CN114815056B - Sandwich efficient emission grating antenna based on staggered offset and manufacturing method thereof - Google Patents
Sandwich efficient emission grating antenna based on staggered offset and manufacturing method thereof Download PDFInfo
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Abstract
The invention provides an interlayer efficient emission grating antenna based on staggered offset and a manufacturing method thereof. The antenna comprises from bottom to top: the substrate, buried layer, dielectric layer have double grating structure and waveguide layer in the dielectric layer, double grating structure includes top layer grating array and bottom layer grating array, bottom layer grating array and top layer grating array parallel arrangement have certain offset each other, bottom layer grating array adopts nano-grating structure, the waveguide layer is located between bottom layer grating array and the top layer grating array. The waveguide layer can reduce the crosstalk problem caused by the grating antenna array; the staggered offset periodic arrangement of the bottom layer grating and the top layer grating can effectively reduce the downward diffraction intensity of the grating, the novel bottom layer grating structure can enable light reflection to be more concentrated, the upward diffraction efficiency of the top layer grating is improved, the directivity of light radiation to free space is enhanced, and the upper limit of the length of the traditional grating is broken through. The invention has simple manufacturing method, high production efficiency and lower cost.
Description
Technical Field
The invention belongs to the technical field of photoelectricity, and particularly relates to an interlayer efficient emission grating antenna based on staggered offset and a manufacturing method thereof.
Background
With the development of technologies such as autopilot, unmanned aerial vehicle, intelligent robot, free space optical communication and optical coherence imaging, in the laser radar field, especially an optical phased array (OpticalPhaseArray, OPA) based on silicon-based waveguide technology is widely studied with low cost and excellent COMS process compatibility. The first full set Cheng Erwei waveguide chip using a silicon-based optical phased array was reported in 2015, followed by a 512-optical channel-based silicon-based OPA chip in 2019, and demonstrated in the indoor 50 meter range. However, silicon-based OPA chips still have some drawbacks. Firstly, limiting the working wavelength, wherein a silicon-based OPA chip mainly works in a communication wave band, and compared with the wavelength range of 850nm-1100nm, the laser is difficult to realize high-power output, and an external optical amplifier (SOA) is needed, so that the complexity and the cost of a system are increased; the photoelectric detector working in 1550nm wave band is mainly composed of InGaAs detector and Ge detector, and has better optical communication capability and low multiplication coefficient compared with silicon-based detector. Secondly, silicon has the limitation of the optical characteristics, silicon has stronger nonlinear effect than silicon nitride, and the light transmission aspect is limited, so that the application capability of the OPA chip in distance detection and light communication transmission is limited.
The beam scanning performance of the optical phased array is closely related to the quality of the grating antenna, and the grating can diffract incident light due to the periodically arranged teeth, grooves, lines or array structure in the grating or on the surface of the grating, so that the grating is an important optical element. In an optical phased array, diffraction efficiency (directivity) of grating radiation into free space affects the detection distance of a beam, and the far-field divergence angle of the grating affects the resolution of beam scanning. In the traditional grating, the substrate material can absorb downward light radiated by the grating due to the self characteristics of the substrate material, so that the light transmission loss is serious, the length of the manufactured grating is limited, and meanwhile, the upward diffraction efficiency is lower. Therefore, how to improve the diffraction efficiency of the radiation free space of the interlayer grating and reduce the divergence angle of the far field is an important technical difficulty of the optical phased array, and how to manufacture the optical phased array according to the existing etching technology is also an important technical problem of the development of the semiconductor technology.
Disclosure of Invention
In order to solve the problems, the invention provides an interlayer efficient emission grating antenna based on staggered offset and a manufacturing method thereof. Compared with a single-layer grating, the technical scheme of the invention has higher transmissivity and smaller far-field divergence angle, thereby effectively enhancing the radiation distance of the grating, improving the resolution ratio during beam scanning, and the manufacturing method has the advantages of high repeatability, simplicity and the like.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
an interleaved offset based sandwich high efficiency transmit grating antenna comprising, from bottom to top: the dual-grating structure comprises a top-layer grating array and a bottom-layer grating array which are arranged in parallel and have a certain offset, the bottom-layer grating array adopts a nano-grating structure, and the waveguide layer is arranged between the bottom-layer grating array and the top-layer grating array.
