A multi-path multi-pass amplification depolarization self-compensation system and method

Abstract

The application discloses a kind of multi-path multi-path depolarization self-compensation system and method, it is related to the field of high-energy laser of frequency.The multi-path multi-path amplification depolarization self-compensation system includes in first optical path, second optical path, third optical path;The first optical path is used for the main optical path of multi-path amplification and closed loop transmission;The second optical path and third optical path are used for respectively rotating the component light of the depolarized laser to be even-path amplified polarization state, to realize depolarization self-compensation.Compared with prior art, the depolarization self-compensation scheme provided in the application makes the laser depolarization after passing through amplifier by even-path to obtain self-compensation, the whole optical path unidirectional operation can naturally avoid counter laser, avoid front stage to be damaged by high-energy counter laser, also can reduce laser output near-field modulation, realize controllable multi-path amplification, make up the shortcomings that spot aperture is small and depolarization compensation effect is bad in the currently commonly used multi-path amplification optical path, suitable for the depolarization compensation of multi-path amplification optical path of high-energy system frequency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-energy laser with high repetition rate, and particularly discloses a multi-path multi-pass depolarization self-compensation system and a compensation method. BACKGROUND

[0002] The multi-pass amplification optical path of the high-energy and high-repetition rate laser system in the prior art mainly follows the multi-pass optical path widely used in the low-energy or single-run laser system. However, the high-energy requires large-aperture beam amplification, and therefore the conventional off-axis multi-pass and coaxial double-pass or multi-pass schemes may encounter laser depolarization. The laser depolarization may cause difficulty in stray light control on one hand, and may cause near-field light intensity distribution modulation on the other hand, which not only reduces the system output capacity, but also increases the risk of damage to the system optical elements. In addition, in the prior art, the off-axis optical path has the problem of low beam duty ratio, and the coaxial multi-pass is highly dependent on the purity of the polarization state. Once depolarization occurs, if the depolarization effect caused by thermal stress birefringence cannot be effectively compensated, it will not only cause difficulty in stray light control, but also may cause laser self-excitation amplification, and reduce the actual isolation ratio between the stages, thereby causing reverse depolarization light and causing damage to the previous stage. SUMMARY

[0003] The present application aims at the above-mentioned problems, and provides a multi-path multi-pass amplification depolarization self-compensation system and method, which can not only realize controllable multi-pass amplification of the laser to be amplified, but also realize depolarization self-compensation of the amplified laser, and can also make the input and output light be off-axis to avoid damage to the optical elements.

[0004] The technical scheme adopted by the present application is as follows:

[0005] A multi-path multi-pass amplification depolarization self-compensation system, which comprises a first optical path, a second optical path and a third optical path between a first node and a third node, wherein the second optical path further comprises a second node; the transmission direction of the third optical path between the first node and the third node is opposite to the transmission direction of the first / second optical path; the first optical path is a main optical path for multi-pass amplification and closed-loop transmission of main laser; the second optical path is used for transmitting linearly polarized light to the first optical path and transmitting component light of depolarized laser to the first optical path after polarization state rotation; and the third optical path is used for transmitting another component light of depolarized laser to the first optical path after polarization state rotation, so as to realize depolarization self-compensation.

[0006] In another aspect, the application also provides a corresponding multi-path amplification depolarization self-compensation method, mainly based on the depolarization self-compensation for multi-path amplification and depolarization self-compensation, by adjusting the optical rotation state of the first polarization selection module, the light beams passing through different optical paths are transformed between different polarization states, and then the light beams can complete controllable multi-path amplification and depolarization self-compensation in the closed-loop optical path system.

[0007] In summary, due to the adoption of the above technical solutions, the application has the following advantages:

[0008] (1) Compared with the prior art, the multi-path amplification depolarization self-compensation system and method provided by the application constructs a multi-ring optical path, wherein the main optical path is used for amplification, and the multi-branch optical path is used for polarization state rotation, and the combination of image transmission enables the laser to run in full aperture in the optical path in theory, and the depolarization of linearly polarized light after passing through the amplifier for an even number of times is self-compensated, and the whole optical path is unidirectional, which can naturally avoid counter laser and avoid damage to the front stage by high-energy counter laser.

