CN115733039A - Multi-optical-path multi-path amplification depolarization self-compensation system and method - Google Patents

Abstract

The invention discloses a multi-light-path multi-pass depolarization self-compensation system and a method, and relates to the field of repetition frequency high-energy lasers. The multi-path amplification depolarization self-compensation system comprises a first optical path, a second optical path and a third optical path; the first light path is a main light path for multi-pass amplification and closed-loop transmission; the second optical path and the third optical path are used for respectively rotating the polarization state of component light of the depolarization laser to be amplified in an even-numbered path, so that depolarization self-compensation is realized. Compared with the prior art, the depolarization self-compensation scheme provided by the invention enables the laser to be subjected to self-compensation in even-numbered passes through the amplifier for depolarization, the whole optical path can naturally avoid the reverse laser in one-way operation, the damage of a front stage by the high-energy reverse laser is avoided, the near-field modulation of the laser output can be reduced, the controllable multi-pass amplification is realized, the defects of small light spot caliber and poor depolarization compensation effect in the conventional multi-pass amplification optical path are overcome, and the depolarization self-compensation scheme is suitable for depolarization compensation of the multi-pass amplification optical path of a repetition frequency high-energy system.

Description

Multi-optical-path multi-path amplification depolarization self-compensation system and method

Technical Field

The invention relates to the field of repetition frequency high-energy lasers, and particularly discloses a multi-path multi-pass depolarization self-compensation system and a compensation method.

Background

In the prior art, a multi-pass amplifying optical path of a laser system which operates at high energy and repeated frequency mainly follows a multi-pass optical path which is widely applied to a laser system which operates at low energy or at a single time. High energy requires large-aperture beam amplification, so that off-axis multi-pass and on-axis two-pass or multi-pass schemes used conventionally suffer from the problem of laser depolarization. On one hand, stray light control difficulty can be caused by laser depolarization, and on the other hand, near-field light intensity distribution modulation is caused, so that the output capacity of the system is reduced, and the risk of damage to optical elements of the system is increased. In addition, in the existing scheme, the off-axis optical path also has the problem of low beam duty ratio; coaxial multipass comparison depends on the purity of a polarization state, once depolarization occurs, if the depolarization effect caused by the thermal stress birefringence effect cannot be effectively compensated, the stray light is difficult to control, laser self-excitation amplification can be caused, the actual isolation ratio between stages is reduced, and the like, so that reverse depolarization is caused and the damage to the previous stage is caused.

Disclosure of Invention

The invention aims to: in view of the above problems, the present invention provides a multi-path multi-pass amplification depolarization self-compensation system and method, which can achieve controllable pass amplification of laser light to be amplified, and also can achieve depolarization self-compensation of the amplified laser light, and at the same time, can make the input light and the output light not coaxial, thereby avoiding damage to optical path elements.

The technical scheme adopted by the invention is as follows:

a multi-optical-path multi-path amplification depolarization self-compensation system comprises a first optical path, a second optical path and a third optical path, wherein the first optical path, the second optical path and the third optical path are positioned between a first node and a third 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 light path is a main light path used for carrying out multi-pass amplification and closed-loop transmission on main laser; the second light path is used for transmitting the linearly polarized light to the first light path, and transmitting the component light of the depolarization laser to the first light path for beam combination after polarization state rotation; the third light path is used for transmitting the other component light of the depolarization laser light to the first light path for beam combination after polarization state rotation, so that depolarization self-compensation is realized.

On the other hand, the invention also provides a corresponding multi-light-path multi-path amplification depolarization self-compensation method, which is mainly used for carrying out multi-path amplification and depolarization self-compensation based on the depolarization self-compensation, and light beams in different light paths are converted between different polarization states by adjusting the optical rotation state of the first polarization selection module, so that the light beams can complete controllable multi-path amplification and depolarization self-compensation in a closed loop light path system.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

(1) Compared with the prior art, the multi-path amplification depolarization self-compensation system and the multi-path amplification depolarization self-compensation method provided by the invention construct a multi-annular light path, wherein a main light path is used for amplification, a multi-branch light path is used for polarization state rotation, laser can theoretically run in a full aperture in the light path by combining image transmission, depolarization of linearly polarized light is self-compensated after passing through an amplifier in an even number path, the whole light path is in one-way operation, anti-laser can be naturally avoided, and damage of a front stage by high-energy anti-laser is avoided.

