Light-emitting device, measuring device, light-emitting method, and measuring method

Abstract

A light emitting device and the like having excellent waveguide efficiency is provided. [Solution] A light-emitting device, etc., comprising a light source, an optical fiber for receiving excitation light emitted from the light source, and a single-photon detector optically coupled to the optical fiber, wherein the optical fiber contains a rare earth element therein and has a region where at least a portion of the rare earth element exists separated into single atoms at a distance exceeding the diffraction limit.

Description

[Technical Field]

[0001] The present disclosure relates to a light emitting device, a measurement device, a light emitting method, and a measurement method. [Background technology]

[0002] Optical fibers are widely used in the fields of information technology, such as communications and computers, because they can transmit optical signals at high speeds. For example, Patent Document 1 discloses a quantum wavelength converter having an optical fiber containing a resonator and a laser light source that inputs pump light into the optical fiber, and describes a single-photon source in which a single-photon detector is connected to the optical fiber of the quantum wavelength converter. Patent Document 2 describes an optical fiber that contains a rare earth element therein and has a region in which at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-167667 [Patent Document 2] Japanese Patent Publication No. 2022-181935 Summary of the Invention [Problem to be solved by the invention]

[0004] In quantum information technology, quantum computers, quantum memories, quantum cryptography, and other applications are being considered that utilize the quantum mechanical properties of single photons.

[0005] Rare earth elements have the property of emitting light when excited by excitation light, i.e., generating photons, and optical fibers doped with rare earth elements, such as those described in Patent Document 1, are being studied. However, it is difficult to generate single photons simply by doping an optical fiber with a rare earth element.

[0006] A method for generating a single photon is described in Patent Document 2. However, when a single photon generated from a single atom is focused by an objective lens, the waveguiding efficiency is usually about 3 to 7%. Therefore, there is a demand for improving the waveguide efficiency.

[0007] The present disclosure has been made in consideration of these circumstances, and the problem that one embodiment of the present disclosure aims to solve is to provide a light emitting device, a measurement device, a light emitting method, and a measurement method that have excellent waveguiding efficiency. [Means for solving the problem]

[0008] The present disclosure includes the following aspects. <1> A light source and an optical fiber through which excitation light emitted from a light source is incident; a single-photon detector optically coupled to the optical fiber; A light emitting device, wherein the optical fiber contains a rare earth element therein, and has a region in which at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit. <2> further comprising a separating means optically coupled to the optical fiber and separating light emitted from the optical fiber into two directions; a single-photon detector optically coupled to said separating means; <1> The light emitting device according to claim 1. <3> further comprising an objective lens that focuses the excitation light emitted from the light source; The optical fiber receives the excitation light focused by the objective lens. <1> or <2> The light emitting device according to claim 1. <4> The rare earth element includes at least one of Nd, Yb, and Er; <1> ~ <3> 10. The light emitting device according to claim 9, wherein: <5> A light source and an optical fiber through which excitation light emitted from a light source is incident; a separating means for separating light emitted from the optical fiber into two directions; a single photon detector optically coupled to the separating means; a correlator connected to the single photon detector; A measurement device, wherein the optical fiber contains a rare earth element therein, and has a region where at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit. <6> A step of inputting excitation light emitted from a light source into an optical fiber; transmitting the generated light in an optical fiber to a single photon detector; Including, A light emitting method, wherein the optical fiber contains a rare earth element therein, and has a region where at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit. <7> further comprising the step of focusing the excitation light with an objective lens; The excitation light focused by the objective lens is input into an optical fiber. <6> The light-emitting method according to claim 1. <8> A step of inputting excitation light emitted from a light source into an optical fiber; splitting light generated by an optical fiber into two directions; transmitting the separated light to a single-photon detector; measuring the correlation of the photons detected by the single photon detector; A measurement method in which the optical fiber contains a rare earth element therein, and has a region in which at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit. [Effects of the Invention]

[0009] According to the present disclosure, a light emitting device, a measuring device, a light emitting method, and a measuring method that are excellent in waveguide efficiency are provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a light emitting device according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing another example of the light emitting device according to the present disclosure. [Figure 3] FIG. 3 is a schematic diagram showing an example of a measurement device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances unless otherwise specified. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0012] The drawings referred to in the following description are illustrative and schematic, and the present disclosure is not limited to these drawings. The same reference numerals indicate the same components. Also, reference numerals in the drawings may be omitted.

[0013] [Light-emitting device] The light emitting device according to the present disclosure comprises a light source, an optical fiber for receiving excitation light emitted from the light source, and a single-photon detector optically coupled to the optical fiber, wherein the optical fiber contains a rare earth element therein and has a region in which at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit. The light emitting device according to the present disclosure includes a single-photon detector optically coupled to an optical fiber, and therefore has superior waveguiding efficiency compared to conventional devices.

