Reflective retardation structure

Abstract

To provide a reflective retardation structure having uniform characteristics in a wide band.SOLUTION: A reflective retardation structure 200 includes: a dielectric spacer layer 220; an anisotropic structure layer 230; and a dielectric protective layer 240. The anisotropic structure layer 230 includes a plurality of metal components 232 and a dielectric filling member 234 for filling gaps between the plurality of metal components 232. The dielectric spacer layer 220 is sandwiched between a metal reflective layer and the anisotropic structure layer 230. When the metal components 232 are viewed in cross section, letting x be a length of an upper side, y be a length of a bottom side, and w be a width at one-half height, relations of 0.6≤x / w≤1.3 and 1.8×w≤x+y≤2.2×w are satisfied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a reflective retardation structure. [Background technology]

[0002] In the field of optics, controlling the phase of light is an important technology. Wave plates such as quarter-wave plates and half-wave plates are widely used as optical components to control the phase of light.

[0003] By forming an anisotropic structure on the surface of an object by microfabrication, the function of a retardation plate can be realized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-210479 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, a reflective retardation structure has a problem in that it is difficult to obtain uniform characteristics over a wide band because the wavelength characteristics are determined by the material used.

[0006] The present disclosure has been made in view of the above-mentioned problems, and one exemplary purpose of an embodiment thereof is to provide a reflective retardation structure having uniform characteristics over a wide band. [Means for solving the problem]

[0007] A reflective phase difference structure according to an embodiment of the present disclosure includes a metal reflective layer, an anisotropic structure layer including a plurality of metal components and a dielectric filling member that fills gaps between the plurality of metal components, a dielectric spacer layer sandwiched between the metal reflective layer and the anisotropic structure layer, and a dielectric protection layer formed on the anisotropic structure layer. When the metal components are viewed in cross section, the length of the top side is x, the length of the bottom side is y, and the width at half the height is w, 0.6≦x / w≦1.3 1.8×w≦x+y≦2.2×w Satisfy the relationship.

[0008] Any combination of the above components, or mutual substitution of the components or expressions of the present disclosure between methods, devices, systems, etc., are also valid aspects of the present disclosure. [Effects of the Invention]

[0009] According to an aspect of the present disclosure, a reflective retardation structure having uniform characteristics over a wide band can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a reflective retardation structure according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the reflective retardation structure of FIG. [Figure 3] FIG. 2 is a cross-sectional view of a metal component. [Figure 4] FIG. 10 is a diagram showing the dependence of the TE reflectivity and TM reflectivity of a reflective retardation structure on the top duty ratio x / w. [Figure 5] FIG. 10 is a diagram showing the dependency of the phase difference characteristic of a reflective phase difference structure on the top duty ratio x / w. [Figure 6] FIG. 10 is a diagram showing the dependency of the phase difference characteristic of a reflective phase difference structure on the top duty ratio x / w. [Figure 7] 10A and 10B are diagrams illustrating a margin for manufacturing variations in a reflective retardation structure. [Figure 8] FIG. 10 is a perspective view of a reflective retardation structure according to Modification 1. [Figure 9] FIG. 10 is a plan view illustrating design parameters of an anisotropic structure layer according to Modification 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not an exhaustive overview of all possible embodiments, nor does it limit essential elements of the embodiments. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0012] A reflective phase difference structure according to an embodiment of the present disclosure includes a metal reflective layer, an anisotropic structure layer including a plurality of metal components and a dielectric filling member that fills gaps between the plurality of metal components, a dielectric spacer layer sandwiched between the metal reflective layer and the anisotropic structure layer, and a dielectric protection layer formed on the anisotropic structure layer. When the metal components are viewed in cross section, the length of the top side is x, the length of the bottom side is y, and the width at half the height is w, 0.6≦x / w≦1.3 1.8×w≦x+y≦2.2×w Satisfy the relationship.

[0013] In a structure in which an anisotropic structure layer is formed in contact with a metal reflective layer, i.e., a structure without a dielectric spacer layer, it is difficult to obtain uniform characteristics over a wide wavelength range. In contrast, by inserting a dielectric spacer layer between the metal reflective layer and the anisotropic structure layer and optimizing its material and thickness, it is possible to uniformize characteristics over a wide band.

[0014] The retardation structure can be evaluated based on its retardation characteristics and reflectance characteristics. Ideally, it is desirable for the retardation structure to have uniform retardation characteristics and uniform reflectance characteristics. However, depending on the application, the uniformity of one of the two characteristics may be required preferentially.

[0015] Adding a dielectric filler can reduce the dispersion of the phase difference.

[0016] Furthermore, by adding a dielectric protection layer and optimizing its thickness, the dispersion of the phase difference can be adjusted to obtain more uniform characteristics.

[0017] In this configuration, by setting x / w in the range of 0.6 to 1.3, the phase difference can be kept within the range of 180±20 degrees over a wide wavelength band.