Further, the offset is 0.13 to 0.16 μm.
Further, the bottom layer grating array adopts one of the following structures: the device comprises a conical bottom layer grating array, a concave arc bottom layer grating array and a right inclined bottom layer grating array.
Further, the tapered grating comprises a rectangular part and a bottom tapered part at the upper part, the ratio of the height of the rectangular part to the height of the tapered part is 9:11, the angle of the arc surface at the top of the concave arc-shaped bottom layer grating is 32-38 degrees, and the inclination angle of the top surface of the right-inclined grating structure is 30-32 degrees.
Further, the waveguide layer comprises a front-end rectangular waveguide, a conical linear waveguide and a rectangular waveguide positioned between the double-layer gratings.
Further, the waveguide etching height of the waveguide layer is 0.8 μm, and the width of the rectangular waveguide is 0.38 μm; the length of the conical linear waveguide is 2 mu m, the width of the input end is 0.38 mu m, and the width of the output end is 2 mu m; the grating period in the double grating structure is 0.65-0.7 mu m, the duty ratio is 0.66, the grating width is 2 mu m, and the distance between the grating and the waveguide is 50nm; the etching depth of the bottom grating array is 0.6 mu m; the top layer grating array etch depth was 0.46 μm.
The invention also provides a manufacturing method of the interlayer high-efficiency emission grating antenna based on staggered offset, which comprises the following steps:
step S1: forming a dielectric layer on a substrate, wherein the refractive index of the dielectric layer is between the refractive index of the waveguide layer and the refractive index of air;
step S2: etching a waveguide layer with a double-grating structure on the surface of the dielectric layer, etching a grating structure at the vertical upper and lower parts of the waveguide, and enabling the top grating to have a certain transverse offset with the bottom grating during etching;
step S3: and removing the photoresist on the surface of the waveguide and cleaning to complete the device.
As a further improvement of the present invention, in the step S2, the waveguide layer is formed into a silicon nitride film on the dielectric layer by a chemical vapor deposition process, and is etched in combination with a standard photolithography process.
As a further improvement of the invention, the bottom layer grating is finished by the modes of photoresist coating, exposure, development and ion etching, and the bottom layer grating is realized by combining the beam oblique incidence mode and the normal incidence mode of ion etching; the top layer grating adopts the same etching mode as the bottom layer grating.
As a further improvement of the invention, the bottom layer grating comprises one of a conical structure, a concave arc structure and a right inclined structure, when the conical structure is adopted, the bottom layer grating is incident from a rectangular grating half waist prescription, the oblique incidence angle is 43-46 degrees, the etching length is 0.33 mu m, and the vertical incidence etching length is 0.6 mu m; when a concave arc structure is adopted, oblique incidence and top vertical incidence from the left side and the right side of the rectangular grating are completed, the oblique incidence angle is 15 degrees, the etching length is 0.2 mu m, and the vertical etching depth is 0.25 mu m; when a right inclined structure is adopted, the light enters obliquely from the upper left, the incident angle is 30-32 degrees, the etching length is 0.4 mu m, and the vertical etching length is 0.41 mu m; the ion etching mode adopted by the top layer grating is vertical incidence, and the etching length is 0.46 mu m.
The beneficial effects of the invention are as follows:
1. the waveguide layer in the structure of the invention comprises a rectangular waveguide and a conical linear waveguide, so that the crosstalk problem caused by the grating antenna array can be reduced; the waveguide layer is vertically arranged in the upper and lower interlayer grating structure, the staggered offset periodic arrangement of the bottom grating and the top grating can effectively reduce the downward diffraction intensity of the grating, the novel bottom grating structure can enable light reflection to be more concentrated, the upward diffraction efficiency of the top grating is improved, the directivity of light radiation to free space is enhanced, the resolution ratio of far-field light beams is improved, the upper limit of the length of the traditional grating is broken through, and the problems of low efficiency and short length of a conventional grating antenna are solved.
