Phase shift device and chromatic aberration optical device including the phase shift device

Abstract

A phase shift device and a chromatic aberration optical device including the phase shift device are provided. The phase shift device includes: a plurality of metal layers and a plurality of first dielectric layers, wherein the metal layers in the plurality of metal layers and the first dielectric layers in the plurality of first dielectric layers are alternately stacked in a first direction; and a second dielectric layer arranged on a side surface of the stacked structure in a second direction, wherein the first dielectric layer includes a first material having a first dielectric constant, the second dielectric layer includes a second material having a second dielectric constant, and wherein the second dielectric constant is greater than the first dielectric constant.

Description

Technical Field

[0001] Example embodiments of the present disclosure relate to a phase shift device, and more particularly, to a phase shift device including a metal-dielectric composite structure having a substantially constant refractive index in a wide wavelength band. Background Art

[0002] Optical devices having unique electrical and optical properties that cannot be found in nature by using an array of dielectric structures having a size smaller than the wavelength of light can be provided. For example, by using such optical properties, lenses, beam deflectors, holographic elements, etc. having very small thickness and small size can be realized.

[0003] However, an optical device having an array of dielectric structures whose size is smaller than the wavelength of light generally has wavelength dependence. Therefore, desired optical properties can be obtained only in a relatively narrow wavelength band. For example, since a lens using such optical properties has a relatively large chromatic aberration, a separate optical member for compensating for chromatic aberration is used together with the lens.

[0004] In addition, in order to manufacture such an optical device, a material having a high refractive index at the wavelength of the corresponding light is used. For example, silicon (Si) having a refractive index of at least 3.5 is mainly used in the infrared band of a wavelength of 1550nm. However, there is no single material in nature that maintains a high refractive index and a constant refractive index in the visible light or near-infrared region. Summary of the invention

[0005] One or more example embodiments provide a phase shift device including a metal-dielectric composite structure having a substantially constant refractive index in a wide wavelength band.

[0006] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of example embodiments.

[0007] According to one aspect of an example embodiment, a phase shift device is provided, comprising: a stacked structure, comprising a metal layer and a first dielectric layer, the metal layer and the first dielectric layer being alternately stacked in a first direction; and a second dielectric layer, arranged on a side surface of the stacked structure in a second direction, wherein the first dielectric layer comprises a first material having a first dielectric constant, and the second dielectric layer comprises a second material having a second dielectric constant, wherein the second dielectric constant is greater than the first dielectric constant.

[0008] The stack structure may include at least two metal layers, wherein the first dielectric layer may be disposed between two adjacent metal layers of the at least two metal layers.

[0009] The phase shift device may further include an oxide layer disposed between the side surface of the stack structure and the second dielectric layer.

[0010] A sum of a width of the stacked structure and a width of the second dielectric layer may be smaller than a wavelength of the incident light.

[0011] A sum of a width of the stacked structure and a width of the second dielectric layer may be less than 1 / 3 of a wavelength of the incident light.

[0012] The width of the stack structure may be equal to or greater than the width of the second dielectric layer.

[0013] The phase shift device may include a plurality of the stack structures and a plurality of the second dielectric layers disposed between the plurality of stack structures.

[0014] Each of the plurality of stack structures and each of the plurality of second dielectric layers may extend in a third direction, and the plurality of stack structures and the plurality of second dielectric layers may be alternately disposed in a second direction perpendicular to the first direction and the third direction, respectively.

[0015] The plurality of stack structures may include a first stack structure and a second stack structure that are different from each other in at least one of a width of a metal layer, a thickness of the metal layer, and a thickness of a first dielectric layer.

[0016] The widths of the plurality of stacked structures may gradually increase or decrease in the second direction.

[0017] The phase shift device may have a first resonance wavelength band based on surface plasmon resonance at an interface between the metal layer and the first dielectric layer and a second resonance wavelength band based on magnetic resonance between metal layers of two adjacent stacked structures, wherein the phase shift device may have a refractive index of 4 or greater in a wavelength band between the first resonance wavelength band and the second resonance wavelength band.

[0018] The phase shift device may have a refractive index difference of 0.3 or less in a wavelength band between the first resonance wavelength band and the second resonance wavelength band.

[0019] The phase shift device may include a plurality of the stack structures two-dimensionally arranged, wherein the second dielectric layer may have a lattice shape surrounding side surfaces of the plurality of stack structures.

[0020] A horizontal cross-section of each stacked structure may have one of a square shape, a rectangular shape, an elliptical shape, a triangular shape, a circular shape, a parallelogram shape, a trapezoidal shape, a rhombus shape, and a polygonal shape of at least a pentagon.

[0021] The plurality of stack structures may include a first stack structure and a second stack structure that are different from each other in at least one of a width of a metal layer, a thickness of the metal layer, and a thickness of a first dielectric layer.

[0022] The stacked structures disposed at different positions may have different widths and / or thicknesses, wherein the phase shift device may have different refractive indices based on the positions of the stacked structures in the phase shift device.

[0023] The stacked structures with different widths and / or thicknesses are arranged so that the phase shift device can be a symmetrical planar lens or an asymmetrical flat aspheric lens.

[0024] The widths of the plurality of stacked structures may gradually increase or decrease from the center of the phase shift device toward the edge of the phase shift device.

[0025] The thickness of the metal layer may range from 5 nm to 20 nm.

[0026] The thickness of the first dielectric layer may be in the range from 2.5 nm to 15 nm.

[0027] The sum of the thickness of one metal layer and the thickness of one first dielectric layer may be 30 nm or less.

[0028] The width of the stack structure may range from 30 nm to 110 nm.

[0029] The width of the second dielectric layer may be in the range from 20 nm to 50 nm, wherein the sum of the width of the stack structure and the width of the second dielectric layer may be in the range from 50 nm to 200 nm.

[0030] The first dielectric constant of the first dielectric layer may be less than 20, and the second dielectric constant of the second dielectric layer may be greater than 30.

