Low-cost manufacturing of optical devices using individual diffractive module assemblies - Patents.com

Abstract

An embodiment of the present disclosure relates to optical device fabrication using a method of individual grating assembly and optical interconnection. Individual gratings corresponding to one of the input coupling grating, intermediate grating, or output coupling grating of the optical device are formed on a separate donor substrate. The donor substrate is diced into individual gratings and bonded to the optical device substrate. Inkjet material is disposed between the gratings to optically interconnect portions of the optical device.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE

[0002] Embodiments of the present disclosure relate generally to optical device manufacturing. In particular, embodiments of the present disclosure relate to optical device manufacturing using discrete diffraction grating assemblies and optical interconnect methods. [Background technology]

[0002] Virtual reality (VR) is generally considered to be a computer-generated simulated environment in which a user has an apparent physical presence. VR experiences are generated in 3D and may be viewed using a head-mounted display (HMD), such as glasses or other wearable display devices, that have a near-eye display panel as a lens to display the VR environment that replaces the real environment.

[0003] Augmented reality (AR), however, allows for an experience in which a user can not only see the surrounding environment through the display lenses of glasses or other HMD devices, but also see images of virtual objects that are generated for display and appear as part of the environment. AR can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and video, that enhance or extend the environment experienced by the user. To achieve an AR experience, the virtual images are overlaid on the surrounding environment, and the overlay is performed by optical devices.

[0004] A plurality of optical devices are fabricated on a substrate and then diced prior to use in a VR and AR device. As a result, the substrate may only hold a minimum number of optical devices, and a large portion of the substrate's surface area is unused. Thus, a method of optical device fabrication is needed that increases the number of optical devices that can be fabricated. Summary of the Invention

[0005] In one embodiment, an optical device is provided. The optical device includes an optical device substrate, a portion of a first donor substrate disposed on a top surface of the optical device substrate, and a first diffraction grating disposed on the portion of the first donor substrate. The first diffraction grating includes a first plurality of optical device structures. The optical device further includes a portion of a second donor substrate disposed on a top surface of the optical device substrate, and a second diffraction grating disposed on the portion of the second donor substrate. The second diffraction grating includes a second plurality of optical device structures and an inkjet material disposed between the first diffraction grating and the second diffraction grating. The inkjet material includes an inkjet height that is flush with or greater than the height of the first plurality of optical device structures and the second plurality of optical device structures.

[0006] In another embodiment, an optical device is provided. The optical device includes an optical device substrate having a first refractive index and a portion of a first donor substrate disposed on a top surface of the optical device substrate. The first donor substrate has a second refractive index. The optical device further includes a first diffraction grating disposed on the portion of the first donor substrate. The first diffraction grating includes a first plurality of optical device structures. The optical device further includes a portion of a second donor substrate disposed on a top surface of the optical device substrate. The portion of the second donor substrate includes a third refractive index. The optical device further includes a second diffraction grating disposed on the portion of the second donor substrate, the second diffraction grating including a second plurality of optical device structures. The optical device further includes an inkjet material disposed between the first diffraction grating and the second diffraction grating. The inkjet material has an inkjet refractive index, and the inkjet refractive index, the first refractive index, the second refractive index, and the third refractive index are substantially equal.

[0007] In yet another embodiment, a method of forming an optical device is provided. The method includes forming an input coupling grating on a first donor substrate, forming an output coupling grating on a second donor substrate, and trimming each of the first donor substrate and the second donor substrate to a donor substrate height. The method further includes dicing each input coupling grating and each output coupling grating into a portion of the first donor substrate and a portion of the second donor substrate, adhering the portion of the first donor substrate and the portion of the second donor substrate to a top surface of an optical device substrate, and disposing an inkjet material between the input coupling grating and the output coupling grating on the optical device substrate.

