CN109143572B

CN109143572B - Beam combiner for pulse laser, pulse beam combining laser system and method

Info

Publication number: CN109143572B
Application number: CN201811084011.7A
Authority: CN
Inventors: 陈绍武; 冯国斌; 王飞; 王振宝; 张磊; 赵海川; 王平
Original assignee: Northwest Institute of Nuclear Technology
Current assignee: Northwest Institute of Nuclear Technology
Priority date: 2018-09-17
Filing date: 2018-09-17
Publication date: 2021-05-25
Anticipated expiration: 2038-09-17
Also published as: CN109143572A

Abstract

The present invention particularly relates to a beam combiner for pulsed laser and a pulsed beam combining laser system and method. In order to overcome the defects in the existing pulse sequential beam combination, the required transmission type element is difficult to adapt to the long-time high-power laser, or other beam combination methods will affect the quality of the laser beam after the combination. The beam combiner of the pulsed laser includes at least two shifting devices arranged in sequence along the output optical path, and is arranged on the shifting device, and is used to make the pulsed laser beams can be spatially combined and output along the output optical path. A pulsed beam combining laser system includes a plurality of beam combiners, pulsed lasers and a foldback mirror, emits laser light according to a set time sequence, and is folded and incident on a reflector through the foldback mirror to form a combined beam of laser light. A method for combining pulsed laser beams, comprising the following steps: 1) the pulsed laser light is reflected by a mirror and then exits along an output optical path (4); 2) each reflection mirror moves into and out of the output optical path without blocking the rear.

Description

Beam combiner for pulse laser, pulse beam combining laser system and method

Technical Field

The invention belongs to the technical field of laser, and particularly relates to a beam combiner for pulse laser, a pulse beam combining laser system and a pulse beam combining laser method, which can improve laser power and repetition frequency parameters.

Background

With the continuous development and maturity of laser technology, high-power laser has wider and wider application, and the development of multiple industries is deeply influenced. The high-power laser is divided into high peak power laser (high-energy pulse laser) and high average power laser.

For high-energy pulse laser, a certain repetition frequency is required in various application fields, however, the direct increase of the repetition frequency of the high-energy pulse laser in operation can generate serious thermal effect, thereby affecting the performance of the laser, even leading to the reduction of the output pulse energy of the laser or the incapability of working. For high average power laser, higher requirements are continuously put forward on the laser output power by application requirements, and the single-path laser power is limited to be increased, so that higher average output power is difficult to realize. Therefore, it is an urgent problem to increase the repetition rate of the pulse laser for both high-energy pulse laser and high-average power laser.

The single laser realizes the output with high power, high beam quality and high efficiency characteristics, the beam quality is reduced nonlinearly due to the increase of the power, and the nonlinear relation is very complex, so that the capability of the single laser output is always limited under specific basic conditions, but the requirement of people on the output of three-high laser is endless, and the optimal path is the multi-beam synthesis technology to realize the output with higher power.

The existing beam combining method includes coherent beam combining, spectral beam combining and pulse laser time-sharing beam combining. The 'incoherent synthesis technical research of pulse laser' published in 'laser technology' in 3 months in 2015 discloses a method for realizing pulse laser beam combination based on turntable rotation, wherein lasers with different time sequences are obliquely incident to crystals with different thicknesses and then shifted, and are refracted by the crystals and then coaxially output to realize beam combination of pulse lasers, so that the aim of improving the laser output repetition frequency and average power is fulfilled. The problem with this solution is that the strong laser needs to be transmitted through the crystal, the optical element has limited ability to withstand the laser power, and it is difficult to meet the incident requirements of high power high energy laser.

The Chinese patent application 201210078189.7 discloses a pulse laser beam combining method, which provides a method of using a rotary reflector to combine a plurality of pulse laser beams with lower repetition frequency into a pulse laser beam with high repetition frequency. According to the technical effect description, all optical elements of the polygon mirror system can be reflecting optical elements, and the device can bear any high-power laser and can output any high-power pulse laser beam as long as the input laser power is high enough. However, this solution has a problem that the quality of the combined light beam is reduced due to the continuous movement of the mirror during the light emitting period of the pulsed laser, for example, when the pulse duration is in the order of milliseconds (ms), the system has an adverse effect on the popularization and application of the system due to the quality reduction of the combined light beam in the order of 1/10 caused by the continuous movement of the mirror.

Disclosure of Invention

The invention aims to overcome the defects that a transmission type element required by the existing pulse time sequence beam combination is difficult to adapt to long-time high-power laser, or other beam combination methods can influence the quality of a combined laser beam, and provides a beam combiner for pulse laser and a pulse beam combination laser system, so that the average output power and the repetition frequency of a single laser are greatly improved, the beam quality of the original laser is basically kept unchanged, and the pulse beam combiner has good power and good expandability of the number of lasers.