[0031] The first dielectric layer may include SiO 2 、Al 2 O 3 、Si 3 N 4 、Na 2 SO 4 , Sr 3 (PO 4 ) 2 , YAlO 3 MgSiO 3 、YOCl、CaB 4 O 7 、Al 2 MgO 4 , Ba 2 SiO 4 , B 2 O3 Mg 4 O 3 (OH) 2 , Ba 3 P 4 O 13 , Li 3 OBr、Mg(OH) 2 , Y 2 (Si 2 O 7 )、AlLiO 2 , YOF, Ba 3 (PO 4 ) 2 , SrB 4 O 7 ,BaSO 4 and poly(methyl methacrylate).

[0032] The second dielectric layer may include TiO 2 , HfO 2 、ZrO 2 、ZnO、SrTiO 3 、GaN、GaP、BeO、NbOCl 3 ,NaNbO 3 、NaTaO 3 、AgTaO 3 , Li 4 CO 4 、CdTiO 3 , KTaO 3 , Y 2 Ti 2 O 7 、Cd 2 Ta 2 O 7 、PbHfO 3 、AlO(OH)、SrHfO 3 、Ag 2 Ta 4 O 11 、BaZrO 3 、PbZrO 3 、NaIO 3 、BiTaO 4 、HfTe 3 O 8 , K 2 W 2 O 7 and Sr 2 Ta 2 O 7 At least one of .

[0033] The metal layer may include at least one of aluminum (Al), silver (Ag), gold (Au), and copper (Cu).

[0034] According to one aspect of an example embodiment, a chromatic aberration optical device including a phase shift device is provided, wherein the phase shift device includes: a stacked structure including a metal layer and a first dielectric layer, wherein the metal layer and the first dielectric layer are alternately stacked in a vertical direction; and a second dielectric layer, which is arranged on a side surface of the stacked structure in a horizontal direction, wherein the first dielectric layer includes a material having a first dielectric constant, and the second dielectric layer includes a material having a second dielectric constant, wherein the second dielectric constant is greater than the first dielectric constant.

[0035] Chromatic optics can be configured as flat lenses or flat beam deflectors in the visible or near-infrared regions.

[0036] The first dielectric constant of the first dielectric layer may be less than 20, and the second dielectric constant of the second dielectric layer may be greater than 30. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above and / or other aspects will become apparent and more readily understood from the following description of example embodiments in conjunction with the accompanying drawings, in which:

[0038] Figure 1 is a cross-sectional view of a structure of a phase shift device according to an example embodiment;

[0039] Figure 2 yes Figure 1 A perspective view of the structure of the phase shift device shown;

[0040] Figure 3 yes Figure 1 A graph showing the refractive index characteristics of the phase shift device according to wavelength;

[0041] Figure 4 is a graph showing that when the thickness of the first dielectric layer is changed Figure 1 A graph showing changes in the refractive index characteristics of the phase shift device according to wavelength;

[0042] Figure 5 The figure shows the effect of changing the width of the metal layer and the pitch of a unit element. Figure 1 A graph showing changes in the refractive index characteristics of the phase shift device according to wavelength;

[0043] Figure 6 is a cross-sectional view of a structure of a phase shift device according to an example embodiment;

[0044] Figure 7 is a cross-sectional view of a structure of a phase shift device according to an example embodiment;

[0045] Figure 8 is a cross-sectional view of a structure of a phase shift device according to an example embodiment;

[0046] Fig. 9 is a graph showing that when the thickness of the first dielectric layer is changed Figure 8 A graph showing changes in the refractive index characteristics of the phase shift device according to wavelength;

[0047] Fig.10 and Fig.11 is a plan view of the shape of an upper surface of a phase shift device having polarization dependence according to an example embodiment;

[0048] Fig. 12A is a plan view of the shape of an upper surface of a phase shift device having a non-polarization characteristic according to an example embodiment;

[0049] Fig. 12B is a perspective view of a structure of a phase shift device having a non-polarization characteristic according to an example embodiment;

[0050] Fig.13 and Fig.14 are plan views of various forms of stacked structures according to example embodiments;

[0051] FIG. 15A to FIG. 15E is a cross-sectional view illustrating a method of manufacturing a phase shift device according to an example embodiment;

[0052] Fig.16 is a cross-sectional view of a schematic structure of a plane lens as an optical device according to an example embodiment; and

[0053] Fig.17 is a cross-sectional view of a schematic structure of a beam deflector as an optical device according to an example embodiment. DETAILED DESCRIPTION

[0054] Hereinafter, a phase shift device having a metal-dielectric composite structure will be described in detail with reference to the accompanying drawings. The same reference numerals always represent the same elements, and in the accompanying drawings, the sizes of the elements may be exaggerated for clarity and convenience of explanation. The example embodiments described below are merely examples, and various modifications may be made from these embodiments.

[0055] In the layer structure described below, expressions such as "on..." or "on..." may include not only the meaning of "directly on / below / left / right of..." in a contacting manner, but also the meaning of "on / below / left / right of..." in a non-contacting manner. Expressions such as "at least one of..." when preceding a column of elements modify the entire column of elements rather than modifying individual elements of the column. For example, the expression "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. It will also be understood that the terms "include" and / or "comprising" used herein specify the presence of the features or elements, but do not exclude the presence or addition of one or more other features or elements.

[0056] Figure 1 is a cross-sectional view of a structure of a phase shift device according to an example embodiment, Figure 2 yes Figure 1 A perspective view of the structure of the phase shift device is shown in FIG. Figure 1 and Figure 2 According to an example embodiment, a phase shift device 100 may include: a stacked structure 110, in which a first dielectric layer 102 and a metal layer 103 are alternately stacked in a vertical direction; and a second dielectric layer 120, which is disposed adjacent to a side surface of the stacked structure 110 in a horizontal direction. The phase shift device 100 may also include a transparent substrate 101, and the stacked structure 110 and the second dielectric layer 120 may both be disposed on an upper surface of the transparent substrate 101. For example, the transparent substrate 101 may include glass, quartz, fused silica, or amorphous sapphire (Al 2 O 3 ).