[0014] An example of a light emitting device according to the present disclosure will be described in detail below with reference to the drawings.

[0015] FIG. 1 is a schematic diagram showing an example of a light emitting device according to the present disclosure.

[0016] 1 includes a light source 10, an optical fiber 20, and a single-photon detector 30. The single-photon detector 30 is optically coupled to the optical fiber 20.

[0017] (light source) The light emitting device 100 includes a light source 10 . The light source 10 is not particularly limited as long as it can irradiate excitation light. The excitation light may be, for example, a laser beam having an appropriate excitation wavelength depending on the type of rare earth element contained in the optical fiber. For example, excitation wavelengths for Yb include 915 nm and 975 nm, for Er include 980 nm and 1480 nm, and for Nd include 810 nm.

[0018] (optical fiber) The light emitting device 100 includes an optical fiber 20 . The optical fiber 20 contains rare earth elements therein, and has a region in which at least a portion of the rare earth elements are separated into single atoms at a distance exceeding the diffraction limit. Hereinafter, a region where at least a part of the rare earth element is present as a single atom separated at a distance exceeding the diffraction limit is also referred to as a "specific region."

[0019] The diffraction limit of light is approximately the wavelength of the light emitted by the rare-earth element. The fact that at least a portion of the rare-earth element exists in a specific region as a single atom at a distance exceeding the diffraction limit can be confirmed by observing the generation of single photons when excitation light is irradiated onto the specific region.

[0020] The generation of single photons can be observed as follows. Excitation light is irradiated onto a specific region of an optical fiber, causing the rare earth element to emit light. The emission of the rare earth element can be confirmed by visually observing the specific region using an optical microscope (e.g., 30x to 40x magnification). Obtaining photon statistics for the emission of the rare earth element through photon correlation measurements can confirm that the photons emitted from the rare earth element atoms are in a single-photon state. Specifically, the emission of the rare earth element is split into two directions using a beam splitter, and the two separated light beams are observed using single-photon detectors, respectively, to perform simultaneous observation and measurement using two single-photon detectors. If the detection probability of photons observed simultaneously by both detectors is nearly zero, the photon emitted from the rare earth element atom is measured as being in a single-photon state. In this way, the generation of single photons can be observed.

[0021] Silica glass is preferably used as the material for the optical fiber, and the optical fiber may have a core / clad structure in which a central core is covered with a clad.

[0022] The diameter of the specific region is not particularly limited, and may be, for example, 0.3 μm to 2.0 μm. The diameter of the specific region can be measured by a method using an electron microscope or an optical microscope (for example, 30 to 40 times magnification). Alternatively, the diameter of the specific region can be measured by a method of calculating the diameter by simultaneously observing a test target or the like with a known scale.

[0023] The optical fiber may include other regions than the specific region.

[0024] Rare earth elements are useful in the field of quantum information technology. For example, rare earth elements are optically active even at room temperature, and optical excitation and optical measurement of the excitation light are easy.

[0025] Furthermore, rare earth elements form stable intrinsic energy levels in solids (in optical fibers) and have a small intrinsic energy uniformity width that is less susceptible to the external environment, making them easy to photoexcite. In contrast, quantum dots cannot form stable intrinsic energy levels in solids.

[0026] Furthermore, single photons generated from atoms of rare earth elements can be easily guided into nanometer-order waveguides (eg, in certain embodiments, specific regions) and resonators.

[0027] The type of rare earth element is not particularly limited. Examples of rare earth elements include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. For example, Yb has an isotope with a nuclear spin of 1 / 2, making it preferable from the viewpoint of application to quantum computers, quantum memories, and the like. Furthermore, Er is preferable from the viewpoint of application to optical communications, since the wavelength of the light it emits is very close to the wavelength used in optical communications. Furthermore, Nd has been established as a laser light source and is therefore economically preferable.

[0028] The rare earth elements may be used singly or in combination of two or more. From the above viewpoint, the optical fiber preferably contains at least one of Nd, Yb, and Er, and more preferably contains Nd.

[0029] Doping amount of rare earth elements into optical fiber (m -3 ) is not particularly limited as long as at least a part of the rare earth element is present separated into single atoms at a distance exceeding the diffraction limit.

[0030] (single photon detector) The light emitting device 100 includes a single photon detector 30 . There are no particular limitations on the single photon detector 30 as long as it has the function of detecting incident single photons. An example of a single photon detector is a single photon counting module manufactured by Excelitas Technologies.

