KR102587061B1 - Spectrometer including metasurface - Google Patents

Abstract

A spectroscope including a metasurface according to the present disclosure may include at least one metasurface including a plurality of nanostructures arranged in two dimensions and a peripheral body surrounding the plurality of nanostructures. Metasurfaces can implement the functions of various optical devices by arranging various nanostructures. Metasurfaces can be thinner and lighter than conventional optical devices. The spectrometer according to the present disclosure may have a sufficiently large optical path length compared to thickness.

Description

Spectrometer including metasurface}

The present disclosure relates to a spectrometer comprising a metasurface.

Optical elements that change the transmission/reflection, polarization, phase, intensity, and path of incident light are used in various optical devices. Since these optical elements mainly include heavy lenses, mirrors, etc., it is difficult to minimize the size of the optical device including the optical elements. Because spectrometers also contain these optical elements, they are large and heavy. Various research is being conducted to miniaturize the structure of the spectroscope and improve its performance.

The present disclosure relates to a spectrometer comprising a metasurface.

A spectrometer according to one embodiment includes a transparent substrate including a first side and a second side facing each other; a slit provided on the first surface and allowing light to be inspected to enter the transparent substrate; Provided on the first or second surface, it includes at least one metasurface including a plurality of nanostructures arranged in two dimensions and a peripheral body surrounding the plurality of nanostructures, the at least one metasurface a spectroscopic optical system including a focusing metasurface that reflects and focuses light incident through the slit at different angles for each wavelength; and a sensor provided on the first or second side of the transparent substrate and receiving light from the spectroscopic optical system. Includes.

It may further include a blocking film disposed on the transparent substrate and blocking light from entering areas other than the slit.

The spectroscopic optical system may further include a collimating metasurface having a plurality of nanostructures arranged two-dimensionally to have a collimating function.

The collimating metasurface may be located on an optical path between the slit and the focusing metasurface.

The spectroscopic optical system may further include a grating metasurface having a plurality of nanostructures arranged two-dimensionally to have a chromatic dispersion function.

The grating metasurface may be located on an optical path between the collimating metasurface and the focusing metasurface.

The grating metasurface and sensor may be provided on the first side, and the collimating metasurface and focusing metasurface may be provided on the second side.

In a plan view seen in a direction perpendicular to the first surface, the grating metasurface, collimating metasurface, focusing metasurface, and sensor may be arranged two-dimensionally.

The transparent substrate includes side surfaces connecting the first side and the second side, and in a plan view viewed in a direction perpendicular to the first side, the collimating metasurface and the grating surface are one of the side surfaces. Closer to , the focusing metasurface and the sensor may be arranged closer to the other side facing the one side.

In the at least one metasurface, the height of each of the plurality of nanostructures or the longest diameter in cross section of the plurality of nanostructures may be smaller than the wavelength of the light.

The grating metasurface is,

It may include a pattern including a plurality of nanostructures arranged at regular intervals in a second direction, and the pattern may be arranged to repeat periodically in a first direction perpendicular to the second direction.

The focusing metasurface may have one or more annular regions in which a plurality of nanostructures are arranged so that the cross-sectional area increases or decreases as the distance from a certain point of the focusing metasurface increases.

The spectroscopic optical system further includes a split metasurface configured to separate light into first polarization and second polarization according to polarization and reflect the separated first polarization and second polarization by wavelength, and the sensor It may include a first sensor provided to receive the separated first polarized light, and a second sensor provided to receive the separated second polarized light.

The focusing metasurface may include a first focusing metasurface for focusing the first polarized light to the first sensor and a second focusing metasurface for focusing the second polarized light to the second sensor.

The split metasurface includes a pattern including a plurality of nanostructures arranged so that diameter components in a first direction increase and decrease, respectively, and the one pattern is formed in the first direction and perpendicular to the first direction. It may be made to repeat periodically along the second direction.

When the total length of the optical path from the slit to the sensor is L and the thickness of the transparent substrate is D, L and D may satisfy the following relationship.

L/D > 3

The peripheral body may be made of at least one material selected from silicon oxide (SiO ₂ ), glass, and polymer.

The transparent substrate may be made of at least one material selected from silicon oxide (SiO ₂ ), glass, and polymer.

The plurality of nanostructures may be made of at least one material selected from c-Si, a-Si, p-Si, GaP, GaAs, SiC, TiO2, SiN, and GaN.

The spectroscope according to the present disclosure may include a metasurface that can replace various optical elements such as convex lenses, concave lenses, prisms, and beam deflectors. This metasurface may include a plurality of nanostructures arranged in two dimensions.

The spectrometer according to the present disclosure includes a metasurface that is relatively small compared to the optical element, so the volume can be reduced.

Additionally, the spectrometer according to the present disclosure can improve spectral performance by increasing the length of the optical path compared to the volume.

