Single-photon generator including metal nanoparticles having chiral structure and two-dimensional transition metal dichalcogenide layer and manufacturing method thereof

Abstract

The present invention relates to a single-photon generator and a manufacturing method thereof. Specifically, the single-photon generator may include metal nanoparticles having a chiral structure and a two-dimensional transition metal dichalcogenide monolayer, and emit circularly polarized single photons even without a separate external magnetic field or metamaterial. The single-photon generator of the present invention may generate a local magnetic field by utilizing the asymmetric electromagnetic field effect of chiral metal nanoparticles, and induce single-photon emission through local strain in a two-dimensional transition metal dichalcogenide monolayer coupled to the chiral metal nanoparticles. Accordingly, the single-photon emitter of the present invention can be implemented as a miniaturized quantum light source that generates single photons without requiring a strong magnetic field or a complex metamaterial, and thus can be applied to industrial fields such as quantum communication, quantum cryptography, and quantum computing.

Description

A single photon generator comprising metal nanoparticles having a chiral structure and a two-dimensional transition metal dichalcogenide layer, and a method for manufacturing the same

[0001] The present invention relates to a single photon generator, and specifically to a single photon generator comprising a metal nanoparticle having a chiral structure and a two-dimensional transition metal dichalcogenide layer, and a method for manufacturing the same.

[0002] This application is a priority application for Korean Patent Application No. 10-2024-0158282 filed on November 8, 2024 and Korean Patent Application No. 10-2025-0035465 filed on March 19, 2023, and all contents disclosed in the specifications and drawings of said applications are incorporated into this application by reference.

[0003] Meanwhile, the present invention was supported by the following national research and development projects.

[0004] Project ID: 1711200721

[0005] Assignment No.: 2021K1A3A32083826

[0006] Ministry Name: Ministry of Science and ICT

[0007] Project Management Agency: National Research Foundation of Korea

[0008] Research Project Name: Establishment of Foundation for International Cooperation

[0009] Research Project Title: Development of an Infrared Quantum Light Source Using Moire Excitons

[0010] Project Performing Organization Name: Seoul National University

[0011] Research Period: 2023.10.01~2024.09.30

[0012] Project ID: 2710006705

[0013] Assignment No.: II200841

[0014] Ministry Name: Ministry of Science and ICT

[0015] Project Management Agency: Ministry of Science and ICT

[0016] Research Project Name: Integration of Quantum Cryptography Communication and Advancement of Transmission Technology

[0017] Research Project Title: Development of Deterministic Quantum Optical Devices Combined with Optical Fibers / Integrated Optical Circuits

[0018] Project Executing Organization Name: Korea Advanced Institute of Science and Technology

[0019] Research Period: 2024.01.01~2024.12.31

[0020] A single-photon generator is a core quantum device in various quantum technologies, such as quantum communication, quantum cryptography, and quantum computing.

[0021] Although light emitted from a single-photon generator generally has linear polarization, converting it to circular polarization enables the efficient utilization of quantum information by using the photon's spin angular momentum (SAM).

[0022] Currently, various studies are underway to convert the polarization of a single photon, and representative methods include controlling the polarization state by applying a strong external magnetic field, and combining metamaterials or phase optics with a size of tens of micrometers.

[0023] Conventional single-photon polarization conversion methods require strong magnetic fields or large metamaterials, which increases system complexity and limits mass production and miniaturization. Magnetic fields induce electromagnetic interference, making stable quantum information processing difficult, while metamaterial-based methods face challenges in commercialization due to the need for precise nanofabrication technology and high costs.

[0024] Therefore, there is a need to develop technology capable of realizing miniaturized light sources that generate single photons without the need for separate external magnetic fields or complex metamaterials.

[0025] The problem that the present invention aims to solve is to provide a single photon generator that generates a single photon having a circularly polarized state without an external magnetic field or metamaterial.

[0026] Meanwhile, the technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by a person skilled in the art from the description below.

[0027] The present invention may include a single photon generator comprising: a metal nanoparticle having a chiral structure; and a two-dimensional transition metal dichalcogenide layer covering the metal nanoparticle.

[0028] The above single photon generator may be characterized by emitting a circularly polarized single photon without a separate external magnetic field.

[0029] The above two-dimensional transition metal dichalcogenide layer may be a single layer.

[0030] The above two-dimensional transition metal dichalcogenide may be at least one selected from molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2), tungsten diselenide (WSe2), and combinations thereof.

[0031] The metal nanoparticles having the above chiral structure may be coated with silica nanoparticles.

[0032] The structure of the metal nanoparticle having the above chiral structure may have an asymmetric (chirality) three-dimensional nanostructure including a plurality of vertices and nanogaps on its interior or surface.

[0033] An electric dipole light source placed at the above vertex induces an instantaneous induced current (J) through the plasmon resonance effect. d ) and retarded induced current (J r Forming ),

[0034] The above delayed induction current (J r ) is a strong circular current and magnetic field (H) in the nanogap region ⊥ By inducing ), a circularly polarized single photon can be generated.

[0035] The photon emitted from the above single photon generator may show a larger absolute value of the Stokes parameter S3 compared to the case where metal nanoparticles of an anachiral structure under the same conditions are applied.

[0036] The absolute value of the Stokes parameter S3 of the photon emitted from the above single photon generator may be 0.3 or greater and 1 or less.

[0037] The photon emitted from the above single-photon generator is g measured at a temperature of 4K using an HBT (Hanbury Brown-Twiss) interferometer 2 (0) The value may be less than 0.5.

[0038] The polarization state of the photon emitted from the above single photon generator may be characterized by polarization characteristics that change depending on the change in the azimuthal angle of the electric dipole light source.

[0039] The photon emitted from the above single photon generator may be capable of quantum information transmission as it is encoded with spin angular momentum.