[0057] The stacked structure 110 may include a plurality of first dielectric layers 102 and a plurality of metal layers 103 alternately stacked on a transparent substrate 101 in a vertical direction. For example, the stacked structure 110 may include at least two metal layers 103. The metal layer 103 may have a relatively small thickness so that light may be transmitted. For example, the thickness hm of the metal layer 103 may be in the range from about 5 nm to about 20 nm. In addition, the plurality of metal layers 103 may be separated from each other at regular intervals by the first dielectric layer 102. The distance between two adjacent metal layers 103 may be adjusted by the thickness hd of the first dielectric layer 102 between the two adjacent metal layers 103. For example, the first dielectric layer 102 may have a thickness of about 2.5 nm to about 15 nm.

[0058] In addition, the plurality of first dielectric layers 102 may be directly disposed on the lower surface and the upper surface of the plurality of metal layers 103. For example, the first dielectric layer 102 may be first disposed on the transparent substrate 101, and the metal layer 103 may be disposed on the first dielectric layer 102. Finally, after the first dielectric layer 102 and the metal layer 103 are alternately disposed, the first dielectric layer 102 may be disposed on the metal layer 103.

[0059] The phase shift device 100 may include a plurality of stacked structures 110 and a plurality of second dielectric layers 120 that are alternately arranged. For example, the plurality of stacked structures 110 and the plurality of second dielectric layers 120 may be alternately arranged on the surface of the transparent substrate 101 in a horizontal direction. Therefore, the direction in which the plurality of stacked structures 110 and the plurality of second dielectric layers 120 are arranged may be perpendicular to the direction in which the plurality of first dielectric layers 102 and the plurality of metal layers 103 are stacked. Figure 1 Only two stacked structures 110 and two second dielectric layers 120 are shown in FIG. 1 , but according to example embodiments, a very large number of stacked structures 110 and second dielectric layers 120 may be arranged one-dimensionally or two-dimensionally. The gap between two adjacent stacked structures 110 may be adjusted by the width Wd of the second dielectric layer 120.

[0060] One stacked structure 110 and one second dielectric layer 120 adjacent to the side surface of the stacked structure 110 constitute one unit element of the phase shift device 100. The pitch P or period of the unit element (that is, the sum of the width Wm of the stacked structure 110 and the width Wd of the second dielectric layer 120) may be smaller than the wavelength of the incident light to obtain a special optical effect. In more detail, the pitch P of the unit element may be smaller than the wavelength band in which the phase shift device 100 mainly operates. For example, the pitch P of the unit element may be smaller than 1 / 2 or 1 / 3 of the wavelength of the incident light.

[0061] According to example embodiments, localized surface plasmon resonance may occur as an electric resonance at the upper and lower surfaces of each metal layer 103. Surface plasmon resonance is a phenomenon in which, when light is incident on the surface of a metal, a very high electric field occurs locally on the surface of the metal due to the collective oscillation of free electrons in the metal. Surface plasmon resonance generally occurs at the interface between a metal and a dielectric. In order to cause surface plasmon resonance, the metal layer 103 may use a metal material that is more likely to cause surface plasmon resonance and has less light loss at a relatively small thickness. For example, the metal layer 103 may include at least one of aluminum (Al), silver (Ag), gold (Au), and copper (Cu).

[0062] The light transmitted through the phase shift device 100 repeatedly passes through the plurality of metal layers 103 to induce surface plasmon resonance. In this process, the phase shift device 100 may have a relatively high refractive index with respect to the light corresponding to the resonance wavelength band of the surface plasmon resonance. The resonance wavelength band may vary depending on various factors, such as the thickness hm of each metal layer 103, the gap between two adjacent metal layers 103 or the thickness hd of each first dielectric layer 102, the width of each metal layer 103 or the width of the first dielectric layer 102 (i.e., Wm), the number of metal layers 103, the material of the metal layer 103, the material of the first dielectric layer 102, etc.

[0063] When the sum of the thickness hd of each first dielectric layer 102 and the thickness hm of each metal layer 103 is small, light can induce more surface plasmon resonances in a short path when passing through the phase shift device 100. For example, the sum of the thickness hd of one first dielectric layer 102 and the thickness hm of one metal layer 103 may be 30 nm or less.

[0064] In addition, the first dielectric layer 102 can more effectively induce surface plasmon resonance on the surface of the metal layer 103, and a dielectric material that transmits in the wavelength band of the incident light can be used. As described above, the surface plasmon resonance occurs at the interface between the metal layer and the dielectric layer. Generally, the smaller the dielectric constant of the dielectric layer in contact with the metal layer, the more the surface plasmon resonance occurs. For example, the first dielectric layer 102 may include a low-k dielectric material having a dielectric constant of less than 20. For example, the first dielectric layer 102 may include SiO 2 、Al 2 O 3 、Si 3 N 4 、Na 2 SO 4 , Sr 3 (PO 4 ) 2 , YAlO 3 MgSiO 3 、YOCl、CaB 4 O 7 、Al 2 MgO 4 , Ba 2 SiO 4 , B 2 O 3 Mg 4 O 3 (OH) 2 , Ba 3 P 4 O 13 , Li 3OBr、Mg(OH) 2 , Y 2 (Si 2 O 7 )、AlLiO 2 , YOF, Ba 3 (PO 4 ) 2 , SrB 4 O 7 ,BaSO 4 and poly(methyl methacrylate).

[0065] In addition, when light passes through the metal layer 103, electron accumulation occurs, wherein free electrons excited by light in the metal layer 103 accumulate on both edges of the metal layer 103 that are in contact with the second dielectric layer 120. Then, as Figure 1 As shown by the arrows in , a magnetic field may be formed between electrons accumulated at the edge of the metal layer 103 in the first unit element and electrons accumulated at the edge of the metal layer 103 in the second unit element adjacent to the first unit element, and magnetic resonance may occur. For example, magnetic resonance occurs between the right edge of one metal layer 103 of the first unit element and the left edge of the metal layer 103 in the second unit element adjacent to the metal layer 103 of the first unit element at the same height.

