WO2025242019A1 - Manufacturing method for diffractive optical waveguide - Google Patents

Abstract

A manufacturing method for a diffractive optical waveguide. On one hand, a grating material is printed in a structural region of a working template (401) by means of an inkjet printing technique to form an imprint resist layer, pre-curing treatment is performed on the location of a gap of a spliced sub-template (102) corresponding to a polymer resist layer to form a pre-cured resist layer (202) having a specified hardness, and then after a polymer resist material (203) is aligned with the gap, secondary curing is performed to form a patterned structure of an imprinted grating. On the other hand, a patterned transfer structure is formed on a first substrate (101), such that compared with the prior art, the demolding step or process is reduced, or the surface states of a grating structural region and a non-grating structural region on the surface of the substrate are changed, and thus the surface of the grating structural region and the surface of the non-grating structural region have different bonding forces. By means of the method, the imprint quality is improved, the invisibility of the grating is improved, the thicknesses of the overflowed resist and the remaining resist are controlled, the imprint process and the waveguide performance are improved, and the formed waveguide has more excellent optical performance and higher transparency.

Description

A method for fabricating a diffractive optical waveguide Technical Field

This invention relates to the field of optical technology, and in particular to a method for fabricating a diffractive optical waveguide.

Background Technology

Nanoimprint lithography is a micro/nano fabrication technology used to manufacture nanoscale structures. Diffractive waveguides using nanoimprint lithography have become mainstream products in AR optics. In existing technologies, the fabrication process for gratings in diffractive waveguides using current nanoimprint lithography processes is relatively complex. Furthermore, the grating structure is easily affected by the complexity of different processes, leading to lower product performance or yield rates, which in turn affects the optical performance and appearance of the diffractive waveguide – a situation undesirable to those skilled in the art.

Summary of the Invention

This invention provides a method for fabricating a diffractive optical waveguide to improve upon existing nanoimprinting processes. On one hand, inkjet printing technology is used to print grating material into an imprinting adhesive layer in the structural area of a working template. The gaps in the splicing sub-plates corresponding to the polymer adhesive layer are first cured to form a pre-cured adhesive layer with a certain hardness. Then, after the polymer adhesive material aligns with the gaps, a second curing is performed to form a patterned structure of the imprinted grating. On the other hand, by forming a patterned transfer structure on a first substrate, the demolding steps or processes are reduced compared to existing technologies. Alternatively, the surface state of the grating structure area and the non-grating structure area on the substrate surface can be modified through surface modification, resulting in different bonding forces between the grating structure area and the non-grating structure area. These methods improve the imprinting quality, increase the precision and diffraction efficiency of the diffractive grating structure fabrication, enhance the invisibility of the grating, control the thickness of excess and residual adhesive, improve the imprinting process and waveguide performance, and result in a waveguide with superior optical performance and high transparency.

Attached Figure Description

Figures 1 to 16 are schematic diagrams of a method for fabricating a diffractive optical waveguide provided by the present invention.

Detailed Implementation

To address the problems pointed out in the background section of this invention, this invention provides a method for fabricating a diffractive optical waveguide. As shown in Figure 1, the method for fabricating a diffractive optical waveguide includes the following steps:

S1: Provide a working template, which has at least one structured area and an unstructured area.

In step S1, the working template is obtained by flipping the printing master, or the working template is formed by flipping the printing master and splicing the templates together; the working template includes at least one structural region to form a grating structure for a diffractive waveguide.

S2: Based on inkjet printing technology, a predetermined volume of grating material is printed in the structural area of the working template to form a grating material imprinting adhesive layer, thus obtaining a working template with a grating material imprinting adhesive layer.

In step S2, inkjet printing technology is used to print a certain amount of grating material only in the structural area of the working template to form a grating material imprinting adhesive layer. In the non-structural area of the working template, no grating material is printed, so that the grating material imprinting adhesive layer is formed only in the structural area, while the non-structural area is in an empty state without grating material.

Conventional spin-coating and imprinting methods only apply pressure to the grating material in structural areas to form grating structures. Grating material in non-structural areas fails to form the desired grating structure, resulting in over 90% waste of grating material and hindering cost control. This invention, however, prints a specific amount of grating material in designated structural areas of the working template to form an imprinting adhesive layer. Unlike existing spin-coating methods, this invention changes the area and positional relationship of the spin-coating process, allowing for controlled printing of grating material based on structural areas. Non-structural areas are left unprinted, thus saving over 90% of grating material, significantly reducing manufacturing costs and improving economic efficiency.

In this embodiment, the printing position in the working template structure area can be precisely selected, and the volume of grating material printed in each structure area can be precisely controlled, so as to change the existing imprinting method and reduce imprinting costs.

The predetermined volume of grating material described in step S2 is determined based on the volume of grating material filling the grating region and the volume of grating material remaining outside the grating region;

S3: The working template with the grating material imprinting adhesive layer from step S2 is brought into contact with the substrate and imprinted, completely transferring the structure of the working template onto the substrate. In step S3, the working template with the grating material imprinting adhesive layer from step S2 is brought into contact with the substrate, and the imprinting is achieved by aligning the working template with the marks on the substrate according to the pre-set positioning information.

S4: Cure the imprinted adhesive layer in the working template and remove the working template to obtain a diffractive waveguide with a grating structure.

This invention first uses inkjet printing technology to print grating material in the structural area of the working template to form an imprinting adhesive layer. On the one hand, this saves grating material compared to existing technologies. On the other hand, the force applied during inkjet printing allows the grating material to fill each grating structural area as much as possible, especially the roots of different grating teeth, such as the roots of blazed or oblique teeth. This results in more complete filling of the grating material, and during pattern transfer, the shape of the grating structure is transferred more completely. This can prevent the tooth shape defects caused by incomplete filling in existing technologies. The method of this invention can improve this situation.