[0008] So that the above recited features of the present disclosure may be understood in detail, a more particular description of the present disclosure, briefly summarized above, may be made by reference to embodiments, some of which are illustrated in the accompanying drawings, It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered limiting of its scope, as other equally effective embodiments may be recognized. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic plan view of an optical device according to an embodiment described herein; [Figure 2A] 1 is a schematic plan view of a donor substrate according to embodiments described herein; [Figure 2B] 1 is a schematic plan view of a donor substrate according to embodiments described herein; [Figure 2C] 1 is a schematic plan view of a donor substrate according to embodiments described herein; [Diagram 3] 4A-4F are flow diagrams of methods for forming the optical device shown in FIGS. 4A-4F according to embodiments described herein. [Figure 4A]4A-4C are schematic side views of the formation of an optical device in the method according to embodiments described herein. [Figure 4B] 4A-4C are schematic side views of the formation of an optical device in the method according to embodiments described herein. [Figure 4C] 4A-4C are schematic side views of the formation of an optical device in the method according to embodiments described herein. [Figure 4D] 4A-4C are schematic side views of the formation of an optical device in the method according to embodiments described herein. [Figure 4E] 4A-4C are schematic side views of the formation of an optical device in the method according to embodiments described herein. [Figure 4F] 4A-4C are schematic side views of the formation of an optical device in the method according to embodiments described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] For ease of understanding, wherever possible, like reference numbers have been used to designate like elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011] FIELD OF THE DISCLOSURE

[0002] Embodiments of the present disclosure relate generally to optical device manufacturing. In particular, embodiments of the present disclosure relate to optical device manufacturing using discrete diffraction grating assemblies and optical interconnect methods.

[0012] 1 is a schematic plan view of an optical device 100. It should be understood that the optical device 100 described below is an exemplary optical device. In one embodiment, which may be combined with other embodiments described herein, the optical device 100 is a waveguide combiner, such as an augmented reality waveguide combiner. The optical device 100 may also be an optical device utilized for optical sensing (e.g., eye tracking functionality). In another embodiment, which may be combined with other embodiments described herein, the optical device 100 is a flat optical device, such as a metasurface.

[0013] The optical device 100 includes a plurality of optical device structures 102. The optical device structures 102 are disposed on a portion 105 of a donor substrate 115 (shown in FIG. 2). The device structures 102 may be nanostructures having submicron dimensions, e.g., nano-sized dimensions. For example, a critical dimension 106 of the optical device structures 102 has a submicron dimension. In one example, the critical dimension 106 is less than 2 micrometers (μm). In another example, the critical dimension 106 is between about 100 nanometers (nm) and about 1000 nm.

[0014] In one embodiment, which may be combined with other embodiments described herein, regions of the device structure 102 correspond to one or more diffraction gratings 104, such as a first diffraction grating 104A, a second diffraction grating 104B, and a third diffraction grating 104C. The first diffraction grating 104A corresponds to an input coupling diffraction grating. The second diffraction grating 104B corresponds to an intermediate diffraction grating. The third diffraction grating 104C corresponds to an output coupling diffraction grating. Each of the diffraction gratings 104 is disposed on a respective portion 105 of the donor substrate 115 (shown in FIG. 2). Each portion 105 is disposed on a top surface 103 of the optical device substrate 101.

[0015] In some embodiments that may be combined with other embodiments described herein, the cross sections of the optical device structures 102 have cross sections with different shapes. In other embodiments that may be combined with other embodiments described herein, the cross sections of the optical device structures 102 of the optical device 100 have cross sections with substantially the same shape. In some embodiments that may be combined with other embodiments described herein, at least one of the critical dimensions 106 of the optical device structures 102 may be different from other critical dimensions 106 of the optical device structures 102. In other embodiments that may be combined with other embodiments described herein, the critical dimensions 106 of the optical device structures 102 are the same.

[0016] In one embodiment, which may be combined with other embodiments described herein, the structural material of the optical device structure 102 includes a non-conductive material, such as a dielectric material. The dielectric material may include an amorphous material, a polycrystalline material, or a crystalline material. Examples of dielectric materials include, but are not limited to, silicon-containing materials, such as Si, silicon nitride (Si3N4), silicon oxynitride, silicon carbide (SiC), silicon carbonitride (SiCN), silicon dioxide, fused silica, or quartz. The silicon may be crystalline silicon, polycrystalline silicon, or amorphous silicon (a-Si). In another embodiment, which may be combined with other embodiments described herein, the construction material of the optical device structure 102 may be, but is not limited to, titanium dioxide (TiO2), zinc oxide (ZnO), tin dioxide (SnO2), aluminum doped zinc oxide (AZO), fluorine doped tin oxide (FTO), cadmium stannate (Cd2SnO4), cadmium stannate (tin oxide) (CTO), zinc stannate (SnZnO3), tantalum oxide (Ta2O5), vanadium(IV) oxide (VO x ), or niobium oxide (Nb2O5)-containing materials. In yet another embodiment, which may be combined with other embodiments described herein, the material of the optical device structure 102 includes a nanoimprint resist material. Examples of nanoimprint resist materials include, but are not limited to, silicon oxycarbide (SiOC), TiO2, silicon dioxide (SiO2), vanadium(IV) oxide (VO x ), aluminum oxide (Al2O3), indium tin oxide (ITO), ZnO, tantalum oxide (Ta2O5), silicon nitride (Si3N4), titanium nitride (TiN), zirconium dioxide (ZrO2) containing materials, or combinations thereof.

