CN217279003U - Frequency domain filter based on super surface, optical 4f system and optical module - Google Patents
Frequency domain filter based on super surface, optical 4f system and optical module Download PDFInfo
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- CN217279003U CN217279003U CN202220230244.9U CN202220230244U CN217279003U CN 217279003 U CN217279003 U CN 217279003U CN 202220230244 U CN202220230244 U CN 202220230244U CN 217279003 U CN217279003 U CN 217279003U
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Abstract
The application provides a frequency domain filter, an optical 4f system and an optical module based on a super surface, which comprise a plurality of working units arranged in an array, wherein each working unit comprises a substrate and a super surface structure; the super-surface structure comprises at least one structural unit, and the structural unit comprises a nano-structure arranged on the surface of a substrate. The optical 4f system and the wafer packaging module thereof comprise an object space super-surface array which is arranged close to an object space in the optical system; an image space super-surface array disposed near an image space in the optical system; and the super-surface-based frequency domain filter is arranged between the object-side super-surface array and the image-side super-surface array. The frequency domain filter realized by the super surface has small volume and quick response; the optical 4f system based on the full super surface can be made into an array, the problem of large chromatic aberration of the traditional 4f system is solved, and different image processing can be simultaneously carried out on input images; the wafer level packaging has high alignment precision and small calibration difficulty.
Description
Technical Field
The application relates to a frequency domain filter based on a super surface, and an optical 4f system and an optical module provided with the frequency domain filter.
Background
The optical 4f system is a special and widely applied optical system, and when two coherent polarized lights are input, the input lights generate a diffraction spectrum on a screen through a special optical device, a cosine grating, a transformation plane and the like. The precise horizontal moving cosine grating can continuously change the phase difference of the diffraction orders of the two beams of light, thereby achieving the purpose of subtracting or adding the diffraction light intensity. The distance between two lenses with focal length f is 2f, and the object distance and the image distance are both f, so the system is called as a 4f system. The existing optical lens introduces optical path difference through gradual change of thickness, and has the disadvantages of large thickness and weight, high alignment difficulty, complex calibration, difficult array manufacture and difficult integration.
SUMMERY OF THE UTILITY MODEL
In view of the above technical problems, a first aspect of the present application provides a frequency domain filter based on a super-surface, including the following technical solutions:
a substrate;
at least one working unit disposed on the substrate, the working unit including a super-surface structure;
the super-surface structure comprises at least one structural unit, the structural unit comprises a nano structure arranged on the surface of the substrate, and the frequency domain filter can realize filtering aiming at different frequencies through corresponding arrangement of the structural unit.
Preferably, a plurality of working units are arranged on the substrate, and the plurality of working units are arranged in an array.
Preferably, the plurality of working units are identically formed.
Preferably, the plurality of working units are configured differently.
Preferably, the structural unit is a regular hexagon, and each vertex and the central position of the regular hexagon are provided with at least one nano structure.
Preferably, the structural unit is a square, and at least one nanostructure is arranged at each vertex and the central position of the square.
Preferably, the nanostructure is a polarization-dependent structure or a polarization-independent structure;
wherein the polarization-dependent structure comprises nanofins or nanoellipsoids and the polarization-independent structure comprises nanocylinders or nanosquares.
A second aspect of the present application provides a super-surface based optical 4f system, comprising:
an object side superlens disposed near an object side in the optical system and including at least one object side working unit;
an image side superlens disposed near an image side in the optical system and including at least one image side working unit;
a metasurface-based frequency domain filter according to any of the first aspects of the present application, arranged between the object side superlens and the image side superlens;
the object space working unit and the image space working unit both comprise a super-surface structure, the super-surface structure comprises at least one structural unit, and the structural unit comprises a nano structure arranged on the surface of the substrate.
Preferably, the distance between the object side and the object side superlens, the distance between the object side superlens and the frequency domain filter based on the supersurface, the distance between the frequency domain filter based on the supersurface and the image side superlens, and the distance between the image side superlens and the image side are equal.
Preferably, the object side superlens includes a plurality of object side working units, and the image side superlens includes a plurality of image side working units;
the working units of the frequency domain filter based on the super surface, the object side working unit and the image side working unit are in one-to-one correspondence and respectively form respective optical 4f systems.
Preferably, the object side superlens can realize Fourier transform of plane waves of object side image information through corresponding arrangement of structural units on the object side superlens; the image side superlens can realize inverse Fourier transform to restore a clear image of a processed object side image through corresponding arrangement of the structural units on the image side superlens.
Preferably, the object side superlens and the super surface based frequency domain filter
And/or
A spacing layer is arranged between the image space super lens and the super surface-based frequency domain filter;
the spacing layer is filled with air or a substance transparent to the operating band.
