Single-photon light source

Abstract

The present invention relates to a single-photon light source capable of generating single photons having a high repetition rate and light collection rate by positioning a light-emitting body in a nano-gap of a nano-antenna that includes metal nano-particles and a metal layer, and adjusting the Purcell enhancement of the nano-gap. The single-photon light source according to the present invention has a simple structure, is easy to manufacture, has a low manufacturing cost, and emits a single photon vertically upward through an optical antenna structure of a nano-antenna, thus having the advantage of an excellent light collection rate. In addition, the single-photon light source makes it possible to generate single photons by applying various light-emitting bodies to the nano-antenna, and has a broad bandwidth, thus having the advantages of a high production yield and being operable at room temperature across various wavelengths.

Description

single-photon light source

[0001] The present invention relates to a single-photon light source, and more particularly, to a single-photon light source capable of generating single photons with high repetition rate and concentration rate by positioning a light emitting body in a nano-gap of a nano-antenna including metal nanoparticles and a metal layer and controlling Purcell enhancement of the nano-gap.

[0002]

[0003] Recently, research on quantum information technology, including quantum cryptography and quantum computers, has been actively conducted worldwide.

[0004] In China, an independent satellite for quantum communications has been launched and quantum cryptography communication has been successfully performed using it, and a nationwide transmission network for quantum cryptography communication is also being built.

[0005] In Europe, the Quantum Technology Flagship project will be implemented for 10 years starting in 2018, and in the United States, the National Quantum Initiative program is being promoted, actively pursuing new large-scale research projects in addition to existing research.

[0006] Quantum cryptography research is also being conducted domestically and a national long-distance test transmission network has been established. However, there are many areas that need improvement, such as low transmission rates due to the lack of a desirable single-photon light source and inability to guarantee stability in long-distance transmission.

[0007] For application to real systems, a deterministic single-photon light source with suitable performance is required. However, there is currently no single-photon light source with practical potential, making system construction and testing difficult.

[0008]

[0009] The present invention has been devised to solve the above problems, and aims to provide a single-photon light source capable of generating single photons with high repetition rate and concentration rate by positioning a light emitting body in a nano-gap of a nano-antenna including metal nanoparticles and a metal layer and controlling Purcell enhancement of the nano-gap.

[0010]

[0011] A single photon light source according to one embodiment of the present invention comprises a nano-antenna including a metal layer formed on a substrate, metal nano-particles spaced apart from the metal layer, and a single light-emitting body positioned in a nano-gap between the metal nano-particles and the metal layer; and can be configured such that light is irradiated to the light-emitting body to generate a single photon and emit it through the nano-antenna.

[0012] Purcell enhancement can be controlled by controlling at least one of the size of the metal nanoparticles and the spacing of the nano gaps.

[0013] The above light source can be excited to generate a linearly polarized single photon.

[0014] The size of the above light-emitting body can be formed to be equal to or smaller than the spacing of the nano gap.

[0015] The nano-antenna is formed by a structure in which a first metal layer is formed on a substrate, a second metal layer having a hole formed in the center of the first metal layer is formed on the first metal layer, and the metal nano-particles are arranged on the upper portion of the first metal layer and inside the hole of the second metal layer, and the light-emitting body can be positioned in the nano-gap between the metal nano-particles and the inner wall surface of the hole of the second metal layer.

[0016] The above nanoantenna is formed by a structure in which a second metal layer having a hole formed in the center is formed on a substrate, and the metal nanoparticles are arranged on the upper part of the substrate and inside the hole of the second metal layer, and the light-emitting body can be positioned in a nano gap between the metal nanoparticles and the inner wall surface of the hole of the second metal layer.

[0017] The above nanoantenna has a structure in which a first metal layer is formed on a substrate and the metal nanoparticles are arranged on top of the first metal layer, and the light-emitting body can be positioned in a nano gap between the metal nanoparticles and the upper surface of the first metal layer.

[0018] The spacing of the above nano gaps can be configured to become narrower from top to bottom or from outside to inside.

[0019] The above light emitting body may be spherical in shape.

[0020] The above light emitting body may be in the form of a plate.

[0021] The above light-emitting body can be composed of a single colloidal quantum dot, a core / shell quantum dot, a diamond defect structure, a silicon defect structure, a two-dimensional semiconductor defect structure, or a nanoplatelet structure.

