CN113341580A - Coherent laser synthesis system - Google Patents

Abstract

The invention discloses a coherent laser synthesis system, comprising a laser source and a lens array, wherein the lens array includes a plurality of lenses, and the lenses are arranged according to a preset Fermat spiral array of non-equal period and non-uniform spatial density; wherein, the laser source is used for Generates multiple laser beams, the laser beams meet the coherence conditions, and the multiple laser beams correspond to multiple lenses one-to-one; the lens is used to receive multiple laser beams and collimate the multiple laser beams, so that each The laser beams are coherently superimposed in the far field to obtain a composite beam. By arranging the lenses according to the Fermat spiral array with non-equi-period and non-uniform spatial density, the present invention makes the lens arrays have a compact center and sparse edge arrangement, thereby increasing the power ratio of the coherent synthesis far-field bucket. At the same time, the side lobe strength of the coherent composite far field is weakened.

Description

A coherent laser synthesis system

technical field

The invention belongs to the technical field of coherent lasers, and in particular relates to a coherent laser synthesis system.

Background technique

Continuously achieving high-power, high-beam quality laser output has always been the goal of defense, industry, and other fields. Fiber lasers have many advantages such as high output beam quality, high power, and compact structure. However, due to factors such as nonlinear effects, thermal effects, and mode instability, the output optical power or energy of a single fiber laser is limited.

In order to obtain a laser with higher power and higher beam quality, it is necessary to obtain a laser output with higher power and better beam quality through multi-channel laser coherent synthesis. Filling method is particularly important. At present, the aperture filling array commonly used in the related art is a regular hexagonal array with an equal period distribution, that is, a plurality of lenses are tiled and spliced in a plane according to a regular hexagonal arrangement.

However, the above-mentioned regular hexagonal array arrangement with equal periodicity will make the far-field output coherently synthesized by the array laser easily detectable side lobes, that is, the energy of the array laser will be partially dispersed to the side lobes, which is not conducive to improving the concentration in the far field. The proportion of energy in the range of the main lobe of the field reduces the quality of the laser beam.

SUMMARY OF THE INVENTION

In order to solve the above problems existing in the prior art, the present invention provides a coherent laser synthesis system. The technical problem to be solved by the present invention is realized by the following technical solutions:

The present invention provides a coherent laser synthesis system, which includes a laser source and a lens array; the lens array includes a plurality of lenses, and the lenses are arranged according to a preset Fermat spiral array with a non-equivalent period and a non-uniform spatial density; wherein,

The laser source is used to generate multiple laser beams, the laser beams satisfy the coherence condition, and the multiple laser beams correspond to the multiple lenses one-to-one;

The lens is used for receiving the multiple laser beams, and collimating the multiple laser beams, so that the respective laser beams emitted from the lens are coherently superimposed in the far field to obtain a combined beam.

In an embodiment of the present invention, the preset Fermat spiral array with non-periodic and non-uniform spatial density is:

表示第n个透镜中心相对于极轴位置的角度，常数β₁控制两个连续透镜之间的角位移，s控制所述预设的非等周期非均匀空间密度费马螺旋阵列中透镜的均匀性与集中程度；ρ _n represents the distance from the center of the nth lens to the center of the preset Fermat spiral array with non-equi-periodic and non-uniform spatial density,

Represents the angle of the center of the nth lens relative to the position of the polar axis, the constant β1 controls the angular displacement between two consecutive lenses, and _s controls the uniformity of the lenses in the preset non-periodic non-uniform spatial density Fermat spiral array Sex and concentration;

Wherein, n _{= 1} , ₂ , .

In an embodiment of the present invention, the preset interval is 0.01˜0.02.

In an embodiment of the present invention, the laser source is a fiber laser.

In one embodiment of the present invention, the lens array includes 120-168 lenses.

In one embodiment of the present invention, the lens array includes 120 lenses, and the radius of each lens is 0.05 cm.

