjustable crystal cavity mirror (3), and a delay-adjustable optical fiber ring (1) according to any one of claims 1 to 6, wherein the delay-adjustable optical fiber ring (1), the polarization controller (2), and the position-adjustable crystal cavity mirror (3) are arranged in sequence; the polarization controller (2) comprises a wave plate (21), a second phase shifter (22), and a polarizer (23) which are arranged in sequence; The position-adjustable crystal cavity mirror (3) comprises a second piezoelectric ceramic block (301); A first strain plate (302) and a second strain plate (303) are symmetrically arranged along the y-axis, and the first strain plate (302) and the second strain plate (303) are T-shaped structures arranged facing each other; A first support plate (316) and a second support plate (317) are symmetrically arranged along the x-axis, and the first support plate (316) and the second support plate (317) are trapezoidal structures arranged facing each other; a first connecting plate (308) disposed between the first strain plate (302) and the first supporting plate (316), a second connecting plate (309) disposed between the first supporting plate (316) and the second strain plate (303), a third connecting plate (310) disposed between the second strain plate (303) and the second supporting plate (317), and a fourth connecting plate (311) disposed between the second supporting plate (317) and the first strain plate (302); The second connecting plate (309) and the third connecting plate (310) are structurally symmetrical along the x-axis, and the first connecting plate (308) and the fourth connecting plate (311) are structurally symmetrical along the x-axis; the second connecting plate (309) and the first connecting plate (308) are structurally symmetrical along the y-axis, and the third connecting plate (310) and the fourth connecting plate (311) are structurally symmetrical along the y-axis; The first strain plate (302) and the first connecting plate (308), the first connecting plate (308) and the first supporting plate (316), the first supporting plate (316) and the second connecting plate (309), the second connecting plate (309) and the second strain plate (303), the second strain plate (303) and the third connecting plate (310), the third connecting plate (310) and the second supporting plate (317), the second supporting plate (317) and the fourth connecting plate (311), and the fourth connecting plate (311) and the first strain plate (302) are connected to form a plate-like structure with a rectangular groove therein by eight flexible sheets arranged along the X direction, wherein the length direction of the rectangular groove is the x-axis direction and the width direction is the y-axis direction; A coated crystal (31) is provided on the first supporting plate (316) or the second supporting plate (317); The second piezoelectric ceramic block (301) is arranged in the rectangular groove, and the displacement generated by the second piezoelectric ceramic block (301) is transmitted to the first strain plate (302) and the second strain plate (303) respectively. The first strain plate (302) and the second strain plate (303) transmit the displacement to the first support plate (316) and the second support plate (317), so that the displacement of the coated crystal (31) changes.

8. The frequency-adjustable crystal cavity mirror pulse laser according to claim 7, characterized in that: The displacement δy of the coating crystal (31) is calculated as follows: δy=0.5×δx×cotγ Wherein, δx is the elongation of the second piezoelectric ceramic block (301), and γ is the angle between the line n connecting the hinge center points at both ends of any connecting plate and the elongation direction m of the second piezoelectric ceramic block (301).

9. The frequency-adjustable crystal cavity mirror pulse laser according to claim 8, characterized in that: A first bonding plate (320) and a second bonding plate (321) are respectively provided between the second piezoelectric ceramic block (301) and the first strain plate (302) and the second strain plate (303); the first bonding plate (320) and the first strain plate (302) are connected via a first flexible plate (318); and the second bonding plate (321) and the second strain plate (303) are connected via a second flexible plate (319).

10. The frequency-adjustable crystal cavity mirror pulse laser according to claim 9, characterized in that: The phase delay amount of the second phase shifter (22) is selected in a range of 0 to π, and the coating reflectivity of the coating crystal (31) is selected in a range of 0 to 99%.

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