(2) The multi-path amplification depolarization self-compensation scheme provided by the invention can reduce near-field modulation of laser output, realize controllable multi-path amplification, make up for the defects of small light spot caliber and poor depolarization compensation effect in the conventional multi-path amplification light path, is suitable for depolarization compensation of most multi-path amplification light paths, and is particularly suitable for a repetition frequency high-energy system.

Drawings

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a graph of the polarization state decomposition of laser light and refractive index ellipsoid relationship under the effect of birefringence in an amplifier;

FIG. 2 is a schematic structural diagram of a multi-optical path multi-pass amplification depolarization self-compensation system according to the present invention;

FIG. 3 is a diagram of an optical path structure according to an embodiment of the present invention;

FIG. 4 is a diagram of an optical path structure according to another embodiment of the present invention;

FIG. 5 is a diagram of an optical path structure according to another embodiment of the present invention;

fig. 6 is a light path structure diagram according to another embodiment of the present invention.

In the figure: n1: a first node; n2: a second node; n3: a third node; r1: a first optical path; r2: a second optical path; r3: a third optical path; 1: incident light; 2: a first polarizing beam splitter; 3: a first polarization rotator; 4: a second polarizing beam splitter; 5: a first reflector; 6: a third polarization beam splitter; 7: a laser amplification module; 8: a second reflector; 9: a third reflector; 10: an image transmitter; 11: a fourth reflector; 12: a second polarization rotator; 13: a phase retarder; 14: emergent light; 15: a fifth reflector; 16: a sixth reflector.

Detailed Description

In order to make the technical solutions of the present invention better understood, the following description of the technical solutions of the present invention with reference to the accompanying drawings of the present invention is made clearly and completely, and other similar embodiments obtained by a person of ordinary skill in the art without any creative effort based on the embodiments in the present application shall fall within the protection scope of the present application.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; the connection can be mechanical connection, electrical connection, physical connection or wireless communication connection; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the optical path of the repetition frequency high-energy high-heat laser system, when polarized light passes through a laser amplifying device, due to the presence of a thermal induced birefringence effect and a holding stress applied to a gain medium, the polarization state can be changed slightly, and laser depolarization is generated. The description will be given by taking S-state polarized light as an incident light as an example, as shown in fig. 1. In fig. 1, OA is the polarization direction of incident light, and OC and OD are respectively the major and minor axes of the index ellipsoid due to thermal induced birefringence at position O. The incident polarized light is split into two components, radial OB and tangential AB, whose optical paths to travel in the amplifier will be OC × L and OD × L, respectively, where L is the path length traveled by the incident light in the gain medium in the laser amplification device. When the light beam passes through the laser head, the radial and tangential components are combined into elliptical polarized light, so that the S polarization state of the laser relative to the incident light is depolarized.

In order to enable the depolarized laser after multipass amplification to realize self-compensation, the embodiment of the invention provides a multipass depolarized self-compensation system and a compensation method, and specifically describes the structure and operation mode of the system in detail.

Example 1

As shown in fig. 2, fig. 2 is a schematic diagram of a multi-path multi-pass amplification depolarization self-compensation system, which can be used in a laser oscillator and a laser amplifier. The multi-path multi-amplification depolarization self-compensation system comprises a first light path R1, a second light path R2 and a third light path R3 which are positioned between a first node N1 and a third node N3, wherein the second light path R2 further comprises a second node N2. The third optical path R3 has a transmission direction between the first node N1 and the third node N3 opposite to the transmission direction of the first/second optical paths (R1, R2).

