CN116661156B - Grating structure, diffraction optical waveguide and display device - Google Patents
Grating structure, diffraction optical waveguide and display device Download PDFInfo
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- CN116661156B CN116661156B CN202310911520.7A CN202310911520A CN116661156B CN 116661156 B CN116661156 B CN 116661156B CN 202310911520 A CN202310911520 A CN 202310911520A CN 116661156 B CN116661156 B CN 116661156B
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
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- 229910003460 diamond Inorganic materials 0.000 description 1
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- 229910000449 hafnium oxide Inorganic materials 0.000 description 1
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
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Abstract
The application provides a grating structure, a diffraction optical waveguide and display equipment, wherein the grating structure comprises a plurality of periodically arranged structural units arranged on the surface of a waveguide substrate, the structural units comprise a first part and a second part, the first part covers and is attached to the surface of the waveguide substrate, the second part is attached to and at least surrounds three surfaces of the first part, the refractive index of the first part is smaller than that of the second part, and the volume ratio of grating teeth of the structural units to the first part is more than or equal to 3. The grating structure provided by the application has higher diffraction efficiency, better uniformity distribution and convenient process.
Description
Technical Field
The present application relates to the field of diffractive waveguides, and in particular, to a grating structure, a diffractive optical waveguide, and a display device.
Background
With the recent development of technology, technologies such as Virtual Reality (VR), augmented Reality (AR) and Mixed Reality (MR) have gradually entered each industry, and diffractive optical waveguide is an important ring in terms of augmented reality. In general, a diffraction optical waveguide requires a higher diffraction efficiency and a better uniformity distribution to achieve a better display effect. In general, the higher the grating index, the higher the diffraction efficiency and the better the spectral/angular bandwidth. Resin materials are widely used to produce grating structures based on the advantage that they can be processed using nanoimprint processes with mass productivity, but such materials have lower refractive indices and thus lower performance ceilings. Another type of inorganic material with higher refractive index in the visible light band can be used as a grating material, such as titanium oxide, hafnium oxide, tantalum pentoxide and the like, and the performance of the inorganic material can be greatly improved, but the inorganic material cannot be processed by adopting a nano imprinting process with mass production, and the inorganic material needs to be processed by adopting a patterning and etching process, so that the process is complex and difficult. Therefore, it is desirable to provide a grating structure with high diffraction efficiency, good uniformity distribution, and convenient processing.
Disclosure of Invention
Aiming at the problems in the prior art, the application provides the grating structure which can achieve higher diffraction efficiency and better uniformity distribution and is convenient and fast in preparation process and suitable for mass production.
The application provides a grating structure, which comprises a plurality of periodically arranged structural units arranged on the surface of a waveguide substrate, wherein the structural units comprise a first subsection and a second subsection, the first subsection covers and is attached to the surface of the waveguide substrate, the second subsection is attached to and at least surrounds three surfaces of the first subsection, the refractive index of the first subsection is smaller than that of the second subsection, and the volume of the first subsection is smaller than that of the second subsection, so that the volume ratio of grating teeth of the formed structural units to the first subsection is more than or equal to 3;
the grating structure comprises a plurality of subareas, wherein the duty ratio and/or the height of the first subarea in the grating structure in at least two subareas are different, so that the diffraction efficiency of each subarea on light is not identical;
when the first subsection is of a rectangular structure, the duty ratio of the first subsection is less than 60%; the height of the first subsection is less than or equal to 100nm; when the first subsection is of a blaze structure, the height of the first subsection is less than or equal to 200nm; the height of the first subsection is the dimension of the first subsection in the normal direction of the surface of the waveguide substrate;
the refractive index of the first subsection ranges from 1.5 to 2.0, and the refractive index of the second subsection is larger than 1.9.
Optionally, the duty cycle and/or the height of the first subsection in the grating structure is graded so that the diffraction efficiency of the grating structure is graded in the direction of the duty cycle and/or the height grading.
Optionally, the height of each structural unit in the grating structure is kept uniform, and the height of each structural unit is the dimension of the structural unit in the normal direction of the surface of the waveguide substrate.