In step S1, the working template is obtained by copying the printing master. Alternatively, the working template is obtained by copying the printing master and then assembling the templates; more specifically, the working template is obtained through the following process:

S11: Provides an impression master with a preset pattern area;

S12: Obtain intermediate sub-plates by flipping the master plate, and obtain several spliced sub-plates by flipping the intermediate sub-plates again;

S13: The several splicing sub-plates formed in the above steps are spliced on the first base in a preset manner to form a splicing master plate;

S14: Provide a second substrate, uniformly coat a layer of polymer adhesive on one surface of the second substrate, and locally cure the polymer adhesive to form a pre-cured adhesive layer;

S15: Use the splicing master plate in step S13 to imprint the second substrate in step S14, and cure it to obtain the working template.

Those skilled in the art will know that in step S13, when several splicing sub-plates are spliced on the first base in a preset manner, there are certain gaps between adjacent splicing sub-plates. As shown in Figure 2, the splicing master plate includes, for example, 5 splicing sub-plates 102. When the 5 splicing sub-plates 102 are spliced on the first base 101, there are multiple gaps, as shown in region A (of course, the gaps in the figure are only examples and do not represent real gaps). The splicing master plate is formed by multiple splicing sub-plates. There are gaps between adjacent splicing sub-plates, or at the splicing position, whether between adjacent splicing sub-plates or at the splicing position between splicing sub-plates and other areas, there are splicing gaps. Even when splicing sub-plates are formed by high-precision laser cutting and then spliced, there are still gaps. This situation is difficult to avoid.

When a working template is formed by imprinting and casting based on a splicing sub-plate, the cast template is prone to forming protrusions in the area corresponding to the gaps between multiple splicing sub-plates. Therefore, directly using the splicing master plate to obtain a working template with a protruding structure to produce waveguide structures will have an adverse effect on the grating pattern transfer effect on the optical wafer. Therefore, how to improve the quality of grating pattern transfer is an urgent problem that needs to be solved by those skilled in the art.

The present invention, through the design of the pre-cured adhesive layer in step S14, first forms a pre-cured adhesive layer with a certain hardness or high hardness, which can minimize or prevent the formation of protrusions at the gaps when forming the working template using the splicing master plate. In step S14, a second substrate is provided, and a layer of polymer adhesive is uniformly coated on one surface of the second substrate. When the polymer adhesive is locally cured to form a pre-cured adhesive layer, the pre-cured adhesive layer corresponds one-to-one with the gaps of the splicing sub-plates in the splicing master plate formed in step S13.

The width of the pre-cured adhesive layer is defined to be greater than the width of the gap between adjacent splicing sub-panels, or the width of the pre-cured adhesive layer is greater than the gap between adjacent splicing sub-panels and between a splicing sub-panel and other areas; that is, the width of the pre-cured adhesive layer is defined to be greater than or equal to the width of the gap in the splicing master panel. The length of the pre-cured adhesive layer covers the length of the gap in the splicing master panel, such that the length of the pre-cured adhesive layer in different areas covers the length of the gap in each area, or corresponds to the length of the gap in multiple areas, so that the pre-cured adhesive layer can at least completely cover the gap. In some embodiments, the width of the slit between adjacent splicing sub-panels is defined to be 0.5 to 1 mm, and the width of the pre-cured adhesive layer is defined to be 2 to 3 mm.

As shown in Figure 3, a layer of polymer adhesive 203 is first uniformly coated on the surface of the second substrate 201. The polymer adhesive 203 is then locally cured at the locations of the seams of the splicing sub-plates, forming a pre-cured adhesive layer 202 with a certain hardness (as shown in the black area in the figure). The pre-cured adhesive layer divides into several areas, and the gaps between the pre-cured adhesive layer and adjacent splicing sub-plates, as well as between the splicing sub-plates and other areas, completely cover all gaps. This allows the polymer adhesive to be confined within each area defined by the pre-cured adhesive layer during the imprinting process between the second substrate and the first substrate, preventing the polymer adhesive from flowing into different gaps under pressure and preventing the polymer adhesive from overflowing at different locations. The imprinting structure is formed only in the structural area, resulting in a patterned working template without protrusions. This leads to an imprinting working template with a better structure, thereby improving the imprinting quality of the working template.

Furthermore, referring to Figure 4, a curing mask is used to locally cure the polymer adhesive 203 to form a pre-cured adhesive layer 202. The curing mask includes a light-transmitting area 301, and the position of the light-transmitting area on the curing mask corresponds at least one-to-one with the adjacent splicing sub-plates 102 on the splicing master plate and/or the gaps between the splicing sub-plates and other areas. The pre-cured adhesive layer 202 is formed by curing through exposure.

In step S14, a local area of the polymer adhesive 203 is first cured using a curing mask to form a pre-cured adhesive layer 202 with higher hardness. Here, the local area of the polymer adhesive 203 is defined as the gap area between adjacent splicing sub-plates and between the splicing sub-plate and other areas. When the splicing master plate is used to imprint the polymer adhesive 203, the pre-cured adhesive layer 202 area corresponding to the second substrate 201 will not produce a protruding structure due to compression. This solves the problem of unsatisfactory transfer effect and poor transfer quality when using the splicing master plate to transfer grating structures. At the same time, it can also prevent adhesive overflow during the imprinting process and ensure the imprinting quality of the imprinted area.

In step S15, when imprinting the second substrate in step S14 using the splicing master plate, the specific operation is limited as follows: the gap between the adjacent splicing sub-plates of the splicing master plate is aligned with the position of the pre-cured adhesive layer on the second substrate. After all the gaps are aligned, the substrate is cured again and demolded to remove the splicing master plate and obtain the working template.

After the above steps, the obtained working template does not have any protrusions in the gap area of the splicing master. When the working template is used to imprint the diffractive waveguide, the imprinting transfer effect is better, which can improve the optical performance of the waveguide.

In steps S14-S15 of this invention, before the overall curing of the polymer adhesive, the gaps between the splicing sub-plates corresponding to the polymer adhesive and between the splicing sub-plates and other areas are first cured to form a pre-cured adhesive layer with a certain hardness. After the polymer adhesive is aligned with the gaps, a second curing is performed to form the patterned structure of the embossed grating. That is, different curing layers are formed by curing twice, which is different from the single curing in the prior art. For the existing embossing process, this can greatly improve the embossing process and waveguide performance, and the resulting diffractive waveguide has better optical performance.

