CN117148499A - Design method of diffraction optical waveguide - Google Patents
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/124—Geodesic lenses or integrated gratings
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- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
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- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
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- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
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- G—PHYSICS
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B2006/12083—Constructional arrangements
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- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
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Abstract
The invention relates to a design method of a diffraction optical waveguide, which comprises the following steps of setting a light beam transmission path and determining a coupling-in region, a turning region and a coupling-out region on a waveguide sheet; dividing grating partitions along the beam transmission path on the coupling-in region, the turning region and the coupling-out region respectively, and determining a blazed grating period, a blazed angle and a blazed angle required for forming the beam transmission path; determining diffraction efficiency of the grating partition based on preset calculation rules of the coupling-in region, the turning region and the coupling-out region respectively, and further determining duty ratio, blazed grating width and blazed grating depth required for achieving the diffraction efficiency; blazed gratings are correspondingly arranged on the grating subareas so as to form coupling-in gratings, turning gratings and coupling-out gratings in the coupling-in area, the turning area and the coupling-out area respectively, thereby obtaining the diffraction optical waveguide. The invention has the advantages of better light-emitting efficiency, uniformity, privacy, mass production economy and the like, and is suitable for mass industrialized production.
Description
Technical Field
The invention relates to the technical field of diffraction optical elements, in particular to a design method of a diffraction optical waveguide.
Background
Waveguides are currently the best augmented reality eyewear solution. The waveguide scheme is further classified into a geometric waveguide scheme, a diffractive optical waveguide scheme (relief grating waveguide scheme), and a volume hologram waveguide scheme. The geometric waveguide scheme generally comprises a sawtooth structure waveguide and a polarized film array reflector waveguide, wherein the polarized film array waveguide mainly uses a part of transmission part of reflection film mirrors of an array to achieve the purpose of displaying virtual information, and the polarized film array waveguide scheme has the advantages of light weight, large eye movement range and uniform color. The embossing grating waveguide scheme can be mass-produced by a nanoimprint process, and is of great interest to AR optical module manufacturers, and has the advantages of large field of view and large eye movement range, but also brings challenges to field of view uniformity and color uniformity, and meanwhile, the related micro-nano processing process is also a great challenge. The volume holographic waveguide solution has advantages in both color uniformity and implementation of monolithic full-color waveguides, but is currently limited in large scale mass production and large field of view.
Referring to fig. 1, at present, the main way to improve the light-emitting efficiency of the diffractive optical waveguide scheme is to use an inclined grating or blazed grating in the coupling-in region, so that the efficiency of the coupling-in portion can be greatly improved, but since uniformity and light efficiency are considered in both the turning region and the coupling-out region, a direct grating scheme is generally adopted, and the implementation is realized through a deep partition or duty ratio partition scheme. Due to the process limitations of height and duty cycle, the diffraction efficiency of a straight grating is generally low, and therefore, a large amount of light waste is caused in the turning region and the exit pupil region.
In order to improve the uniformity of the optical waveguide, the uniformity of the light output after each total reflection is ensured, in the existing grating design scheme, a turning region and a coupling region are designed into subareas with depth and variable duty ratio, and each area meets the conditions of longer light transmission distance and higher diffraction efficiency, so that the uniformity of the overall efficiency is ensured. However, to ensure uniformity of the amount of light output after each total reflection, the diffraction efficiency is less than 10% each time the light passes through the grating, resulting in a final light efficiency loss of more than 50%. This results in an extremely low overall efficiency of the diffractive optical waveguide, which makes it difficult to meet the requirements of consumer-grade applications; on the contrary, based on the design thought, if the light efficiency is simply required to be improved, the uniformity is greatly reduced, and the overall imaging effect is poor. Therefore, the design schemes of the traditional turning region and the coupling-out region are difficult to simultaneously consider the problems of light efficiency and uniformity, and the requirement on imaging quality is difficult to realize. In addition, the adoption of the depth-partition straight grating structure requires repeated exposure and etching in the actual template processing process, and the processing cost can be increased while the processing steps are increased. The mass production of the optical waveguide is not facilitated, and the improvement of the yield is also not facilitated.
Disclosure of Invention
The invention aims to solve the problems of the prior art, provides a design method of a diffraction optical waveguide, has the advantages of better light emitting efficiency, uniformity, privacy, mass production economy and the like, and is suitable for mass industrialized production.
