Single photon source device and preparation method thereof

Abstract

The invention discloses a single photon source device and a preparation method thereof, relates to the technical field of optical signal processing, and discloses the preparation method of the single photon source device, which comprises the following steps: providing a hollow-core optical fiber, a colloidal quantum dot solution and a single-mode optical fiber; guiding the colloidal quantum dot solution into a fiber core of the hollow-core optical fiber; and connecting the hollow-core optical fiber with the single-mode optical fiber to obtain the single photon source device. According to the scheme of the invention, the collection and detection efficiency of quantum dot luminescence of the single-photon source device can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical signal processing, in particular to a single photon source device and a preparation method thereof. BACKGROUND

[0002] Traditional single photon source devices usually use spatial light paths (such as high numerical aperture objective lenses) to collect and couple photons. Such a scheme has a complex optical path, a large system volume, poor stability, and huge alignment loss and mode mismatch loss when coupling the collected photons into a single-mode optical fiber for transmission, which seriously limits the final available single photon rate. Therefore, how to improve the collection and detection efficiency of quantum dot light emission of a single photon source device becomes a problem to be solved.

[0003] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0004] The main purpose of the present application is to provide a single photon source device and a preparation method thereof, which aims to solve the technical problem of how to improve the collection and detection efficiency of quantum dot light emission of a single photon source device.

[0005] To achieve the above-mentioned purpose, the present application provides a single photon source device, which comprises: a hollow optical fiber; colloidal quantum dots, which are integrated in the internal cavity of the hollow optical fiber; a single-mode optical fiber, which is connected to one end of the hollow optical fiber.

[0006] In an embodiment, the single-mode optical fiber is connected to one end of the hollow optical fiber by fusion splicing.

[0007] In an embodiment, the light emission wavelength of the colloidal quantum dots is within the transmission wavelength window of the hollow optical fiber.

[0008] In addition, to achieve the above-mentioned purpose, the present application further provides a preparation method of a single photon source device, which comprises: providing a hollow optical fiber, a colloidal quantum dot solution and a single-mode optical fiber; introducing the colloidal quantum dot solution into the core of the hollow optical fiber; connecting the hollow optical fiber and the single-mode optical fiber to obtain a single photon source device.

[0009] In an embodiment, the step of introducing the colloidal quantum dot solution into the core of the hollow optical fiber comprises: cutting the hollow optical fiber and determining the cut end of the hollow optical fiber as the first end; injecting the colloidal quantum dot solution into the core of the hollow core optical fiber from the first end.

[0010] In an embodiment, the step of introducing the colloidal quantum dot solution into the core of the hollow core optical fiber comprises: cutting the hollow core optical fiber, and determining the cut end of the hollow core optical fiber as the first end, and determining the uncut end of the hollow core optical fiber as the second end; immersing the first end into the colloidal quantum dot solution; absorbing the colloidal quantum dot solution into the core of the hollow core optical fiber from the second end.

[0011] In an embodiment, after the step of introducing the colloidal quantum dot solution into the core of the hollow core optical fiber, the method further comprises: fixing the hollow core optical fiber on a spin coater; starting the spin coater to uniformly coat the colloidal quantum dots in the colloidal quantum dot solution on the glass wall in the core.

[0012] In an embodiment, the step of connecting the hollow core optical fiber with the single mode optical fiber to obtain a single photon source device comprises: connecting the first end of the hollow core optical fiber with the single mode optical fiber; determining the unconnected end of the hollow core optical fiber as the second end in the case that the first end of the hollow core optical fiber is connected with the single mode optical fiber, and cutting the hollow core optical fiber at the second end to obtain a single photon source device.

[0013] In an embodiment, the step of connecting the first end of the hollow core optical fiber with the single mode optical fiber comprises: aligning the discharge electrode of the optical fiber fusion splicer to the single mode optical fiber side of the connection point; starting the optical fiber fusion splicer to fuse the single mode optical fiber at the first end of the hollow core optical fiber.

[0014] In an embodiment, the step of starting the optical fiber fusion splicer to fuse the single mode optical fiber at the first end of the hollow core optical fiber comprises: controlling the optical fiber fusion splicer to start; controlling the optical fiber fusion splicer to stop for a second preset time length when the optical fiber fusion splicer starts for a first preset time length; returning to the step of controlling the optical fiber fusion splicer to start until the first end of the hollow core optical fiber is fused with the single mode optical fiber.

