Bidirectional pump amplifier, control method and laser

Abstract

This application discloses a bidirectional pump amplifier, a control method, and a laser, relating to the field of pump amplifier technology. The pump amplifier includes: a pump source for outputting pump light; a signal source for outputting signal light; an optical fiber disposed in the optical path of the signal light, used to amplify the signal light using the pump light, with unamplified signal light input at the first end and amplified signal light output at the second end; a beam splitter disposed in the optical path of the pump light, used to split the pump light into a first pump light and a second pump light, the first pump light being linearly polarized light transmitted from the beam splitter and the second pump light being linearly polarized light reflected by the beam splitter; and a reflection component disposed in the optical path of the first and second pump lights, used to reflect the first pump light to a first end and the second pump light to a second end, achieving a bidirectional pumping effect with a single pump source.

Description

Technical Field

[0001] This application relates to the field of pump amplifier technology, and in particular to a bidirectional pump amplifier, a control method, and a laser. Background Technology

[0002] Pump amplifiers are one of the core components commonly used in laser applications. They mainly amplify the power of signal light by utilizing the energy of pump light.

[0003] Existing signal light amplification methods include forward pumping, reverse pumping, and bidirectional pumping. Among them, bidirectional pumping combines the advantages of both forward and reverse pumping, offering higher signal-to-noise ratio and slope efficiency, more uniform temperature distribution, and effectively reducing mode instability effects. It is the preferred pumping method for achieving high-power amplification.

[0004] However, in practical applications, during bidirectional pumping, the optical fiber cannot completely absorb the pump light input from both directions, and the remaining pump light is continuously output to the opposite pump source, which leads to the instability of the pump source power. In severe cases, it may even fail. Therefore, bidirectional pumping accounts for a small proportion of the pumping methods used. Summary of the Invention

[0005] In view of the above-mentioned technical problems existing in the prior art, this application provides a bidirectional pump amplifier, a control method and a laser.

[0006] In one technical solution of this application, a bidirectional pump amplifier, a control method, and a laser are provided, comprising: a pump source for outputting pump light; a signal source for outputting signal light; an optical fiber disposed in the optical path of the signal light, the optical fiber being used to amplify the signal light using the pump light, a first end of the optical fiber receiving unamplified signal light, and a second end of the optical fiber outputting amplified signal light; a beam splitter disposed in the optical path of the pump light for splitting the pump light into a first pump light and a second pump light, the first pump light being linearly polarized light transmitted from the beam splitter, and the second pump light being linearly polarized light reflected by the beam splitter; and a reflection component disposed in the optical path of the first pump light and the second pump light for reflecting the first pump light to the first end and reflecting the second pump light to the second end.

[0007] In one technical solution of this application, the wavelength of the signal light and the wavelength of the pump light have a wavelength difference; the reflection component further includes a first dichroic mirror and a second dichroic mirror, the first dichroic mirror being disposed at the first end of the optical fiber for reflecting the first pump light to the first end; the second dichroic mirror being disposed at the second end of the optical fiber for reflecting the second pump light to the second end; both the first and second dichroic mirrors are disposed in the optical path of the signal light; the first end is also used to output a second residual light of the second pump light, and the second end is also used to output a first residual light of the first pump light. Based on the reflection component, the... The first residual light is collinear with the second pump light, and the second residual light is collinear with the first pump light. The reflecting component is further configured to reflect the first residual light in the reverse direction of the second pump light to the beam splitter, and to reflect the second residual light in the reverse direction of the first pump light to the beam splitter. The beam splitter is further configured to transmit the first residual light as a third residual light and reflect the second residual light as a fourth residual light. The fourth residual light has the same optical path as the third residual light. A light recovery device is provided along the optical path of the third residual light, and the input port of the light recovery device is configured corresponding to the optical path of the third residual light.

[0008] In one technical solution of this application, the reflective component further includes a first reflective component, which includes a first reflector disposed in the optical path of the first pump light and is used to reflect the first pump light to the first dichroic mirror; and a second reflective component, which includes a second reflector disposed in the optical path of the second pump light and is used to reflect the second pump light to the second dichroic mirror.

[0009] In one technical solution of this application, the first dichroic mirror and the second dichroic mirror have a wavelength transmittance of more than 90% for the signal light and a wavelength reflectance of more than 90% for the pump light.

[0010] In one technical solution of this application, a first aperture and a second aperture are provided in the optical path of the signal light. The first aperture is disposed between the signal light source and the first dichroic mirror to intercept the second residual light. The second aperture is disposed on the side of the second dichroic mirror away from the optical fiber to intercept the first residual light.

[0011] In one technical solution of this application, the pump light is linearly polarized light; it also includes a tunable waveplate, which is disposed between the pump source and the beam splitter. The tunable waveplate is used to adjust the ratio of the first pump light and the second pump light split by the beam splitter by adjusting the polarization direction of the pump light.

[0012] In one technical solution of this application, a power detection component is further included. The power detection component is disposed on the reflection component and is used to detect the power of the first pump light and / or the power of the second pump light. The tunable waveplate is equipped with a driving element, and the driving element is electrically connected to a control module. The control module is electrically connected to the power detection component and is used to control the driving element to rotate the tunable waveplate according to the detection result of the power detection component.

[0013] In one technical solution of this application, a lens assembly is further included, the lens assembly comprising: a first lens disposed between the first end and the first dichroic mirror for focusing the signal light and the first pump light, and collimating the second residual light; a second lens disposed between the second end and the second dichroic mirror for collimating the signal light and the first residual light, and focusing the second pump light; and a third lens disposed between the pump source and the tunable waveplate for collimating the pump light.