2. The thickness parameters of the substrate dielectric layer, the width, the thickness and the height of the waveguide are adjusted, and parameters such as grating period, duty ratio, etching depth and the like are optimized to be matched with each other, so that diffraction energy of grating radiation upwards can be improved, directivity can be enhanced, detection distance can be enhanced, and far-field beam divergence angle is smaller.
3. The manufacturing method of the sandwich high-efficiency emission grating antenna forms multiple layers of photoresist with different energies by adopting the SOI substrate, and exposes and etches the bottom layer grating for multiple times, thereby forming a series of nano pattern structures on the substrate. The invention can complete the manufacture of the high-directivity sandwich grating antenna by adopting a simple process, and has high production efficiency and lower cost.
Drawings
Fig. 1 is a schematic three-dimensional structure diagram of an interlayer efficient transmission grating antenna based on staggered offset.
Fig. 2 is a schematic cross-sectional structure of three different bottom layer grating embodiments, where (a) is a schematic bottom layer tapered grating structure, (b) is a schematic bottom layer concave arc grating structure, and (c) is a schematic bottom layer right-inclined grating structure.
Fig. 3 is a schematic diagram of electric field transmission of a tapered linear waveguide in a waveguide layer.
Fig. 4 is a graph comparing directivity of a transmission grating antenna with an underlying grating structure to an operating wavelength.
Fig. 5 is a graph comparing directivity versus operating wavelength for three different configurations of bottom emission gratings versus a conventional dual-layer grating antenna (rectangular).
Fig. 6 is a visual far-field diagram (a) and a grating exit angle Theta (b) Phi (c) range diagram of the interlayer high-efficiency emission grating antenna based on staggered offset, provided by the invention, under the working wavelength of 1550 nm.
Fig. 7 is a graph of the length versus optical power of an interleaved high efficiency transmission grating antenna based on staggered offset.
Fig. 8 is a schematic diagram of a beam scanning range of the staggered offset-based sandwich high-efficiency transmission grating antenna provided by the invention under a working band (1450 nm-1600 nm).
Fig. 9 shows far field test data of an interlayer high-efficiency transmitting grating antenna based on staggered offset, wherein (a) is far field beam test data, and (b) is beam actual measurement scanning range data.
Fig. 10 is a schematic diagram of a plasma etching process for preparing the staggered offset-based sandwich high-efficiency emission grating antenna provided by the invention.
Reference numerals illustrate:
the optical waveguide comprises a 1-substrate layer, a 2-buried layer, a 3-dielectric layer, a 4-linear taper waveguide, a 5-top layer grating array, a 6-taper bottom layer grating array, a 7-waveguide layer input end, an 8-concave arc bottom layer grating array and a 9-right inclined bottom layer grating array.
Detailed Description
The technical scheme provided by the present invention will be described in detail with reference to the following specific examples, and it should be understood that the following specific examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. Other advantages and effects of the present invention will be readily apparent to those skilled in the art from the present disclosure. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Please refer to fig. 1 to 9. It should be noted that the illustrations provided in the present embodiment are merely schematic illustrations of the basic concepts of the invention, and the components in the drawings are not drawn according to the number and size of components in the actual embodiment, but are merely illustrations of embodiments.
As shown in fig. 1, the interlayer efficient transmission grating antenna based on staggered offset provided in this embodiment includes from bottom to top: the substrate layer 1, the buried layer 2 and the dielectric layer 3 further comprise a double grating structure and a waveguide layer 7 located in the dielectric layer 3. The double-grating structure comprises a top-layer grating array 5 and a bottom-layer grating array, and the bottom-layer grating adopts a nano-grating structure and is used for radiating light signals in waveguide transmission upwards, so that the emission efficiency of the top-layer grating is improved. The bottom layer grating and the top layer grating are horizontally arranged with a certain offset, and the offset is 0.13-0.16 mu m.
