CN104111539B - A kind of array hot spot generator and production method - Google Patents

Abstract

The invention relates to an array spot generator, which generates two-dimensional orthogonal array spot at a specific diffraction distance after the incident coherent plane light is diffracted by a diffractive optical element, which is characterized in that the diffractive optical element It is a second-order pure phase plate, which is composed of closely arranged elements of the same size. Each element has a binary phase distribution, and each element is a square aperture plus a rectangular aperture. The rectangular aperture There is a relative displacement between the center of the light hole and the center of the square light hole, and the specific diffraction distance is related to the wavelength of the incident light, the width of the element and the compression ratio. The array light spot generator has a simple structure, is easy to process and replicate, and has low cost. It is suitable for a variety of different light sources and can be widely used in the fields of optical computing, optical communication, and photoelectric hybrid processing.

Description

A kind of array light spot generator and generating method

technical field

The invention relates to an array spot generator and a generating method.

Background technique

The array spot generator can divide the input beam into regular one-dimensional or two-dimensional array spot, and then realize functions such as optical power distribution, multi-channel interconnection and micro-pattern transmission. The generation of array spots fully embodies the high-speed and parallelism of optical processing, and has a wide range of application values in the fields of optical computing, optical communication, and photoelectric hybrid processing. For example, it is used as a uniform array spot generator for each light gate in a two-dimensional optical logic array, and an energy collector array to improve the performance of an infrared focal plane array detector.

Currently, there are various optical elements that can be used to generate arrayed spots, such as microlens arrays or diffraction gratings. Microlens arrays can directly focus different parts of the incident beam, but the intensity distribution of the array spots generated from a microlens array is not uniform. Using a Galileo or Newtonian telescope system can make the microlens array produce an array spot with uniform intensity distribution, but its additional optical elements increase the cost. An ordinary diffraction grating can divide a beam of light into multiple diffraction orders of light spots, but the ordinary diffraction grating cannot produce an array of light spots with uniform intensity distribution. Specially designed diffraction gratings, such as Damman gratings, can produce arrayed spots with uniform intensity distribution. However, the Damman grating is a diffractive optical element with a special structure based on an optimization algorithm. The number of array spots generated based on it is limited to a certain extent, and the diffraction efficiency of the Damman grating decreases as the number of array spots increases. Therefore, the use of Daman gratings cannot produce high diffraction efficiency, high compression ratio and large number of array spots.

The fractional Taber effect is used to make an optical array spot generator, that is, the Taber array spot generator, which can generate array spots with uniform intensity distribution, high diffraction efficiency, and arbitrary compression ratio. And different beam splitting ratios can be enlarged at various fractional Taber distances, that is, more array spot numbers can be obtained with fewer grating units [Opt.Lett.15, 288 (1990); US Patent US5124843]. However, Taber array spot generators are all based on a multi-order phase plate. To obtain high diffraction efficiency, high compression ratio, and large number of array spots, the higher the phase order required will be. However, the current processing technology is difficult to produce such a high-order phase plate, and the processing process is complicated, and the produced phase plate is expensive, difficult to replicate, and difficult to be applied in practice.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the existing problems and deficiencies in the prior art, and to provide a method for generating array light spots that can realize uniform intensity distribution, high compression ratio, and large number of array light spots at the same time.

The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a method for generating array spot, specifically comprising the following steps:

Step 1: Select multiple binary primitives, set the size value Δ of each binary primitive, the spot compression ratio β and the number M of the array spot in the one-dimensional direction, and calculate the diffractive optics through the above set values the dimension value of the component;

Step 2: Calculate the phase values at the positions of all binary primitives according to the set values set in step 1

Step 3: According to the phase value obtained in step 2 Calculate the relative displacement value δ _mn between the center of the rectangular light hole and the center of the binary primitive in all binary primitives with the size value Δ of all binary primitives;

Step 4: Arranging the M×M binary primitives closely according to the position parameters (m, n) to generate a binary phase distribution map of the binary primitives;

Step 5: Prepare M×M binary primitives into diffractive optical elements according to the binary phase distribution diagram;

Step 6: Determine the diffraction distance according to the size value Δ of each binary primitive, the spot compression ratio β and the wavelength λ of the incident light, then the incident light will generate two-dimensional M×M intensities at this diffraction distance after passing through the diffractive optical element Uniformly distributed orthogonal array of light spots.