The above object of the present invention is achieved by the following technical solutions:
a design method of diffraction optical waveguide includes the following steps,
s1, setting a light beam transmission path, and determining a coupling-in area, a turning area and a coupling-out area on a waveguide sheet;
s2, dividing grating partitions along the light beam transmission path on the coupling-in region, the turning region and the coupling-out region respectively, and determining a blazed grating period P, a blazed angle alpha and a blazed angle beta required for forming the light beam transmission path;
s3, determining diffraction efficiency T of the grating partition based on preset calculation rules of the coupling-in area, the turning area and the coupling-out area respectively, and further determining duty ratio f, blazed grating width l and blazed grating depth h required for achieving the diffraction efficiency T;
s4, a blazed grating is correspondingly arranged on the grating subarea so as to form a coupling-in grating, a turning grating and a coupling-out grating in the coupling-in area, the turning area and the coupling-out area respectively, and the diffraction optical waveguide is obtained.
By adopting the technical scheme, based on the design thought that blazed grating structures are adopted in the coupling-in area, the turning area and the coupling-out area, wherein the coupling-in area preferably adopts blazed gratings with consistent grating parameters, the turning area and the coupling-out area preferably adopt gradual-change blazed gratings, and the upper diffraction efficiency limit of the diffraction optical waveguide can be greatly improved; meanwhile, as the ultimate efficiency of the blazed grating is higher, a gradual change diffraction structure is formed by adjusting the duty ratio and the height of the blazed grating through a process, wherein the period P, the blazed angle alpha and the blazed angle beta of the blazed grating are kept unchanged in the whole grating partition, the duty ratio is changed, i.e. l and h are reduced according to the principle that P, alpha and beta are unchanged and the like, in an actual grating area, the depth h is linearly increased along the direction matched with a light beam transmission path, and l is correspondingly changed according to the similarity of triangles, so that the light emitting efficiency can be ensured, the light emitting uniformity can be improved, the brightness of an AR lens is greatly improved, and the method is suitable for large-scale industrial production; in addition, the design mode can effectively inhibit reverse transmission of light, and privacy of the AR glasses is improved; in addition, the gradual change blazed grating can be prepared once in the template processing process, the steps are not needed to be carried out for many times, the template processing cost can be greatly saved, the mass production yield is greatly improved, and the blazed grating structure is extremely friendly to imprinting, so that the service lives of the nano imprinting template and the soft film are prolonged, and the production cost is reduced.
Further, the coupling-in region, the turning region and the coupling-out region all adopt blazed grating structures, wherein the turning region and the coupling-out region adopt blazed gratings with duty ratio and depth variation, and the specific depth variation is selected according to the actual design requirement and is not limited to a certain mode, such as linearity, gradient gradual change and the like. The material type of the grating region can be resin material after embossing, high refractive index inorganic material after etching, or any material which can meet the manufacturing condition of the optical waveguide. The grating partition can be coated according to the requirements so as to improve the diffraction efficiency. In addition, the overall layout of the diffractive optical waveguide is not limited to the following manner, and any multi-region one-dimensional grating configuration capable of realizing complete two-dimensional pupil expansion is applicable.
Further, in the S1, the beam transmission path needs to satisfy the grating vector closing relationship, that is, the grating vectors of the coupling-in region, the turning region, and the coupling-out region, so as to form a closed triangle, so that the beams entering the coupling-in region can be coupled out from the coupling-out region at the same angle.
Further, grating vectors of the coupling-in region, the turning region and the coupling-out region sequentially follow a first vector direction, a second vector direction and a third vector direction, and the second vector direction intersects with the first vector direction and the third vector direction respectively to form an included angle of 30-60 degrees.