1 is a cross-sectional view schematically showing a spectrometer according to an embodiment.
Figure 2 is a diagram showing a focusing metasurface according to one embodiment.
Figure 3 is a diagram showing a focusing metasurface according to another embodiment.
Figure 4 is a cross-sectional view schematically showing a spectroscope according to another embodiment.
Figures 5a to 5d are perspective views showing the schematic shape of the nanostructure.
Figure 6 is a diagram showing a grating metasurface according to an embodiment.
FIG. 7 is a graph showing the grating efficiency of the grating metasurface according to FIG. 6.
Figure 8 is a diagram showing a grating metasurface according to another embodiment.
Figure 9 is a cross-sectional view schematically showing a spectrometer according to another embodiment.
Figure 10 is a cross-sectional view schematically showing a spectrometer according to another embodiment.
FIG. 11 is a plan view schematically showing the spectrometer according to FIG. 10 looking down from one direction.
Figure 12 is a perspective view schematically showing a spectrometer according to another embodiment.
Figure 13 is a diagram showing a split metasurface according to an embodiment.
FIG. 14 is a diagram showing the nanostructure pattern of the split metasurface according to FIG. 13.

Hereinafter, a spectroscope including a metasurface will be described in detail with reference to the attached drawings. The size of each component in the drawings may be exaggerated for clarity and convenience of explanation. Additionally, the embodiments described below are merely illustrative, and various modifications are possible from these embodiments.

Figure 1 is a cross-sectional view schematically showing a spectrometer 100 according to an embodiment.

Referring to FIG. 1, the spectrometer 100 according to this embodiment may include a spectroscopic optical system 110 including a focusing metasurface 111, a sensor 120, a transparent substrate 130, and a slit 140. there is.

The spectrometer 100 according to this embodiment can replace a relatively bulky conventional optical element with a flat spectroscopic optical system 110 including a metasurface. Optical elements may include, for example, collimators, prisms or grating patterns, concave mirrors, etc. The spectroscopic optical system 110 may be lighter and smaller in volume than the optical elements described above.

The transparent substrate 130 may be made of a material that is transparent to incident light and has a low refractive index. For example, the incident light may be light in the visible, infrared, and ultraviolet regions, and the transparent substrate 130 may be transparent to such light. Transparency may mean that there is no or very little light loss as light travels through the interior of the transparent substrate 130. For example, the material of the transparent substrate 130 may be glass or polymer. Polymers may include PMMA, PDMS, SU8, etc. The transparent substrate 130 made of polymer may have flexibility.

The transparent substrate 130 may have a flat shape. The flat plate may include a first side that is relatively wider than the side surface and a second side that faces the first side. The flat plate may include sides connecting the first side and the second side. Flat plates can include not only flat plates but also curved plates.

Referring to FIG. 1, the spectroscopic optical system 110 may include at least one metasurface including a plurality of nanostructures (ns) arranged in two dimensions and a peripheral body (sr) surrounding the plurality of nanostructures. . It may include a plurality of nanostructures (ns) and a peripheral body (sr) surrounding the plurality of nanostructures (ns). Nanostructures (ns) can have various arrangements inside the metasurface, and depending on the various arrangements of the nanostructures (ns), the metasurface can function as various optical elements. For example, the spectroscopic optical system 110 may include a metasurface that functions as a collimator, a grating element, a focusing mirror, etc.

The nanostructure (ns) may have a higher refractive index than the surrounding material (sr). The refractive index may be greater than that of the transparent substrate 130. The nanostructure (ns) and the peripheral body (sr) may be provided on a substrate (sub), and the refractive index of the nanostructure (ns) may be greater than that of the substrate (sub). Each metasurface may have a nanostructure (ns) and a peripheral body (sr) placed on a substrate (sub), but the substrate (sub) may be removed after forming the metasurface. Although each metasurface is shown in the drawing as including a substrate (sub), it is not limited thereto.

Nanostructures (ns) can temporarily trap received light inside each nanostructure (ns) like a kind of weak resonator due to the high-contrast refractive index difference. The greater the refractive index contrast between the nanostructure (ns) and the surrounding material (sr), the longer the nanostructure (ns) can trap light and the more light it can capture inside the nanostructure. The wavelength range of light captured by the nanostructure (ns) may be different for each nanostructure (ns), and can be referred to as the resonance wavelength range. The resonance wavelength band of the nanostructure (ns) may vary depending on the shape, size, and refractive index of the nanostructure (ns). Each nanostructure (ns) can re-emit the captured light. The phase of light exiting from the nanostructure (ns), such as reflection or transmission, may be relatively different depending on the shape of the nanostructure (ns).

The nanostructure (ns) may have a dimensional element with a length smaller than the resonance wavelength. For example, since light in the infrared or visible light region has a wavelength of hundreds of nm, the dimensional element of the nanostructure (ns) for transmitting and receiving visible light may be hundreds of nm or less. When the length of the dimensional element of the nanostructure (ns) is smaller than the resonance wavelength, light may be subjected to subwavelength scattering or subwavelength grating. The dimensional element may refer to a length element of the three-dimensional shape of the nanostructure (ns), such as the height or diameter of the nanostructure (ns). Accordingly, the longest length among the dimensional elements of the plurality of nanostructures (ns) may be smaller than the wavelength of the incident light. The light incident on the array of nanostructures (ns) that satisfies these sub-wavelength scattering conditions has optical properties such as wavelength, polarization, and emission (or reflection) angle depending on the shape, volume, and arrangement of the nanostructures (ns). It can change.

