Bidirectional pumping amplifier, control method and laser

Abstract

The invention discloses a bidirectional pumping amplifier, a control method and a laser, and relates to the technical field of pumping amplifiers, and the bidirectional pumping amplifier comprises a pumping source which is used for outputting pumping light; the signal light source is used for outputting signal light; the optical fiber is arranged on a light path of the signal light, the optical fiber is used for amplifying the signal light through the pump 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 beam splitter is arranged on a light path of the pump light and used for splitting the pump light into first pump light and second pump light, the first pump light is linearly polarized light transmitted by the beam splitter, and the second pump light is linearly polarized light reflected by the beam splitter; the reflection assembly is arranged on light paths of the first pump light and the second pump light and used for reflecting the first pump light to the first end and reflecting the second pump light to the second end, and the bidirectional pumping effect is achieved through a single pumping source.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pump amplifier, in particular to a bidirectional pump amplifier, a control method and a laser. BACKGROUND

[0002] The pump amplifier is one of the common core devices in the field of laser application, which mainly realizes the amplification of signal light power by using the energy of pump light.

[0003] The existing signal light amplification methods include forward pumping, backward pumping and bidirectional pumping. The bidirectional pumping can combine the advantages of forward pumping and backward pumping, has a high signal-to-noise ratio and slope efficiency, and has a more uniform temperature distribution, which can effectively reduce the mode instability effect, and is an optimal pumping method for realizing high-power amplification.

[0004] However, in actual application, the optical fiber cannot completely absorb the bidirectional input pump light in the bidirectional pumping process, and the remaining pump light continues to output to the opposite pump source, which affects the stability of the pump source power, and in serious cases, the pump source even fails. Therefore, the bidirectional pumping accounts for a small proportion in the adopted pumping methods. SUMMARY

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

[0006] In one technical solution of the present application, a bidirectional pump amplifier, a control method and a laser are provided, which include: a pump source for outputting pump light; a signal light source for outputting signal light; an optical fiber arranged on the light path of the signal light, the optical fiber being used for amplifying the signal light by using the pump light, a first end of the optical fiber inputting unamplified signal light, and a second end of the optical fiber outputting amplified signal light; a beam splitter arranged on the light path of the pump light, for dividing the pump light into first pump light and 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 assembly arranged on the light paths 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 a technical solution of the present application, the signal light and the pump light have a wavelength difference; the reflection assembly further comprises a first dichroic mirror and a second dichroic mirror, the first dichroic mirror is arranged at the first end of the optical fiber and used for reflecting the first pump light to the first end; the second dichroic mirror is arranged at the second end of the optical fiber and used for reflecting the second pump light to the second end; the first dichroic mirror and the second dichroic mirror are arranged on the light path of the signal light; the first end is further used for outputting the second residual light of the second pump light, and the second end is further used for outputting the first residual light of the first pump light; based on the reflection assembly, 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 assembly is further used for reversely reflecting the first residual light to the beam splitter according to the light path of the second pump light, and reversely reflecting the second residual light to the beam splitter according to the light path of the first pump light; the beam splitter is further used for transmitting the first residual light as third residual light and reflecting the second residual light as fourth residual light, the fourth residual light has the same light path as the third residual light, and an optical line recycling device is arranged along the light path of the third residual light, and an input port of the optical line recycling device corresponds to the light path of the third residual light.

[0008] In a technical solution of the present application, the reflection assembly further comprises a first reflection assembly and a second reflection assembly, the first reflection assembly comprises a first reflector arranged on the light path of the first pump light and used for reflecting the first pump light to the first dichroic mirror; the second reflection assembly comprises a second reflector arranged on the light path of the second pump light and used for reflecting the second pump light to the second dichroic mirror.

[0009] In a technical solution of the present application, the first dichroic mirror and the second dichroic mirror have a transmittance of greater than 90% for the wavelength of the signal light, and a reflectivity of greater than 90% for the wavelength of the pump light.

[0010] In a technical solution of the present application, a first light barrier and a second light barrier are arranged on the light path of the signal light, the first light barrier is arranged between the signal light source and the first dichroic mirror and used for intercepting the second residual light; the second light barrier is arranged on the side of the second dichroic mirror away from the optical fiber and used for intercepting the first residual light.