[0009] (2) The multi-path amplification depolarization self-compensation scheme provided by the application can also reduce the near-field modulation of laser output, realize controllable multi-path amplification, make up for the shortcomings of small spot aperture and poor depolarization compensation effect in the commonly used multi-path amplification optical path, and is suitable for depolarization compensation of most multi-path amplification optical paths, especially for high-energy systems with high repetition frequency. BRIEF DESCRIPTION OF DRAWINGS

[0010] The application will be described by way of example and with reference to the accompanying drawings, in which:

[0011] Figure 1 is a diagram of the decomposition of the polarization state of laser and the refractive index ellipsoid under the birefringence effect in the amplifier;

[0012] Figure 2 is a structural schematic diagram of a multi-path amplification depolarization self-compensation system of the application;

[0013] Figure 3 is an optical path structure diagram of an embodiment provided by the application;

[0014] Figure 4 is an optical path structure diagram of another embodiment provided by the application;

[0015] Figure 5 is an optical path structure diagram of another embodiment provided by the application;

[0016] Figure 6 is an optical path structure diagram of another embodiment provided by the application.

[0017] In the diagram: N1: First node; N2: Second node; N3: Third node; R1: First optical path; R2: Second optical path; R3: Third optical path; 1: Incident light; 2: First polarization beam splitter; 3: First polarization rotator; 4: Second polarization beam splitter; 5: First reflector; 6: Third polarization beam splitter; 7: Laser amplification module; 8: Second reflector; 9: Third reflector; 10: Image transmitter; 11: Fourth reflector; 12: Second polarization rotator; 13: Phase delayer; 14: Outgoing light; 15: Fifth reflector; 16: Sixth reflector. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.

[0019] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0020] In the optical path of a high-repetition-rate, high-energy, high-thermal laser system, when polarized light passes through a laser amplification device, its polarization state changes due to thermally induced birefringence and the stress on the gain medium, resulting in laser depolarization. This will be illustrated using S-state polarized light as the incident light as an example. Figure 1 As shown. Figure 1 In the diagram, OA represents the polarization direction of the incident light, and OC and OD are the major and minor axes of the refractive index ellipsoid at position O due to thermal birefringence, respectively. The incident polarized light is decomposed into two components: radial (OB) and tangential (AB). The optical path lengths of these two components in the amplifier are OC×L and OD×L, respectively, where L is the path length of the incident light in the gain medium of the laser amplifier device. After the beam passes through the laser head, the radial and tangential components combine to form elliptically polarized light, thereby depolarizing the laser relative to the S-polarization state of the incident light.

[0021] In order to enable self-compensation of depolarized laser after multi-path amplification, this invention provides a multi-path multi-path depolarization self-compensation system and compensation method, and provides a detailed description of the structure and operation of the system.

[0022] Embodiment 1

[0023] As shown in Figure 2 , Figure 2 is a multi-path multi-stage amplification depolarization self-compensation system structure diagram, which can be used in a laser oscillator or a laser amplifier. The multi-path multi-stage amplification depolarization self-compensation system includes a first optical path R1, a second optical path R2, and a third optical path R3 between a first node N1 and a third node N3. The second optical path R2 further includes a second node N2. The third optical path R3 is opposite to the transmission direction of the first / second optical path (R1, R2) between the first node N1 and the third node N3.

[0024] The first node N1 is used to guide the incident light of a polarization state. The second node N2 is used to guide the outgoing light or to guide the non-outgoing light (i.e., only after the last stage of amplification, the outgoing light is guided out, and in the remaining optical paths, only the light beam passes through and enters the next optical path). Since the incident and outgoing positions of the light beam are different, the incident light and the outgoing light are different in axis, avoiding the damage of the system by the counter laser in the system. The third node N3 is used to guide the non-outgoing light into the first optical path R1. At the same time, according to the specific optical path structure, the depolarized laser is split and combined at any one or two of the first node N1, the second node N2, and the third node N3.