The first node N1 is used for introducing incident light in a polarization state. The second node N2 is used for leading out emergent light or leading in non-emergent light (i.e. the emergent light is led out after the last amplification, and only the light beam passes through the other optical paths and enters the next optical path). Because the incident position and the emergent position of the light beam are different, the incident light and the emergent light are not coaxial, and the damage of the laser in the system to the system is avoided. And the third node N3 is used for guiding non-emergent light into the first light path R1. Meanwhile, according to a specific optical path structure, depolarization laser is subjected to beam splitting and beam combining at any one or two of the first node N1, the second node N2 and the third node N3.

The first optical path R1 is a main optical path for performing multi-pass amplification and closed-loop transmission on main laser light. The second optical path R2 is used for directly transmitting the linearly polarized light amplified by the odd-numbered path to the first optical path R1 for amplification, and transmitting the component light of the depolarized laser amplified by the even-numbered path to the first optical path R1 for beam combination and amplification after polarization state rotation. The third light path R3 is used for transmitting the other component light of the depolarization laser light to the first light path R1 after the polarization state rotation, combining and amplifying the other component light, and therefore depolarization self-compensation is achieved.

The second optical path R2 further includes a first polarization selection module located between the first node N1 and the second node N2, and configured to select whether to perform polarization rotation processing on the light beam according to the amplification degree number and the state of the light beam: when the light beam passing through the first polarization selection module is amplified in a first pass or a last pass, the first polarization selection module is adjusted to be in a non-optical rotation state; besides, when the light beam is amplified in the middle range (i.e. not in the first range or the last range), the first polarization selection module is adjusted to be in the optical rotation working state.

The third optical path R3 further includes a second polarization selection module, and the second polarization selection module always maintains an optical rotation working state, and is configured to rotate the polarized light passing through the module by 90 degrees to change the polarization state thereof.

In a preferred embodiment, as shown in fig. 3, 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 transmitter 10, and a fourth reflector 11.

The first polarization beam splitter 2 is used for guiding the multi-path amplified front-stage incident light 1 into the system on a first optical path, performing polarization beam splitting on the depolarization laser after odd-path amplification, and transmitting or reflecting the linearly polarized light transmitted back in a closed loop after even-path amplification. It should be noted that, in this embodiment, the light beam is amplified once from the injection position along the closed-loop optical path and returns to the injection position, which is the amplification of one optical path.

The third polarization beam splitter 6 is configured to directly transmit or reflect incident light for odd-path amplification, and guide polarization component light from different optical paths for even-path amplification into the first optical path R1 for amplification after polarization combining.

The laser amplification module 7 is used for carrying out multi-pass amplification on main laser: when the odd-path amplification is carried out, the laser to be amplified is linearly polarized, and the amplified laser is depolarized to obtain depolarized laser in a nonlinear polarization state after the odd-path amplification; when the even-range is amplified, the laser to be amplified is non-linear polarized light, and the amplified laser realizes depolarization self-compensation to obtain the even-range amplified linear polarized light.

And the closed-loop transmission module consisting of the second reflector 8, the third reflector 9, the image transmitter 10 and the fourth reflector 11 is used for transmitting the amplified light beam to the injection position of the incident light 1, namely the first polarization beam splitter 2 in a closed loop. The reflectors are used for reflecting light beams, a plurality of reflectors can form a reflector group, laser can return in a closed loop by combining a plurality of image transmitters 10, and meanwhile, theoretically, the laser can run in a full aperture in a light path.

In one embodiment, the number of reflectors may not be limited, and the reflectors may be mirrors, prisms, or other elements that may function as a reflector. The image relay 10 may be a 4f imaging system or a single lens imaging system.

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

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 after polarization splitting is performed on depolarization laser at the first polarization beam splitter 2, the two component lights respectively rotate in a polarization state along the second light path R2 and the third light path R3 and then are combined at the third polarization beam splitter 6. In addition, the optical path of the closed loop optical path formed by the second optical path R2 and the third optical path R3 needs to satisfy the image transfer relationship, so that the transmission of the laser light follows the image transfer principle.