[0011] In a technical solution of the present application, the pump light is linearly polarized light; further comprising an adjustable wave plate arranged between the pump source and the beam splitter, the adjustable wave plate is used for adjusting the proportion 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 of the technical solutions of the present application, a power detection component is arranged on the reflection component, and is configured to detect the power of the first pump light and / or the power of the second pump light; the adjustable wave plate is provided with a driving element, the driving element is electrically connected with a control module, the control module is electrically connected with the power detection component, and the control module is configured to control the driving element to rotate the adjustable wave plate according to the detection result of the power detection component.

[0013] In one of the technical solutions of the present application, a lens component is further included, and the lens component includes: a first lens arranged between the first end and the first dichroic mirror, configured to focus the signal light and the first pump light, and collimate the second residual light; a second lens arranged between the second end and the second dichroic mirror, configured to collimate the signal light and the first residual light, and focus the second pump light; and a third lens arranged between the pump source and the adjustable wave plate, configured to collimate the pump light.

[0014] In one of the technical solutions of the present application, the optical fiber is a rod photonic crystal fiber, the fiber mode field diameter of the optical fiber is greater than the beam waist diameter of the signal light, and the core numerical aperture of the optical fiber is greater than the numerical aperture of the signal light; the cladding diameter of the optical fiber is greater than the beam waist diameter of the pump light, and the cladding numerical aperture of the optical fiber is greater than the numerical aperture of the pump light.

[0015] In one of the technical solutions of the present application, a control method of a bidirectional pump amplifier is provided, which comprises sequentially turning on a signal light source and a pump source, and receiving and detecting the power of second pump light, wherein the pump source is configured to output linearly polarized pump light, a beam splitter is arranged in the light path of the pump light, and the beam splitter transmits part of the pump light as first pump light and reflects part of the pump light as the second pump light; a reflection assembly is arranged in the light path of the first pump light and the second pump light, the first pump light is reflected to a first end of an optical fiber through the reflection assembly, and the second pump light is reflected to a second end of the optical fiber through the reflection assembly, the optical fiber is arranged in the light path of signal light output by the signal light source, a power detection assembly arranged in the reflection assembly is configured to detect the power of the second pump light; according to the required power of the second pump light, a target parameter of a rotatable wave plate is calculated, wherein the required power of the second pump light is a preset value, the rotatable wave plate is arranged between the pump source and the beam splitter, the rotatable wave plate is configured to adjust the proportion 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 rotatable wave plate is provided with a driving element, the driving element is electrically connected with a control module, the control module is electrically connected with the power detection assembly, the control module is configured to calculate the target parameter of the rotatable wave plate according to the detection result of the power detection assembly; the rotatable wave plate is rotated according to the target parameter, and the power of the second pump light is detected to be equal to the required power of the second pump light; the amplification of the signal light is completed; the first end of the optical fiber inputs the unamplified signal light, the second end of the optical fiber outputs the amplified signal light, the first pump light is input into the first end through the reflection assembly, the first pump light is absorbed by the optical fiber, the second pump light is input into the second end through the reflection assembly, the second pump light is absorbed by the optical fiber, and at this time, the signal light is amplified through the optical fiber.

[0016] In one technical solution of the present application, first residual light of the first pump light and 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, 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 and is reflected to the beam splitter in the light path of the first pump light through a first dichroic mirror arranged at the first end of the optical fiber; the first residual light is output from the second end and is reflected to the beam splitter in the light path of the second pump light through a second dichroic mirror arranged at the second end of the optical fiber, the beam splitter is further configured to transmit the first residual light as third residual light and reflect the second residual light as the fourth residual light, and the third residual light and the fourth residual light are collected through a light recycling device arranged along the light path of the third residual light.

