Multilayer high efficiency dielectric grating with improved manufacturability

Abstract

Systems and methods are provided for multi-layer high efficiency dielectric gratings with improved manufacturability. An example of a diffraction grating-based morphology includes: a plurality of grating lines; a plurality of intermediate layers; and a substrate carrying both the plurality of grating lines and the plurality of intermediate layers; wherein one or more of the plurality of grating lines comprises a plurality of grating layers; and wherein at least two of the plurality of grating layers comprise materials of different refractive indices (RIs). The plurality of grating layers includes one or more layers having a low refractive index (RI) material and one or more layers having a high refractive index (RI) material. The plurality of intermediate layers includes a plurality of matching layers and a plurality of dielectric layers.

Description

Technical Field

[0001] Aspects of the present disclosure relate to technical solutions based on optical communication. More specifically, certain implementations of the present disclosure relate to methods and systems for implementing and utilizing multi-layer high-efficiency dielectric gratings with improved manufacturability. Background Art

[0002] The limitations and disadvantages of conventional diffraction gratings will become apparent to those skilled in the art through comparison of such a system with certain aspects of the present disclosure as set forth in the remainder of this application with reference to the figures. Summary of the invention

[0003] As more fully set forth in the claims, systems and methods are provided for multi-layer high efficiency dielectric gratings with improved manufacturability, substantially as shown in and / or described in conjunction with at least one of the figures.

[0004] These and other advantages, aspects and novel features of the present disclosure and details of illustrated embodiments thereof will be more fully understood from the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 A cross section of an example of a diffraction grating is shown.

[0006] Figure 2 An example of a reflective grating with a single propagation level is shown.

[0007] Figure 3 An example of a single-layer reflection grating-based morphology is shown.

[0008] Figure 4 is a contour plot showing performance contours for an example of a single layer reflection grating based morphology.

[0009] Figure 5 An example of a multilayer reflection grating based morphology is shown.

[0010] Figure 6 is a contour plot showing performance contours of an example of a multilayer reflection grating based morphology. DETAILED DESCRIPTION

[0011] The present disclosure is directed to diffraction gratings, and specifically to forms used therein. Specifically, implementations based on the present disclosure relate to diffraction gratings for high-energy laser systems based on spectral (grating-based) beam synthesis. In this regard, a diffraction grating is an optical component with a periodic structure that is configured to decompose (e.g., angularly disperse) incident light into several beams propagating in different directions. Diffraction gratings can have different uses. For example, diffraction gratings can be used in fiber optics, such as in optical fibers in which the diffraction grating is included in the fiber in order to optimize the optical performance of the fiber. In this regard, the diffraction grating can be used to combine multiple high-power single-frequency laser beams with slightly different wavelengths into a single high-energy output beam. As described in more detail below, enhanced diffraction gratings and grating-based forms are provided according to the technical solutions of the present disclosure.

[0012] Figure 1 A cross section of an example of a diffraction grating is shown. Figure 1 Shown in is a diffraction grating 100. The diffraction grating 100 includes a surface having a plurality of lines and spaces configured to facilitate a grating function. For example, the diffraction grating 100, and the grating function thereby, can be designed for a particular application. The diffraction grating 100 has periodic lines and spaces - that is, close, equidistant and parallel lines separated by corresponding close, equidistant and parallel spaces. Thus, the diffraction grating 100 has lines of equal size separated by spaces of equal size. Such a structure (particularly when the materials used therein are appropriately selected) can decompose incident light signals of different wavelengths in a special manner and with high efficiency. In Figure 2 Shown and referenced in Figure 2 Examples of reflective grating operations are described in more detail.

[0013] Figure 2 An example of a reflective grating with a single propagation level is shown. Figure 2 Shown in FIG. 2 is a diffraction grating 200 and grating operations performed therewith. In this regard, the diffraction grating 200 includes a surface having closely spaced, equally spaced, and parallel lines configured to decompose incident light (or an optical signal). Figure 2 An example of a reflective grating operation using a diffraction grating 200 having a single propagation order is shown in FIG. 1. In this regard, applying an input beam to the diffraction grating 200 results in a number of corresponding outputs, with the input beam hitting the diffraction grating 200 from the top side.

