CN218974691U - Immersion type continuous plane type diffraction beam splitter - Google Patents
Immersion type continuous plane type diffraction beam splitter Download PDFInfo
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Abstract
The utility model discloses an immersed continuous plane type diffraction beam splitter, which consists of a single-period structure array; the single-period structure sequentially comprises a substrate structure layer, an optical medium 1 and an optical medium 2 from bottom to top, wherein the refractive indexes of the optical medium 1 and the optical medium 2 are different; the planar sagittal height h between the optical medium 1 and the optical medium 2 satisfies the following relation: h=1/2 λ Φ n1-n 2/pi. The beneficial effects of the utility model are as follows: the immersion type continuous plane type diffraction beam splitter has the advantages that the whole plane type is excessively smooth and has no step structure, the whole diffraction efficiency can reach more than 95%, the uniformity error among orders can be less than 5%, and the beam splitting uniformity is good. The submerged continuous surface type diffraction beam splitter disclosed by the utility model has the advantages that the corresponding sagittal height of the surface type is improved by a plurality of times compared with the sagittal height of the original design, and the difficulty in surface type processing is obviously reduced.
Description
Technical Field
The utility model belongs to the technical field of optics, and particularly relates to an immersion type continuous surface type diffraction beam splitter.
Background
A beam splitter may be placed in the optical path to modulate the light to achieve the function of dividing a single beam into multiple target beams in proportion. The method is widely applied to the fields of laser radar, laser processing display, skin treatment and the like.
The beam splitter is of a periodic structure, the period size is influenced by the adjacent-order included angle, the applicable wavelength and other parameters, and the diffraction equation is adopted
Where d is the period size, θm is the diffraction beam angle, m is the beam order, and λ is the working wavelength. The single period inner surface type is continuous, the specific structure of the surface type is influenced by a beam splitting target, and the whole surface type is a central symmetrical pattern.
At present, the diffraction beam splitter mainly has a highly discrete step structure, because the number of steps is 2 n due to the process, typically: 2 nd order, 4 th order, 8 th order, 16 th order, etc. The diffraction efficiency is limited by the step structure and has a theoretical bottleneck (theoretically, the upper line of the diffraction efficiency is 40.5%,81.1%,95.1%,98.7% and the like). However, the practical efficiency is further reduced due to shape tolerance, position tolerance and other factors introduced in the processing process.
In the field of micro-nano surface type processing, the method is mainly performed in the modes of single-point diamond machining, mask photoetching, maskless laser direct writing, nano imprinting and the like at present, and the precision of the laser direct writing process can reach 100nm except for a high-cost semiconductor process. However, for the processing of submicron-sized surface patterns, the current precision is still to be improved.
Disclosure of Invention
The main object of the present application is to provide an immersion type continuous surface type diffraction beam splitter with an overall surface type excessively smooth structure without steps, and with an overall diffraction efficiency of more than 95%, and with a uniformity error between orders of less than 5%, and with a better beam splitting uniformity.
In order to achieve the above object, the present utility model provides the following technical solutions:
an immersion continuous surface type diffraction beam splitter, the diffraction beam splitter being comprised of at least one array of monocycle structures;
the single-period structure sequentially comprises a substrate structure layer, an optical medium 1 and an optical medium 2 from bottom to top, wherein the refractive indexes of the optical medium 1 and the optical medium 2 are different;
the planar sagittal height h between the optical medium 1 and the optical medium 2 satisfies the following relation:
wherein:
lambda represents the wavelength;
n1 represents the refractive index of the optical medium 1;
n2 represents the refractive index of the optical medium 2.