[0040] In addition, the present invention comprises a single photon generator comprising metal nanoparticles having a chiral structure and a two-dimensional transition metal dichalcogenide layer covering the metal nanoparticles; and

[0041] A conductive substrate comprising a plurality of the above single photon generators arranged in a periodic or non-periodic pattern;

[0042] The above single photon generator emits a circularly polarized single photon without a separate external magnetic field, and

[0043] The above plurality of single photon generators may include a multi-array single photon generating element characterized by each acting as an individual single photon source.

[0044] In addition, the present invention comprises the step of preparing metal nanoparticles having a chiral structure (S01);

[0045] A step of coating silica on the surface of the metal nanoparticles having the above chiral structure (S02); and

[0046] The method comprises the step (S03) of bonding a two-dimensional transition metal dichalcogenide layer to the surface of the silica-coated metal nanoparticles having a chiral structure, and

[0047] A method for manufacturing a single photon generator may be included, characterized by emitting a single photon that is circularly polarized without a separate external magnetic field.

[0048] After step S02 and before step S03, the method may further include a step (S04) of arranging the silica-coated metal nanoparticles having a chiral structure on a conductive substrate in a periodic or non-periodic pattern.

[0049] The single photon generator according to the present invention utilizes the asymmetric electromagnetic field effect of chiral metal nanoparticles to form a local magnetic field and can induce the emission of a single photon through local strain of a two-dimensional transition metal dichalcogenide monolayer coupled with chiral metal nanoparticles. Therefore, a miniaturized quantum light source capable of generating a single photon without a strong magnetic field or complex metamaterials can be realized, and this can be applied in industrial fields such as quantum communication, quantum cryptography, and quantum computing.

[0050] Meanwhile, the effects of the present invention are not limited to those mentioned above, and other unmentioned technical effects will be clearly understood by a person skilled in the art from the description below.

[0051] FIG. 1 is a schematic diagram showing the structure of a single photon generator according to one embodiment of the present invention.

[0052] FIG. 2 is a scanning electron microscope (SEM) image of silica-coated chiral gold nanoparticles prepared according to Example 1-2 of the present invention (scale bar 200 nm).

[0053] FIG. 3 is a scanning electron microscope (SEM) image (Tilted-view, inset: top view) of chiral gold nanoparticles bonded with a tungsten diselenide (WSe2) monolayer according to Examples 1-3 of the present invention.

[0054] FIG. 4 is a schematic diagram showing the fabrication process of a multi-array single-photon generating device according to one embodiment of the present invention.

[0055] FIGS. 5 and 6 are the results of confirming whether single photon generation occurs for chiral gold nanoparticles coupled with a tungsten diselenide (WSe2) monolayer according to an embodiment of the present invention, showing (a) a photoluminescence (PL) spectrum (inset: emission intensity curve as a function of laser pump power) and (b) a time correlation function g of single photon emission.2 (τ) is.

[0056] FIGS. 7 to 14 are the results of analyzing the circular polarization characteristics of chiral gold nanoparticles combined with a tungsten diselenide (WSe2) monolayer according to one embodiment of the present invention.

[0057] FIGS. 15 to 19 are the results of measuring the circular polarization characteristics of a gold nanoparticle structure with an achiral structure bonded to a tungsten diselenide (WSe2) monolayer according to Comparative Example 1 of the present invention.

[0058] FIGS. 20 to 24 are the results of a theoretical analysis of the mechanism by which chiral gold nanoparticles (cNP) according to an embodiment of the present invention emit a circularly polarized single photon, wherein (FIS. 20) a current (J) generated inside the chiral gold nanoparticles r ,J d Schematic diagram illustrating the process of ) and dipole formation, (Fig. 21) magnetic field (H induced in chiral gold nanoparticles) ⊥ As a result of simulating the distribution, (Fig. 22) shows the change in Stokes parameters (S1, S2, S3) according to the dipole direction () and (Fig. 23) shows the elliptical polarization state at = 0° and (Fig. 24) = 90°.

[0059] Detailed information regarding the purpose, technical configuration, and resulting effects of the present invention will be more clearly understood through the following detailed description based on the drawings attached to the specification of the present invention. An embodiment according to the present invention will be described in detail with reference to the attached drawings.

[0060] The embodiments disclosed herein should not be interpreted or used to limit the scope of the invention. It is obvious to those skilled in the art that the description including the embodiments herein has various applications. Accordingly, any embodiments described in the detailed description of the invention are illustrative for better explaining the invention and are not intended to limit the scope of the invention to the embodiments.

[0061] As used in the specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0062]

[0063] single photon generator

[0064] The present invention relates to a single-photon emitter (SPE) characterized by generating circular polarization without a separate external magnetic field.

[0065]

[0066] The structure of a single photon generator according to one embodiment of the present invention is schematically shown in FIG. 1, and will be described in detail below.

[0067]

[0068] A single-photon state refers to a state limited to the existence of only one photon at a specific moment, and a single-photon light source does not emit two or more photons simultaneously. The Single-Photon Emitter (SPE) of the present invention refers to a light source that emits only one photon (light particle) at a time.

[0069]

[0070] The single photon generator (SPE) of the present invention comprises a metal nanoparticle having a chiral structure and a two-dimensional transition metal dichalcogenide layer covering the metal nanoparticle. Specifically, the single photon generator of the present invention is in the form in which a two-dimensional transition metal dichalcogenide monolayer is bonded to the surface of a metal chiral nanoparticle (cNP).

[0071]

[0072] The above chiral metal nanoparticle (cNP) is based on a polyhedral shape and contains a chiral three-dimensional nanostructure on its surface and inside. The chiral metal nanoparticle contains multiple vertices and nanogap regions on its surface. Due to the existence of this structural chirality, when electromagnetic waves (incident light sources) interact with the nanoparticle, the induced current does not flow uniformly but is distributed with a specific directionality.