[0022] The above metal nanoparticles may be in a spherical shape.

[0023] The above metal nanoparticles may be in the shape of truncated spheres.

[0024] The above metal nanoparticles may be in the shape of a cylinder or polyhedron.

[0025] It may further include a support member that supports the metal nanoparticles, and may be configured with a structure in which the metal nanoparticles are settled on the support member.

[0026] It further includes a lens that entirely surrounds the metal nanoparticles, and the lens can focus the direction of single photons emitted from the metal nanoparticles vertically upward.

[0027] A coating layer may be formed on at least a portion of the surface of the nanoantenna.

[0028] The nano-antenna is formed with a structure in which a first metal layer is formed on a substrate, an insulating layer is formed on the first metal layer, a second metal layer having a hole formed in the center of the insulating layer is formed on the insulating layer, and the metal nano-particles are arranged on the upper portion of the insulating layer and inside the hole of the second metal layer, and the light-emitting body can be positioned in the nano-gap between the metal nano-particles and the inner wall surface of the hole of the second metal layer.

[0029]

[0030] The single-photon light source of the present invention has a simple structure, is easy to manufacture, has a low manufacturing cost, and has the advantage of excellent light collection efficiency by emitting single photons vertically upward through the optical antenna structure of the nano-antenna.

[0031] In addition, by applying various light-emitting materials to the nanoantenna, it is possible to generate single photons, and it has the advantage of having a wide bandwidth, high production yield, and operation at room temperature at various wavelengths.

[0032]

[0033] Figure 1 is a drawing for explaining the target performance of the single-photon light source of the present invention.

[0034] FIG. 2 is a drawing showing a single-photon light source according to an example of the present invention.

[0035] Figure 3 is electric field simulation data of the nano antenna of the present invention.

[0036] Figure 4 is FDTD simulation data showing the field size and wavelength according to the diameter of metal nanoparticles when the nano gap of the nanoantenna of the present invention is 6 nm.

[0037] Figure 5 is FDTD simulation data showing the size and wavelength of the field at each nano gap when the diameter of the metal nano-position of the nano-antenna of the present invention is 90 nm.

[0038] Figure 6 is simulation data showing the antenna efficiency of the nanoantenna of the present invention by wavelength.

[0039] Figure 7 is a graph comparing the luminescence intensity when the quantum dot is in a nano gap and the luminescence intensity when it is on a SiO2 layer.

[0040] Figure 8 is a graph comparing the luminescence lifetime when the quantum dot is in a nano gap and when it is on a SiO2 layer.

[0041] Figure 9 is a drawing showing various types of light-emitting bodies.

[0042] Figure 10 is a drawing showing various shapes of light-emitting bodies.

[0043] Figure 11 is a drawing showing various shapes of metal nanoparticles.

[0044] FIG. 12 is a drawing showing a nanoantenna according to a first example of the present invention.

[0045] FIG. 13 is a drawing showing a nanoantenna according to a second example of the present invention.

[0046] FIG. 14 is a drawing showing a nanoantenna according to a third example of the present invention.

[0047] FIG. 15 is a drawing showing a nanoantenna according to another example of the present invention.

[0048] FIG. 16 is a drawing showing a nanoantenna according to another example of the present invention.

[0049]

[0050] Hereinafter, the present invention will be described with reference to the attached drawings.

[0051] First, the present invention relates to a single-photon light source applicable to quantum cryptography. The present invention aims to provide an on-demand single-photon light source with excellent performance and practicality. More specifically, the present invention aims to realize a single-photon light source that generates single photons with high purity, brightness, and a high repetition rate at room temperature.

[0052] Figure 1 is a drawing for explaining the target performance of the single-photon light source of the present invention. An ideal single-photon light source satisfies the four conditions described above: operability at room temperature, high purity, high brightness, and high repetition rate. Brightness refers to the probability of a single photon being collected for use per single-photon request pulse. The present invention, for example, satisfies the condition [g (2) (0) < 0.05, η > 50%, Rate > 40 GHz] can be satisfied as the target performance.

[0053] To this end, the present invention secures a plasmonic nano-antenna with Purcell enhancement and maximized antenna efficiency, secures a single emitter suitable for the purpose, and implements a single-photon light source by fixing the single emitter at a desired location of the nano-antenna.