[0025] The first optical path R1 is a main optical path for multi-stage amplification and closed-loop transmission of the main laser. The second optical path R2 is used to directly transmit the linearly polarized light amplified by an odd number of stages to the first optical path R1 for amplification, and to transmit the component light of the depolarized laser amplified by an even number of stages to the first optical path R1 for polarization state rotation and amplification. The third optical path R3 is used to transmit another component light of the depolarized laser to the first optical path R1 for polarization state rotation and amplification, thereby realizing depolarization self-compensation.

[0026] The second optical path R2 further includes a first polarization selection module between the first node N1 and the second node N2, which is used to select whether to perform polarization state rotation processing on the light beam according to the amplification stage and the state of the light beam: when the light beam passing through the first polarization selection module is the first stage or the last stage of amplification, the first polarization selection module is adjusted to a non-rotating state; in addition, when the light beam is amplified in the middle stage (i.e., not the first stage or the last stage), the first polarization selection module is adjusted to a rotating working state.

[0027] The third optical path R3 further includes a second polarization selection module, which always maintains a rotating working state, and is used to rotate the polarized light passing through the module by 90 degrees to change its polarization state.

[0028] In a preferred embodiment, asFigure 3 As shown, the first optical path R1 includes a first polarization beam splitter 2 (corresponding to the first node N1), a third polarization beam splitter 6 (corresponding to the third node N3), a laser amplification module 7, a second reflector 8, a third reflector 9, an image transfer device 10, and a fourth reflector 11.

[0029] The first polarization beam splitter 2 is used to introduce the pre-stage incident light 1 for multi-stage amplification into the system on the first optical path, to perform polarization splitting on the depolarized light after odd-stage amplification, and to transmit or reflect the linearly polarized light transmitted back in a closed loop after even-stage amplification. It should be noted that in this embodiment, one stage of amplification is completed when the light beam from the injection position is amplified along the closed loop optical path and returns to the injection position.

[0030] The third polarization beam splitter 6 is used to directly transmit or reflect the incident light for odd-stage amplification, and to perform polarization beam combination on the polarization state component light from different optical paths for even-stage amplification and then introduce it into the first optical path R1 for amplification.

[0031] The laser amplification module 7 is used to perform multi-stage amplification on the main laser: when amplifying the odd-stage, the laser to be amplified is linearly polarized light, and after amplification, the laser is depolarized to obtain the depolarized light in the non-linear polarization state after odd-stage amplification; when amplifying the even-stage, the laser to be amplified is non-linearly polarized light, and after amplification, the laser realizes self-compensation of depolarization to obtain linearly polarized light after even-stage amplification.

[0032] The closed loop transmission module composed of the second reflector 8, the third reflector 9, the image transfer device 10, and the fourth reflector 11 is used to transmit the amplified light beam in a closed loop to the injection position of the incident light 1, i.e., the first polarization beam splitter 2. The reflectors are used to reflect the light beam, and multiple reflectors can form a reflector group in combination with several image transfer devices 10 to enable the laser to return in a closed loop, and in theory, the laser can run in full aperture in the optical path.

[0033] In one embodiment, the number of reflectors can not be limited, and the reflectors can be mirrors, prisms, or other elements that can reflect. The image transfer device 10 can be a 4f imaging system or a single-lens imaging system.

[0034] The second optical path R2 includes a first polarization rotator 3 (corresponding to the first polarization selection module), a second polarization beam splitter 4 (corresponding to the second node N2), and a first reflector 5. The third optical path R3 includes a second polarization rotator 12 (corresponding to the second polarization selection module) and a phase delay device 13.

[0035] The second light path R2 and the third light path R3 are located between the first polarization beam splitter 2 and the third polarization beam splitter 6 on the first light path R1 and form a closed loop, and when the depolarized laser light is polarized at the first polarization beam splitter 2, the two component lights are combined at the third polarization beam splitter 6 after polarization state rotation along the second light path R2 and the third light path R3. In addition, the optical path of the closed loop light path formed by the second light path R2 and the third light path R3 needs to satisfy the image transmission relationship, so that the transmission of the laser light follows the image transmission principle.