The waveguide layer 7 comprises a rectangular waveguide at the front end, a conical linear waveguide 4 near the grating end and a rectangular waveguide part positioned between a top grating array and a bottom grating array in the double grating structure, wherein the waveguide etching height is 0.8 mu m, and the rectangular waveguide width is 0.38 mu m; the tapered linear waveguide had a length of 2 μm, an input end width of 0.38 μm and an output end width of 2 μm. The waveguide layer 7 is protected by a dielectric layer 3, wherein the refractive index of the dielectric layer 3 is smaller than the refractive index of the waveguide layer 7.
The substrate is an SOI substrate comprising a silicon single crystal bottom layer and a silicon single crystal top layer, and the total thickness of the substrate and the buried layer 2 is 2 mu m; the dielectric layer is made of silicon dioxide and has a thickness of 4 mu m; the double grating structure material is silicon nitride; the waveguide material is silicon nitride. The materials of the dielectric layer, substrate, dual grating and waveguide can be modified by those skilled in the art according to specific needs.
As shown in fig. 2, three possible embodiments of a sandwich-type high-efficiency transmission grating antenna based on staggered offset are shown. The three-dimensional structure of the bottom layer grating of the three embodiments is a conical bottom layer grating array 6 (fig. 2 (a)), a concave arc bottom layer grating array 7 (fig. 2 (b)), or a right-leaning bottom layer grating array 8 (fig. 2 (c)), respectively. The following is a one-to-one description of the cell structures in the three underlying grating arrays: in the conical bottom layer grating array, the whole shape of the conical grating is big and small, and in the figure, the conical grating comprises an upper rectangular part and a bottom conical part. The rectangular part has a height of 0.27 mu m, the tapered part has a height of 0.33 mu m, the ratio of the rectangular height to the tapered height of the lower grating is 9:11, the grating antenna with the rectangular part and the tapered part meeting the ratio can obtain the optimal directivity, and the diffraction performance is reduced when the ratio is too low. In the concave arc bottom layer grating array, the top of the concave arc grating structure is provided with a concave arc surface, and the concave surface of the concave arc grating structure is opposite to the direction of waveguide optical signal diffraction transmission. The angle of the arc surface is controlled within the range of 32-38 degrees, and the etching depth of the concave surface is 0.25 mu m. A concave surface within this parameter range may effectively reflect the portion of the waveguide where the optical signal interferes. When the arc angle is too large, the curvature of the concave surface is larger, so that light beam gathering reflection is easy to cause, and light leakage is caused when the top grating of the grating antenna exits due to the too large gathering energy; when the arc angle is too small, the concave features approach a plane and diffuse reflection is apparent as light reaches the face. In the right inclined bottom layer grating array, the top of the right inclined grating structure is provided with an inclined plane inclined downwards to the right, the inclined angle is 30-32 degrees, and the maximum diffraction directivity can be obtained in the range.
The grating period in the double grating structure is 0.65-0.7 mu m, the duty ratio is 0.66, the grating width is 2 mu m, and the distance between the grating and the waveguide is 50nm; the etching depth of the bottom grating 5 is 0.6 mu m; the etching depth of the top grating 6 is 0.46 mu m, the design parameter can maximally improve the upward radiation efficiency of the grating antenna, and the detection distance of beam detection can be obviously improved.
According to the embodiment, the continuous spectrum is adopted as a light source by the optical device manufacturing platform, the radiation end of the manufactured grating is monitored in real time, the influence of parameters on the transmission characteristic is analyzed, the grating antenna with high radiation efficiency is manufactured, and the working performance of the grating antenna is analyzed.