[0054] FIG. 2 is a drawing showing a single-photon light source according to an example of the present invention. The single-photon light source (100) of the present invention largely includes a nano-antenna (20) and a single light-emitting body (30).

[0055] A nanoantenna (20) is a plasmonic nanoantenna element including a metal layer (21) formed on a substrate (10) and metal nanoparticles (22) spaced apart from the metal layer (21), such that a nanogap (NG) is formed between the metal nanoparticles (22) and the metal layer (21). The substrate (10) serves as a support and may be a semiconductor or ceramic.

[0056] The metal layer (21) and metal nanoparticles (22) of the nanoantenna (20) generate surface plasmons and may be gold, platinum, silver, palladium, aluminum, copper, or a mixture or alloy thereof, and the metal layer (21) and metal nanoparticles (22) may be composed of the same or different metals.

[0057] A nano gap (NG) is formed between metal nanoparticles (22) spaced apart from the metal layer (21), and the interval of the nano gap (NG) can be formed to be approximately 10 nm.

[0058] A single light-emitting body (30) is positioned between a metal nanoparticle (22) and a metal layer (21), i.e., in a nano-gap (NG). The single light-emitting body (30) is a semiconductor crystal having a size of several to several tens of nanometers, and has discontinuous energy levels and gaps, so that it can emit light of a specific wavelength depending on the characteristics of the crystal. The single light-emitting body (30) may be a single quantum dot (QD), and the diameter of the light-emitting body (30) may be formed to be approximately 10 nm and positioned and fixed in the nano-gap (NG).

[0059] Precisely positioning the emitter at the nano-gap point where Purcell enhancement is highest is crucial for improving the performance of single-photon light sources. To achieve this, optical tweezers or suction techniques can be used to position emitters, such as quantum dots, at the nano-gap point where the electric field is strongest. It is desirable to align a single quantum dot along the dipole direction, where Purcell enhancement is greatest.

[0060] A local electric field is formed between the metal nanoparticles and the metal layer of the nanoantenna, i.e., in the nanogap, and LSPR (Localized Surface Plasmon Resonance) is generated. When light (ray), for example, a laser, is irradiated on a light-emitting body located in the nanogap, the light-emitting body is excited to generate a single photon (SP), and the generated single photon (SP) is emitted to the outside through the plasmonic nanoantenna. Fig. 3 is electric field simulation data of the nanoantenna of the present invention.

[0061] The LSPR can be controlled by controlling the gap between the metal nanoparticles and the metal layer, i.e., the nano gap, and the LSPR can be controlled by controlling the size of the metal nanoparticles (e.g., the diameter or width of the metal nanoparticles). More specifically, when the nano gap becomes smaller, the field becomes stronger and the LSPR wavelength increases, and when the size of the metal nanoparticles becomes larger, the LSPR wavelength increases. Fig. 4 is FDTD simulation data showing the field size and wavelength according to the diameter of the metal nanoparticles when the nano gap of the nanoantenna of the present invention is 6 nm, and Fig. 5 is FDTD simulation data showing the field size and wavelength according to the spacing of the nano gap when the diameter of the metal nanoparticles of the nanoantenna of the present invention is 90 nm.

[0062] Based on this, by controlling the LSPR by the size of the metal nanoparticles and the spacing of the nano-gap, the electric field generated at the resonant wavelength can be increased, the Purcell enhancement can be increased, and the luminescence efficiency of the light emitter can be further increased by matching the emission wavelength to the LSPR wavelength. That is, the degree of Purcell enhancement can be controlled by controlling the size of the metal nanoparticles and the spacing of the nano-gap so that the electric field intensity is maximized at the desired wavelength, and if the Purcell enhancement is large, the radiative recombination rate of the light emitter, for example, a quantum dot exciton, can be increased, which can significantly increase the single-photon repetition rate and greatly improve the indistinguishability. In addition, even if the luminescence quantum efficiency of the light emitter is low, the luminescence efficiency can be increased to almost 100% and the blinking phenomenon can be minimized by large Purcell enhancement.