Further, in said S2, for the blazed grating of the coupling-in region, the blazed grating period P is controlled 1 =300 to 450nm, blaze angle α 1 =20 to 45°, glint angle β 1 =70~90°。
And/or, in the step S2, for the blazed grating of the turning region, controlling the blazed grating period P 2 =200 to 330nm, blaze angle α 2 =20 to 45°, glint angle β 2 =70~90°。
And/or, in said S2, for the blazed grating of the coupling-out region, controlling the blazed grating period P 3 =300 to 450nm, blaze angle α 3 =20 to 45°, glint angle β 3 =70~90°。
Further, in S2, a blazed grating period P and a blazed direction are determined according to a grating vector on the beam transmission path, and a blazed angle α and a blazed angle β are determined according to the diffraction efficiency distribution; wherein,
for blazed gratings of the coupling-in region, the blazed grating period P is controlled 1 =364 to 420nm, blaze angle α 1 =28 to 30°, glint angle β 1 =80~85°；
For blazed gratings in turning areas, the period P of the blazed gratings is controlled 2 =258 to 420nm, blaze angle α 2 =39 to 42°, glint angle β 2 =88~89°；
For blazed gratings of the coupling-out region, the blazed grating period P is controlled 3 =364 to 420nm, blaze angle α 3 =36 to 39 °, glint angle β 3 =85~88°。
Further, in the step S3, the preset calculation rule of the coupling-in area is that grating parameters of blazed gratings on two adjacent grating partitions are the same, and the maximum diffraction efficiency T is based on 1 Determining a duty cycle f 1 Blazed grating width l =100%, a 1 =f 1 *P 1 Blazed grating depth h 1 =l 1 *tanα 1 *tanβ 1 /（tanα 1 +tanβ 1 ）。
And/or in the step S3, the preset calculation rule of the turning region is to control the duty ratios on the adjacent two grating partitions to be different, and the energy of the light beam transmitted to the coupling-out region after the light beam is totally reflected in the turning region each time is approximately equal, so as to determine the diffraction efficiency T 2 =（N 2 -n 2 +1） -1 Duty cycle f 2 =39 to 68%, blazed grating width l 2 =f 2 *P 2 Blazed grating depth h 2 =l 2 *tanα 2 *tanβ 2 /（tanα 2 +tanβ 2 ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein N is 2 、n 2 The total number of diffraction of the beam in the turning region and the diffraction number at the current diffraction efficiency, respectively.
Further, for blazed gratings in the turning region, the depth h of the blazed grating 2 =105 to 180nm blazed grating depth h 2 Increasing in the second vector direction to ensure the diffraction efficiency T 2 Increasing from 10 to 50%. Wherein the increment is a linear increment, a step increment, or a curve increment along the second vector direction.
And/or in the step S3, the preset calculation rule of the coupling-out area is to control the duty ratios on the adjacent two grating partitions to be different, and the energy of the light beams coupled out of the optical waveguide after the light beams are totally reflected in the coupling-out area each time is approximately equal, so as to determine the diffraction efficiency T 3 =（N 3 -n 3 +1） -1 Duty cycle f 3 37-65%, blazed grating width l 3 =f 3 *P 3 Blazed grating depth h 3 =l 3 *tanα 3 *tanβ 3 /（tanα 3 +tanβ 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein N is 3 、n 3 The total number of diffraction of the beam in the turning region and the diffraction number at the current diffraction efficiency, respectively.
Further, for the blazed grating of the coupling-out region, the blazed grating depth h 3 =98 to 172nm blazed grating depth h 2 Increasing in the third vector direction to ensure the diffraction efficiency T 3 Increasing from 9 to 38%. Wherein the increment is linear increment, step increment or curve increment along the third vector direction.
Further, in the step S3, the coupling-in grating is disposed on the coupling-in region, and the coupling-in grating is used for coupling the light beam into the optical waveguide sheet and propagating the light beam in the optical waveguide sheet; the turning grating is arranged on the turning region and on one side or two sides of the coupling-in grating along the light beam transmission path, and the turning grating is used for receiving the light beam transmitted by the coupling-in grating and guiding the light beam to the coupling-out region; the coupling-out gratings are arranged on the coupling-out area and on one side of the turning grating along the light beam transmission path, and the coupling-out gratings are used for receiving the light beams transmitted by the turning grating and coupling the light beams out of the light waveguide sheet. Based on the light beam transmission rule, the two-dimensional pupil expansion effect is realized, namely, the light beam is ensured to be coupled out in the whole coupling-out area.
In summary, the beneficial technical effects of the invention are as follows: by adopting a gradual change blazed grating design mode in the turning region and the coupling-out region, on the premise of ensuring higher diffraction efficiency, the uniformity of light emitted from the turning region is regulated and controlled by utilizing a depth gradual change blazed grating structure, so that the imaging effect is comprehensively improved, and the method has the advantages of better light emitting efficiency, uniformity, privacy, mass production economy and the like, and is suitable for mass industrialized production.