[0066] The light passing through the phase shift device 100 may repeatedly undergo multiple magnetic resonances, so that the phase shift device 100 has a relatively high refractive index relative to the light corresponding to the resonance wavelength band of the magnetic resonance. When the second dielectric layer 120 has a higher dielectric constant, free electrons may be more easily accumulated at the interface between the metal layer 103 and the second dielectric layer 120 to increase the magnetic resonance effect. For example, the second dielectric layer 120 may include a high-k dielectric material having a dielectric constant greater than 30. For example, the second dielectric layer 120 may include TiO 2 , HfO 2 、ZrO 2 、ZnO、SrTiO 3 、GaN、GaP、BeO、NbOCl 3 ,NaNbO 3 、NaTaO 3 、AgTaO 3 , Li 4 CO 4 、CdTiO 3 , KTaO 3 , Y 2 Ti 2 O 7 、Cd 2 Ta 2 O 7、PbHfO 3 、AlO(OH)、SrHfO 3 、Ag 2 Ta 4 O 11 、BaZrO 3 、PbZrO 3 、NaIO 3 、BiTaO 4 、HfTe 3 O 8 , K 2 W 2 O 7 and Sr 2 Ta 2 O 7 At least one of .

[0067] In addition, when the width Wd of the second dielectric layer 120 is too large, the gap between the electrons accumulated in one edge of the metal layer 103 in one unit element and the electrons accumulated in one edge of the metal layer 103 in another unit element adjacent to the one unit element will further widen, and the magnetic resonance effect will be reduced. Therefore, in order to obtain a sufficient magnetic resonance effect, the maximum width of the second dielectric layer 120 may be equal to or less than the width Wm of the stacked structure 110. In other words, the width Wm of the stacked structure 110 or the width of the metal layer 103 may be equal to or greater than the width Wd of the second dielectric layer 120. For example, the width Wm of the stacked structure 110 may be from about 30nm to about 110nm. The width Wd of the second dielectric layer 120 may be, for example, about 20nm to about 50nm. In addition, as described above, the width or pitch P of one unit element of the phase shift device 100 is less than the wavelength band in which the phase shift device 100 mainly operates. For example, the sum of the width Wm of the stack structure 110 and the width Wd of the second dielectric layer 120 may be about 50 nm to about 200 nm.

[0068] As described above, the phase shift device 100 according to the example embodiment has a first resonance wavelength band caused by surface plasmon resonance, which is an electric resonance at the interface between the metal layer 103 and the first dielectric layer 102, and a second resonance wavelength band caused by magnetic resonance between adjacent metal layers 103 in two adjacent stacked structures 110. The phase shift device 100 has a relatively high refractive index with respect to light in the first resonance wavelength band and light in the second resonance wavelength band. According to an example embodiment, the first resonance wavelength band is smaller than the second resonance wavelength band. Thus, in the wavelength band between the first resonance wavelength band and the second resonance wavelength band, the phase shift device 100 can maintain a relatively high refractive index unchanged. For example, in the wavelength band between the first resonance wavelength band and the second resonance wavelength band, the phase shift device 100 can maintain a refractive index of about 4 or more at a constant level.

[0069] For example, Figure 3 yes Figure 1 FIG. 1 is a graph showing the refractive index characteristics of the phase shift device 100 according to wavelength. Figure 3 , electric resonance occurs in a wavelength band of about 400 nm to about 600 nm (that is, a first resonance wavelength band), and forms a first peak of a refractive index of about 5 at a wavelength of about 500 nm. Magnetic resonance occurs in a wavelength band of about 1000 nm to about 1300 nm (that is, a second resonance wavelength band), and forms a second peak of a refractive index of about 5 at a wavelength of about 1130 nm. In the red visible light and near-infrared region between about 600 nm and about 1000 nm between the first resonance wavelength band and the second resonance wavelength band, the refractive index of about 4 may be maintained substantially unchanged.

[0070] Therefore, the phase shift device 100 according to the example embodiment can have a relatively high refractive index and a constant refractive index over a relatively wide wavelength band. Specifically, the phase shift device 100 can achieve a relatively high refractive index and a constant refractive index in the visible light or near infrared region. Therefore, by using the phase shift device 100 according to the example embodiment, an optical device that can operate in a visible light band or a near infrared band and has a relatively small chromatic aberration can be realized.

[0071] As described above, the wavelength band in which a relatively high refractive index of about 4 or more can be maintained is a wavelength band between the first resonance wavelength band and the second resonance wavelength band. The first resonance wavelength band can be determined according to various factors, such as the thickness hm of each metal layer 103, the gap between two adjacent metal layers 103 or the thickness hd of each first dielectric layer 102, the width of each metal layer 103 or the width of the first dielectric layer 102 (i.e., Wm), the number of metal layers 103, the material of the metal layer 103, the material of the first dielectric layer 102, and the like. In addition, the second resonance wavelength band can be determined according to various factors, such as the thickness hm of each metal layer 103, the width Wm of each stacked structure 110 or the width Wm of each metal layer 103, the width Wd of the second dielectric layer 120, the pitch P of one unit element, the number of metal layers 103, the material of the metal layer 103, the material of the second dielectric layer 120, and the like. Therefore, by adjusting the above factors, the optical characteristics of the phase shift device 100, such as the wavelength band at which a high refractive index can be maintained and the value of the refractive index, can be determined.

[0072] Figure 4 is a graph showing that when the thickness hd of the first dielectric layer 102 is changed Figure 1 FIG. 1 is a graph showing a change in the refractive index characteristic of the phase shift device 100 according to wavelength. Figure 4 In the example of , three metal layers 103 are used, Ag is used as the material of the metal layer 103, and the thickness of the metal layer 103 is fixed to 15 nm. In addition, in a state where the width (i.e., Wm) of the metal layer 103 is fixed to 30 nm and the pitch P of one unit element is fixed to 50 nm, the thickness hd of the first dielectric layer 102 varies between 5 nm, 10 nm, and 15 nm. In addition, SiO 2 The material used for the first dielectric layer 102 is HfO 2 The material used for the second dielectric layer 120 is shown in FIG. Figure 4 It can be seen from the graph that in the wavelength band from 400 nm to 750 nm, as the thickness of the first dielectric layer 102 decreases, the refractive index of the phase shift device 100 increases.