In an embodiment of the present invention, the far-field amplitude of the composite beam is:

Wherein, U _Σ (x ₁ , y ₁ ) represents the complex amplitude distribution of the composite beam on the exit surface of the lens, x1 and y1 are the abscissa and ordinate of the exit surface, respectively, and i is the complex number Imaginary unit, k is the wave vector constant, and k=2π/λ, λ represents the wavelength of the light wave emitted by the laser source, z represents the distance from the light field to the far field, x and y are the abscissa and ordinate of the far field, respectively coordinate.

In an embodiment of the present invention, the distance that the optical field is transmitted to the far field is:

Wherein, λ represents the wavelength of the light wave emitted by the laser source, D represents the equivalent aperture of the lens array, and z represents the calculated distance from the optical field to the far field.

The beneficial effects of the present invention are:

The embodiment of the present invention provides a coherent laser synthesis system, including a laser source and a lens array, the lens array includes a plurality of lenses, and the lenses are arranged according to a preset Fermat spiral array of non-equi-period and non-uniform spatial density; wherein, the laser source It is used to generate multiple laser beams, the laser beams meet the coherence conditions, and the multiple laser beams correspond to multiple lenses one-to-one; the lens is used to receive multiple laser beams, and collimates the multiple laser beams so that the lens exits The individual laser beams are coherently superimposed in the far field to obtain a composite beam. By arranging the lenses according to the Fermat spiral array with non-equi-period and non-uniform spatial density, the present invention makes the lens arrays have a compact center and sparse edge arrangement, thereby increasing the power ratio of the coherent synthesis far-field bucket. At the same time, the side lobe strength of the coherent composite far field is weakened.

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is the schematic diagram of the regular hexagonal array of the medium periodic distribution of the related art;

2 is a schematic structural diagram of a coherent laser synthesis system provided by an embodiment of the present invention;

3 is a schematic diagram of a lens array in a coherent laser synthesis system provided by an embodiment of the present invention;

4 is another schematic structural diagram of a lens array in a coherent laser synthesis system provided by an embodiment of the present invention;

FIG. 5 is another schematic structural diagram of a lens array in a coherent laser synthesis system provided by an embodiment of the present invention.

Detailed ways

The present invention will be described in further detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

At present, in the related art, the lens array is arranged, and the laser beam with higher power and quality is obtained by using the array fiber laser coherent synthesis technology. In the array fiber laser coherent synthesis technology, it is necessary to determine the aperture filling method of the multi-channel fiber laser, and the regular hexagonal array with equal periodic distribution is the most commonly used tile aperture filling array. Specifically, referring to Fig. 1, the lenses are tiled and spliced in a plane according to a regular hexagonal arrangement, so that the laser beams emitted by the lens are coherently combined in the far field, and are aligned in the far field plane. The laser output with high power and high beam quality is obtained within the range (the standard barrel size generally takes the radius r=1.22λ/D, λ is the wavelength of the coherent composite beam, and D is the equivalent aperture of the hexagonal array).

However, during the research process, the inventor found that when the regular hexagonal arrays with equal periodic distribution are arranged, the coherent combined beam output in the far field has side lobes that are easily detected, that is, the part of the coherent combined beam The energy will be dispersed to the side lobes, which is not conducive to increasing the proportion of energy concentrated in the far-field main lobe range; at the same time, when the number of lenses increases to dozens or even hundreds of arrays, the arrangement of the regular hexagonal array It also causes the duty cycle of the array to decrease.

In view of this, the present invention provides a coherent laser synthesis system.

As shown in FIG. 2 , a coherent laser synthesis system 100 provided by an embodiment of the present invention includes a laser source 10 and a lens array 20 ; the lens array 20 includes a plurality of lenses 201 , and the lenses 201 follow a preset aperiodic and non-uniform space Density Fermat spiral array arrangement; where,

The laser source is used to generate multiple laser beams 101, the laser beams 101 satisfy the coherence condition, and the multiple laser beams 101 correspond one-to-one with the multiple lenses 201;

The lens 201 is used for receiving the multiple laser beams 101 and collimating the multiple laser beams 101 , so that the respective laser beams 101 emitted by the lens 201 are coherently superposed in the far field to obtain the combined beam 30 .