The beneficial effects of the present invention are: the diffractive optical element used in the present invention is a pure phase binary device, which is easy to process and reproduce, and has low processing cost; it can simultaneously realize uniform distribution of intensity, high compression ratio, and a large number of two-dimensional orthogonal Generation of array spots; the present invention can produce orthogonal array spots with any compression ratio, especially array spots with high compression ratio and high diffraction efficiency; the present invention only needs to control the size of primitives, the size and compression ratio of diffractive optical elements, The orthogonal array light spots of any period can be generated; the invention has a simple structure and can be widely used in the fields of optical calculation, optical communication, photoelectric hybrid processing and the like.

On the basis of the above technical solutions, the present invention can also be improved as follows.

Further, in the step 3, the phase value Bring the following formula (1) into the relative displacement value δ _mn of the center of the rectangular light hole in all primitives and the center of the primitive with the primitive size value Δ;

Formula 1)

Among them, m: represents the position parameter of the primitive in the array spot generator in the horizontal direction, and takes an integer;

n: indicates the position parameter of the primitive in the array spot generator in the vertical direction, and takes an integer;

Δ: is the side length of the square;

δ _mn : represents the relative displacement between the center of the rectangular light hole and the center of the square light hole in the primitive with the position parameter (m, n);

Indicates the phase value of the position of the primitive whose position parameter is (m, n).

Further, in the step 2, calculate the phase values at all primitive positions according to the formula (2) described below

Formula (2)

Among them, the spot compression ratio β: expresses the compression ratio, and the value is a positive integer;

L: specifies the value range of β;

The phase value above The value range of is [-π, π].

Further, in the step 5, the diffractive optical element is processed by combining photolithography and wet etching of optoelectronic fabrication technology; or the diffractive optical element is processed by combining photolithography and dry etching of optoelectronic fabrication technique.

The technical problem to be solved by the present invention is to overcome the problems and deficiencies in the prior art, and to provide an array spot generator that can realize uniform intensity distribution, high compression ratio, and a large number of array spots at the same time, and the array spot generator can generate device, simple in structure, easy to process and replicate, and low in cost.

The technical solution of the present invention to solve the above-mentioned technical problems is as follows: an array spot generator, including a light source emitting device, a beam expander and a wavefront shaper, a diffractive optical element, and a spot display surface arranged in sequence along the same central axis;

The light source emitting device is used to emit coherent light;

The beam expander and wavefront shaper expands the incident coherent light into coherent planar light; the beam expander and wavefront shaper shapes and expands a Gaussian beam with a small spot diameter into a planar light wave with a larger spot;

The diffractive optical element closely arranges the M×M binary primitives according to the position parameters (m, n) to generate a binary phase distribution diagram of the binary primitives; and according to the binary phase distribution diagram, the M×M A diffractive optical element prepared by binary primitives; wherein, each binary primitive is a binary phase distribution.

The beneficial effects of the present invention are: the diffractive optical element used in the present invention is a pure phase binary device, which is easy to process and reproduce, and has low processing cost; it can simultaneously realize uniform distribution of intensity, high compression ratio, and a large number of two-dimensional orthogonal Generation of array spots; the present invention can produce orthogonal array spots with any compression ratio, especially array spots with high compression ratio and high diffraction efficiency; the present invention only needs to control the size of primitives, the size and compression ratio of diffractive optical elements, The orthogonal array light spots of any period can be generated; the invention has a simple structure and can be widely used in the fields of optical calculation, optical communication, photoelectric hybrid processing and the like.

On the basis of the above technical solutions, the present invention can also be improved as follows.

Further, each binary primitive is a square light hole superimposed with a rectangular light hole, and the center of the rectangular light hole does not overlap with the center of the square light hole.

Further, the phase of the square light hole is 0, and the phase of the rectangular light hole is π; or, the phase of the square light hole is π, and the phase of the rectangular light hole is 0.

Further, the length of one side of the rectangular light-through hole is equal to the length of the square side, the other side of the rectangular light-through hole is half the length of the square light-through hole, and the center of the rectangular light-through hole is aligned with the length of the square light-through hole along the length direction of the short side. There is a relative displacement between the centers.

Further, the relative displacement between the center of the rectangular light hole and the center of the square light hole is determined by the following formula (1):

Formula 1)

Among them, m: represents the position parameter of the primitive in the array spot generator in the horizontal direction, and takes an integer;

n: indicates the position parameter of the primitive in the array spot generator in the vertical direction, and takes an integer;

Δ: is the side length of the square;

δ _mn : represents the relative displacement between the center of the rectangular light hole and the center of the square light hole in the primitive with the position parameter (m, n);

Indicates the phase value of the position of the primitive whose position parameter is (m, n).