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

[0018] The present application has the advantages of solving the problem of power instability of the pump source caused by the impact of unabsorbed residual pump light on the bidirectional pump source, achieving bidirectional pumping effect with one pump source, and reducing the structural cost. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0021] Figure 3 is a flowchart of the adjustment method of the ratio of horizontal and vertical polarization pump light power in the present 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 mirror; 54, second reflection assembly; 541, second mirror; 6, light recycling device; 7, first diaphragm; 8, second diaphragm; 9, adjustable wave plate; 10, power detection assembly; 11, control module; 12, lens assembly; 121, first lens; 122, second lens; 123, third lens. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present application will be described in detail below with reference to the drawings, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the scope of protection of the present application can be more clearly defined.

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

[0025] The pump amplifier can amplify the signal light with the pump light in the optical fiber 3, but the optical fiber cannot guarantee that the input pump light is 100% absorbed, and the residual pump light that is not absorbed will continue to propagate in the input direction. In the common bidirectional pumping structure, a pump source 1 is arranged at the first end and the second end of the optical fiber 3 respectively. The pump source 1 inputs two opposite pump lights from the first end and the second end of the optical fiber 3 to the optical fiber 3, and the two pump lights are absorbed by the optical fiber 3 to amplify the signal light near the first end and the second end respectively, so as to realize the preferred pumping mode of high-power amplification with high signal-to-noise ratio and slope efficiency, and uniform temperature distribution in the optical fiber 3. However, the corresponding residual pump light that is not absorbed is input into the opposite pump source 1, and the pump source 1 at both ends is impacted, which destroys the power stability of the output of the pump source 1 and affects the amplification effect of the signal light.

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

[0027] In a specific embodiment of the present application, as shown in Figure 1 The present application shows a pump amplifier realizing bidirectional pumping mode by a pump source 1. The pump source 1 is used for outputting pump light, and the signal light source 2 is used for outputting signal light. The optical fiber 3 is arranged on the light path of the signal light, and the optical fiber 3 has a first end and a second end corresponding to the two ends of the optical fiber 3 respectively. The signal light is input into the first end of the optical fiber 3, and the signal light is amplified in the optical fiber 3 with the pump light. The amplified signal light is output through the second end of the optical fiber 3.

[0028] The pump source 1 is used for outputting pump light, and the beam splitter 4 is arranged on the light path of the pump light. The beam splitter 4 can divide the pump light into first pump light and 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. The first pump light and the second pump light are divided, and the reflecting assembly 5 is arranged on the light path of the first pump light and the second pump light. The reflecting assembly 5 reflects the first pump light to the first end of the optical fiber 3, and the first pump light is input into the optical fiber 3 at the same end as the signal light. The reflecting assembly 5 reflects the second pump light to the second end of the optical fiber 3, and the second pump light is input into the optical fiber 3 from the second end.

[0029] The single pump source 1 emits a beam of pump light, which is split into first pump light and second pump light by the beam splitter 4. In terms of the number of pump light, the technical feature requirement of the two pump sources respectively emitting a beam of pump light in the bidirectional pumping structure is achieved. Considering the quality of pump light, the sum of the power of the first pump light and the power of the second pump light emitted by the single pump source 1 is generally less than the sum of the power of two beams of pump light respectively output by two pump sources with the same power.

[0030] For high pump power requirements, a higher power model of pump source can be selected, or multiple pump sources can be combined into one pump source for output. At this time, the higher power pump light is split into first pump light and second pump light, and the power of the first pump light and the second pump light can compensate for the problem of smaller power due to the output of the single pump source 1. It should be noted that the combination of multiple sub-pump sources to form the pump source 1 is a common means to increase the power of the pump source. Compared with directly using two sub-pump sources, the single pump source 1 has the advantages of saving pump source installation space, time, optimizing installation steps and space arrangement.

[0031] According to the embodiment, the application can achieve bidirectional pumping and amplification of signal light by a single pump source 1, which has lower use cost and simpler control mode compared with the common bidirectional pumping structure.

[0032] The first pump light and the second pump light are respectively reflected by the reflection assembly 5. The first pump light is linearly polarized light transmitted by the beam splitter 4, and its propagation direction is the same as that 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, and the angle is less than 180 degrees.