[0015] The one or more technical solutions provided in the present application have at least the following technical effects: The inner cavity of the hollow core optical fiber constitutes an optical microcavity, which can produce Purcell effect on the integrated colloidal quantum dots, change the radiation rate of the colloidal quantum dots to enhance the light intensity and high-order correlation degree, and obtain single photons with higher purity. The hollow core optical fiber can directly collect the photons emitted by the quantum dots, avoid the low collection efficiency caused by the radiation of the photons in the traditional free space or plane substrate structure to the useless direction, and fully exert the single photon emission characteristics of the colloidal quantum dots integrated in the cavity of the hollow core optical fiber. The single mode optical fiber is connected with one end of the hollow core optical fiber, which can solve the complex structure and high loss of the traditional spatial light coupling, build a low-loss photon transmission channel, and improve the collection and detection efficiency of the single photon source device. BRIEF DESCRIPTION OF DRAWINGS

[0016] The drawings incorporated into the specification and constituting a part of the specification show embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application.

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0018] Figure 1 A structure schematic diagram of a first embodiment of a single photon source device of the present application; Figure 2 A flowchart schematic diagram of a first embodiment of a preparation method of a single photon source device of the present application; Figure 3 A flowchart schematic diagram of a second embodiment of a preparation method of a single photon source device of the present application; Figure 4 A schematic diagram of a single photon source device using device of a second embodiment of a preparation method of a single photon source device of the present application; Figure 5 A schematic diagram of a pump light excitation of a second embodiment of a preparation method of a single photon source device of the present application; Figure 6 A brief flowchart schematic diagram of a preparation method of a single photon source device provided by the second embodiment of the present application.

[0019] Explanation of reference numerals: 10, hollow core optical fiber; 20, colloidal quantum dots; 30, single mode optical fiber.

[0020] The purpose realization, functional characteristics and advantages of the present application will be further explained with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0021] It should be understood that the specific embodiments described herein are merely intended to explain the technical solutions of the present application, and are not intended to limit the present application.

[0022] In order to better understand the technical solutions of the present application, the following will be described in detail in combination with the drawings of the specification and specific embodiments.

[0023] A single photon source is a core resource of a fiber quantum network and quantum information technology, and is a physical basis for realizing quantum secure communication, quantum computing, quantum metrology and other applications. An ideal single photon source needs to meet stringent conditions such as high purity, high indistinguishability, high brightness and high collection efficiency.

[0024] At present, the physical systems for preparing a single photon source mainly include atomic systems, color centers, two-dimensional materials and colloidal quantum dots. Among them, colloidal quantum dots are considered as a single photon emitter with great application prospect because of their advantages such as being synthesized by solution method, adjustable emission wavelength and visible at room temperature.

[0025] However, the existing single photon source technology based on colloidal quantum dots has the following shortcomings: first, as a nanometer light emitter, the light emission of quantum dots is isotropic. In the traditional free space or planar substrate structure, most of the emitted photons will enter the substrate or be radiated to useless directions, which are difficult to be effectively collected, resulting in extremely low actual collection efficiency (usually less than 1%); second, the existing technology mostly uses a spatial light path (such as a high numerical aperture objective lens) for photon collection and coupling. This scheme has complex optical path, large system volume and poor stability, and there is a huge alignment loss and mode mismatch loss when coupling the collected photons into a single-mode optical fiber for transmission, which seriously limits the final available single photon rate; third, the system based on objective lens collection is not conducive to the miniaturization and all-fiber integration of the device, and it is difficult to directly and efficiently interface with the existing optical fiber network, which limits its deployment and application in practical systems such as quantum communication.

[0026] To solve the problem of collection efficiency, the existing technology tries various microcavity structures (such as microdisks, photonic crystal microcavities, etc.) for directional emission and Purcell enhancement, which is to enhance certain optical phenomena, such as the spontaneous emission rate of a light emitter, by using the Purcell effect. However, these microcavities usually have complex preparation process and high cost, and also face challenges in coupling with optical fiber systems, and have not fundamentally solved the problem of integration of high-efficiency collection and high-efficiency fiber coupling.

[0027] The present application provides a new single photon source device integrated with quantum dots and hollow core optical fiber, which combines colloidal quantum dots with hollow core optical fiber microcavities, and utilizes the characteristics that the hollow core optical fiber itself is both a microcavity and a natural photon transmission channel, to realize the integration of single photon emission, enhancement and high-efficiency optical fiber transmission.

[0028] Reference is made to Figure 1 , Figure 1 Figure 1 is a schematic diagram of a structure of a first embodiment of a single-photon source device according to the present application.

[0029] In the first embodiment, the single-photon source device comprises: a hollow-core optical fiber 10; colloidal quantum dots 20 integrated in the internal cavity of the hollow-core optical fiber 10; and a single-mode optical fiber 30 connected to one end of the hollow-core optical fiber 10.

[0030] It should be noted that the hollow-core optical fiber 10 is a hollow-core structure (i.e., an internal cavity) in the core part, and the core is surrounded by a glass tube wall to form a hollow channel. The size of the core diameter can not only accommodate the colloidal quantum dots 20, but also meet the resonance requirements of the optical microcavity. The glass tube wall ensures the structural stability of the optical fiber and provides a confinement boundary for photon transmission.