[0073] Figure 5 The figure shows the change in the width (ie, Wm) of the metal layer 103 and the pitch P of a unit element. Figure 1 FIG. 1 is a graph showing a change in the refractive index characteristic of the phase shift device 100 according to wavelength. Figure 5 In the example, three metal layers 103 are used, Ag is used as the material of the metal layer 103, SiO 2 The material used for the first dielectric layer 102 is HfO 210 nm, and the thickness hd of the first dielectric layer 102 is fixed at 5 nm and the thickness hm of the metal layer 103 is fixed at 10 nm. The width (i.e., Wm) of the metal layer 103 is varied between 30 nm, 40 nm, and 50 nm, and the pitch P of one unit element is varied between 50 nm, 60 nm, and 70 nm. Figure 5 It can be seen from the curve graph that in the wavelength band from 400 nm to 750 nm, the refractive index of the phase shift device 100 generally increases as the width (ie, Wm) of the metal layer 103 increases.

[0074] exist Figure 1 In the illustrated exemplary embodiment, each stacked structure 110 includes three metal layers 103 and four first dielectric layers 102, and the lowermost layer and the uppermost layer of the stacked structure 110 are the first dielectric layers 102. However, this is merely an example, and the structure of the stacked structure 110 is not limited thereto. The number of first dielectric layers 102, the number of metal layers 103, and the stacking order of the first dielectric layers 102 and the metal layers 103 may vary according to the optical properties required by the phase shift device 100.

[0075] For example, Figure 6 is a cross-sectional view of a structure of a phase shift device according to an exemplary embodiment. Figure 6 , the phase shift device 200 may include: a stacked structure 210, in which a metal layer 103 and a first dielectric layer 102 are alternately stacked in a vertical direction; and a second dielectric layer 120, which is disposed adjacent to a side surface of the stacked structure 210 in a horizontal direction. The stacked structure 210 may include a metal layer 103 and a first dielectric layer 102 alternately stacked on an upper surface of a transparent substrate 101 in a vertical direction. For example, the metal layer 103 may be first disposed on an upper surface of the transparent substrate 101, and the first dielectric layer 102 may be disposed on the metal layer 103. The first dielectric layer 102 may be disposed at a top layer of the stacked structure 210.

[0076] also, Figure 7 is a cross-sectional view of a structure of a phase shift device according to an exemplary embodiment. Figure 7 The phase shift device 300 may include: a stack structure 310, in which metal layers 103 and first dielectric layers 102 are alternately stacked in a vertical direction; and a second dielectric layer 120 disposed adjacent to a side surface of the stack structure 310 in a horizontal direction. Figure 7 The structure of the stacked structure 310 shown in FIG. Figure 6 The structure of the stacked structure 210 shown in FIG. 2 is substantially similar. Figure 7 In the example embodiment shown, the metal layer 103 is disposed at the top of the stack structure 310 .

[0077] Figure 8 is a cross-sectional view of a structure of a phase shift device according to an exemplary embodiment. Figure 8 , the phase shift device 400 may include: a stacking structure 110, in which the metal layer 103 and the first dielectric layer 102 are alternately stacked in the vertical direction; and the second dielectric layer 120 is arranged adjacent to the side surface of the stacking structure 310 in the horizontal direction, and the oxide layer 104 is arranged between the side surface of the stacking structure 110 and the second dielectric layer 120 in the horizontal direction. Figure 8 The stacked structure 110 shown in FIG. Figure 1 The stacked structure 110 shown in FIG. 1 is substantially the same. However, in Figure 8 In the embodiment, the stacked structure 110 can be used Figure 6 The stacked structure 210 shown in Figure 7 The stacked structure 310 shown in FIG.

[0078] The oxide layer 104 may have a width Wo of about 3 nm or less, and extend in a vertical direction along an interface between the stack structure 110 and the second dielectric layer 120 . Figure 8 The oxide layer 104 is shown to be uniformly disposed along the interface between the stack structure 110 and the second dielectric layer 120. However, example embodiments are not limited thereto, and the oxide layer 104 may be disposed only at the interface between the metal layer 103 and the second dielectric layer 120, and may be only partially disposed or not disposed at the interface between the first dielectric layer 102 and the second dielectric layer 120. The oxide layer 104 may include, for example, an oxide of a metal material of the metal layer 103.

[0079] Fig. 9 is a graph showing that when the thickness hd of the first dielectric layer 102 is changed Figure 8 FIG. 4 is a graph showing a change in the refractive index characteristic of the phase shift device 400 according to wavelength. Fig. 9 In the example of , two metal layers 103 and two first dielectric layers 102 are used, Al is used as the material of the metal layer 103, and the thickness of the metal layer 103 is fixed to 10 nm. In addition, in a state where the width Wm of the metal layer 103 is fixed to 110 nm and the pitch P of one unit element is fixed to 150 nm, the thickness hd of the first dielectric layer 102 varies between 5 nm, 10 nm, and 15 nm. Fig. 9 The “tot” in FIG. 1 represents the total thickness of the stacked structure 110. 2 MgO 4 The material used for the first dielectric layer 102 is HfO 2 The material used as the second dielectric layer 120. The width Wo of the oxide layer 104 formed of aluminum oxide is about 2.5 nm. Fig. 9, it can be seen that in the wavelength band of 600nm to 900nm, the refractive index of the phase shift device 100 generally increases as the thickness of the first dielectric layer 102 decreases. Specifically, it can be seen that when the thickness hd of the first dielectric layer 102 is 5nm and 10nm, in the wavelength band of 650nm to 1000nm, the refractive index of 4 or more is maintained unchanged. In addition, when the thickness hd of the first dielectric layer 102 is fixed, the refractive index difference in the wavelength band of 650nm to 1000nm can be about 0.3 or less. Therefore, the phase shift device can have a refractive index difference of about 0.3 or less in the wavelength band between the first resonance wavelength band and the second resonance wavelength band.