[0033] For the first pump light, the reflection assembly 5 reflects the first pump light to the first end of the optical fiber 3 by not less than once reflection, and the first pump light is input into the optical fiber 3 from the first end. For the second pump light, the reflection assembly 5 reflects the second pump light to the second end of the optical fiber 3 by not less than once reflection, and the second pump light is input into the optical fiber 3 from the second end.

[0034] Because the cladding numerical aperture of the optical fiber 3 is large, the reflection assembly 5 does not have to reflect the first pump light to be collinear with the optical path of the signal light when reflecting. Instead, the first pump light is reflected to the first end of the optical fiber 3 under the premise that there is a certain angle deviation between the optical path of the first pump light and the optical path of the signal light. At the same time, the second pump light does not have to be reflected to be collinear with the optical path of the signal light, but is reflected to the second end of the optical fiber 3 under the premise that there is a certain angle deviation between the optical path of the second pump light and the optical path of the signal light. The deviation angle depends on the specific cladding numerical aperture of the optical fiber and the numerical aperture of the pump light.

[0035] In one specific embodiment of the present application, the beam splitter 4 specifically comprises a polarization beamsplitter cube (PBSPolarization Beamsplitter). The polarization beamsplitter cube comprises two cemented right-angle prisms, and a polarization beamsplitter film is coated on the cemented hypotenuse of the two prisms. The pump light emitted by the pump source 1 is incident on the cemented hypotenuse at an angle of 45 degrees, and is split into the first pump light and the second pump light by the beam splitter 4. The first pump light is horizontal pump light, and the second pump light is vertical pump light. The exit angle between the first pump light and the second pump light is 90 degrees.

[0036] In one specific embodiment of the present application, the signal light has a wavelength difference from the pump light. The reflection assembly 5 further comprises a first dichroic mirror 51 and a second dichroic mirror 52, and the first dichroic mirror 51 and the second dichroic mirror 52 are both arranged on the light path of the signal light. The first dichroic mirror 51 is arranged 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 arranged at the second end of the optical fiber 3, and is used to reflect the second pump light to the second end.

[0037] The dichroic mirror is an optical element that selectively realizes high transmission or high reflection for a specific wavelength band according to the wavelength of light. The first dichroic mirror 51 and the second dichroic mirror 52 of the reflection assembly 5 have high reflectivity for the wavelength band of the pump light, and have high transmissivity for the wavelength band of the signal light. The first dichroic mirror 51 and the second dichroic mirror 52 transmit the signal light, and the first dichroic mirror 51 and the second dichroic mirror 52 reflect the pump light.

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

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

[0040] The wavelength of the signal light and the wavelength of the pump light are selected depending on the type of the rare-earth ion doped in the gain fiber, and different rare-earth ions have their specific absorption spectrum and emission spectrum. The absorption spectrum determines the wavelength of the pump light that can be used, and the emission spectrum determines the wavelength of the signal light that can be used. In industrial fiber lasers, for example, a ytterbium-doped fiber is mostly used, and the ytterbium ion absorption spectrum has two absorption peaks at 915 nm and 976 nm, so the pump wavelength is mostly 915 nm and 976 nm. Other wavelengths near the absorption peaks can also be used as pump light, but the efficiency is relatively low. The emission spectrum of the ytterbium ion is 1000 to 1200 nm, and the laser wavelength of the pulsed laser is generally 1064 nm, while the wavelength of the continuous laser is within 1070 to 1080 nm.

[0041] The first dichroic mirror 51 and the second dichroic mirror 52 are both arranged on the light path of the signal light, and the first pump light is reflected to the first end, and the second pump light is reflected to the second end. When the first pump light is reflected to the first end by the first dichroic mirror 51, and the second pump light is reflected to the second end by the second dichroic mirror 52, the light paths of the first pump light, the second pump light and the signal light are collinear, or in other words, without considering the direction of propagation, the light paths of the first pump light and the second pump light share a light path with the signal light.

[0042] It is known that the fiber 3 is arranged according to the light path of the signal light, and the end faces of the two ends of the fiber 3 are perpendicular to the direction of propagation of the signal light. In this embodiment, similarly, when the first pump light and the second pump light are input through the first end and the second end of the fiber 3, the incident directions are respectively perpendicular to the end face of the first end and the end face of the second end. Maintaining the input at a perpendicular angle to the end face of the fiber 3 can ensure the input accuracy of the first pump light and the second pump light and improve the input efficiency.