[0031] Specifically, the hollow-core optical fiber 10 as an optical microcavity can produce a Purcell effect on the spontaneous radiation of the colloidal quantum dots 20 integrated therein, change the radiation rate of the quantum dots, and thus enhance the light emission intensity and high-order correlation degree of single photons, and improve the purity of single photons. In addition, the hollow-core optical fiber 10 as a natural photon transmission channel can directly collect single photons emitted by the colloidal quantum dots 20, avoiding the problem of photon radiation to the substrate or in useless directions in the traditional free space or planar substrate structure, and greatly improving the photon collection efficiency.

[0032] In addition, it should be noted that the colloidal quantum dots 20 are nanoscale light emitters, usually with a size of several tens of nanometers, and have the characteristic of being synthesized by a solution method. They can be dissolved in a suitable solvent to form a colloidal quantum dot solution, and the emission wavelength can be adjusted by adjusting the size and composition of the colloidal quantum dots.

[0033] Specifically, the colloidal quantum dots 20 as nanoscale light emitters have the advantages of visible light emission at room temperature and stable light emission performance, and can efficiently emit single photons under the excitation of pump light. Integrating the colloidal quantum dots 20 in the internal cavity of the hollow-core optical fiber 10 can fully utilize the microcavity effect of the hollow-core optical fiber 10 to enhance the light emission performance, while avoiding the interference of external environment (such as temperature and vibration) on the light emission characteristics of the quantum dots, and ensuring the stability of single photon emission.

[0034] In addition, it should be noted that the single-mode optical fiber 30 only allows one light mode to be transmitted therein. The core is a solid quartz glass structure, and the cladding uses a material with a lower refractive index than the core. The refractive index difference realizes the constrained transmission of photons, ensuring low loss and large bandwidth of photons in the transmission process.

[0035] It should be understood that the microcavity structure of hollow optical fiber can produce the Purcell effect on the spontaneous emission of the integrated colloidal quantum dots, changing their emission rate and thus significantly enhancing their luminescence intensity and higher-order correlation, resulting in a single-photon source with higher purity. By directly collecting and transmitting single photons emitted by quantum dots using hollow optical fiber, spatial scattering is reduced, which can fundamentally eliminate alignment and coupling losses and improve the collection and detection efficiency of quantum dot emission in single-photon source devices.

[0036] Furthermore, the single-mode optical fiber 30 is connected to one end of the hollow optical fiber 10 by fusion splicing.

[0037] It should be noted that when connecting one end of single-mode fiber 30 to one end of hollow fiber 10 by fusion splicing, the fiber optic fusion splicer will be activated to generate high temperature, which will melt and fuse the end faces of the single-mode fiber 30 and the hollow fiber 10 to be connected into one, forming a continuous optical transmission channel.

[0038] It should be understood that seamless, low-loss connection between hollow fiber 10 and single-mode fiber 30 can be achieved through fusion splicing, resulting in a compact, highly stable, and environmentally resistant single-photon source device that is easy to integrate with existing optical fiber communication networks.

[0039] Furthermore, the emission wavelength of the colloidal quantum dot 20 is within the transmission wavelength window of the hollow optical fiber 10.

[0040] It should be noted that the colloidal quantum dot 20 is a single-photon emission source, and its emission wavelength can be controlled by adjusting the size and composition of the quantum dot. The precise control of its emission wavelength directly determines whether single photons can be efficiently transmitted within the hollow-core fiber 10. The transmission wavelength window of the hollow-core fiber 10 refers to the specific wavelength range within which the hollow-core fiber 10 can transmit photons with low loss. This range is determined by the structural parameters of the hollow-core fiber 10 (such as the core diameter and cladding refractive index distribution) and material properties (such as the transmittance of the glass material). When the photon wavelength is within this window, the transmission loss can be significantly reduced. If the wavelength exceeds the window range, a large amount of photon loss will occur due to absorption and scattering by the fiber material, resulting in ineffective transmission.

[0041] It should be understood that when preparing colloidal quantum dots 20, the synthesis parameters of the quantum dots need to be determined according to the transmission wavelength window of the selected hollow fiber 10, and the composition and size of the quantum dots need to be adjusted accordingly so that the emission wavelength is within the transmission wavelength window of the hollow fiber 10, in order to reduce transmission loss and improve emission and transmission efficiency.