Drawings
FIG. 1 is a graph of diffraction efficiency versus beam path distribution for a prior art diffractive optical waveguide in accordance with the background of the invention;
FIG. 2 is a graph showing diffraction efficiency of the diffractive optical waveguide according to the embodiment 1 of the present invention as a function of the transmission path of the light beam;
FIG. 3 is a schematic diagram of the structure of a blazed grating according to embodiment 1 of the present invention; wherein P, alpha, beta, l and h respectively represent blazed grating period, blazed angle, blazed grating width and blazed grating depth;
FIG. 4 is a graph of a fit of the diffraction efficiency and duty cycle of the diffractive optical waveguide of example 1 of the present invention; wherein, the fitting curve sequentially corresponds to blaze angles of 25 degrees, 30 degrees, 35 degrees, 40 degrees and 45 degrees from top to bottom;
FIG. 5 is a schematic view showing the structure of a diffractive optical waveguide according to embodiment 2 of the present invention;
fig. 6 is a schematic structural view of a diffractive optical waveguide according to embodiment 3 of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and detailed description in order to make the technical means, the creation characteristics, the achievement of the objects and the functions of the invention more clear and easy to understand.
Example 1: referring to fig. 2 and 3, a method for designing a diffractive optical waveguide according to the present invention includes the steps of,
s1, setting a light beam transmission path, and determining a coupling-in area, a turning area and a coupling-out area on a waveguide sheet;
s2, dividing grating partitions along a light beam transmission path on a coupling-in region, a turning region and a coupling-out region respectively, and determining a blazed grating period P, a blazed angle alpha and a blazed angle beta required for forming the light beam transmission path;
s3, determining diffraction efficiency T of the grating partition based on preset calculation rules of the coupling-in area, the turning area and the coupling-out area respectively, and further determining duty ratio f, blazed grating width l and blazed grating depth h required for achieving the diffraction efficiency T;
s4, a blazed grating is correspondingly arranged on the grating subarea so as to form a coupling-in grating, a turning grating and a coupling-out grating in the coupling-in area, the turning area and the coupling-out area respectively, so that a diffraction optical waveguide is obtained;
the coupling-in area, the turning area and the coupling-out area all adopt blazed grating structures, the coupling-in grating is arranged on the coupling-in area, and the coupling-in grating is used for coupling light beams into the optical waveguide sheet and transmitting the light beams in the optical waveguide sheet; the turning grating is arranged on the turning region and on one side or two sides of the coupling-in grating along the light beam transmission path, and the turning grating is used for receiving the light beam transmitted by the coupling-in grating and guiding the light beam to the coupling-out region; the coupling-out gratings are arranged on the coupling-out area and on one side of the turning grating along the light beam transmission path, and the coupling-out gratings are used for receiving the light beams transmitted by the turning grating and coupling the light beams out of the light waveguide sheet.
In S1, the beam transmission path needs to satisfy the grating vector closing relationship, that is, grating vectors of the coupling-in region, the turning region and the coupling-out region, so as to form a closed triangle, so that the beams entering the coupling-in region can be coupled out from the coupling-out region at the same angle; specifically, grating vectors of the coupling-in region, the turning region and the coupling-out region sequentially follow a first vector direction, a second vector direction and a third vector direction, and the second vector direction is intersected with the first vector direction and the third vector direction respectively to form an included angle of 30-60 degrees.
In S2, a blazed grating period p=300 to 450nm and a blazed direction are determined according to a grating vector on a beam transmission path, and a blazed angle α=20 to 45° and a blazed angle β=70 to 90 ° are determined according to a diffraction efficiency distribution.