The first polarization rotator 3 is an active optical rotation device, such as an electro-optical switch or the like. The second polarization rotator 12 may be an active polarization rotator, or may be a passive polarization rotator, such as a quartz rotor, a nonlinear crystal rotor, a half-wave plate, or a pyramid inverter mirror set.

The phase retarder 13 is configured to make an optical path difference between the component light transmitted in the second optical path R2 and the third optical path R3 be zero, or make the optical path difference be an integral multiple of a laser wavelength to be amplified. In this embodiment, the phase retarder 13 may be disposed in the second optical path R2 or the third optical path R3, so as to ensure that the optical path difference transmitted in the two optical paths satisfies the aforementioned condition.

The laser amplifier device is a module for providing gain for laser, and is used in the present invention to describe that the light beam may be depolarized after passing through the laser amplifier device for the reasons described above. In this embodiment, the laser amplifying device may refer to the laser amplifying module 7 or the image transmitter 10, or may refer to an integral module composed of the laser amplifying module 7, the second reflector 8, the third reflector 9, the image transmitter 10, and the fourth reflector 11. In another preferred embodiment, the laser amplifier device may further be a gain amplifier device at least including a gain medium, a pump source, and the like.

The operation of the depolarization self-compensation system will be described with reference to fig. 3 by taking the incident light 1 as S-state polarized light as an example. In the initialized state, the first polarization beam splitter 2 guides the S-state polarized light of the first pass to the second optical path to the first polarization rotator 3, and at this time, the first polarization rotator 3 only serves as a transmission element, and the polarization state of the incident light is not changed. The S-state polarized light passes through the first polarization rotator 3, then passes through the second polarization beam splitter 4 and the first reflector 5, then reaches the third polarization beam splitter 6, and enters the first light path R1.

In the first optical path, the S-state polarized light is subjected to first-pass amplification by the laser amplification module 7 and then subjected to depolarization, and the depolarized laser light (for convenience, the laser light is still independently transmitted by radial and tangential components) sequentially passes through the second reflector 8, the third reflector 9, the image transmitter 10 and the fourth reflector 11 along the closed-loop first optical path R1 and then reaches the first polarization beam splitter 2 again. At this time, the light beam starting the second optical path is split into P component light and S component light, which are different in radial and tangential components, by the splitting action of the first polarization splitter 2, and enters the second optical path R2 and the third optical path R3, respectively:

the P component light enters the second optical 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 be an optical rotation state, and the P component light is rotated, so that the P component light is changed into S component light, and then the S component light reaches the third polarization beam splitter 6 again after passing through the second polarization beam splitter 4 and the first reflector 1;

the other side of the light beam entering the third optical path simultaneously is an S component light beam, and when the S component light beam reaches the second polarization rotator 12, since the device of the second polarization rotator 12 always keeps an optical rotation working state in the working process of the whole laser system, the S component light beam passes through the second polarization rotator 12 and then becomes a P component light beam, and the P component light beam enters the phase retarder 13 again. Through the precise adjustment of the phase retarder 13, it is ensured that when the component light of the second optical path and the component light of the third optical path reach the third polarization beam splitter 6, the optical path difference of the two component light is zero or an integral multiple of the wavelength of the laser light to be amplified.

At the position of the third polarization beam splitter 6, the two component lights with different polarization states, that is, the S component light from the second optical path R2 and the P component light from the third optical path R3, are combined in an aplanatic beam combining manner, and finally the effect of combining the beams is completely equal to the effect of combining the P-state polarized light and the S-state polarized light at the first polarization beam splitter 2 after they are rotated by 90 degrees, respectively. Because the optical path difference of the two polarization state component lights of the combined beam is not changed, in order to display the depolarization compensation effect, the combined beam is still independently transmitted and analyzed according to the tangential polarization state and the radial polarization state.

