TWM673033U - Metalens - Google Patents

Abstract

A metalens including a substrate and a plurality of meta-atoms is provided. The meta-atoms are distributed on the substrate. Each of the meta-atoms includes two phase retardation structures crossing in a direction parallel to the substrate. Pitches of the meta-atoms are not completely the same, and focal lengths of the meta-atoms are not completely the same.

Description

Ultra-slim lens

This novel invention relates to an optical element, and in particular to a super-sharp lens (metalens).

For the past few decades, optical lenses have been an indispensable component in optical systems, used in applications such as imaging, focusing, and adjusting focus. However, traditional lenses have limitations, such as thickness and shape that restrict imaging quality, and interference from light fields such as refraction and scattering, which can cause stray light or ghost images. These limitations have limited their use in some applications.

Subsequently, super-lenses were developed. However, the modulation transfer function (MTF) of images produced by these super-lenses, which typically use circular meta-atoms, still has room for improvement.

This novel invention provides an ultra-smooth lens that can effectively improve the modulation transfer function value and imaging quality.

One embodiment of the present invention provides a super-lens comprising a substrate and a plurality of super-atoms. These super-atoms are distributed on the substrate, each of which includes two phase-delay structures intersecting in a direction parallel to the substrate. The super-atoms have different pitches and different focal lengths.

In the meta-lens of this embodiment of the invention, each meta-atom includes two phase-delay structures intersecting in a direction parallel to the substrate, and these meta-atoms have unequal pitches and focal lengths. Therefore, compared to meta-lenses using circular meta-atoms, this embodiment of the invention can achieve a higher modulation transfer function (MTF) value, effectively improving the imaging quality of the meta-lens.

Figure 1A is a schematic front view of a superlens according to an embodiment of the present invention. Figure 1B is a partially enlarged schematic view of region M1 in Figure 1A. Figure 2A is a schematic front view of a superatom in Figure 1A. Figure 2B is a schematic three-dimensional view of a superatom in Figure 1A. Figure 3 is a schematic cross-sectional view of the optical system of the superlens in Figure 1A. Referring to Figures 1A, 1B, 2A, 2B, and 3, the superlens 100 of this embodiment includes a substrate 110 and a plurality of superatoms 200. These super-sharp atoms 200 are distributed on a substrate 110. Each super-sharp atom 200 includes two phase delay structures 210 and 220 that intersect in a direction parallel to the substrate 110. These super-sharp atoms 200 have different pitches P and focal lengths. In this embodiment, the design of these super-sharp atoms 200 conforms to Babinet's principle.

In this embodiment, the two phase delay structures 210 and 220 intersect at a 90-degree angle. In this embodiment, each of the two phase delay structures 210 and 220 is in the shape of a rectangular column. In other words, in this embodiment, the two intersecting phase delay structures 210 and 220 form a cross-shaped column, whose cross-section parallel to the substrate 110 is cross-shaped.

Furthermore, in this embodiment, each superatom 200 further includes multiple fillet structures 230 ( FIG. 2A shows four fillet structures 230 as an example) located adjacent to the intersection of the two phase delay structures 210 and 220. In this embodiment, the angles θ1 and θ2 between the side surfaces 232 of these fillet structures 230 and the adjacent side surfaces 212 and 222 of the two phase delay structures 210 and 220 are both, for example, 135 degrees.

In this embodiment, these super-slim atoms 200 are distributed on opposite surfaces 112 and 114 of substrate 110 (as shown in FIG3 ). Furthermore, in this embodiment, the super-slim atoms 200 on surface 112 and the super-slim atoms 200 on surface 114 are mirror-symmetrical with respect to substrate 110. In this embodiment, the material of these super-slim atoms 200 is, for example, titanium dioxide, and the material of substrate 110 is, for example, gallium nitride, but the present invention is not limited to this. In this embodiment, the surface 114 in FIG. 3 and the area to the left of the superslim atoms 200 thereon are, for example, air, and the surface 112 in FIG. 3 and the area to the right of the superslim atoms 200 thereon are, for example, air. The refractive index of air is, for example, 1. The "phase delay" of the phase delay structures 210 and 220 refers to the fact that their materials have a greater phase delay effect than air. The fillet structure 230 can be made of the same material as the phase delay structures 210 and 220, and the fillet structure 230 and the phase delay structures 210 and 220 can be integrally formed. Furthermore, in this embodiment, the substrate 110 is, for example, a circular substrate, and the superslim atoms 200 are arranged in an array on the substrate 110.