[0017] The optical device substrate 101 and the donor substrate 115 may be formed from materials including, but not limited to, silicon (Si), silicon dioxide (SiO2), fused silica, quartz, silicon carbide (SiC), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), diamond, gallium nitride (GaN), gallium oxide (Ga2O3), or sapphire-containing materials. In another embodiment, which may be combined with other embodiments described herein, the optical device substrate 101 and the donor substrate 115 include high index glasses, such as one or more of silicon dioxide (SiO2), boron oxide (BO3), titanium oxide (TiO2), zirconium dioxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), lanthanum oxide (La2O3), bismuth oxide (Bi2O3), zinc oxide (ZnO), lead oxide (PbO), lithium oxide (Li2O), sodium oxide (Na2O), potassium oxide (KO), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), aluminum oxide (Al2O3), and gallium oxide (Ga2O3). The materials of the optical device substrate 101 and the donor substrate 115 may be different. The optical device substrate 101 has a first refractive index of about 1.6 to about 3.0. The donor substrate 115 has a second refractive index of about 1.6 to about 3.0.

[0018] In some embodiments, the inkjet material 108 is disposed between the plurality of diffraction gratings 104. The inkjet material 108 is a flowable material that can be deposited on selective areas on the optical device substrate 101 and the donor substrate 115 using inkjet printing. The inkjet material 108 can be further crosslinked or cured after printing to produce a solidified film. The inkjet material 108 is adjusted to have an inkjet refractive index close to or equal to the refractive index of the optical device structure 102. In one embodiment, which can be combined with other embodiments described herein, the ink for producing the inkjet material 108 is a colloidal dispersion of nanoparticles. For example, the nanoparticles can include one or more of titanium oxide (TiO2), zirconium dioxide (ZrO2), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), lanthanum oxide (La2O3), bismuth oxide (Bi2O3), or zinc oxide (ZnO). In another embodiment, which may be combined with other embodiments described herein, the ink is derived from metal oxide precursors, including, but not limited to, metal alkoxides, metal acetates, and metal nitrates. Some example precursors include titanium tetraisopropoxide, zirconium butoxide, zirconium acetate, zirconium acetylacetonate, tantalum ethoxide, zinc nitrate, and zinc acetate. The ink formulation may include the following components: solvents, such as water, ethanol, propylene glycol methyl ether, and cyclopentanone; acids and bases, such as acetic acid, hydrochloric acid, citric acid, sodium hydroxide, and ethanolamine; and crosslinkers, monomers, and polymers, such as triethylene glycol dimethacrylate, 9-vinylcarbazole, polyimides, and polyphosphonates. The inkjet material 108 after curing has an inkjet refractive index between about 1.6 and about 3.0. The refractive index of the optical device structure 102 is also between about 1.6 and about 3.0.

[0019] 2A-C are schematic plan views of a donor substrate 115. Each donor substrate 115 includes a plurality of diffraction gratings 104. Each diffraction grating 104 includes a plurality of optical device structures 102 (shown in detail in FIG. 1). The plurality of diffraction gratings 104A-C are each fabricated on a separate donor substrate 115 to allow for dense packing of the diffraction gratings 104. The plurality of diffraction gratings 104 are not limited to rectangular shapes as shown in FIGS. 2A-C.