Further, in the formula (1) It is calculated by the following formula (2):

Formula (2)

Among them, the spot compression ratio β: expresses the compression ratio, and the value is a positive integer;

L: specifies the value range of β;

The phase value above The value range of is [-π, π].

The relationship between the above-mentioned specific diffraction distance and the incident light wavelength, cell width and compression ratio is as follows: when β is a positive even number, the value of the specific diffraction distance is z=βΔ2/λ; when β is a positive odd number, the specific The value of the diffraction distance is z=2βΔ2/λ, where λ is the wavelength of the incident light.

The number and period of the above-mentioned two-dimensional orthogonal array of light spots are related to the compression ratio, the size of the primitive and the size of the diffractive optical element.

The basic idea of the present invention is based on the circuitous phase encoding principle [Appl.Opt.5,967(1966)], divides the phase plate in the Taber array spot generator into closely arranged sampling units, and then puts a rectangular light-through hole into In each sampling unit, the phase is encoded by changing the position between the center of the rectangular aperture and the sampling center. The multi-order phase distribution of each primitive in the Talbot array spot generator is encoded into a binary (0, π) distribution, thereby transforming the multi-order Talbot array spot generator into a binary array spot generator.

Description of drawings

Fig. 1 is a flow chart of a method for generating array spot of the present invention;

Fig. 2 is a schematic diagram of the first phase distribution of the primitive of the present invention;

Fig. 3 is the schematic cross-sectional view of the first geometric structure of the primitive of the present invention;

Fig. 4 is a schematic diagram of the second phase distribution of the primitive of the present invention;

Fig. 5 is a schematic cross-sectional view of the second geometric structure of the primitive of the present invention;

Fig. 6 is the binary phase distribution figure of 10 * 10 array light spots that the compression ratio of the present invention is β=30;

7 is a schematic diagram of the optical path of the array spot generator of the present invention;

8 is an intensity distribution diagram of 10×10 array spots with a compression ratio of β=30 according to the present invention;

FIG. 9 is a one-dimensional intensity curve diagram of 10×10 array spots with a compression ratio of β=30 according to the present invention;

10 is a binary phase distribution diagram of 20×20 array spots with a compression ratio of β=15 according to the present invention;

Fig. 11 is the intensity distribution figure of 20 * 20 array light spots that the compression ratio designed by the present invention is β=15;

FIG. 12 is a one-dimensional intensity curve diagram of 20×20 array spots with a compression ratio of β=15 designed in the present invention.

In the accompanying drawings, the list of parts represented by each label is as follows:

1. Light source emitting device, 2. Beam expander and wave surface shaper, 3. Diffractive optical element, 4. Spot display surface.

detailed description

The principles and features of the present invention are described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

As shown in Figure 1, a method for generating array spot in the present invention specifically includes the following steps:

Step 1: Select multiple binary primitives, set the size value Δ of each binary primitive, the spot compression ratio β and the number M of the array spot in the one-dimensional direction, and calculate the diffractive optics through the above set values the dimension value of the component;

Step 2: Calculate the phase values at the positions of all binary primitives according to the set values set in step 1

Step 3: According to the phase value obtained in step 2 Calculate the relative displacement value δ _mn between the center of the rectangular light hole and the center of the binary primitive in all binary primitives with the size value Δ of all binary primitives;

Step 4: Arranging the M×M binary primitives closely according to the position parameters (m, n) to generate a binary phase distribution map of the binary primitives;

Step 5: Prepare M×M binary primitives into diffractive optical elements according to the binary phase distribution diagram;

Step 6: Determine the diffraction distance according to the size value Δ of each binary primitive, the spot compression ratio β and the wavelength λ of the incident light, then the incident light will generate two-dimensional M×M intensities at this diffraction distance after passing through the diffractive optical element Uniformly distributed orthogonal array of light spots.

Taking the incident light wavelength λ=633nm, element width Δ=60um, and diffractive optical element size as 18mm×18mm as an example, a specific implementation scheme of high compression ratio and large number of orthogonal array spots is designed.