The material of the nanostructure (ns) may be formed of a material with a higher refractive index than the surrounding material (sr). For example, the material of the nanostructure (ns) may include at least one of c-Si, a-Si, p-Si, GaP, GaAs, SiC, TiO2, SiN, and GaN. Or, for example, the nanostructure (ns) may be formed of metal. A nanostructure (ns) formed of a metal can cause a surface plasmon effect in relationship with the surrounding material (sr).

The peripheral body (sr) and the transparent substrate 130 may be formed of a material with a lower refractive index than the nanostructure (ns). For example, the peripheral body (sr) and the transparent substrate 130 may have a refractive index less than 1.5 compared to the nanostructure (ns). The peripheral body sr may be formed of a material that is transparent to incident light. For example, the peripheral body sr may be formed of the same material as the transparent substrate 130. For example, the peripheral body sr may be made of glass, silicon oxide (SiO ₂ ), or polymer. Polymers may include PMMA, PDMS, SU8, etc.

The peripheral body sr may not be formed as a separate structure, but may be a partial area of the transparent substrate 130 where a plurality of nanostructures ns are arranged.

For example, the step of forming the integrated spectroscopic optical system 110 on the transparent substrate 130 may be as follows. In the first step, the nanostructure (ns) material may be deposited or applied on the transparent substrate 130. In the second step, the nanostructure (ns) material may be formed into a specific pattern in a certain area where the spectroscopic optical system 110 will be formed using a semiconductor process. In the third step, the same material as the transparent substrate 130 may be deposited or applied onto the deposited or applied material of the nanostructure (ns) to form a peripheral body (sr) surrounding the nanostructure (ns). This step of forming the spectroscopic optical system 110 is only an example and is not limited thereto.

Metasurfaces can have various optical device functions depending on the arrangement of nanostructures (ns). The spectrometer 100 according to this embodiment may include a spectroscopic optical system 110 including a focusing metasurface 111, a collimating metasurface (212 in FIG. 2), a grating metasurface (212 in FIG. 2), etc. there is.

The focusing metasurface 111 may function as a focusing mirror. The focusing metasurface 111 can focus the light incident on the slit 140 to a different location for each wavelength and allow it to enter the sensor 120 to become spectral light. We will look at this in detail below in Figures 2 and 3.

The sensor 120 may receive light according to wavelength. The sensor 120 may include a known light receiving sensor used in a spectrometer. The sensor 120 may include a known pixelated sensor such as a charge coupled device (CCD), complementary metal-oxide semiconductor (CMOS), or InGaAs sensor that can receive light in one or two dimensions.

The slit 140 can adjust the amount and angle of incidence of light incident on the transparent substrate 130. For example, the slit 140 may be a hole of a certain size that is not blocked by a blocking film, which will be described later. For example, the slit 140 may include a convex lens capable of concentrating incident light. These lenses can also be made as transmissive metasurface lenses made of nanostructures (ns) and peripheral elements (rs). Additionally, the slit 140 may have a variable diameter to adjust the amount of light entering.

The spectrometer 100 may further include a blocking film to block external light. The blocking film is disposed on the transparent substrate 130 and can absorb light so that it does not enter areas other than the slit 140. The blocking film may have a material that reflects or absorbs light such as ultraviolet rays, visible rays, and infrared rays. For example, the blocking film may be made of a metal material and reflect external light. For example, the blocking film can absorb light using a light-absorbing material such as carbon black. The blocking film blocks the inflow of external light other than the light incident on the slit 140, thereby improving the spectral efficiency of the spectrometer 100. The blocking film may be provided to surround the transparent substrate 130 except for the slit 140. For example, the blocking film may be formed by coating the outer surface of the transparent substrate 130 with the metal material. In short, the blocking film is sufficient to block external light flowing into the spectroscope 100, and its specific composition or material is not limited.

Since the spectrometer 100 according to this embodiment includes only the focusing metasurface 111 as the spectroscopic optical system 110, it has a simple structure and can have a small volume.

FIG. 2 is a diagram illustrating a focusing metasurface 111 according to an embodiment. FIG. 3 is a diagram showing a focusing metasurface 111' according to another embodiment.

Referring to FIG. 2, the focusing metasurface 111 may include an array of nanostructures (ns) that function as the focusing mirror described above. The plurality of nanostructures (ns) may be arranged so that the cross-sectional diameter gradually decreases or increases as the distance from one point on the focusing metasurface 111 increases. For example, the plurality of nanostructures (ns) may be arranged so that the distance from center to center is constant and the duty ratio decreases as the distance from one point increases. When the diameter of the nanostructure (ns) located closest to a point is f ₀ and the respective diameters of the nanostructures (ns) located sequentially farther from it are f ₁ , f ₂ , and f ₃ , the diameter f ₀ , f ₁ , f ₂ and f ₃ can satisfy the relationship f ₀ > f ₁ > f ₂ > f ₃ . A group of nanostructures (ns) that satisfy the relationship f ₀ > f ₁ > f ₂ > f ₃ may be called an annular region, and the focusing metasurface 111 may include at least one annular region.