[0043] In order to avoid the impact of the residual pump light that is not absorbed on the stability of the pump source, for the residual pump light that is not absorbed, in one specific embodiment of the present application, the remaining part of the first pump light that is not absorbed by the fiber 3 forms the first residual light. The first residual light continues to propagate in the direction of the first pump light and is output from the second end of the fiber 3. Similarly, the remaining part of the second pump light that is not absorbed by the fiber 3 forms the second residual light, and the second residual light continues to propagate in the direction of the second pump light and is output from the first end of the fiber 3.

[0044] Since the first pump light and the second pump light are collinear and opposite in direction when the first pump light and the second pump light enter the first end and the second end of the input fiber 3, the first residual light and the second residual light are collinear and opposite in direction when the first residual light and the second residual light enter the second end and the first end of the output fiber 3. Since the optical path is reversible, at this time, the first residual light is reflected to the beam splitter 4 through the reflection assembly 5 in the reverse direction along the optical path of the second pump light, and the second residual light is reflected to the beam splitter 4 through the reflection assembly 5 in the reverse direction along the optical path of the first pump light.

[0045] The beam splitter 4 is also used for transmitting the first residual light as third residual light and reflecting the second residual light as fourth residual light, the fourth residual light being the same as the third residual light in the optical path. The light ray recycling device 6 is arranged along the optical path of the third residual light, and the input port of the light ray recycling device 6 is arranged corresponding to the optical path of the third residual light. The first residual light and the first pump light are both pump light transmitted by the beam splitter 4, and the second residual light and the second pump light are both pump light reflected by the beam splitter 4. That is, the beam splitter 4 transmits the pump light to which the first residual light belongs twice, and reflects the pump light to which the second residual light belongs twice.

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

[0047] For the third residual light and the fourth residual light, the light ray recycling device 6 is arranged on the optical path of the third residual light, and the input port of the light ray recycling device 6 is directly opposite the optical path of the third residual light, so that the third residual light and the fourth residual light can be input into the light ray recycling device 6 through the input port of the light ray recycling device 6.

[0048] In an example of the present application, the light ray recycling device 6 includes a light extinction cylinder, which is arranged as a hollow conical barrel, the inside of the cylinder is treated by sanding or etching to have a rough surface. The third residual light and the fourth residual light are collected to one end of the light extinction cylinder and are diffusely reflected in the inside of the cylinder and finally completely absorbed.

[0049] In another optional example of the present application, the light extinction cylinder can be any one of a beam current collector, a light beam collector, and a light pocket.

[0050] In one specific embodiment of the present application, the reflection assembly 5 further comprises a first reflection assembly 53 and a second reflection assembly 54. The first reflection assembly 53 comprises a first reflector 531, which comprises two reflectors. The first reflector 531 controls the reflection of the first pump light to the first dichroic mirror 51 by reflecting the first pump light twice, so as to realize the input of the first pump light into the first end of the optical fiber 3 in a light path collinear with the second pump light.

[0051] Similarly, the second reflection assembly 54 comprises 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, so as to realize the input of the second pump light into the second end of the optical fiber 3 in a light path collinear with the first pump light.

[0052] Through the present embodiment, the first pump light is controlled by the first reflection assembly 53, and the second pump light is controlled by the second reflection assembly 54. The two controls are separately divided, which reduces the correlation between the components and thus reduces the processing difficulty in arrangement and maintenance.

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

[0054] The first residual light and the second residual light are both beams emitted by the pump source 1, so the wavelengths of the first residual light and the second residual light are the same as the wavelength of the pump light emitted by the pump source. Although the wavelength reflectivity of the first dichroic mirror 51 and the second dichroic mirror 52 to the pump light is greater than 90%, part of the first residual light and the second residual light still transmits through the second dichroic mirror 52 or the first dichroic mirror 51. The second residual light transmits through the first dichroic mirror 51 to the signal light source 2, and the first residual light transmits through the second dichroic mirror 52 in the same direction as the signal light.