Optionally, the first subsection is processed by a nanoimprint process, and the second subsection is formed on the first subsection in a covering manner.
The present application provides a diffractive optical waveguide comprising a waveguide substrate, an in-coupling grating and an out-coupling grating, at least one of the in-coupling grating and the out-coupling grating comprising a grating structure as described above; alternatively, the diffractive optical waveguide comprises a waveguide substrate, an in-coupling grating, a turning grating and an out-coupling grating, at least one of the in-coupling grating, the turning grating and the out-coupling grating comprising a grating structure as described above.
Optionally, thicknesses of the second parts in the coupling-in grating, the turning grating and the coupling-out grating in a normal direction of the surface of the waveguide substrate are the same; or the thicknesses of the second parts in the coupling-in grating, the turning grating and the coupling-out grating in the normal direction of the surface of the waveguide substrate are not identical, the thicknesses of the second parts in the coupling-in grating in the normal direction of the surface of the waveguide substrate are identical, the thicknesses of the second parts in the turning grating in the normal direction of the surface of the waveguide substrate are identical, and the thicknesses of the second parts in the coupling-out grating in the normal direction of the surface of the waveguide substrate are identical.
The present application provides a display device including: the device comprises a device body, a projection optical machine and the diffraction optical waveguide arranged on the device body.
The grating structure provided by the application is designed to comprise two parts with different refractive indexes, the first part is covered and attached to the surface of the waveguide substrate, the grating structure can be processed by adopting a nanoimprint process, the volume or size of the limited first part is smaller (even far smaller) than that of the grating structure in the prior art, the smaller first part is formed, after the structure of the first part is formed, the patterning and etching process can be avoided, the second part is directly formed on the first part, the process is simplified, the difficulty is reduced, particularly the difficulty of imprinting is reduced, the volume ratio of the formed grating teeth to the first part is limited, the volume of the first part is small, the volume of the second part is large, even the volume of the first part is far smaller than that of the second part, the diffraction efficiency is improved by controlling the volume ratio of the first part and the second part, and particularly the volume ratio of the limited grating teeth to the first part is more than or equal to 3. Because the refractive index of the second subsection is larger than that of the first subsection, light is firstly incident into the second subsection and then transmitted to the first subsection through the second subsection, and thus the effective refractive index of the grating structure can be improved on one hand by reasonably selecting the volume ratio of the grating teeth to the first subsection, more light can be coupled into the waveguide substrate, and the diffraction efficiency of the grating structure is improved; on the other hand, the diffraction characteristics of the grating structure on light rays with different fields of view are effectively improved, the sensitivity on the angle of view of incident light rays is reduced, the uniformity of the grating structure in the whole field of view range is improved, and meanwhile, the difficulty of an imprinting process can be reduced, so that the method is suitable for batch imprinting processes and the performance of gratings is ensured.
The diffractive optical waveguide and the display device provided by the application comprise the grating structure, and have the advantages of the grating structure.
Drawings
For a clearer description of embodiments of the application or of the solutions of the prior art, the drawings that are required to be used in the description of the embodiments or of the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the application, and that other drawings can be obtained, without the inventive effort, from the structures shown in these drawings, for a person skilled in the art;
FIG. 1 is a schematic diagram of a grating structure according to an embodiment of the present application;
FIG. 2 is a schematic diagram showing the relationship between diffraction efficiency and angle of view when changing parameters of a grating structure according to an embodiment of the present application;
FIG. 3 is a diagram showing the relationship between diffraction efficiency and angle of view of a pure low refractive index grating structure according to an embodiment of the present application when changing parameters;
FIG. 4 is a diagram showing the relationship between diffraction efficiency and angle of view of a pure high refractive index grating structure according to an embodiment of the present application when changing parameters;
FIG. 5 is a schematic diagram showing the performance of a grating structure with different parameters according to an embodiment of the present application;
FIG. 6 is a schematic diagram showing the performance of a grating structure with different parameters according to another embodiment of the present application;
FIG. 7 is a schematic diagram of a highly modulated structure of a first subsection of a grating structure according to an embodiment of the present application;
FIG. 8 is a schematic diagram of a duty cycle modulation of a first division of a grating structure according to an embodiment of the present application;
fig. 9 is a schematic diagram of a structure of duty cycle and highly simultaneous modulation of a first subsection of a grating structure according to an embodiment of the present application.