[0036] The first polarization rotator 3 is an active optical device, such as an electro-optical switch. The second polarization rotator 12 can be an active polarization rotating device or a passive polarization rotating device, such as a quartz rotor, a nonlinear crystal rotor, a half-wave plate, or an angular pyramid inverter lens group.

[0037] The phase retarder 13 is used to make the optical path difference of the component light transmitted in the second light path R2 and the third light path R3 be zero or an integer multiple of the wavelength of the laser to be amplified. In the embodiment, the phase retarder 13 can be placed in the second light path R2 or the third light path R3, so as to ensure that the optical path difference of the transmission in the two light paths satisfies the foregoing condition.

[0038] The laser amplification device described in the foregoing is a module for providing gain for laser, and in the present application, it is used to describe that the beam will be depolarized after passing through the laser amplification device due to the reasons described in the foregoing. In the embodiment, the laser amplification device can refer to the laser amplification module 7 or the image transfer device 10, or refer to the whole module composed of the laser amplification module 7, the second reflector 8, the third reflector 9, the image transfer device 10, and the fourth reflector 11. In another preferred embodiment, the laser amplification device can also be a gain amplification device containing at least a gain medium, a pump source, and the like.

[0039] The accompanying drawings are combined with the Figure 3 The working process of the depolarization self-compensation system is described by taking the incident light 1 as S-state polarized light as an example. In the initial state, the first polarization beam splitter 2 guides the first S-state polarized light to the second light path to the first polarization rotator 3, and at this time, the first polarization rotator 3 only acts as a transmission element and does not change the polarization state of the incident light. After the S-state polarized light passes through the first polarization rotator 3, it reaches the third polarization beam splitter 6 through the second polarization beam splitter 4 and the first reflector 5 and enters the first light path R1.

[0040] In the first light path, the S state polarized light is depolarized after first pass amplification by the laser amplification module 7, and the depolarized light (for convenience, still transmitted separately as radial and tangential components) is sequentially passed through the second reflector 8, the third reflector 9, the image transfer device 10, and the fourth reflector 11 along the closed-loop first light path R1, and then reaches the first polarization beam splitter 2. At this time, the light beam starting the second light path is split into different P component light and S component light in the radial and tangential components respectively under the splitting effect of the first polarization beam splitter 2, and enters the second light path R2 and the third light path R3 respectively:

[0041] The P component light enters the second light path, and when the P component light reaches the first polarization rotator 3, the working state of the first polarization rotator 3 is adjusted to an optical rotation state, and the P component light is rotated so that the P component light becomes S component light. Then the S component light reaches the third polarization beam splitting device 6 again via the second polarization beam splitter 4 and the first reflector 1;

[0042] On the other hand, the S component light enters the third light path at the same time, and when the S component light reaches the second polarization rotator 12, since the second polarization rotator 12 device always maintains an optical rotation working state during the entire operation of the laser system, the S component light becomes P component light after passing through the second polarization rotator 12, and the P component light enters the phase delay device 13. After precise adjustment of the phase delay device 13, it is ensured that the component light of the second light path and the third light path has a path difference of zero or an integer multiple of the wavelength of the laser to be amplified when reaching the third polarization beam splitter 6.

[0043] At this time, at the position of the third polarization beam splitter 6, the component light of two different polarization states, i.e. the S component light from the second light path R2 and the P component light from the third light path R3, are combined in an equal path length combination manner, and the final combination effect is exactly the same as that of the P state polarized light and the S state polarized light after rotating 90 degrees and then combining at the first polarization beam splitter 2. Since the path difference of the two polarization component light beams of the combination is unchanged, in order to show the depolarization compensation effect, the combined light is still analyzed according to the tangential and radial polarization states independently.