In some embodiments, in step S2: a predetermined volume of grating material is printed in the structural area of the working template based on inkjet printing technology to form a grating material imprinting adhesive layer; it is known that the structure based on the diffractive waveguide includes a coupling-in region, a coupling-out region, or in some embodiments, a transition region.

To address the issues of ink overflow and uniformity of residual ink thickness mentioned in the background section of this invention, this invention uses different grating structures to define predetermined volumes of grating material for printing in different structural regions of the working template. This allows for precise control of the volume of printed grating material in different regions, thereby controlling ink overflow and residual ink thickness. The predetermined volume of grating material is determined based on the volume of grating material filling the grating region and the volume of grating material remaining outside the grating region. More specifically, the inkjet-printed grating materials in multiple different structural regions are defined to satisfy the following relationship:

The predetermined volume of grating material for each structural region is equal to the sum of the volume of the reference grating material and the volume of the residual grating material; the calculation formulas for different structural regions are as follows:

The grating material V _{_coupled} of the predetermined volume of the coupling region = + (1); In equation (1), f represents the duty cycle of the coupled grating structure, h represents the height of the coupled grating structure, d represents the diameter of the coupled region, x represents the inward distance of the grating material in the coupled region, and t represents the thickness of the residual adhesive in the coupled region; the predetermined volume of the grating material in the transition region V _{_turn} = + (2); In equation (2), F1 represents the duty cycle of the grating structure in the transition region, H1 represents the height of the grating structure in the transition region, W1 represents the width of the transition region, Y1 represents the inward distance of the grating material in the transition region, L1 represents the length of the transition region, and T1 represents the thickness of the residual adhesive in the transition region. The grating material _{V_out} of the predetermined volume of the coupling region = + (3); In equation (3), F2 represents the duty cycle of the grating structure in the coupling region, H2 represents the height of the grating structure in the coupling region, W2 represents the width of the coupling region, Y2 represents the distance of the grating material in the coupling region shrinkage, L2 represents the length of the coupling region, and T2 represents the thickness of the residual adhesive in the coupling region.

For further detailed explanation, Figure 7 shows a top view of the coupling region, transition region, and coupling out region. In the figure, A represents the top view of the coupling region, d represents the diameter of the coupling region (i.e., the size of the coupling grating area to be formed after inkjet printing and imprinting), the gray area represents the grating material area printed by inkjet printing in the coupling region, and x represents the inward shrinkage distance of the grating material in the coupling region (i.e., the distance between the formed coupling grating structure area and the inkjet-printed grating material). Figures B and C in Figure 7 show top views of the transition region and the coupling out region. W1 represents the width of the transition region, L1 represents the length of the transition region, Y1 represents the inward shrinkage distance of the grating material in the transition region, W2 represents the width of the coupling out region, L2 represents the length of the coupling out region, and Y2 represents the inward shrinkage distance of the grating material in the transition region. It can be seen that W1, W2, L1, and L2 can vary in the transition region or the coupling out region, and even Y1 and Y2 vary in different regions, defining different predetermined volumes based on different inward shrinkage distances. Based on the design, W1, W2, L1, and L2 of different regions are determined according to the grayscale color map during inkjet printing. Of course, whether W1, W2, L1, and L2 shown in the figure change depends on the design. The figure is only an example and does not limit the trend of W1, W2, L1, and L2.

Based on the same understanding, H1 in formula (2) and H2 in formula (3) represent the height of the grating structure in the transition region or the coupling region, respectively. Based on the consideration of the transition and coupling efficiency, their values can vary, such as gradually increasing. The values of H1 and H2 are different in different positions. Therefore, the amount of grating material used in inkjet printing in different regions can be determined based on the grayscale color map during inkjet printing to determine H1 and H2 in different regions. The volume of grating material in inkjet printing is different in different regions, showing a certain regular change.

By limiting the volume of grating material printed in different areas, it is mainly divided into two parts. The first part is the reference grating material volume, which is used to determine the required amount of grating material based on grating parameters such as grating structure, duty cycle, period, and height in different areas. The second part is the residual grating material volume, which is based on the amount of glue overflow during printing and the requirements for residual grating material during printing. The amount of glue overflow outside the grating structure area is controlled by precise calculation. By calculating the reference grating material volume within the grating structure area and the residual grating material volume outside the grating structure area in detail and accurately, glue overflow control and grating structure conformation are achieved.

The reference grating material volume within the grating structure region referred to in this invention refers to the volume of grating material required to completely fill the grating structure region from the bottom to the end; the residual grating material volume refers to the volume of the residual layer formed outside the grating structure region.

Referring to Figure 5, the working template 401 obtained through the aforementioned embodiments shows a working template 401 including two structures. It is assumed that the formed working template includes, for example, a blazed grating structure region 4011, a straight tooth grating structure region 4012, and a helical tooth grating structure region 4013.

Figure 6 is a partial enlarged view of the blazed grating structure region 4011 in the working template 401 of the two structures, defining the grating region 40112 and the non-grating region 40111. Of course, the same grating region and non-grating region also exist for the straight tooth grating structure region 4012 and the oblique tooth grating structure region 4013. Furthermore, the grating region 40112 refers to the region formed from the bottom to the top of the grating where the grating is located. The grating material fills the space region where the grating is located defined from the bottom to the top of the grating structure. The defined reference grating material volume refers to the volume of grating material required to completely fill the space region from the bottom to the top of the grating structure within the grating region. The region outside the grating region 40112 in the figure is defined as the non-grating region, which is equivalent to the area outside the grating region. The residual grating material volume refers to the volume of the residual layer formed outside the grating region. Of course, different combinations of grating structures can be included in the same structural area, such as blazed and straight teeth, straight teeth and helical teeth, etc. The attached drawings are not intended to limit the combination of multiple grating structures based on different grating designs.