A third aspect of the present application provides a wafer-level packaged optical module comprising a super-surface based optical 4f system as described in any of the preceding claims.
The beneficial effects of this application technical scheme are: the frequency domain filter realized by the super surface has small volume and quick response, and the super surface manufactured based on the semiconductor process has higher centering precision compared with the traditional lens; the optical 4f system based on the full-super-surface can be made into an array, so that the problem of large chromatic aberration of the traditional 4f system is solved, and different image processing can be simultaneously carried out on input images; the wafer level packaging has high alignment precision and small calibration difficulty.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
FIG. 1 is a schematic diagram of a prior art optical 4f system;
FIG. 2 is a schematic diagram of a prior art 4f system based on graded index materials;
FIG. 3 is a schematic view of a super-surface based optical 4f system according to the present disclosure;
FIG. 4 is a distribution diagram of each working unit in a frequency domain filter based on a super-surface according to the present disclosure;
fig. 5A, fig. 5B, fig. 5C, and fig. 5D are schematic diagrams of a super-surface structure unit in the technical solution of the present application, wherein:
FIG. 5A is a schematic diagram of a regular hexagonal structural unit;
FIG. 5B is a schematic diagram of a square structural unit;
FIG. 5C is a schematic view of a nanopillar in a building block;
FIG. 5D is a schematic diagram of a nanofin in a building block;
FIG. 6 is a schematic view of an optical 4f system wafer package structure according to the present disclosure;
FIG. 7 is a distribution diagram at a frequency domain filter of the present application;
fig. 8A and 8B are input and output images in an embodiment of the present application, wherein:
FIG. 8A is an object side input image;
fig. 8B is an image side output image.
The drawing is marked with: the optical lens system comprises a frequency domain filter based on a super surface 1, an object space super lens 2, an image space super lens 3, an object space 4 and an image space 5.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.
The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context. The features of the following examples and embodiments may be combined with each other without conflict.
The technical solution of the present application will be clearly and completely described below with reference to the accompanying drawings and exemplary embodiments.
Example 1
The embodiment provides a super-surface based frequency domain filter, which comprises:
the device comprises a plurality of working units arranged in an array, wherein each working unit comprises a substrate and a super-surface structure;
the super-surface structure comprises at least one structural unit, and the structural unit comprises a nano-structure arranged on the surface of a substrate. The function of this frequency-domain filter is to perform the following filtering transformation on the optical wave in the optical 4f system:
in the formula, λ is the working wavelength, and f is the focal length.
Compared with the prior art, the frequency domain filter realized by the super surface has smaller volume and faster response.
Specifically, as shown in fig. 5A, the structural unit is a regular hexagon, and at least one nanostructure is disposed at each vertex and at a central position of the regular hexagon.
Specifically, as shown in fig. 5B, the structural unit is a square, and at least one nanostructure is disposed at each vertex and the center of the square.
Specifically, the nanostructure may be a polarization-dependent structure or a polarization-independent structure;
wherein, as shown in fig. 5C and 5D, the polarization-dependent structure comprises nanofins or nano elliptic cylinders, and the polarization-independent structure comprises nano cylinders or nano square cylinders.
Example 2
The present embodiment provides a super-surface based optical 4f system, comprising:
an object side superlens disposed close to an object side in the optical system;
an image side superlens disposed close to an image side in the optical system;
the super-surface based frequency domain filter as described in the previous embodiments and any one of the preferred embodiments thereof, disposed between the object side superlens and the image side superlens.
Specifically, the distance between the object space and the object space superlens, the distance between the object space superlens and the frequency domain filter based on the super surface, the distance between the frequency domain filter based on the super surface and the image space superlens, and the distance between the image space superlens and the image space are all equal, the distances are f, and f is the focal length of the object space superlens or the image space superlens.
The super-surface structure in the super-surface based frequency domain filter faces towards the object side and also faces towards the image side.
Specifically, the object side super lens and the image side super lens are both provided with a plurality of working units; the working units of the frequency domain filter based on the super surface, the working units of the object side super lens and the working units of the image side super lens are in one-to-one correspondence to form a plurality of groups of optical 4f systems, the object side super lens can perform Fourier transformation on light waves, and the image side super lens can perform inverse Fourier transformation on the light waves.
Specifically, a spacing layer is arranged between the object side superlens and the frequency domain filter based on the super surface and/or between the image side superlens and the frequency domain filter based on the super surface; the spacer layer is filled with air or a substance transparent to the operating band. In the embodiment, the working wave band of the system is visible light (380-760 nm), near infrared, far infrared and terahertz.
Specifically, the object side superlens and/or the image side superlens include: a substrate and a super-surface structure on the surface of the substrate; the super-surface structure comprises structural units arranged in an array; the structural unit comprises a plurality of nanostructures; the super-surface structure is arranged on the surface of the object side super-lens facing the image side, and the super-surface structure is arranged on the surface of the image side super-lens facing the object side. In short, the super-surface structures on the object side and the image side face the inner side of the whole body, and the function of the super-surface structures is to protect the super-surface structures on the super-surface structures.