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 below with reference to the accompanying drawings in which 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 those skilled in the art based on the embodiments of the present application without making any inventive effort, shall fall within the scope of the present application.
It should be noted that the terms "first," "second," and the like herein are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the application described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The application provides a grating structure, referring to fig. 1, the grating structure 100 comprises a plurality of periodically arranged structural units 110 arranged on the surface of a waveguide substrate 200, the structural units 110 comprise a first part 111 and a second part 112, the first part 111 covers and is attached to the surface of the waveguide substrate 200, the second part 112 is attached to and at least surrounds three surfaces of the first part 111, the refractive index of the first part 111 is smaller than that of the second part 112, and the volume ratio of grating teeth of the structural units to the first part 111 is greater than or equal to 3.
In practice, the surface of the second section 112 remote from the first section 111 is stepped; so that the diffraction efficiency of the grating structure unit is higher than that of the smooth surface structure, and the diffraction efficiency of the grating structure is improved as a whole.
Based on the scheme, the grating structure is arranged to comprise two parts with different refractive indexes, the first part is covered and attached to the surface of the waveguide substrate, the grating structure can be obtained by adopting a nanoimprint process, after the first part is formed, the patterning and etching processes can be avoided, the second part is directly formed on the first part, the process is simplified, and the process difficulty is reduced. In addition, as the refractive index of the second part is larger than that of the first part, and the light is firstly incident into the second part and then transmitted to the first part through the second part, the volume of the first part is smaller than that of the second part, even far smaller than that of the second part, and the effective refractive index of the grating structure can be improved by reasonably selecting the volume ratio of the grating teeth to the first part, so that more light can be coupled into the waveguide substrate, and the diffraction efficiency of the grating structure is improved; on the other hand, the diffraction characteristics of the grating structure on the light rays with different fields of view can be effectively improved, the sensitivity on the angle of view of the incident light rays is reduced, and the uniformity of the grating structure in the whole field of view is improved.
It should be noted that, in terms of size, compared with the grating structure formed by using one material (such as a low refractive index resin material or a high refractive index inorganic material) in the prior art, in the embodiment of the present application, the size of the first part in the structural unit of the grating structure is much smaller, and the whole formed by the first part and the second part is the grating structure having the diffraction effect on light. Moreover, after the first subsection is designed into a structure with a smaller size (smaller volume), the volume of the grating teeth of the grating unit structure is larger than that of the first subsection, and even the grating teeth are far larger than that of the first subsection, so that diffraction efficiency and uniformity can be improved, and a better effect is obtained.
The grating structure may be a one-dimensional grating or a two-dimensional grating, as an implementation. When the grating structure is a one-dimensional structure, the first subsection may be a rectangular structure, a sloped quadrilateral structure, a blazed structure, a stepped structure, a trapezoid structure, or the like. In the case of a two-dimensional grating structure, the cross-sectional shape of the first subsection in the structural unit of the grating structure may be circular, elliptical, square, diamond, etc. The refractive index of the first subsection is lower than that of the second subsection, and typically the refractive index of the first subsection may range from 1.5 to 2.0, and the refractive index of the second subsection is typically greater than 1.9. Illustratively, the first subsection may be a resin material and the second subsection may be an inorganic material.