As mentioned earlier, the volume of grating material in each structural region = the volume of reference grating material + the volume of residual grating material. Further explanation is provided in conjunction with Figures 5 and 6. The non-grating region 40111 in the figures shows a cross-sectional view of the shape of the residual grating material after imprinting. An imprinting structure (not shown in the figure) is formed on the substrate using the working template provided by this invention, forming an imprinting structure including the residual grating material. That is, the grating material within the thick black frame is defined as the residual adhesive volume, i.e., the volume of grating material exposed outside the structural region. For example, the residual adhesive volume coupled into the grating region is defined as... For example, the volume of the residual grating material in the transition region is limited to The volume of residual grating material in the coupled grating region is limited to The physical meanings of the physical quantities in the formula are the same as those described above. The grating material in the area covered by the thick black outline is defined as the reference grating material volume, that is, the volume of grating material required to fill the area from the bottom to the end of the grating structure. In this application, if the reference grating material volume of the coupling region is defined as... The volume of the reference grating material in the transition region is limited to The volume of the reference grating material in the coupled grating region is limited to The physical meanings of each physical quantity in the formula are the same as those described above. Therefore, by defining the volume of the reference grating material and the volume of the residual grating material, the volume of the reference grating material can be accurately calculated to ensure that the grating material completely fills all areas of the grating structure, especially the root positions of the blazed and helical tooth structures. The calculated volume of the residual grating material can be precisely controlled to control the volume of the grating material exposed outside the structural area. During imprinting, based on the known volume of the grating material exposed outside the structural area, the thickness of the residual grating material after imprinting can be controlled by controlling the imprinting force. Controlling the volume to control the overflow of adhesive and the thickness of the residual adhesive layer after imprinting is beneficial to those skilled in the art.

This invention utilizes the force applied during inkjet printing to ensure that the grating material fills each grating structure area as much as possible, especially the roots of different grating teeth, such as the roots of blazing or oblique teeth. This results in more complete filling of the grating material and a more complete transfer of the grating structure shape during pattern transfer, preventing the tooth shape defects caused by incomplete filling that exist in existing technologies.

Meanwhile, in forming the working template, before the overall curing of the polymer adhesive, the gaps in the splicing sub-templates corresponding to the polymer adhesive layer are first cured to form a pre-cured adhesive layer with a certain hardness. After the polymer adhesive is aligned with the gaps, a second curing is performed to form the patterned structure of the embossed grating. That is, different curing layers are formed in two separate curing processes, which is different from the single curing in the prior art. This can significantly improve the embossing process and waveguide performance, and the resulting diffractive waveguide has superior optical performance. Based on the grating structure parameters, the volume of the printed grating material in the coupled grating region, the turning point, or the coupled grating region can be calculated separately. The printing volume can be precisely controlled at the picoliter level. Thus, by precisely controlling the volume of the printed grating material in different regions, the overflow and residual adhesive thickness can be controlled, resulting in unexpected technical effects.

In another embodiment, a method for fabricating a diffraction grating is provided, as shown in Figures 8-13, comprising the following steps:

(1) Provide a first substrate and perform surface treatment on any one surface of the first substrate; the surface treatment includes at least a surface adhesion enhancement treatment;

(2) Provide an imprinting master, which has a graphical structure to be transferred;

(3) A first imprinting adhesive layer is uniformly formed on one side surface of the imprinting master with a graphic structure;

(4) Based on the surface that has been surface treated in step (1), imprint the first imprinting adhesive layer in step (3) to form a first imprinting composite layer; and remove the imprinting master in the first imprinting composite layer to obtain a second substrate with a transfer patterned structure.

(5) Perform surface treatment on the surface of the second substrate with the transfer patterned structure;

(6) The diffraction grating is formed based on the second substrate that has been surface-treated in step (5).

In step (2), an imprint master 30 is provided, which has multiple graphic structures to be transferred, as shown in Figure 8.

In step (3), a first imprinting adhesive layer 40 is uniformly formed on the side surface of the imprinting master 30 with the graphic structure; a layer of the first imprinting adhesive layer 40 is uniformly coated on the side surface of the imprinting master with the graphic structure; and the thickness of the first imprinting adhesive layer 40 is greater than the maximum height of the graphic structure, so as to achieve uniform coating of the first imprinting adhesive layer 40 on the entire surface of the imprinting master.

In step (4), the first imprinted adhesive layer 40 in step (3) is imprinted on the surface 20 that has been surface-treated in step (1) to form the first imprinted composite layer S1.

Based on the aforementioned steps, the imprint master 30 in the first imprint composite layer S1 is removed to obtain a second substrate S2 with a transfer patterned structure; the second substrate S2 has an optical structure unit complementary to the imprint master 30, namely the transfer patterned structure; as shown in Figure 8, a grating unit complementary to the imprint master 30 is shown on the second substrate S2, which is transferred through the imprint master to form the patterned structure.

It also includes step (5), which involves surface treatment of the surface of the second substrate S2 with the transfer patterned structure to obtain the surface structure 50 after surface treatment. The surface treatment method used is the same as that in step (1), including adhesive treatment or plasma treatment processes.

In step (6), a diffraction grating is formed based on the second substrate that has been surface-treated in step (5). Specifically, two different embodiments are included. As shown in FIG9, the formation of a diffraction grating based on the second substrate that has been surface-treated in step (5) includes step (61), depositing a second material on the second substrate that has been surface-treated in step (5) to form a second material layer 90, the refractive index of the second material layer 90 being greater than that of the first imprinted adhesive layer 40; step (62), providing a first substrate 70, and uniformly forming a third material layer 100 on any surface of the first substrate 70; bonding the third material layer 100 to a surface of the second material layer 90 facing away from the patterned structure to form a diffraction waveguide; when the diffraction waveguide is in operation, light is transmitted by total internal reflection within the first substrate.

In this embodiment, the third material layer 100 has an adhesive function, which enables the first substrate 70 to bond better with the second material layer 90, especially by improving the bonding force of the two bonding surfaces through adhesive treatment.

In this embodiment, a second material layer 90 is formed by depositing a second material on the second substrate, wherein the refractive index of the second material is greater than 1.7. The refractive index of the second material layer 90 is greater than the refractive index of the first imprinted adhesive layer 40, in order to meet the optical performance requirements of the diffractive waveguide.