[0063] Figure 6 is simulation data showing the antenna efficiency of the nanoantenna of the present invention by wavelength. Generally, most surface plasmon devices have high ohmic loss, which limits their performance. However, the present invention utilizes an efficient antenna structure, so that the surface plasmon is emitted as light before it disappears due to loss, thereby increasing the luminous efficiency and greatly increasing the brightness.

[0064] More specifically, the present invention is configured to have metal nanoparticles positioned at the center and spaced apart from the metal layer, thereby functioning as an optical antenna, thereby increasing luminous efficiency and narrowing the far-field radiation angle, thereby significantly enhancing the light collection rate of single photons, i.e., brightness. In this way, according to the present invention, the antenna quantum efficiency for converting plasmons into light can be maximized.

[0065] Figure 7 is a graph comparing the luminescence intensity when the quantum dot is in a nano gap with the luminescence intensity when it is on a SiO2 layer. The SiO2 layer can be positioned on a silicon substrate, and in Figure 7, when the quantum dot is on a silicon oxide layer, the luminescence intensity is so weak that it is multiplied by 50 to show it. As shown, it can be confirmed that the luminescence intensity of a single photon is significantly increased when the quantum dot is in a nano gap compared to when it is not.

[0066] Figure 8 is a graph comparing the luminescence lifetime when quantum dots are located in a nano-gap with that when they are located on a SiO2 layer. As shown, when quantum dots are placed in a nano-gap, the luminescence lifetime of single photons is significantly reduced due to the enhanced electric field, i.e., the luminescence rate is significantly increased. This is advantageous in improving the repetition rate of single photon light sources at room temperature.

[0067] The present invention utilizes Purcell enhancement to enhance single-photon generation, thereby eliminating the need for a resonator structure, unlike conventional single-photon light sources that require a resonator structure. Furthermore, the resulting emitted single photons are linearly polarized, allowing for easy laser filtering from the single photons.

[0068] FIG. 9 is a drawing showing various types of light-emitting bodies. The light-emitting body (30) of the present invention may be a single colloidal quantum dot as in (a) of FIG. 9, a core / shell quantum dot as in (b) of FIG. 9, a diamond NV center as in (c) of FIG. 9, or a nano-platelet as in (d) of FIG. 9.

[0069] As shown in (a) of Fig. 9, the light-emitting body (30) of the present invention may be composed of colloidal quantum dots, and in this case, the colloidal quantum dots may be CdSe single colloids.

[0070] As shown in (b) of Fig. 9, the light-emitting body (3) of the present invention may be composed of a core / shell quantum dot, and more specifically, may be composed of a colloidal single quantum dot composed of a core portion made of an inorganic material and a shell. Colloidal quantum dots have discontinuous energy levels that change depending on their size due to the quantum confinement effect.

[0071] These colloidal quantum dots can emit light at room temperature, so they can secure single photons at room temperature and have high purity characteristics. Colloidal quantum dots have a wide line width at room temperature, but a narrow line width at low temperatures. In the present invention, quantum dots having a narrow line width can be used by controlling the thickness of the cladding of core / shell quantum dots and improving the surface treatment. More specifically, the present invention can shorten the exciton lifetime by increasing the electron-hole overlap rather than the specific luminescence efficiency through the combination of surface treatment and cladding, and accordingly, quantum dots having high luminescence efficiency, no blinking, and improved performance can be used. For example, the present invention can be applied to core / shell quantum dots such as single CdSe, CdSe / ZnS, and other quantum dots such as InAs quantum dots, PbS quantum dots, and perovskite quantum dots can be applied.

[0072] As shown in (c) of Fig. 9, the light-emitting body of the present invention can be composed of a diamond defect structure, and more specifically, the light-emitting body of the present invention can be applied with a nano-diamond NV center, a nano-diamond Si-V center, or a nano-diamond Sn-V center having a size of about 10 nm.

[0073] In addition, the light-emitting body of the present invention can be composed of a silicon defect structure, and more specifically, the present invention can be applied to a silicon G center, a silicon W center, etc. as a light-emitting body.

[0074] In addition, the light-emitting body of the present invention can be composed of a defect structure of a two-dimensional semiconductor, and more specifically, the present invention can be applied as a light-emitting body, including various defect centers of BN, including defect centers of transition metal di-chalcogenide (TMDC), etc., in a plate shape made to a size that can enter a nano gap.