In order to obtain higher diffraction efficiency and better uniformity, the volume ratio of the grating teeth to the first branches in the structural unit of the grating structure should be greater than or equal to 3, and in terms of variation trend, the greater the volume ratio of the grating teeth to the first branches, the better the performance of the grating structure, the smaller the duty ratio and the smaller the height of the first branches in the structural unit of the grating structure provided by the embodiment of the application, and the larger the thickness of the second branches. For example, when the first subsection in the structural unit of the grating structure is in a rectangular structure, the duty ratio of the first subsection is less than 60%, and the height is less than or equal to 100nm; when the first subsection is a blazed structure in the structural unit of the grating structure, the height of the first subsection is less than or equal to 200nm; the thickness of the second subsection in the structural unit of the grating structure is more than or equal to 50nm.
With continued reference to FIG. 1, the first subsection has a duty cycle W 1 /T，W 1 The width of the first subsection, i.e. the dimension of the first subsection in the direction of the period of the grating structure, T is the period of the grating structure. The height of the first subsection is H, i.e. the dimension of the first subsection in the direction of the normal to the surface of the waveguide substrate. The thickness of the second portion includes W 21 、W 22 、W 23 、W 24 I.e. the dimension of the second subsection in the vertical direction from the first subsection and the surfaces of the waveguide substrate. W is practically 21 =W 22 Or W 23 =W 24 Can be used forImplementation site W 21 =W 22 And W is 23 =W 24 Further, there may be W 21 =W 22 =W 23 =W 24 . The grating depth of the grating structure is the distance between the top surface of the grating teeth and the bottom surface of the grating groove, and is equal to the height of the first subsection.
Illustratively, referring to fig. 1, the first subsection of the structural unit of the grating structure of the present application is a portion surrounded by a black solid line frame, and the second subsection of the structural unit of the grating structure of the present application is a portion surrounded by a black dot-dash frame.
Referring to FIG. 2, a diagram shows the duty cycle W of a first subsection in changing the structural unit of the grating structure 1 T and the thickness W of two sides of the second part 21 、W 22 The diffraction efficiency is plotted against the angle of view when the other parameters of the grating structure remain unchanged. Wherein, the period T=286 nm of the grating structure, the height H=40 nm of the first subsection, the up-down thickness W of the second subsection 23 =W 24 =60 nm, i.e. the depth of the grating structure is 40nm, the first fraction refractive index is 1.9, and the second fraction refractive index is 2.4. The abscissa of each sub-graph in fig. 2 is the field angle, and the ordinate is the diffraction efficiency; the duty ratio of the first subsection corresponding to each column of subgraphs is consistent, and the duty ratio of the first subsection corresponding to each column of subgraphs is gradually increased from left to right, and is sequentially 0%, 10%, 20%, 30%, 40% and 50%; two side thicknesses W of the second subsection corresponding to each row of subgraph 21 /W 22 The thicknesses of the two sides of the second subsection corresponding to each row of subgraph are gradually increased from top to bottom, and the thicknesses are 0nm, 10nm, 20nm, 30nm, 40nm, 50nm and 60nm in sequence.
Fig. 3 and 4 show a schematic diagram of diffraction efficiency versus angle of view for a pure low refractive index grating structure and a pure high refractive index grating structure, respectively, as the duty cycle is varied. Wherein, the grating period is 286nm, the grating depth is 40nm, the refractive index of the pure low refractive index grating structure is 1.9, and the refractive index of the pure high refractive index grating structure is 2.4. The duty ratio of the first division corresponding to each sub-graph is gradually increased from left to right, and is sequentially 0%, 10%, 20%, 30%, 40% and 50%.