In this embodiment, the coherent laser synthesis system 100 includes a laser source 10 . After the laser beam emitted from the laser source 10 is divided into beams, many sub-beams, that is, laser beams 101 , can be obtained. It should be understood that the basic principle of the fiber coherent synthesis technology is to precisely control the optical paths of the multiple laser beams 101 generated by the medium-power laser source 10, so that the laser beams 101 are superimposed on the far-field target to obtain high-power, high-quality laser beams. Single-mode laser output; wherein, the basic condition for coherent synthesis is that the laser beams 101 emitted by the laser source 10 satisfy the coherence condition, that is, the laser beams 101 have the same phase, the same polarization direction and the same wavelength.

Optionally, the laser source 10 is a fiber laser. Fiber lasers refer to lasers that use rare-earth element-doped glass fiber as the gain medium. They have the characteristics of small size, light weight, compact structure, and high reliability. When using fiber lasers to make coherent laser synthesis systems, it is more conducive to achieve integration.

Certainly, other types of lasers may also be selectively used as the laser source 10 in some other embodiments of the present application, such as solid-state lasers or semiconductor lasers, which are not limited in this embodiment.

Further, since the laser beams 101 generated by the laser source 10 and the lenses 201 in the lens array 20 have the same number and are in one-to-one correspondence, each laser beam 101 is received by the lens 201 and the lens 201 collimates the laser beam. Exemplarily, the lens 201 selectively uses a collimating lens, the lens array 20 can be installed on an aluminum lens holder, and each lens is pre-calibrated with an interferometer to reduce the angular deviation of the optical axis in each lens 201, thereby Improve collimation accuracy.

It should be noted that, in some other embodiments of the present application, the lens 201 may also use other types of lenses, as long as the laser beam 201 can be collimated. In addition, FIG. 2 only schematically shows the relative positional relationship between the laser source 10 and the lens array 20 , and the number of laser beams 101 and the number of lenses 201 in the lens array 20 are not intended to limit the application.

FIG. 3 is a schematic structural diagram of a laser array in a coherent laser synthesis system provided by an embodiment of the present invention. As shown in FIG. 3 , the black dot is the center of each lens 201 in the lens array 20 . Please refer to FIGS. 2-3 . In this embodiment, the plurality of lenses 201 follow a preset Fermat spiral with a non-equal period and non-uniform spatial density. The array arrangement can make the lens array 20 present a compact center and sparse edge arrangement, thereby increasing the power ratio of the coherent combined far-field bucket while weakening the side lobe intensity of the coherent combined far-field.

Optionally, the preset non-periodic and non-uniform spatial density Fermat spiral array is:

表示第n个透镜201中心相对于极轴位置的角度，常数β₁控制两个连续透镜201之间的角位移，s控制预设的非等周期非均匀空间密度费马螺旋阵列中透镜201的均匀性与集中程度；ρ _n represents the distance from the center of the n-th lens 201 to the center of the preset Fermat spiral array with non-equal period and non-uniform spatial density,

Represents the angle of the center of the nth lens 201 relative to the position of the polar axis, the constant β1 controls the angular displacement between two consecutive lenses 201, and _s controls the preset non-periodic non-uniform spatial density of the lens 201 in the Fermat spiral array. uniformity and concentration;

Wherein, n _{= 1} , ₂ , .

Please refer to the above formula, the parameter s controls the uniformity and concentration of the array elements (ie the lens 201 ) in the Fermat spiral array. Specifically, when the parameter s is constant, the Fermat spiral array is a uniform spatial density spiral array, and when the parameter is non-constant, the Fermat spiral array is a non-uniform spatial density spiral array. Exemplarily, in this embodiment, s=s ₀ +(n-1)Δs is set, where n=1, 2, . . . , N, N represents the number of lenses 201 , s ₀ is the initial value of s, and Δs is The preset interval ranges from 0.01 to 0.02, for example, Δs=0.01, Δs=0.015, or Δs=0.02.