As shown in fig. 3 to 5, fig. 3 is an electric field transmission schematic diagram of a tapered linear waveguide of a waveguide layer, and the transmission mode of an optical signal in the waveguide is good, which can effectively reduce the crosstalk problem of a phased array due to a periodic structure. The grating antenna is a phased array light beam emitting device, the quality of the performance of the grating antenna directly determines the light beam emitting quality, the diffraction performance of the grating antenna can be reflected through a directional parameter, and a directional calculation formula is as follows:
and placing the grating in a three-dimensional characterization box, wherein Ttop is the grating diffraction energy detected by the top detector, tbottom is the grating diffraction energy detected by the bottom detector, and Tright is the scattering energy detected by the detector at the incident light. FIG. 4 is a graph of the directivity of an emission grating antenna with or without a bottom layer grating structure versus the operating wavelength, in FIG. 4, the advantage of a tapered bottom layer sandwich grating is more obvious than that of a traditional bottom layer grating, the directivity of the traditional grating is very poor and is between 30% and 50% in the operating band range of 1450nm and 1600nm, and the directivity of the sandwich grating with dislocation offset is all over 60%, wherein at the wavelength of 1.55 μm, the directivity efficiency of the sandwich grating (the bottom layer is tapered) is the highest and reaches 87.5%, which is an important index for light beam detection. FIG. 5 shows the relationship between the directivity of the bottom grating and the working wavelength of different structures, wherein the directivity of the concave arc bottom grating is lower than that of the conical bottom grating structure in the 1450 nm-1500 nm wave band and the 1560 nm-1600 nm wave band due to the fact that the concave is opposite to the direction of the diffraction transmission of the waveguide optical signal, and the directivity of the concave arc bottom grating is 92.5% when the working wavelength is 1.54 μm; the right inclined bottom grating structure has inclined plane with opposite diffraction transmission direction to the waveguide light signal, directivity lower than 50% in 1450-1470 nm band and directivity over 80% in the rest band. In combination, the sandwich grating antenna with the conical bottom layer is the best choice in the wave band range of 1450nm to 1600nm, and the structure has wider wavelength range tuning. In a specific wave band, the sandwich grating antenna with the bottom layer in a concave arc shape and the sandwich grating antenna with the bottom layer in a right inclination have higher directivity. The choice of underlying grating structure depends on the application.
As shown in fig. 6 to 9, the far field performance of the grating antenna was demonstrated in the structure of example 1. According to the equivalent medium theory, the effective refractive index of the grating is calculated through the following formula, wherein L is the offset of the sandwich grating, P is the grating period, and n1, n2 and n3 are the local effective refractive indexes of the grating solved by the eigenmodes under 1550nm wavelength.
After calculating the effective refractive index of the grating, the emission angle is calculated
Where Nc is the effective refractive index of the dielectric layer (SiO 2) and λ is the free space wavelength of light. For the controlled deflection of the beam at phase Φ, the method is represented by the formula
ΔΦ is a uniform phase difference between waveguides, d is a gap between two adjacent waveguides, and Wwg is a width of the waveguides. Fig. 6 is a normalized far field plot at a free space wavelength of 1550nn, and the grating exit angle case. According to the graph, the far-field divergence angle of the grating antenna is 3.85 degrees, if the divergence angle of the grating antenna is required to be further reduced, the length of the grating antenna is required to be increased, but the longer the grating antenna is, the better the grating antenna is, the relation diagram between the length of the grating antenna and the normalized optical power of the graph of fig. 7 shows that the optical power is reduced along with the length of the grating antenna, in order to ensure the optical power of more than 50%, the maximum length of the grating antenna can be 2mm, and the far-field divergence angle can reach 0.52 degrees; fig. 8 shows far field conditions of λ=1450 nm and λ=1600 nm, ΔΦ=0, and it can be seen from the graph that the scanning angle of the transverse field angle of the grating antenna in the wave band of 1450nm to 1600nm is 21.48 °, and fig. 9 shows the test data of the far field of the grating antenna structure of the present invention, and the full width at half maximum of the diffraction far field of the grating is 0.53cm; when the uniform phase difference between the waveguides is pi, the longitudinal field angle scanning angle range is 80 deg..