[0014] Specifically, Figure 2Shown in FIG. 1 is a reflection grating with an input beam and the corresponding output levels that can be achieved. The outputs are zero-order reflection (R0), zero-order transmission (T0), first-order transmission (T1), and first-order reflection (R1). For efficient operation, it is desirable that R1 contains most of the energy and minimizes the energy in all other output channels (R0, T0, and T1). One parameter that can be used to characterize the operation of a grating is the diffraction efficiency, which is defined as the energy in a particular order divided by the input energy. With the input beam normalized to 1, the value of R1 is the diffraction efficiency converted to that order.

[0015] Embodiments according to the present disclosure are directed to the morphology of diffraction gratings, and in particular, high performance diffraction gratings with improved manufacturability. In this regard, diffraction gratings for applications requiring high efficiency and large laser induced damage threshold (LIDT) may be limited by manufacturability limitations. Some designs may utilize fused silica grating lines combined with multiple dielectric layers. Performance requirements lead to morphological requirements of large duty cycles (e.g., greater than 65% duty cycles) and / or large grating line heights, which are defined as the ratio of line width to grating period. Such requirements may be challenging for photolithographic grating patterning and commonly used positive photoresists. In addition, commonly used low refractive index (RI) grating lines may limit the diffraction efficiency that can be achieved. Other designs may introduce high RI materials into the grating lines to provide improved performance and reduce the required line width. However, in such designs, the etched trenches terminate in the high RI material. This creates challenges for manufacturability since endpoint detection or etch stop layers for termination of the etching process cannot be utilized. Each grating must be carefully etched to the correct depth relying on strict process control and metrology to verify the etch depth achieved.

[0016] By using a morphology that optimizes performance while taking into account improved manufacturability, the technical solutions based on the present disclosure overcome at least some of the challenges of using such designs. In this regard, various exemplary embodiments according to the present disclosure include: an improved grating-based morphology including a multilayer grating line and an associated base layer. Specifically, examples of multilayer-based grating morphologies may include: a multilayer grating line including multiple layers, a matching layer group below the grating line, a dielectric layer group below the matching layer, and a substrate carrying the grating line and all of these layers. In addition, some existing gratings may include alternating layers of different materials and / or may even include different materials, such layers are usually very thin compared to the wavelength and perform non-optical functions (for example, to avoid crystallization of hafnium dioxide). In contrast, the multilayer structure used in the technical solutions based on the present disclosure is configured to perform an optical function, and as such can have different and unique features compared to any prior art solutions - for example, the thickness of the layer (multilayer grating line) can be equivalent to ¼ of the wavelength or thicker.

[0017] Each multilayer grating line may include: several layers of materials with different refractive indices (RI). For example, the multilayer grating line may include a minimum of three layers in an LHL arrangement of layers, where L indicates a low refractive index material (e.g., silicon dioxide (SiO2) in some embodiments disclosed herein) and H indicates a high refractive index material (e.g., hafnium dioxide (HfO2) in some embodiments disclosed herein). However, the present disclosure is not limited to such an arrangement, and any suitable arrangement may be used. In this regard, the multilayer grating line may have an L layer at the top, and more layers subsequently added, specifically by incremental HL pairs - that is, an exemplary embodiment: LHL may be the minimum arrangement, but arrangements such as LHLHL may also be used, for example.

[0018] In addition, the present disclosure is not limited to the specific materials used in the grating lines described herein, namely silicon dioxide (SiO2) and hafnium dioxide (HfO2), and any suitable material may be used. Nevertheless, predetermined criteria may be used in selecting the materials used in the different layers. For example, a commonly used material may have a refractive index (RI) that is not higher than hafnium dioxide and not lower than silicon dioxide (or alternatively, an RI that is not higher than a predetermined upper limit and not lower than a predetermined lower limit - for example, the upper limit may be 4 and the lower limit may be 1). In addition, one of the determining factors considered in selecting the materials used in the different layers in the grating lines may be the minimum difference (delta) between the two layers with respect to the refractive index (RI) of the two layers. In this regard, there must be at least some predetermined value of the minimum difference between the two layers. For example, it may be beneficial to have a minimum difference of at least 0.5 between the two layers. In this regard, it should be understood that such a minimum difference in refractive index is a non-limiting example and should not be interpreted as limiting the scope of the present disclosure. As such, a different (eg, higher or lower) minimum difference in refractive index may be used for each particular grating, such as based on determining (based on testing) that such a value has the best benefit.