[0014] In one technical solution of this application, the optical fiber is a rod-shaped photonic crystal fiber, the fiber mode field diameter of the optical fiber is larger than the waist diameter of the signal light, the fiber core numerical aperture is larger than the numerical aperture of the signal light; the cladding diameter of the optical fiber is larger than the waist diameter of the pump light, and the cladding numerical aperture of the optical fiber is larger than the numerical aperture of the pump light.

[0015] In one technical solution of this application, a control method for a bidirectional pump amplifier is provided, comprising: sequentially turning on a signal source and a pump source, receiving and detecting the power of a second pump light, wherein the pump source is used to output linearly polarized pump light, a beam splitter is disposed in the optical path of the pump light, the beam splitter transmits part of the pump light as a first pump light and reflects part of the pump light as a second pump light; a reflection component is disposed in the optical path of the first pump light and the second pump light, the first pump light is reflected by the reflection component to a first end of an optical fiber, and the second pump light is reflected by the reflection component to a second end of an optical fiber, the optical fiber is disposed in the optical path of the signal light, the signal light is output by a signal source, and the power of the second pump light is detected by a power detection component disposed in the reflection component; and a target parameter of a rotating tunable waveplate is calculated according to the required power of the second pump light, wherein the required power of the second pump light is a preset value, and the tunable waveplate is disposed in the optical path of the pump source and the signal source is used to output linearly polarized pump light. Between the source and the beam splitter, the tunable waveplate is used to adjust the ratio of the first pump light and the second pump light split by the beam splitter by adjusting the polarization direction of the pump light. The tunable waveplate is equipped with a driving element, which is electrically connected to a control module. The control module is electrically connected to the power detection component. The control module is used to calculate the target parameters of the tunable waveplate based on the detection results of the power detection component; rotate the tunable waveplate according to the target parameters; detect that the power of the second pump light is equal to the required power of the second pump light; and complete the amplification of the signal light. The first end of the optical fiber inputs the unamplified signal light, and the second end of the optical fiber outputs the amplified signal light. The first pump light is input to the first end through the reflection component and is absorbed by the optical fiber. The second pump light is input to the second end through the reflection component and is absorbed by the optical fiber. At this time, the signal light is amplified through the optical fiber.

[0016] In one technical solution of this application, the method includes: collecting a first residual light of the first pump light and a second residual light of the second pump light, wherein the first residual light is the first pump light remaining after absorption by the optical fiber, and the second residual light is the second pump light remaining after absorption by the optical fiber; the second residual light is output from the first end, passes through a first dichroic mirror disposed at the first end of the optical fiber, and is reflected in the reverse direction of the optical path of the first pump light to the beam splitter; the first residual light is output from the second end, passes through a second dichroic mirror disposed at the second end of the optical fiber, and is reflected in the reverse direction of the optical path of the second pump light to the beam splitter; the beam splitter is further used to transmit the first residual light as a third residual light and reflect the second residual light as a fourth residual light, and collects the third residual light and the fourth residual light through a light recovery device disposed along the optical path of the third residual light.

[0017] In one technical solution of this application, a laser is provided, which has a bidirectional pump amplifier as described in any of the above technical solutions, and is configured to perform the control method as described in any of the above technical solutions.

[0018] The beneficial effects of this invention include: solving the problem of unstable pump source power caused by the impact of unabsorbed residual pump light on the bidirectional pump source in the prior art; achieving bidirectional pumping effect with a single pump source; and reducing structural costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a specific embodiment of the bidirectional pump amplifier of this application;

[0020] Figure 2 This is a flowchart of the bidirectional pump amplifier control method of this application;

[0021] Figure 3 This is a flowchart of the method for adjusting the power ratio of horizontal and vertical polarization pump light in this application;

[0022] 1. Pump source; 2. Signal light source; 3. Optical fiber; 4. Beam splitter; 5. Reflection assembly; 51. First dichroic mirror; 52. Second dichroic mirror; 53. First reflection assembly; 531. First reflector; 54. Second reflection assembly; 541. Second reflector; 6. Light recovery device; 7. First aperture; 8. Second aperture; 9. Adjustable waveplate; 10. Power detection assembly; 11. Control module; 12. Lens assembly; 121. First lens; 122. Second lens; 123. Third lens. Detailed Implementation

[0023] The preferred embodiments of this application will now be described in detail with reference to the accompanying drawings, so that the advantages and features of this application can be more easily understood by those skilled in the art, thereby providing a clearer and more definite definition of the scope of protection of this application.

[0024] It should be noted that the terms "first," "second," and "third" in the claims and description of this application are used only to distinguish similar objects and should not be construed as describing a specific order or sequence.

[0025] A pump amplifier can amplify signal light using pump light within fiber 3. However, the fiber cannot guarantee that the input pump light will be 100% absorbed, and the unabsorbed residual pump light will continue to propagate along the input direction. In a common bidirectional pump structure, a pump source 1 is set at the first and second ends of fiber 3. Pump sources 1 input two opposing pump lights into fiber 3 from the first and second ends. The two pump lights are absorbed by fiber 3 and amplify the signal light near the first and second ends respectively, thus achieving a preferred pumping method for high-power amplification with both high signal-to-noise ratio and slope efficiency, and a more uniform temperature distribution within fiber 3. However, the corresponding unabsorbed residual pump light is input into the opposing pump sources 1, and the pump sources 1 at both ends are impacted, disrupting the stability of their output power and affecting the amplification effect on the signal light.

[0026] Figure 1 A schematic diagram of a specific embodiment of a bidirectional pump amplifier is shown.

[0027] In one specific embodiment of the present invention, such as Figure 1 As shown, this invention illustrates a pump amplifier that achieves bidirectional pumping via a single pump source 1. The pump source 1 outputs pump light, and the signal source 2 outputs signal light. An optical fiber 3 is positioned along the optical path of the signal light. The first end and the second end of the optical fiber 3 correspond to its two ends, respectively. The signal light is input to the first end of the optical fiber 3, where it is amplified by the pump light. The amplified signal light is then output through the second end of the optical fiber 3.