[0073]

[0074] The surface of the aforementioned chiral metal nanoparticles includes multiple vertex regions. Due to the asymmetric structure of the nanoparticles, the local field enhancement effect is increased at the vertex regions. When an electric dipole light source is placed in these vertex regions, it interacts with plasmon resonance to become a key location that determines the polarization state of a single photon.

[0075]

[0076] In addition, multiple nanogaps are formed on the surface of the chiral metal nanoparticles. Specifically, the metal nanoparticles having the chiral structure contain 12 nanogaps. A nanogap refers to a narrow gap at the level of several nanometers (nm), and strong localized field enhancement between metals can be induced. Specifically, the instantly induced current (J d ) and retarded induced current (J r ) occurs simultaneously. As a result, a strong circulating current is formed around the nanogap, and a local magnetic field (H) inside the chiral metal nanoparticles ⊥ It induces ). As a result, this magnetic field promotes plasmon-exciton coupling by binding a two-dimensional transition metal dichalcogenide layer to the surface of the chiral metal nanoparticles, and can control the polarization state of light even without an external magnetic field.

[0077]

[0078] In particular, the metal nanoparticles having the above chiral structure possess a subwavelength size and, specifically, can induce a specific current flow and magnetic field formation despite the nanoparticle size being relatively small compared to the wavelength (λ) of the light used. Generally, if the nanoparticle size is smaller than the wavelength, interaction with electromagnetic waves is limited; however, the chiral metal nanoparticles of the present invention utilize the chiral three-dimensional shape and the plasmon resonance effect in the nanogap to induce an instantly induced current (J d ) and delayed induced current (J rIt simultaneously forms ). In particular, near the nanogap, a circulating current is induced due to the local field enhancement effect, and in this process, a local magnetic field (H ⊥ A ) is formed, and as a result, circularly polarized single-photon emission becomes possible. In anachiral metal nanoparticles (e.g., anachiral metal nanocubes), such a current pattern is not formed, so the circular polarization component is low, but chiral metal nanoparticles can exhibit a much higher degree of circular polarization (DOCP) compared to anachiral structures by maintaining delayed-induced current flow in the nanogap.

[0079]

[0080] In addition, when a two-dimensional transition metal dichalcogenide layer is covered on the surface of the chiral metal nanoparticles, strain relaxation occurs in the nanogap region, which can control the optical response and single-photon emission characteristics.

[0081]

[0082] The chiral metal nanoparticles mentioned above may be made of a material having excellent plasmon resonance properties, and may be, for example, at least one selected from gold (Au), silver (Ag), copper (Cu), and alloys thereof, and preferably may be gold (Au).

[0083]

[0084] The surface of the above chiral metal particles can be prepared in a form coated with silica (SiO2) nanoparticles. As a transparent dielectric material, silica not only minimizes light scattering and absorption but also protects the metal nanoparticles from external environments, such as oxidation or ionic reactions in solution, thereby maintaining structural stability over the long term. Furthermore, the silica coating serves to maintain the original chiral structure of the nanoparticles and protects the geometric characteristics of specific nanostructures.

[0085]

[0086] The above two-dimensional transition metal dichalcogenide (TMD) layer is a monolayer semiconductor thin film that covers and binds the metal nanoparticles having the chiral structure. Specifically, the two-dimensional transition metal dichalcogenide (TMD) may be at least one selected from molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2), tungsten diselenide (WSe2), and combinations thereof. In particular, a tungsten diselenide (WSe2) monolayer can be preferably used, and tungsten diselenide (WSe2) has characteristics of a direct bandgap (~1.65 eV, 740 nm) and strong spin-orbit coupling, and is a material suitable for single-photon emission (SPE) applications, as it is capable of forming excitons by photoexcitation by an external light source, such as a 532 nm pumping laser.

[0087]

[0088] In addition, the above-mentioned two-dimensional transition metal dichalcogenide (TMD) monolayer has an atomic-level thickness (about ~0.7 nm), so it has the characteristic of being able to flexibly deform according to the shape of the underlying structure when placed on chiral metal nanoparticles. When placed on the surface of nanoparticles having complex three-dimensional structures such as curvature, nanogaps, and vertices, it can undergo physical strain depending on the shape of the nanostructure. Specifically, depending on the chiral surface structure of the chiral metal nanoparticles, a strain coupling effect with the two-dimensional transition metal dichalcogenide (TMD) monolayer occurs, and specifically, strain enhancement in the form of elongation may occur in some regions, or strain relaxation in the form of crumpling may occur in other regions. For example, at the vertex regions of chiral metal nanoparticles, the two-dimensional transition metal dichalcogenide (TMD) monolayer faces relatively large changes in curvature, which can lead to increased local strain enhancement. On the other hand, at the nanogap regions, strain relaxation may occur in which the TMD monolayer is compressed due to the narrow gap. In other words, the chiral three-dimensional surface structure of the chiral metal nanoparticles can induce complex strain coupling that is not induced in TMD monolayers placed on conventional flat substrates, thereby strengthening plasmon-exciton coupling between the TMD monolayer and the chiral metal nanoparticles and leading to the appearance of circular polarization characteristics of single photons.

[0089]

[0090] The polarization characteristics and the dominance of the circular polarization component of the photon emitted from the single-photon generator of the present invention can be evaluated through the value of the Stokes parameter S3, which is a parameter that quantitatively represents the polarization component of light. The S3 value is a parameter that quantitatively represents the circular polarization component (Left Circular Polarization, LCP or Right Circular Polarization, RCP) of the emitted photon. If S3 > 0, it means that RCP (right circular polarization) is dominant, and if S3 < 0, it means that LCP (left circular polarization) is dominant; furthermore, the closer the S3 value is to 0, the closer the polarization of the photon is to a linearly polarized (LP) or unpolarized state. Since anachiral structures (e.g., gold nanocubes) have a symmetrical shape, the induced current generated by plasmon resonance does not have a specific directionality. That is, since the current flow is formed symmetrically overall, the local magnetic field (H⊥) is not formed asymmetrically, and as a result, a single photon with almost no circular polarization component is emitted. Therefore, when non-chiral metal nanoparticles are applied, the polarization of the single photon is close to linear polarization, and the S3 value is close to 0, so there is almost no circular polarization component. On the other hand, the chiral metal nanoparticles of the present invention can emit a circularly polarized single photon due to the circular current and local magnetic field effects generated at the nanogap and vertex, and the circular polarization component of the emitted photon increases, resulting in a larger S3 value.

