Blazed grating formation using step etching

Abstract

Embodiments herein are generally directed to methods of forming a waveguide structure having a blazed grating. The methods include depositing a photoresist layer on a patterned hardmask disposed above a device layer or a substrate, exposing the photoresist layer to produce a plurality of photoresist segments, etching the device layer or the substrate to produce at least one step forming a blazed grating, trimming the plurality of photoresist segments horizontally, and removing the plurality of photoresist segments and the patterned hardmask. The methods can further include repeating the steps to produce a second step and a third step of the blazed grating.

Description

Technical Field

[0001] The embodiments of this disclosure generally relate to optical waveguides. More specifically, the embodiments described herein provide techniques for forming waveguides with blazed gratings. Background Technology

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

[0003] However, augmented reality enables experiences where users can still see their surroundings through the display lenses of glasses or other HMD devices, and also see images of virtual objects generated to be displayed and appear as part of the environment. Augmented reality can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and videos of the environment that enhance or augment the user experience. As an emerging technology, augmented reality faces many challenges and design constraints.

[0004] Blazed gratings are required in AR waveguides to achieve high diffraction efficiency at the target order. However, it is difficult to fabricate blazed facets using conventional patterning. Currently, there is no scalable industrial solution for forming blazed gratings for AR waveguides.

[0005] Therefore, there is a need for improved systems and methods for forming blazed grating structures. Summary of the Invention

[0006] The embodiments described herein are generally directed to methods for forming optical element structures such as blazed gratings.

[0007] In one embodiment, a method for forming an optical element structure is provided. The method includes: depositing a photoresist layer on a patterned hard mold disposed above an element layer or a substrate; exposing the photoresist layer to generate a plurality of photoresist segments; etching the element layer or the substrate to generate at least one step, the at least one step forming a blazed grating; horizontally trimming the plurality of photoresist segments; and removing the plurality of photoresist segments and the patterned hard mold.

[0008] In another embodiment, a method for forming an optical element structure is provided. The method includes: depositing a photoresist layer on a patterned hard mold having a plurality of hard mold segments disposed above an element layer or a substrate; exposing the photoresist layer to generate the plurality of photoresist segments; and etching the element layer or the substrate to generate a first step of a blazed grating. The method also includes: horizontally trimming the plurality of photoresist segments; and repeatedly etching the element layer or the substrate; and horizontally trimming the plurality of photoresist segments to generate a second step of the blazed grating. The method may further include: repeatedly etching the element layer and horizontally trimming the plurality of photoresist segments to generate a third step of the blazed grating; and removing the plurality of photoresist segments and the patterned hard mold.

[0009] In another embodiment, a method for forming an optical element structure is provided. The method includes: depositing a photoresist layer on a patterned hard mold disposed above an element layer or substrate; patterning the photoresist layer to generate a plurality of photoresist segments; etching the element layer or substrate to generate a first step of a blazed grating with a first linewidth; and horizontally trimming the plurality of photoresist segments. The method also includes: repeatedly etching the element layer or substrate and horizontally trimming the plurality of photoresist segments to generate a second step of the blazed grating with a second linewidth; and removing the plurality of photoresist segments and the patterned hard mold. In one aspect, the second linewidth of the second step is non-uniformly larger than the first linewidth of the first step. Attached Figure Description

[0010] To gain a more detailed understanding of the features described above, a more specific description of the present disclosure can be obtained by referring to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only exemplary embodiments of the present disclosure and should not be construed as limiting its scope; other equally effective embodiments are permissible.

[0011] Figure 1A It is a perspective front view of an optical element according to certain embodiments.

[0012] Figure 1B and Figure 1C It is a schematic cross-sectional view of a plurality of element structures according to certain embodiments.

[0013] Figure 2 This is a flowchart of a method for forming an optical element structure according to certain embodiments.

[0014] Figure 3A to Figure 3I According to certain implementation methods, it undergoes the process of forming Figure 2 A schematic cross-sectional view of the waveguide structure of the method.