[0028] Pump source 1 is used to output pump light. A beam splitter 4 is set in the optical path of the pump light, which can split the pump light into a first pump light and a second pump light. The first pump light is linearly polarized light transmitted from the beam splitter 4, and the second pump light is linearly polarized light reflected by the beam splitter 4. A reflection component 5 is set in the optical path of the split first pump light and the second pump light. The reflection component 5 reflects the first pump light to the first end of the optical fiber 3 and inputs it into the optical fiber 3 at the same end as the signal light. The reflection component 5 reflects the second pump light to the second end of the optical fiber 3 and inputs it into the optical fiber 3 from the second end.

[0029] The beam splitter 4 divides the single pump light emitted from pump source 1 into a first pump light and a second pump light. This achieves the technical requirement of two pump sources each emitting a single pump light in a bidirectional pumping structure, in terms of the number of pump lights. However, considering the quality of the pump light, the sum of the power of the first pump light emitted from pump source 1 and the power of the second pump light is generally less than the sum of the power of the two pump lights output from two pump sources of equal power.

[0030] For high pump power requirements, a higher-power pump source can be selected, or multiple pump sources can be combined into a single pump source for output. In this case, the higher-power pump light is split into a first pump light and a second pump light. The power of the first and second pump lights can compensate for the lower power output of a single pump source 1. It should be noted that combining multiple sub-pump sources into a single pump source 1 is a common method to increase pump source power. Compared to directly using two sub-pump sources, a single pump source 1 has the advantages of saving pump source installation space and time, and optimizing installation steps and spatial layout.

[0031] According to this embodiment, the present invention can achieve bidirectional pump amplification of signal light through a separate pump source 1. The separate pump source 1 has lower cost and is simpler to control than common bidirectional pump structures.

[0032] The first pump light and the second pump light are reflected by the reflector 5. The first pump light is linearly polarized light transmitted from the beam splitter 4, and its propagation direction is the same as before the pump light is split. The second pump light is linearly polarized light reflected by the beam splitter 4, and its propagation direction forms an angle with the propagation direction of the first pump light, which is less than 180 degrees.

[0033] For the first pump light, the reflecting component 5 reflects the first pump light to the first end of the optical fiber 3 through at least one reflection, and the first pump light enters the optical fiber 3 from the first end. For the second pump light, the reflecting component 5 reflects the second pump light to the second end of the optical fiber 3 through at least one reflection, and the second pump light enters the optical fiber 3 from the second end.

[0034] Because the cladding numerical aperture of fiber 3 is relatively large, the reflecting component 5 does not need to reflect the first pump light so that it is collinear with the optical path of the signal light. Instead, it reflects the first pump light to the first end of fiber 3, provided that there is a certain angular deviation between the optical paths of the first pump light and the signal light. Similarly, it does not need to reflect the second pump light so that it is collinear with the optical path of the signal light; instead, it reflects the second pump light to the second end of fiber 3, provided that there is a certain angular deviation between the optical paths of the second pump light and the signal light. This allowable deviation angle depends on the specific numerical aperture of the fiber cladding and the numerical aperture of the pump light.

[0035] In a specific embodiment of the present invention, the beam splitter 4 specifically includes a polarization beamsplitter (PBS). The polarization beamsplitter comprises two cemented right-angle prisms, with a polarizing beam-splitting film coated on their cemented inclined surfaces. The pump light emitted from the pump source 1 forms a 45-degree angle with the cemented inclined surfaces and is split into a first pump light and a second pump light by the beam splitter 4. The first pump light is a horizontal pump light, and the second pump light is a vertical pump light, with an exit angle of 90 degrees between the first and second pump lights.

[0036] In one specific embodiment of the present invention, the wavelength of the signal light and the wavelength of the pump light have a wavelength difference. The reflecting component 5 further includes a first dichroic mirror 51 and a second dichroic mirror 52, both of which are disposed in the optical path of the signal light. The first dichroic mirror 51 is disposed at the first end of the optical fiber 3 and is used to reflect the first pump light to the first end. The second dichroic mirror 52 is disposed at the second end of the optical fiber 3 and is used to reflect the second pump light to the second end.

[0037] A dichroic mirror is an optical element that selectively transmits or reflects light at specific wavelengths. The first dichroic mirror 51 and the second dichroic mirror 52, serving as reflective components 5, exhibit high reflectivity for the pump light wavelength and high transmittance for the signal light wavelength. This allows the first dichroic mirror 51 and the second dichroic mirror 52 to transmit the signal light and reflect the pump light.

[0038] In one specific embodiment of the present invention, the transmittance of the first dichroic mirror 51 and the second dichroic mirror 52 to the wavelength of the signal light is greater than 90%. The transmittance value specified in this embodiment is the minimum transmittance value. In actual production, the transmittance of the first dichroic mirror 51 and the second dichroic mirror 52 to the wavelength of the signal light is usually above 95%.

[0039] Similarly, the first dichroic mirror 51 and the second dichroic mirror 52 have a wavelength reflectivity of more than 90% for the pump light. This is also the lowest reflectivity value for the wavelength reflectivity of the pump light. In actual production, the wavelength reflectivity of the pump light is usually above 95%.