[0080] According to example embodiments, the shapes of the stacked structure 110 and the second dielectric layer 120 in the above-described phase shift devices 100, 200, 300, and 400 may vary according to the optical characteristics required of the phase shift devices 100, 200, 300, and 400. For example, Fig.10 and Fig.11 is a plan view of a shape of an upper surface of a phase shift device having polarization dependence according to example embodiments.

[0081] Reference Fig.10 , the stacked structure 110 and the second dielectric layer 120 may be longer in the Y-axis direction than in the X-axis direction. In this example, it can be seen that the stacked structure 110 having a rod shape extending in the Y-axis direction and the second dielectric layer 120 having a rod shape extending in the Y-axis direction are alternately arranged in the X-axis direction. Thus, the phase shift device can transmit light of a linear polarization component in the Y-axis direction.

[0082] Reference Fig.11 , the stacked structure 110 and the second dielectric layer 120 may be longer in the X-axis direction than in the Y-axis direction. In this example, it can be seen that the stacked structure 110 having a rod shape extending in the X-axis direction and the second dielectric layer 120 having a rod shape extending in the X-axis direction are alternately arranged in the Y-axis direction. Thus, the phase shift device can transmit light of a linear polarization component in the X-axis direction.

[0083] also, Fig. 12A is a plan view of the shape of the upper surface of the phase shift device having non-polarization characteristics, Fig. 12B is a perspective view of a structure of a phase shift device having a non-polarization characteristic according to an example embodiment. Fig. 12A and Fig. 12B The phase shift device includes a plurality of stacked structures 110 two-dimensionally arranged in the X-axis and Y-axis directions, and the second dielectric layer 120 may have a lattice shape surrounding all sides of the plurality of stacked structures 110. In this example, the phase shift device may transmit light of all polarization components.

[0084] Fig. 12A and Fig. 12B Each stacked structure 110 is shown to have a square shape, but the shape of the stacked structure 110 may vary. For example, Fig.13 and Fig.14 1 is a plan view showing various forms of stacked structures 110. Fig.13 As shown, the stacked structure 110 may have a circular shape arranged two-dimensionally. Fig.14 As shown, the stack structure 110 may have a hexagonal shape arranged two-dimensionally. In addition, the stack structure 110 may have one of an elliptical shape, a triangular shape, a rectangular shape, a parallelogram shape, a trapezoidal shape, a rhombus shape, and a polygonal shape of at least a pentagon.

[0085] Although it has been about Figure 1 The shape of the stacked structure 110 depicts Figures 10 to 14 , but about Figures 10 to 14 The same description can also be applied to Figure 6 and Figure 7 The stacked structures 210 and 310 are shown in FIG.

[0086] FIG. 15A to FIG. 15E is a cross-sectional view illustrating a method of manufacturing the phase shift device 100 according to an example embodiment.

[0087] First, refer to Fig.15A , the first dielectric layer 102 and the metal layer 103 are alternately stacked on the upper surface of the transparent substrate 101. Fig.15A In the embodiment, the first dielectric layer 102 is first stacked, the metal layer 103 is stacked on the first dielectric layer 102, and the first dielectric layer 102 is located on the top. Figure 6 and Figure 7 As shown, the order of stacking the first dielectric layer 102 and the metal layer 103 and the number of the first dielectric layer 102 and the metal layer 103 may vary. Thereafter, a mask layer 140 is stacked on top of the first dielectric layer 102 to cover the entire surface of the first dielectric layer 102 .

[0088] Next, refer to Fig. 15B For example, the mask layer 140 is patterned by a photolithography process to form a patterned mask 141. The shape of the patterned mask 141 may be similar to Figures 10 to 14 The pattern shape of the stacked structure 110 shown in FIG. 1 is the same as that of the stacked structure 110 shown in FIG. 1 . The portion of the first dielectric layer 102 exposed to the outside between the patterned masks 141 may be the same as that of the first dielectric layer 102. Figures 10 to 14 The pattern shape of the second dielectric layer 120 shown in FIG. 1 is the same.

[0089] Afterwards, refer to Fig. 15C, the multiple portions of the first dielectric layer 102 exposed to the outside between the patterned masks 141 and the portions of the multiple metal layers 103 thereunder are removed by etching in a vertical direction, so that the transparent substrate 101 is exposed to the outside. When the transparent substrate 101 is exposed to the outside, the etching process is stopped and the etchant is cleaned. Then, the patterned masks 141 are removed. Thus, the multiple stacked structures 110 are formed, and the multiple grooves 142 are formed between the multiple stacked structures 110.

[0090] Reference Fig.15D , the second dielectric layer material 121 is filled in the groove 142. For example, the second dielectric layer material 121 may be filled in all of the plurality of grooves 142 and cover all upper surfaces of the plurality of stacked structures 110. Thus, the second dielectric layer 120 may be formed between the plurality of stacked structures 110. This process may be completed without removing the second dielectric layer material 121 on the upper surface of the stacked structure 110. The phase shift device 100 may then include the second dielectric layer 120 extending to the upper surface of the stacked structure 110.

[0091] Finally, refer to Fig.15E , the second dielectric layer material 121 on the upper surface of the stacked structure 110 can be removed using a planarization process such as chemical mechanical polishing (CMP). Then, the upper surface of the stacked structure 110 is exposed to the outside, and the upper surface of the stacked structure 110 and the upper surface of the second dielectric layer 120 can be coplanar.