[0020] 2A includes a first configuration 200A of a donor substrate 115. The first configuration 200A includes a plurality of first gratings 104A formed on the donor substrate 115. Each of the plurality of first gratings 104A corresponds to an input coupling grating. Each donor substrate 115 may have between 4 and 3000 first gratings 104A depending on the size of the donor substrate 115. For example, the donor substrate 115 may include about 160 of the first gratings 104A. The plurality of first gratings 104A may be formed on the donor substrate 115 as needed to maximize the number of first gratings 104A on the donor substrate 115.

[0021] 2B includes a second configuration 200B of the donor substrate 115. The second configuration 200B includes a plurality of second gratings 104B formed on the donor substrate 115. Each of the plurality of second gratings 104B corresponds to an intermediate grating. Each donor substrate 115 may have between 4 and 300 second gratings 104B depending on the size of the donor substrate 115. For example, the donor substrate 115 may include about 32 of the second gratings 104B. The plurality of second gratings 104B may be formed on the donor substrate 115 to increase or maximize the number of second gratings 104B on the donor substrate 115, as needed.

[0022] 2C includes a third configuration 200C of the donor substrate 115. The third configuration 200C includes a plurality of third gratings 104C formed on the donor substrate 115. Each of the plurality of third gratings 104C corresponds to an output grating. Each donor substrate 115 may have between 4 and 300 third gratings 104C depending on the size of the donor substrate 115. For example, the donor substrate 115 may include about 24 of the third gratings 104C. The plurality of third gratings 104C may be formed on the donor substrate 115 to maximize the number of third gratings 104C on the donor substrate 115, as needed.

[0023] Forming the first grating 104A, the second grating 104B, and the third grating 104C on separate donor substrates 115 allows for utilization of more surface area of ​​the donor substrate 115. As described below in method 300, forming the first grating 104A, the second grating 104B, and the third grating 104C on separate donor substrates 115 reduces the cost of optical device manufacturing by utilizing more surface area of ​​the donor substrate 115. Furthermore, the fabrication of the first grating 104A, the fabrication of the second grating 104B, and the fabrication of the third grating 104C may each employ different manufacturing processes. Thus, the manufacturing cost may be further reduced by forming each grating separately so that each donor substrate 115 may undergo the same manufacturing process.

[0024] FIG. 3 is a flow diagram of a method 300 for forming the optical device 100 shown in FIGS. 4A-4F. FIGS. 4A-4F are schematic side views of the formation of the optical device 100 during the method 300. For ease of explanation, the method 300 and FIGS. 4A-4F show the optical device 100 with a first diffraction grating 104A (e.g., an input coupling diffraction grating) and a third diffraction grating 104C (e.g., an output coupling diffraction grating), however, the method 300 also contemplates the formation of an optical device 100 with a second diffraction grating 104B (e.g., an intermediate diffraction grating). Additionally, although the optical device structures 102 of each diffraction grating 104 are formed with the same height 402, it is contemplated that the height 402 of each of the optical device structures 102 may vary across the donor substrate 115.

[0025] In step 301, a plurality of gratings 104 are patterned on a donor substrate 115, as shown in FIG. 4A. FIG. 4A only shows that a first grating 104A is formed on a donor substrate 115, but a second grating 104B and / or a third grating 104C are formed on different donor substrates 115. The plurality of gratings 104 on each donor substrate 115 are substantially identical. It is contemplated that the method 300 described herein is not limited to one grating type on one donor substrate 115. It is contemplated to design and fabricate different gratings on the same donor substrate 115 to further utilize the blank area of ​​each respective donor substrate 115. For ease of explanation, steps 301-303 are described with respect to the first grating 104A. However, steps 301-303 may also be performed with respect to the second grating 104B and the third grating 104C. Although only three of the first gratings 104A are shown in FIG. 4A, it is contemplated that any number of gratings 104 may be formed on the donor substrate 115.

[0026] In step 302, the donor substrate 115 is trimmed, as shown in FIG. 4B. The donor substrate 115 is trimmed to a donor substrate height 408. The donor substrate height 408 is determined based on a predetermined substrate thickness 412 (shown in FIG. 4E and FIG. 4F). The predetermined substrate thickness 412 is the sum of the donor substrate height 408 and the optical device substrate height 410. The donor substrate 115 is trimmed such that the predetermined substrate thickness 412 is achieved when placed on the optical device substrate 101. For example, the desired substrate thickness 412 is 800 μm and the optical device substrate height 410 is 500 μm, so the donor substrate height 408 will be about 300 μm.