[0042] In this embodiment, the internal cavity of the hollow fiber 10 constitutes an optical microcavity, which can induce the Purcell effect on the colloidal quantum dot 20 integrated therein, changing its radiation rate to enhance the luminescence intensity and higher-order correlation, thereby obtaining single photons with higher purity. It can also directly collect photons emitted by quantum dots, avoiding the problem of low collection efficiency caused by photons radiating in useless directions in traditional free space or planar substrate structures. At the same time, after the colloidal quantum dot 20 is integrated into the cavity of the hollow fiber 10, its single-photon emission characteristics can be fully utilized. Connecting the single-mode fiber 30 to one end of the hollow fiber 10 can solve the complex structure and high loss problem of traditional spatial optical path coupling, build a low-loss photon transmission channel, and improve the collection and detection efficiency of quantum dot emission in single-photon source devices.

[0043] Reference Figure 2 , Figure 2 This is a schematic flowchart of the first embodiment of the fabrication method of the single-photon source device of this application, which presents the first embodiment of the fabrication method of the single-photon source device of this application.

[0044] In this embodiment, the fabrication method of the single-photon source device includes steps S10 to S30: Step S10: Provide hollow-core optical fiber, colloidal quantum dot solution, and single-mode optical fiber; It should be noted that colloidal quantum dots can be dissolved in a suitable solvent to obtain a colloidal quantum dot solution. Before fabricating a single-photon source device, hollow-core optical fiber, colloidal quantum dot solution, and single-mode optical fiber that meet the specified requirements must be prepared in advance.

[0045] It should be understood that when selecting hollow fiber, it is necessary to determine the core diameter to match the requirements of colloidal quantum dot introduction and optical microcavity. Hollow fiber with a core diameter of 20-30 micrometers can be selected. When preparing colloidal quantum dot solution, it is necessary to ensure that the emission wavelength of colloidal quantum dots matches the transmission wavelength window of hollow fiber. When selecting single-mode fiber, it is necessary to ensure that it can achieve low-loss transmission after being connected with hollow fiber.

[0046] Step S20: The colloidal quantum dot solution is introduced into the core of the hollow optical fiber; It should be noted that the core of a hollow fiber is the hollow region at its center. Introducing a colloidal quantum dot solution into the core of the hollow fiber allows the colloidal quantum dots to be distributed within the optical microcavity of the hollow fiber, preparing for subsequent single-photon excitation.

[0047] It should be understood that a suitable method must be used to introduce the colloidal quantum dot solution into the core of the hollow optical fiber. During the introduction process, the operation precision must be controlled to avoid solution overflow or uneven distribution within the core. At the same time, it must be ensured that the colloidal quantum dot solution can fully fill the designated area of ​​the core. Different introduction methods can be selected according to the actual operating conditions and requirements.

[0048] In one feasible implementation, step S20 may include steps A11-A12: Step A11: Cut the hollow fiber and determine the cut end of the hollow fiber as the first end; It should be noted that a fiber optic cleaver can be used to cut the end face of the hollow fiber to obtain a flat, burr-free fiber end face. This ensures a clear image of the end face when injecting quantum dots under a microscope, and also guarantees the splicing quality between the hollow fiber and the single-mode fiber. The first end refers to the hollow fiber end face formed after the cleaving process, which is prepared for subsequent solution injection from this end.

[0049] Step A12: Inject the colloidal quantum dot solution into the core of the hollow optical fiber from the first end.

[0050] It should be noted that hollow optical fibers have air holes in the core, but the size is only tens of micrometers. Microneedles with a needle tip of 5-10 micrometers can be used as injection tools to deliver colloidal quantum dot solution from the first end of the hollow optical fiber into the core, so as to ensure that the solution can be injected accurately and without leakage.

[0051] Specifically, after determining the first end of the hollow fiber, a microneedle of appropriate specification is selected, and the tip of the microneedle is precisely aligned with the first end. The colloidal quantum dot solution inside the microneedle is slowly pushed in, so that the solution is smoothly injected into the core of the hollow fiber from the first end. During the injection process, the injection speed and injection volume need to be controlled to avoid the generation of air bubbles or uneven distribution of the solution in the core, and to ensure that the colloidal quantum dot solution can fully fill the designated area of ​​the core.

[0052] In addition to integrating colloidal quantum dots into hollow optical fibers, the hollow optical fibers can be replaced with photonic crystal fibers with hollow structures to achieve the same effect as the single-photon source device prepared in this application. Alternatively, the colloidal quantum dots can be replaced with other light-emitting micro-nano materials, such as perovskite nanocrystals or self-organized quantum dots, to achieve the same effect as the single-photon source device prepared in this application.

[0053] In this embodiment, the colloidal quantum dot solution is injected into the hollow fiber after it is cut using microneedle transfer technology, which helps to reduce costs and enable large-scale preparation, and achieves effective introduction of colloidal quantum dot solution into the core of the hollow fiber.