[0015] To facilitate understanding, the same reference numerals are used to denote common elements in the figures where possible. Elements and features of one embodiment are contemplated to be advantageously incorporated into other embodiments without further description. Detailed Implementation

[0016] The embodiments described herein are generally directed to a method for forming a waveguide structure with a blazed grating. The method includes exposing a component layer disposed above a substrate having a patterned hard mold and an offset patterned photoresist to an etchant.

[0017] Figure 1A This is a front view of optical element 100. It should be understood that the optical element 100 described below is an exemplary optical element. In one embodiment, which may be combined with other embodiments described herein, optical element 100 is a waveguide combiner, such as an augmented reality waveguide combiner. In another embodiment, which may be combined with other embodiments described herein, optical element 100 is a planar optical element, such as a metasurface. Optical element 100 includes components disposed in a substrate 101 (e.g., Figure 1B (as shown) or on the substrate (such as) Figure 1C The structure of multiple components (as shown). For example... Figure 1C As shown, the element structure is formed in an element layer 103 formed on a substrate 101. The element structure can have submicron dimensions, such as nanoscale dimensions, like nanostructures with a critical size of less than 1 μm. The optical element 100 includes multiple gratings 106 (such as...) Figure 1B and Figure 1C The input coupling region 102A, waveguide region 102B, and output coupling region 102C are defined in the figure.

[0018] Input coupling region 102A receives an incident beam (virtual image) of a certain intensity from the microdisplay. Each of the plurality of gratings 106 divides the incident beam into multiple modes. The zero-order mode (T0) beam is refracted back or lost in the optical element 100. The positive first-order mode (T1) beam passes through the optical element 100, undergoes total internal reflection (TIR) ​​across waveguide region 102B to reach the output coupling region 102C and is output for display. The negative first-order mode (T-1) beam propagates in the optical element 100 in the opposite direction to the T1 beam. In diffraction order, only the T1 beam is output to the display through the output coupling region 102C, while other modes are lost due to their different directivity. Therefore, it is crucial to increase the intensity of the T1 beam and decrease the intensity of the other order beams to achieve higher element optical efficiency. One method for increasing the intensity of the T1 beam and decreasing the intensity of the other order beams is to control the shape of each grating in the plurality of gratings 106. The blazing shape of each of the plurality of gratings 106 provides improved optical efficiency.

[0019] Figure 1B and Figure 1C This is a schematic cross-sectional view of a plurality of blazed gratings 106 according to certain embodiments. In one embodiment, which can be combined with other embodiments described herein, the plurality of blazed gratings 106 correspond to an input coupling region 102A of an optical element 100. The method 200 described herein forms a plurality of blazed gratings 106. A waveguide combiner according to one embodiment that can be combined with other embodiments described herein may include blazed gratings 106. Each blazed grating in blazed grating 106 includes a blazed surface 108, a top surface 109, a sidewall 112, a depth h, and a linewidth d. The blazed surface 108 has a plurality of steps 110. In one embodiment, which can be combined with other embodiments described herein, the blazed surface 108 includes at least three steps 110, such as more than 16 steps 110, for example, 32 steps 110. The blazed surface 108 has a blaze angle γ and a blaze linewidth d2. The blaze angle γ is the angle between the blaze surface 108 and the surface parallel to the substrate 101, and the angle between the surface normal of the substrate 101 and the facet normal f of the blaze surface 108. The depth h corresponds to the height of the sidewall 112, and the linewidth d corresponds to the distance between the sidewalls 112 of adjacent blaze gratings 106. The blaze linewidth d2 corresponds to the difference between the linewidth d and the width of the top surface 109 of each blaze grating 106.

[0020] In one embodiment that can be combined with other embodiments described herein, the blaze angle γ of two or more blaze gratings 106 is different. In another embodiment that can be combined with other embodiments described herein, the blaze angle γ of the two or more blaze gratings 106 is the same. In one embodiment that can be combined with other embodiments described herein, the depth h of two or more blaze gratings 106 is different. In another embodiment that can be combined with other embodiments described herein, the depth h of two or more blaze gratings 106 is the same. In one embodiment that can be combined with other embodiments described herein, the linewidth d of two or more blaze gratings 106 is different. In another embodiment that can be combined with other embodiments described herein, the linewidth d of one or more blaze gratings 106 is the same.