The technical scheme of the invention is as follows:

a beam combiner for pulse laser comprises a plurality of reflecting mirrors which are obliquely arranged along an output light path; a plurality of beams of pulse laser emitted according to a set time sequence are reflected and combined by corresponding reflectors and then emitted along the same output optical path; the reflector is arranged on the shifting device, the shifting device acts to enable the reflector to move in and out of the output light path according to a time sequence matched with the pulse laser, and in the laser emitting direction of the output light path, the reflector in the front position cannot block the emitting light beam of the reflector in the rear position.

Furthermore, in the beam combiner of the pulse laser, the shifting devices are a plurality of electrically controlled shifting stages which are controlled only according to a time sequence.

Further, in the beam combiner of the pulse laser, the electrically controlled displacement stage moves in a direction perpendicular to the output optical path.

Further, in the beam combiner of the pulse laser, the electric control displacement table is driven by a lead screw, an air cylinder or a hydraulic cylinder.

Furthermore, in the beam combiner for pulse laser, an included angle between each reflector and the output light path is 30 to 60 degrees, and an included angle between each reflector and the output light path may be different, but it is required to ensure that the pulse laser is emitted along the same output light path after being reflected by the reflectors.

Further, in the beam combiner for pulse laser, an included angle between the reflecting mirror and the output light path is 45 degrees.

A pulse beam combination laser system, characterized in that: the laser comprises n pulse lasers and n reflectors, wherein the pulse lasers emit laser according to a set time sequence and form beam combination laser emission after being incident to the reflectors, and n is a positive integer larger than 1.

Furthermore, the pulse beam combination laser system also comprises a turn-only mirror; the emergent laser is reflected back by the reflecting mirror and then enters the reflecting mirror.

A method for pulse laser beam combination is characterized by comprising the following steps:

1) pulse lasers emitted by at least two lasers according to a set time sequence are reflected by respective reflectors and then emitted out along an output light path;

2) each reflector moves in and out of the output light path according to the time sequence matched with the pulse laser, and in the laser emitting direction of the output light path, the reflector at the front position cannot block the light beam of the reflector at the rear position.

Further, the pulse laser in the step 1) is refracted by a catadioptric mirror and then reflected by a reflecting mirror.

The invention has the beneficial effects that:

1. the invention realizes the combination of the pulse laser by arranging a plurality of reflectors on the same output light path and moving out and in according to the time sequence matched with the emission time sequence of the pulse laser, greatly improves the power and the repetition frequency of the output laser on the premise of not changing the characteristic parameters of the light beam of the original laser, can expand the quantity, has no upper limit of power in the combination mode, and has important application value in the industry and other fields;

2. the reflector and other optical path devices of the invention adopt a total reflection mode, thus avoiding the defects of limited device tolerance power and influence on the beam quality when adopting a transmission type optical element, being particularly suitable for the conditions of high power and long-time light emitting, avoiding additional influences such as beam expanding and beam shrinking on the parameters of incident laser in beam combining implementation and ensuring the beam quality of the laser after beam combining.

Drawings

FIG. 1 is a schematic diagram of the operation of the beam combiner for pulsed laser according to the present invention;

FIG. 2 is a timing diagram of n pulse lasers before pulse laser beam combining according to the present invention;

FIG. 3 is a schematic diagram of the output power of the laser after the pulse laser is combined;

FIG. 4 is a schematic diagram illustrating the principle of shifting the beam combiner mirror for pulsed laser according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of the pulse beam combination laser system of the present invention;

FIG. 6 is a schematic diagram of a pulse beam combination laser system according to an embodiment of the present invention;

description of reference numerals:

1-a displacement device; 2-a reflector; 3-incident laser beam; 4-output optical path; 5-a shift control unit; 6-an electric control displacement platform; 7-laser time sequence control unit; 8-synchronous trigger signal; 9-a pulsed laser; 10-fold mirror.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

As shown in fig. 1, fig. 2 and fig. 3, the principle idea of pulse beam combination of the present invention is: n reflectors 2 are obliquely arranged on the same output light path 4, each reflector 2 is arranged on the shifting device 1, and the reflectors 2 can be shifted out of the beam combining light path along the shifting direction 3 in the figure and then shifted back to the beam combining light path, and the beam combining light path is the output light path 4; the shifting means may be an integral or separate mechanism, which allows independent movement of each mirror 2.