[0018] Within the above range, the wavelength band where the phase difference is flat (180±20 degrees) is narrowest when x / w=1, and the flat wavelength band becomes wider as the value moves away from x / w=1. 0.6≦x / w≦0.8 or 1.1≦x / w≦1.3 It may also be possible to use the following.

[0019] In one embodiment, the wavelength used in the reflective retardation structure may be in the wavelength range of 400 to 1200 nm.

[0020] In one embodiment, the dielectric spacer layer and the dielectric fill member may be the same material.

[0021] In one embodiment, the dielectric fill member and the dielectric protection layer may be the same material.

[0022] In one embodiment, the material of the metal component may be an aluminum-based metal, which can provide uniform properties across a wide wavelength range in the visible range, rather than the common metasurface materials Au or Ag.

[0023] (Embodiment) Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are merely examples and do not limit the disclosure or invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure or invention.

[0024] In addition, the dimensions (thickness, length, width, etc.) of each component shown in the drawings may be enlarged or reduced as appropriate for ease of understanding. Furthermore, the dimensions of multiple components do not necessarily represent their relative sizes, and even if a component A is depicted as being thicker than another component B in the drawings, it is possible that component A is thinner than component B.

[0025] 1 is a perspective view of a reflective retardation structure 200 according to an embodiment. The reflective retardation structure 200 has a layered structure including a metal reflective layer 210, a dielectric spacer layer 220, an anisotropic structure layer 230, and a dielectric protection layer 240.

[0026] As materials for the metal reflective layer 210, Ag, Al, etc. are suitable in the visible range. When designing for near-infrared light, Au, Cu, etc. can be used. When high reflectivity is not required, Cr, Ni, Fe, etc. may also be used. The metal reflective layer 210 is formed on the surface of a substrate (not shown) or on the surface of another member that is intended to function as a retardation plate.

[0027] The anisotropic structure layer 230 has different structures in a first direction (x direction) and a second direction (y direction) that are perpendicular to each other in the plane (xy) of the reflective retardation structure 200. The anisotropic structure layer 230 includes a plurality of metal components 232. In this embodiment, the anisotropic structure layer 230 has a wire grid structure (line and space structure), and the plurality of metal components 232 are a plurality of wire grids that extend in the y direction and are adjacent in the x direction.

[0028] The material of the metal components 232 of the anisotropic structure layer 230 can be selected depending on the wavelength used in the reflective retardation structure 200 .

[0029] For example, if the reflective retardation structure 200 is to be used in the visible range, an aluminum (Al)-based metal can be used as the material. An aluminum-based metal means a metal containing at least aluminum, and can include not only pure aluminum, but also aluminum containing impurities and aluminum alloys containing aluminum as the main component. In short, an aluminum-based metal has aluminum as the main component and can contain other materials as long as they do not impair the optical properties of pure aluminum or can obtain optical properties equivalent to those of pure aluminum.

[0030] The anisotropic structural layer 230 further includes a dielectric filler member 234 that fills the spaces between the plurality of metal components 232 .

[0031] The dielectric spacer layer 220 is sandwiched between the metal reflective layer 210 and the anisotropic structure layer 230. A dielectric protection layer 240 is formed on the anisotropic structure layer 230. In other words, the reflective retardation structure 200 has a layered structure in which the metal reflective layer 210, the dielectric spacer layer 220, the anisotropic structure layer 230, and the dielectric protection layer 240 are stacked in this order.

[0032] The dielectric spacer layer 220, the dielectric filling member 234, and the dielectric protection layer 240 may be made of the same material or different materials, such as SiO2, TiO2, MgF2, Al2O3, MgO, Y2O3, HfO2, ZrO2, and Ta2O5.

[0033] Fig. 2 is a cross-sectional view of the reflective retardation structure 200 of Fig. 1. The optical characteristics of the reflective retardation structure 200 can be designed using parameters such as the thickness d1 and material of the dielectric spacer layer 220, the structure and size (height d2, line width Wl, and space width Ws) of the metal components 232 of the anisotropic structure layer 230, the material of the dielectric filling member 234, and the thickness d3 and material of the dielectric protection layer 240.

[0034] FIG. 3 is a cross-sectional view of the metal component 232. The shape of the metal component 232 is assumed to be rectangular. When the metal component 232 is viewed in cross section along the y axis, the length of the top side is defined as x, the length of the bottom side as y, and the width at half the height as w. Here, x / w is defined as the top duty ratio. The following describes the results of verifying the influence of the top duty ratio x / w on the optical characteristics of the reflective retardation structure 200 by simulation. The horizontal axis represents wavelength, and the vertical axis represents the top duty ratio x / w.

[0035] First, the design was optimized assuming use in the wavelength band of 400 to 800 nm.

[0036] 4 is a diagram showing the dependence of the TE reflectivity and TM reflectivity of the reflective retardation structure 200 on the top duty ratio x / w. In the simulation, w is fixed, and y is changed according to a change in x, assuming that the relationship 2×w=x+y holds. The cross-sectional shape of the metal component 232 is a triangle with an apex on the upper side when x / y=0, a rectangle when x / y=1, and an inverted triangle with an apex on the lower side when x / y=2.