In S3, referring to fig. 4, a fitted curve of diffraction efficiency and duty cycle is established, the diffraction efficiency increases significantly with increasing duty cycle, and this phenomenon is satisfied at different blaze angles. Therefore, the gradual-change blazed grating structure can be applied to the grating structure in the optical waveguide and used for regulating and controlling the diffraction efficiency of different light-emitting positions, so that the uniformity of the overall light-emitting efficiency is realized; based on this, the first and second light sources,
the preset calculation rule of the coupling-in area is that grating parameters of blazed gratings on two adjacent grating partitions are the same and are based on the maximum diffraction efficiency T 1 Determining a duty cycle f 1 Blazed grating width l =100%, a 1 =f 1 *P 1 Blazed grating depth h 1 =l 1 *tanα 1 *tanβ 1 /（tanα 1 +tanβ 1 ）；
The preset calculation rule of the turning area is to control two adjacent gratingsThe duty ratios on the subareas are different, and the energy of the light beam transmitted to the coupling-out area after each total reflection of the light beam in the turning area is approximately equal, so as to determine the diffraction efficiency T 2 =（N 2 -n 2 +1） -1 Duty cycle f 2 =39 to 68%, blazed grating width l 2 =f 2 *P 2 Blazed grating depth h 2 =l 2 *tanα 2 *tanβ 2 /（tanα 2 +tanβ 2 ) =105 to 180nm blazed grating depth h 2 Linearly increasing in the second vector direction to ensure the diffraction efficiency T 2 Linearly increasing from 10 to 50%; wherein N is 2 、n 2 The total diffraction frequency of the light beam in the turning area and the diffraction frequency under the current diffraction efficiency are respectively;
the preset calculation rule of the coupling-out area is that the duty ratios on two adjacent grating subareas are controlled to be different, and the energy of the light beams of the coupling-out optical waveguide is approximately equal after the light beams are totally reflected in the coupling-out area each time, so as to determine the diffraction efficiency T 3 =（N 3 -n 3 +1） -1 Duty cycle f 3 37-65%, blazed grating width l 3 =f 3 *P 3 Blazed grating depth h 3 =l 3 *tanα 3 *tanβ 3 /（tanα 3 +tanβ 3 ) =98 to 172nm blazed grating depth h 2 Linearly increasing in a third vector direction to ensure diffraction efficiency T 3 Linearly increasing from 9 to 38 percent; wherein N is 3 、n 3 The total number of diffraction of the beam in the turning region and the diffraction number at the current diffraction efficiency, respectively.
Example 2: referring to fig. 5, a method for designing a diffractive optical waveguide according to the present invention includes the steps of,
s1, setting a light beam transmission path, and determining a coupling-in area, a turning area and a coupling-out area on a waveguide sheet;
the light beam transmission path is required to meet the grating vector closing relationship, and grating vectors of the coupling-in area, the turning area and the coupling-out area sequentially follow a first vector direction (X), a second vector direction and a third vector direction (Y), wherein the second vector direction is intersected with the first vector direction and the third vector direction respectively to form an included angle of 45 degrees;
s2, dividing grating partitions along a light beam transmission path on a coupling-in region, a turning region and a coupling-out region respectively, and determining a blazed grating period P, a blazed angle alpha and a blazed angle beta required for forming the light beam transmission path;
wherein, the blazed grating period P and the blazed direction are determined according to the grating vector on the beam transmission path, and the blazed angle alpha and the blazed angle beta are determined according to the diffraction efficiency distribution;
for blazed gratings of the coupling-in region, the blazed grating period P is controlled 1 =364 nm, blaze angle α 1 Angle of glint beta = 28% 1 =80°；
For blazed gratings in turning areas, the period P of the blazed gratings is controlled 2 =258 nm, blaze angle α 2 =42°, anti-blaze angle β 2 =89°；
For blazed gratings of the coupling-out region, the blazed grating period P is controlled 3 =364 nm, blaze angle α 3 Angle of glint beta = 36% 3 =85°；
S3, determining diffraction efficiency T of the grating partition based on preset calculation rules of the coupling-in area, the turning area and the coupling-out area respectively, and further determining duty ratio f, blazed grating width l and blazed grating depth h required for achieving the diffraction efficiency T;