[0075] In addition, as shown in (d) of FIG. 9, the light-emitting body of the present invention can be configured as a nano-platelet structure, and more specifically, the present invention can be applied to CdSe nano-platelets or the like as the light-emitting body.

[0076] Fig. 10 is a drawing showing various shapes of a light-emitting body. The light-emitting body (30) can be configured in a spherical shape as shown on the left side of Fig. 10, or in a plate shape as shown on the right side of Fig. 10. As previously discussed, the diameter or width of such a light-emitting body can be formed to be equal to or smaller than the distance between the metal nanoparticles and the metal layer, i.e., the distance between the nano gaps, and can be positioned and fixed at one point of the nano gap.

[0077] Referring back to FIG. 2, the metal nanoparticles (22) may be configured in a spherical shape. More specifically, the metal nanoparticles may be configured in a spherical shape with a truncated bottom and configured in a structure in which they are mounted on a support (11) described later. Since this spherical shape is symmetrical in all directions with respect to the center, the size of the nano gap formed around the sphere is configured to be uniform throughout, and accordingly, an electric field is uniformly formed over the entire area on the nano gap, so that there is an advantage in that a constant performance can be secured regardless of where the light-emitting body is positioned in the nano gap.

[0078] Metal nanoparticles can have various shapes other than spherical ones. Fig. 11 is a drawing showing various shapes of metal nanoparticles. As shown, metal nanoparticles (22) can be formed in the shape of a cylinder or a prism, and can also be formed in the shape of a polyhedron.

[0079] Referring back to FIG. 2, the single-photon light source (100) of the present invention may further include a lens (40). The lens (40) may be, for example, a solid immersion lens, and may be configured to entirely surround the metal nanoparticles (22). The lens (40) may be composed of a low-refractive index polymer material or a dielectric material such as SiO2. The lens (40) may be configured to have a structure in which the interior is completely filled with a polymer, and thus the polymer may be interposed in the nano-gap (NG) or the space between the light-emitting body (30) and the metal nanoparticles (22). That is, the space of the nano-gap may be replaced with a polymer instead of air.

[0080] As shown, the lens (40) is formed in the shape of a roughly hemispherical dome or parabolic lens, and can vertically collect the direction of the single photons generated from the light emitter (30) and emitted through the metal nanoparticles (22), thereby further narrowing the far-field radiation angle of the single photons and increasing the light collection rate. In addition, by providing the lens (40), there is an advantage in that the structures inside, i.e., the metal nanoparticles (22) and the light emitter (30), etc., can be protected.

[0081] Below, the structure of a nanoantenna and a single-photon light source based thereon according to various embodiments of the present invention will be examined in more detail.

[0082] Fig. 12 is a drawing showing a nanoantenna according to a first example of the present invention, Fig. 13 is a drawing showing a nanoantenna according to a second example of the present invention, and Fig. 14 is a drawing showing a nanoantenna according to a third example of the present invention. The nanoantenna of Fig. 13 is the same as the nanoantenna of Fig. 2, but for the convenience of explanation, it will be described as the second example.

[0083] First, a nanoantenna according to a first example of the present invention will be examined. As shown in FIG. 12, the nanoantenna (20) of the present example includes a first metal layer (21-1) and a second metal layer (21-2) as metal layers (21). The first metal layer (21-1) is formed flat on a substrate (10), and the second metal layer (21-2) is formed on the first metal layer (21-1) and a hole (H) may be formed in the center. The first metal layer (21-1) and the second metal layer (21-2) may be composed of the same or different surface plasmon metals.

[0084] The first metal layer (21-1) may be arranged on the bottom with respect to the metal nanoparticles (22), and the second metal layer (21-2) may be arranged on the side or lower side with respect to the metal nanoparticles (22). The names of the first and second metal layers (21-1, 21-2) according to such shapes or arrangement structures will be applied equally to the metal layers of the second and third examples.

[0085] The nano-antenna (20) of this example is formed by a structure in which a first metal layer (21-1) is formed on a substrate (10), a second metal layer (21-2) having a hole (H) formed in the center is formed on the first metal layer (21-1), and metal nano-particles (22) are arranged on the upper part of the first metal layer (21-1) and inside the hole (H) of the second metal layer (21-2).