[0044] After the combined laser enters the laser amplification module 7 again, the radial component OB will be transmitted along the path with refractive index OC because the polarization state of the light is rotated by 90 degrees; and the tangential component AB will be transmitted along the path with refractive index OD. After the second amplification of the laser amplification module 7, the optical paths of the two components become OC*L and OD*L respectively. It can be seen that after the laser passes through the laser amplification module 7 twice, the phase difference between the radial component and the tangential component becomes an integer multiple of 2π, and the only change is that the polarization states of the radial and tangential components are both rotated by 90 degrees. The final combined polarization state is also linearly polarized light, that is, the laser obtained after the final two amplifications is P-state linearly polarized light rotated by 90 degrees relative to the first S-state incident light 1.

[0045] In other words, it can be seen that for the depolarization self-compensation system provided in the embodiment of the application, the output of the light beam is pure P-state linearly polarized light after each even-order amplification, that is, after passing through the laser amplification module 7 an even number of times. Therefore, in the embodiment of the application, the optical path required to complete one depolarization self-compensation is an even-order optical path.

[0046] The P-state linearly polarized light after the even-order amplification of the laser amplification module 7 again reaches the first polarization beam splitter 2 along the first light path R1, enters the second light path R2, and reaches the first polarization rotating device 3 again. At this time, the working state of the first polarization rotating device 3 is adjusted according to whether the light beam is output:

[0047] If the system needs to continue to amplify the light beam for multiple times, the first polarization rotating device 3 continues to maintain the rotating working state. At this time, the P-polarized light becomes S-polarized light again, and the first-order or odd-order light path is repeated;

[0048] When the system needs to output the light beam, the first polarization beam splitter 3 is adjusted to a working state of only transmitting without changing the polarization state (i.e., a non-rotating working state). In this way, the P-state linearly polarized light after two amplifications or even-order amplifications can be guided out after passing through the first polarization rotating device 3, for example, guided out through the second polarization beam splitter 4 in this embodiment, to obtain the outgoing light 14 after two amplifications and depolarization self-compensation.

[0049] Embodiment 2

[0050] For the depolarization self-compensation system provided in the application, the polarization state incident light 1 can be P-polarized light or S-polarized light. In Figure 3As shown in the self-compensation system of the depolarization, when the incident light 1 to be amplified is S-state polarized light injected from the first polarization beam splitter 2, the first polarization beam splitter 2 is also used for splitting and polarizing, and the final output light 14 after the even-order amplification and self-compensation of the depolarization is output from the second polarization beam splitter 4; or the incident light 1 can be P-state polarized light injected from the second polarization beam splitter 4, at this time the third polarization element 6 is used for splitting and polarizing, and the final output light 14 after the even-order amplification and self-compensation of the depolarization is output from the first polarization beam splitter 1. That is, for the same optical path, the optical devices corresponding to the first node and the second node can be transposed, and the input and output directions can also be transposed.

[0051] The embodiment takes the incident light 1 as P-state polarized light as an example for optical path description, as shown in the figure, Figure 4 As shown, in the initialization state, the second polarization beam splitter 4 (corresponding to the first node N1 in this embodiment) guides the first-order P-state polarized light to the second optical path to the first polarization rotator 3, at this time the first polarization rotator 3 only acts as a transmission element and does not change the polarization state of the incident light. After the P-state polarized light passes through the first polarization rotator 3, it passes through the first polarization beam splitter 2 (corresponding to the second node N2 in this embodiment) and then sequentially passes through the fourth reflector 11, the image transferor 10, the third reflector 9, and the second reflector 8 to reach the laser amplification module 7 to complete the first amplification. The depolarized laser after the first amplification is subjected to polarization splitting at the third polarization beam splitter 6, and the second optical path is started.

[0052] At this time, the light beam starting the second optical path will enter the second optical path and the third optical path under the splitting action of the third polarization beam splitter 6 according to the respective different P components and S components of the radial and tangential components:

[0053] The S component light enters the second optical path, and when the S component light reaches the first polarization rotator 3 along the first reflector 5 and the second polarization beam splitter 4, the working state of the first polarization rotator 3 is adjusted to be a rotatory state, so that the S component light becomes P-state polarized light, and then the P-state polarized light reaches the first polarization beam splitter 2 again;

[0054] On the other hand, the P component light enters the third optical path at the same time, and after the P component light passes through the phase delay device 13 and the second polarization rotator 12, the polarization state is rotated and precisely adjusted, so that the optical path difference between the second optical path and the third optical path is zero or an integer multiple of the wavelength of the laser to be amplified when the light beams of the second optical path and the third optical path reach the first polarization beam splitter 2.