[0054] In another feasible implementation, step S20 may include steps A21 to A23: Step A21: Cut the hollow fiber and determine the cut end of the hollow fiber as the first end and the uncut end of the hollow fiber as the second end. It should be noted that the first end refers to the hollow fiber end face formed after cleaving, which can be cleaved using a fiber optic cleaver for subsequent solution injection. The second end refers to the uncleaved end of the hollow fiber, whose end face remains in its original state. During the adsorption operation, it serves as the port for applying negative pressure, facilitating the entry of the colloidal quantum dot solution into the fiber core.

[0055] Step A22: Immerse the first end in the colloidal quantum dot solution; It should be noted that immersion refers to the operation of completely immersing the first end of the hollow fiber into the colloidal quantum dot solution. The purpose is to allow the solution to fully contact the fiber core port at the first end, creating conditions for subsequent adsorption operations and enabling the solution to smoothly enter the fiber core.

[0056] It should be understood that after determining the first end and the second end, the first end of the hollow fiber is slowly placed into a container containing colloidal quantum dot solution, ensuring that the end face of the first end is completely immersed in the solution and that the hollow fiber is kept at an appropriate tilt angle to prevent the solution from entering from the second end, while ensuring stable contact between the first end and the solution, in preparation for subsequent solution adsorption.

[0057] Step A23: Adsorb the colloidal quantum dot solution into the core of the hollow optical fiber from the second end.

[0058] It should be noted that a vacuum adsorption device can be used to apply negative pressure at the second end, and by utilizing the pressure difference between the inside and outside of the hollow fiber, the colloidal quantum dot solution can be drawn into the fiber core from the first end, thus completing the operation of adsorbing the colloidal quantum dot solution into the fiber core of the hollow fiber.

[0059] Specifically, after immersing the colloidal quantum dot solution into the first end, the adsorption port of the vacuum adsorption device is connected to the second end of the hollow fiber. The vacuum adsorption device is then started, creating a stable negative pressure environment at the second end. Under the influence of the pressure difference, the colloidal quantum dot solution is drawn from the first end into the core of the hollow fiber. During the adsorption process, the magnitude of the negative pressure and the adsorption time need to be controlled to avoid the solution entering too quickly and generating bubbles due to excessive negative pressure, or the solution not being fully filled due to insufficient adsorption time.

[0060] In this embodiment, after the hollow fiber is cut, a colloidal quantum dot solution is introduced through vacuum adsorption, which can effectively introduce the colloidal quantum dot solution into the core of the hollow fiber and meet the needs under different operating conditions.

[0061] In another feasible implementation, after step S20, steps S201-S202 may also be included: Step S201: Fix the hollow optical fiber on the spin coater; It should be noted that a spin coater is a device that uses rotation to generate centrifugal force, causing the liquid coated on the surface of an object to be evenly distributed. Clamps or other devices can be used to stably mount hollow optical fibers at designated positions on the spin coater to secure the fibers and ensure they do not shift or wobble during rotation, thus guaranteeing the coating effect.

[0062] Specifically, after the colloidal quantum dot solution is introduced into the core of the hollow optical fiber, the hollow optical fiber is placed on the worktable of the spin coater. The appropriate clamps are used to fix the hollow optical fiber from both ends or the middle. The tightness of the clamps is adjusted to ensure that the hollow optical fiber is horizontal and secure after fixing, which is in preparation for the subsequent spin coating operation of the spin coater.

[0063] Step S202: Start the spin coater to uniformly coat the colloidal quantum dots in the colloidal quantum dot solution onto the glass wall in the fiber core.

[0064] It should be noted that after fixing the hollow fiber, turn on the power of the spin coater, set an appropriate rotation speed and rotation time, and start the spin coater. The spin coater drives the hollow fiber to rotate at high speed. Under the action of centrifugal force, the colloidal quantum dot solution spreads evenly along the glass wall of the fiber core. After the solvent gradually evaporates, the colloidal quantum dots are evenly coated on the glass wall by spin coating, ensuring that the subsequent pump light can fully and evenly excite the colloidal quantum dots to emit single photons.

[0065] In this embodiment, the quantum dots are coated evenly using a spin coater, which ensures that the pump light excites as many quantum dots as possible to emit light, thereby improving the emission efficiency.

[0066] Step S30: Connect the hollow fiber to the single-mode fiber to obtain a single-photon source device.

[0067] It should be understood that after the colloidal quantum dot solution is successfully introduced into the core of the hollow fiber, a suitable connection method (such as fusion splicing, coupling, etc.) is required to connect the hollow fiber to the single-mode fiber. During the connection process, it is necessary to ensure that the end faces of the two fibers are precisely aligned to reduce connection loss and ensure that the single photons emitted by the quantum dots in the hollow fiber can be efficiently transmitted to the single-mode fiber. After the connection is completed, a single-photon source device with single-photon generation and transmission functions is obtained.