Referring to FIG. 3, the focusing metasurface 111' may include a plurality of annular regions where the diameter of the cross section of the nanostructure (ns) gradually decreases as the distance from a point on the focusing metasurface 111' increases. there is. For example, the focusing metasurface 111' may include a first annular region and a second annular region as it moves away from the center.

In the cross-sectional view of the focusing metasurface 111' along the B-B' direction, the phase of light emitted from the focusing metasurface 111' has a phase shift of 2pi between the first annular region and the second annular region. You can.

The focusing metasurface (111, 111') adjusts the shape, angle, and chromatic dispersion of the focused light by adjusting the diameter of the nanostructure, the distance between nanostructures, the shape of the cross section of the nanostructure, the material, duty ratio, and annular region. Various light characteristics can be adjusted.

Figure 4 is a cross-sectional view schematically showing a spectrometer 200 according to another embodiment.

Referring to FIG. 4, the spectrometer 200 according to this embodiment may include a spectroscopic optical system 210 that further includes a collimating metasurface 212 and a grating metasurface 213. Descriptions of components that overlap with the spectrometer 100 will be omitted.

The collimating metasurface 212 may function as a light deflector and collimator. The collimating metasurface 212 converts the wavefront of light incident through the slit 140 into a plane wave, collimates and reflects and diffracts the light to prevent diffusion, and directs it at a specific angle to the grating metasurface 213. It can be biased.

The collimating metasurface 212 can be created by appropriately mixing the properties of the grating metasurface 213 and the focusing metasurface 111. For example, the collimating metasurface 212 reflects the form of light incident through the slit 140 (wavefront shape and intensity distribution) and the form of a plane wave that is reflected from the collimating metasurface 212 and proceeds in a specific direction. can be determined in advance. Based on this, the reflection phase distribution that the collimating metasurface 212 should have can be determined based on the location on the plane where the collimating metasurface 212 is to be located. The reflection phase distribution may correspond to the cross section of a kind of hologram. For example, when the wavefront of the incident light is similar to a diverging square wave, the collimating metasurface 212 is a grating meta that diffracts the phase distribution and plane wave incident beam in a specific direction of the metasurface, which acts as a concave mirror. The phase distribution of the surface may be added to each other.

The grating metasurface 213 may function as a grating element. The grating metasurface 213 can reflect and diffract light at different angles depending on the wavelength. The arrangement of the nanostructures of the grating metasurface 213 will be examined in detail in FIGS. 6 to 8 below.

If the average length of the optical path from the slit 140 to the sensor 120 that receives the light is L, the longer L is, the better the spectral performance of the spectrometer can be. Since the length of the optical path may vary slightly depending on the light of each wavelength, L will be defined as the length of the optical path of light of an intermediate wavelength.

We will look at the principle that the longer L, the better the spectral efficiency of the spectrometer. The collimating, grating, and focusing metasurface elements are made of nanostructures, so they can have chromatic dispersion characteristics in which light of different wavelengths is reflected and diffracted at different angles. Accordingly, when light with different wavelengths passing through these elements is incident on sufficiently different positions (pixels) of the sensor 120, spectral resolution (incident wavelength interval/pixel size) can be increased. In other words, the chromatic dispersion characteristics of metasurface elements with different diffraction angles for each wavelength create a larger difference in the focus position of light for each wavelength in the sensor as the overall optical path increases. As the average length L of the optical path increases, the spectrometer can resolve even finer differences in diffraction angles between wavelengths, thereby increasing the spectral efficiency of the spectrometer 200. The spectrometer 200 according to this embodiment replaces the optical element with a thin flat metasurface and can make the average length L of the optical path sufficiently long compared to the thickness d of the transparent substrate 130, thereby improving the spectral efficiency. You can secure enough. For example, the spectrometer 200 may satisfy the following relationship.

[Equation 1]

L/d > 3

The spectrometer 200 according to this embodiment may have the arrangement and dimensional elements of the spectroscopic optical system 210 to satisfy Equation 1. The spectrometer 200 that satisfies Equation 1 may have high spectral efficiency. The grating metasurface 213 can improve the length L of the optical path of light incident on the spectrometer 200.

Figures 5a to 5d are perspective views showing the schematic shape of the nanostructure.

Referring to FIGS. 5A to 5D, the plurality of nanostructures (ns) may have various shapes. The nanostructure (ns) may have a pillar shape. For example, the nanostructure (ns) may have a cross-section of any one of circular, oval, rectangular, and square shapes. When creating a metasurface, nanostructures (ns) can have various cross-sectional shapes and height distributions on a two-dimensional surface.