Each reflector 2 corresponds to an incident laser beam 3, wherein the laser is a pulse laser output at a repetition frequency, the light emitting time sequence of each laser is as shown in fig. 2, and a scheme of 'research on incoherent synthesis technology of pulse lasers' in the background art can be adopted, a programmable logic array generates an electrical signal with pulse width, frequency and time delay meeting requirements, and then the electrical signal drives a seed laser and amplifies or drives a pulse pumping laser, so that the light pulse output by each laser keeps different time delays to meet the requirements of pulse beam combination.

In fig. 1, when n lasers are incident on the corresponding mirrors 2, the shifting device 1 moves the mirrors 2 away and back to the original positions according to the incident timing sequence, so that when the laser incident from the rear is reflected and output, the front mirror 2 does not block the incident beam from the rear, and thus the combination of multiple pulsed lasers can be realized. For example, the outgoing pulse of the 2# laser has a certain delay compared with that of the 1# laser, when the 2# laser is incident to the 2# mirror, as long as the 1# mirror in front is moved away by the shifting device and is not blocked on the optical path, there is only one laser beam on the beam combining optical path, namely the 2# pulse laser; similarly, the light-emitting pulse of the 3# laser is delayed from that of the 2# laser, when the 3# laser enters the 3# reflector, as long as the 1# reflector and the 2# reflector in front are moved away by the shifting device and are not blocked on the light path, the laser output on the beam combining light path at the moment is the 3# pulse laser, and so on, and after all the lasers are sequentially incident, the laser is recycled from the 1# so as to obtain the high repetition frequency or quasi-continuous laser output shown in fig. 3.

In practical application, due to action delay of the shifting mechanism, when the reflector shifts, the front reflector inevitably has small blocking effect on the rear, and seamless time sequence synthesis is difficult to achieve, so that continuous output is difficult to achieve, and quasi-continuous output can be achieved or the repetition frequency of original laser can be improved. Because each pulse laser is output with a certain duty ratio, the laser after the combination is the combination of n lasers, the average power of the laser is the sum of the average powers of all the n lasers, thereby greatly improving the output average power of the laser, simultaneously, the reflected light beams are coaxial, the quality of the light beams after the combination can not change due to the movement of the reflector, and the laser after the combination can be remotely transmitted and transmitted with high efficiency and high quality.

The significance of this pulse combination is: whether solid state, fiber or semiconductor lasers are affected by nonlinear and thermal effects, it is difficult to increase the average power output of a single laser, especially for a continuous output laser. The purpose of using pulse beam combination is to make a single laser into a pulse laser with a certain repetition frequency output and a small duty ratio, and although the average power cannot be too high due to the influence of nonlinear effect and thermal effect, the peak power of the pulse can be very high. Then, the pulse time sequence characteristic of each laser is adjusted through a pulse beam combination scheme, and n beams of laser beams are combined into high repetition frequency laser or quasi-continuous laser through the beam combination device, so that the output power is improved by n times, the original beam quality is still kept, and the beam combination mode has no power upper limit theoretically, and has important application value in the industry and other fields.

As shown in fig. 4, the shifting apparatus 1 in the embodiment of the present invention is a plurality of electrically controlled shifting stages 6 only electrically connected to the shifting control unit 5, the electrically controlled shifting stages 6 adopt a lead screw transmission mode or an operating mode of an air cylinder or a hydraulic cylinder, under the control of the shifting control unit 5, sequentially drive the corresponding mirrors 2 to move out of the output optical paths 4 according to a time sequence, and then move back to an original position, and ensure that the mirrors 2 in front of the optical paths at each time do not block the light beams behind, and only one laser beam can be output along the output optical paths 4 at the same time. Meanwhile, in order to match with the output time sequence of the laser, the shift control unit 5 outputs a synchronous trigger signal 8 to the laser time sequence control unit 7, or the laser time sequence control unit 7 outputs a synchronous trigger signal 8 to the shift control unit 5, so that the matching of the displacement of the reflector 2 and the pulse laser time sequence is realized. The mirror surface of the reflector 2 is a plane, the included angle between the mirror surface and the output light path 4 is 30-60 degrees, preferably 45 degrees, and the electrically controlled displacement table 6 moves in and out of the output light path 4 according to the direction perpendicular to the output light path 4.