[0091] For example, the S3 value of a photon emitted from the single photon generator of the present invention may be 0.3 or greater and 1 or less in absolute terms. In one embodiment, the polarization state of a photon emitted from the single photon generator of the present invention is such that the polarization characteristics change according to the change in the azimuthal angle (θ) of the electric dipole light source, so that when the azimuthal angle (θ) changes, the S3 value may increase to a level of approximately ±0.8 when the chiral metal nanoparticles of the present invention are applied. When θ = 0°, the S3 value is approximately -0.8, indicating that LCP (left circular polarization) is dominant; when θ = 90°, the S3 value is approximately +0.8, indicating that RCP (right circular polarization) is dominant; and when θ = 45°, the S3 value is close to 0, indicating that linear polarization is dominant. On the other hand, even when the value changes, the S3 value approaches 0, and circular polarization is not generated. That is, the photon emitted from the single photon generator of the present invention may be characterized by having a larger absolute value of the Stokes parameter S3 compared to the case where metal nanoparticles of an achiral structure under the same conditions are applied.

[0092]

[0093] To evaluate the characteristics of photons emitted from the single-photon generator of the present invention, the correlation function g of the photons was used with a Hanbury Brown-Twiss (HBT) interferometer. 2 The value of (τ) can be measured. g 2 (0) The value is a key indicator for determining whether a photon has single-photon properties and is generally interpreted as follows.

[0094] g 2 If (0) > 1, a classical light source (coherent light source), e.g., a laser

[0095] g 2 When (0)=1, a semiclassical light source that follows Poissonian statistics, e.g., thermal light

[0096] g 2 (0) < 1, correlated light source

[0097] g 2 (0) < 0.5, a light source with strong single-photon properties that has a low probability of multi-photon emission and exhibits antibunching.

[0098] g 2 When (0)=0, the perfect single-photon source

[0099] The photon emitted from the single photon generator of the present invention is g in a cryogenic environment of 4K using an HBT interferometer 2 (0) When the value was measured, it was found to have a value of less than 0.5. This means that the light source is not a semiclassical light source such as a general thermal light or laser that exhibits bunching effects, but a quantum light source in which multiphoton emission is suppressed, and a single photon light source that exhibits antibunching characteristics.

[0100]

[0101] In summary, the single-photon generator of the present invention has a structure in which a two-dimensional transition metal dichalcogenide (WSe2) monolayer is combined with chiral metal nanoparticles, and single-photon emission is induced by local strain and plasmon-exciton coupling effects formed in this structure. In particular, local exciton states formed by specific defect states or strain sites in the WSe2 monolayer act as key factors inducing single-photon emission. In addition, the localized surface plasmon resonance (LSPR) effect of the chiral metal nanoparticles is combined to control the single-photon emission characteristics and increase the circular polarization component.

[0102]

[0103] Therefore, the combination of the chiral metal nanoparticles and the two-dimensional transition metal dichalcogenide monolayer of the present invention can impart unique optical and electromagnetic properties based on local mechanical deformation and plasmon-exciton coupling, going beyond the concept of simple physical covering. Through this, it can be used as a single-photon generator capable of circularly polarized single-photon emission with a specific directionality (SAM-Encoded Single-Photon Emission) without a separate external magnetic field.

[0104]

[0105] Method for manufacturing a single photon generator

[0106] The method for manufacturing a single photon generator of the present invention may first perform the step (S01) of preparing metal nanoparticles having a chiral structure.

[0107] Specifically, chiral gold nanoparticles (cNPs) are formed by controlling growth solution conditions and precursor composition, and can form chiral three-dimensional nanostructures based on octahedral or polyhedral structures. For example, chiral gold nanoparticles can be synthesized by preparing a growth solution by combining compounds such as ammonium hexavalent bromide (CTAB) surfactant, a gold precursor (HAuCl4), a reducing agent (L-ascorbic acid), and a chiral agent (L-glutathione), and inducing the growth of seed nanoparticles within this solution. Subsequently, impurities are removed through centrifugation and washing, and the chiral gold nanoparticles are redispersed in a 1 mM CTAB solution to be prepared for use in subsequent processes.

[0108]

[0109] Next, a step (S02) of coating silica on the surface of the metal nanoparticles having the chiral structure may be performed. The silica coating can be applied using a sol-gel method with tetraethyl orthosilicate (TEOS), and by controlling the coating thickness, it can prevent structural deformation of the nanoparticles and prevent aggregation between the nanoparticles.

[0110]

[0111] Additionally, a step (S03) of bonding a two-dimensional transition metal dichalcogenide layer to the surface of the silica-coated metal nanoparticles having a chiral structure may be performed. The two-dimensional transition metal dichalcogenide (TMD) may be, for example, at least one selected from molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2), tungsten diselenide (WSe2), and combinations thereof. A TMD in the form of a single layer may be prepared through mechanical exfoliation or chemical vapor deposition (CVD). In step S03, the method of bonding the two-dimensional transition metal dichalcogenide single layer onto the metal nanoparticles may be performed by a method including, for example, wet transfer, dry transfer, or atomic layer deposition (ALD).