[0019] The matching layer set may include one or more impedance matching dielectric layers to optimally couple the signal propagating through the grating lines to the underlying dielectric layer and to optimize the overall diffraction efficiency. The matching layer set may include multiple layers of materials of different refractive indices (RI) preferably arranged in an alternating manner - i.e., an HL-based arrangement.

[0020] The dielectric layer group may include one or more dielectric layers that provide increased reflectivity (i.e., Bragg reflectors) or increased transmittance (i.e., anti-reflection (AR) coatings). The dielectric layer group may include multiple layers of materials of different refractive indices (RI), preferably arranged in an alternating manner - i.e., an HL-based arrangement.

[0021] Embodiments incorporating diffraction grating-based morphologies according to the present disclosure may be configured for operation over various wavelength ranges.Exemplary embodiments may be configured for operation over a wavelength range of 1035 nm to 1075 nm.

[0022] The improved morphology based on the present disclosure can provide various benefits with respect to manufacturability and performance compared to any prior art solutions. These benefits can include terminating the etched trench at an etch stop boundary that provides more robust etch depth accuracy. In addition, the improved morphology can allow the use of a spectroscopic endpoint method to determine when to stop the etching process (e.g., receiving a signal when the etching process reaches an interface) and benefit from the slowing down of the process. In addition, the improved morphology can provide improved etch depth uniformity compared to timed etching that terminates within a layer of material. In addition, the inclusion of high RI materials reduces the required duty cycle of the grating lines. Finally, higher performance allows for looser morphology tolerances.

[0023] Exemplary embodiments including enhanced reflection gratings and morphologies based thereon are described in greater detail below, wherein a set of dielectric layers proximate a substrate comprises Bragg reflectors.

[0024] Figure 3 An example of a single-layer reflection grating-based morphology is shown. Figure 3 What is shown in FIG. 3 is a form 300 (or a portion thereof) based on a single-layer reflective grating. Specifically, Figure 3 Shown in FIG. 3 is a cross section showing the morphology 300 of the grating structure based on a single layer and the base layer.

[0025] like Figure 3 As shown in FIG. 3 , form 300 includes: a single layer (eg, based on silicon dioxide (SiO 2 )) grating lines 310 , a plurality of matching layers 320 , a plurality of dielectric layers 330 , and a substrate (eg, based on silicon) 340 .

[0026] Each single-layer grating line 310 comprises a single layer composed of the same material. Figure 3 In the exemplary embodiment shown in , the single layer grating lines 310 may include a single layer grating lines based on silicon dioxide (SiO2). In addition to the materials used therein, the characteristics of the grating lines may be described by specific parameters such as line height, line width, grating period, and duty cycle. In this regard, as noted above, the duty cycle is defined as the line width divided by the grating period - that is, duty cycle = line width / grating period. As such, the line width of the grating lines may be simply indicated by the duty cycle indicating the grating period.

[0027] exist Figure 3 In the portion of the form 300 shown in FIG. 1 , only three (3) grating periods are shown, but it is understood that the grating is composed of a large number of lines. For example, corresponding to a grating period of 862 nm, the form 300 may have a line density of 1160 lines / mm. In addition, Figure 3In the exemplary embodiment shown in , the single layer grating lines 310 have, for example, a duty cycle of 64%, and accordingly, at a grating period of 862 nm, the line width of the single layer grating lines 310 in the form 300 can be 551.68 nm. In addition, although the grating lines are shown as having a cross-sectional profile of a simple rectangular shape, the present disclosure is not limited to such shapes, and accordingly, other shapes can be used (if deemed appropriate) - for example, the cross-sectional profile of the line can be trapezoidal or have a curved profile, and be shaped and optimized accordingly.

[0028] The plurality of matching layers 320 comprises an impedance matching dielectric layer set that is configured (e.g., based on the selection of materials used therein) and / or arranged for optimal coupling of the grating structure (single layer of grating lines 310) to the underlying dielectric layer 330, as well as optimizing overall diffraction efficiency. In this regard, optimal coupling may require and / or be characterized in terms of electric field phase matching.