In the meta-lens 100 of this embodiment, each meta-atom 200 includes two phase delay structures 210 and 220 intersecting in a direction parallel to the substrate 110. These meta-atoms 200 have different pitches P and focal lengths. Therefore, compared to meta-lenses using circular meta-atoms, the meta-lens 100 of this embodiment can achieve a higher modulation transfer function (MTF) value, effectively improving the imaging quality of the meta-lens 100. For example, for incident light with a wavelength of 520 nanometers, at the same effective focal length and within a field of view of 0 to 20 degrees, the meta-lens 100 of this embodiment can achieve a higher modulation transfer function value than a conventional meta-lens using circular meta-atoms. Furthermore, compared to conventional refractive lenses, the meta-lens 100 of this embodiment can be thinner and is less susceptible to interference from light refraction and scattering, resulting in less stray light or ghosting in the image.

In this embodiment, the super-lenses 100 meet the following conditions: 0.25 μm < P < 0.5 μm, where P is the pitch of the super-atoms 200.

In this embodiment, each superatom 200 of the superlens 100 satisfies the following conditions: 0.25 μm < W < 0.5 μm; and 0.25 μm < H < 0.5 μm, where W is the length of one of the two phase delay structures 210 and 220 (e.g., the phase delay structure 210) in a direction parallel to the substrate 110, and H is the length of the other of the two phase delay structures 210 and 220 (e.g., the phase delay structure 220) in a direction parallel to the substrate 110.

In this embodiment, each superatom 200 of the superlens 100 satisfies the following relationship: 0.5 μm < L < 1 μm, where L is the height of the superatom 200 in a direction perpendicular to the substrate 110.

Figure 4A shows the light energy distribution curve of the super-smooth lens of Figure 1A when it focuses normally incident parallel light onto the imaging surface along the line Y = 0. Figure 4B shows the light energy distribution curve of the super-smooth lens of Figure 1A when it focuses normally incident parallel light onto the imaging surface along the line X = 0. In Figure 1A , the X and Y directions are both parallel to the substrate 110, the Z direction is perpendicular to the substrate 110, and the X, Y, and Z directions are all perpendicular to each other. As can be seen from Figures 4A and 4B , the light energy distribution is concentrated, and the super-smooth lens 100 has excellent imaging quality.

Figure 5A shows a light energy distribution curve for another embodiment of the super-smooth lens of Figure 1A, where the light energy of vertically incident parallel light is focused onto the imaging surface along a straight line at Y = 0. Figure 5B shows a light energy distribution curve for another embodiment of the super-smooth lens of Figure 1A, where the light energy of vertically incident parallel light is focused onto the imaging surface along a straight line at X = 10 microns. Referring to Figures 5A and 5B , the super-smooth lens 100 of this embodiment utilizes a properly distributed design with varying pitches P, thereby deflecting the light emitted from the super-smooth lens 100 toward a 20-degree field of view in the X direction. As shown in Figures 5A and 5B , even when the emitted light is deflected toward a 20-degree field of view, the light energy distribution remains concentrated, thus maintaining excellent imaging quality.

Figure 6 is a graph showing the modulation transfer function of the image formed on the imaging surface by the light energy of Figures 4A and 4B on the line at X=0 and the line at Y=0, and Figure 7 is a graph showing the modulation transfer function of the image formed on the imaging surface by the light energy of Figures 5A and 5B on the line at X=10 microns and the line at Y=0. Figure 8 is a graph showing the modulation transfer function of the image formed on the imaging surface by the light energy of Figures 4A and 4B and the modulation transfer function of a conventional superlens using circular superatoms at a viewing angle of 0 degrees. These two modulation transfer functions are labeled "Present Embodiment" and "Conventional Superlens" in Figure 8, respectively. FIG9 is a graph showing the modulation transfer function (MTF) of the image formed on the imaging surface by the light energy in FIG5A and FIG5B , and the MTF of a conventional meta-lens using circular meta-atoms at a viewing angle of 20 degrees. These two MTFs are labeled "Present Embodiment" and "Conventional Meta-lens" in FIG9 , respectively. As can be seen from FIG6 to FIG9 , at the same effective focal length and within a field of view range of 0 to 20 degrees, the meta-lens 100 of this embodiment achieves a higher MTF value than a conventional meta-lens using circular meta-atoms.

Figure 10A shows the refractive index distribution of a single superatom in the superlens of Figure 1A along the Y direction, Figure 10B shows the refractive index distribution of a single superatom in the superlens of Figure 1A along the X direction, and Figure 11 shows the total transmittance and total reflectance distribution of a single superatom in the superlens of Figure 1A in the visible light band at different light output angles. Referring to Figures 10A, 10B, and 11, Figures 10A and 10B illustrate the refractive index distribution of the superlens 100 at different positions along the X and Y directions. Figure 11 shows that the superatom 200 of this embodiment has good transmittance, with high diffraction efficiency indicating high transmittance.