[0086] The metal nanoparticles (22) are spaced apart from the first metal layer (21-1) and are arranged on the upper portion of the first metal layer (21-1). To this end, the nanoantenna (20) may further include a support (11) that supports the metal nanoparticles (22), and may be configured in a structure in which the metal nanoparticles (22) are settled on the support (11). The support (11) may be formed by depositing silicon oxide to a certain thickness on the first metal layer (21-1), and after the metal nanoparticles (22) are formed, wet etching is performed to remove the remaining silicon oxide portion, leaving only the silicon oxide of the support (11).

[0087] In the nanoantenna (20) of this structure, a nanogap (NG) is formed between the metal nanoparticle (22) and the inner wall surface (E) of the hole (H) of the second metal layer (21-2), and a light-emitting body (30) is positioned in the nanogap (NG). The metal nanoparticle (22) is positioned at the center of the hole (H) of the second metal layer (21-2) and is spaced apart from the inner wall surface (E) of the hole (H) of the second metal layer (21-2), and accordingly, the nanogap (NG) is formed as a closed loop along the perimeter of the side surface of the metal nanoparticle (22), and the light-emitting body (30) can be positioned at one point of the nanogap (NG) formed as the closed loop. One side of the light-emitting body (30) can be in contact with the metal nanoparticle (22), and the other side can be in contact with the second metal layer (21-2).

[0088] The nano gap (NG) can be configured such that at least a portion thereof becomes narrower from top to bottom. This can be achieved by controlling the shape of the metal nanoparticles (22), the shape of the second metal layer (21-2), and the distance between the two. By configuring a portion of the nano gap (NG) to become narrower in this way, a light-emitting body (30) having a size similar to the spacing of the nano gap (NG) can be caught and fixed in the central portion of the nano gap (NG), which can be helpful in positioning a very small-scale light-emitting body (30) in the nano gap (NG).

[0089] Next, a nanoantenna according to a second example of the present invention will be described. As illustrated in FIG. 13, the nanoantenna (20) of the present example includes a second metal layer (21-2) as a metal layer (21). The second metal layer (21-2) may be formed on the substrate (10) and at the same time, a hole (H) may be formed in the center. The second metal layer (21-2) may be arranged on the side or lower side with respect to the metal nanoparticle (22).

[0090] The nano-antenna (20) of this example is formed by forming a second metal layer (21-2) with a hole (H) formed in the center on a substrate (10), and having a structure in which metal nano-particles (22) are arranged on the upper part of the substrate (10) and inside the hole (H) of the second metal layer (21-2).

[0091] The metal nanoparticles (22) are spaced apart from the substrate (10) and placed on the upper portion of the substrate (10). To this end, the nanoantenna (20) may further include a support (11) that supports the metal nanoparticles (22), and may be configured in a structure in which the metal nanoparticles (22) are settled on the support (11). The support (11) may be formed by depositing silicon oxide to a certain thickness on the first metal layer (21-1), and after the metal nanoparticles (22) are formed, wet etching is performed to remove the remaining silicon oxide portion, leaving only the silicon oxide of the support (11).

[0092] In the nanoantenna (20) of this structure, a nanogap (NG) is formed between the metal nanoparticle (22) and the inner wall surface (E) of the hole (H) of the second metal layer (21-2), and a light-emitting body (30) is positioned in the nanogap (NG). The metal nanoparticle (22) is positioned at the center of the hole (H) of the second metal layer (21-2) and is spaced apart from the inner wall surface (E) of the hole (H) of the second metal layer (21-2), and accordingly, the nanogap (NG) is formed as a closed loop along the perimeter of the side surface of the metal nanoparticle (22), and the light-emitting body (30) can be positioned at one point of the nanogap (NG) formed as the closed loop. One side of the light-emitting body (30) can be in contact with the metal nanoparticle (22), and the other side can be in contact with the second metal layer (21-2).

[0093] The nano gap (NG) can be configured such that at least a portion thereof becomes narrower from top to bottom. This can be achieved by controlling the shape of the metal nanoparticles (22), the shape of the second metal layer (21-2), and the distance between the two. By configuring a portion of the nano gap (NG) to become narrower in this way, a light-emitting body (30) having a size similar to the spacing of the nano gap (NG) can be caught and fixed in the central portion of the nano gap (NG), which can be helpful in positioning a very small-scale light-emitting body (30) in the nano gap (NG).