[0068] In this embodiment, colloidal quantum dots are combined with hollow fiber microcavities. Utilizing the characteristic of hollow fiber having an air core formed by a glass tube, a colloidal quantum dot solution with a diameter of tens of nanometers is integrated into its hollow structure. Compared with traditional quantum dot luminescence methods that use spatial excitation and collection, this improves the luminescence efficiency of quantum dots, as well as the collection and detection efficiency of quantum dot luminescence. Connecting one end of a single-mode fiber to one end of the hollow fiber yields a single-photon source device. The single-mode fiber can directly transmit quantum dot luminescence, achieving integrated single-photon emission, enhancement, and efficient fiber optic transmission, reducing spatial scattering, and improving the single-photon collection efficiency.

[0069] Based on the first embodiment of this application, in the second embodiment of this application, the content that is the same as or similar to that in the first embodiment described above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 3 Step S30 may include steps S31 to S32: Step S31: Connect the first end of the hollow fiber to the single-mode fiber; It should be understood that before making the connection, the flatness of the first end of the hollow fiber must be confirmed. If there are burrs or tilting, it needs to be recut. Then, the first end of the hollow fiber is aligned with the first end of the single-mode fiber to ensure that the central axes of the two fibers coincide. This avoids increased optical loss after connection due to alignment deviation. Then, the connection is completed by the selected connection method, so that the single photons emitted by the quantum dots in the hollow fiber can be successfully transmitted into the single-mode fiber.

[0070] Specifically, the first end of the hollow fiber can be connected to the single-mode fiber through fusion splicing or connector coupling.

[0071] In one feasible implementation, step S31 may include steps S311 to S312: Step S311: Align the discharge electrode of the fiber optic fusion splicer with the biased single-mode fiber side of the connection point. It should be noted that fiber optic fusion splicers use high temperatures generated by discharge to melt and fuse the end faces of two optical fibers. The core component is the discharge electrode, and the high temperature generated by the discharge electrode is the key energy source for fiber optic splicing. The connection point refers to the area where the first end of the hollow fiber contacts or is close to the end face of the single-mode fiber. "Offset to the single-mode fiber side" means that when aligning the connection point, the central axis of the discharge electrode is offset towards the single-mode fiber side, rather than directly towards the center of the two fibers. This avoids excessive application of the high temperature of the discharge to the hollow fiber, protecting the integrity of the internal glass tube structure of the hollow fiber.

[0072] It should be understood that after aligning the first end of the hollow fiber with the single-mode fiber, the position of the discharge electrode of the fiber fusion splicer should be adjusted so that the center of the discharge area of ​​the discharge electrode is biased towards the single-mode fiber. At the same time, it should be ensured that the discharge electrode can cover the connection point area, so that the high temperature can act on the end faces of the two fibers simultaneously, which is to prepare for subsequent fusion splicing and avoid damage to the hollow fiber structure or weak fusion splicing due to improper electrode position.

[0073] Step S312: Start the fiber optic fusion splicer to fuse the single-mode fiber at the first end of the hollow fiber.

[0074] It should be understood that after aligning the discharge electrode with the single-mode fiber side of the connection point, the fiber fusion splicer is started. The equipment will control the discharge electrode to generate high temperature according to the set discharge parameters (such as discharge intensity and single discharge time). The high temperature causes the end face of the first end of the hollow fiber and the end face of the single-mode fiber to gradually melt. After the melting reaches the preset state, the discharge is stopped, and the molten area is allowed to cool and solidify naturally, so that the two fibers are firmly connected and the fusion splicing operation is completed, ensuring that the optical transmission loss meets the requirements after the connection.

[0075] In this embodiment, when splicing hollow fiber and single-mode fiber, slightly offsetting the discharge electrode to one side of the single-mode fiber can ensure the integrity of the internal structure of the hollow fiber and reduce splicing loss.

[0076] In one feasible implementation, step S312 may include: Control the start of the fiber optic fusion splicer; When the fiber optic fusion splicer starts for a first preset time, control the fiber optic fusion splicer to stop for a second preset time. Return to the step of controlling the start of the fiber optic fusion splicer until the first end of the hollow fiber is fused with the single-mode fiber.

[0077] It should be noted that the first preset duration refers to the duration of a single discharge cycle of the fiber optic fusion splicer. This duration is set based on the fiber material (such as the glass material of hollow fiber, the material of single-mode fiber), diameter, and the required degree of melting. The purpose is to ensure that the fiber end face reaches a moderately molten state at high temperatures, avoiding damage to the fiber structure due to excessive heating time in a single cycle. The second preset duration refers to the interval between discharge cycles. Stopping the discharge allows the molten area a short cooling time, preventing the collapse of the internal glass tube structure of the hollow fiber due to continuous high temperatures, and also avoiding fiber deformation caused by excessive melting.