The embodiment of the invention also provides a manufacturing method of the staggered offset-based sandwich high-efficiency emission grating antenna, and the structure diagram of the staggered offset-based sandwich high-efficiency emission grating antenna manufactured by the embodiment can refer to fig. 1, 2 and 9, and the manufacturing method comprises the following steps:
step S1: providing a substrate layer positioned at the bottom, and forming a dielectric layer on the substrate, wherein the refractive index of the dielectric layer is between the refractive index of the waveguide layer and the refractive index of air;
step S2: etching a waveguide layer with a double grating structure on the surface of the dielectric layer, and etching the grating structure at the vertical upper and lower parts of the waveguide; wherein the waveguide layer is etched by chemical vapor deposition to form a silicon nitride film on the dielectric layer in combination with standard photolithographic processes.
In the step, the double grating structure is positioned on the upper layer and the lower layer of the waveguide layer vertically, the bottom grating is completed by the modes of photoresist coating, exposure, development and ion etching, and the conical structure, the concave arc structure and the right inclined structure of the bottom grating in the double grating structure are realized by the beam oblique incidence mode and the vertical incidence mode which need to be combined with ion etching; the top grating adopts the same etching mode as the bottom grating, a certain transverse offset is needed to be formed between the top grating and the bottom grating during etching, and the ion implantation mode adopts vertical incidence.
The concave arc structure, the right inclined structure and the conical structure of the bottom layer grating adopt ion etching modes of mixed etching of oblique incidence and vertical incidence, as shown in figure 10, wherein the right inclined grating structure needs to be obliquely incident from the upper left, the incidence angle is 30-32 degrees, the etching length is 0.4 mu m, and the vertical etching length is 0.41 mu m; the concave arc structure is required to be completed by oblique incidence from the left side and the right side of the rectangular grating and vertical incidence from the top end, the oblique incidence angle is 15 degrees, the etching length is 0.2 mu m, and the vertical etching depth is 0.25 mu m; the conical structure needs to be incident from the rectangular grating half waist prescription, the oblique incidence angle is 43-46 degrees, the etching length is 0.33 mu m, and the vertical incidence etching length is 0.6 mu m. The ion etching mode adopted by the top layer grating is vertical incidence, and the etching length is 0.46 mu m. The control of the incident angle is realized by strictly controlling the proportion of the shielding gas. The invention adopts SF 6 And C 4 F 8 The shape etching effect of the bottom grating can be controlled by adjusting the flow ratio of the two gases alternately introduced. When SF is 6 And C 4 F 8 When the ratio of (2) is less than 1, SF 6 Is far less than C 4 F 8 Gas and its preparation methodThe flow of the bottom grating is a conical structure; when the ratio is equal to 1, the air flow at two sides is the same, the incident angle changes the vertical incident mode, and a concave arc structure can be realized; and when the ratio is greater than 1, the grating structure is tilted right.
Step S3: and removing the photoresist on the surface of the waveguide and cleaning to complete the device.
It should be noted that the foregoing merely illustrates the technical idea of the present invention and is not intended to limit the scope of the present invention, and that a person skilled in the art may make several improvements and modifications without departing from the principles of the present invention, which fall within the scope of the claims of the present invention.
Claims (9)
1. An efficient sandwich transmission grating antenna based on staggered offset, which is characterized by comprising the following components from bottom to top: the device comprises a substrate, a buried layer and a dielectric layer, wherein the dielectric layer is internally provided with a double-grating structure and a waveguide layer, the double-grating structure comprises a top-layer grating array and a bottom-layer grating array, the bottom-layer grating array and the top-layer grating array are arranged in parallel and have a certain offset, the bottom-layer grating array adopts a nano-grating structure, and the waveguide layer is arranged between the bottom-layer grating array and the top-layer grating array; the bottom layer grating array adopts one of the following structures: the device comprises a conical bottom layer grating array, a concave arc bottom layer grating array and a right inclined bottom layer grating array.