[0021] Figure 2 It is used to form as shown in Figure 3A to Figure 3I A flowchart of a method 200 for a plurality of blazed gratings 106 in an optical element structure 300 is shown. In one embodiment, the optical element structure 300 corresponds to the input coupling region 102A of the optical element 100 and includes a plurality of blazed gratings etched in a substrate 302, the plurality of blazed gratings being similar to Figure 1B The blazed grating 106 formed in the substrate 101 is shown.

[0022] The substrate 302 can be any substrate used in the art, and depending on its intended use as a substrate for a waveguide, it can be opaque or transparent to light of a selected wavelength. Substrate selection can include substrates of any suitable material, including but not limited to amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, polymers, or combinations thereof. In some embodiments, substrate 302 includes, but is not limited to, silicon-containing materials, silicon- and oxygen-containing compounds, germanium-containing materials, indium- and phosphide-containing compounds, gallium- and arsenic-containing compounds, gallium- and nitrogen-containing compounds, carbon-containing materials, silicon- and carbon-containing compounds, silicon-, carbon- and oxygen-containing compounds, silicon- and nitrogen-containing compounds, silicon-, oxygen- and nitrogen-containing compounds, niobium- and oxygen-containing compounds, lithium-, niobium- and oxygen-containing compounds, aluminum- and oxygen-containing compounds, indium-, tin- and oxygen-containing compounds, titanium- and oxygen-containing compounds, lanthanum- and oxygen-containing compounds, gadolinium- and oxygen-containing compounds, zinc- and oxygen-containing compounds, yttrium- and oxygen-containing compounds, tungsten- and oxygen-containing compounds, potassium- and oxygen-containing compounds, phosphorus- and oxygen-containing compounds, barium- and oxygen-containing compounds, sodium- and oxygen-containing compounds, or combinations thereof. In other embodiments that can be combined with other embodiments described herein, substrate 302 comprises an oxide including one or more of a material containing gadolinium, silicon, sodium, barium, potassium, tungsten, phosphorus, zinc, calcium, titanium, tantalum, niobium, lanthanum, zirconium, lithium, or yttrium. Exemplary materials for substrate 302 include silicon (Si), silicon monoxide (SiO), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, diamond, germanium quartz (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), sapphire, sapphire (Al2O3), lithium niobate (LiNbO3), indium tin oxide (ITO), lanthanum oxide (La2O3), gadolinium oxide (Gd2O5), zinc oxide (ZnO), yttrium oxide (Y2O3), tungsten oxide (WO3), titanium oxide (TiO2), zirconium oxide (ZrO3), sodium oxide (Na2O), niobium oxide (Nb2O5), barium oxide (BaO), potassium oxide (K2O), phosphorus pentoxide (P2O5), calcium oxide (CaO), or combinations thereof.

[0023] In another embodiment, the plurality of blazed gratings are etched into a component layer (not shown) formed above the substrate 302, similar to Figure 1CThe diagram shows a blazed grating 106 formed in a component layer 103 above a substrate 101. In this embodiment, the component layer 103 and the substrate 101 comprise different materials. The component layer 103 comprises, but is not limited to, one or more oxides, carbides, or nitrides of silicon, aluminum, zirconium, tin, tantalum, zirconium, barium, titanium, hafnium, lithium, lanthanum, cadmium, niobium, or combinations thereof. Exemplary materials for element layer 103 include silicon carbide, silicon oxycarbide, titanium oxide, titanium dioxide, silicon oxide, silicon dioxide, vanadium oxide, aluminum oxide, aluminum-doped zinc oxide, indium tin oxide, tin oxide, zinc oxide, tantalum oxide, tantalum pentoxide, silicon nitride, titanium nitride, zirconium oxide, zirconium dioxide, niobium oxide, cadmium stannate, silicon oxynitride, barium titanate, diamond-like carbon, hafnium oxide, lithium niobate, silicon carbonitride, silver, cadmium selenide, mercury telluride, zinc selenide, silver indium gallium sulfide, silver indium sulfide, indium phosphide, gallium phosphide, lead sulfide, lead selenide, zinc sulfide, molybdenum sulfide, tungsten sulfide, or combinations thereof.