The working principle of the embodiment is as follows:
the plane wave recording the object image information is subjected to Fourier transform at a focal plane (namely, a frequency domain filter) behind the object super lens, and is subjected to inverse Fourier transform at the focal plane (namely, an image side) behind the image super lens after passing through the frequency domain filter, so that a clear image of the processed object image is restored.
Mathematically:
after passing through object super lens f (t) ═ f (jw) (Eq-1)
After passing through a frequency domain filter G (w) ((jw)) (Eq-2)
After passing through an image space superlens f 1 (t)＝F -1 {G(w)·F(jw)} (Eq-3)
If the output light field signal is proportional to the differential of the input light field signal (for edge detection), i.e.:
fourier transform of first order differential:
the corresponding inverse fourier transform:
comparing Eq-3 to Eq-6 results in a filter function for the frequency domain filter that should be:
in the formula, λ is the working wavelength, and f is the focal length.
Supplementary explanation for the present embodiment:
different sets of working units can be arranged for the object, the image side superlens and the frequency domain filter, as shown in fig. 4, and further, a plurality of sets of optical 4f systems are formed. Can be used as an array form, and is suitable for being integrated into a wafer due to the characteristics of the processing technology.
In this embodiment, each working unit, including the object, image side super lens and frequency domain filter, includes a super surface structure, and can modulate the incident light according to the super surface structure unit thereon. The super-surface structure unit comprises a full-medium or plasma nano antenna, and the phase, amplitude, polarization and other characteristics of light can be directly adjusted and controlled. According to the phase required by the nano-structure under different wavelengths, the nano-structure with the closest phase can be searched in the nano-structure database. In an embodiment, the nanostructure is an all-dielectric structural unit, having high transmittance in the operating band, and the selectable materials include: titanium oxide, silicon nitride, fused silica, aluminum oxide, gallium nitride, gallium phosphide, amorphous silicon, crystalline silicon, hydrogenated amorphous silicon, and the like. The nano-structure units are arranged in an array, the super-surface structure units are regular hexagons and/or squares, and a nano-structure is arranged at the central position of each super-surface structure unit or at the central position and the vertex position of each super-surface structure unit. FIGS. 5A, 5B, 5C, and 5D provide regular hexagonal, square arrangements of super-surface structured cells and schematic illustrations of nano-structured cells. The nano-structure can be a polarization-dependent structure, such as a nano-fin, a nano-elliptic cylinder and the like, and the structure exerts a geometric phase on incident light; the nanostructure may also be a polarization independent structure, such as a nanocylinder or a nanocylinder, which imparts a propagation phase to the incident light.
Example 3
The present embodiment provides a wafer-level packaged optical module, including the optical system 4f based on super-surface as described in any one of the previous embodiments and any one of the preferred embodiments. The optical 4f system array sequentially comprises a layer of super lens array (object side super lens); a spacer layer (fill medium); a layer of frequency domain filter array; a spacer layer (fill medium); a layer of superlens array (image side superlens). Wherein: working units in the three layers of superlenses correspond to each other one by one, and each group forms an optical 4f system; each frequency domain filtering unit can execute different functions, each optical 4f system based on the frequency domain filtering unit can execute different functions, and different image processing functions can be simultaneously carried out on an object input image after the optical 4f system is made into an array.
Example 4
The present embodiment provides an embodiment of image edge extraction by a super-surface-based optical 4f system, where the first super-surface and the third super-surface correspond to an object-side super-lens and an image-side super-lens in other embodiments, respectively, and the second super-surface corresponds to a frequency domain filter array or a frequency domain filter.
The focal length of the first super surface is the same as that of the third super surface, f is 10mm, and the side length is 2 mm. The first super surface adopts a quartz substrate and an amorphous silicon nano-column structure, the units are arranged according to a regular hexagon, the period is 450nm, and the height of the nano-column is 600 nm. The third super surface uses a quartz substrate and an amorphous silicon nano-pillar structure, the units are arranged according to a regular pentagon, the period is 500nm, and the height of the nano-pillar is 550 nm. The side length of the second super-surface frequency domain filter is 2 mm. The second super surface adopts a quartz substrate and an amorphous silicon nano-column structure, the units are arranged according to a regular hexagon, the period is 450nm, and the height of the nano-column is 500 nm. The filling medium is air. The object space is located 10mm in front of the first super surface, and the image space is located 10mm behind the third super surface. The distribution of the frequency domain filtering super surface obtained by substituting the wavelength and the focal length into Eq-7 and Eq-2 for the near infrared light with the working band of 940nm is shown in FIG. 7, and when the object side input image is shown in FIG. 8A, the image side output image is shown in FIG. 8B.