The beam splitter is of a periodic structure, the period size is influenced by the included angle of adjacent orders, the wavelength is applicable, and the diffraction equation is used for
Where d is the period size, θ is the angle of the diffracted beam, m is the beam order, and λ is the operating wavelength. />
The original diffraction beam splitting scheme is of a single modulation surface type, the refractive index value is fixed to be n1, if the medium is directly incident into an air medium, the refractive index difference delta n is larger, the vector height is lower, and the surface type machining precision is difficult to guarantee. If the refractive indexes of the media at two sides of the surface type are similar, the corresponding sagittal height of the surface type is improved by a plurality of times compared with the original sagittal height, and the corresponding sagittal height of the surface type can be generally increased from submicron sagittal height to a height of a plurality of micrometers or even hundreds of micrometers. The difficulty of surface processing is obviously reduced.
The immersion type continuous surface type diffraction beam splitter as a preferred embodiment further comprises a lower layer antireflection film and an upper layer antireflection film, wherein the lower layer antireflection film is covered on the lower surface of the base structure layer, and the upper layer antireflection film is covered on the upper surface of the optical medium 2;
the wavelengths of the lower antireflection film and the upper antireflection film are in the above relation with each other
Is the same.
The provision of the antireflection film can increase transmittance. The film layer may be a single layer of magnesium fluoride (MgF) or other multi-layer film system.
An immersion type continuous plane diffraction beam splitter as described above, as a preferred embodiment, the base structure layer is a quartz layer, a glass layer, or an optical plastic layer; the thickness of the base structure layer is 2-3mm.
As a preferred embodiment, the immersion type continuous plane type diffraction beam splitter is characterized in that the optical medium 1 is optical glass, optical plastic or optical resin, and the refractive index difference between the optical medium 1 and air is 0.4-1.2; the thickness of the optical medium 1 is the planar sagittal height h.
As a preferred embodiment, the immersion type continuous plane type diffraction beam splitter is that the optical medium 2 is optical glass, optical plastic or optical resin, and the refractive index difference between the optical medium 1 and the optical medium 2 is 0-0.9; the thickness of the optical medium 2 is 20-30um.
The immersion type continuous surface diffraction beam splitter as a preferred embodiment further comprises an upper substrate layer, wherein the upper substrate layer covers the upper surface of the optical medium 2;
the upper substrate layer is a quartz layer, a glass layer or an optical plastic layer; the thickness of the upper basal layer is 2-3mm.
The arrangement of the upper basal layer seals the whole body into an integrated structure, isolates the optical modulation surface type from the external environment, has good dustproof, mildew-proof, water vapor-proof and salt fog-proof effects, and can keep excellent optical performance for a long time.
As a preferred embodiment, the upper substrate layer may be attached to the upper surface of the optical medium 2 by means of gluing.
In a second aspect of the present application, a method for preparing an immersion type continuous surface type diffraction beam splitter is provided, including the following steps:
(1) Making a master, wherein the surface structure of the master is matched with the surface shape between the optical medium 1 and the optical medium 2;
(2) Placing a viscous optical medium 1 on the substrate structural layer, imprinting by adopting a master plate, filling the gap between the master plate and the substrate structural layer with the optical medium 1, heating and curing, and removing the master plate;
(3) Placing a viscous optical medium 2 on the substrate obtained in the step (2), stamping by adopting a horizontal master plate, and curing after the surface is leveled to obtain the immersed continuous plane type diffraction beam splitter.
In the above method for preparing an immersion type continuous plane diffraction beam splitter, in step (1), as a preferred embodiment, the surface structure of the master is manufactured by direct laser writing, gray scale lithography or ultra-precise machine tool processing.
The beneficial effects of the utility model are as follows: the immersion type continuous plane type diffraction beam splitter has the advantages that the whole plane type is excessively smooth and has no step structure, the whole diffraction efficiency can reach more than 95%, the uniformity error among orders can be less than 5%, and the beam splitting uniformity is good.
The submerged continuous surface type diffraction beam splitter has the advantages that the corresponding sagittal height of the surface type is improved by several times compared with the original sagittal height, and the difficulty of surface type processing is obviously reduced.