FIG. 6 is a diagram illustrating a grating metasurface 213 according to an embodiment. FIG. 7 is a graph showing the grating efficiency of the grating metasurface 213 according to FIG. 6.

Referring to FIG. 6, the arrangement of the nanostructures (ns) may correspond to the arrangement of the nanostructures (ns) of the grating metasurface 213.

As described above, when the length of the dimensional element of the nanostructure (ns) is smaller than the resonance wavelength of each nanostructure (ns), the light incident on the nanostructure (ns) may be sub-wavelength grated. Accordingly, the nanostructures (ns) of the grating metasurface 213 may be arranged repeatedly at regular intervals, with nanostructures (ns) having the same cross-sectional shape and cross-sectional size. The period represents the distance from the center of the adjacent nanostructure (ns) to the center. This period is smaller than the resonant wavelength. The wavelength decomposition effect of the grating metasurface 112 does not have the same efficiency for light in all wavelength ranges, and depends on the cross-sectional shape of each nanostructure (ns), the size of the cross-sectional area, and the spacing between nanostructures (ns). It can have diffraction efficiency for different wavelengths.

Referring to FIG. 6, the arrangement of nanostructures (ns) according to this embodiment may include a 1-1 pattern and a 1-2 pattern that are periodically repeated along the y-axis direction. The 1-1 pattern and the 1-2 pattern are just examples, and additional patterns may be included. For convenience of explanation, an embodiment including the 1-1 and 1-2 patterns will be described as follows.

The 1-1 pattern may include a plurality of nanostructures (ns) that are periodically repeated in the y-axis direction. The cross-sectional sizes and shapes of the plurality of nanostructures (ns) constituting the 1-1 pattern may be the same. The duty ratio of the 1-1 pattern may be constant. For example, a plurality of nanostructures (ns) may be periodically repeated by a distance l ₁ .

The 1-2 pattern may include a plurality of nanostructures (ns) that are periodically repeated in the y-axis direction. The cross-sectional sizes and shapes of the plurality of nanostructures (ns) constituting the 1-2 pattern may be the same. The duty ratio of the 1st and 2nd patterns may be constant. For example, a plurality of nanostructures (ns) may be periodically repeated by a distance l ₂ . The cross sections of the plurality of nanostructures (ns) constituting the 1-1 pattern and the cross sections of the plurality of nanostructures (ns) constituting the 1-2 pattern may have the same size or different sizes. .

Distance l ₁ and distance l ₂ may be equal to each other. The duty ratios of the 1-1 pattern and the 1-2 pattern may or may not match each other. By adjusting the shape of the 1-1 pattern and the 1-2 pattern, such as the duty ratio and the height of the nanostructure (ns), the corresponding wavelength region of the grating pattern can be adjusted.

The 1-1 pattern and the 1-2 pattern may be arranged to alternately repeat each other along the x-axis direction. The nanostructures of the 1-1 pattern and the 1-2 pattern may be arranged aligned with each other or shifted from each other along the x-axis direction. For example, some of the plurality of nanostructures (ns) constituting the 1-1 pattern and the 1-2 pattern may be arranged misaligned to have a hexagonal pattern. For example, a plurality of nanostructures (ns) constituting a hexagonal pattern may be arranged to form a regular hexagon by connecting the centers of each nanostructure (ns) constituting the hexagonal pattern.

An array of nanostructures (ns) having a hexagonal pattern repeated along the x-axis and y-axis directions may have higher grating efficiency than an array of nanostructures (ns) having patterns that are aligned with each other.

Referring to FIG. 7, the x-axis of the graph may represent the wavelength of light, and the y-axis of the graph may represent grating efficiency (%). For example, the nanostructure (ns) array according to FIG. 4 may have a grating efficiency of 55% or more for light in the wavelength range of 820 nm to 870 nm.

Figure 8 is a diagram showing a grating metasurface 213' according to another embodiment. Referring to FIG. 8, a plan view of the grating metasurface 213' and a cross-sectional view viewed in the direction A-A' on the plan view are shown. The grating metasurface 213' may include a second pattern including a plurality of nanostructures (ns) arranged so that the cross-sectional area gradually decreases or increases in the x-axis direction.

The second pattern may be repeated periodically with equal intervals l ₃ along the x-axis. For example, the second pattern may be a pattern in which the cross-sectional area gradually decreases from left to right along the +x-axis direction. For example, the second pattern may include nanostructures (ns) with diameters e ₀ , e ₁ , e ₂ , and e ₃ , respectively, and the diameters have the following relationship: e ₀ > e ₁ > e ₂ > e ₃ can be satisfied. For example, these diameters are such that the phase of light reflected from each nanostructure (ns) within the l ₃ interval is sampled at equal intervals between 0 and 2pi (e.g., 0, pi/2, pi, 3pi/2) can be designed. The grating metasurface 213' having this structure can provide a momentum of 2pi/l ₃ in the +x direction. Incident light can be reflected and diffracted by being deflected to the right in proportion to the momentum it has when entering the light.