[0040] The selection of signal and pump light wavelengths depends on the type of rare-earth ions doped in the gain fiber. Different rare-earth ions have specific absorption and emission spectra. The absorption spectrum determines the available pump light wavelength, while the emission spectrum determines the available signal light wavelength. For example, ytterbium-doped fibers are mostly used in industrial fiber lasers. Ytterbium ions have two absorption peaks in their absorption spectrum, located at 915 nm and 976 nm, respectively. Therefore, pump wavelengths of 915 nm and 976 nm are mostly used. Other wavelengths near the absorption peaks can also be used as pump light, but with relatively lower efficiency. The emission spectrum of ytterbium ions is from 1000 to 1200 nm. The laser wavelength of pulsed lasers is generally 1064 nm, while the wavelength of continuous-wave lasers is in the range of 1070 to 1080 nm.

[0041] Both the first dichroic mirror 51 and the second dichroic mirror 52 are placed in the optical path of the signal light, reflecting the first pump light to the first end and the second pump light to the second end. When the first pump light is reflected by the first dichroic mirror 51 to the first end and the second pump light is reflected by the second dichroic mirror 52 to the second end, the optical paths of the first pump light, the second pump light and the signal light are collinear. In other words, without considering the propagation direction, the optical paths of the first pump light, the second pump light and the signal light share the same optical path.

[0042] It is known that fiber optic cable 3 is configured according to the optical path of the signal light, and the end faces of fiber optic cable 3 are perpendicular to the propagation direction of the signal light. Similarly, in this embodiment, when the first pump light and the second pump light are input through the first and second ends of fiber optic cable 3, their incident directions are perpendicular to the end faces of the first and second ends, respectively. Maintaining an input angle perpendicular to the end faces of fiber optic cable 3 ensures the input accuracy of the first and second pump lights and improves input efficiency.

[0043] To avoid a decrease in stability caused by the impact of unabsorbed residual pump light on the pump source, in one specific embodiment of the present invention, the remaining portion of the first pump light not absorbed by the optical fiber 3 forms first residual light. The first residual light continues to propagate along the direction of the first pump light and is output from the second end of the optical fiber 3. Similarly, the remaining portion of the second pump light not absorbed by the optical fiber 3 forms second residual light, which continues to propagate along the direction of the second pump light and is output from the first end of the optical fiber 3.

[0044] Since the first pump light and the second pump light are collinear and in opposite directions at the first and second ends of the input fiber 3, the first residual light and the second residual light are also collinear and in opposite directions at the second and first ends of the output fiber 3. Because the optical path is reversible, the first residual light travels in reverse along the optical path of the second pump light, is reflected by the reflecting component 5, and reaches the beam splitter 4. Similarly, the second residual light travels in reverse along the optical path of the first pump light, is reflected by the reflecting component 5, and reaches the beam splitter 4.

[0045] Beam splitter 4 is also used to transmit the first residual light into a third residual light and reflect the second residual light into a fourth residual light, the fourth residual light having the same optical path as the third residual light. A light-gathering device 6 is arranged along the optical path of the third residual light, with its input port corresponding to the optical path of the third residual light. The first residual light and the first pump light are both pump lights transmitted by beam splitter 4, and the second residual light and the second pump light are both pump lights reflected by beam splitter 4. That is, beam splitter 4 transmits the first residual light and the pump light belonging to the first pump light twice, and reflects the second residual light and the pump light belonging to the second pump light twice.

[0046] The first residual light is reflected to beam splitter 4 through the reverse path of the second pump light, and the second residual light is reflected to beam splitter 4 through the reverse path of the first pump light. The first and second pump lights are obtained by splitting the same pump light by beam splitter 4. Therefore, when beam splitter 4 transmits the first residual light and reflects the second residual light, the optical paths of the third residual light formed by the first residual light and the fourth residual light formed by the second residual light are the same.

[0047] For the third and fourth residual light, the light recovery device 6 is set in the optical path of the third residual light, and the input port of the light recovery device 6 is directly facing the optical path of the third residual light. The third and fourth residual light can be input into the light recovery device 6 through the input port of the light recovery device 6.

[0048] In one embodiment of the present invention, the light recovery device 6 includes an extinction cylinder, which is configured as a hollow conical barrel with a rough surface due to frosting or etching treatment inside. The third and fourth residual light are collected at one end of the extinction cylinder and diffusely reflected inside the cylinder, eventually being completely absorbed.

[0049] In another optional embodiment of the present invention, the extinction tube can be any one of a beam collector, a beam collector, or a beam catcher.

[0050] In one specific embodiment of the present invention, the reflecting component 5 further includes a first reflecting component 53 and a second reflecting component 54. The first reflecting component 53 includes a first reflecting mirror 531, which includes two reflecting mirrors. The first reflecting mirror 531 controls the reflection of the first pump light to the first dichroic mirror 51 by reflecting the first pump light twice, thereby enabling the first pump light to enter the first end of the optical fiber 3 through a collinear optical path with the second pump light.

[0051] Similarly, the second reflective component 54 includes a second reflector 541, which comprises two reflectors. The second reflector 541 controls the reflection of the second pump light to the second dichroic mirror 52 by reflecting the second pump light twice, thereby enabling the second pump light to enter the second end of the optical fiber 3 in a collinear optical path with the first pump light.

[0052] In this embodiment, the first pump light is controlled by the first reflection component 53, and the second pump light is controlled by the second reflection component 54. The two controls are separated, reducing the correlation between the components and thus reducing the difficulty of arrangement and maintenance.

[0053] In one specific embodiment of the present invention, a first aperture 7 and a second aperture 8 are provided in the optical path of the signal light. The first aperture 7 is disposed between the signal light source 2 and the first dichroic mirror 51 to intercept the second residual light. The second aperture 8 is disposed on the side of the second dichroic mirror 52 away from the optical fiber 3 to intercept the first residual light.

[0054] The first and second residual light are both emitted by pump source 1, therefore their wavelengths are the same as the pump light emitted by the pump source. Although the first dichroic mirror 51 and the second dichroic mirror 52 have a minimum reflectivity of more than 90% for the pump light wavelength, some of the first and second residual light still pass through the second dichroic mirror 52 or the first dichroic mirror 51. The second residual light passes through the first dichroic mirror 51 and propagates towards the signal light source 2, while the first residual light passes through the second dichroic mirror 52 and propagates in the same direction as the signal light.