In this embodiment, after surface treatment of the first substrate, it is imprinted onto an imprinting master with a structured imprinting adhesive, and the structured imprinting adhesive layer is transferred onto the first substrate to form a second substrate. Then, a second material layer (grating material layer) is further formed on the structured imprinting adhesive layer to obtain a diffraction grating. Finally, a third material is used to bond the diffraction grating to the first substrate to form a diffraction waveguide. At this point, the second substrate (the first substrate and the structured imprinting adhesive layer) does not need to be separated from the diffraction grating. The first substrate can be used as a protective cover, and the structured imprinting adhesive layer serves to connect the diffraction grating and the first substrate, while also protecting the diffraction grating structure from damage. This method is simpler and more effective than existing imprinting methods for preparing diffraction gratings.

In another embodiment, in step (6), the diffraction grating is formed based on the second substrate that has been surface-treated in step (5). The method further includes the steps of: (7) providing a first substrate and uniformly forming a second imprinting adhesive layer on any surface of the first substrate; (8) imprinting the second imprinting adhesive layer from step (7) onto the second substrate with the transfer patterned structure that has been surface-treated in step (5), forming a diffraction grating within the second imprinting adhesive layer to obtain a diffraction waveguide with a diffraction grating; when the diffraction waveguide is in operation, light is transmitted via total internal reflection within the first substrate.

In detail, as shown in Figure 10, in step (7), a first substrate 70 is provided, and a second imprinting adhesive layer 80 is uniformly formed on any surface of the first substrate 70; wherein the thickness of the second imprinting adhesive layer 80 is greater than the highest height of the patterned structure, so that the entire surface of the first substrate 70 is coated with a layer of the second imprinting adhesive layer 80. The refractive index of the second imprinting adhesive layer 80 is in the range of 1.8 to 2.3, and it must also satisfy that the refractive index of the second imprinting adhesive layer 80 is greater than that of the first imprinting adhesive layer 40. The refractive index of the first substrate 70 is in the range of 1.8 to 2.2, and its value should be as close as possible to that of the second imprinting adhesive layer 80.

As shown in Figure 11, the process also includes step (8), where the second imprinting adhesive layer 80 from step (7) is imprinted onto the second substrate S2 with the transfer patterned structure that has been surface-treated in step (5), resulting in the imprinted second imprinted composite layer S3, as shown in Figure 12; a diffraction grating is formed within the second imprinting adhesive layer to obtain a diffraction waveguide with a diffraction grating; when the diffraction waveguide is in operation, light is transmitted through total internal reflection within the first substrate. As shown in Figure 12, the second imprinting adhesive layer 80 is imprinted onto the second substrate S2 formed in step (4).

Through the above steps (1) to (8), a second imprinted composite layer S3 with a superimposed structure is obtained, and a diffraction grating structure is formed, resulting in a diffraction waveguide with a diffraction grating structure. When the diffraction waveguide is working, the light is transmitted by total internal reflection within the first substrate, as shown in Figure 12. The diffraction grating is obtained through this process, forming the diffraction grating with the required patterned structure.

Compared to existing technologies, this embodiment only involves a demolding operation in step (4) when removing the imprinting master from the first imprinting composite layer, reducing the number of demolding steps or processes. This invention can form the required diffraction grating with a single demolding and imprinting process, avoiding damage to the grating structure caused by multiple demolding operations in existing technologies. The fewer demolding processes of this invention can better ensure the integrity of the grating structure.

On the other hand, the present invention, through the lamination process in step (8), eliminates the need for further lamination of the final diffractive waveguide product, and also eliminates the need for multiple cleaning operations as in the prior art, making the preparation process simpler and more efficient. By setting an imprinting adhesive layer on the surface of the imprinting master 30 and the first substrate 70, which includes two homogenization operations, the present invention requires fewer homogenization operations compared to the prior art. At the same time, the imprinting pattern area formed by the first imprinting adhesive layer 40 with a lower refractive index is used to imprint the second imprinting adhesive layer 80 with a higher refractive index to form a diffraction grating with the required refractive index. In this process, the first imprinting adhesive layer 40 with a lower refractive index can completely fill the diffraction grating structure, or the second material layer 90 can completely fill the structural area in the first imprinting adhesive layer 40 without demolding. That is, the first imprinting adhesive layer can play a role in full bonding, which can achieve the technical effect of full bonding of the diffractive waveguide, resulting in higher transparency and grating invisibility.

As shown in Figure 13, after undergoing the same process as in the aforementioned embodiments, a region comprising three different grating structures is obtained, and a region further comprising at least three different grating structures. This embodiment provides a diffractive waveguide comprising a first substrate, a second imprinted adhesive layer, a first imprinted adhesive layer, and a first substrate stacked sequentially; the first imprinted adhesive layer has a patterned structure, and the patterned structure forms a complementary patterned structure in the second imprinted adhesive layer, and the refractive index of the first imprinted adhesive layer is less than that of the second imprinted adhesive layer; the projected area of the first imprinted adhesive layer on the first substrate is not less than the projected area of the second imprinted adhesive layer on the first substrate; when the diffractive waveguide is in operation, light is transmitted by total internal reflection within the first substrate.

The present invention also provides a diffractive waveguide, the diffractive waveguide comprising a first substrate, a first imprinted adhesive layer, and a first substrate stacked sequentially, and further comprising a second imprinted adhesive layer or a second material layer; the first imprinted adhesive layer has a patterned structure, and the patterned structure forms a complementary patterned structure in the second imprinted adhesive layer or the second material layer, and the refractive index of the first imprinted adhesive layer is less than the refractive index of the second imprinted adhesive layer or the second material layer; the projected area of the first imprinted adhesive layer on the first substrate is not less than the projected area of the second imprinted adhesive layer or the second material layer on the first substrate; when the diffractive waveguide is in operation, light is transmitted by total internal reflection within the first substrate.

Furthermore, the present invention provides a grating fabrication method based on surface modification selective imprinting. The surface modification defined in the present invention refers to surface treatment of a local surface region of a diffractive waveguide substrate to improve its surface contact angle, thereby achieving the purpose of the present invention.