[0024] In this embodiment, prior to performing method 200, a device layer 103 may be deposited on the substrate 101 to form Figure 1C The blazed grating 106 is shown. Any suitable method for depositing the element layer 103 can be used. Examples of suitable thin film deposition methods include physical vapor deposition (PVD) processes (e.g., ion beam sputtering, magnetron sputtering, electron beam evaporation), chemical vapor deposition (CVD) processes, plasma-enhanced chemical vapor deposition (PECVD) processes, atomic layer deposition (ALD) processes, inkjet printing processes, or three-dimensional (3D) printing processes.

[0025] As shown in Figure 3A, before operation 201, on substrate 302 (or Figure 1C A hard mold 306 is disposed and patterned on the component layer 103 (if present). The patterned hard mold 306 includes multiple hard mold segments, such as a first hard mold segment 306a, a second hard mold segment 306b, and a third hard mold segment 306c separated from each other. The spacing (e.g., distance) between the segments of the patterned hard mold 306 determines the maximum width of the stepped surface 108 of each resulting blazed grating structure. The substrate 302 (or...) Figure 1CThe portions of the element layer 103 (if present) are then exposed through the spacing between the segments of the patterned hard mold 306. Figure 3B is a schematic cross-sectional view of the substrate 302 at operation 201. In operation 201, as shown in Figure 3B, a photoresist layer 308 is deposited or otherwise disposed on the exposed portions (or...) of the hard mold segments 306 and the substrate 302. Figure 1C Above the component layer 103 (if present). The material of the photoresist layer 308 is based on the etching chemistry of the substrate 302 (where the substrate 302 is etched to form such a layer). Figure 1B In the embodiment of the blazed grating structure shown, or the etching chemical properties of element layer 103 (where element layer 103 is etched to form such a blazed grating structure) Figure 1C The blazed grating structure shown in the embodiment is selected accordingly.

[0026] In operation 202 and as shown in FIG3C, the photoresist layer 308 is patterned by a flatbed printing process (such as photolithography or digital lithography) or by a laser ablation process to form a plurality of photoresist segments 310. In an embodiment, the plurality of photoresist segments 310 include those formed on the patterned hard mold 306 and the substrate 302 (or Figure 1C The first photoresist segment 310a, the second photoresist segment 310b, and the third photoresist segment 310c are located above the element layer 103 (if present). Although only three photoresist segments 310a to 310c and three hard mold segments 306a to 306c are illustrated, the entire photoresist layer 308 and hard mold 306 can be etched so that, depending on the predetermined design for the optical element structure 300, on the substrate 302 (or Figure 1C The required number of blazed gratings 106 are formed in the element layer 103 (if present).

[0027] The multiple photoresist segments 310 are offset from the hard mold segment 306, so that the photoresist segments 310 directly contact and cover a portion of the substrate 302 (or Figure 1C The element layer 103 (if present) is exposed, while a portion of each hard stencil segment 306a, 306b, and 306c is exposed. Furthermore, the photoresist segment 310 does not extend into subsequent hard stencil segments (e.g., from the first hard stencil segment 306a to the second hard stencil segment 306b). Instead, each photoresist segment 310 terminates at a distance from the adjacent subsequent hard stencil segment 306.