[0055] When the signal light source is subjected to the input of the second residual light, the power stability of its output signal light decreases, and it may even cause the signal light source to fail. Furthermore, the wavelength and beam quality of the first residual light differ from those of the signal light, affecting subsequent components and leading to decreased system stability. The spots of the first and second residual lights are much larger than the spot of the signal light. By setting a suitable second aperture 8 and a first aperture 7, the signal light can pass through completely, while most of the first and second residual lights are blocked. In a specific embodiment of the present invention, the spot diameter of the signal light is 1 mm, while the spot diameter of the pump light is 10 mm, and the aperture diameter is set to 2 mm.

[0056] In one specific embodiment of the present invention, the pump light is linearly polarized light. It also includes a tunable waveplate 9, which is disposed between the pump source 1 and the beam splitter 4. The tunable waveplate 9 is used to adjust the ratio of the first pump light and the second pump light split by the beam splitter 4 by adjusting the polarization direction of the pump light.

[0057] For signal light of different power and frequency, there exists an optimal power ratio between the first pump light and the second pump light during the amplification process via fiber 3, thereby obtaining optimal amplification power and nonlinear suppression. However, since the polarization direction of the pump light is determined by the output of pump source 1, the power ratio of the first pump light and the second pump light formed by the beam splitter 4 under a fixed polarization direction is also fixed, and it cannot continuously maintain the optimal ratio for signal light of different power or frequency.

[0058] The tunable waveplate 9 is an optical element utilizing the principle of birefringence. The tunable waveplate 9 has different refractive indices in two mutually perpendicular directions, with the smaller refractive index on the fast axis and the larger refractive index on the slow axis. Linearly polarized light has a fixed vibration direction. When linearly polarized light enters the waveplate, it is decomposed along both the fast and slow axes. The two decomposed components have a fixed phase relationship, determined by the angle between the polarization direction of the linearly polarized light and the fast axis of the waveplate. By rotating this angle, the polarization direction of the pump light can be adjusted, thereby adjusting the ratio of the first and second pump lights split by the beam splitter 4.

[0059] In this embodiment, the adjustable waveplate 9 is specifically a half-wave plate. The half-wave plate has continuous adjustability. By rotating the half-wave plate itself, for example by a motor, the polarization direction of the pump light can be changed continuously and smoothly, thereby improving the flexibility of the pump light adjustment method.

[0060] In one specific embodiment of the present invention, a lens assembly 12 is further included for collimating or focusing the input light. The lens assembly 12 includes: a first lens 121 disposed between a first end and a first dichroic mirror 51, used to focus the signal light and the first pump light, while simultaneously collimating the second residual light; a second lens 122 disposed between a second end and a second dichroic mirror 52, used to collimate the signal light and the first residual light, while simultaneously focusing the second pump light; and a third lens 123 disposed between the pump source 1 and the tunable waveplate 9, used to collimate the pump light.

[0061] The first lens 121 and the second lens 122 need to simultaneously focus the signal light and pump light incident on the optical fiber 3, and collimate the signal light and pump light exiting the optical fiber 3. To ensure good collimation for different wavelengths and avoid chromatic aberration that could cause the light spot to enlarge or shift in position, the first lens 121 and the second lens 122 have an achromatic design. Furthermore, because the pump light power required for collimation and / or focusing by the first lens 121, the second lens 122, and the third lens 123 is very high, the first lens 121, the second lens 122, and the third lens 123 are made of high-quality materials, such as fused silica, and are coated with high-damage-threshold antireflective coatings on both sides.

[0062] In one specific embodiment of the present invention, the optical fiber 3 is a rod-shaped photonic crystal fiber, the fiber mode field diameter of the optical fiber 3 is larger than the waist diameter of the signal light, the core numerical aperture of the optical fiber 3 is larger than the numerical aperture of the signal light, the cladding diameter of the optical fiber 3 is larger than the waist diameter of the pump light, and the cladding numerical aperture of the optical fiber 3 is larger than the numerical aperture of the pump light.

[0063] The fiber mode field diameter of fiber 3 refers to the size of the transverse distribution of light in the fiber, while the beam waist diameter of the signal light refers to the diameter of the narrowest point of the signal light propagation path, which is the location where the signal light energy is most concentrated. Setting the fiber mode field diameter of fiber 3 to be larger than the beam waist diameter of the signal light, and aligning the beam waist diameter of the signal light with the end face of the first end, can achieve higher coupling efficiency.

[0064] The numerical aperture of fiber 3 refers to the maximum angle at which the fiber receives signal light, while the numerical aperture of the signal light refers to the divergence angle after leaving the fiber waist. The numerical aperture of fiber 3 must be larger than the numerical aperture of the signal light; otherwise, some signal light will not be able to couple into fiber 3.

[0065] The waist diameter of the pump light refers to the diameter of the pump light at the narrowest point in its propagation path. The cladding diameter of fiber 3 is larger than the waist diameter of the pump light to ensure that all focused pump light can be coupled into fiber 3.

[0066] The cladding numerical aperture of fiber 3 refers to the maximum angle at which the fiber receives pump light, while the numerical aperture of the pump light refers to the divergence angle after leaving the beam waist. The cladding numerical aperture of fiber 3 must be greater than the numerical aperture of the pump light to ensure that the pump light is within the maximum receiving angle of fiber 3.

[0067] like Figure 2 As shown, in a specific embodiment of the present invention, a control method for a bidirectional pump amplifier is disclosed. The first step is to sequentially turn on the signal light source 2 and the pump source 1, and detect the power of the second pump light.