[0092] As described above, the refractive index of the phase shift devices 100, 200, 300, and 400 according to example embodiments may vary depending on various factors, such as the thickness hm of the metal layer 103, the gap between two adjacent metal layers 103 or the thickness hd of each first dielectric layer 102, the width of each metal layer 103 or the width of each first dielectric layer 102 (i.e., Wm), the number of metal layers 103, the material of the metal layer 103, the material of the first dielectric layer 102, the pitch P of one unit element, the material of the second dielectric layer 120, etc. Therefore, by changing these factors according to each region of the phase shift devices 100, 200, 300, and 400, the phase shift devices 100, 200, 300, and 400 having a specific refractive index distribution may be manufactured. When the refractive index locally changes according to each region of the phase shift device 100, 200, 300, and 400, the phase of light passing through the phase shift device 100, 200, 300, and 400 may locally change. The phase shift device 100, 200, 300, and 400 may be used as an optical device performing a specific optical function.

[0093] For example, by using the phase shift devices 100, 200, 300, and 400, it is possible to collect incident light, scatter or reflect incident light in a specific direction, change the traveling direction of incident light, or transmit or reflect only light of a specific wavelength among incident light. Specifically, since the phase shift devices 100, 200, 300, and 400 according to the example embodiments have a high refractive index in the visible light or near-infrared wavelength band and maintain a constant refractive index over a relatively wide bandwidth, an optical device can be realized that can operate in the visible light band or the near-infrared band and has relatively small chromatic aberration when the phase shift devices 100, 200, 300, and 400 are used. For example, a lens device, a beam shaping device, a beam deflector, a beam steering device, a holographic device, etc. having an achromatic characteristic that maintains uniform optical performance in a wide bandwidth can be realized. The operating characteristics of such an optical device can be determined according to the refractive index distribution of the phase shift devices 100, 200, 300, and 400.

[0094] For example, Fig.16 is a cross-sectional view of a schematic structure of a planar lens as an optical device according to an exemplary embodiment. Fig.16 The flat lens 500 includes a plurality of stacked structures 110 and a plurality of second dielectric layers 120 alternately disposed on a transparent substrate 101. Fig.16 As shown, the width of the stacked structure 110 is the smallest at the center of the planar lens 500, and the width of the multiple stacked structures 110 can be gradually increased symmetrically or asymmetrically toward the edge of the planar lens 500. For example, the width distribution of the stacked structure 110 can have a distribution of a radially symmetrical shape. Thus, the planar lens 500 becomes a symmetrical planar lens. In addition, the width of the multiple stacked structures 110 can be gradually increased asymmetrically. In this case, the planar lens 500 can be an asymmetric flat aspheric lens. The width of the second dielectric layer 120 can be the same in all regions of the planar lens 500. The planar lens 500 can have a relatively low chromatic aberration in the visible light or near-infrared region.

[0095] Fig.16 The width of the stacked structure 110 is shown to be the smallest at the center of the planar lens 500, and the widths of the plurality of stacked structures 110 gradually increase symmetrically or asymmetrically toward the edge of the planar lens 500. However, in some other embodiments, for example, the width of the stacked structure 110 is the largest at the center of the planar lens 500, and the widths of the plurality of stacked structures 110 may gradually decrease symmetrically or asymmetrically toward the edge of the planar lens 500. In addition, although Fig.16Only the width of the stacked structure 110 is shown to be changed, but other factors may be changed. For example, the flat lens 500 may include a plurality of stacked structures 110 that are different from each other in at least one of the width of the metal layer, the thickness of the metal layer, and the thickness of the first dielectric layer.

[0096] Fig.17 is a cross-sectional view of a schematic structure of a beam deflector according to an example embodiment. Fig.17 The beam deflector 600 includes a plurality of stacked structures 110 and a plurality of second dielectric layers 120 alternately disposed on a substrate 101. Fig.17 As shown, the width of the plurality of stacked structures 110 may gradually increase or decrease in one direction. For example, the width of the plurality of stacked structures 110 may gradually increase or decrease from left to right. Each stacked structure 110 and each second dielectric layer 120 may have a rod shape extending in one direction. The width of the second dielectric layer 120 may be the same in all regions of the beam deflector 600. The beam deflector 600 may uniformly deflect light of most wavelengths in the visible light or near infrared region at a constant angle.

[0097] In addition, despite Fig.17 Only the width of the stacked structure 110 is shown to be changed, but other factors may be changed. For example, the beam deflector 600 may include the plurality of stacked structures 110 that differ from each other in at least one of the thickness of the first dielectric layer 102 , the thickness of the metal layer 103 , and the total thickness of the stacked structure 110 .

[0098] Although the phase shift device having the above metal-dielectric composite structure has been described with reference to the example embodiments shown in the drawings, they are only examples. Descriptions of features or aspects within each example embodiment should generally be considered applicable to other similar features or aspects in other embodiments.

[0099] Although example embodiments have been described with reference to the accompanying drawings, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope defined by the claims.

[0100] This application claims the priority of Korean Patent Application No. 10-2018-0163314 filed on December 17, 2018 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A phase shift device, comprising a plurality of unit elements, wherein the plurality of unit elements are arranged one-dimensionally or two-dimensionally to form an array structure, each unit element comprising: A stacked structure, comprising a metal layer and a first dielectric layer, wherein the metal layer and the first dielectric layer are alternately stacked in a first direction; and A second dielectric layer is arranged on a side surface of the stacked structure in a second direction, wherein the first dielectric layer comprises a first material having a first dielectric constant, and the second dielectric layer comprises a second material having a second dielectric constant, wherein the second dielectric constant is greater than the first dielectric constant, and The phase shift device further includes an oxide layer disposed between the side surface of the stack structure and the second dielectric layer.

2. The phase shift device according to claim 1, wherein the stacked structure comprises at least two metal layers, and The first dielectric layer is disposed between two adjacent metal layers among the at least two metal layers. 3 . The phase shift device according to claim 1 , wherein a sum of a width of the stacked structure and a width of the second dielectric layer is smaller than a wavelength of incident light. 4 . The phase shift device according to claim 1 , wherein a sum of a width of the stacked structure and a width of the second dielectric layer is less than 1 / 3 of a wavelength of incident light. 5 . The phase shift device according to claim 1 , wherein a width of the stacked structure is equal to or greater than a width of the second dielectric layer.