[0112]

[0113] After step S02 and before step S03, a step (S04) of arranging the silica-coated metal nanoparticles having a chiral structure in a periodic or non-periodic pattern on a conductive substrate may be further performed. A fine nanohole pattern may be formed on a silicon (Si) substrate, and chiral gold nanoparticles may be aligned to the pattern through DIP coating or a mechanical friction method. After pattern alignment, the chiral gold nanoparticles are stably fixed through chemical surface modification (Aminosilane treatment). A single-photon generating device having a large-scale array can be fabricated by combining it with a transferred TMD monolayer in the subsequent step S03.

[0114]

[0115] The fabricated single-photon generator can emit single photons by an excited-by-laser method using an external laser with a wavelength of 532 nm. For example, a WSe2 monolayer absorbs laser light to form an exciton, and a circularly polarized single photon is emitted through interaction with chiral gold nanoparticles. In particular, due to the chiral structure of the chiral gold nanoparticles, circularly polarized (LCP or RCP) single photons with specific directionality can be generated. Furthermore, a large-scale quantum light source array can be formed through multiple arrays of single-photon generators.

[0116]

[0117] The single-photon generator of the present invention and the single-photon generating device including the same can be utilized as a quantum light source and a single-photon emitter or single-photon generator, and can be applied to advanced technologies such as quantum communication, quantum computing, and chiral optical sensors.

[0118]

[0119]

[0120] Below, specific embodiments and experimental examples of the present invention are examined.

[0121]

[0122] Example 1. Single photon generator comprising chiral gold nanoparticles and a two-dimensional transition metal dichalcogenide layer

[0123] Example 1-1. Synthesis of chiral gold nanoparticles (cNP; chiral Au nanoparticle) (S01)

[0124] 1) A growth solution is prepared by sequentially adding 0.8 mL of 0.1 M cetyltrimethylammonium bromide (CTAB) solution, 0.2 mL of 0.01 M gold precursor (HAuCl4) solution, 0.475 mL of 0.1 M L-ascorbic acid (AA) solution, and 5 μL of 5 mM L-glutathione (L-GSH) solution to 3.95 mL of DI water (Deionized water).

[0125] 2) 25 μL of seed nanoparticles (e.g., octahedron nanoparticles) were added to the growth solution and mixed, and the mixture was reacted in a water bath at 30°C for 2 hours to form a chiral structure. As the nanoparticles continued to grow, the color of the growth solution changed from a transparent purple to a navy color accompanied by large scattering.

[0126] 3) After the reaction, the solution was centrifuged (1677 g, 1 min) to obtain chiral gold nanoparticles (cNP), and the remaining reaction product was removed by washing twice with 1 mM CTAB solution. The synthesized chiral gold nanoparticles were redispersed in CTAB (1 mM) for further use.

[0127]

[0128] Example 1-2. Silica coating (S02) on the surface of chiral gold nanoparticles (cNP)

[0129] 1) Add mPEG-SH (Methoxy polyethylene glycol Thiol; 0.25 mM, 0.3 mL) to 10 mL of a 1 mM cetyltrimethylammonium bromide (CTAB) solution mixed with the prepared cNP, and mix using a stirrer at a speed of 800 rpm for 30 minutes. This process stabilizes the surface of the cNP to prevent aggregation from occurring during the silica coating process.

[0130] 2) Centrifuge the solution (1677 g, 1 min) to obtain chiral gold nanoparticles (cNP), and wash twice with absolute ethanol (EtOH) to remove any remaining reaction products.

[0131] 3) To 1.2 mL of nanoparticles coated with mPEG-SH from the above process, 1 mL of DI water, 2.3 mL of EtOH, and 90 μL of ammonia water (NH4OH; 2 M ethanol solution) are added, and tetraethyl orthosilicate (TEOS; 5 vol % in IPA) is slowly injected. The mixed solution is stirred using a stirrer at 800 rpm for 2 hours.

[0132] 4) After the reaction, the solution is centrifuged (1677 g, 1 min) to obtain silica-coated chiral gold nanoparticles (silica-coated cNPs), the centrifuged nanoparticles are washed twice with ethanol to remove remaining impurities, and finally redispersed in ethanol for storage.

[0133]

[0134] Example 1-3. Bonding of a tungsten diselenide (WSe2) monolayer (S03)

[0135] 1) Tungsten diselenide (WSe2) bulk is mechanically exfoliated using blue tape (DN-280) to obtain a single layer of WSe2.

[0136] 2) Attach the exfoliated WSe2 monolayer to the PDMS (Polydimethylsiloxane) stamp.

[0137] 3) Precisely position the WSe2 monolayer attached to the PDMS stamp on a substrate on which chiral gold nanoparticles are arranged, and carefully press to transfer the WSe2 monolayer onto the nanoparticle array.

[0138] At this time, localized tensile strain is generated in the WSe2 monolayer due to the structure of the chiral gold nanoparticles, making it possible to generate a single photon at a specific defect location.

[0139]

[0140] Example 1-4. Fabrication of a multi-array single-photon generating device (S04)

[0141] FIG. 4 is a schematic diagram showing the fabrication process of a multi-array single-photon generating device according to one embodiment of the present invention.

[0142] Referring to Fig. 4, the fabrication process of a large-scale two-dimensional array substrate of a multi-array single-photon generating device (cNP) can be observed.

[0143] First, a pattern of circular nano-holes with a diameter of 200 nm and a depth of 2 μm is formed on a silicon (Si) substrate, the surface of the substrate is deactivated by treating it with a trichlorosilane compound, and chiral gold nanoparticles coated with silica are inserted into the nano-pattern through dip coating and mechanical friction (Fig. 4(a)).

[0144] Subsequently, the SiO2 substrate is immersed for 1 hour in a solution of 3-aminopropyltriethoxysilane (APTES) diluted in ethanol to a concentration of 1 vol% to form amine functional groups. This chemically bonds with the silica coating layer of the nanoparticles, enabling the nanoparticles to be stably immobilized. The nanoparticles arranged on the patterned PDMS substrate are transferred to the APTES-treated SiO2 substrate to form a chiral gold nanoparticle array with a spacing of 2 μm (Fig. 4(b)).