[0027] In step 303, as shown in FIG. 4C, each grating 104 (e.g., each first grating 104A shown in FIG. 4C) is diced into portions 105 of a donor substrate 115. The portions 105 are diced by laser ablation cutting, filamentation, diamond blade cutting, or a substrate dicing process using a precision dicing saw.

[0028] In step 304, as shown in FIG. 4D, the portion 105 of the donor substrate 115 with the first grating 104A and the portion 105 of the donor substrate 115 with the third grating 104C are placed in close proximity to the optical device substrate 101. In some embodiments, the portion 105 of the donor substrate 115 with the second grating 104B (not shown) is bonded to the optical device substrate 101. To assist in aligning the donor substrate 115 with the optical device substrate 101, alignment marks are designed and fabricated on the optical device substrate 101 and the donor substrate 115. The alignment marks may be complementary in shape, or the position of each mark may be read by an alignment system to calculate and align the relative positions of the optical device substrate 101 and the donor substrate 115. The plurality of optical device structures 102 of the first diffraction grating 104A are perpendicular to the surface 202 of the donor substrate 115 and the top surface 103 of the optical device substrate 101. The plurality of optical device structures 102 of the third diffraction grating 104C are angled relative to the surface 202 of the donor substrate 115 and the top surface 103 of the optical device substrate 101. Each of the diffraction gratings 104 can be angled or perpendicular relative to the surface 202.

[0029] In step 305, as shown in FIG. 4E, the portion 105 of the donor substrate 115 with the first grating 104A is bonded to the optical device substrate 101. Additionally, the portion 105 of the donor substrate 115 with the third grating 104C is bonded to the optical device substrate 101. In some embodiments, the portion 105 of the donor substrate 115 with the second grating 104B (not shown) is bonded to the optical device substrate 101. The portions 105 of the donor substrate 115 are bonded to the optical device substrate by bonding to the portions 105 using a process such as adhesive bonding, glass frit bonding, or fusion bonding. Fusion bonding refers to the spontaneous adhesion of two planar substrates without the addition of an intermediate layer. In fusion bonding, a plasma pretreatment may be used to generate a clean surface free of organic contamination.

[0030] In step 306, as shown in FIG. 4F, inkjet material 108 is disposed on the optical device substrate 101 to form the optical device 100. The inkjet material 108 is disposed so as to be intermediate the optical device structures 102 of each diffraction grating 104. The inkjet material 108 is also disposed so as to be between each adjacent donor substrate 115. The inkjet material 108 is disposed via an inkjet printing process. The inkjet material 108 is disposed with an inkjet height 404. The inkjet height 404 is flush with or higher than the top surface 406 of the optical device structures 102.

[0031] The inkjet refractive index is substantially equal to the first refractive index of the optical device substrate 101 and the second refractive index of the donor substrate 115. The inkjet material 108 optically interconnects the first diffraction grating 104A to the third diffraction grating 104C such that the optical path of the incident light on the optical device 100 allows for total internal reflection. For example, since the inkjet refractive index is substantially equal to the first refractive index of the optical device substrate 101 and the second refractive index of the donor substrate 115, the light is able to propagate through the optical device 100. The inkjet material 108 does not require an extra patterning step to define the area of ​​interconnection between the diffraction gratings 104.

[0032] In summary, optical device fabrication using a method of individual grating assembly and optical interconnection is provided herein. During the process, individual gratings corresponding to one of the input coupling grating, intermediate grating, or output coupling grating of the optical device are formed on a separate donor substrate. The donor substrate is diced into individual gratings and bonded to the optical device substrate. Inkjet material is disposed between the gratings to optically interconnect portions of the optical device. By forming each grating on a separate substrate, optical device manufacturing costs are reduced due to improved use of the substrate surface area.