6. The phase shift device according to claim 1, comprising: A plurality of the stacked structures and a plurality of the second dielectric layers disposed between the plurality of the stacked structures.

7. The phase shift device according to claim 6, wherein each of the plurality of stacked structures and each of the plurality of second dielectric layers extend in a third direction, and the plurality of stacked structures and the plurality of second dielectric layers are alternately arranged in the second direction perpendicular to the first direction and the third direction, respectively. 8 . The phase shift device according to claim 6 , wherein the plurality of stack structures include a first stack structure and a second stack structure that are different from each other in at least one of a width of the metal layer, a thickness of the metal layer, and a thickness of the first dielectric layer. 9 . The phase shift device according to claim 6 , wherein widths of the plurality of stacked structures gradually increase or decrease in the second direction.

10. The phase shift device according to claim 6, wherein the phase shift device has a first resonance wavelength band based on surface plasmon resonance at an interface between the metal layer and the first dielectric layer and a second resonance wavelength band based on magnetic resonance between two adjacent stacked metal layers, and wherein the phase shift device has a refractive index of 4 or more in a wavelength band between the first resonance wavelength band and the second resonance wavelength band. 11 . The phase shift device according to claim 10 , wherein the phase shift device has a refractive index difference of 0.3 or less in the wavelength band between the first resonance wavelength band and the second resonance wavelength band.

12. The phase shift device according to claim 1, wherein the phase shift device comprises a plurality of the stacked structures arranged two-dimensionally, and The second dielectric layer has a lattice shape surrounding side surfaces of the plurality of stacked structures. 13 . The phase shift device according to claim 12 , wherein a horizontal cross-section of each of the stacked structures has one of a square shape, a rectangular shape, an elliptical shape, a triangular shape, a circular shape, a parallelogram shape, a trapezoidal shape, a rhombus shape, and a polygonal shape of at least a pentagon. 14 . The phase shift device of claim 12 , wherein the plurality of stack structures include a first stack structure and a second stack structure that are different from each other in at least one of a width of the metal layer, a thickness of the metal layer, and a thickness of the first dielectric layer.

15. The phase shift device according to claim 12, wherein the stacked structures arranged at different positions have different widths and / or thicknesses, and The phase shift device has different refractive indices based on the position of the stacked structure in the phase shift device. 16 . The phase shift device according to claim 15 , wherein the stacked structures having different widths and / or thicknesses are arranged so that the phase shift device is a symmetrical plane lens or an asymmetrical flat aspheric lens. 17 . The phase shift device according to claim 12 , wherein widths of the plurality of stacked structures gradually increase or decrease from a center of the phase shift device to an edge of the phase shift device.

18. The phase shift device according to claim 1, wherein a thickness of the metal layer is in a range from 5 nm to 20 nm.

19. The phase shift device according to claim 1, wherein a thickness of the first dielectric layer is in a range from 2.5 nm to 15 nm.

20. The phase shift device according to claim 1, wherein a sum of a thickness of one metal layer and a thickness of one first dielectric layer is 30 nm or less. 21 . The phase shift device according to claim 1 , wherein a width of the stack structure is in a range from 30 nm to 110 nm.

22. The phase shift device according to claim 1, wherein a width of the second dielectric layer is in a range from 20 nm to 50 nm, and The sum of the width of the stacked structure and the width of the second dielectric layer is in the range of 50 nm to 200 nm. 23 . The phase shift device according to claim 1 , wherein a first dielectric constant of the first dielectric layer is less than 20, and a second dielectric constant of the second dielectric layer is greater than 30.

24. The phase shift device according to claim 23, wherein the first dielectric layer comprises SiO2, Al2O3, Si3N4, Na2SO4, Sr3(PO4)2, YAlO3, MgSiO3, YOCl, CaB4O7, Al2MgO4, Ba2SiO4, B2O3, Mg4O3(OH)2, Ba3P4O 13 , Li3OBr, Mg(OH)2, Y2(Si2O7), AlLiO2, YOF, Ba3(PO4)2, SrB4O7, BaSO4 and at least one of poly(methyl methacrylate).

25. The phase shift device of claim 23, wherein the second dielectric layer comprises TiO2, HfO2, ZrO2, ZnO, SrTiO3, GaN, GaP, BeO, NbOCl3, NaNbO3, NaTaO3, AgTaO3, Li4CO4, CdTiO3, KTaO3, Y2Ti2O7, Cd2Ta2O7, PbHfO3, AlO(OH), SrHfO3, Ag2Ta4O 11 , BaZrO3, PbZrO3, NaIO3, BiTaO4, HfTe3O8, K2W2O7 and Sr2Ta2O7. 26 . The phase shift device according to claim 1 , wherein the metal layer comprises at least one of aluminum (Al), silver (Ag), gold (Au), and copper (Cu).

27. An optical device comprising a phase shift device, wherein the phase shift device comprises a plurality of unit elements, the plurality of unit elements are arranged one-dimensionally or two-dimensionally to form an array structure, each unit element comprising: A stacked structure, comprising a metal layer and a first dielectric layer, wherein the metal layer and the first dielectric layer are alternately stacked in a vertical direction; and A second dielectric layer is disposed on a side surface of the stacked structure in a horizontal direction, wherein the first dielectric layer comprises a first material having a first dielectric constant, and the second dielectric layer comprises a second material having a second dielectric constant, wherein the first material is different from the second material, wherein the second dielectric constant is greater than the first dielectric constant, and The phase shift device further includes an oxide layer disposed between the side surface of the stack structure and the second dielectric layer.

28. The optical device of claim 27, configured as a planar lens or a planar beam deflector in the visible or near infrared region. 29 . The optical device according to claim 27 , wherein a first dielectric constant of the first dielectric layer is less than 20, and a second dielectric constant of the second dielectric layer is greater than 30.

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