The second pattern may repeat periodically along the y-axis. The second patterns may be arranged to be aligned or misaligned with each other along the y-axis. For example, the second pattern may be arranged so that nanostructures (ns) having the same cross-sectional area along the y-axis direction are aligned and periodically repeated with each other. For example, in the second pattern, nanostructures (ns) having different cross-sectional areas along the y-axis direction may be periodically and repeatedly arranged with each other offset to form a hexagonal pattern.

Figure 9 is a cross-sectional view schematically showing a spectrometer 300 according to another embodiment. The spectrometer 300 according to this embodiment has substantially the same configuration as the spectrometer 200 according to FIG. 2 except for the aberration control metasurface 314, so overlapping descriptions will be omitted below.

Referring to FIG. 9, light passes through the slit 140 and enters the transparent substrate 130, collimating metasurface 212, grating metasurface 213, focusing metasurface 111, and aberration control metasurface. The light may sequentially pass through 314 and be received by the sensor 120. With the introduction of the aberration control metasurface 314, the length l of the optical path of the spectrometer 300 can be increased. The aberration control metasurface 314 may have a function to correct aberration so that light of various wavelengths focused by the focusing metasurface 111 is incident on the position of each corresponding wavelength pixel of the sensor 120.

For example, the focusing metasurface 111 may also have the characteristics of a lens in that light is incident on the nanostructure (ns) and refracted. For example, when light passing through the focusing metasurface 111 is focused on the sensor 120, the position of the image may be misaligned due to chromatic aberration, spherical aberration, and astigmatism. These aberrations may reduce the spectral efficacy of sensor 120. The aberration control metasurface 314 may have an array of nanostructures (ns) to have an aberration control function. For example, the aberration control metasurface 214 may have the nanostructure array of the focusing metasurface 111 described above, or a nanostructure array that functions as a weak convex or concave lens.

Figure 10 is a cross-sectional view schematically showing a spectroscope 400 according to another embodiment. FIG. 11 is a plan view schematically showing the spectroscope 400 according to FIG. 10 when viewed from one direction.

Referring to FIG. 10, the spectrometer 400 according to this embodiment may include a collimating metasurface 411, a grating metasurface 412, a focusing metasurface 413, and a sensor 420.

Based on the slit 440, a collimating metasurface 411 may be provided below in the z direction. A grating metasurface 412 may be provided at a certain distance in the x-axis direction and the z-axis direction based on the collimating metasurface 411. A focusing metasurface 413 may be provided at a predetermined distance in the y-axis direction and the z-axis direction based on the grating metasurface 412. The sensor 420 may be provided at a predetermined distance in the x-axis direction and the z-axis direction based on the focusing metasurface 413. Light may be incident on the transparent substrate 430 through the slit 440, pass through the collimating metasurface 411, grating metasurface 412, and focusing metasurface 413 and be received by the sensor 420. .

Likewise, the focusing metasurface 413 has substantially the same focusing function as the focusing metasurface (313 in FIG. 1), but may have a function of adding optical momentum to light in a certain direction. For example, the focusing metasurface 413 may include a pattern in which nanostructures are arranged in a diagonal shape on the xy plane. For example, the grating metasurface 412 may be arranged so that nanostructures are periodically arranged on a line that satisfies the function form y = a ₁ *(-x) + a ₂ . Here, a ₁ and a ₂ may be any rational numbers.

The collimating metasurface 411, grating metasurface 412, focusing metasurface 413, and sensor 420 may be arranged three-dimensionally. The three-dimensional arrangement of the metasurface may mean that the lines connecting the centers of each metasurface provided in the spectrometer 400 form a three-dimensional shape. The spectrometer 400 including a three-dimensionally arranged metasurface can increase the length of the optical path relative to the volume, thereby improving spectral efficiency. For example, when the collimating metasurface 411 and the grating metasurface 412 are located close to one side of the transparent substrate 430, the focusing metasurface 413 and the sensor 414 face the one side. It can be placed closer to the other side.

The grating metasurface 412 may have substantially the same grating function as the grating metasurface 213 in FIG. 1 (213 in FIG. 2). However, in response to the three-dimensional arrangement of the metasurface, the optical path must also be formed three-dimensionally. Accordingly, the grating metasurface 312 and the focusing metasurface 313 may have a function of adding optical momentum that changes the direction of the incident light by, for example, 90 degrees in the horizontal direction when it is reflected. Light momentum is an expression that describes the straight motion of light from the perspective of inertia. For example, the grating metasurface 412 may include a pattern in which nanostructures are periodically arranged in a diagonal shape in the xy plane. For example, the grating metasurface 412 may be arranged so that nanostructures have periodicity along a line that satisfies the function form y = b ₁ * x + b ₂ . Here, b ₁ and b ₂ may be arbitrary real numbers.