[0029] The plurality of dielectric layers 330 comprises a set of dielectric layers configured (eg, based on the selection of materials used therein) and / or arranged to provide increased reflectivity (eg, functioning as a Bragg reflector) or increased transmittance (eg, functioning as an anti-reflective (AR) coating).

[0030] To optimize performance, substrate 340 may include suitable materials and may have predetermined dimensions. Figure 3 In the exemplary embodiment shown in , the substrate 340 may include a silicon (Si)-based substrate having a diameter of 75 mm at a thickness of 6 mm. In some examples, the substrate may include (e.g., may also be made of) a material that is substantially transparent in the operating wavelength range. This may be particularly implemented, for example, when the dielectric layer 330 is configured to increase transmittance.

[0031] The plurality of matching layers 320 may include alternating layers of high refractive index (RI) and low refractive index (RI) materials. Similarly, the plurality of dielectric layers 330 may include alternating layers of low RI and high RI materials. In this regard, in some examples, different high RI and / or low RI materials (and layers including such materials) may be used. For example, in Figure 3 In the exemplary embodiment shown in , two different high RI materials, identified hereinafter as H1 and H2, may be used, and only one low RI material, identified hereinafter as L, may be used. In this regard, for example, H1 may include tantalum pentoxide (Ta2O5), H2 may include hafnium dioxide (HfO2), and L may include silicon dioxide (SiO2).

[0032] The first layer (322) of the plurality of matching layers 320 below the single layer of grating lines 310 acts as an etch stop layer. As such, where the grating lines comprise a low RI material (such as SiO2, as is the case in form 300), the etch stop layer 322 may comprise a high RI material. For example, in form 300, the etch stop layer 322 comprises an H2 material - i.e., HfO2. In addition to the etch stop layer 322, the plurality of matching layers 320 may comprise paired HL-based layers. In one embodiment, the same material is used throughout. As such, where the etch stop layer 322 comprises an H2 material, the plurality of matching layers 320 may comprise paired H2-L-based layers. For example, in Figure 3 In the exemplary embodiment shown in FIG. 1 , the plurality of matching layers 320 in form 300 include a H2-L-H2-L-H2 arrangement.

[0033] The plurality of dielectric layers 330 may include two separate subgroups: a first dielectric layer subgroup 332 and a second dielectric layer subgroup 334, each of which includes a different combination of low RI and high RI based layers. Figure 3 In the exemplary embodiment shown in FIG. 1 , the first dielectric layer subset 332 includes one or more paired H2-L based layers, while the second dielectric layer subset 334 includes one or more paired H1-L based layers. In this regard, the exact number of layers in the plurality of dielectric layers 330 as a whole, and in each of the first dielectric layer subset 332 and the second dielectric layer subset 334, may be adaptively determined, such as to optimize the performance of the multi-layer dielectric layer 330 and / or the morphology 300 as a whole. For example, in FIG. Figure 3 In the exemplary embodiment shown in , the first dielectric layer subset 332 includes three (3) pairs of H2-L based layers, while the second dielectric layer subset 334 includes twenty-seven (27) pairs of H1-L based layers.

[0034] Various aspects or parameters of at least some of the features and / or components may be adaptively selected based on the desired performance. In this regard, in some embodiments, an optimization algorithm (e.g., a least squares minimization of a merit function involving a rigorous coupled wave analysis (RCWA) calculation of, for example, diffraction efficiency) may be used to determine at least some of these aspects or parameters. For example, such an optimization algorithm may be used to determine the number and / or thickness of layers of each of the plurality of matching layers 320 and the plurality of dielectric layers 330 as a whole, and / or the thickness of each of the layers therein.

[0035] For example, in Figure 3In the exemplary embodiment shown in , based on the use of such an optimization algorithm, in the H2-L-H2-L-H2 arrangement used in the plurality of matching layers 320, the five individual layers (starting with the etch stop layer 322) may have thicknesses of 237 nm, 77 nm, 194 nm, 182 nm, and 156 nm, respectively. The thicknesses of each of the L, H1, and H2 layers used in the plurality of dielectric layers 330 may be 205.4 nm, 146.15 nm, and 157.8 nm, respectively. Additionally, while the present arrangement is illustrated as having a cross-sectional profile of a simple rectangular shape, the present disclosure is not limited to such shapes, and as such, other shapes may be used - for example, the cross-sectional profile of the line may be trapezoidal or have a curved profile, and be shaped and optimized accordingly.