As is evident from comparing fig. 2, 3 and 4, for a resin grating with a refractive index of 1.9, the efficiency is only 9% and the uniformity is only 25% by modulating the duty cycle at a period of 286nm and a grating height of 40 nm; for a high refractive index grating with a refractive index of 2.4, the efficiency can reach 27.5%, and the uniformity can reach 53%. For grating structures comprising two refractive indices, at a second partial thickness W 21 /W 22 The grating structure has the advantages that the grating teeth of the first subsection are larger than the grating teeth of the second subsection, so that the effects that the grating with a relatively pure low refractive index is better in performance and the grating with a relatively pure high refractive index is similar in performance can be achieved when the space ratio of the grating teeth in the structural unit of the grating structure to the first subsection is larger, and even the grating with a relatively pure high refractive index is better in uniformity in certain cases. Such as: referring to column 2, row 7 subgraphs, at duty cycle W 1 T=10% thickness W 21 =W 22 When the volume ratio of the grating teeth to the first subsection is approximately 13, the average efficiency value of the grating structure is 22.2%, the uniformity reaches 83%, the average efficiency value is close to that of the pure high-refractive-index grating, and even the uniformity is better than that of the pure high-refractive-index grating. Referring again to column 3, line 5 subgraphs, at duty cycle W 1 At/t=20%, thickness W 21 =W 22 When the volume ratio of the grating teeth to the first subsection is approximately 6, the average efficiency of the grating structure is 19.9%, the uniformity is 65%, the average efficiency is close to that of the pure high-refractive-index grating, and even the uniformity is better than that of the pure high-refractive-index grating. The average value of the efficiency is the average value of the diffraction efficiency of the full field, and the uniformity is the ratio of the minimum diffraction efficiency to the maximum diffraction efficiency in the full field.
Referring to fig. 5, a graph of grating structure performance versus the same grating depth, second division thickness, and first division duty cycle is shown. In this example, the first subsection refractive index is 1.7, the height of the first subsection is 40nm, the second subsection refractive index is 2.4, and the grating period is 300nm. The first subsection duty ratio in the first grating structure is 10%, the thickness of the second subsection is 60nm, the volume ratio of grating teeth to the first subsection is 12.5, the average efficiency value is 21.7%, and the uniformity is 77.8%. The first subsection duty ratio in the grating structure II is 20%, the thickness of the second subsection is 50nm, the volume ratio of the grating teeth to the first subsection is 6, the average efficiency value is 19.2%, and the uniformity is 78.0%. The first subsection duty ratio in the grating structure III is 40%, the thickness of the second subsection is 20nm, the volume ratio of the grating teeth to the first subsection is 2, the average efficiency value is 6.0%, and the uniformity is 8.4%. It can be seen that the volume ratio of the grating teeth of the first and second structural units to the first subsection of the grating structure is greater than 3, the average efficiency is close to that of the pure high refractive index grating, and the uniformity is superior to that of the pure high refractive index grating. The volume ratio of the grating teeth of the structural unit to the first subsection in the grating structure III is less than 3, and the average efficiency and uniformity are not as good as those of a pure high-refractive-index grating.
Referring to fig. 6, a graph of grating structure performance versus the same grating depth, second division thickness, and first division duty cycle is shown. In this example, the first fraction refractive index is 1.9, the second fraction refractive index is 2.4, the first fraction height is 80nm, and the grating period is 280nm. The first subsection duty ratio in the grating structure IV is 30%, the thickness of the second subsection is 50nm, the volume ratio of the grating teeth to the first subsection is 3.6, the average efficiency value is 41.9%, and the uniformity reaches 79.3%. In the fifth grating structure, the duty ratio of the first subsection is 45%, the thickness of the second subsection is 30nm, the volume ratio of the grating teeth to the first subsection is 2, the average efficiency is 28.8%, and the uniformity is 31.6%. It can be seen that the volume ratio of the grating teeth of the four structural units of the grating structure to the first subsection is greater than 3, and the average value and uniformity of the efficiency are superior to those of the pure high-refractive-index grating; the volume ratio of the grating teeth of the five structural units of the grating structure to the first subsection is less than 3, and the average efficiency value is close to that of a pure high-refractive-index grating, but the uniformity is not as good as that of the pure high-refractive-index grating.
In one embodiment, the grating structure comprises a plurality of segments, and the first segment of the grating structure in at least two segments has a different duty cycle and/or height, so that the diffraction efficiency of each segment on light is not identical.
The grating structure comprises a plurality of partitions, the duty ratio of a first partition in the grating structure in at least two partitions is different, and then the duty ratio of the unit structure is modulated, so that the diffraction efficiency of different areas of the grating structure on the grating can be modulated, and the diffraction uniformity of the grating structure is improved.