[0028] At operation 203, plasma etchant 304 contacts substrate 302, such as Figure 3D As shown. The substrate 302 is exposed to a plasma etchant 304 (such as free radicals and ion beams) in contact with the substrate 302. The substrate 302 (or...) Figure 1CThe exposure of the component layer 103 (if present) to the plasma etchant 304 may include etching processes such as ion etching and reactive ion etching (RIE). The plasma etchant 304 exposes at least one step 330 to multiple depths 324 (e.g., Figures 3F to 3I The first depth 320 of the etching (shown) is etched into the substrate 302 exposed between the patterned hard mold sections 306a to 306c and the plurality of photoresist sections 310 (or Figure 1C In the various portions of the element layer 103 (if present). After operation 203, in addition to the first depth 320, the at least one step 330 also includes the initial leading sidewall portion 342 of the leading sidewall 344 (as shown in the figure). Figure 3D (as shown), tail sidewall 352, and a first linewidth 362 from the initial leading sidewall portion 342 to the tail sidewall 352. The first linewidth 362 is defined by the leading edge plane 334 defined by the first side 312 of each photoresist segment 310 and the first linewidth 362 defined by the first side 312 of each hard mold segment 306 and the substrate 302 (or Figure 1C The distance 332 between the trailing edge planes 336 defined by the exposed side 314 of the component layer 103 (if present) contacting the substrate 302 is controlled. The distance 332 corresponds to the first linewidth 362 because the plasma etchant 304 does not contact the substrate 302 (or...) outside the distance 332. Figure 1C Component layer 103 (if it exists).

[0029] At operation 204, photoresist sections 310a, 310b, and 310c are trimmed using an isotropic ion etching process, which creates vertical and horizontal recesses in the photoresist sections. This operation will be performed at a distance of 362 from the first linewidth (from...). Figure 3D The distance (defined as the initial leading sidewall portion 342 to the tail sidewall portion 352) increases to Figure 3F The distance 332 between the leading sidewall 344 and the trailing edge plane 334 is shown.

[0030] At optional operation 205, operations 203 and 204 can be repeated to etch at least one second depth 322 of a plurality of depths 324 of at least one step 330 to the substrate 302 (or Figure 1C In the element layer 103 (if present). As shown in FIG3E, each photoresist segment 310 is trimmed to reduce the width of each photoresist segment 310, such that the first side 312 of each photoresist segment 310 is offset along the substrate 302, thereby increasing the distance 332.

[0031] like Figure 3FAs shown, in addition to the second depth 322, step 330 includes a second leading sidewall portion 346 and a second linewidth 364 extending from the second leading sidewall portion 346 to the trailing sidewall portion 352. The second linewidth 364 is controlled by a distance 332 between the leading edge plane 334 and the trailing edge plane 336, increased by optional operation 204. Since the distance 332 increases with each iteration of operation 204, the second linewidth 364 is longer than the first linewidth 362. The distance 332 corresponds to the second linewidth 364 because the plasma etchant 304 does not contact the substrate 302 (or...) beyond the distance 332. Figure 1C The element layer 103 (if present). As shown in FIG3E, in various embodiments, the increase in distance 332 between the trimmed photoresist segments 310 is uniform and equal to twice the first linewidth 362, for example, the second linewidth 364 is twice the length of the first linewidth 362, such that each step in at least one step 330 is symmetrical. Alternatively, the second linewidth 364 may increase non-uniformly beyond the first linewidth 362, for example, non-uniformly greater than the first linewidth. For example, the second linewidth 364 may increase by 1.5 times the first linewidth 362, thereby producing an asymmetric stepped grating or blazed grating. Similarly, subsequent linewidths may increase symmetrically or asymmetricly.

[0032] As shown in Figures 3G and 3H, optional operation 205 includes repeating optional operation 204 after etching at least one step 330 at each second depth 322. For example, at optional operation 204, the photoresist segment 310 is trimmed to further increase the distance 332. At optional operation 203, a third depth 326 of the plurality of depths 324 is created, along with a third leading sidewall portion 348 and a third linewidth 366 from the third leading sidewall portion 348 to the trailing sidewall 352. The third linewidth 366 is controlled by the distance between the leading edge plane 334 and the trailing edge plane 336 and is increased by subsequent optional operation 202. The distance 332 corresponds to the third linewidth 366 because the plasma etchant 304 does not contact the substrate 302 (or) beyond the distance 332. Figure 1C Component layer 103 (if it exists).