Referring to FIG. 11, the spectrometer 400 viewed from the z-axis may have a collimating metasurface 411, a grating metasurface 412, a focusing metasurface 413, and a sensor 420 arranged in two dimensions. there is. For example, the collimating metasurface 411, the grating metasurface 412, the focusing metasurface 413, and the sensor 420 may be arranged in a square shape based on a view looking down on the z-axis. This is only one embodiment, and the collimating metasurface 411, grating metasurface 412, focusing metasurface 413, and sensor 420 have various shapes, such as circular and oval, based on the plane viewed from the z-axis. It can have any form of arrangement.

Figure 12 is a cross-sectional view schematically showing a spectrometer 500 according to another embodiment.

Referring to FIG. 12, the spectrometer 500 according to this embodiment includes a split metasurface 511, a first focusing metasurface 512, a second focusing metasurface 513, a first sensor 521, and a second sensor. It may include (522).

The split metasurface 511 may have both a polarizing beam splitter and a grating function. The split metasurface 511 can separate and reflect light into first polarization and second polarization in two opposite directions according to polarization, and separate the light to proceed in slightly different directions for each wavelength. The detailed configuration of the split metasurface 511 will be described later in FIGS. 13 and 14. The split metasurface 511 separates the light into first and second polarizations, decomposes the first polarization by wavelength and transfers it to the first focusing metasurface 512, and decomposes the second polarization by wavelength into the first polarization. 2 Transferred to the focusing metasurface 513. For example, the first polarization may be TE mode light, and the second polarization may be TM mode light. Or it could be the other way around.

Since the first focusing metasurface 512 and the second focusing metasurface 513 play substantially the same role as the focusing metasurface (111 in FIG. 1), detailed descriptions are omitted. The first focusing metasurface 512 can focus the first polarized light and transmit it to the first sensor 521. The second focusing metasurface 513 may focus the second polarized light and transmit it to the second sensor 522.

Since the first sensor 521 and the second sensor 522 are substantially the same as the sensor (120 in FIG. 1), detailed descriptions will be omitted.

The spectrometer 500 can separately spectralize light components according to polarization, and the spectral efficiency can be high due to the length of the light path compared to the volume.

Figure 13 is a diagram showing a split metasurface 511 according to another embodiment. FIG. 14 is a diagram showing the nanostructure pattern of the split metasurface 511 according to FIG. 13.

Referring to FIGS. 13 and 14, the split metasurface 511 includes a pattern including a plurality of nanostructures arranged so that the diameter in the x-axis direction increases and decreases, and the pattern includes the x-axis direction and the y-axis direction. It may be arranged to repeat periodically along the axial direction. The x-direction diameter and y-direction diameter of the plurality of nanostructures increase or decrease, respectively, and each plurality of nanostructures can control light in different polarization states due to the difference in diameter so that it is reflected and diffracted and emitted in opposite directions. For example, if the diameter of the cross section of the nanostructure in the y-axis direction is k ₀ , k ₁ , k ₂ , k _3, k ₄ , k ₅ , k ₆ , k _7, k ₈ , the diameter is It can gradually become longer from k ₀ to k ₅ and gradually become smaller from k ₆ to k ₈ .

The split metasurface 511 may separate light into first polarization and second polarization according to polarization and reflect the light in the x-axis direction. For example, the first polarized light may be reflected in the +x-axis direction and the second polarized light may be reflected in the -x-axis direction.

So far, exemplary embodiments of spectrometers incorporating nanostructures have been described and illustrated in the accompanying drawings to aid understanding of the present invention. However, it should be understood that these examples are merely illustrative of the invention and do not limit it. And it should be understood that the present invention is not limited to the description shown and illustrated. This is because various other modifications may occur to those skilled in the art.

100: spectrometer
110: meta surface
ns: nanostructure
sr: peripheral body
sub: substrate
120: sensor
130: transparent substrate
140: slit

Claims (19)