[0055] At this time, the components of the two different polarization states are combined at the position of the first polarization beam splitter 2, and the combined light continues to enter the laser amplification module 7 along the first optical path to complete secondary amplification, and is emitted from the first polarization beam splitter 2 to obtain the emitted light 14. The final secondary amplified emitted light 14 is S state polarized light rotated by 90 degrees relative to the first path P state incident light 1.

[0056] Embodiment 3

[0057] Figure 5 The structure diagram of another preferred embodiment of the present application is shown in the figure. The polarization state incident light 1 is incident from the first polarization beam splitter 2 and enters the first optical path from the second optical path to the laser amplification module 7 to perform first path amplification. The amplified depolarized light is split at the third polarization beam splitter 6 by the closed loop transmission module composed of the second reflector 8, the third reflector 9 and the image transfer 10. After splitting, the two component lights enter the second optical path and the third optical path respectively to rotate the polarization state, and are combined at the second polarization beam splitter 4 to be amplified again. The linearly polarized light of even path amplification is guided out of the second polarization beam splitter 4 to obtain the emitted light 14 of multi-path amplification and depolarization self-compensation.

[0058] In this embodiment, the first polarization rotator 3 and the second polarization rotator 12 can preferably be large aperture PEPC electro-optical switches as polarization selection modules for controlling the change of the polarization state, which are more suitable for high energy devices with high repetition frequency.

[0059] It should be noted that the number of mirrors and image transfers on each optical path in different embodiments can be increased or decreased according to the needs of the optical path, so that the optical path satisfies the image transfer relationship and realizes multi-path amplification and depolarization self-compensation. At the same time, the same parts as the principles in the foregoing embodiments are not described again in this embodiment.

[0060] Embodiment 4

[0061] Figure 6 The structure diagram of another preferred embodiment of the present application is shown in the figure. The polarization state incident light 1 is incident from the first polarization beam splitter 2 and enters the first optical path from the second optical path to the laser amplification module 7 to perform first path amplification. The amplified depolarized light is split at the third polarization beam splitter 6 by the closed loop transmission module composed of the second reflector 8, the third reflector 9 and the image transfer 10. After splitting, the two component lights enter the second optical path and the third optical path respectively to rotate the polarization state, and are combined at the second polarization beam splitter 4 to be amplified again. The linearly polarized light of even path amplification is guided out of the second polarization beam splitter 4 to obtain the emitted light 14 of multi-path amplification and depolarization self-compensation.

[0062] It should be noted that the number and position of the mirrors and image conveyors on each optical path in the present embodiment can also be set according to the requirements of the optical path, so that the optical path satisfies the image conveying relationship and realizes multi-pass amplification and depolarization self-compensation. Meanwhile, the present embodiment will not repeat the same principles as in the foregoing embodiments.

[0063] Embodiment 5

[0064] The present embodiment is a multi-optical-path multi-pass amplification depolarization self-compensation method, which is based on the system in any of the foregoing embodiments. Taking the system optical path structure in Embodiment 1 as an example, the method comprises the following steps: Figure 3

[0065] S01, adjusting the first polarization rotator 3 to be in a non-rotating state and the second polarization rotator 12 to be in a rotating state, and then directing the polarized incident light 1 from the first polarization beam splitter 2 to the third polarization beam splitter 6 along the second optical path and into the first optical path;

[0066] S02, using the laser amplification module 7 to perform first amplification on the incident light 1 in the first optical path, and returning the depolarized laser after the first amplification along the closed-loop first optical path to the first polarization beam splitter 2, and splitting the depolarized laser into first component light and second component light under the beam splitting action of the first polarization beam splitter 2 and entering the second optical path and the third optical path, respectively.