After the combined laser light enters the laser amplification module 7 again, the radial component OB will be transmitted along a path with a refractive index of OC due to the rotation of 90 degrees of the polarization state of the light; the tangential component AB will be transmitted along the path with refractive index OD, and after the second amplification by 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 passing through the laser amplification module 7 twice, the phase difference between the radial component and the tangential component becomes an integral multiple of 2 pi, the only change is that the polarization states of the radial component and the tangential component are both rotated by 90 degrees, and the finally synthesized polarization state is also linearly polarized light, i.e. the laser obtained after the final twice amplification is P-state linearly polarized light which is rotated by 90 degrees relative to the first pass S-state incident light 1.

In other words, it can be seen that, in the working process of the depolarization self-compensation system provided in the embodiment of the present invention, when the light beam is amplified by even number of passes each time, that is, after passing through the laser amplification module 7 for even number of times, the output light beam is pure P-state linearly polarized light, so that the optical path required to complete one depolarization self-compensation in the embodiment of the present invention is an even number of passes.

The P-state linearly polarized light amplified by the even-numbered path from the laser amplification module 7 enters the second optical path R2 after reaching the first polarization beam splitter 2 along the first optical path R1 again, and reaches the first polarization rotating device 3 again, and at this time, the working state of the first polarization rotating device 3 is adjusted according to whether the light beam is output:

if the system needs to continuously amplify the light beam in multiple passes, the first polarization rotating device 3 continuously keeps the rotating working state, at the moment, the P polarized light is changed into S polarized light again, and the light path of the first pass or the odd pass is repeated;

when the system needs to output a light beam, the first polarization splitter 3 is adjusted to transmit only the working state (i.e. the non-rotational working state) without changing the polarization state, so that the P-state linearly polarized light after twice amplification or even-order amplification is led out after passing through the first polarization rotator 3, for example, in this embodiment, led out through the second polarization splitter 4, and the outgoing light 14 with twice amplification and depolarization and self-compensation is obtained.

Example 2

For the depolarization self-compensation system provided by the application, the polarization incident light 1 may be P-polarization state light or S-polarization state light. In the depolarization self-compensation system shown in fig. 3, when the incident light 1 to be amplified is S-state polarized light, the light is injected from the first polarization beam splitter 2, the first polarization beam splitter 2 is also used for splitting polarization, and finally the emergent light 14 after even-path amplification and depolarization self-compensation is completed is output from the second polarization beam splitter 4; the incident light 1 may be P-state polarized light and injected from the second polarization beam splitter 4, and the third polarizing element 6 is used for polarization splitting at this time, and the emergent light 14 after even-order amplification and depolarization self-compensation is finally completed 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 may be switched, and the input and output directions may also be switched.

In this embodiment, the optical path is described by taking the incident light 1 as P-state polarized light as an example, as shown in fig. 4, in the initialization state, the second polarization beam splitter 4 (corresponding to the first node N1 in this embodiment) guides the P-state polarized light of the first pass into the second optical path to the first polarization rotator 3, and at this time, the first polarization rotator 3 only serves as a transmission element and does not change the polarization state of the incident light. After passing through the first polarization rotator 3, the P-state polarized light passes through the first polarization beam splitter 2 (corresponding to the second node N2 in this embodiment), and then sequentially reaches the laser amplification module 7 along the fourth reflector 11, the image transmitter 10, the third reflector 9, and the second reflector 8, and then completes the first amplification, and the depolarization laser light after the first amplification performs polarization beam splitting at the third polarization beam splitter 6, and starts the second optical path.

At this time, the light beam starting the second optical path enters the second optical path and the third optical path respectively according to the respective different P component and S component of the radial component and the tangential component under the splitting action of the third polarization beam splitter 6:

the light entering the second optical path is S-component light, and when the S-component light reaches the first polarization rotator 3 along the first reflecting mirror 5 and the second polarization beam splitter 4, the working state of the first polarization rotator 3 is adjusted to be an optical rotation state, so that the S-component light is changed into P-state polarized light, and then the P-state polarized light reaches the first polarization beam splitter 2 again;

the other side of the light beam simultaneously enters the third light path and is P component light, when the P component light sequentially passes through the phase retarder 13 and the second polarization rotator 12, polarization state rotation and precise adjustment are completed, and when the light beams of the second light path and the third light path reach the first polarization beam splitter 2, the optical path difference between the second light path and the third light path is zero or integral multiple of the laser wavelength to be amplified.