2. The stagger offset-based sandwich high efficiency transmission grating antenna of claim 1, wherein the offset is 0.13-0.16 μm.
3. The staggered offset based sandwich high efficiency transmission grating antenna of claim 1, wherein the tapered bottom layer grating comprises an upper rectangular portion and a bottom tapered portion, the ratio of the rectangular portion height to the tapered portion height is 9:11, the angle of the arc surface at the top of the concave arc bottom layer grating is 32-38 °, and the tilt angle of the top surface of the right tilt bottom layer grating structure is 30-32 °.
4. The stagger offset based sandwich efficient transmission grating antenna of claim 1, wherein the waveguide layer comprises a front end rectangular waveguide, a tapered linear waveguide, and a rectangular waveguide between the bilayer gratings.
5. The stagger offset based sandwich efficient transmission grating antenna according to claim 4, characterized in that the waveguide layer waveguide etch height is 0.8 μm and the rectangular waveguide width is 0.38 μm; the length of the conical linear waveguide is 2 mu m, the width of the input end is 0.38 mu m, and the width of the output end is 2 mu m; the grating period in the double grating structure is 0.65-0.7 mu m, the duty ratio is 0.66, the grating width is 2 mu m, and the distance between the grating and the waveguide is 50nm; the etching depth of the bottom grating array is 0.6 mu m; the top layer grating array etch depth was 0.46 μm.
6. A method for manufacturing an interlayer high-efficiency transmission grating antenna based on staggered offset, which is used for manufacturing the interlayer high-efficiency transmission grating antenna based on staggered offset as claimed in any one of claims 1 to 5, and comprises the following steps:
step S1: forming a dielectric layer on a substrate, wherein the refractive index of the dielectric layer is between the refractive index of the waveguide layer and the refractive index of air;
step S2: etching a waveguide layer with a double-grating structure on the surface of the dielectric layer, etching a grating structure at the vertical upper and lower parts of the waveguide, and enabling the top grating to have a certain transverse offset with the bottom grating during etching;
step S3: and removing the photoresist on the surface of the waveguide and cleaning to complete the device.
7. The method for manufacturing the staggered offset-based sandwich high-efficiency transmission grating antenna according to claim 6, wherein the waveguide layer in the step S2 is formed by a chemical vapor deposition process to form a silicon nitride film on the dielectric layer, and the silicon nitride film is etched by combining a standard photolithography process.
8. The manufacturing method of the staggered offset-based interlayer high-efficiency emission grating antenna according to claim 6, wherein the bottom layer grating is completed in the modes of photoresist coating, exposure, development and ion etching, and the bottom layer grating is realized by combining an ion etching light beam oblique incidence mode and a vertical incidence mode; the top layer grating adopts the same etching mode as the bottom layer grating.
9. The method for manufacturing the staggered offset-based sandwich high-efficiency emission grating antenna according to claim 6 or 8, wherein the bottom layer grating comprises one of a conical structure, a concave arc structure and a right-angled structure, when the conical structure is adopted, the incidence is from a rectangular grating half waist prescription, the oblique incidence angle is 43-46 degrees, the etching length is 0.33 μm, and the vertical incidence etching length is 0.6 μm; when a concave arc structure is adopted, oblique incidence and top vertical incidence from the left side and the right side of the rectangular grating are completed, the oblique incidence angle is 15 degrees, the etching length is 0.2 mu m, and the vertical etching depth is 0.25 mu m; when a right inclined structure is adopted, the right inclined structure obliquely enters from the upper left, the incident angle is 30-32 degrees, the etching length is 0.4 mu m, and the vertical etching length is 0.41 mu m; the ion etching mode adopted by the top layer grating is vertical incidence, and the etching length is 0.46 mu m.
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