[0078] It should be understood that after confirming that the discharge electrode position is accurate and the two optical fibers are aligned correctly, a start command can be issued through the control interface of the equipment. After receiving the command, the optical fiber fusion splicer activates the discharge system, an electric arc is generated between the discharge electrodes, and high temperature is released. The high temperature acts on the connection point between the first end of the hollow fiber and the single-mode fiber, and begins to heat and melt the fiber end face. In order to ensure the integrity of the internal structure of the hollow fiber, a small amount of discharge should be used.

[0079] Furthermore, after the fiber optic fusion splicer starts discharging, the built-in timer begins timing. When the timer reaches the first preset duration, the device automatically controls the discharge electrodes to stop discharging, entering a stop state, and simultaneously begins calculating the stop time. When the stop time reaches the second preset duration, one cycle is completed. After the first cycle, the fusion state of the two optical fibers is checked. If the requirement for sufficient fusion is not met, the fiber optic fusion splicer is restarted, repeating the operation of starting for the first preset duration and stopping for the second preset duration, and so on, until it is confirmed by equipment testing or manual observation that the first end of the hollow fiber and the single-mode fiber are completely fused, forming a connection structure that meets the requirements.

[0080] In this embodiment, multiple discharges are performed during the fusion splicing of hollow fiber and single-mode fiber, and the discharge electrode is slightly offset to one side of the single-mode fiber. This ensures the integrity of the internal structure of the hollow fiber, reduces splicing loss, and thus guarantees the transmission efficiency of single photons.

[0081] Step S32: When the first end of the hollow fiber is connected to the single-mode fiber, the unconnected end of the hollow fiber is determined as the second end, and the hollow fiber is cut at the second end to obtain a single-photon source device.

[0082] It should be noted that using a fiber optic cleaver to cut the second end face yields a flat, smooth end face, reducing the loss of subsequent pump light coupling into the hollow fiber from the second end. After cleaving, the single-photon source device with single-photon emission and transmission capabilities is fabricated.

[0083] For example, please refer to Figure 4 , Figure 4 This is a schematic diagram of the apparatus for using the single-photon source device according to the second embodiment of the fabrication method of the single-photon source device of this application. After the single-photon source device is fabricated according to the above-described fabrication method, it can be used as follows: Figure 4The single-photon source device shown uses an apparatus in which the pump source is connected to the front end of the hollow fiber (i.e., the end not connected to the single-mode fiber) in the single-photon source device, and the filter is connected to the rear end of the single-mode fiber (i.e., the end not connected to the hollow fiber) in the single-photon source device. The pump light emitted by the pump source is input into the single-photon source device. Inside the single-photon source device, the pump light excites the colloidal quantum dots integrated in the cavity inside the hollow fiber to emit single photons. The mixed optical signal containing single photons and pump light is passed into the filter. After the filter filters out the pump light, pure single-photon emitted light is obtained, which is the single-photon source.

[0084] Please refer to Figure 5 , Figure 5 This is a schematic diagram of pump light excitation in the second embodiment of the fabrication method for the single-photon source device of this application. Pump light can be input from the unfused end of a hollow-core fiber using spatial coupling. The pump light excites a quantum dot to emit a single photon. The emitted photon from the quantum dot and the pump light are then transmitted together into a single-mode fiber before being output. Fiber optic transmission reduces photon loss and improves collection and detection efficiency. Besides using spatial coupling to input the pump light, spatial coupling can also be used to couple the hollow-core fiber to the single-mode fiber.

[0085] This embodiment provides a method for fabricating a single-photon source device. By aligning the first end of a hollow fiber with a single-mode fiber and connecting the hollow fiber and the single-mode fiber by fusion splicing, a low-loss connection can be achieved, effectively protecting the integrity of the internal structure of the hollow fiber and preventing increased single-photon transmission loss due to improper connection. The second end of the hollow fiber is cut to obtain a flat end face, which creates conditions for efficient coupling input of pump light in the future.