[0055] The input of the second residual light to the signal light source will cause the power stability of the signal light output by the signal light source to decrease, and even cause the signal light source to fail. The first residual light and the signal light have different wavelengths and beam qualities, which will affect the subsequent elements and cause the system stability to decrease. The spot of the first residual light and the second residual light is much larger than that of the signal light. By arranging the second light barrier 8 and the first light barrier 7 with appropriate light transmission apertures, the signal light can completely pass through, and most of the first residual light and the second residual light can be intercepted. In one specific embodiment of the present application, the spot diameter of the signal light is 1 mm, and the spot diameter of the pump light is 10 mm. The light transmission diameter of the light barrier is set to 2 mm.

[0056] In one embodiment of the present application, the pump light is linearly polarized light. An adjustable wave plate 9 is also included, which is arranged between the pump source 1 and the beam splitter 4. The adjustable wave plate 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 different power and frequency of the signal light, there is an optimal power ratio of the first pump light and the second pump light in the amplification process through the optical fiber 3, so as to obtain the optimal amplification power and nonlinear suppression. However, because the polarization direction of the pump light is determined when the pump source 1 outputs, the power ratio of the first pump light and the second pump light split by the beam splitter 4 is fixed, and the optimal ratio for different power or frequency of the signal light cannot be continuously maintained.

[0058] The adjustable wave plate 9 is an optical element using the birefringence principle. The adjustable wave plate 9 has different refractive indexes in two mutually perpendicular directions, in which the smaller refractive index is the fast axis, and the larger refractive index is the slow axis. The linearly polarized light has a fixed vibration direction. When the linearly polarized light enters the wave plate, the linearly polarized light is decomposed into two directions of the fast axis and the slow axis. The two components have a fixed phase relationship, which is determined by the angle between the polarization direction of the linearly polarized light and the fast axis of the wave plate. By rotating the angle, the polarization direction of the pump light can be adjusted, and then the ratio of the first pump light and the second pump light split by the beam splitter 4 can be adjusted.

[0059] In the embodiment, the adjustable wave plate 9 is specifically a 1 / 2 wave plate (half wave plate). The 1 / 2 wave plate has continuous adjustability. For example, by rotating the 1 / 2 wave plate itself through a motor, the polarization direction of the pump light can be continuously and smoothly changed, and the flexibility of the pump light adjustment mode is improved.

[0060] In one embodiment of the present application, a lens assembly 12 is also included, which is used to collimate or focus the input light. The lens assembly 12 includes: a first lens 121 arranged between the first end and the first dichroic mirror 51, which is used to focus the signal light and the first pump light, and collimate the second residual light. A second lens 122 is arranged between the second end and the second dichroic mirror 52, which is used to collimate the signal light and the first residual light, and focus the second pump light. A third lens 123 is arranged between the pump source 1 and the adjustable wave plate 9, which is 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 fiber 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 at 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, ensuring 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] The pump source 1 is used for outputting linearly polarized pump light, the beam splitter 4 transmits part of the pump light as first pump light and reflects part of the pump light as second pump light. The first pump light and the second pump light are reflected to the first end and the second end of the optical fiber 3 through the reflection assembly 5 arranged on the light path of the first pump light and the second pump light respectively. The optical fiber 3 is arranged on the light path of signal light, the signal light is output by the signal light source 2, and the power of the second pump light is detected through the power detection assembly 10 arranged on the reflection assembly 5.

[0069] Second step: according to the required power of the second pump light, the target parameter of the rotatable wave plate 9 is calculated.

[0070] The required power of the second pump light is a preset value, and the rotatable wave plate 9 is arranged between the pump source 1 and the beam splitter 4. The rotatable wave plate 9 is used for adjusting the proportion 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 rotatable wave plate 9 is provided with a driving element, the driving element is electrically connected with the control module 11, and the control module 11 is electrically connected with the power detection assembly 10. The control module 11 is used for calculating the target parameter of the rotatable wave plate 9 according to the detection result of the power detection assembly 10.

[0071] Third step: the rotatable wave plate 9 is rotated according to the target parameter until the detected power of the second pump light is equal to the required power of the second pump light.