[0036] Figure 4 is a contour plot showing performance contours for an example of a single layer reflection grating based morphology. Figure 4 Shown in FIG. 400 is a diagram. In this regard, FIG. 400 includes a diagram representing a single-layer reflective grating (e.g., Figure 3 Data on the performance of a morphology (minimum diffraction efficiency in % for all wavelengths λ and for both polarization components) as a function of the duty cycle of the grating lines in the morphology (y-axis) and the line height in μm (x-axis).

[0037] like Figure 4 As shown in , the graph 400 includes contours of minimum diffraction efficiency - that is, contour lines connecting data points corresponding to specific minimum diffraction efficiency values. As used herein, the minimum diffraction efficiency corresponds to the minimum value for R1 over the scanning wavelength λ and for both polarization components. The graph 400 shows the performance contours of the monolayer-based form 300 including one or more SiO2 grating lines.

[0038] Graph 400 (or specifically, the contour lines therein) can be similarly interpreted as a topographic map. As such, graph 400 exhibits a peak at approximately 64% duty cycle and 1.29 μm line height. Graph 400 indicates the range of variation of two parameters that can be tolerated in order to understand a particular performance level. For example, in order to understand 95% minimum diffraction efficiency, the two parameters must be constrained to the interior of the "95" contour line. As shown in graph 400, there is a small window / region where 97% minimum diffraction efficiency can be achieved, and 99% minimum diffraction efficiency cannot be achieved.

[0039] Figure 5 An example of a multilayer reflection grating based morphology is shown. Figure 5 What is shown in FIG. 5 is a form 500 (or a portion thereof) based on a multilayer reflective grating. Specifically, Figure 5Shown in FIG. 5 is a cross section illustrating a morphology 500 of a multi-layer based grating structure and a base layer.

[0040] like Figure 5 As shown in FIG. 5 , form 500 includes: a multilayer (e.g., based on silicon dioxide (SiO2) and HfO2) grating line 510, a plurality of matching layers 520, a plurality of dielectric layers 530, and a substrate (e.g., silicon) 540. In this regard, unless otherwise described, the components of form 500 may be similar to those in FIG. Figure 3 The key difference, however, is that form 500 includes a multi-layer based grating structure - e.g. Figure 5 The multilayer grating lines 510 are shown in FIG.

[0041] In this regard, each of the multilayer grating lines 510 includes: a plurality of layers each including different materials. Specifically, the layers used in the multilayer grating lines 510 may include materials with different refractive indices (RI). For example, the multilayer grating lines 510 may include alternating layers of high refractive index (RI) and low refractive index (RI) materials. For example, in Figure 5 In the exemplary embodiment shown in , the multilayer grating lines 510 may include: a hafnium dioxide (HfO2) layer 514 sandwiched by two silicon dioxide (SiO2) layers 512 and 516. In this way, as noted above, while there may be some existing gratings (e.g., nanolaminated gratings) that utilize alternating layers of hafnium dioxide and silicon dioxide, such layers in these gratings are very thin compared to the wavelength and perform non-optical functions (e.g., avoiding crystallization of hafnium dioxide), in contrast, in the multilayer gratings based on the present disclosure (e.g., multilayer grating lines 510), the layer thickness is equivalent to ¼ of the wavelength or thicker and performs an optical function. Nevertheless, the present disclosure is not limited to such a multilayer arrangement, and any other suitable arrangement may be used. In this regard, preferably, the top layer in the multilayer-based grating structure may include a low refractive index (RI) material (e.g., SiO2), followed by a pair of HL-based layers. Additionally, similar to single-layer grating lines, multi-layer grating lines may also be characterized by parameters such as line height, line width, grating period, and duty cycle, in addition to the materials used therein. In examples where the cross-section of the lines is not rectangular (e.g., trapezoidal or with curved sidewalls), line width and duty cycle may be defined using parameters defined at a particular height or defined as averages at different heights.