If the effective incident area (i.e. the area after oblique angle projection) of the reflector is far larger than the light spot of the laser beam, the reflector is always in a reciprocating state under the action of the electric control displacement table from the starting time to the ending time of the laser pulse, and the width and the displacement speed of the laser pulse are controlled to ensure that the incident light beam cannot leak out of the reflector surface. If the effective incident area of the reflector is only slightly larger than the light spot of the laser beam, the reflector is kept static at the moment of laser light emitting through the program control setting of the electric control displacement table, and the reflector is quickly moved away from the position of the emitted light beam after the light emitting is finished, so that the shielding of the back reflected light is avoided. The moving mode of the electric control displacement platform can meet the requirements of power superposition and unchanged beam quality of the pulse combined beam and the adoption of a total reflection device on an optical path, and the beam combination requirement of the low-repetition-frequency pulse laser is realized.

Fig. 5 shows a schematic diagram of the composition principle of the pulse beam combination laser system, wherein a light beam output by the pulse laser 9 controlled according to a time sequence is directly incident on the reflector 2, and finally the combined beam is output after being a beam of pulse laser. Fig. 6 shows a compact pulse beam combining laser system, in which the output beam of the laser 9 passes through the turning mirror 10 and then enters the reflecting mirror 2 for beam combining. The whole system is compact in structure, convenient to arrange and implement in the direction perpendicular to the combined beam, and meanwhile, all the combined beam optical devices are in a reflection type, so that the system is particularly suitable for the conditions of high power and long-time light emitting, additional influences such as beam expanding and beam shrinking on parameters of incident laser are not generated in the combined beam implementation, and the quality of the combined laser beam is ensured.

The embodiment also provides a method for pulse laser beam combining, which includes the following steps:

The pulse laser in the step 1) is refracted by the catadioptric mirror and then reflected by the reflecting mirror.

Claims

1. a beam combiner for pulsed laser is characterized in that: comprise laser timing control unit (7), shift control unit (5), shift device (1) and many along the same output optical path (4) ) reflector (2) arranged obliquely; the multi-beam pulsed laser light emitted according to the set timing is reflected by the corresponding reflector (2), and then exits along the output optical path (4) after spatial combination, and each reflector (2) ) corresponds to the incident laser beam; the reflecting mirror (2) is arranged on the shifting device (1), and the shifting device (1) produces an action, so that the reflecting mirror (2) moves in according to the timing matching with the pulsed laser and move out of the output optical path (4), and in the laser output direction of the output optical path (4), the reflector (2) in the front position will not block the beam of the reflector (2) at the rear position;

The displacement device is a plurality of electrically controlled displacement stages (6) that are only electrically connected to the displacement control unit (5) and controlled according to time sequence; the electrically controlled displacement stages move in a direction perpendicular to the output optical path (4) , the mirror (2) is always in a state of reciprocating movement under the action of the electronically controlled displacement stage (6);

The laser timing control unit (7) outputs a synchronous trigger signal (8) to the displacement control unit (5), so as to realize the matching between the displacement of the mirror (2) and the timing of the pulsed laser;

The pulsed laser is a pulsed laser output at a repeated frequency, and the optical pulse output by each laser maintains a different time delay.

2 . The beam combiner for pulsed lasers according to claim 1 , wherein the electronically controlled displacement stage is driven by a lead screw, an air cylinder or a hydraulic cylinder. 3 .

3 . The beam combiner for pulsed laser light according to claim 2 , wherein the angle between the reflection mirror ( 2 ) and the output optical path ( 4 ) is 30-60 degrees. 4 .

4 . The beam combiner for pulsed laser light according to claim 3 , wherein the angle between the reflection mirror ( 2 ) and the output optical path ( 4 ) is 45 degrees. 5 .

5. a pulsed beam combining laser system that utilizes the beam combiner described in any one of claims 1-4 to obtain for pulsed laser, it is characterized in that: comprise n pulse lasers (9) and n reflectors ( 2), the pulsed laser (9) emits laser light according to the set time sequence, and is incident on the reflector (2) to form a combined beam of laser light, where n is a positive integer greater than 1.

6. The pulsed beam combining laser system according to claim 5, characterized in that: it further comprises n folding mirrors (10); the outgoing laser is folded back by the folding mirror (10) and then incident on the reflecting mirror (2).

7. A method for pulsed laser beam combining, based on the pulsed combining laser system of claim 5 or 6, characterized in that, comprising the following steps:

1) The pulsed lasers emitted by at least two lasers (9) according to the set timing are reflected by the respective mirrors (2) and then exit along the output optical path (4);

2) Each reflector (2) moves in and out of the output optical path (4) according to the timing matching with the pulsed laser, and the reflector (2) in the front position will not block the laser output direction of the output optical path (4). The beam from the rear position mirror (2).

8. a kind of method for pulsed laser beam combining according to claim 7 is characterized in that:

The pulsed laser in the step 1) is first refracted by the catadioptric mirror and then reflected by the reflecting mirror (2).