Illustratively, the grating structure comprises a plurality of partitions, and the heights of the first partitions in the grating structure in at least two partitions are different, so that the grating depth of the unit structure can be modulated, thereby modulating the diffraction efficiency of different areas of the grating structure on the grating and improving the diffraction uniformity of the grating structure.
In some examples, the duty cycle and the height of the first subsection may also be modulated simultaneously.
In some examples, the duty cycle and/or the height of the first subsection within each subsection are consistent.
In some embodiments, referring to fig. 7, the heights of the individual structural elements within the grating structure remain uniform, the heights of the structural elements being the dimensions of the structural elements in the direction normal to the waveguide substrate surface. That is, the thickness of the second portion of the grating structure at different locations (thickness W in FIG. 1 23 ) Different.
Further in some embodiments, as shown in FIG. 8, a structure is provided in which the duty cycle of a first subsection of the grating structure is modulated, the duty cycle of different grating structures is different, and the thickness of a second subsection of the grating structure is different (thickness W in FIG. 1 23 ) The same applies.
In some embodiments, referring to FIG. 9, the thickness of the second subsection in each structural element within the grating structure (thickness W in FIG. 1 23 ) And keep the same. The grating structure process is more convenient.
In both embodiments, the duty cycle and/or the grating depth of the grating unit structure can also be modulated when the duty cycle and/or the height of the first subsection is modulated.
Illustratively, the surface of the second section remote from the first section is stepped; so that the diffraction efficiency of the grating structure unit is higher than that of the smooth surface structure, and the diffraction efficiency of the grating structure is improved as a whole.
It should be noted that, in the embodiment of the present application, the tooth shape of the grating teeth in the structural unit of the grating structure may be consistent with the shape of the first section. For example, the second portion may be conformal to the first portion or the second portion may not be substantially the same vertical dimension as the first portion and the surfaces of the waveguide substrate. The tooth shape of the grating teeth in the structural unit of the grating structure may be inconsistent with the shape of the first subsection, for example, the tooth shape of the grating teeth is a trapezoid mechanism, and the first subsection is a rectangular structure. The high and duty cycle of the first subsection and the volume ratio of the grating teeth to the first subsection are optimized for different grating tooth shapes, so that a good effect can be achieved.
In other examples, the duty cycle and/or height of the first subsection in the grating structure is graded such that the diffraction efficiency of the grating structure is graded along the direction of the duty cycle and/or height grading. The duty cycle and/or the grating depth of the grating unit structure can also be modulated gradually at the duty cycle and/or the height of the first subsection. Thus, negative effects caused by parameter mutation can be avoided, and imaging effect is improved. Gradation here refers to a continuous change, but is not limited to absolute continuity in a mathematical sense.
The embodiment of the application also provides a diffraction optical waveguide, which comprises a waveguide substrate, an in-coupling grating and an out-coupling grating, or comprises the waveguide substrate, the in-coupling grating, the turning grating and the out-coupling grating, wherein at least one of the in-coupling grating, the turning grating and the out-coupling grating comprises the grating structure in any one example.
Further, optionally, the thicknesses of the second sections of the coupling-in grating, the turning grating and the coupling-out grating in the normal direction of the surface of the waveguide substrate are the same; or the thicknesses of the second parts in the coupling grating, the turning grating and the coupling grating in the normal direction of the surface of the waveguide substrate are not identical, and the thicknesses of the second parts in the coupling grating in the normal direction of the surface of the waveguide substrate are identical, and the thicknesses of the second parts in the turning grating in the normal direction of the surface of the waveguide substrate are identical, and the thicknesses of the second parts in the coupling grating in the normal direction of the surface of the waveguide substrate are identical. Namely the thickness of the second sections of the coupling-in grating, the turning grating and the coupling-out grating is completely the same; or the thickness of the second part of one of the coupling-in grating, the turning grating and the coupling-out grating is different, and the thicknesses of the other two parts are the same; or the second partial thickness of the coupling-in grating, the turning grating and the coupling-out grating is different. But the second part thickness remains uniform in the respective areas. In this way, the profile of the first subsection can be replicated onto the grating structure when modulating its profile parameters (e.g. duty cycle, depth, etc.).