[0072] Fourth step: the amplification of the signal light is realized.

[0073] The first end of the optical fiber 3 inputs the unamplified signal light, and the second end of the optical fiber 3 outputs the amplified signal light. The first pump light is input into the first end through the reflection assembly 5, and the first pump light is absorbed by the optical fiber 3. The second pump light is input into the second end through the reflection assembly 5, and the second pump light is absorbed by the optical fiber 3. At this time, the signal light is amplified through the optical fiber 3.

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

[0075] The first residual light is the first pump light remaining after being absorbed by the optical fiber 3, and the second residual light is the second pump light remaining after being absorbed by the optical 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 to the beam splitter 4 in the reverse direction of the light path of the first pump light through the first dichroic mirror 51 arranged at the first end of the optical fiber 3, and the first residual light is reflected to the beam splitter 4 in the reverse direction of the light path of the second pump light through the second dichroic mirror 52 arranged at the second end of the optical fiber 3. The beam splitter 4 is also used for transmitting the first residual light as third residual light and reflecting the second residual light as fourth residual light, and collecting the third residual light and the fourth residual light through the light line recovery device 6 arranged along the light path of the third residual light.

[0076] In one embodiment of the present application, a laser is provided, which has the bidirectional pumped amplifier described in any of the above embodiments.

[0077] In one optional embodiment of the present application, the signal light is linearly polarized collimated light with a spot diameter of 0.8 mm, a central wavelength of 1030 nm, a power of 300 mW, a pulse width of 500 ps, a spectral width of 8 nm, and a repetition frequency of 1 MHz. This set of parameters is only used in this embodiment, and other parameters can also be selected.

[0078] The first dichroic mirror 51 and the second dichroic mirror 52 are high-transmissive to the 1030 nm signal light and high-reflective to the 976 nm pump light.

[0079] The first lens 121 is used to focus the signal light and the horizontally polarized pump light, and to collimate the residual vertically polarized pump light. In this embodiment, the focal length of the first lens 121 is 30 mm. After the signal light is focused, its beam waist diameter and numerical aperture are both smaller than the mode field diameter and the core numerical aperture of the rod-shaped photonic crystal fiber 3, so as to ensure 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 beam waist diameter and numerical aperture are both smaller than the cladding diameter and the cladding numerical aperture of the rod-shaped photonic crystal fiber 3, so as to ensure 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 is a 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 second lens 122 is used to collimate the amplified signal light and the residual horizontally polarized pump light, and to focus the vertically polarized pump light. In this embodiment, the focal length of the second lens 122 is 30 mm. After the vertically polarized pump light is focused, its beam waist diameter and numerical aperture are both smaller than the cladding diameter and the cladding numerical aperture of the rod-shaped photonic crystal fiber 3, so as to ensure that the pump light is coupled into the cladding of the rod-shaped photonic crystal fiber 3.

[0082] The pump source 1 outputs linearly polarized light with a power of 450 W and a central wavelength of 976 nm, and a numerical aperture of 0.2. The pump source 1 can also be a combination of several sub-pump sources.

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

[0084] The adjustable wave plate 9 is used to adjust the polarization direction of the pump light. The wave plate is a 976 nm 1 / 2 wave plate, and its rotation angle is adjusted by a motor.

[0085] The beam splitter 4 has two functions. The first function is to divide the pump light into horizontal polarization and vertical polarization. The horizontal polarization light transmits through the beam splitter 4, and the vertical polarization light is reflected by 90°. The second function is to prevent residual pump light from entering the pump source 1. The residual horizontal polarization pump light transmits through the beam splitter 4 and enters the light recycling device 6. The residual vertical polarization pump light is reflected by 90° and then enters the light recycling device 6. In this embodiment, the beam splitter 4 is a polarization beam splitting cube with a side length of 25.4 mm and a working wavelength of 620-1000 nm.

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

[0087] The first diaphragm 7 is used to intercept the residual vertical polarization pump light transmitted by the first dichroic mirror 51, and the aperture is 2 mm, which plays a role in protecting the seed source. The second diaphragm 8 is used to intercept the residual horizontal polarization pump light transmitted by the second dichroic mirror 52, and the aperture is 2 mm.