[0086] For example, to help understand the implementation flow of the fabrication method of the single-photon source device obtained by combining this embodiment with the above embodiment one, please refer to... Figure 6 , Figure 6 A simplified flowchart of a method for fabricating a single-photon source device is provided, specifically: Prepare a section of hollow-core optical fiber. Use a fiber optic cleaver to cut one end of the hollow-core fiber, ensuring a flat end face for subsequent fusion splicing with a single-mode fiber. Inject colloidal quantum dot solution into the core of the hollow-core fiber using a microneedle. The emission wavelength of the colloidal quantum dots should match the transmission wavelength window of the hollow-core fiber. The resonant cavity formed by the glass tube inside the hollow-core fiber can enhance quantum dot emission and improve collection efficiency. Fix the hollow-core fiber injected with quantum dot solution onto a spin coater. Start the spin coater to evenly coat the quantum dot solution onto the glass wall inside the hollow-core fiber core using a spin coating method. This ensures that the pump light can excite as many quantum dots as possible to emit light, improving emission efficiency. Use a special fiber optic fusion splicer to fuse the flattened end of the hollow-core fiber with the single-mode fiber using a multi-discharge fusion splice. The method involves slightly offsetting the discharge electrode to one side of the single-mode fiber to ensure the integrity of the internal structure of the hollow fiber and reduce splicing loss. This ensures the integrity of the internal structure of the hollow fiber, reduces splicing loss, and guarantees the transmission efficiency of single photons. After splicing, the un-spun end of the hollow fiber is cut flat with a cleaver to obtain a single-photon source device, which can reduce coupling loss when spatially coupling pump light. Using spatial coupling, pump light is input from the un-spun end of the hollow fiber. The pump light excites quantum dots to emit single photons. The emitted light from the quantum dots and the pump light are transmitted together into the single-mode fiber and output. Transmission through the fiber reduces the loss of emitted photons and improves collection and detection efficiency. A filter is connected to the back end of the single-mode fiber to filter out the pump light, resulting in a pure single-photon source.

[0087] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the fabrication method of the single-photon source device of this application. Any simple modifications based on this technical concept are within the protection scope of this application.

[0088] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0089] The above description is only a part of the embodiments of this application and does not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A single photon source device, characterized in that, The single-photon source device comprises: a hollow-core optical fiber; colloidal quantum dots integrated in an inner cavity of the hollow-core optical fiber; a single-mode optical fiber connected to one end of the hollow-core optical fiber.

2. The single photon source device of claim 1, wherein, The single-mode optical fiber is connected to one end of the hollow-core optical fiber by fusion.

3. The single photon source device of claim 1, wherein, The colloidal quantum dots have a light-emitting wavelength within a transmission wavelength window of the hollow-core optical fiber.

4. A method of fabricating a single photon source device, characterized by, The single-photon source device is prepared by a method comprising: providing a hollow-core optical fiber, a colloidal quantum dot solution, and a single-mode optical fiber; introducing the colloidal quantum dot solution into a fiber core of the hollow-core optical fiber; connecting the hollow-core optical fiber to the single-mode optical fiber to obtain the single-photon source device.

5. The method of claim 4, wherein, The step of introducing the colloidal quantum dot solution into the fiber core of the hollow-core optical fiber comprises: cutting the hollow-core optical fiber and determining a cut end of the hollow-core optical fiber as a first end; injecting the colloidal quantum dot solution into the fiber core of the hollow-core optical fiber from the first end.

6. The method of claim 4, wherein, The step of introducing the colloidal quantum dot solution into the fiber core of the hollow-core optical fiber comprises: cutting the hollow-core optical fiber and determining a cut end of the hollow-core optical fiber as a first end, and determining an uncut end of the hollow-core optical fiber as a second end; immersing the first end in the colloidal quantum dot solution; absorbing the colloidal quantum dot solution into the fiber core of the hollow-core optical fiber from the second end.

7. The method of claim 4, wherein, After the step of introducing the colloidal quantum dot solution into the fiber core of the hollow-core optical fiber, the method further comprises: fixing the hollow-core optical fiber on a spin coater; starting the spin coater to uniformly coat colloidal quantum dots in the colloidal quantum dot solution on a glass wall in the fiber core.

8. The method of claim 4, wherein, The step of connecting the hollow-core optical fiber to the single-mode optical fiber to obtain the single-photon source device comprises: connecting the first end of the hollow-core optical fiber to the single-mode optical fiber; determining an unconnected end of the hollow-core optical fiber as a second end in the case that the first end of the hollow-core optical fiber is connected to the single-mode optical fiber, and cutting the hollow-core optical fiber at the second end to obtain the single-photon source device.

9. The method of claim 8, wherein, The step of connecting the first end of the hollow-core optical fiber to the single-mode optical fiber comprises: aligning a discharge electrode of a fiber fusion splicer to a single-mode optical fiber side of the connection point; starting the fiber fusion splicer to fuse the single-mode optical fiber at the first end of the hollow-core optical fiber.

10. The method of claim 9, wherein, The step of starting the fiber fusion splicer to fuse the single-mode optical fiber at the first end of the hollow-core optical fiber comprises: controlling the fiber fusion splicer to start; controlling the fiber fusion splicer to stop for a second preset time length when the fiber fusion splicer starts for a first preset time length; returning to the step of controlling the fiber fusion splicer to start until the first end of the hollow-core optical fiber is completely fused to the single-mode optical fiber.

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