A transparent substrate including a first side and a second side facing each other;
a slit provided on the first surface and allowing light to be inspected to enter the transparent substrate;
Provided on the transparent substrate, it includes at least one metasurface including a plurality of two-dimensionally arranged nanostructures and a peripheral body surrounding the plurality of nanostructures, wherein the at least one metasurface is exposed through the slit. A spectroscopic optical system comprising a focusing metasurface that reflects and focuses incident light at different angles for each wavelength; and
a sensor provided on the transparent substrate and receiving light from the spectroscopic optical system; Including,
A spectrometer wherein the focusing metasurface is disposed on a second side of the transparent substrate, and the sensor is disposed on a first side of the transparent substrate. According to claim 1,
A spectrometer further comprising a blocking film disposed on the transparent substrate and blocking light from entering areas other than the slit. A transparent substrate including a first side and a second side facing each other;
a slit provided on the first surface and allowing light to be inspected to enter the transparent substrate;
Provided on the transparent substrate, it includes at least one metasurface including a plurality of two-dimensionally arranged nanostructures and a peripheral body surrounding the plurality of nanostructures, wherein the at least one metasurface is exposed through the slit. A spectroscopic optical system comprising a focusing metasurface that reflects and focuses incident light at different angles for each wavelength; and
A sensor provided on the transparent substrate and receiving light from the spectroscopic optical system,
The spectroscopic optical system,
A spectroscope further comprising a collimating metasurface having a plurality of nanostructures arranged two-dimensionally to have a collimating function. According to claim 3,
The collimating metasurface is,
A spectrometer located on the optical path between the slit and the focusing metasurface. According to claim 3,
The spectroscopic optical system,
A spectrometer further comprising a grating metasurface having a plurality of nanostructures arranged two-dimensionally to have a color dispersion function. According to claim 5,
The grating metasurface is,
A spectrometer located on an optical path between the collimating metasurface and the focusing metasurface. According to claim 5,
The grating metasurface and sensor are provided on the first surface,
The collimating metasurface and the focusing metasurface are provided on the second surface. According to claim 6,
On a plan view seen in a direction perpendicular to the first side,
A spectrometer in which the grating metasurface, collimating metasurface, focusing metasurface, and sensor are arranged two-dimensionally. According to claim 8,
The transparent substrate includes side surfaces connecting the first side and the second side,
On a plan view seen in a direction perpendicular to the first surface,
The collimating metasurface and the grating metasurface are closer to one of the sides,
The focusing metasurface and the sensor are arranged closer to the other side facing the one side. According to claim 1,
In the at least one metasurface,
A spectrometer in which the height of each of the plurality of nanostructures or the longest diameter in the cross section of the plurality of nanostructures is smaller than the wavelength of the light. A transparent substrate including a first side and a second side facing each other;
a slit provided on the first surface and allowing light to be inspected to enter the transparent substrate;
Provided on the transparent substrate, it includes at least one metasurface including a plurality of two-dimensionally arranged nanostructures and a peripheral body surrounding the plurality of nanostructures, wherein the at least one metasurface is exposed through the slit. A spectroscopic optical system comprising a focusing metasurface that reflects and focuses incident light at different angles for each wavelength; and
A sensor provided on the transparent substrate and receiving light from the spectroscopic optical system,
The spectroscopic optical system includes a grating metasurface,
The grating metasurface is,
Comprising a pattern including a plurality of nanostructures arranged at regular intervals in a second direction,
A spectrometer wherein the pattern is arranged to repeat periodically in a first direction perpendicular to the second direction. A transparent substrate including a first side and a second side facing each other;
a slit provided on the first surface and allowing light to be inspected to enter the transparent substrate;
It is provided on the transparent substrate and includes at least one metasurface including a plurality of two-dimensionally arranged nanostructures and a peripheral body surrounding the plurality of nanostructures, wherein the at least one metasurface is exposed through the slit. A spectroscopic optical system comprising a focusing metasurface that reflects and focuses incident light at different angles for each wavelength; and
A sensor provided on the transparent substrate and receiving light from the spectroscopic optical system,
The focusing metasurface is,
A spectrometer having one or more annular regions in which a plurality of nanostructures are arranged so that the cross-sectional area increases or decreases as the distance from a point on the focusing metasurface increases or decreases. A transparent substrate including a first side and a second side facing each other;
a slit provided on the first surface and allowing light to be inspected to enter the transparent substrate;
Provided on the transparent substrate, it includes at least one metasurface including a plurality of two-dimensionally arranged nanostructures and a peripheral body surrounding the plurality of nanostructures, wherein the at least one metasurface is exposed through the slit. A spectroscopic optical system comprising a focusing metasurface that reflects and focuses incident light at different angles for each wavelength; and
A sensor provided on the transparent substrate and receiving light from the spectroscopic optical system,
The spectroscopic optical system,
Further comprising a split metasurface configured to separate light into first polarization and second polarization according to polarization and to reflect the separated first polarization and second polarization by wavelength,
The sensor is a spectrometer including a first sensor provided to receive the separated first polarized light and a second sensor provided to receive the separated second polarized light. According to claim 13,
The focusing metasurface is,
A spectrometer comprising a first focusing metasurface for focusing the first polarized light to the first sensor and a second focusing metasurface for focusing the second polarized light to the second sensor. According to claim 13,
The split metasurface is,
Comprising a pattern including a plurality of nanostructures arranged so that diameter components in a first direction respectively increase and decrease,
A spectrometer wherein the pattern is arranged to repeat periodically along the first direction and a second direction perpendicular to the first direction. According to claim 1,
When the total length of the optical path from the slit to the sensor is L and the thickness of the transparent substrate is D, L and D satisfy the following relationship.
L/D > 3 According to claim 1,
A spectroscope in which the peripheral body is made of at least one material selected from the group consisting of silicon oxide (SiO ₂ ), glass, and polymer. According to claim 1,
The transparent substrate is a spectroscope made of at least one material selected from the group consisting of silicon oxide (SiO ₂ ), glass, and polymer. According to claim 1,
The plurality of nanostructures are a spectrometer made of at least one material selected from c-Si, a-Si, p-Si, GaP, GaAs, SiC, TiO2, SiN, and GaN.

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