[0031] The single-photon detector 30 is optically coupled to the optical fiber 20 . In the present disclosure, "optically coupled" refers to a state in which components are coupled to each other without a layer of air, gas, vacuum, or the like.

[0032] In the light emitting device 100, the optical fiber 20 and the single-photon detector 30 are optically coupled, and therefore the waveguiding efficiency is far superior to that of conventional devices.

[0033] As shown in FIG. 1, single-photon detector 30 is preferably optically coupled to the longitudinal end of optical fiber 20 .

[0034] (eyepiece, objective lens) The light emitting device 100 includes an eyepiece lens 1 and an objective lens 2 . The eyepiece lens 1 and the objective lens 2 collect the excitation light emitted from the light source 10 .

[0035] The light emitting device according to the present disclosure does not necessarily have to include an eyepiece lens and an objective lens. Furthermore, the light emitting device according to the present disclosure may include only an eyepiece lens or only an objective lens, and may include only one eyepiece lens or two or more eyepiece lenses.

[0036] When the light-emitting device according to the present disclosure includes an eyepiece and an objective lens, it is preferable that the eyepiece collects the excitation light emitted from the light source, the objective lens receives the excitation light collected by the eyepiece, and the optical fiber receives the excitation light collected by the objective lens. Furthermore, when the light emitting device according to the present disclosure includes only an objective lens, it is preferable that the objective lens collects the excitation light emitted from the light source, and that the optical fiber inputs the excitation light collected by the objective lens.

[0037] FIG. 2 is a schematic diagram showing another example of the light emitting device according to the present disclosure.

[0038] 2 includes a light source 10, an optical fiber 20, single-photon detectors 30A and 30B, and a beam splitter 40 serving as a separating means. Each of the single-photon detectors 30A and 30B is optically coupled to the beam splitter 40.

[0039] The light source 10 and the optical fiber 20 in the light emitting device 200 are similar to the light source 10 and the optical fiber 20 in the light emitting device 100, and therefore a description thereof will be omitted.

[0040] (beam splitter) The beam splitter 40 is a means for splitting the light emitted from the optical fiber 20 into two directions. The split ratio is, for example, 50:50. "Splitting light into two directions" means splitting light into two paths. An example of the beam splitter 40 is a fused single-mode optical fiber coupler manufactured by Thorlabs.

[0041] The beam splitter 40 is optically coupled to the optical fiber 20 . Additionally, beam splitter 40 is optically coupled to each of single photon detectors 30A and 30B.

[0042] In the light emitting device 200, the optical fiber 20 and the beam splitter 40 are optically coupled, and the beam splitter 40 and the single photon detectors 30A and 30B are optically coupled, so that the waveguiding efficiency is far superior to that of conventional devices.

[0043] [Lighting method] The present disclosure provides a light emission method including the steps of: inputting excitation light emitted from a light source into an optical fiber; and transmitting light generated in the optical fiber to a single-photon detector. The optical fiber contains a rare earth element, and has a region where at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit.

[0044] An example of a light emitting method according to the present disclosure is a light emitting method using a light emitting device 100 shown in FIG.

[0045] As shown in FIG. 1, excitation light (arrow A1) is emitted from light source 10. The excitation light (arrow A2) focused by eyepiece lens 1 is incident on objective lens 2, and the excitation light (arrow A3) focused by objective lens 2 is incident on optical fiber 20. Inside optical fiber 20, the excited rare earth element emits light, and a single photon is generated from the atom of the rare earth element. The light emitted from the rare earth element can be guided through a specific region of optical fiber 20 toward the longitudinal end of optical fiber 20.

[0046] Next, the light generated in the optical fiber 20 is transmitted to the single-photon detector 30. In the above light emission method, the light generated in the optical fiber 20 is sent from the optical fiber 20 to the single-photon detector 30 without being released into the air, and therefore the waveguiding efficiency is much better than conventional methods.

[0047] The light emitting method according to the present disclosure may also be a light emitting method using a light emitting device 200 shown in FIG. 2 is used, light generated in optical fiber 20 is split into two directions by beam splitter 40, and the split light is transmitted to single-photon detectors 30A and 30B. In the above light-emitting method, the light generated in optical fiber 20 is sent from optical fiber 20 to single-photon detectors 30A and 30B without being released into the air, resulting in significantly better waveguiding efficiency than conventional methods.

[0048] [Measuring equipment] FIG. 3 is a schematic diagram showing an example of a measurement device according to the present disclosure.

[0049] The measurement device 300 shown in FIG. 3 includes a light source 10, an optical fiber 20, single-photon detectors 30A and 30B, a beam splitter 40 serving as a separating means, and a correlation measuring device 50.