[0145] Next, a WSe2 monolayer is transferred onto the cNP array in the same manner as the bonding process of the tungsten diselenide (WSe2) monolayer described in Example 1-3 above to fabricate a multi-array single-photon generating device (Fig. 4(c~d)).

[0146]

[0147] A single photon can be obtained by pumping the multi-array single photon generator fabricated as described above with a laser of 532 nm wavelength. When the laser stimulates the WSe2 monolayer, a single photon is generated and interacts with chiral gold nanoparticles.

[0148]

[0149] For the practical application of multi-array single-photon generating devices in quantum information and communication, it is important to precisely control the position of single-photon emitters and accurately adjust their optical properties. To this end, a multi-array structure in which a two-dimensional array of chiral metal nanoparticles (cNPs) with a fixed-pitch pattern, such as 8 mm x 8 mm, is fabricated and a WSe2 monolayer is transferred thereon can be preferably used. This method ensures spatial uniformity of individual single-photon sources and increases precision during the fabrication process, thereby maintaining uniform performance of all single-photon emitters within the array. Since each location where a chiral gold nanoparticle is combined with a tungsten diselenide (WSe2) monolayer is situated acts as an individual single-photon source, enabling the realization of consistent single-photon generators in large-scale arrays, it is expected to serve as a key element for constructing high-reliability quantum light sources and large-scale quantum networks in various quantum applications such as quantum communication and quantum computing.

[0150]

[0151]

[0152] Experimental Example 1. Confirmation of Microstructure

[0153] FIG. 2 is a scanning electron microscope (SEM) image of silica-coated chiral gold nanoparticles prepared according to Example 1-2 of the present invention (scale bar 200 nm).

[0154] Referring to Fig. 2, it can be seen that gold nanoparticles with a chiral structure and a uniformly formed silica (SiO2) coating maintain their unique chiral shape. Additionally, it can be seen that individual nanoparticles are distributed independently without aggregating with each other.

[0155]

[0156] FIG. 3 is a scanning electron microscope (SEM) image (Tilted-view, inset: top view, scale bar: 200 nm) of chiral gold nanoparticles bonded with a tungsten diselenide (WSe2) monolayer according to Examples 1-3 of the present invention.

[0157] Referring to Fig. 3, a structure in which the actual fabricated chiral gold nanoparticles and WSe2 monolayer are combined can be confirmed using a scanning electron microscope (SEM), and a shape in which the WSe2 monolayer covers along the surface of the chiral gold nanoparticles can be confirmed.

[0158]

[0159]

[0160] Experimental Example 2. Verification of single photon generation

[0161] FIGS. 5 and 6 are the results of confirming whether single photon generation occurs for chiral gold nanoparticles coupled with a tungsten diselenide (WSe2) monolayer according to an embodiment of the present invention, showing (a) a photoluminescence (PL) spectrum (inset: emission intensity curve as a function of laser pump power) and (b) a time correlation function g of single photon emission. 2 (τ) is.

[0162] Referring to Figures 5 and 6, single-photon emission characteristics can be confirmed through the PL spectrum. When the fabricated device was pumped with a 532 nm wavelength light (laser) at a temperature of 4 K, a strong emission PL spectrum was observed at specific wavelengths (approximately 738 nm to 1.1 nm). This is caused by localized excitons originating from defect states resulting from bandgap deformation of the strained WSe2 monolayer, and the thin PL linewidth of ~1.1 nm indicates localized single-photon emission. In other words, it can be confirmed that this exhibits single-photon emission characteristics formed by the interaction between the WSe2 monolayer and chiral gold nanoparticles. Furthermore, as shown in the inset, brightness was measured while increasing the light (laser) pump power; as the pump power increased, a saturation phenomenon was observed, with a saturation pump power of 0.28 μW and a PL intensity of 1.68 x 10⁻⁶ at saturation. 3 It was measured in counts / s. In other words, it can be confirmed that the emission intensity increase curve according to optical pumping power exhibits characteristic saturation properties, indicating that photoexcitation leads to single-photon emission. Additionally, to verify the single-photon characteristics, a Hanbury Brown-Twiss (HBT) interferometer was used to g 2 (0) The value was measured, and as a result, g measured in a low-temperature environment of 4K 2 (0) The value was found to be 0.5 or less, approximately 0.3 or less, specifically 0.286±0.063, which indicates the characteristics of non-classical single-photon emission, thus confirming that single-photon generation occurred. If multiple-photon emission occurs, g 2(0) Although the value should be greater than or equal to 1, in this experiment, this value was reduced to 0.3 or less, confirming the single photon emission characteristics. Through these results, the chiral gold nanoparticles combined with a tungsten diselenide (WSe2) monolayer of the present invention can be utilized as a quantum light source capable of single photon emission.

[0163]

[0164]

[0165] Experimental Example 3. Verification of Circular Polarization Characteristics

[0166] FIGS. 7 to 14 are the results of analyzing the circular polarization characteristics of chiral gold nanoparticles combined with a tungsten diselenide (WSe2) monolayer according to one embodiment of the present invention.

[0167] Single photons generated from a tungsten diselenide (WSe2) monolayer interact with chiral gold nanoparticles (cNPs) to exhibit circular polarization characteristics. To experimentally verify whether they possess circular polarization characteristics, the characteristics of two samples exhibiting left circular polarization (LCP) and right circular polarization (RCP), respectively, were compared.