A selective imprinting method based on surface modification, as shown in Figures 14-1 and 14-2, includes:

Step (1): Provide a substrate 100, deposit a first barrier layer 200 on any surface of the substrate 100, the first barrier layer 200 having at least one window region, at least one patterned region being adapted to the shape and position corresponding to the grating structure region; the substrate having a grating structure region and a non-grating structure region.

In step (1), the substrate 100 can be a silicon substrate, a glass substrate, a germanium substrate, a gallium arsenide, a SiC, a _TiO2 , or a flexible substrate such as a resin polymer; the first barrier layer 200 has at least one window region A, as shown in Figure 14-1; of course, the first barrier layer can be defined to include two window regions, wherein each window region corresponds to the coupling-in region and the coupling-out region of the diffracted optical waveguide, or may also include a turning region, etc.

Furthermore, multiple window areas of the first barrier layer correspond to the grating structure areas, and their shapes and positions are adapted to each other; that is, the shape of each window area matches the shape of the corresponding grating structure area to enable subsequent process operations.

In step (1), the purpose of setting the first barrier layer is to prevent the contact between the adhesive layer and the local surface of the substrate when the adhesive layer 300 is set in the subsequent steps, thereby reducing the contact force and the contact area between the two. The thickness of the first barrier layer is no more than 100 μm, such as 10~50 μm, 50~80 μm, or 80~100 μm.

Step (2) Spin-coat an adhesive material onto at least the surface of the window area of the first barrier layer to form a uniform adhesive layer 300; the thickness of the adhesive layer is not greater than 20 nm. As shown in Figure 14-1, spin-coat an adhesive material onto at least a few window areas of the first barrier layer, including spin-coating an adhesive material, such as an adhesive adhesive, onto the surface of the first barrier layer and the surfaces of a few window areas, and uniformly coat the adhesive to form a uniform adhesive layer. The function of the adhesive layer is to improve the adhesion of the substrate surface, improve the bonding force between the high-bending-pressure printing adhesive and the substrate, ensure that the high-bending-pressure printing adhesive is not peeled off by the subsequent process, and improve the force during bonding.

Step (3): Remove the first barrier layer by physical peeling, so that the substrate surface under the first barrier layer is completely exposed. In this step, the barrier layer is removed by physical peeling to provide process surface space for the subsequent process of adding the anti-stick layer 500, while removing excess adhesive layer.

Step (4): A second barrier layer 400 is deposited on the surface of the adhesion-enhancing layer 300. The material of the second barrier layer is different from that of the first barrier layer. The thickness of the second barrier layer is no greater than 30 μm. Due to the presence of the adhesion-enhancing layer on the substrate surface, the second barrier layer will preferentially be deposited in the adhesion-enhancing layer region, forming a second barrier layer. Other regions will not have a second barrier layer deposited because there is no adhesion-enhancing layer. The thickness of the second barrier layer is no greater than 30 μm. Of course, if the second barrier layer 400 is deposited in a non-grating structure region, it can also be removed by conventional physical methods. In step (4), the function of the second barrier layer is to protect the adhesion-enhancing layer to prevent it from being affected and failing. The material of the second barrier layer is different from that of the first barrier layer.

Step (5): Deposit an anti-adhesion layer 500 on the entire substrate surface from step (4); the thickness of the anti-adhesion layer is no greater than 15 nm. An anti-adhesion layer with a thickness of no greater than 15 nm is deposited on the entire substrate surface after step (4) by physical vapor deposition. The purpose is to reduce the adhesion of the exposed surface area of the substrate, i.e., to reduce the adhesion of the non-grating structure area, increase the surface contact angle of the non-grating structure area, reduce the bonding force between the high-reflection adhesive in this area and the substrate surface, and ensure that the high-reflection adhesive can be peeled off by the subsequent process to achieve surface treatment of the non-grating structure area of the substrate. The surface contact angle of the anti-adhesion layer is no less than 109°. This ensures that the surface of the anti-adhesion layer has good hydrophobicity, making it less likely for liquids or impurities to deposit on the surface, thus better protecting the cleanliness of the substrate surface.

Step (6): Remove the second barrier layer 400 to fully expose the tackifying layer on the substrate surface. In this step, the purpose of removing the second barrier layer is to fully expose the tackifying layer on the substrate surface so that the high-bending-pressure adhesive can make full contact with the tackifying layer as much as possible in the subsequent process, thereby enhancing the bonding force between the high-bending-pressure adhesive and the substrate and improving the bonding strength.

Step (7): Spin-coat a high-refractive-index embossing adhesive onto the entire surface of the substrate. The thickness of the high-refractive-index embossing adhesive meets the imprinting requirements of the preset diffraction grating. Then, perform the imprinting process. In this step, based on the existing spin-coating process, spin-coat a layer of high-refractive-index embossing adhesive 600 onto the surface of the substrate to form a high-refractive-index embossing adhesive layer 600 for the diffraction grating, and then perform the imprinting process to form the diffraction grating.

Step (8): After curing, the high-refractive-index printing adhesive is peeled off by physical demolding, so that at least the substrate surface between the grating structure areas is exposed, resulting in an imprinted product, as shown in Figure 14-2. In this step, after the high-refractive-index printing adhesive has cured, the high-refractive-index printing adhesive in the non-grating structure areas is peeled off by physical demolding, such as manual demolding or mechanical demolding, so that the imprinted diffraction grating structure in the grating structure area remains on the substrate surface through the action of the adhesive layer, as shown in Figure 14-2. By setting a thin film on the surface of the high-refractive-index printing adhesive and peeling off the film, the high-refractive-index printing adhesive in the non-grating structure areas with poor adhesion to the substrate surface is peeled off, while the diffraction grating structure in the grating structure area is unaffected due to the strong bonding force of the adhesive layer and remains on the adhesive layer of the substrate, thus obtaining the imprinted diffraction grating product. Of course, based on the bonding strength of the anti-adhesive layer, it also includes peeling off the anti-adhesive layer in the non-grating structure area when peeling off the high-folding pressure printing adhesive, so that only the grating structure is retained in the grating structure area, while the other structure areas expose the substrate surface, as shown in Figure 15, which is also within the scope of protection claimed in this application.