Drawings
FIG. 1 is a schematic structural diagram of a single periodic structure of an immersion type continuous surface diffraction beam splitter according to embodiment 1 of the present application;
FIG. 2 is a multi-period array diagram of an immersion continuous surface type diffraction beam splitter as described herein;
FIG. 3 is a simulated view of an immersion continuous surface type diffraction beam splitter as described herein;
FIG. 4 is a schematic diagram of a two-dimensional beam splitting diffraction optical element produced by the method for producing an immersion type continuous plane type diffraction beam splitter according to the present application;
FIG. 5 is a schematic diagram of a diffraction optical element with linear beam splitting, which is obtained by the method for preparing an immersion type continuous plane type diffraction beam splitter;
FIG. 6 is a schematic structural diagram of a single periodic structure of an immersion type continuous surface diffraction beam splitter according to embodiment 4 of the present application;
FIG. 7 is a schematic diagram of step (2) in a method for preparing an immersion type continuous surface type diffraction beam splitter according to example 1 of the present application;
FIG. 8 is a schematic diagram of step (3) in a method for preparing an immersion type continuous surface type diffraction beam splitter according to example 1 of the present application;
in the figure: 1. a base structural layer; 2. an optical medium 1; 3. beam-splitting micro-lens surfaces; 4. an optical medium 2; 5. an upper base layer; 6. a master.
Detailed Description
In order that those skilled in the art will better understand the present application, a technical solution in the embodiments of the present application will be clearly and completely described in the following in connection with examples, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.
The utility model provides an immersion type continuous plane type diffraction beam splitter which is of a periodic structure and is composed of at least one single-periodic structure array.
The two dimension (Λx, Λy) period of the single periodic structure can be obtained according to the number of the orders of the design target and the included angle between the orders, and the two dimension (Λx, Λy) period satisfies the following conditions at normal incidence: Λ×sin (Θ) =n×λ, Λ is a period of the beam splitter surface type, θ is an included angle of diffraction orders, n is a diffraction order, and λ is an applicable wavelength.
A multi-period array of immersion continuous-face diffraction beam splitters described herein is shown in fig. 2.
Example 1
An immersion continuous surface type diffraction beam splitter as in embodiment 1, said diffraction beam splitter being comprised of an array of monocycle structures;
the monocycle structure sequentially comprises a substrate structure layer (glass layer) with the thickness of 2mm, an optical medium 1 (optical resin layer with the refractive index of 1.7) and an optical medium 2 (optical resin layer with the refractive index of 1.5) with the thickness of 20um from bottom to top, wherein the refractive indexes of the optical medium 1 and the optical medium 2 are different;
the optical medium 1 and the optical medium 2 are in beam-splitting micro-lens type, and the plane sagittal height h of the beam-splitting micro-lens type meets the following relation:
wherein:
λ represents a wavelength, and 633 nm is used as a reference wavelength in this embodiment;
n1 represents the refractive index of the optical medium 1;
n2 represents the refractive index of the optical medium 2.
The above formula calculates the plane sagittal height h range of 0-4 microns.
The method for preparing the immersion type continuous surface type diffraction beam splitter in embodiment 1 comprises the following steps:
(1) Making a master plate by laser direct writing, wherein the surface structure of the master plate is matched with the surface shape between the optical medium 1 and the optical medium 2;
(2) Placing a viscous optical medium 1 on the substrate structure layer, imprinting by using a master plate, filling the gap between the master plate and the substrate structure layer with the optical medium 1, heating for curing, and removing the master plate (shown in fig. 7);
(3) And (3) placing a viscous optical medium 2 on the substrate obtained in the step (2), stamping by adopting a horizontal master plate, and curing after the surface is leveled to obtain the immersed continuous plane type diffraction beam splitter (shown in figure 8).
The efficiency of each stage of the immersion type continuous plane type diffraction beam splitter described in embodiment 1 is shown in table 1, and the simulation diagram is shown in fig. 4.