[0168] Figures 7 and 11 are σ + (Right-sided circular polarization, RCP) and σ - This shows the PL spectrum measured by separating the (left circular polarization, LCP) component. Strong polarized photoluminescence was observed at specific wavelengths, which may indicate that the spin angular momentum of photons is controlled due to the coupling of the WSe2 monolayer and chiral gold nanoparticles. RCP(σ + ) and LCP(σ - When comparing the intensity differences of the polarized PL spectra, it was confirmed that LCP or RCP was dominant depending on the polarization direction, respectively. In the insets of Figures 7 and 11, g of the LCP sample and the RCP sample 2(0) The values ​​were found to be approximately 0.213 ± 0.086 and 0.286 ± 0.063, respectively, and g 2 (0)<0.5, confirming single-photon emission characteristics with high single-photon purity.

[0169] In Figures 8, 9, and 10, Stokes parameters S1, S2, and S3 were measured to specifically analyze the circular polarization characteristics (degree of circular polarization). In the device in the LCP state, a polarization direction of -58° was observed, and the values ​​of Stokes parameters S1, S2, and S3 were measured as -0.228, -0.573, and -0.793, respectively, showing strong LCP characteristics. Through Figure 10, which visualizes this, the polarization ellipse in the left-polarized state can be confirmed.

[0170] In FIGS. 12, 13, and 14, conversely, a polarization direction of 49° appeared as a device in the RCP state, and the Stokes parameters S1, S2, and S3 were measured to be -0.133, 0.846, and 0.493, respectively, showing strong RCP characteristics. Through FIG. 14, which visualizes this, the polarization ellipse in the right-sided polarization state can be confirmed. These results allow for quantitative and visual confirmation that left-sided and right-sided circular polarizations occur predominantly in the two different samples, respectively, and may imply that the circular polarization direction of photons can be changed or controlled depending on the chirality (handedness) of the chiral gold nanoparticles.

[0171]

[0172] Comparative Example 1. A chiral gold nanoparticle structure bonded with a tungsten diselenide (WSe2) monolayer

[0173] Examples 1-3. A structure comprising gold nanoparticles of an achiral structure (cube shape) and a WSe2 layer was prepared using the same method as in Example 1, except that the bonding step (S03) of the tungsten diselenide (WSe2) monolayer was not performed.

[0174]

[0175] FIGS. 15 to 19 are the results of measuring the circular polarization characteristics of a gold nanoparticle structure with an achiral structure bonded to a tungsten diselenide (WSe2) monolayer according to Comparative Example 1 of the present invention.

[0176] Referring to FIGS. 15 to 19, to determine whether gold nanoparticles having a chiral structure are involved in the circular polarization of photons, the circular polarization characteristics of a single photon generated in a structure using cube-shaped gold nanoparticles without a chiral structure were analyzed. For the device fabricated with achiral cube-shaped gold nanoparticles, the Stokes parameters S1, S2, and S3 values ​​were 0.152, 0.842, and -0.012, respectively. In particular, the value of S3 was very close to 0, confirming that photons in a linearly polarized state are emitted. When compared to the device fabricated in Example 1, the Degree of Circular Polarization (DOCP) value of photons was measured as 0.156 in Comparative Example 1, which is a very low value compared to the value of 0.389 measured in Example 1. When comparing the probability distributions by classifying the polarization type distribution into left-handed circular polarization (LCP), linear polarization (LP), and right-handed circular polarization (RCP), the device fabricated in Example 1 showed that circular polarization was dominant with LCP and RCP accounting for 35% and 25%, respectively, whereas in Comparative Example 1, 90% was linear polarization (LP). These results all indicate that Example 1 effectively generates single-photon circular polarization, whereas in Comparative Example 1, due to the anachiral structure, it does not have a specific directionality, and the generation of circularly polarized photons is limited and mainly emitted in a linearly polarized state.

[0177]

[0178] FIGS. 20 to 24 are the results of a theoretical analysis of the mechanism by which chiral gold nanoparticles (cNP) according to an embodiment of the present invention emit a circularly polarized single photon, wherein (FIS. 20) a current (J) generated inside the chiral gold nanoparticles r ,J dSchematic diagram illustrating the process of ) and dipole formation, (Fig. 21) magnetic field (H induced in chiral gold nanoparticles) ⊥ As a result of simulating the distribution, (Fig. 22) shows the change in Stokes parameters (S1, S2, S3) according to the dipole direction () and (Fig. 23) shows the elliptical polarization state at = 0° and (Fig. 24) = 90°.

[0179] Figures 20 to 24 show the results of full-wave optical simulations performed to elucidate the mechanism of circularly polarized single-photon emission from chiral gold nanoparticles (cNPs). Changes in polarization characteristics were analyzed by combining 180 nm chiral gold nanoparticles (including a 10 nm thick silica coating) with an electric dipole light source of 740 nm wavelength. In this case, it was assumed that the electric dipole light source originates from local strain sites in the WSe2 monolayer.

[0180] Figure 20 shows a schematic structural diagram of chiral gold nanoparticles, simulating the case where dipoles are positioned at specific vertex locations. Here, the current J immediately induced due to the plasmonic resonance effect d (red curved arrows) and delayed induced current J r (blue curved arrow) occurs. As can be seen in Fig. 21, the calculated magnetic field distribution is formed perpendicular to the surface of the nanoparticle, and a strong circular current is induced, particularly around the nanogap. The area indicated by the white dashed line is J rThis represents the magnetic field formed by the current. In contrast, such a magnetic field was not observed in the magnetic field distribution of achiral gold nanocubes, and only the overall oscillation of plasmon modes was present. This suggests that the nanogap structure of chiral gold nanoparticles increases the capacitive and inductive responses, and that a retarded current flow is generated despite the nanoparticle size being relatively small compared to the wavelength of light. This retarded current is a key factor enabling the induction of circular polarization even in subwavelength-sized nanostructures.