[0068] Pump source 1 outputs linearly polarized pump light. Beam splitter 4 transmits a portion of the pump light as the first pump light and reflects a portion as the second pump light. The first and second pump lights are reflected by reflection components 5 located in the optical paths of the first and second pump lights to the first and second ends of optical fiber 3, respectively. Optical fiber 3 is located in the optical path of the signal light, which is output by signal source 2. The power of the second pump light is detected by power detection component 10 located in reflection component 5.

[0069] Step 2: Calculate the target parameters of the rotating tunable waveplate 9 based on the required power of the second pump light.

[0070] The required power of the second pump light is a preset value, and the tunable waveplate 9 is positioned between the pump source 1 and the beam splitter 4. The tunable waveplate 9 is used to adjust the ratio of the first pump light and the second pump light split by the beam splitter 4 by adjusting the polarization direction of the pump light. The tunable waveplate 9 is equipped with a driving element, which is electrically connected to a control module 11, which is electrically connected to a power detection component 10. The control module 11 is used to calculate the target parameters of the rotating tunable waveplate 9 based on the detection results of the power detection component 10.

[0071] Step 3: Rotate the adjustable waveplate 9 according to the target parameters until the detected second pump light power is equal to the required second pump light power.

[0072] Step 4: Amplify the signal light.

[0073] Unamplified signal light is input at the first end of fiber 3, and amplified signal light is output at the second end of fiber 3. A first pump light is input to the first end through reflector 5 and is absorbed by fiber 3. A second pump light is input to the second end through reflector 5 and is absorbed by fiber 3. At this time, the signal light is amplified through fiber 3.

[0074] In one specific embodiment of the present invention, a first residual light of a first pump light and a second residual light of a second pump light are collected.

[0075] The first residual light is the first pump light remaining after absorption by fiber 3, and the second residual light is the second pump light remaining after absorption by fiber 3. The first residual light is output from the second end, and the second residual light is output from the first end. The second residual light is reflected in the reverse direction to beam splitter 4 via a first dichroic mirror 51 located at the first end of fiber 3, following the optical path of the first pump light. Similarly, the first residual light is reflected in the reverse direction to beam splitter 4 via a second dichroic mirror 52 located at the second end of fiber 3, following the optical path of the second pump light. Beam splitter 4 is also used to transmit the first residual light as a third residual light and reflect the second residual light as a fourth residual light. The third and fourth residual lights are collected by a light-gathering device 6 located along the optical path of the third residual light.

[0076] In one specific embodiment of the present invention, a laser is provided having a bidirectional pump amplifier as described in any of the above embodiments.

[0077] In one optional embodiment of the present invention, the signal light is linearly polarized collimated light with a spot diameter of 0.8 mm, a center wavelength of 1030 nm, a power of 300 mW, a pulse width of 500 ps, ​​a spectral width of 8 nm, and a repetition rate of 1 MHz. These parameters are only those used in this embodiment; other parameters may also be selected.

[0078] The first dichroic mirror 51 and the second dichroic mirror 52 have high transmittance for 1030nm signal light and high reflectivity for 976nm pump light.

[0079] The first lens 121 focuses the signal light and the horizontally polarized pump light, while collimating the residual vertically polarized pump light. In this embodiment, the focal length of the first lens 121 is 30mm. After the signal light is focused, its waist diameter and numerical aperture are both smaller than the mode field diameter and core numerical aperture of the rod-shaped photonic crystal fiber 3, ensuring that the signal light is coupled into the core of the rod-shaped photonic crystal fiber 3. After the horizontally polarized pump light is focused, its waist diameter and numerical aperture are both smaller than the cladding diameter and cladding numerical aperture of the rod-shaped photonic crystal fiber 3, ensuring that the pump light is coupled into the cladding of the rod-shaped photonic crystal fiber 3.

[0080] The rod-shaped photonic crystal fiber 3 serves as the gain medium, with a length of 80 cm, a core diameter of 85 μm, a core numerical aperture of 0.015, a mode field diameter of 65 μm, a cladding diameter of 260 μm, and a cladding numerical aperture of 0.5.

[0081] The function of the second lens 122 is to collimate and amplify the signal light and the residual horizontally polarized pump light, while simultaneously focusing the vertically polarized pump light. In this embodiment, the focal length of the second lens is 30mm. After the vertically polarized pump light is focused, its beam waist diameter and numerical aperture are both smaller than the cladding diameter and cladding numerical aperture of the rod-shaped photonic crystal fiber 3, ensuring that the pump light is coupled to the cladding of the rod-shaped photonic crystal fiber 3.

[0082] Pump source 1 outputs linearly polarized light with a power of 450W, a center wavelength of 976nm, and a numerical aperture of 0.2. Pump source 1 can also be composed of several sub-pump sources combined into one.

[0083] The function of the third lens 123 is to collimate the pump light output from the pump source 1. In this embodiment, the focal length of the third lens 123 is 30mm.

[0084] Adjustable waveplate 9 is used to adjust the polarization direction of the pump light. The waveplate is a half-waveplate with a wavelength of 976nm, and its rotation angle is adjusted by a motor.

[0085] Beam splitter 4 serves two purposes. First, it splits the pump light into two beams: horizontally polarized and vertically polarized. The horizontally polarized light passes through beam splitter 4, while the vertically polarized light is reflected at a 90° angle. Second, it prevents residual pump light from entering pump source 1. Residual horizontally polarized pump light passes through beam splitter 4 and enters light recovery device 6, while residual vertically polarized pump light is reflected at a 90° angle and then enters light recovery device 6. In this embodiment, beam splitter 4 is a polarization beam-splitting cube with a working wavelength of 620~1000nm and a side length of 25.4mm.