At this time, similarly, at the position of the first polarization beam splitter 2, the two component lights with different polarization states are combined, and after the combination, the light continues to enter the laser amplification module 7 along the first light path to complete secondary amplification, and is emitted from the first polarization beam splitter 2, so as to obtain the emergent light 14. The finally secondarily amplified outgoing light 14 is S-state polarized light rotated by 90 degrees with respect to the first-pass P-state incident light 1.

Example 3

Fig. 5 is a schematic structural diagram of another preferred embodiment of the present invention, as shown in the drawing, wherein an incident light 1 in a polarization state enters from the first polarization beam splitter 2 and is guided into the laser amplification module 7 in the first optical path from the second optical path for first-pass amplification, the amplified depolarization laser passes through the closed-loop transmission module composed of the second reflector 8, the third reflector 9 and the image transmitter 10 to be split at the third polarization beam splitter 6, after splitting, two component lights respectively enter the second optical path and the third optical path to undergo polarization rotation, and after being combined at the second polarization beam splitter 4, the amplified laser is amplified again, and finally, linearly polarized light after even-pass amplification is led out from the second polarization beam splitter 4, so as to obtain an emergent light 14 with multi-pass amplification and depolarization self-compensation.

In this embodiment, the first polarization rotator 3 and the second polarization rotator 12 may preferably use PEPC electro-optical switches with large apertures as polarization selection modules for controlling polarization state change, and are more suitable for high-frequency-repetition high-energy devices.

It should be noted that, in different embodiments, the number of the reflecting mirrors and the number of the image transmitters on each optical path may be increased or decreased according to the optical path requirement, so that the optical path satisfies the image transmission relationship and realizes multi-pass amplification and depolarization self-compensation. Meanwhile, the same parts as the principles in the foregoing embodiments are not described in detail in this embodiment.

Example 4

Fig. 6 is a schematic structural diagram of another preferred embodiment of the present invention, as shown in the drawing, wherein a polarization state incident light 1 enters from a first polarization beam splitter 2 and enters a first optical path from a second optical path through a second polarization beam splitter 4 to perform a first-pass amplification, an amplified depolarization laser beam is split at a third polarization beam splitter 6, two split component lights respectively enter the second optical path and the third optical path to perform polarization state rotation, and are combined at the second polarization beam splitter 4 to be amplified again, and finally, a linearly polarized light beam after even-pass amplification is guided out from the second polarization beam splitter 4, so as to obtain an emergent light 14 with multi-pass amplification and depolarization self-compensation.

It should be noted that in this embodiment, the number and the positions of the reflecting mirrors and the image transmitters on each optical path may also be set according to the optical path requirement, so that the optical path satisfies the image transmission relationship and realizes the multi-pass amplification and depolarization self-compensation. Meanwhile, the same parts as the principles in the foregoing embodiments are not described in detail in this embodiment.

Example 5

The implementation is a multi-optical path multi-pass amplification depolarization self-compensation method, and the method is performed based on the system in any one of the embodiments. Taking the optical path structure of the system shown in fig. 3 of embodiment 1 as an example, the method includes the following steps:

s01, adjusting the first polarization rotator 3 to be in a non-rotation state and the second polarization rotator 12 to be in a rotation state, guiding the polarization state incident light 1 from the first polarization beam splitter 2, then reaching the third polarization beam splitter 6 along the second light path and entering the first light path;

and S02, performing primary amplification on the incident light 1 in the first light path by using the laser amplification module 7, returning the polarization-removed laser after the primary amplification to the first polarization beam splitter 2 along the closed-loop first light path, and splitting the laser into first component light and second component light under the beam splitting action of the first polarization beam splitter 2 and respectively entering the second light path and the third light path.