[0037] FIG. 5 is a diagram showing the dependency of the phase difference characteristic of the reflective phase difference structure 200 on the top duty ratio x / w.

[0038] In the figure, a flatness of 180±20 degrees is ensured within the range enclosed by the rectangle. Focusing on the vertical axis of this rectangle, it can be seen that a flatness of 180±20 degrees can be ensured if the top duty ratio x / w is within the following range. 0.6≦x / w≦1.3

[0039] Here, when focusing on the contour line of a phase difference of 160 degrees, the wavelength band is narrow when x / y is around 0.8 to 1.1, and the wavelength band where flatness is ensured becomes wider as it moves away from that point. Therefore, x / y is 0.6≦x / w≦0.8 or 1.1≦x / w≦1.3 This can further improve the flatness.

[0040] In this simulation, it was assumed that 2×w=x+y holds true, but in the actual manufacturing process, depending on the etching method, processing conditions, and dimensional tolerances, the cross-sectional shape may not necessarily be a trapezoid as shown in Figure 3, and 2×w=x / w may not hold true strictly. If an error of 10% is allowed, 1.8×w≦x+y≦2.2×w It is sufficient if the following holds true.

[0041] Next, the optimal dimensional parameters (specifically, width w, height h, grid spacing, etc.) obtained assuming use in the wavelength range of 400 to 800 nm were scaled to assume use in the wavelength range of 800 to 1200 nm, and a simulation was performed.

[0042] 6 is a diagram showing the dependency of the phase difference characteristic of the reflective retardation structure 200 on the top duty ratio x / w. A flatness of 180±20 degrees is ensured within the range enclosed by the rectangle. Focusing on the vertical axis of this rectangle, it can be seen that a flatness of 180±20 degrees can be ensured if the top duty ratio x / w is within the following range: 0.6≦x / w≦1.3 This is similar to the case of an optimum design at 400 to 800 nm, which supports the idea that the optimum range of the top duty ratio can be generalized even if the operating wavelength changes.

[0043] Fig. 7 is a diagram illustrating the margin for manufacturing variations in the reflective retardation structure 200. Fig. 7 shows characteristics at wavelengths of 400 nm, 450 nm, 550 nm, 650 nm, and 700 nm, with the horizontal axis representing the top duty ratio and the vertical axis representing the reflectance and retardation. At a wavelength of 450 nm, the retardation margin for variations in the top duty ratio is largest.

[0044] Next, a modified example of the anisotropic structure layer 230 will be described.

[0045] The anisotropic structure layer 230 may have a double patterning structure in which pairs of two wire grids adjacent to each other in the x direction are repeatedly formed in the x direction.

[0046] Furthermore, the anisotropic structure layer 230 is not limited to a collection of wire grids.

[0047] 8 is a perspective view of a reflective retardation structure 200F according to Modification 1. In this modification, a plurality of metal components 232F are a collection of a plurality of blocks adjacent to each other in the x and y directions. The anisotropic structure layer 230F may include a dielectric filling member 234, and a dielectric protection layer 240 may be formed on the anisotropic structure layer 230F.

[0048] 9 is a plan view illustrating design parameters of an anisotropic structure layer 230F according to Modification 1. The anisotropic structure layer 230F has a metal component 232F having a length Δx in the x direction, a length Δy in the y direction, and a space d in the x direction. x , space d in the y direction y In order for the anisotropic structure layer 230F to be said to have an anisotropic structure, Δx≠Δy, d x ≠d y At least one of the above conditions must be satisfied. [Explanation of symbols]

[0049] 200 Reflective phase difference structure 210 Metal reflective layer 220 dielectric spacer layer 230 Anisotropic Structure Layer 232 Metallic Components 234 Dielectric filling material 240 Dielectric protection layer

Claims

1. a metal reflective layer; an anisotropic structure layer including a plurality of metal components and a dielectric filler member filling gaps between the plurality of metal components; a dielectric spacer layer sandwiched between the metal reflective layer and the anisotropic structure layer; a dielectric protection layer formed on the anisotropic structure layer; Equipped with When the metal component is viewed in cross section, the length of the upper side is defined as x, the length of the bottom side is defined as y, and the width of 1 / 2 height is defined as w, 0.6≦x / w≦1.3 1.8 x w ≤ x + y ≤ 2.2 x w A reflective phase difference structure characterized by satisfying the following relationship:

2. 2. The reflective retardation structure according to claim 1, wherein the wavelength used is within the wavelength range of 400 to 1200 nm.

3. 3. The reflective phase difference structure according to claim 1, wherein the dielectric spacer layer and the dielectric filling member are made of the same material.

4. 3. The reflective retardation structure according to claim 1, wherein the dielectric filling member and the dielectric protection layer are made of the same material.

5. 3. The reflective phase difference structure according to claim 1, wherein the material of the metal component is an aluminum-based metal.

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