[0042] exist Figure 5In the portion of form 500 shown in FIG. 1 , only two (2) grating periods are shown, but it is understood that the grating is composed of a large number of lines. For example, similar to form 300, corresponding to a grating period of 862 nm, form 500 can have a line density of 1160 lines / mm. However, the use of a multi-layer based structure can allow for the use of a smaller duty cycle. For example, in Figure 5 In the exemplary embodiment shown in , the multilayer grating lines 510 have a duty cycle of 57%, and accordingly, at a grating period of 862 nm, the line width of the multilayer grating lines 510 in form 500 can be 491.34 nm. In addition, although the grating lines are shown as having a cross-sectional profile with a simple rectangular shape, the present disclosure is not limited to such shapes, and accordingly, other shapes can be used if deemed appropriate - for example, the cross-sectional profile of the line can be trapezoidal or have a curved profile, and be shaped and optimized accordingly.

[0043] The plurality of matching layers 520 can be substantially similar to the plurality of matching layers 320 described above, and as such similarly include a set of impedance matching dielectric layers. Similarly, the plurality of dielectric layers 530 can be substantially similar to the plurality of dielectric layers 330 described above, and as such similarly include a set of dielectric layers that provide increased reflectivity (e.g., functioning as a Bragg reflector) or increased transmittance (e.g., functioning as an anti-reflection (AR) coating). Additionally, for example, the substrate 540 can be substantially similar to the substrate 340 described above, and as such similarly can include a silicon (Si) based substrate, and can have a diameter of 75 mm at a thickness of 6 mm. In some examples, the substrate can include (e.g., can also be made from) a material that is substantially transparent in the operating wavelength range, particularly if the dielectric layers 530 are configured to increase transmittance.

[0044] The use of a multi-layer based grating structure may allow some modifications to be made to some components. For example, the number of layers used in the plurality of matching layers 520 may be reduced without affecting performance. For example, in Figure 5 In the exemplary embodiment shown in , the plurality of matching layers 520 in form 500 includes a HLH (specifically, H2-L-H2) arrangement including a top H2 layer acting as an etch stop layer 522 followed by a L-H2 layer pair.

[0045] Various aspects or parameters of at least some of the features and / or components of form 500 may be adaptively selected based on desired performance. In this regard, in some embodiments, the optimization algorithms described herein may be used to determine at least some of these aspects or parameters. For example, the optimization algorithm may be used to determine the number and / or thickness of each layer used in multi-layer grating lines 510. Figure 5In the exemplary embodiment shown in , based on the use of such an optimization algorithm, the thickness of each of the layers 512, 514 and 516 in the multi-layer grating lines 510 can be set to 211 nm, 360.7 nm and 222 nm, respectively.

[0046] As noted, the use of a grating structure based on multiple layers may improve performance compared to a grating structure based on a single layer. Figure 6 As shown in and referenced Figure 6 This is described in more detail.

[0047] Figure 6 is a contour plot showing performance contours of an example of a multilayer reflection grating based morphology. Figure 6 Shown in Figure 600 is a graph. In this regard, graph 600 includes data representing the performance of a form based on a multilayer reflection grating (e.g., form 500) (minimum diffraction efficiency in % for all wavelengths λ and for both polarization components) as a function of the duty cycle of the grating lines in the form (y-axis) and the line height in μm (x-axis).

[0048] like Figure 6 As shown in , graph 600 includes contours of minimum diffraction efficiency - that is, contour lines connecting data points corresponding to specific minimum diffraction efficiency values. As used herein, the minimum diffraction efficiency corresponds to the minimum value for R1 over the scanned wavelength λ and for both polarization components. Graph 600 shows the performance contours of the 3-layer based morphology 500. In this regard, for the data used in graph 600, only the HfO2 grating layer thickness was adjusted while the two SiO2 layers remained unchanged.

[0049] Specifically, line height adjustment can be achieved by adjusting the HfO2 layer thickness while leaving the SiO2 layer thickness unchanged. As shown by Figure 600, the use of a multilayer grating results in improved performance. In this regard, in both Figure 600 and Figure 400, the contour plots (performance maps) show "areas" of equal size (e.g., Δ duty cycle = 20% and Δ line height = 200nm). This allows for a visual comparison of the tolerances of the two designs. However, relative to Figure 400, the performance contours of Figure 600 show a larger window / area that achieves 97% minimum diffraction efficiency, and can even achieve 99% minimum diffraction efficiency.