[0067] In one embodiment, the first component light and the second component light are P-state polarized component light and S-state polarized component light, respectively.

[0068] S03, adjusting the first polarization rotator 3 to be in a rotating state, so that the polarization state of the first component light in the second optical path changes, and the first component light after the change of the polarization state reaches the third polarization beam splitter 6 along the second optical path;

[0069] S04, the second component light in the third optical path reaches the third polarization beam splitter 6 along the second optical path after the change of the polarization state by the second polarization rotator 12, the phase retarder 13 is adjusted, and the optical path difference between the second component light and the first component light when reaching the third polarization beam splitter 6 meets a preset condition.

[0070] In a preferred embodiment, the preset condition refers to an optical path difference of zero or an optical path difference of an integer multiple of the wavelength of the laser to be amplified.

[0071] S05, combining the first component light after the change of the polarization state with the second component light, using the laser amplification module 7 to perform second amplification on the combined light beam, and returning the twice-pass amplified light beam along the first optical path to the first polarization beam splitter 2;

[0072] ​S06, if the light beam needs to continue to be amplified, the rotation state of the first polarization rotator 3 is maintained, the light beam repeats the first path and the second path, until the light beam needs to stop continuing to be amplified after the even-numbered path amplification, that is, the last path amplification, the first polarization rotator 3 is adjusted to a non-rotatory state, the light beam is transmitted to the second polarization beam splitter 4 to output, and the outgoing light 14 is obtained, which is opposite to the polarization state of the incident light 1 and is subjected to the self-compensation of depolarization.

[0073] For the linearly polarized light of the last path after the even-numbered path amplification, since the polarization state of the linearly polarized light is just opposite to the polarization state of the incident light at this time, the incident direction thereof is also opposite with respect to the same optical path device (the same incident node), and therefore when the amplified polarized light returns to the incident position, the first polarization beam splitter 2 at the incident position transmits the linearly polarized light according to the outgoing direction thereof and transmits the linearly polarized light to the second polarization beam splitter 4 at the next corresponding node to guide the linearly polarized light out (the incident linearly polarized light is transmitted by the first polarization beam splitter 2 in the incident direction due to the different polarization states), so that the incident light and the outgoing light are different in axis, and the isolation safety of the front-stage system is ensured.

[0074] Compared with the prior art, the multi-path multi-stage amplification and depolarization self-compensation system and method provided in the embodiment of the application innovatively constructs a multi-ring optical path, wherein the main optical path is used for amplification, and the multi-branch optical path is used for polarization state rotation, and the image transmission is combined to enable the laser to run in the full aperture in theory, and the depolarization of the linearly polarized light after the even-numbered path through the amplifier is self-compensated, and the whole optical path is unidirectional running and can naturally avoid the back laser to avoid the damage of the front-stage system by the high-energy back laser. Meanwhile, the laser output near-field modulation can be reduced, and the controllable multi-stage amplification is realized. The technical scheme provided by the application makes up for the shortcomings of the small spot aperture and the poor depolarization compensation effect in the commonly used multi-stage amplification optical path, is suitable for the depolarization compensation of most multi-stage amplification optical paths, and is especially suitable for the high-frequency and high-energy system.

[0075] The above only describes the preferred embodiments 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 the drawings, or direct / indirect application in other related technical fields within the concept of the application is included in the patent protection scope of the application.

[0076] Any feature disclosed in the specification (including any accompanying claims, abstract) can be replaced by other equivalent or similar features unless specifically stated otherwise. That is, each feature is only an example of a series of equivalent or similar features unless specifically stated.