FIG. 2 is a schematic diagram of the first phase distribution of the elements in the diffractive optical element of the present invention. As shown in the figure, the primitive is to add a rectangular light hole with a phase of π into a square light hole with a phase of 0. For this pure phase binary structure, it can be processed by combining the mature optoelectronic preparation process photolithography and wet/dry etching. In this embodiment, BK7 glass with an incident light wavelength of 633 nm and a refractive index of 1.515 is selected as the substrate, and the corresponding etching depth is 615 nm. Its geometric structure parameters are shown in Fig. 3. FIG. 4 is a schematic diagram of the second phase distribution of the elements in the diffractive optical element of the present invention. Fig. 5 is a schematic diagram of the second geometric structure of the primitive. For the two phase distributions of the elements in the diffractive optical element of the present invention, the effect of generating array spot is the same. In this embodiment, the first type is taken as an example to illustrate the implementation effect.

In this embodiment, the geometric dimension of the square light hole is Δ×Δ=60um×60um; the geometric dimension of the rectangular light hole is Δ×Δ/2=60um×30um. There is a relative displacement δ _mn Δ between the geometric center of the rectangular light hole and the geometric center of the square light hole, and the displacement is along the x direction of the short side of the rectangle. The relative displacement δ _mn is related to the position parameters m and n of the primitive , which can be given by formula (1):

Formula 1)

in,

Formula (2)

Wherein, β in formula (2) represents the compression ratio, and its value is a positive integer; L is a value specifying the value range of β, and its value is 0 or a positive integer. in, The value range of is [-π, π], and from the size of the diffractive optical element and the width of the element, the number of elements in the one-dimensional direction M = 18mm/60um = 300, that is, m, n∈[ 1,300].

Therefore, through formula (1) and formula (2), the relative displacement of all primitives in all diffractive optical elements can be calculated, and then the geometric structure of each primitive can be determined, and then all primitives can be closely arranged according to the corresponding position parameters , the phase distribution diagram of the binary pure phase diffractive optical element is obtained.

Fig. 6 shows the binary pure phase distribution diagram of the diffractive optical element when the compression ratio is a positive even number β=30. According to the binary pure phase distribution shown in Fig. 6, a pure phase diffractive optical element is manufactured, and then the array light spot can be generated by using this diffractive optical element.

Figure 7 shows the schematic diagram of the optical path of the array spot generator. The light emitted by the light source emitting device 1, through the beam expander and the wavefront shaper 2, becomes a uniform incident coherent plane wave, and after passing through the diffractive optical element 3, the light at a certain diffraction distance An array of light spots is generated on the light spot display surface 4 .

Diffractive optical elements with different geometric structures will correspond to different diffraction distance z, and the diffraction distance z is related to the wavelength of incident light, element width and compression ratio. When the compression ratio β is a positive even number, the diffraction distance z=βΔ2/λ; when the compression ratio β is a positive odd number, the specific diffraction distance z=2βΔ2/λ. In this example, z=2×30×602/0.633um=170.6mm is obtained from the above parameters. As shown in FIG. 8, it is the simulated diffraction light intensity distribution at the diffraction distance z=170.6 mm. It can be seen from FIG. 8 that 10×10 orthogonal array light spots are generated at this diffraction distance. FIG. 9 is a graph of intensity distribution in the corresponding one-dimensional transverse direction. It can be seen from the figure that the light intensity of the array spot is uniformly distributed. The period of the grating can be calculated from the geometric size of the diffractive optical element, and the period is β×Δ=30×60um=1.8mm. In this example, the size of the diffractive optical element is 18mm×18mm, so the number of array spots obtained is 10×10.

Fig. 10 shows the binary pure phase distribution diagram of the diffractive optical element when the compression ratio is a positive odd number β=15. When the compression ratio β is a positive odd number, the specific diffraction distance z=2βΔ2/λ=170.6mm. As shown in FIG. 11 , it is the simulated intensity distribution of diffracted light at the diffraction distance z=170.7 mm. It can be seen from FIG. 11 that orthogonal array light spots are also generated at this diffraction distance. Fig. 12 is a graph of intensity distribution in the corresponding one-dimensional transverse direction. It can be seen from the figure that an array spot with uniform intensity is obtained, but the period of the array spot becomes β×Δ=15×60um=0.9mm. The size of the diffractive optical element is 18mm×18mm, so the number of array spots obtained is 20×20.