[0050] Thus, in addition to the manufacturability improvements described above, with multilayer reflective grating-based morphologies, peaks can be higher and greater morphological variation can be tolerated for a given performance level—for example, performance contours of equal value in Figure 600 encompass one or more larger areas than in Figure 400 .

[0051] An example of a diffraction grating-based morphology according to the present disclosure includes: a plurality of grating lines; a plurality of intermediate layers; and a substrate carrying both the plurality of grating lines and the plurality of intermediate layers; wherein one or more of the plurality of grating lines include a plurality of grating layers; and wherein at least two of the plurality of grating layers include materials with different refractive indices (RI).

[0052] In an exemplary embodiment, the plurality of grating layers includes: one or more layers including a low refractive index (RI) material and one or more layers including a high refractive index (RI) material.

[0053] In an exemplary embodiment, a top layer of the plurality of grating layers comprises a low refractive index (RI) material.

[0054] In an exemplary embodiment, one or more layers including a low refractive index (RI) material and one or more layers including a high refractive index (RI) material are arranged in an alternating manner.

[0055] In an exemplary embodiment, the low refractive index (RI) material used in the plurality of grating layers includes silicon dioxide (SiO 2 ).

[0056] In an exemplary embodiment, the high refractive index (RI) material used in the plurality of grating layers includes hafnium dioxide (HfO2).

[0057] In an exemplary embodiment, the plurality of intermediate layers includes a plurality of matching layers.

[0058] In an exemplary embodiment, a first layer of the plurality of matching layers in contact with the plurality of grating lines is an etch stop layer.

[0059] In an exemplary embodiment, the etch stop layer includes a high refractive index (RI) material.

[0060] In an exemplary embodiment, the plurality of matching layers include layers of materials having different refractive indices (RI).

[0061] In an exemplary embodiment, the plurality of matching layers includes: one or more layers including a low refractive index (RI) material and one or more layers including a high refractive index (RI) material.

[0062] In an exemplary embodiment, one or more layers including a low refractive index RI material and one or more layers including a high refractive index RI material are arranged in an alternating manner.

[0063] In an exemplary embodiment, the low refractive index (RI) material used in the plurality of matching layers includes silicon dioxide (SiO 2 ).

[0064] In an exemplary embodiment, the high refractive index (RI) material used in the plurality of matching layers includes hafnium dioxide (HfO 2 ).

[0065] In an exemplary embodiment, the plurality of intermediate layers includes a plurality of dielectric layers.

[0066] In an exemplary embodiment, the plurality of dielectric layers includes layers of materials having different refractive indices (RI).

[0067] In an exemplary embodiment, the plurality of dielectric layers includes: one or more layers including a low refractive index (RI) material and one or more layers including a high refractive index (RI) material.

[0068] In an exemplary embodiment, one or more layers including a low refractive index (RI) material and one or more layers including a high refractive index (RI) material are arranged in an alternating manner.

[0069] In an exemplary embodiment, the low refractive index (RI) material used in the plurality of dielectric layers includes silicon dioxide (SiO 2 ).

[0070] In an exemplary embodiment, the one or more layers comprising a high refractive index (RI) material include: at least one first layer comprising a first high refractive index (RI) material and at least one second layer comprising a second high refractive index (RI) material, wherein the first high refractive index (RI) material and the second high refractive index (RI) material are different.

[0071] In an exemplary embodiment, the first high refractive index (RI) material includes tantalum pentoxide (Ta 2 O 5 ).

[0072] In an exemplary embodiment, the second high refractive index (RI) material includes hafnium dioxide (HfO 2 ).

[0073] In an exemplary embodiment, the substrate includes silicon (Si).