Claims

1. A multi-path multi-pass amplification depolarization self-compensated system, characterized in that, The multi-path multi-pass amplification depolarization self-compensation system comprises a first optical path, a second optical path and a third optical path between a first node and a third node, wherein the second optical path further comprises a second node; the transmission direction of the first optical path is from the third node to the first node, and the transmission direction of the second / third optical path is from the first node to the third node; The first node is used for guiding the polarization state incident light; the second node is used for guiding the outgoing light or guiding the non-outgoing light, and the incident light is different from the outgoing light in the axis; the third node is used for guiding the non-outgoing light into the first optical path, and splitting and / or combining the light beams; The first optical path is a main optical path for multi-pass amplification and closed-loop transmission of laser; the first optical path comprises at least one laser amplification module for multi-pass amplification of laser; when the odd number of passes is amplified, the laser to be amplified is linearly polarized light, and the amplified laser is depolarized to obtain the odd number of passes of the non-linear polarization state of the depolarized laser; when the even number of passes is amplified, the laser to be amplified is depolarized laser, and the amplified laser realizes depolarization self-compensation to obtain the linearly polarized light after the even number of passes; the non-linear polarization state of the depolarized laser after the odd number of passes is split at the first node to obtain the first component light and the second component light; The second optical path is used for transmitting the linearly polarized light to the first optical path, and transmitting the first component light of the depolarized laser to the first optical path after polarization state rotation; The third optical path is used for transmitting the second component light of the depolarized laser to the first optical path after polarization state rotation, thereby realizing depolarization self-compensation; The second optical path further comprises a first polarization selection module between the first node and the second node, which is used for selecting whether to perform polarization state rotation processing on the light beam according to the amplification pass number and the light beam state: when the light beam passing through the first polarization selection module is the first pass or the last pass, the first polarization selection module is adjusted to a non-rotating state; otherwise, the first polarization selection module is adjusted to a rotating working state; The third optical path further comprises a second polarization selection module, which always maintains a rotating working state, and is used for rotating the polarization state component light passing through the module by 90 degrees to change the polarization state thereof.

2. A multi-path multi-pass amplification depolarization self-compensated system according to claim 1, characterized in that, The first node, the second node and the third node are polarization beam splitters.

3. A multi-path multi-pass amplification depolarization self-compensated system according to claim 1, characterized in that, The two component lights after splitting enter the second optical path and the third optical path respectively for polarization state rotation, the two component lights after rotation are combined and amplified again on the first optical path to obtain the linearly polarized light after the even number of passes.

4. A multi-path multi-pass amplification depolarization self-compensated system according to claim 3, characterized in that, The second optical path or the third optical path comprises at least one phase retarder, which is used for making the optical path difference of the two component lights in the second optical path and the third optical path be zero or an integer multiple of the wavelength of the laser to be amplified.

5. A multi-path multi-pass amplification depolarization self-compensation method, characterized in that, The method comprises: S01, adjusting the first polarization selection module to a non-rotating state, guiding the polarization state incident light from the first node, and reaching the third node and entering the first optical path along the second optical path; S02, amplifying the incident light by using the laser amplification module in the first optical path for the first time, returning the depolarized laser after the first amplification to the first node along the first optical path, and splitting into the first component light and the second component light under the splitting action of the first node, and entering the second optical path and the third optical path respectively; S03, adjusting the first polarization rotator to be in an optically active state, so that the polarization state of the first component light in the second optical path is changed, and the first component light after the change of the polarization state reaches the third node along the second optical path; S04, making the second component light after the change of the polarization state by the second polarization selection module reach the third node, and adjusting the phase retarder so that the optical path difference between the second component light and the first component light when reaching the third node meets a preset condition; S05, combining the first component light after the change of the polarization state and the second component light, using the laser amplification module to amplify the combined light beam for a second time, and returning the light beam after the amplification for a second time along the first optical path to the first node; S06, if the light beam needs to continue to be amplified, maintaining the working state of the first polarization selection module, so that the light beam repeats the first-stage optical path, until the light beam needs to stop continuing to be amplified, and the light beam is transmitted to the second node for output, obtaining the outgoing light which is opposite to the polarization state of the incident light and has undergone self-compensation of depolarization.

6. A multi-path multi-pass amplification depolarization self-compensation method according to claim 5, characterized in that, When the light beam stops continuing to be amplified in step S06, the first polarization selection module is adjusted to be in a non-optically active state, so that the light beam is not changed in the polarization state and is directly transmitted to the second node.

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