In the embodiments, the frequency domain filter realized by the super surface has small volume and quick response; the optical 4f system based on the full-super-surface can be made into an array, so that the problem of large chromatic aberration of the traditional 4f system is solved, and different image processing can be simultaneously carried out on input images; the wafer level packaging has high alignment precision and small calibration difficulty.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.
Claims (13)
1. A metasurface-based frequency domain filter, comprising:
a substrate;
at least one working unit disposed on the substrate, the working unit including a super-surface structure;
the super-surface structure comprises at least one structural unit, the structural unit comprises a nano structure arranged on the surface of the substrate, and the frequency domain filter can realize filtering aiming at different frequencies through corresponding arrangement of the structural unit.
2. The super-surface based frequency domain filter according to claim 1, wherein a plurality of working units are disposed on the substrate and arranged in an array.
3. The super-surface based frequency domain filter of claim 2, wherein the plurality of working units are identically constructed.
4. The super-surface based frequency domain filter of claim 2, wherein the plurality of working units are configured differently.
5. The super-surface based frequency domain filter according to claim 1, wherein the structural units are regular hexagons, and at least one nanostructure is disposed at each vertex and center of the regular hexagons.
6. The super-surface based frequency domain filter according to claim 1, wherein the structural unit is a square, and at least one nanostructure is disposed at each vertex and center position of the square.
7. The super-surface based frequency domain filter of claim 1, wherein the nano-structures are polarization dependent structures or polarization independent structures;
wherein the polarization-dependent structure comprises nanofins or nanoellipsoids and the polarization-independent structure comprises nanocylinders or nanosquares.
8. A super-surface based optical 4f system, comprising:
an object side superlens disposed near an object side in the optical system and including at least one object side working unit;
an image side superlens disposed near an image side in the optical system and including at least one image side working unit;
the hypersurface-based frequency domain filter of any one of claims 1-7 disposed between the object side superlens and image side superlens;
the object space working unit and the image space working unit both comprise a super-surface structure, the super-surface structure comprises at least one structural unit, and the structural unit comprises a nano structure arranged on the surface of the substrate.
9. The metasurface-based optical 4f system of claim 8, wherein a distance between the object side and object side superlens, a distance between the object side superlens and the metasurface-based frequency domain filter, a distance between the metasurface-based frequency domain filter and image side superlens, and a distance between the image side superlens and image side are equal.
10. The super-surface based optical 4f system of claim 8, wherein the object side superlens comprises a plurality of object side working units, and the image side superlens comprises a plurality of image side working units;
the working units of the frequency domain filter based on the super surface, the object side working unit and the image side working unit are in one-to-one correspondence and respectively form respective optical 4f systems.
11. The metasurface-based optical 4f system of claim 8, wherein the object side superlens enables fourier transformation of plane waves of object side image information by corresponding arrangement of structural elements thereon; the image side superlens can realize inverse Fourier transform to restore the processed object side image through corresponding arrangement of the structural units on the image side superlens.
12. The super-surface based optical 4f system of claim 8, wherein between the object side superlens and the super-surface based frequency domain filter
And/or
A spacing layer is arranged between the image space super lens and the super surface-based frequency domain filter;
the spacer layer is filled with air or a substance transparent to the operating band.
13. A wafer level packaged optical module comprising the super-surface based optical 4f system according to any one of claims 8 to 12.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115327678A (en) * | 2022-09-01 | 2022-11-11 | 天津山河光电科技有限公司 | Bidirectional optical path system, optical module and optical equipment |
| US11927769B2 (en) | 2022-03-31 | 2024-03-12 | Metalenz, Inc. | Polarization sorting metasurface microlens array device |
| US11978752B2 (en) | 2019-07-26 | 2024-05-07 | Metalenz, Inc. | Aperture-metasurface and hybrid refractive-metasurface imaging systems |
| US11988844B2 (en) | 2017-08-31 | 2024-05-21 | Metalenz, Inc. | Transmissive metasurface lens integration |
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2022
- 2022-01-27 CN CN202220230244.9U patent/CN217279003U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11988844B2 (en) | 2017-08-31 | 2024-05-21 | Metalenz, Inc. | Transmissive metasurface lens integration |
| US11978752B2 (en) | 2019-07-26 | 2024-05-07 | Metalenz, Inc. | Aperture-metasurface and hybrid refractive-metasurface imaging systems |
| US11927769B2 (en) | 2022-03-31 | 2024-03-12 | Metalenz, Inc. | Polarization sorting metasurface microlens array device |
| CN115327678A (en) * | 2022-09-01 | 2022-11-11 | 天津山河光电科技有限公司 | Bidirectional optical path system, optical module and optical equipment |
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