[0033] Figure 3F This is a schematic cross-sectional view of the optical element structure 300. Operations 203 and 204 are repeated until the optical element structure 300 is formed, at which point at least one step 330 has multiple depths 324, including a first depth 320 and at least one second depth 322 corresponding to the step depth. Reducing the first depth 320 and each of the second depths 322 will result in a smoother leading sidewall 344 of at least one step 330.

[0034] Figure 3IThis is a schematic cross-sectional view of the optical element structure 300 after operation 206 of method 200. In one embodiment, the patterned hard mold 306 and at least one photoresist layer 308 comprise a non-transparent material, which is removed at operation 206 after the formation of the optical element structure 300, as shown below. Figure 3I As shown. For example, the patterned hard mold 306 and at least one photoresist layer 308 comprise a reflective material, such as Cr or silver (Ag). In another embodiment, the patterned hard mold 306 and the photoresist layer 308 comprise a transparent material, such that the patterned hard mold 306 and at least one photoresist layer 308 are retained after the optical element structure 300 is formed.

[0035] After operation 206, at least step 330 retains and forms the structure of the blazed grating 106. Although Figure 3I Only three steps are illustrated, but optional operation 204 can be repeated to produce the desired number of steps, such as 5, 10, or 25. As the number of steps increases, it is worth noting that the linewidth of each step (e.g., 362, 364) may decrease, thereby producing a smoother leading sidewall portion (e.g., 342, 344) or blazing surface 108 for each blazed grating 106.

[0036] The advantage of this disclosure is that it provides a scalable method for forming blazed gratings for AR waveguides using standard lithography and etching processes. For example, method 200 enables the formation of multiple blazed gratings 106 by etching multiple stepped steps to form blazed surfaces 108 of each blazed grating 106, each of which subsequently approximates a continuous blazed profile. Blazed gratings are typically required in AR waveguides to improve diffraction efficiency.

[0037] When describing elements of this disclosure or exemplary aspects or implementations thereof, the articles “a”, “an”, “the” and “described” are intended to indicate the presence of one or more elements.

[0038] The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements besides those listed.

[0039] This article uses the term "coupling" to refer to direct or indirect coupling between two objects. For example, if object A physically touches object B and object B touches object C, then objects A and C can still be considered coupled to each other—even if objects A and C do not physically touch each other directly. For example, even if the first object never physically touches the second object, the first object may still be coupled to the second object.

[0040] Although the foregoing embodiments of this disclosure are described, other and further embodiments of this disclosure may be designed without departing from the basic scope of this disclosure, and the scope of this disclosure is defined by the appended claims.

Claims

1. A method for forming an optical element structure, the method comprising: A photoresist layer is deposited on a patterned hard mold having multiple hard mold sections disposed above a component layer or substrate. The photoresist layer is patterned to create multiple photoresist segments; Etch the element layer or the substrate to create at least one step, the at least one step forming a blazed grating; The multiple photoresist sections are horizontally trimmed; as well as Remove the multiple photoresist segments and the patterned hard mold.

2. The method of claim 1, further comprising: Before removing the plurality of photoresist segments and the patterned hard mold, the element layer or the substrate is repeatedly etched and the plurality of photoresist segments are horizontally trimmed to produce the second step of the blazed grating.

3. The method of claim 2, further comprising: Before removing the plurality of photoresist segments and the patterned hard mold, but after generating the second step of the blazed grating, the element layer or the substrate is repeatedly etched and the plurality of photoresist segments are horizontally trimmed to generate the third step of the blazed grating.

4. The method of claim 1, wherein the plurality of photoresist segments are offset from a plurality of hard mold segments of the patterned hard mold such that a portion of each of the plurality of photoresist segments directly contacts a portion of the element layer or the substrate.

5. The method of claim 1, wherein the at least one step includes a first linewidth controlled by a distance between a leading edge plane defined by a first side of a photoresist segment of the plurality of photoresist segments and a trailing edge plane defined by an exposed side of a hard mold segment of the plurality of hard mold segments.