It can be seen that the present invention can generate a two-dimensional orthogonal array of light spots with uniform intensity distribution, and the number of light spots is related to the compression ratio, the size of the primitive and the size of the phase plate. This array light spot generator can fully satisfy the actual manufacturing process, has a simple structure, is easy to process and replicate, and has low cost, so it can be widely used.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (9)

1. An array spot generation method is characterized in that, specifically comprises the following steps: Step 1: Select multiple binary primitives, set the size value Δ of each binary primitive, the spot compression ratio β and the number M of the array spot in the one-dimensional direction, and calculate the diffractive optics through the above set values the dimension value of the component; Step 2: Calculate the phase values at the positions of all binary primitives according to the set values set in step 1 Step 3: According to the phase value obtained in step 2 Calculate the relative displacement value δ _mn between the center of the rectangular light hole and the center of the binary primitive in all binary primitives with the size value Δ of all binary primitives; Step 4: Arranging the M×M binary primitives closely according to the position parameters (m, n) to generate a binary phase distribution map of the binary primitives; Step 5: Prepare M×M binary primitives into diffractive optical elements according to the binary phase distribution diagram; Step 6: Determine the diffraction distance according to the size value Δ of each binary primitive, the spot compression ratio β and the wavelength λ of the incident light, then the incident light will generate two-dimensional M×M intensities at this diffraction distance after passing through the diffractive optical element Uniformly distributed orthogonal array of light spots. 2. A kind of array spot generation method according to claim 1, is characterized in that, in described step 3, phase value Bring the following formula (1) into the relative displacement value δ _mn of the center of the rectangular light hole in all primitives and the center of the primitive with the primitive size value Δ; Formula 1) Among them, m: represents the position parameter of the primitive in the array spot generator in the horizontal direction, and takes an integer; n: indicates the position parameter of the primitive in the array spot generator in the vertical direction, and takes an integer; Δ: represents the side length of a square; each of the binary primitives is a square light hole superimposed with a rectangular light hole, and the center of the rectangular light hole does not overlap with the center of the square light hole; δ _mn : represents the relative displacement between the center of the rectangular light hole and the center of the square light hole in the primitive with the position parameter (m, n); Indicates the phase value of the position of the primitive whose position parameter is (m, n). 3. a kind of array spot generation method according to claim 2, is characterized in that, in the described step 2, calculate the phase value at all primitive positions according to the formula (2) described below Formula (2) Among them, the spot compression ratio β: expresses the compression ratio, and the value is a positive integer; L: specifies the value range of β; The phase value above The value range of is [-π, π]. 4. A method for generating array spot according to any one of claims 1-3, characterized in that, in the step 5, a method combining optoelectronic manufacturing process photolithography and wet etching is used to process the diffractive optical element; Or process the diffractive optical element by combining photolithography with dry etching. 5. An array spot generator, characterized in that it includes a light source emitting device, a beam expander and a wavefront shaper, a diffractive optical element, and a spot display surface arranged sequentially along the same central axis; The light source emitting device is used to emit coherent light; The beam expander and wavefront shaper expands the incident coherent light into coherent plane light; The diffractive optical element diffracts the incident coherent plane light; making the spot display surface present a two-dimensional orthogonal array of spots; The diffractive optical element closely arranges the M×M binary primitives according to the position parameters (m, n) to generate a binary phase distribution diagram of the binary primitives; and according to the binary phase distribution diagram, the M×M A diffractive optical element prepared from binary primitives; wherein, each binary primitive is a binary phase distribution; each binary primitive is a square light hole superimposed on a rectangular light hole, The centers of the rectangular light apertures do not overlap with the centers of the square light apertures. 6. A kind of array spot generator according to claim 5, characterized in that, the phase of the square light through hole is 0, and the phase of the rectangular light through hole is π; or, the phase of the square light through hole is π, and the phase of the rectangular aperture is 0. 7. The array spot generator according to claim 6, wherein the length of one side of the rectangular light-through hole is equal to the length of the side of the square, and the length of the other side of the rectangular light-through hole is half that of the square light-through hole , there is a relative displacement between the center of the rectangular light hole and the center of the square light hole along the length direction of the short side. 8. A kind of array spot generator according to any one of claims 5-7, is characterized in that, the relative displacement between the center of described rectangular light-through hole and the center of square light-through hole is by following formula ( 1) decide: Formula 1) Among them, m: represents the position parameter of the primitive in the array spot generator in the horizontal direction, and takes an integer; n: indicates the position parameter of the primitive in the array spot generator in the vertical direction, and takes an integer; Δ: is the side length of the square; δ _mn : represents the relative displacement between the center of the rectangular light hole and the center of the square light hole in the primitive with the position parameter (m, n); Indicates the phase value of the position of the primitive whose position parameter is (m, n). 9. a kind of array spot generator according to claim 8, is characterized in that, in the described formula (1) It is calculated by the following formula (2): Formula (2) Among them, the spot compression ratio β: expresses the compression ratio, and the value is a positive integer; L: specifies the value range of β; The phase value above The value range of is [-π, π].