[0086] The light recovery device 6 is used to collect residual pump light.

[0087] The first aperture 7, with a diameter of 2mm, is used to block the residual vertically polarized pump light transmitted through the first dichroic mirror 51, thus protecting the seed source. The second aperture 8, with a diameter of 2mm, is used to block the residual horizontally polarized pump light transmitted through the second dichroic mirror 52.

[0088] The power detection component 10 is used to detect the vertically polarized pump light transmitted through the second reflector 541, thereby determining the power of the vertically polarized pump light.

[0089] The control module 11 is used to receive the detection results of the power detection component 10 and drive the motor of the adjustable waveplate 9, thereby achieving a specific horizontal / vertical polarization pump light power ratio.

[0090] In an optional embodiment of the present invention, a specific amplification process of a bidirectional pump amplifier is disclosed, including: Signal light path: After passing through a first dichroic mirror 51, it is focused by a first lens 121 onto the core of a rod-shaped photonic crystal fiber 3, where it is amplified by combining with pump light within the rod-shaped photonic crystal fiber 3. The amplified signal light is collimated by a second lens 122 and then output through a second dichroic mirror 52.

[0091] The optical path of the pump light: The linearly polarized pump light output from pump source 1 is collimated by the third lens 123 and its polarization direction is changed by the adjustable waveplate 9 before entering the beam splitter 4. The beam splitter 4 splits the pump light into two beams of polarized light, one horizontally polarized and the other vertically polarized.

[0092] The horizontally polarized pump light path: After passing through beam splitter 4, it is reflected sequentially by first reflector 531, first dichroic mirror 51, and focused by first lens 121, and then coupled into the cladding of rod-shaped photonic crystal fiber 3. The residual horizontally polarized pump light that is not absorbed by rod-shaped photonic crystal fiber 3 is collimated by second lens 122, and then reflected sequentially by second dichroic mirror 52 and second reflector 541 before entering beam splitter 4. After passing through beam splitter 4, it finally enters light recovery device 6.

[0093] The vertically polarized pump light path: reflected by beam splitter 4, then reflected sequentially by second mirror 541, second dichroic mirror 52, and focused by second lens 122, is coupled into the cladding of rod-shaped photonic crystal fiber 3. The residual vertically polarized pump light not absorbed by rod-shaped photonic crystal fiber 3 is collimated by first lens 121, then reflected sequentially by first dichroic mirror 51 and first mirror 531 into beam splitter 4, and finally reflected by beam splitter 4 into light recovery device 6.

[0094] like Figure 3 As shown, the automatic adjustment method for the power ratio of horizontal and vertical polarization pump light includes:

[0095] S301: Determine the P / I curve of pump current versus pump source 1 output power.

[0096] S302: Under a specific pump current, the control module 11 drives the adjustable waveplate 9 to slowly rotate 1 / 4 turn, and records the maximum value P detected by the power detection component 10. max P max The corresponding pump output power P0 under this pump current.

[0097] S303: Input the required power ratio 'a' between the horizontally polarized pump light and the vertically polarized pump light. The software calculates the value P that the power detection component 10 needs to detect: P=P max / (a+1).

[0098] S304: Control module 11 drives the adjustable waveplate 9 to rotate slowly until the power detection component measures a value of P. At this time, the power ratio of the horizontally polarized pump light to the vertically polarized pump light is a, and the power of the vertically polarized pump light is P2 = P0 * P / P. max The horizontally polarized pump light power P1 = P0 - P2.

[0099] In another optional embodiment of the present invention, a laser is provided having the bidirectional pump amplifier described in any of the above embodiments, and in combination with the method described in any of the above embodiments, to achieve high-power amplification of the signal light.

[0100] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0101] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0102] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A bidirectional pump amplifier, characterized in that, include: Pump source (1) is used to output pump light; Signal light source (2), used to output signal light; An optical fiber (3) is disposed in the optical path of the signal light. The optical fiber (3) is used to amplify the signal light using the pump light. The first end of the optical fiber (3) receives the unamplified signal light, and the second end of the optical fiber (3) outputs the amplified signal light. A beam splitter (4) is disposed in the optical path of the pump light to split the pump light into a first pump light and a second pump light. The first pump light is linearly polarized light transmitted from the beam splitter (4), and the second pump light is linearly polarized light reflected by the beam splitter (4). A reflective component (5) is disposed in the optical path of the first pump light and the second pump light, for reflecting the first pump light to the first end and reflecting the second pump light to the second end; The wavelength of the signal light has a wavelength difference from that of the pump light; The reflective component (5) further includes a first dichroic mirror (51) and a second dichroic mirror (52). The first dichroic mirror (51) is disposed at the first end of the optical fiber (3) and is used to reflect the first pump light to the first end. The second dichroic mirror (52) is disposed at the second end of the optical fiber (3) and is used to reflect the second pump light to the second end. Both the first dichroic mirror (51) and the second dichroic mirror (52) are disposed in the optical path of the signal light. The first end is also used to output the second residual light of the second pump light, and the second end is also used to output the first residual light of the first pump light. Based on the reflection component (5), the first residual light is collinear with the second pump light, and the second residual light is collinear with the first pump light. The reflection component (5) is also used to reflect the first residual light in the reverse direction of the optical path of the second pump light to the beam splitter (4), and to reflect the second residual light in the reverse direction of the optical path of the first pump light to the beam splitter (4). The beam splitter (4) is also used to transmit the first residual light as the third residual light and reflect the second residual light as the fourth residual light. The fourth residual light has the same optical path as the third residual light. A light recovery device (6) is provided along the optical path of the third residual light. The input port of the light recovery device (6) is provided corresponding to the optical path of the third residual light.