6. The method of claim 5, wherein the at least one step further comprises a second step, the second step comprising a second linewidth controlled by the distance between a leading edge plane defined by the first side of each of the plurality of photoresist segments and the trailing edge plane after a second trimming of the plurality of photoresist segments, the second linewidth being longer than the first linewidth.

7. The method of claim 1, wherein etching the element layer or the substrate comprises: Reactive ion etching is used.

8. The method of claim 1, wherein the at least one step includes a first depth into the element layer or the substrate.

9. The method of claim 2, wherein the at least one step includes a first depth into the element layer or the substrate, and the second step includes a second depth into the element layer or the substrate, the first depth being greater than the second depth.

10. The method of claim 3, wherein the at least one step includes a first depth into the element layer or the substrate, the second step includes a second depth into the element layer or the substrate, and the third step includes a third depth into the element layer or the substrate, the first depth being greater than the second depth and the second depth being greater than the third depth.

11. A method for forming an optical element structure, the method comprising: A photoresist layer is deposited on a patterned hard mold having multiple hard mold sections disposed above a component layer or substrate. The photoresist layer is patterned to create multiple photoresist segments; Etch the element layer or the substrate to create the first step of the blazed grating; The multiple photoresist sections are horizontally trimmed; Repeated etching of the element layer or the substrate and horizontal trimming of the plurality of photoresist segments are performed to generate the second step of the blazed grating; Repeated etching of the element layer or the substrate and horizontal trimming of the plurality of photoresist segments to produce the third step of the blazed grating; as well as Remove the multiple photoresist segments and the patterned hard mold.

12. The method of claim 11, wherein the plurality of photoresist segments are offset from a plurality of hard mold segments of the patterned hard mold such that a portion of each of the plurality of photoresist segments directly contacts a portion of the element layer or the substrate.

13. The method of claim 11, wherein the first step includes a first linewidth controlled by a distance between a leading edge plane defined by a first side of a photoresist segment of the plurality of photoresist segments and a trailing edge plane defined by an exposed side of a hard mold segment of the plurality of hard mold segments.

14. The method of claim 13, wherein the second step includes a second linewidth controlled by a distance between a leading edge plane defined by the first side of one of the plurality of photoresist segments and the trailing edge plane, the second linewidth being greater than the first linewidth.

15. The method of claim 14, wherein the third step includes a third linewidth controlled by the distance between a leading edge plane and a trailing edge plane defined by the first side of the photoresist segment in the plurality of photoresist segments, the third linewidth being greater than the second linewidth.

16. A method for forming an optical element structure, the method comprising: A photoresist layer is deposited on a patterned hard mold positioned above the component layer or substrate; The photoresist layer is patterned to create multiple photoresist segments; Etch the element layer or the substrate to create a first step of the blazed grating with a first linewidth; The multiple photoresist sections are horizontally trimmed; Repeated etching of the element layer or the substrate and horizontal trimming of the plurality of photoresist segments are performed to generate a second step of the blazed grating with a second linewidth, the second linewidth being non-uniformly larger than the first linewidth; as well as Remove the multiple photoresist segments and the patterned hard mold.

17. The method of claim 16, wherein the plurality of photoresist segments are offset from a plurality of hard mold segments of the patterned hard mold such that a portion of each of the plurality of photoresist segments directly contacts a portion of the element layer or the substrate.

18. The method of claim 16, wherein the first step includes a first depth into the element layer or the substrate, and the second step includes a second depth into the element layer or the substrate, the first depth being greater than the second depth.

19. The method of claim 16, further comprising: The element layer or the substrate is repeatedly etched and the plurality of photoresist segments are horizontally trimmed to produce a third step of the blazed grating with a third linewidth, the third linewidth being non-uniformly larger than the second linewidth.

20. The method of claim 19, wherein the first step includes a first depth into the element layer or the substrate, the second step includes a second depth into the element layer or the substrate, and the third step includes a third depth into the element layer or the substrate, the first depth being greater than the second depth and the second depth being greater than the third depth.

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