Referring to Figure 16, compared with the prior art, Figure 16(1) shows a diffractive waveguide with an imprinted grating structure in the prior art. After the surface modification imprinting process of the present invention, the imprinted structure shown in Figure 16(2) and (3) can be formed. In step (8), the high-refractive-index imprinting adhesive is peeled off by physical demolding so that at least the substrate surface between the grating structure regions is exposed. This includes the embodiment shown in Figure 16(2), that is, only the substrate surface between the grating structure regions is exposed; it also includes the embodiment shown in Figure 16(3), that is, all substrate surfaces other than the grating structure regions are exposed, that is, only the grating structure is retained in the grating structure region, while the substrate surface is exposed in other structure regions. Such a structure is beneficial to improving the imaging effect of the waveguide.

In this embodiment, by repeatedly depositing a first barrier layer, a second barrier layer, an anti-sticking layer, and an adhesion-enhancing layer, the surface state of the grating structure region and the non-grating structure region on the substrate surface is changed, resulting in different bonding forces between the surfaces of the grating structure region and the non-grating structure region. This achieves surface modification of the grating structure region and the non-grating structure region, thereby allowing the imprinting adhesive layer with different surface bonding force states to be peeled off or retained, improving the overall imprinting quality of the imprinted product. It enables the peeling off of high-refractive-index imprinting adhesive in the non-grating structure region. Through the process of this embodiment, on the one hand, the surface parallelism of the imprinted product in the non-grating structure region can be maintained; on the other hand, it avoids problems such as environmental particle adsorption, internal adhesive contamination, and scratches during micro-nano processing, thus protecting the integrity of the substrate surface as much as possible.

Furthermore, in some other embodiments, step (8) also includes peeling off the anti-adhesive layer in the non-grating structure area while peeling off the high-folding embossing adhesive, as shown in FIG16, so that the embossing structure is retained only in the grating structure area, while the anti-adhesive layer in the non-grating structure area is peeled off, forming a diffractive waveguide with different structures, as shown in (2) and (3) in FIG16. Thus, two different substrate product categories can be obtained according to the requirements of the actual product. All of these are within the technical scope of the present invention.

The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims (20)