In one embodiment, the first component light and the second component light are P-state polarization component light and S-state polarization component light, respectively.

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 light path is changed, and the first component light after the polarization state change reaches the third polarization light splitting device 6 along the second light path;

and S04, the second component light of which the polarization state is changed by the second polarization rotator 12 in the third light path reaches the third polarization light splitting device 6 along the second light path, the phase retarder 13 is adjusted, and the optical path difference value of the two component lights meets a preset condition when the second component light and the first component light reach the third polarization light splitting device 6.

In a preferred embodiment, the preset condition is that the optical path difference is zero or that the optical path difference is an integral multiple of the wavelength of the laser to be amplified.

S05, combining the first component light and the second component light after the polarization state is changed, performing second amplification on the combined light beam by using the laser amplification module 7, and returning the light beam after the double-path amplification to the first polarization beam splitter 2 along the first light path;

and S06, judging whether the light beam needs to be amplified or not, if the light beam needs to be amplified continuously, keeping the rotation state of the first polarization rotator 3, enabling the light beam to repeat the light paths of the first pass and the second pass, and adjusting the first polarization rotator 3 to be in a non-optical rotation state after the light beam needs to be amplified in the last pass until the light beam needs to be amplified continuously after the even-number pass is amplified, so that the light beam is transmitted to the second polarization beam splitter 4 to be output, and emergent light 14 which is opposite to the polarization state of the incident light 1 and is subjected to depolarization self-compensation is obtained.

For the linearly polarized light of the last path after even-path amplification, because the polarization state of the linearly polarized light is just opposite to the polarization state of the incident light at the time, the incident direction is also opposite to that of the same light path device (the same incident node), and therefore when the amplified polarized light returns to the incident position, the amplified polarized light can be transmitted by the first polarization splitting sheet 2 at the incident position according to the emergent direction thereof and then is led out after being transmitted by the second polarization splitting sheet 4 at the next corresponding node (the incident polarized light can be transmitted by the first polarization splitting sheet 2 in the incident direction due to different polarization states), so that different axes of the incident light and the emergent light are realized, and the isolation safety of a front-stage system is ensured.

Compared with the prior art, the multi-path amplification depolarization self-compensation system and method provided by the embodiment of the invention creatively construct a multi-ring-shaped optical path, wherein the main optical path is used for amplification, the multi-branch optical path is used for polarization state rotation, the laser can theoretically run in the optical path in a full aperture manner by combining image transmission, the depolarization of linearly polarized light can be self-compensated after passing through an amplifier in an even number path, the whole optical path is in unidirectional operation and can naturally perform laser inversion, and the front stage is prevented from being damaged by high-energy laser inversion. Meanwhile, the near field modulation of laser output can be reduced, and controllable multi-pass amplification is realized. The technical scheme provided by the invention overcomes the defects of small light spot caliber and poor depolarization compensation effect in the conventional multi-pass amplification light path, is suitable for depolarization compensation of most multi-pass amplification light paths, and is particularly suitable for a repetition frequency high-energy system.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Any feature disclosed in this specification (including any accompanying claims, abstract) may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.

Claims (10)

1. The multi-path multi-pass amplification depolarization self-compensation system is characterized by comprising a first light path, a second light path and a third light path which are positioned between a first node and a third node, wherein the second light path also 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 node is used for introducing polarization state incident light; the second node is used for leading out emergent light or leading in non-emergent light, and the incident light and the emergent light are not coaxial; the third node is used for splitting and/or combining the light beams;

the first light path is a main light path used for carrying out multi-pass amplification and closed-loop transmission on laser; the second light path is used for transmitting the linearly polarized light to the first light path, and transmitting the component light of the depolarization laser to the first light path for beam combination after polarization state rotation; the third light path is used for transmitting the other component light of the depolarization laser light to the first light path for beam combination after polarization state rotation, so that depolarization self-compensation is realized.