in the process of linearly increasing depth, the blazed grating period, the blazed angle and the blazed angle are unchanged, and the duty ratio f of the corresponding grating can be calculated according to triangle similarity rules 2 And blazed grating width l 2 The method comprises the steps of carrying out a first treatment on the surface of the The grating vector of the coupling-out region is along the Y-axis direction, and the blazed grating depth is along the blazed grating with linearly increased Y-direction, and similar to the turning region, the blazed grating period, the blazed angle and the blazed angle are unchanged, and the duty ratio f is equal to that of the turning region 3 And blazed grating width l 3 Triangle similarity relationship is satisfied; for the light incident in the X direction, after being diffracted by the coupling grating, the light propagates along the X direction to reach the turning region; after that, the light is transmitted downwards to the coupling-out area along the Y direction through the diffraction of the turning grating, and the diffraction efficiency is increased along with the increase of the propagation distance due to the gradual change of the blazed grating depth of the turning grating, so that the approaching of the light energy reaching the coupling-out area can be ensured to the greatest extent;finally, the light is diffracted by the coupling-out grating and is emitted again along the Z direction, so that the optical waveguide is coupled out, and as the coupling-out area adopts a grating structure with gradually changed depth, the diffraction efficiency is gradually increased along the positive direction of the Y axis, so that the light energy of the finally coupled-out optical waveguide is ensured to be close;
the preset calculation rule of the coupling-in area is that grating parameters of blazed gratings on two adjacent grating partitions are the same and are based on the maximum diffraction efficiency T 1 =72%, determining the duty cycle f 1 Blazed grating width l =100%, a 1 =f 1 *P 1 Blazed grating depth h=364 nm 1 =l 1 *tanα 1 *tanβ 1 /（tanα 1 +tanβ 1 ）=177nm。
The preset calculation rule of the turning region is to control the different duty ratios of the adjacent two grating partitions, and determine the diffraction efficiency T after the total reflection of the light beam in the turning region each time and the approximate equality of the energy of the light beam transmitted to the coupling-out region 2 =（N 2 -n 2 +1） -1 =25%, 33%, 50%, duty cycle f 2 =39%, 51%, 68%, blazed grating width l 2 =f 2 *P 2 Blazed grating depth h=100 nm, 131nm, 175nm 2 =l 2 *tanα 2 *tanβ 2 /（tanα 2 +tanβ 2 ) =90 nm, 118nm, 158nm; wherein N is 2 、n 2 The total number of diffraction of the beam in the turning region and the diffraction number at the current diffraction efficiency, respectively. In order to show a better uniformity effect, the grating depth of the turning region is linearly increased from 90nm to 158nm;
the preset calculation rule of the coupling-out area is that the duty ratios on two adjacent grating subareas are controlled to be different, and the energy of the light beams of the coupling-out optical waveguide is approximately equal after the light beams are totally reflected in the coupling-out area each time, so as to determine the diffraction efficiency T 3 =（N 3 -n 3 +1） -1 =9%, 18%, 28%, 38%, duty cycle f 3 Blazed grating width l=37%, 46%, 54%, 65 = 3 =f 3 *P 3 Blazed grating depth h=135 nm, 167nm, 197nm, 236nm 3 =l 3 *tanα 3 *tanβ 3 /（tanα 3 +tanβ 3 ) =98 nm, 114nm, 135nm, 171nm; wherein N is 3 、n 3 The total diffraction frequency of the light beam in the turning area and the diffraction frequency under the current diffraction efficiency are respectively; in order to show better uniformity effect, the grating depth of the turning region is linearly increased from 98nm to 171nm;
s4, blazed gratings are correspondingly arranged on the grating subareas so as to form coupling-in gratings, turning gratings and coupling-out gratings in the coupling-in areas, the turning areas and the coupling-out areas respectively, and the diffraction optical waveguide is obtained.
Example 3: referring to fig. 6, a method for designing a diffractive optical waveguide according to the present invention includes the steps of,
s1, setting a light beam transmission path, and determining a coupling-in area, a turning area and a coupling-out area on a waveguide sheet;
the light beam transmission path is required to meet the grating vector closing relationship, and grating vectors of the coupling-in area, the turning area and the coupling-out area sequentially follow a first vector direction (X), a second vector direction and a third vector direction, wherein the second vector direction is intersected with the first vector direction and the third vector direction respectively to form an included angle of 60 degrees;
s2, dividing grating partitions along a light beam transmission path on a coupling-in region, a turning region and a coupling-out region respectively, and determining a blazed grating period P, a blazed angle alpha and a blazed angle beta required for forming the light beam transmission path;
wherein, the blazed grating period P and the blazed direction are determined according to the grating vector on the beam transmission path, and the blazed angle alpha and the blazed angle beta are determined according to the diffraction efficiency distribution;
for blazed gratings of the coupling-in region, the blazed grating period P is controlled 1 =420 nm, blaze angle α 1 =30°, anti-blaze angle β 1 =85°；
For blazed gratings in turning areas, the period P of the blazed gratings is controlled 2 =420 nm, blaze angle α 2 Angle of glint beta =39° 2 =88°；
For blazed gratings of the coupling-out region, the blazed grating period P is controlled 3 =420 nm, blaze angle α 3 Angle of glint beta =39° 3 =88°；