[0050] The light source 10 and the optical fiber 20 in the measuring device 300 are similar to the light source 10 and the optical fiber 20 in the light emitting device 100, and therefore a description thereof will be omitted. The single photon detectors 30A, 30B and the beam splitter 40 in the measurement device 300 are similar to the single photon detectors 30A, 30B and the beam splitter 40 in the light emitting device 200, and therefore a description thereof will be omitted.

[0051] (Correlation measuring instrument) The correlator 50 is connected to each of the single-photon detectors 30A and 30B. The correlator 50 can measure the probability of detecting photons observed at the same time for the light obtained from each of the single-photon detectors 30A and 30B. If the probability of detecting photons observed at the same time is nearly zero, the photon generated from the rare-earth element atom is measured as being in a single-photon state. An example of the correlator 50 is a time-correlated single-photon counting module manufactured by Becker & Hickle.

[0052] [Measurement method] The present disclosure provides a measurement method including the steps of: inputting excitation light emitted from a light source into an optical fiber; splitting the light generated in the optical fiber into two directions; transmitting the split light to a single-photon detector; and measuring the correlation of photons detected by the single-photon detector. The optical fiber contains a rare earth element therein, and has a region where at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit.

[0053] An example of a measurement method according to the present disclosure is a measurement method using a measurement device 300 shown in FIG. In the above measurement method, the light generated in the optical fiber 20 is sent from the optical fiber 20 to the single-photon detectors 30A and 30B without being released into the air, resulting in a waveguiding efficiency that is significantly better than conventional methods. [Example]

[0054] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to these examples.

[0055] When a single photon generated from a single atom is focused by an objective lens, the waveguide efficiency η1, which is determined by the numerical aperture NA of the objective lens and the refractive index n of air, is expressed by the following formula: Since the NA value of a typical objective lens is about 0.5 and the refractive index of air is about 1, the waveguide efficiency η1 was calculated to be about 6.7%.

[0056]

number

[0057] Next, when a single photon generated from a single atom inside an optical fiber is guided directly into the optical fiber using the principle of total internal reflection using the device shown in Figure 3, the waveguiding efficiency η2, which is determined by the conditions for total internal reflection of an optical fiber with a refractive index n', is expressed by the following formula: The refractive index of a typical optical fiber is approximately 1.45, and the waveguiding efficiency η2 was calculated to be approximately 31%.

[0058]

number

[0059] It was found that when the device shown in FIG. 3 was used, the waveguiding efficiency was significantly improved. [Explanation of symbols]

[0060] 10 light source 20. Optical Fiber 30, 30A, 30B Single Photon Detector 40 Beam Splitter 50 Correlation Measuring Instrument 100, 200 Light-emitting device 300 Measuring Equipment A1, A2, A3 excitation light

Claims

1. A light source and an optical fiber through which the excitation light emitted from the light source is incident; a single-photon detector optically coupled to the optical fiber; The light emitting device, wherein the optical fiber contains a rare earth element therein, and has a region in which at least a portion of the rare earth element is present as a single atom separated at a distance exceeding the diffraction limit.

2. a splitter means optically coupled to the optical fiber and splitting the light emitted from the optical fiber into two directions; 2. The light emitting device of claim 1, wherein the single-photon detector is optically coupled to the separating means.

3. further comprising an objective lens that focuses the excitation light emitted from the light source; 3. The light emitting device according to claim 1, wherein the optical fiber receives the excitation light focused by the objective lens.

4. 3. The light emitting device according to claim 1, wherein the rare earth element comprises at least one of Nd, Yb, and Er.

5. A light source and an optical fiber through which the excitation light emitted from the light source is incident; a separating means for separating light emitted from the optical fiber into two directions; a single photon detector optically coupled to said separating means; a correlator connected to the single-photon detector; A measurement device, wherein the optical fiber contains a rare earth element therein, and has a region in which at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit.

6. A step of inputting excitation light emitted from a light source into an optical fiber; transmitting the light generated in the optical fiber to a single-photon detector; Including, The light emitting method, wherein the optical fiber contains a rare earth element therein, and has a region in which at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit.

7. further comprising the step of focusing the excitation light with an objective lens; The light emitting method according to claim 6 , wherein the excitation light focused by the objective lens is made incident on an optical fiber.

8. A step of inputting excitation light emitted from a light source into an optical fiber; splitting the light generated in the optical fiber into two directions; transmitting the separated light to a single-photon detector; measuring the correlation of photons detected by the single-photon detector; The optical fiber contains a rare earth element therein, and has a region in which at least a portion of the rare earth element is separated into single atoms at a distance exceeding the diffraction limit.

Images