[0088] The power detection assembly 10 is used to detect the vertical polarization pump light transmitted through the second mirror 541, so as to determine the power of the vertical polarization pump light.

[0089] The control module 11 is used to receive the detection result of the power detection assembly 10 and drive the motor of the adjustable wave plate 9, so as to realize a specific horizontal / vertical polarization pump light power ratio.

[0090] In an optional embodiment of the present application, a specific amplification process of the bidirectional pump amplifier is disclosed, which includes: a signal light path: after transmitting through the first dichroic mirror 51, the signal light is focused to the core of the rod-shaped photonic crystal fiber 3 by the first lens 121, and is amplified in the rod-shaped photonic crystal fiber 3 by combining with the pump light. The amplified signal light is collimated by the second lens 122 and then output through the second dichroic mirror 52.

[0091] A pump light path: the linear polarization pump light output by the pump source 1 enters the beam splitter 4 after being collimated by the third lens 123 and changing the polarization direction by the adjustable wave plate 9 in turn. The beam splitter 4 divides the pump light into horizontal polarization and vertical polarization.

[0092] A horizontal polarization pump light path: transmitting through the beam splitter 4, reflecting by the first mirror 531 and the first dichroic mirror 51 in turn, and focusing by the first lens 121, the horizontal polarization pump light is coupled into the cladding of the rod-shaped photonic crystal fiber 3. The residual horizontal polarization pump light which is not absorbed by the rod-shaped photonic crystal fiber 3 is collimated by the second lens 122, reflected by the second dichroic mirror 52 and the second mirror 541 in turn, and then enters the beam splitter 4. Finally, the residual horizontal polarization pump light transmits through the beam splitter 4 and enters the light recycling device 6.

[0093] The vertical polarization pump light path: reflected by the beam splitter 4, sequentially reflected by the second mirror 541, the second dichroic mirror 52 and focused by the second lens 122, coupled into the cladding of the rod photonic crystal fiber 3. The residual vertical polarization pump light not absorbed by the rod photonic crystal fiber 3 is collimated by the first lens 121, sequentially reflected by the first dichroic mirror 51 and the first mirror 531 into the beam splitter 4, and finally enters the light recycling device 6 after being reflected by the beam splitter 4.

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

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

[0096] S302: Under a certain pump current, the control module 11 drives the adjustable wave plate 9 to rotate slowly by 1 / 4 turn, and records the maximum value P max recorded by the power detection assembly 10. max Corresponding to the pump output power P0 under this pump current.

[0097] S303: Input the required power ratio a of the horizontal polarization pump light and the vertical polarization pump light, and the software calculates the value P=P max / (a+1) that needs to be detected by the power detection assembly 10.

[0098] S304: The control module 11 drives the adjustable wave plate 9 to rotate slowly until the value measured by the power detection assembly is P. At this time, the power ratio of the horizontal polarization pump light and the vertical polarization pump light is a, the vertical polarization pump light power P2=P0*P / P max , and the horizontal polarization pump light power P1=P0-P2.

[0099] Another optional embodiment of the present application provides a laser with the bidirectional pump amplifier described in any of the above embodiments, and realizes high-power amplification of signal light by combining the method described in any of the above embodiments.

[0100] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. In actual implementation, another division mode can be used. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0101] ​The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may also be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0102] The above is only an embodiment of the application, and does not limit the patent scope of the application, and any equivalent structural transformation made by using the content of the specification and drawings, or directly or indirectly applied to other related technical fields, is also included in the patent protection scope of the 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.

2. The bidirectional pump amplifier according to claim 1, characterized in that, 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.

3. The bidirectional pump amplifier according to claim 2, 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).

4. The bidirectional pump amplifier according to claim 2, 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.

5. The bidirectional pump amplifier according to claim 2, 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.

6. The bidirectional pump amplifier according to claim 2, 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.

7. The bidirectional pump amplifier according to claim 6, 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).

8. The bidirectional pump amplifier according to claim 6, 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.

9. 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.

10. 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).

11. The control method for a bidirectional pump amplifier according to claim 10, 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 back 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.

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

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