[0074] As used herein, "and / or" means any one or more of the items in the list connected by "and / or". As an example, "x and / or y" means any element in the three-element group {(x), (y), (x, y)}. In other words, "x and / or y" means "one or both of x and y". As another example, "x, y and / or z" means any element in the seven-element group {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, "x, y and / or z" means "one or more of x, y and z". As used herein, the word "exemplary" means serving as a non-limiting example, example or instance. As used herein, the words "for example" and "eg" list one or more non-limiting examples, examples or instances.

[0075] While the present method and / or system has been described with reference to a specific implementation, it will be understood by those skilled in the art that various changes may be made and may be substituted with equivalents without departing from the scope of the present method and / or system. In addition, many modifications may be made to the teachings of the present disclosure to accommodate specific circumstances or materials without departing from the scope of the present disclosure. Therefore, it is intended that the present method and / or system is not limited to the specific implementation disclosed, but rather, the present method and / or system will include all implementations that fall within the scope of the appended claims.

Claims

1. A diffraction grating-based modality comprising: multiple raster lines; Multiple intermediate layers; as well as a substrate carrying both the plurality of grating lines and the plurality of intermediate layers; wherein one or more of the plurality of grating lines comprises a plurality of grating layers; and Wherein, at least two of the multiple grating layers include materials with different refractive indexes RI.

2. The diffraction grating-based modality of claim 1, wherein: The plurality of grating layers include: one or more layers including a low refractive index RI material and one or more layers including a high refractive index RI material.

3. The diffraction grating-based modality of claim 2, wherein: The top layer of the plurality of grating layers comprises a low refractive index RI material.

4. The diffraction grating-based modality of claim 2, wherein: The one or more layers comprising low refractive index RI material and the one or more layers comprising high refractive index RI material are arranged in an alternating manner.

5. The diffraction grating-based modality of claim 2, wherein: The low refractive index RI material includes silicon dioxide SiO2.

6. The diffraction grating-based modality of claim 2, wherein: The high refractive index RI material includes hafnium dioxide HfO2.

7. The diffraction grating-based modality of claim 1, wherein: The plurality of intermediate layers include a plurality of matching layers.

8. The diffraction grating-based modality of claim 7, wherein: A first layer of the plurality of matching layers in contact with the plurality of grating lines is an etch stop layer.

9. The diffraction grating-based modality of claim 8, wherein: The etch stop layer includes a high refractive index RI material.

10. The diffraction grating-based modality of claim 7, wherein: The plurality of matching layers include layers of materials having different refractive indices RI.

11. The diffraction grating-based modality of claim 10, wherein: The plurality of matching layers include: one or more layers including a low refractive index RI material and one or more layers including a high refractive index RI material.

12. The diffraction grating-based modality of claim 11, wherein: The one or more layers comprising low refractive index RI material and the one or more layers comprising high refractive index RI material are arranged in an alternating manner.

13. The diffraction grating based modality of claim 11, wherein: The low refractive index RI material includes silicon dioxide SiO2.

14. The diffraction grating based modality of claim 11, wherein: The high refractive index RI material includes hafnium dioxide HfO2.

15. The diffraction grating based modality of claim 1, wherein: The plurality of intermediate layers include a plurality of dielectric layers.

16. The diffraction grating based modality of claim 15, wherein: The plurality of dielectric layers include layers of materials having different refractive indices RI.

17. The diffraction grating based modality of claim 16, wherein: The plurality of dielectric layers include: one or more layers including a low refractive index RI material and one or more layers including a high refractive index RI material.

18. The diffraction grating based modality of claim 17, wherein: The one or more layers comprising low refractive index RI material and the one or more layers comprising high refractive index RI material are arranged in an alternating manner.

19. The diffraction grating-based modality of claim 17, wherein: The low refractive index RI material includes silicon dioxide SiO2.

20. The diffraction grating-based modality of claim 17, wherein: The one or more layers comprising high refractive index RI material include: at least one first layer comprising a first high refractive index RI material and at least one second layer comprising a second high refractive index RI material, and wherein the first high refractive index RI material and the second high refractive index RI material are different.

21. The diffraction grating-based modality of claim 20, wherein: The first high refractive index RI material includes tantalum pentoxide Ta2O5.

22. The diffraction grating-based modality of claim 20, wherein: The second high refractive index RI material includes hafnium dioxide HfO2.

23. The diffraction grating-based modality of claim 1, wherein: The substrate includes silicon Si.

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