Claims

1. An optical device substrate; a portion of a first donor substrate disposed on a top surface of the optical device substrate; a first diffraction grating disposed on the portion of the first donor substrate, the first diffraction grating including a first plurality of optical device structures; and a portion of a second donor substrate disposed on the top surface of the optical device substrate; a second diffraction grating disposed on the portion of the second donor substrate, the second diffraction grating including a second plurality of optical device structures; and an inkjet material disposed between the first diffraction grating and the second diffraction grating, the inkjet material having an inkjet height that is flush with or greater than a height of the first plurality of optical device structures and the second plurality of optical device structures; An optical device comprising:

2. 2. The optical device of claim 1 , wherein the inkjet material has an inkjet refractive index, the optical device substrate has a first refractive index, the first donor substrate has a second refractive index, and the second donor substrate has a third refractive index, and the first refractive index, the second refractive index, the third refractive index, and the inkjet refractive index are substantially equal.

3. The optical device of claim 2 , wherein the inkjet refractive index is between about 1.6 and about 3.

0.

4. The optical device of claim 1 , wherein the inkjet material comprises a colloidal dispersion of nanoparticles or metal oxide precursors.

5. a portion of a third donor substrate disposed on the top surface of the optical device substrate; a third diffraction grating disposed on the portion of the third donor substrate, the third diffraction grating including a third plurality of optical device structures, the third diffraction grating corresponding to an intermediate diffraction grating; and The optical device of claim 1 further comprising:

6. The optical device of claim 1 , wherein the first grating is an input coupling grating.

7. The optical device of claim 1 , wherein the second grating is an output coupling grating.

8. The optical device of claim 1 , wherein the inkjet material is operable to optically interconnect the first diffraction grating to the second diffraction grating to create an optical path for incident light.

9. the first plurality of optical device structures are perpendicular to the top surface of the optical device substrate; the second plurality of optical device structures are non-perpendicular to the top surface of the optical device substrate; 2. The optical device of claim 1.

10. The optical device of claim 1 , wherein the inkjet height is flush with the height of the first and second plurality of optical device structures.

11. an optical device substrate, the optical device substrate having a first refractive index; a portion of a first donor substrate disposed on a top surface of the optical device substrate, the first donor substrate having a second refractive index; a first diffraction grating disposed on the portion of the first donor substrate, the first diffraction grating including a first plurality of optical device structures; and a portion of a second donor substrate disposed on the top surface of the optical device substrate, the portion of the second donor substrate having a third refractive index; a second diffraction grating disposed on the portion of the second donor substrate, the second diffraction grating including a second plurality of optical device structures; and an inkjet material disposed between the first diffraction grating and the second diffraction grating, the inkjet material having an inkjet refractive index, the inkjet refractive index, the first refractive index, the second refractive index, and the third refractive index being substantially equal; and An optical device comprising:

12. 12. The optical device of claim 11, wherein the inkjet refractive index is between about 1.6 and about 3.

0.

13. The optical device of claim 11 , wherein the inkjet material comprises a colloidal dispersion of nanoparticles or metal oxide precursors.

14. The optical device of claim 11 , wherein the first grating is an input coupling grating.

15. The optical device of claim 11 , wherein the second grating is an output coupling grating.

16. The optical device of claim 11 , wherein the inkjet material is operable to optically interconnect the first diffraction grating to the second diffraction grating to form an optical path for incident light.

17. forming an input coupling grating on a first donor substrate; forming an output coupling grating on a second donor substrate; trimming each of the first donor substrate and the second donor substrate to a donor substrate height; dicing each input coupling grating and each output coupling grating into a portion of the first donor substrate and a portion of the second donor substrate; bonding the portion of the first donor substrate and the portion of the second donor substrate to a top surface of an optical device substrate; disposing an inkjet material on the optical device substrate between the input coupling grating and the output coupling grating; 23. A method of forming an optical device comprising:

18. 20. The method for forming an optical device of claim 17, wherein the inkjet material optically interconnects the input coupling grating to the output coupling grating to form an optical path for incident light.

19. 20. The method of claim 17, further comprising disposing the inkjet material directly on the top surface of the optical device substrate and between the first donor substrate and the second donor substrate.

20. forming an intermediate grating on a third donor substrate; trimming the third donor substrate to the donor substrate height; dicing each of the intermediate gratings onto a portion of the third donor substrate; adhering the portion of the third donor substrate to the top surface of the optical device substrate; disposing an inkjet material on the optical device substrate between the input coupling grating, the output coupling grating, and the intermediate grating; 20. The method of forming the optical device of claim 17, further comprising:

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