[0094] Next, a nanoantenna (20) according to a third example of the present invention will be described. As shown in FIG. 14, the nanoantenna (20) of this example includes a first metal layer (21-1) as a metal layer (21). The first metal layer (21-1) may be formed flat on a substrate (10). The first metal layer (21-1) may be arranged on the bottom with respect to the metal nanoparticles (22).

[0095] The nanoantenna (20) of this example is structured such that a first metal layer (21-1) is formed on a substrate (10) and metal nanoparticles (22) are arranged on top of the first metal layer (21-1).

[0096] The metal nanoparticles (22) are spaced apart from the first metal layer (21-1) and are arranged on the upper portion of the first metal layer (21-1). To this end, the nanoantenna (20) may further include a support (11) that supports the metal nanoparticles (22), and may be configured with a structure in which the metal nanoparticles (22) are settled on the support (11). The support (11) may be formed integrally with the substrate (10) and may be configured with a structure protruding upward from the substrate (10), and may be formed through etching of the substrate (10).

[0097] In the nanoantenna (20) of this structure, a nanogap (NG) is formed between the metal nanoparticle (22) and the upper surface of the first metal layer (21-1), and a light-emitting body (30) is positioned in the nanogap (NG). The metal nanoparticle (22) is spaced apart from the upper surface of the first metal layer (21-1), and accordingly, the nanogap (NG) is formed as a closed loop along the lower perimeter of the metal nanoparticle (22), and the light-emitting body (30) can be positioned at one point of the nanogap (NG) formed as the closed loop. One side of the light-emitting body (30) can be in contact with the metal nanoparticle (22), and the other side can be in contact with the first metal layer (21-1).

[0098] In this example, the nano gap (NG) can be configured such that at least some areas thereof become narrower from the outside to the inside. This can be implemented by controlling the shape of the metal nanoparticles (22), the thickness of the first metal layer (21-2), and the distance between the two. By configuring a portion of the nano gap (NG) to become narrow in this way, a light-emitting body (30) having a size similar to the spacing of the nano gap (NG) can be caught and fixed in the central portion of the nano gap (NG), which can be helpful in positioning a very small-scale light-emitting body (30) in the nano gap (NG).

[0099] In summary, the nanoantenna (20) of the first example includes both a first metal layer (21-1) formed on the bottom of a metal nanoparticle (22) as a metal layer (21) and a second metal layer (21-2) formed on the side of the metal nanoparticle (22), the nanoantenna (20) of the second example includes only a second metal layer (21-2) formed on the side of a metal nanoparticle (22) as a metal layer (21), and the nanoantenna (20) of the third example includes only a first metal layer (21-1) formed on the bottom of a metal nanoparticle (22) as a metal layer (21). The first example has an advantage over the second and third examples in that the radiation angle of a single photon emitted from the metal nanoparticle (22) is formed narrower, and the second and third examples have an advantage over the first example in that the structure is simpler and the manufacturing cost is lower, respectively.

[0100] Meanwhile, although not shown separately, in the nanoantenna (20) of FIGS. 12 to 14, the metal nanoparticles (22) may be formed in a columnar or polyhedral shape in addition to a spherical shape, and a single light-emitting body (30) may be applied in a spherical or plate shape, and a lens (40) surrounding the metal nanoparticles (22) may be further provided.

[0101] FIG. 15 is a drawing showing a nanoantenna according to another example of the present invention, and as shown, the present example may further include a coating layer (50). The coating layer (50) may be configured to entirely cover the surface of the nanoantenna (20), that is, the surface of the metal layer (21) and the metal nanoparticles (22). The coating layer (50) may be an insulator, such as an inorganic material such as Al2O3 or HfO, or an organic material such as PVA. The thickness of the coating layer (50) may be formed to be approximately 2 nm, and the coating layer (50) may prevent the light-emitting body (30) from directly contacting the metal nanoparticles (22) or the metal layer (21), and by controlling the thickness of the coating layer (50), the distance between the nano gaps (NG) may be reduced, thereby making it easy for the light-emitting body (30) to be fixed to the nano gaps (NG). Meanwhile, although not shown separately, this coating layer can be applied equally to various examples of nanoantennas, and of course, a lens (40) can also be applied together with the coating layer (50).