In summary, in the meta-lens of this embodiment of the present invention, each meta-atom includes two phase-delay structures intersecting in a direction parallel to the substrate, and these meta-atoms have unequal pitches and focal lengths. Therefore, compared to meta-lenses employing circular meta-atoms, this meta-lens can achieve a higher modulation transfer function (MTF) value, effectively improving the imaging quality of the meta-lens.

100: Super-lens 110: Substrate 112, 114: Surface 200: Super-atom 210, 220: Phase delay structure 212, 222, 232: Side surface 230: Fillet structure H, W: Length L: Height P: Pitch X, Y, Z: Directions θ1, θ2: Angle

FIG1A is a schematic front view of a super-smooth lens according to an embodiment of the present invention. FIG1B is a partially enlarged schematic diagram of region M1 in FIG1A. FIG2A is a schematic front view of a super-smooth atom in FIG1A. FIG2B is a schematic three-dimensional diagram of a super-smooth atom in FIG1A. FIG3 is a schematic cross-sectional diagram of the optical system of the super-smooth lens in FIG1A. FIG4A is a light energy distribution curve of the light energy on the straight line Y=0 when the super-smooth lens in FIG1A focuses vertically incident parallel light on the imaging surface. FIG4B is a light energy distribution curve of the light energy on the straight line X=0 when the super-smooth lens in FIG1A focuses vertically incident parallel light on the imaging surface. Figure 5A is a graph showing the energy distribution of light energy on a straight line at Y=0 when the superlens of Figure 1A is used to focus normally incident parallel light onto an imaging surface. Figure 5B is a graph showing the energy distribution of light energy on a straight line at X=10 microns when the superlens of Figure 1A is used to focus normally incident parallel light onto an imaging surface. Figure 6 is a graph showing the modulation transfer function of the images formed on the imaging surface by the light energy of Figures 4A and 4B on the straight line at X=0 and the straight line at Y=0. Figure 7 is a graph showing the modulation transfer function of the images formed on the imaging surface by the light energy of Figures 5A and 5B on the straight line at X=10 microns and the straight line at Y=0. Figure 8 is a graph showing the modulation transfer function of the image formed on the imaging surface by the light energy of Figures 4A and 4B, and the modulation transfer function of a conventional super-silver lens using circular super-atom at a viewing angle of 0 degrees. Figure 9 is a graph showing the modulation transfer function of the image formed on the imaging surface by the light energy of Figures 5A and 5B, and the modulation transfer function of a conventional super-silver lens using circular super-atom at a viewing angle of 20 degrees. Figure 10A is a graph showing the distribution of the transverse index of a single super-atom in the super-silver lens of Figure 1A in the Y direction. Figure 10B is a graph showing the distribution of the transverse index of a single super-atom in the super-silver lens of Figure 1A in the X direction. FIG11 is a graph showing the distribution of the total transmittance and total reflectance of a single superatom in the superlens of FIG1A at different light output angles in the visible light band.

110:Substrate

112: Surface

200: Super-sharp Atom

210, 220: Phase Delay Structure

212, 222, 232: side

230: Fillet structure

L: Height

Claims (10)

A super-sharp lens includes: a substrate; and a plurality of super-sharp atoms distributed on the substrate, each super-sharp atom including two phase delay structures crossing in a direction parallel to the substrate, wherein the super-sharp atoms have different pitches and different focal lengths. The super lens of claim 1, wherein each super atom further comprises a plurality of fillet structures located adjacent to the intersection of the two phase delay structures. The super lens of claim 2, wherein the side surfaces of the fillet structures and the adjacent side surfaces of the two phase delay structures form an angle of 135 degrees. The superlens as described in claim 3, wherein the two phase delay structures are crossed at 90 degrees. The superlens as described in claim 4, wherein each of the two phase delay structures is in the shape of a rectangular column. The super lens as described in claim 1, wherein the material of the super atoms is titanium dioxide, and the material of the substrate is gallium nitride. The super-smooth lens of claim 1, wherein the super-smooth lenses meet the following conditions: 0.25 μm < P < 0.5 μm, where P is the pitch of the super-smooth atoms. The superlens as described in claim 1, wherein each superatom of the superlens satisfies the following conditions: 0.25 μm < W < 0.5 μm; and 0.25 μm < H < 0.5 μm, wherein W is the length of one of the two phase delay structures in a direction parallel to the substrate, and H is the length of the other of the two phase delay structures in a direction parallel to the substrate. The super-lens as described in claim 1, wherein each super-atom of the super-lens satisfies the following conditions: 0.5 μm < L < 1 μm, where L is the height of the super-atom in a direction perpendicular to the substrate. The super-lens as described in claim 1, wherein the super-atoms are distributed on two opposite surfaces of the substrate.