A method for fabricating a diffractive optical waveguide, characterized by comprising the following steps: S1: Provide a working template, the working template having at least one structured region and an unstructured region; S2: Based on inkjet printing technology, a predetermined volume of grating material is printed in at least one of the structural regions of the working template, and no grating material is printed in the non-structural regions, forming a grating material imprinting adhesive layer, thereby obtaining the working template having the grating material imprinting adhesive layer; the predetermined volume of grating material is determined based on the volume of grating material filling the grating region and the volume of grating material remaining outside the grating region; S3: The working template with the grating material imprinting adhesive layer from step S2 is brought into contact with the substrate and imprinted to completely transfer the structure of the working template onto the substrate; S4: Cure the imprinting adhesive layer in the working template and remove the working template to obtain the diffractive waveguide with a grating structure. A method for fabricating a diffractive waveguide according to claim 1, characterized in that, in step S2, a predetermined volume of grating material is printed in at least one structural region of the working template, wherein the predetermined volume of grating material printed in each structural region is equal to the sum of the volume of a reference grating material and the volume of a residual grating material; the volume of the reference grating material is defined as the volume of grating material filling the grating region; and the volume of the residual grating material is defined as the volume of the residual layer formed outside the grating region. According to claim 2, the fabrication method of a diffractive optical waveguide is characterized in that the volume of the reference grating material in the coupling region within the structural region is limited to [missing information]. The volume of the residual grating material within the coupling region is defined as follows: The volume of the reference grating material in the transition region within the structural region is limited to [a certain value]. The volume of the reference grating material in the coupled region within the structural region is defined as follows: The volume of the residual grating material within the transition region is limited to The volume of the residual grating material within the coupling region is defined as follows: ; In the formula, f represents the duty cycle of the coupled grating structure, h represents the height of the coupled grating structure, d represents the diameter of the coupled region, x represents the inward shrinkage distance of the grating material in the coupled region, and t represents the thickness of the residual adhesive in the coupled region; F1 represents the duty cycle of the grating structure in the transition region, H1 represents the height of the grating structure in the transition region, W1 represents the width of the transition region, Y1 represents the inward shrinkage distance of the grating material in the transition region, L1 represents the length of the transition region, and T1 represents the thickness of the residual adhesive in the transition region; F2 represents the duty cycle of the grating structure in the coupled region, H2 represents the height of the grating structure in the coupled region, W2 represents the width of the coupled region, Y2 represents the inward shrinkage distance of the grating material in the coupled region, L2 represents the length of the coupled region, and T2 represents the thickness of the residual adhesive in the coupled region. A method for fabricating a diffractive optical waveguide according to claim 1 or 2, characterized in that the working template is obtained through the following steps: S11: Provides an impression master with a preset pattern area; S12: Obtain intermediate sub-plates by flipping the master plate, and obtain several spliced sub-plates by flipping the intermediate sub-plates again; S13: The several splicing sub-plates formed in the above steps are spliced on the first base in a preset manner to form a splicing master plate; S14: Provide a second substrate, uniformly coat a layer of polymer adhesive on one surface of the second substrate, and locally cure the polymer adhesive to form a pre-cured adhesive layer; S15: Use the splicing master plate in step S13 to imprint the second substrate in step S14, and cure it to obtain the working template. According to claim 4, the method for manufacturing a diffractive waveguide is characterized in that the pre-cured adhesive layer formed in step S14 corresponds one-to-one with the gaps in the splicing master plate formed in step S13, and the gaps include the gaps between several splicing sub-plates and the gaps between the splicing sub-plates and other areas. According to claim 5, the method for manufacturing a diffractive optical waveguide is characterized in that the width of the pre-cured adhesive layer is greater than or equal to the width of the gap in the splicing master plate; and the length of the pre-cured adhesive layer at least completely covers the length of the gap in the splicing master plate. A method for fabricating a diffractive waveguide according to claim 5 or 6, characterized in that a curing mask is used to locally cure the polymer adhesive material in step S14, wherein the curing mask includes a light-transmitting area, and the position of the light-transmitting area on the curing mask corresponds one-to-one with the gap in the splicing master plate. A method for fabricating a diffraction grating, characterized by comprising the following steps: (1) Provide a first substrate and perform surface treatment on any one surface of the first substrate; (2) Provide an imprinting master, the imprinting master having a graphical structure to be transferred; (3) A first embossing adhesive layer is uniformly formed on one side surface of the embossing master plate with a graphic structure; (4) Based on the surface that has been surface-treated in step (1), imprint the first imprinting adhesive layer in step (3) to form a first imprinting composite layer; and remove the imprinting master in the first imprinting composite layer to obtain a second substrate with a transfer patterned structure; (5) Perform surface treatment on the surface of the second substrate having a transfer patterned structure; (6) The diffraction grating is formed based on the second substrate that has been surface-treated in step (5). According to claim 8, a method for fabricating a diffraction grating is characterized in that, in step (6), in detail, a second material is deposited on the second substrate to form a second material layer to form the diffraction grating, based on the second substrate that has been surface-treated in step (5). According to claim 9, a method for fabricating a diffraction grating is characterized in that, in step (6), a first substrate is provided, and a third material layer is uniformly formed on any surface of the first substrate; the third material layer is bonded to a surface of the second material layer opposite to the patterned structure to form a diffraction waveguide; when the diffraction waveguide is in operation, the light is transmitted by total internal reflection within the first substrate. According to claim 8, a method for fabricating a diffraction grating is characterized in that step (6) specifically includes providing a first substrate and uniformly forming a second imprinting adhesive layer on any surface of the first substrate; imprinting the second imprinting adhesive layer based on the second substrate with a transfer patterned structure that has been surface-treated in step (5), forming the diffraction grating within the second imprinting adhesive layer, and obtaining a diffraction waveguide with the diffraction grating; when the diffraction waveguide is in operation, light is transmitted by total internal reflection within the first substrate. According to claim 11, the method for fabricating a diffraction grating is characterized in that the refractive index of the second imprinting adhesive layer is greater than the refractive index of the first imprinting adhesive layer; the refractive index of the second imprinting adhesive layer is in the range of 1.8 to 2.3. According to claim 10, the method for fabricating a diffraction grating is characterized in that the refractive index of the second material layer is greater than the refractive index of the first imprinting adhesive layer; the refractive index of the second material layer is greater than 1.7. A method for fabricating a diffraction grating according to claim 11, characterized in that the diffraction waveguide comprises a first substrate, a first imprinted adhesive layer, and a first base layer sequentially stacked, and further comprises a second imprinted adhesive layer or a second material layer; the first imprinted adhesive layer has a patterned structure, and the patterned structure forms a complementary patterned structure in the second imprinted adhesive layer or the second material layer, and the refractive index of the first imprinted adhesive layer is less than the refractive index of the second imprinted adhesive layer or the second material layer; the projected area of the first imprinted adhesive layer on the first substrate is not less than the projected area of the second imprinted adhesive layer or the second material layer on the first substrate; when the diffraction waveguide is in operation, light is transmitted by total internal reflection within the first substrate. A method for fabricating a diffraction grating, characterized by comprising the following steps: Step (1): Provide a substrate having a grating structure region and a non-grating structure region, deposit a first barrier layer on any surface of the substrate, the first barrier layer having at least one window region, at least one of the window regions being adapted to the shape and position corresponding to the grating structure region; Step (2): Spin-coat the adhesive material onto at least the surface of the window area of the first barrier layer to form a uniform adhesive layer; Step (3): Remove the first barrier layer by physical peeling to fully expose the substrate surface beneath the first barrier layer; Step (4): Deposit a second barrier layer on the surface of the adhesive layer, the second barrier layer being made of a different material than the first barrier layer; Step (5): Deposit an anti-adhesion layer on the entire substrate surface as in step (4); Step (6): Remove the second barrier layer so that the adhesive layer on the substrate surface is fully exposed; Step (7): Spin-coat a high-refractive-index embossing adhesive onto the entire surface of the substrate, wherein the thickness of the high-refractive-index embossing adhesive meets the imprinting requirements of the preset diffraction grating; and perform the imprinting process. Step (8): After curing, the high-folding embossing adhesive is peeled off by physical demolding so that the surface of the substrate between at least the grating structure regions is exposed, and an embossed product is obtained. According to claim 15, the method for fabricating a diffraction grating is characterized in that the thickness of the first blocking layer is not greater than 100 μm, the thickness of the adhesive layer is not greater than 20 nm, the thickness of the second blocking layer is not greater than 30 μm, and the thickness of the anti-adhesion layer is not greater than 15 nm. According to claim 15, a method for fabricating a diffraction grating is characterized in that, in step (5), an anti-adhesion layer is deposited on the entire surface of the substrate in step (4) to reduce the adhesion of the non-grating structure region and increase the surface contact angle of the non-grating structure region; the surface contact angle of the anti-adhesion layer is not less than 109°. According to claim 15, a method for fabricating a diffraction grating is characterized in that, in step (6), the second blocking layer is removed so that the adhesive layer on the surface of the substrate is fully exposed, so that the high-folding printing adhesive is in complete contact with the adhesive layer, thereby enhancing the bonding force between the high-folding printing adhesive and the substrate. A selective imprinting method based on surface modification according to claim 15 or 17, characterized in that, in step (8), specifically, it includes exposing only the surface of the substrate between the grating structure regions, or exposing all substrate surfaces outside the grating structure regions. According to claim 15 or 17, a selective area imprinting method based on surface modification is characterized in that, in step (8), in detail, the high-fold imprinting adhesive of the non-grating structure area with poor adhesion to the substrate surface is peeled off by physical demolding, while the diffraction grating structure of the grating structure area remains on the adhesive layer of the substrate due to the strong bonding force of the adhesive layer, thereby obtaining the imprinted diffraction grating product.