2. The multi-optical path multi-path amplification depolarization self-compensation system of claim 1, wherein the second optical path further comprises a first polarization selection module located between the first node and the second node, and configured to select whether to perform polarization rotation processing on the light beam according to the amplification path number and the state of the light beam:

when the light beam passing through the first polarization selection module is amplified in a first pass or a last pass, the first polarization selection module is adjusted to be in a non-optical rotation state; otherwise, the first polarization selection module is adjusted to be in an optical rotation working state.

3. The multi-optical path multi-path amplification depolarization self-compensation system of claim 2, wherein the third optical path further comprises a second polarization selection module, the second polarization selection module always keeps an optical rotation operation state, and the polarization state component light passing through the second polarization selection module is rotated by 90 degrees to change the polarization state of the polarization state component light.

4. The multi-optical path multi-pass amplification depolarization self-compensation system of claim 3, wherein the first optical path comprises at least one laser amplification module for multi-pass amplification of laser light.

5. The multi-optical-path multi-path amplification depolarization self-compensation system of claim 4, wherein when the odd-path amplification is performed, the laser to be amplified is linearly polarized light, and the amplified laser is depolarized to obtain depolarized laser in a non-linear polarization state after the odd-path amplification; when the even-numbered path is amplified, the laser to be amplified is depolarization laser, and the amplified laser realizes depolarization self-compensation to obtain linearly polarized light after the even-numbered path is amplified.

6. The multi-path multi-amplification depolarization self-compensation system of claim 5, wherein the first node, the second node and the third node are polarization splitters.

7. The multi-path amplification depolarization self-compensation system of claim 5, wherein odd-path amplified depolarization laser light in a non-linear polarization state is split, the split two paths of component light enter the second optical path and the third optical path respectively to perform polarization rotation, and the two paths of component light after optical rotation are combined and amplified again on the first optical path to obtain even-path amplified linearly polarized light.

8. The multi-optical path multi-pass amplification depolarization self-compensation system of claim 7, wherein the second optical path or the third optical path comprises at least one phase retarder, for making the optical path difference of the two component lights transmitted in the second optical path and the third optical path be zero or the optical path difference be an integer multiple of the wavelength of the laser to be amplified.

9. A multi-optical path multi-pass amplification depolarization self-compensation method is characterized by comprising the following steps:

s01, adjusting the first polarization selection module to be in a non-optical rotation state, guiding the polarization state incident light from the first node, then reaching the third node along the second light path and entering the first light path;

s02, utilizing a laser amplification module to amplify incident light for the first time in a first light path, returning the polarization-reversed laser after the first amplification to a first node along the first light path, dividing the laser into first component light and second component light under the beam splitting action of the first node, and respectively entering a second light path and a third light path;

s03, adjusting the first polarization rotator 3 to be in an optical rotation working 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 polarization state change reaches a third node along the second optical path;

s04, enabling the second component light of which the polarization state is changed by the second polarization selection module in the third light path to reach a third node, and adjusting the phase retarder to enable the optical path difference value of the second component light and the first component light to meet a preset condition when the second component light and the first component light reach the third node;

s05, combining the first component light and the second component light after the polarization state is changed, performing second amplification on the combined light beam by using a laser amplification module, and returning the light beam after twice-path amplification to a first node along a first light path;

and S06, if the light beam needs to be amplified continuously, keeping the working state of the first polarization selection module, and enabling the light beam to repeat the light path of the first pass until the light beam needs to be amplified continuously after the even-pass amplification, and enabling the light beam to be transmitted to a second node for output to obtain emergent light which is opposite to the polarization state of incident light and subjected to depolarization self-compensation.

10. The multi-path multi-amplification depolarization self-compensation method of claim 9, wherein in step S06, when the light beam stops amplifying, the first polarization selection module is adjusted to be in a non-optical rotation state, so that the light beam is transmitted to the second node without being changed in polarization state.

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