S3, determining diffraction efficiency T of the grating partition based on preset calculation rules of the coupling-in area, the turning area and the coupling-out area respectively, and further determining duty ratio f, blazed grating width l and blazed grating depth h required for achieving the diffraction efficiency T;
the coupling-out path is actually divided into a turning region, an upper coupling-out region and a lower coupling-out region, the coupling-out region is symmetrical about an X axis, the included angle between a grating vector of the turning region and the X direction is 60 degrees, and the included angle between a grating vector of the coupling-out region and the X direction is 120 degrees; in the whole turning region and the coupling-out region, the grating selects blazed gratings with depths linearly increased along the X direction, the blazed grating period, the blazed angle and the anti-blazed angle are unchanged, and the duty ratio f and the grating width l of the corresponding gratings are calculated according to triangle similarity rules;
the preset calculation rule of the coupling-in area is that grating parameters of blazed gratings on two adjacent grating partitions are the same and are based on the maximum diffraction efficiency T 1 =69%, determining the duty cycle f 1 Blazed grating width l =100%, a 1 =f 1 *P 1 Blazed grating depth h=420 nm 1 =l 1 *tanα 1 *tanβ 1 /（tanα 1 +tanβ 1 ）=230nm；
The preset calculation rule of the turning region is to control the different duty ratios of the adjacent two grating partitions, and determine the diffraction efficiency T after the total reflection of the light beam in the turning region each time and the approximate equality of the energy of the light beam transmitted to the coupling-out region 2 =（N 2 -n 2 +1） -1 =9%, 18%, 28%, 38%, duty cycle f 2 32%, 42%, 48%, 56%, blazed grating width l 2 =f 2 *P 2 =134 nm, 176nm, 201nm, 236nm, blazed grating depth h 2 =l 2 *tanα 2 *tanβ 2 /（tanα 2 +tanβ 2 ) =112 nm, 148n, 169nm, 198nm; wherein N is 2 、n 2 The total diffraction frequency of the light beam in the turning area and the diffraction frequency under the current diffraction efficiency are respectively; in order to show better uniformity effect, the grating depth of the turning region is linearly increased from 112-198nm;
the preset calculation rule of the coupling-out region is to control the different duty ratios of the adjacent two grating partitions, and the coupling-out light beams after total reflection in the coupling-out region each timeThe energy of the light beams exiting the optical waveguide is approximately equal, and the diffraction efficiency T is determined 3 =（N 3 -n 3 +1） -1 =9%, 18%, 28%, 38%, duty cycle f 3 32%, 42%, 48%, 56%, blazed grating width l 3 =f 3 *P 3 =134 nm, 176nm, 201nm, 236nm, blazed grating depth h 3 =l 3 *tanα 3 *tanβ 3 /（tanα 3 +tanβ 3 ) =112 nm, 148n, 169nm, 198nm; wherein N is 3 、n 3 The total diffraction frequency of the light beam in the turning area and the diffraction frequency under the current diffraction efficiency are respectively; in order to show better uniformity effect, the grating depth of the turning region is linearly increased from 112-198nm;
s4, blazed gratings are correspondingly arranged on the grating subareas so as to form coupling-in gratings, turning gratings and coupling-out gratings in the coupling-in areas, the turning areas and the coupling-out areas respectively, and the diffraction optical waveguide is obtained.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered by the scope of the claims of the present invention.
Claims (10)
1. A method of designing a diffractive optical waveguide, characterized by: comprises the steps of,
s1, setting a light beam transmission path, and determining a coupling-in area, a turning area and a coupling-out area on a waveguide sheet;
s2, dividing grating partitions along the light beam transmission path on the coupling-in region, the turning region and the coupling-out region respectively, and determining a blazed grating period P, a blazed angle alpha and a blazed angle beta required for forming the light beam transmission path;
s3, determining diffraction efficiency T of the grating partition based on preset calculation rules of the coupling-in area, the turning area and the coupling-out area respectively, and further determining duty ratio f, blazed grating width l and blazed grating depth h required for achieving the diffraction efficiency T;
s4, a blazed grating is correspondingly arranged on the grating subarea so as to form a coupling-in grating, a turning grating and a coupling-out grating in the coupling-in area, the turning area and the coupling-out area respectively, and the diffraction optical waveguide is obtained.
2. A method of designing a diffractive optical waveguide according to claim 1, wherein: in the S1, the beam transmission path needs to satisfy the grating vector closing relationship, that is, the grating vectors of the coupling-in region, the turning region, and the coupling-out region, so as to form a closed triangle, so that the beams entering the coupling-in region can be coupled out from the coupling-out region at the same angle.