TABLE 1
| |
4 | 3 | 2 | 1 | 0 | -1 | -2 | -3 | -4 |
| Diffraction efficiency | 0.2％ | 22.0％ | 0.6％ | 23.6％ | 0.9％ | 23.6％ | 0.6％ | 22.0％ | 0.2％ |
As can be seen from table 1 and fig. 3: the total efficiency of the continuous surface type diffraction beam splitter is higher than 90%, and the uniformity error among stages is smaller than 5%.
Example 2
An immersion continuous surface type diffraction beam splitter as in embodiment 2, said diffraction beam splitter being comprised of an array of monocycle structures;
the monocycle structure sequentially comprises a substrate structure layer (glass layer) with the thickness of 2mm, an optical medium 1 (optical resin layer with the refractive index of 1.50) and an optical medium 2 (optical resin layer with the refractive index of 1.45) with the thickness of 25um from bottom to top, wherein the refractive indexes of the optical medium 1 and the optical medium 2 are different;
the planar sagittal height h between the optical medium 1 and the optical medium 2 satisfies the following relation:
wherein:
λ represents a wavelength, and 633 nm is used as a reference wavelength in this embodiment;
n1 represents the refractive index of the optical medium 1;
n2 represents the refractive index of the optical medium 2.
The above formula calculates the plane sagittal height h range of 0-15 microns.
The method for preparing the immersion type continuous surface type diffraction beam splitter in embodiment 2 comprises the following steps:
(1) Making a master plate by laser direct writing, wherein the surface structure of the master plate is matched with the surface shape between the optical medium 1 and the optical medium 2;
(2) Placing a viscous optical medium 1 on the substrate structural layer, imprinting by adopting a master plate, filling the gap between the master plate and the substrate structural layer with the optical medium 1, heating and curing, and removing the master plate;
(3) Placing a viscous optical medium 2 on the substrate obtained in the step (2), stamping by adopting a horizontal master plate, and curing after the surface is leveled to obtain the immersed continuous plane type diffraction beam splitter.
Example 3
An immersion continuous surface type diffraction beam splitter as in embodiment 3, said diffraction beam splitter being comprised of an array of monocycle structures;
the single periodic structure comprises a lower antireflection film, a substrate structure layer (glass layer) with the thickness of 2mm, an optical medium 1 (optical resin layer with the refractive index of 1.7) and an optical medium 2 with the thickness of 20um (optical resin layer with the refractive index of 1.5) from bottom to top, wherein the refractive indexes of the optical medium 1 and the optical medium 2 are different, and the upper antireflection film is arranged on the substrate structure layer;
the planar sagittal height h between the optical medium 1 and the optical medium 2 satisfies the following relation:
wherein:
λ represents a wavelength, and 633 nm is used as a reference wavelength in this embodiment;
n1 represents the refractive index of the optical medium 1;
n2 represents the refractive index of the optical medium 2.
The above formula calculates the plane sagittal height h range of 0-4 microns.
(1) Making a master plate by laser direct writing, wherein the surface structure of the master plate is matched with the surface shape between the optical medium 1 and the optical medium 2;
(2) Placing a viscous optical medium 1 on the substrate structural layer, imprinting by adopting a master plate, filling the gap between the master plate and the substrate structural layer with the optical medium 1, heating and curing, and removing the master plate;
(3) Placing a viscous optical medium 2 on the substrate obtained in the step (2), imprinting by adopting a horizontal master plate, and curing after the surface is leveled;
(4) And plating a lower antireflection film and an upper antireflection film on the lower surface of the base structure layer and the upper surface of the optical medium 2 respectively to obtain the immersed continuous plane type diffraction beam splitter.