[0102] FIG. 16 is a drawing showing a nanoantenna according to another example of the present invention, and as shown, this example may further include an insulating layer (12). The insulating layer (12) may be made of a silicon oxide (SiO2) material, and this may be implemented in a manner such that only a portion of the support (11) is etched during the nanoantenna manufacturing process, so that SiO2 remains in areas other than under the support (11).

[0103] The single-photon light source of the present invention has a simple structure, so it is easy to manufacture and has a low production cost, and it has an excellent light collection rate by emitting single photons vertically upward through the optical antenna structure of the nanoantenna, and it is possible to generate single photons by applying various light-emitting materials to the nanoantenna, and it has the advantages of having a wide bandwidth, a high production yield, and being able to operate at room temperature and at various wavelengths.

[0104] While the embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. A nano-antenna including a metal layer formed on a substrate and metal nano-particles spaced apart from the metal layer; and A single light-emitting body positioned in a nano gap between the metal nanoparticles and the metal layer; The light is irradiated onto the above light-emitting body to generate a single photon and is configured to be emitted through the nano-antenna. Single photon source.

2. In paragraph 1, The Purcell enhancement can be controlled by controlling at least one of the size of the metal nanoparticle and the spacing of the nano gap. Single photon source.

3. In paragraph 1, The above light source is excited to generate a linearly polarized single photon. Single photon source.

4. In paragraph 1, The size of the above light-emitting body is formed to be equal to or smaller than the spacing of the nano gap. Single photon source.

5. In paragraph 1, The above nano antenna A first metal layer is formed on the substrate, A second metal layer having a hole formed in the center is formed on the first metal layer, It is formed with a structure in which the metal nano particles are arranged on the upper part of the first metal layer and inside the hole of the second metal layer, The above light-emitting body is located in the nano gap between the metal nanoparticle and the inner wall surface of the hole of the second metal layer. Single photon source.

6. In paragraph 1, The above nano antenna A second metal layer is formed on the substrate with a hole formed in the center, It is formed by a structure in which the metal nano particles are arranged on the upper part of the substrate and inside the hole of the second metal layer, The above light-emitting body is located in the nano gap between the metal nanoparticle and the inner wall surface of the hole of the second metal layer. Single photon source.

7. In paragraph 1, The above nano antenna A first metal layer is formed on the substrate, It is formed with a structure in which the metal nano particles are arranged on top of the first metal layer, The above light-emitting body is located in the nano gap between the metal nanoparticle and the upper surface of the first metal layer. Single photon source.

8. In paragraph 1, The spacing of the above nano gap is configured to become narrower from top to bottom or from outside to inside. Single photon source.

9. In paragraph 1, The above light source is spherical in shape, Single photon source.

10. In paragraph 1, The above light source is in the form of a plate. Single photon source.

11. In paragraph 1, The above light-emitting body is composed of a single colloidal quantum dot, a core / shell quantum dot, a diamond defect structure, a silicon defect structure, a two-dimensional semiconductor defect structure, or a nanoplatelet structure. Single photon source.

12. In paragraph 1, The above metal nanoparticles are spherical in shape. Single photon source.

13. In paragraph 1, The above metal nanoparticles are in the shape of truncated spheres. Single photon source.

14. In paragraph 1, The above metal nanoparticles are in the shape of a cylinder or polyhedron. Single photon source.

15. In paragraph 1, Further comprising a support member supporting the metal nanoparticles; A structure in which the metal nanoparticles are settled on the support member, Single photon source.

16. In paragraph 1, It further includes a lens that entirely surrounds the above metal nanoparticles; The above lens focuses the direction of single photons emitted from the metal nanoparticles vertically upward. Single photon source.

17. In paragraph 1, A coating layer is formed on at least a portion of the surface of the nano antenna. Single photon source.

18. In paragraph 1, The above nano antenna A first metal layer is formed on the substrate, An insulating layer is formed on the first metal layer, A second metal layer having a hole formed in the center is formed on the above insulating layer, It is formed with a structure in which the metal nano particles are arranged on the upper part of the insulating layer and inside the hole of the second metal layer, The above light-emitting body is located in the nano gap between the metal nanoparticle and the inner wall surface of the hole of the second metal layer. Single photon source.

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