In the lens array 20, each lens 201 actually has a light-transmitting hole with a certain radius, and the entire lens array 20 has a minimum circumscribed circle. In this circumcircle region, only the position of each lens 210 transmits light, and the rest The positions are all opaque, and the ratio of the area of the light-transmitting hole to the area of the entire circumscribed circle is the duty ratio; wherein, the above circumscribed circle refers to a circle with the smallest size that includes all the lenses 201 . It can be understood that, the larger the duty ratio of the currently used non-uniform spatial density helical array, the better the quality of the combined beam.

4 and 5 are another schematic structural diagram of a lens array in a coherent laser synthesis system provided by an embodiment of the present invention. It should be noted that the black circle in FIG. 4 and FIG. 5 is the center of each lens 201 in the lens array 20 . Referring to the lens arrays shown in Figure 3, Figure 4 and Figure 5, the values of Δs are 0.01, 0.15 and 0.02, respectively. It can be seen that, with the increase of Δs, the degree of concentration in the center of the lens array 10 also increases, and the duty cycle of the central area of the lens array 10 also increases. Obviously, this application sets the range of Δs to 0.01-0.02. Although the duty cycle is slightly reduced, it can provide a good foundation for subsequent application in laser coherent synthesis and increase the power ratio in the far-field bucket, thereby further improving the efficiency of the synthesized beam. quality.

It should be noted that this embodiment only takes the case where the parameter s is an arithmetic sequence as an example for description. In some other embodiments of this application, the parameter s may also take values in other ways. In addition, when s=s ₀ +(n-1)Δs, the preset interval Δs can also be flexibly adjusted according to the actual situation.

Optionally, the lens array 20 includes 120 to 168 lenses 201 , for example, the number of lenses in the lens array 20 is 120, and the radius of each lens 201 is 0.05 cm. It should be understood that the greater the number of lenses 201, the more favorable it is to obtain a high-quality composite beam, but at the same time, it will also increase the manufacturing difficulty of the above-mentioned coherent laser synthesis system and increase the production cost; while the number of lenses 201 is too small, it will lead to synthesis The energy of the beam is lower, and the side lobes are more pronounced than the main lobes. In this embodiment, by setting the number of lenses 201 to 120-168, the quality of the combined beam can be improved, the manufacturing cost of the coherent laser combining system can be reduced, and the combining effect can be improved.

In addition, the size of the lens 201 in this embodiment should be flexibly set according to actual needs. Generally speaking, the order of magnitude corresponding to the radius size of the lens 201 may be millimeters or centimeters, which is not limited in this embodiment.

In this embodiment, the far-field amplitude of the composite beam is:

Among them, U _Σ (x ₁ , y ₁ ) represents the complex amplitude distribution of the composite beam on the exit surface of the lens, x1 and y1 are the abscissa and ordinate of the exit surface, respectively, i is the imaginary unit in complex numbers, and k is the The wave vector constant, and k=2π/λ, λ represents the wavelength of the light wave emitted by the laser source, z represents the distance from the light field to the far field, and x and y are the abscissa and ordinate of the far field, respectively.

In this embodiment, the distance from the light field to the far field is:

Among them, λ represents the wavelength of the light wave emitted by the laser source, D represents the equivalent aperture of the lens array, and z is the distance from the calculated optical field to the far field. For a lens array 20, the equivalent aperture is actually the diameter of its circumscribed circle, and the diameter of the circumscribed circle is uniquely determined. Only when the number or size of the lenses 201 changes, the size of the lens array 20 will change accordingly. As shown in the above formula, the larger the diameter D of the circumscribed circle of the lens array 20 is, the greater the distance from the light field to the far field is transmitted; on the contrary, the smaller the diameter D of the circumscribed circle of the lens array 20 is, the smaller the distance from the light field to the far field is transmitted. .

It should be understood that the standard bucket is a preset area on the far-field plane, and the light field in the preset area is the main lobe of the light spot, and the power in the bucket (PIB) is the far-field standard bucket range The ratio of the inner energy to the total energy of the far-field receiving surface, PIB<1. Optionally, the commonly used standard buckets are 0.53λz/D, 1.22λz/D, 2.23λz/D, 3.24λz/D, etc. The larger the circumcircle diameter D of the lens array 20 and the larger the PIB, the more far-field light is indicated. The more the field energy is distributed in the gauge bucket, the better the quality of the resulting beam.