3. A method of designing a diffractive optical waveguide according to claim 1, wherein: in S2, the blazed grating period p=300 to 450nm, the blaze angle α=20 to 45°, and the blaze angle β=70 to 90 °.
4. A method of designing a diffractive optical waveguide according to claim 1, wherein: in S2, a blazed grating period P and a blazed direction are determined according to a grating vector on a beam transmission path, and a blazed angle α and a blazed angle β are determined according to a diffraction efficiency distribution; wherein,
for blazed gratings of the coupling-in region, the blazed grating period P is controlled 1 =364 to 420nm, blaze angle α 1 =28 to 30°, glint angle β 1 =80~85°；
For blazed gratings in turning areas, the period P of the blazed gratings is controlled 2 =258 to 420nm, blaze angle α 2 =39 to 42°, glint angle β 2 =88~89°；
For blazed gratings of the coupling-out region, the blazed grating period P is controlled 3 =364 to 420nm, blaze angle α 3 =36 to 39 °, glint angle β 3 =85~88°。
5. A method of designing a diffractive optical waveguide according to claim 1, wherein: in the S3, couple inThe preset calculation rule of the area is that grating parameters of blazed gratings on two adjacent grating areas are the same and are based on the maximum diffraction efficiency T 1 Determining a duty cycle f 1 Blazed grating width l =100%, a 1 =f 1 *P 1 Blazed grating depth h 1 =l 1 *tanα 1 *tanβ 1 /（tanα 1 +tanβ 1 ）。
6. A method of designing a diffractive optical waveguide according to claim 1, wherein: in the step S3, the preset calculation rule of the turning region is to control the duty ratios on two adjacent grating partitions to be different, and the energy of the light beam transmitted to the coupling-out region after the light beam is totally reflected in the turning region each time is approximately equal, so as to determine the diffraction efficiency T 2 =（N 2 -n 2 +1） -1 Duty cycle f 2 =39 to 68%, blazed grating width l 2 =f 2 *P 2 Blazed grating depth h 2 =l 2 *tanα 2 *tanβ 2 /（tanα 2 +tanβ 2 ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein N is 2 、n 2 The total number of diffraction of the beam in the turning region and the diffraction number at the current diffraction efficiency, respectively.
7. A method of designing a diffractive optical waveguide according to claim 1, wherein: for blazed gratings in turning areas, the depth h of the blazed gratings 2 =105 to 180nm blazed grating depth h 2 Increasing in the second vector direction to ensure the diffraction efficiency T 2 Increasing from 10 to 50%.
8. A method of designing a diffractive optical waveguide according to claim 1, wherein: in the step S3, the preset calculation rule of the coupling-out region is to control the duty ratios on two adjacent grating partitions to be different, and determine the diffraction efficiency T after the light beam is totally reflected in the coupling-out region each time and the energy of the light beam coupled out of the optical waveguide is approximately equal 3 =（N 3 -n 3 +1） -1 Duty cycle f 3 37-65%, blazed grating width l 3 =f 3 *P 3 Blazed grating depth h 3 =l 3 *tanα 3 *tanβ 3 /（tanα 3 +tanβ 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein N is 3 、n 3 The total number of diffraction of the beam in the turning region and the diffraction number at the current diffraction efficiency, respectively.
9. A method of designing a diffractive optical waveguide according to claim 1, wherein: for blazed gratings of the coupling-out region, the depth h of the blazed grating 3 =98 to 172nm blazed grating depth h 2 Increasing in the third vector direction to ensure the diffraction efficiency T 3 Increasing from 9 to 38%.
10. A method of designing a diffractive optical waveguide according to claim 1, wherein: in the step S3, the coupling-in grating is disposed on the coupling-in region, and the coupling-in grating is used for coupling the light beam into the optical waveguide sheet and transmitting the light beam in the optical waveguide sheet; the turning grating is arranged on the turning region and on one side or two sides of the coupling-in grating along the light beam transmission path, and the turning grating is used for receiving the light beam transmitted by the coupling-in grating and guiding the light beam to the coupling-out region; the coupling-out gratings are arranged on the coupling-out area and on one side of the turning grating along the light beam transmission path, and the coupling-out gratings are used for receiving the light beams transmitted by the turning grating and coupling the light beams out of the light waveguide sheet.
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