2. The bidirectional pump amplifier according to claim 1, characterized in that, The reflective component (5) further includes a first reflective component (53), which includes a first reflector (531). The first reflector (531) is disposed in the optical path of the first pump light and is used to reflect the first pump light to the first dichroic mirror (51). The second reflective component (54) includes a second reflector (541), which is disposed in the optical path of the second pump light and is used to reflect the second pump light to the second dichroic mirror (52).

3. The bidirectional pump amplifier according to claim 1, characterized in that, The first dichroic mirror (51) and the second dichroic mirror (52) have a wavelength transmittance of more than 90% for the signal light, and the first dichroic mirror (51) and the second dichroic mirror (52) have a wavelength reflectance of more than 90% for the pump light.

4. The bidirectional pump amplifier according to claim 1, characterized in that, A first aperture (7) and a second aperture (8) are provided in the optical path of the signal light. The first aperture (7) is located between the signal light source (2) and the first dichroic mirror (51) to intercept the second residual light. The second aperture (8) is located on the side of the second dichroic mirror (52) away from the optical fiber (3) to intercept the first residual light.

5. The bidirectional pump amplifier according to claim 1, characterized in that, The pump light is linearly polarized light; It also includes a tunable waveplate (9), which is disposed between the pump source (1) and the beam splitter (4). The tunable waveplate (9) is used to adjust the ratio of the first pump light and the second pump light split by the beam splitter (4) by adjusting the polarization direction of the pump light.

6. The bidirectional pump amplifier according to claim 5, characterized in that, It also includes a power detection component (10), which is disposed on the reflection component (5) for detecting the power of the first pump light and / or the power of the second pump light; The adjustable waveplate (9) is equipped with a driving element, which is electrically connected to a control module (11). The control module (11) is electrically connected to the power detection component (10). The control module (11) is used to control the driving element to rotate the adjustable waveplate (9) according to the detection result of the power detection component (10).

7. The bidirectional pump amplifier according to claim 5, characterized in that, It also includes a lens assembly (12), which includes: a first lens (121) disposed between the first end and the first dichroic mirror (51) for focusing the signal light and the first pump light and collimating the second residual light; The second lens (122) is disposed between the second end and the second dichroic mirror (52) for collimating the signal light and the first residual light and focusing the second pump light; A third lens (123) is disposed between the pump source (1) and the tunable waveplate (9) for collimating the pump light.

8. The bidirectional pump amplifier according to claim 1, characterized in that, The optical fiber (3) is a rod-shaped photonic crystal fiber. The fiber mode field diameter of the optical fiber (3) is larger than the waist diameter of the signal light, and the core numerical aperture of the optical fiber (3) is larger than the numerical aperture of the signal light. The cladding diameter of the optical fiber (3) is larger than the waist diameter of the pump light, and the numerical aperture of the cladding of the optical fiber (3) is larger than the numerical aperture of the pump light.

9. A control method for a bidirectional pump amplifier, characterized in that, include: The signal light source (2) and pump source (1) are turned on in sequence, and the power of the second pump light is detected. Wherein, the pump source (1) is used to output linearly polarized pump light; a beam splitter (4) is provided in the optical path of the pump light, the beam splitter (4) transmits part of the pump light as the first pump light and reflects part of the pump light as the second pump light; a reflection component (5) is provided in the optical path of the first pump light and the second pump light, the first pump light is reflected to the first end of the optical fiber (3) through the reflection component (5), and the second pump light is reflected to the second end of the optical fiber (3) through the reflection component (5), the optical fiber (3) is provided in the optical path of the signal light, the signal light is output by the signal light source (2), and the power of the second pump light is detected by the power detection component (10) provided in the reflection component (5); The target parameters of the rotating adjustable waveplate (9) are calculated based on the required power of the second pump light, wherein the required power of the second pump light is a preset value. The adjustable waveplate (9) is disposed between the pump source (1) and the beam splitter (4). The adjustable waveplate (9) is used to adjust the ratio of the first pump light and the second pump light split by the beam splitter (4) by adjusting the polarization direction of the pump light. The adjustable waveplate (9) is equipped with a driving element. The driving element is electrically connected to a control module (11). The control module (11) is electrically connected to the power detection component (10). The control module (11) is used to calculate the target parameters of the rotating adjustable waveplate (9) based on the detection result of the power detection component (10). Rotate the tunable waveplate (9) according to the target parameters and detect that the power of the second pump light is equal to the required power of the second pump light; The first end of the optical fiber (3) receives the unamplified signal light, and the second end of the optical fiber (3) outputs the amplified signal light. The first pump light is input to the first end through the reflection component (5) and is absorbed by the optical fiber (3). The second pump light is input to the second end through the reflection component (5) and is absorbed by the optical fiber (3). At this time, the signal light is amplified through the optical fiber (3).

10. The control method for a bidirectional pump amplifier according to claim 9, characterized in that, include: The first residual light of the first pump light and the second residual light of the second pump light are collected, wherein the first residual light is the first pump light remaining after absorption by the optical fiber (3), and the second residual light is the second pump light remaining after absorption by the optical fiber (3). The second residual light is output from the first end and, through the first dichroic mirror (51) set at the first end of the optical fiber (3), the second residual light is reflected back to the beam splitter (4) according to the optical path of the first pump light. The first residual light is output from the second end and, through the second dichroic mirror (52) disposed at the second end of the optical fiber (3), the first residual light is reflected in the opposite direction to the beam splitter (4) according to the optical path of the second pump light. The beam splitter (4) is also used to transmit the first residual light as the third residual light and reflect the second residual light as the fourth residual light, and to collect the third residual light and the fourth residual light by a light recovery device (6) arranged along the optical path of the third residual light.

11. A laser, characterized in that, It has a bidirectional pump amplifier as described in any one of claims 1 to 8, and is configured to perform the control method as described in any one of claims 9 to 10.

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