As can be seen from the above-mentioned embodiments, the beneficial effects of the present invention are:

The invention provides a coherent laser synthesis system, which includes a laser source and a lens array, the lens array includes a plurality of lenses, and the lenses are arranged according to a preset Fermat spiral array of non-equal period and non-uniform spatial density; wherein, the laser source is used for Generates multiple laser beams, the laser beams meet the coherence conditions, and the multiple laser beams correspond to multiple lenses one-to-one; the lens is used to receive multiple laser beams and collimate the multiple laser beams, so that each The laser beams are coherently superimposed in the far field to obtain a composite beam. By arranging the lenses according to the Fermat spiral array with non-equi-period and non-uniform spatial density, the present invention makes the lens arrays have a compact center and sparse edge arrangement, thereby increasing the power ratio of the coherent synthesis far-field bucket. At the same time, the side lobe strength of the coherent composite far field is weakened.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " rear, left, right, vertical, horizontal, top, bottom, inside, outside, clockwise, counterclockwise, etc., or The positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it should not be construed as a limitation of the present invention.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

Although the application is described herein in conjunction with the various embodiments, those skilled in the art will understand and understand, by reviewing the drawings, the disclosure, and the appended claims, in practicing the claimed application. Other variations of the disclosed embodiments are implemented. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that these measures cannot be combined to advantage.

Claims (8)

1. A coherent laser synthesis system comprising a laser source and a lens array; the lens array comprises a plurality of lenses, and the lenses are arranged according to a preset non-uniform-period non-uniform-space-density Fermat spiral array; wherein,

the laser source is used for generating a plurality of laser beams, the laser beams meet the coherence condition, and the laser beams correspond to the lenses one by one;

the lens is used for receiving the laser beams and collimating the laser beams, so that the laser beams emitted by the lens are coherently superposed in a far field to obtain a composite beam.

2. The coherent laser combining system of claim 1, wherein the predetermined non-uniform periodic non-uniform spatial density fermat spiral array is:

ρ_nrepresenting the distance of the center of the nth lens from the center of the preset non-uniform periodic non-uniform spatial density Fermat spiral array,

angle representing the position of the n-th lens center with respect to the polar axis, constant beta₁Controlling the angular displacement between two successive lenses, s controlling the preset non-uniform periodic non-uniform spatial density Fermat spiralThe uniformity and concentration of the lenses in the array;

wherein N is 1, 2, …, N represents the number of lenses, s is s₀+(n-1)Δs，s₀Is an initial value of s, Δ s is a predetermined interval, β₁＝1.618。

3. The coherent laser combining system according to claim 2, wherein the predetermined interval is 0.01 to 0.02.

4. The coherent laser combining system of claim 1, wherein the laser source is a fiber laser.

5. The coherent laser combining system of claim 4, wherein the lens array comprises 120-168 lenses.

6. The coherent laser combining system of claim 5, wherein the lens array comprises 120 lenses, each lens having a radius of 0.05 cm.

7. The coherent laser combining system of claim 1, wherein the far field amplitude of the combined beam is:

wherein, U_Σ(x₁，y₁) The complex amplitude distribution of the combined light beam on the lens emergent surface is shown, x1 and y1 are respectively an abscissa and an ordinate of the emergent surface, i is an imaginary number unit in a complex number, k is a wave vector constant, k is 2 pi/lambda, lambda represents the wavelength of the light wave emitted by the laser source, z represents the distance from the light field to the far field, and x and y are respectively the abscissa and the ordinate of the far field surface.

8. The coherent laser combining system of claim 7, wherein the optical field is transmitted to the far field at a distance of:

wherein λ represents the wavelength of the light wave emitted by the laser source, D represents the equivalent aperture of the lens array, and z is the calculated distance from the optical field to the far field.

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