The embodiment of the application also provides a display device, which comprises: the device body, the projection optical machine and the diffraction optical waveguide arranged on the device body.
In one embodiment, the display device is a near-eye display device comprising a frame and a lens, the lens comprising a diffractive optical waveguide.
The display device may also be a heads-up display device, as may be implemented.
The foregoing describes specific embodiments of the present application. It is to be understood that the application is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the application. The embodiments of the application and the features of the embodiments may be combined with each other arbitrarily without conflict.
Claims (7)
1. A grating structure comprising a plurality of periodically arranged structural units arranged on the surface of a waveguide substrate, wherein the structural units comprise a first subsection and a second subsection, the first subsection covers and is attached to the surface of the waveguide substrate, the second subsection is attached to and at least surrounds three surfaces of the first subsection, the refractive index of the first subsection is smaller than that of the second subsection, and the volume of the first subsection is smaller than that of the second subsection, so that the volume ratio of grating teeth of the formed structural units to the first subsection is more than or equal to 3;
the grating structure comprises a plurality of subareas, wherein the duty ratio and/or the height of the first subarea in the grating structure in at least two subareas are different, so that the diffraction efficiency of each subarea on light is not identical;
when the first subsection is of a rectangular structure, the duty ratio of the first subsection is smaller than 60%, and the height of the first subsection is smaller than or equal to 100nm; when the first subsection is of a blaze structure, the height of the first subsection is less than or equal to 200nm; the height of the first subsection is the dimension of the first subsection in the normal direction of the surface of the waveguide substrate; the thickness of the second subsection in the structural unit is greater than or equal to 50nm;
the refractive index of the first subsection ranges from 1.5 to 2.0, and the refractive index of the second subsection is larger than 1.9.
2. A grating structure according to claim 1, wherein the duty cycle and/or height of the first subsection in the grating structure is graded such that the diffraction efficiency of the grating structure is graded in the direction of the duty cycle and/or height grading.
3. The grating structure of claim 2, wherein a height of each of the structural units within the grating structure is uniform, the height of the structural unit being a dimension of the structural unit in a direction normal to the waveguide substrate surface.
4. The grating structure of claim 1, wherein the first segment is fabricated using a nanoimprint process and the second segment is overlaid on the first segment.
5. A diffractive optical waveguide, characterized in that it comprises a waveguide substrate, an in-coupling grating and an out-coupling grating, at least one of which comprises a grating structure according to any of claims 1-4; alternatively, the diffractive optical waveguide comprises a waveguide substrate, an in-coupling grating, a turning grating and an out-coupling grating, at least one of the in-coupling grating, the turning grating and the out-coupling grating comprising the grating structure of any one of claims 1-4.
6. The diffractive optical waveguide according to claim 5, wherein the thicknesses of the second sections of the coupling-in grating, the turning grating, and the coupling-out grating in the normal direction of the waveguide substrate surface are the same; or the thicknesses of the second parts in the coupling-in grating, the turning grating and the coupling-out grating in the normal direction of the surface of the waveguide substrate are not identical, the thicknesses of the second parts in the coupling-in grating in the normal direction of the surface of the waveguide substrate are identical, the thicknesses of the second parts in the turning grating in the normal direction of the surface of the waveguide substrate are identical, and the thicknesses of the second parts in the coupling-out grating in the normal direction of the surface of the waveguide substrate are identical.
7. A display device, the display device comprising: a device body, a projection light engine, and the diffractive optical waveguide according to claim 5 or 6 provided on the device body.
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| CN120802427B (en) * | 2025-09-16 | 2025-11-11 | 北京阿法龙科技有限公司 | A high diffraction efficiency grating waveguide structure and its fabrication method |
| CN120891582A (en) * | 2025-09-26 | 2025-11-04 | 歌尔光学科技有限公司 | Optical waveguide structure, optical module and intelligent glasses |
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