[0181] To more quantitatively analyze the changes in polarization characteristics in nanoparticles, Stokes parameters S1, S2, and S3 were calculated as the azimuthal angle of the electric dipole changed. For the experiment on Stokes parameters, an objective lens with a numerical aperture (NA) of 0.85 was applied for the calculation, and for the analysis of circular polarization, the polarization resolution intensity was analyzed based on the QWP and LP using the Jones matrix. As a result, as shown in Fig. 22, it was confirmed that all Stokes parameters were smoothly deformed when the value changed from 0° to 180°. In particular, the S3 value, which represents the degree of circular polarization, changed to a negative value (LCP dominant) at =0° and a positive value (RCP dominant) at =90°, and around =45°, the S3 value was close to 0, confirming that linear polarization (LP) was dominant. Figures 23 and 24 show the polarization ellipses when LCP and RCP are dominant, respectively, and show results consistent with the circular polarization characteristics observed in the experiment. Meanwhile, in the case of achiral nanocubes, the polarization characteristics did not change significantly with changes in value, and linear polarization in the 45° direction was observed only at =45°, while the overall circular polarization component appeared very low. This explains that this is directly related to the fact that chiral gold nanoparticles (cNPs) have a much higher DOCP (degree of circular polarization) distribution compared to achiral nanocubes. In conclusion, unlike achiral gold nanoparticles (e.g., nanocubes), chiral gold nanoparticles are structures that inherently possess SAM-encoded single photon emission.

[0182]

[0183]

[0184] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Metal nanoparticles having a chiral structure; and A two-dimensional transition metal dichalcogenide layer covering the above metal nanoparticles; comprising A single photon generator characterized by emitting a circularly polarized single photon without a separate external magnetic field under conditions where an external light source is applied.

2. In Paragraph 1, A single-photon generator in which the above two-dimensional transition metal dichalcogenide layer is a single layer.

3. In Paragraph 1, The above two-dimensional transition metal dichalcogenide is a single photon generator selected from at least one of molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2), tungsten diselenide (WSe2) and combinations thereof.

4. In Paragraph 1, A single photon generator in which the metal nanoparticles having the above chiral structure are coated with silica nanoparticles.

5. In Paragraph 1, A single photon generator having a structure of a metal nanoparticle having the above chiral structure, having a chirality three-dimensional nanostructure including a plurality of vertices and nanogaps on its interior or surface.

6. In Paragraph 1, Inside the metal nanoparticles having the above chiral structure, an instantaneous induced current (J) is generated through the plasmon resonance effect. d ) and retarded induced current (J r Forming ), The above delayed induction current (J r ) is a strong circular current and magnetic field (H) in the nanogap region ⊥ A single photon generator characterized by generating a circularly polarized single photon by inducing ).

7. In Paragraph 1, A single photon generator characterized in that the photon emitted from the above single photon generator exhibits a larger absolute value of the Stokes parameter S3 compared to the case where metal nanoparticles of an anachiral structure under the same conditions are applied.

8. In Paragraph 1, A single photon generator characterized in that the absolute value of the Stokes parameter S3 of the photon emitted from the single photon generator is 0.3 or greater and 1 or less.

9. In Paragraph 1, The photon emitted from the above single-photon generator is g measured at a temperature of 4K using an HBT (Hanbury Brown-Twiss) interferometer 2 (0) A single photon generator characterized by a value of less than 0.

5.

10. In Paragraph 1, A single photon generator characterized in that the polarization state of a photon emitted from the single photon generator has polarization characteristics that change according to the change in the azimuthal angle of an electric dipole light source.

11. In Paragraph 1, A single photon generator characterized in that the photon emitted from the above single photon generator has its spin angular momentum encoded, enabling quantum information transmission.

12. A single photon generator comprising any one selected from claims 1 to 11; and A conductive substrate comprising a plurality of the above single photon generators arranged in a periodic or non-periodic pattern; The above single photon generator emits a circularly polarized single photon without a separate external magnetic field under conditions where an external light source is applied, and A multi-array single-photon generating device characterized in that the plurality of single-photon generators each individually function as a single photon source.

13. Step of preparing metal nanoparticles having a chiral structure (S01); A step of coating silica on the surface of the metal nanoparticles having the above chiral structure (S02); and The method comprises the step (S03) of bonding a two-dimensional transition metal dichalcogenide layer to the surface of the silica-coated metal nanoparticles having a chiral structure, and A method for manufacturing a single photon generator characterized by emitting a circularly polarized single photon without a separate external magnetic field under conditions where an external light source is applied.

14. In Paragraph 13, After the above S02 step and before the above S03 step, A method for manufacturing a single photon generator, further comprising the step (S04) of arranging the above-mentioned silica-coated metal nanoparticles having a chiral structure on a conductive substrate in a periodic or non-periodic pattern.

15. In Paragraph 13, A method for manufacturing a single photon generator in which the above two-dimensional transition metal dichalcogenide layer is a single layer.

16. In Paragraph 13, A method for manufacturing a single photon generator, wherein the above-mentioned two-dimensional transition metal dichalcogenide is at least one selected from molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2), tungsten diselenide (WSe2), and combinations thereof.

17. In Paragraph 13, A method for manufacturing a single photon generator, wherein the structure of the metal nanoparticle having the chiral structure described above has a chirality three-dimensional nanostructure including a plurality of vertices and nanogaps on its interior or surface.

18. In Paragraph 13, A method for manufacturing a single photon generator, characterized in that the photon emitted from the single photon generator has a larger absolute value of the Stokes parameter S3 compared to the case where metal nanoparticles of an achiral structure under the same conditions are applied.

19. In Paragraph 13, A method for manufacturing a single photon generator, characterized in that the absolute value of the Stokes parameter S3 of the photon emitted from the single photon generator is 0.3 or greater and 1 or less.

20. In Paragraph 13, The photon emitted from the above single-photon generator is g measured at a temperature of 4K using an HBT (Hanbury Brown-Twiss) interferometer 2 (0) A method for manufacturing a single photon generator characterized by a value of less than 0.5.

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