Example 4
An immersion continuous surface type diffraction beam splitter as in embodiment 4, said diffraction beam splitter being comprised of an array of monocycle structures;
the monocycle structure sequentially comprises a substrate structure layer (glass layer) with the thickness of 2mm, an optical medium 1 (optical resin layer with the refractive index of 1.50) and an optical medium 2 (optical resin layer with the refractive index of 1.45) with the thickness of 30um from bottom to top, wherein the refractive indexes of the optical medium 1 and the optical medium 2 are different, and an upper substrate layer (optical plastic layer) with the thickness of 2 mm;
the planar sagittal height h between the optical medium 1 and the optical medium 2 satisfies the following relation:
wherein:
λ represents a wavelength, and 633 nm is used as a reference wavelength in this embodiment;
n1 represents the refractive index of the optical medium 1;
n2 represents the refractive index of the optical medium 2.
The above formula calculates the plane sagittal height range h to be 0-15 microns.
The method for preparing the immersion type continuous surface type diffraction beam splitter described in the embodiment 4 comprises the following steps:
(1) Making a master plate by laser direct writing, wherein the surface structure of the master plate is matched with the surface shape between the optical medium 1 and the optical medium 2;
(2) Placing a viscous optical medium 1 on the substrate structural layer, imprinting by adopting a master plate, filling the gap between the master plate and the substrate structural layer with the optical medium 1, heating and curing, and removing the master plate;
(3) Placing a viscous optical medium 2 on the substrate obtained in the step (2), imprinting by adopting a horizontal master plate, and curing after the surface is leveled;
(4) And adhering an upper substrate layer on the upper surface of the optical medium 2 to obtain the immersed continuous plane diffraction beam splitter.
The preparation method of the immersion type continuous plane type diffraction beam splitter can also be used for manufacturing diffraction optical elements with different optical effects, such as two-dimensional beam splitting, linear beam splitting, special patterns and the like.
A simulation of the resulting diffractive optical element with two-dimensional beam splitting was made as shown in fig. 4.
A simulation image of the resulting diffractive optical element having linear beam splitting was produced as shown in fig. 5.
The foregoing is merely a preferred embodiment of the present utility model, and it should be noted that modifications and additions may be made to those skilled in the art without departing from the method of the present utility model, which modifications and additions are also to be considered as within the scope of the present utility model.
Claims (6)
1. An immersion continuous surface type diffraction beam splitter, characterized in that the diffraction beam splitter is composed of at least one single periodic structure array;
the single-period structure sequentially comprises a substrate structure layer, an optical medium 1 and an optical medium 2 from bottom to top, wherein the refractive indexes of the optical medium 1 and the optical medium 2 are different;
the planar sagittal height h between the optical medium 1 and the optical medium 2 satisfies the following relation:
wherein:
lambda represents the wavelength;
n1 represents the refractive index of the optical medium 1;
n2 represents the refractive index of the optical medium 2.
2. An immersion type continuous surface type diffraction beam splitter as claimed in claim 1, further comprising a lower antireflection film and an upper antireflection film, wherein the lower antireflection film is covered on the lower surface of the base structure layer, and the upper antireflection film is covered on the upper surface of the optical medium 2.
3. An immersion continuous surface type diffraction beam splitter as claimed in claim 1, wherein the base structure layer is a quartz layer, a glass layer or an optical plastic layer; the thickness of the base structure layer is 2-3mm.
4. An immersion type continuous surface type diffraction beam splitter according to claim 1, wherein the optical medium 1 is optical glass, optical plastic or optical resin, and the refractive index difference between the optical medium 1 and air is 0.4-1.2.
5. The immersion type continuous surface type diffraction beam splitter as claimed in claim 4, wherein the optical medium 2 is optical glass, optical plastic or optical resin, and the refractive index difference between the optical medium 1 and the optical medium 2 is 0-0.9; the thickness of the optical medium 2 is 20-30um.
6. An immersion continuous surface type diffraction beam splitter as claimed in claim 1, further comprising an upper base layer covering the upper surface of the optical medium 2;
the upper substrate layer is a quartz layer, a glass layer or an optical plastic layer; the thickness of the upper basal layer is 2-3mm.
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