Optical fiber light source

Abstract

To provide an optical fiber light source having high spectral wavelength flexibility and enabling incoherent continuous-wave output in a single transverse mode.SOLUTION: An optical fiber light source has: an optical fiber having a first end, a second end, and a tapered part positioned between the first and second ends, which is a single mode fiber; a wavelength conversion part; a light source for exciting the wavelength conversion part; and a support part. The first end outputs radiant light emitted from the excited wavelength conversion part. The tapered part includes: a constricted part; a first tapered region in which a diameter gradually decreases from the second end side toward the constricted part; and a second tapered region in which a diameter gradually increases from the constricted part toward the first end side. The constricted part has a diameter smaller than those of the first and second ends, and has a size of the wavelength or less of the radiant light. The wavelength conversion part is composed of liquid or gas and is disposed so as to surround at least an outer periphery of the constricted part of the tapered part. The light source simultaneously excites the outer peripheral portion surrounding the wavelength conversion part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to an optical fiber light source. [Background technology]

[0002] Fiber-optic light sources, which use optical fibers in their output stages, have been developed in various types due to their ease of routing and portability, and are widely used in industrial and research applications. However, in light sources that output incoherent light, multimode fibers are usually used in the output stage, resulting in light diffusion and poor quality of the transverse modes. Furthermore, in methods that illuminate the optical fiber core itself, such as with rare-earth doped fibers, only light at the emission wavelength of the dopant is extracted, resulting in low flexibility in the wavelength spectrum. For this reason, there is a demand for optical fiber light sources that offer good transverse mode quality, high flexibility in the wavelength spectrum, and the ability to output incoherent light. In this context, research on nanofibers is progressing, for example, as described in Non-Patent Document 1. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] NEW GLASS Vol.31 No.118 2016 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] One aspect of the disclosure aims to provide an optical fiber light source or optical fiber structure that is single transverse mode, has a high degree of freedom in wavelength spectrum, and is capable of continuous wave (CW) incoherent output. [Means for solving the problem]

[0005] In one aspect of the disclosure, the optical fiber light source is An optical fiber having a first end that emits light, a second end located on the opposite side of the first end, and a tapered portion located between the first end and the second end, and being a single-mode fiber, A wavelength conversion portion that contacts the tapered portion, A light source that excites the wavelength conversion portion, A support portion that contacts the wavelength conversion portion, And having, The first end outputs the emitted light from the excited wavelength conversion portion, The tapered portion includes a constricted portion where the diameter is minimized, a first tapered region where the diameter decreases from the second end side toward the constricted portion, and a second tapered region where the diameter increases from the constricted portion toward the first end side, The diameter of the constricted portion is smaller than the diameters of the first end and the second end, and is less than or equal to the wavelength of the emitted light.

[0006] In one aspect of the disclosure, the optical fiber structure [[ID=​​​​​​​​​​​​​​​​​​This invention provides an optical fiber light source or optical fiber structure that operates in a single transverse mode, offers high wavelength spectral freedom, and enables CW incoherent output. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating the principle of the optical fiber light source according to the embodiment. [Figure 2] This figure shows a first example configuration of an optical fiber light source. [Figure 3] This figure shows a second example configuration of an optical fiber light source. [Figure 4] This figure shows a first example of an optical fiber structure including a wavelength conversion section and a support section. [Figure 5] This figure shows a second example of an optical fiber structure including a wavelength conversion section and a support section. [Figure 6] This figure shows a third example of an optical fiber structure including a wavelength conversion section and a support section. [Modes for carrying out the invention]

[0009] In this embodiment, an optical fiber light source is provided that satisfies three conditions: "single transverse mode," "high wavelength spectral degree of freedom," and "CW incoherent light source." "Single transverse mode" is a so-called TEM 00 This is a transverse mode, a Gaussian-type propagation mode in which the intensity distribution in the cross-section of the light beam (a section perpendicular to the optical axis) is large at the center and small at the periphery. Light from a single transverse mode has high focusing and directivity.

[0010] "High wavelength spectral degree of freedom" means a configuration that is not limited to light of a single wavelength, but can generate and output light of any desired wavelength. A "CW incoherent light source" is a light source that continuously oscillates incoherent light. Incoherent light is light in which the phases and amplitudes of multiple waves fluctuate independently, making interference less likely. In this respect, it differs from lasers that output coherent light with synchronized phases, but by realizing a "single transverse mode," it is possible to output incoherent light with focusing and directivity equivalent to laser light.

[0011] Incoherent light has a broad spectral distribution, similar to sunlight or LED light. Furthermore, because the phase and amplitude distributions fluctuate randomly, wave interference is minimal. While superluminescent diodes and assisted spontaneous emission (ASE) light sources exist as highly focused or directional incoherent light sources, their output wavelengths are fixed, resulting in limited freedom in the wavelength spectrum. In other words, a light source that satisfies all three criteria—single transverse mode, high wavelength spectral freedom, and continuous wave (CW) incoherent light—has not yet been realized.

[0012] In this embodiment, a fiber optic light source that satisfies the three conditions described above is realized by incorporating the light obtained by wavelength conversion into an optical fiber. While supercontinuum (SC) light sources utilize the nonlinear optical effects of optical fibers, SC light sources are pulsed light sources that output strong, coherent pulses with aligned phases. The fiber optic light source in this embodiment is an incoherent light source with linearity and focusing properties equivalent to laser light, and a high degree of freedom in its wavelength spectrum. Having these characteristics, the fiber optic light source in this embodiment is highly useful and applicable to applications such as spot illumination for microscopes and light sources for exciting fluorescent markers used in endoscopes.

[0013] Figure 1 is a diagram illustrating the principle of the optical fiber light source 10 of the embodiment. In the following embodiments, the same reference numerals are used for the same components, and redundant explanations may be omitted. The optical fiber light source 10 has an optical fiber 11 having a tapered portion 113, a wavelength conversion unit 15 in contact with the tapered portion 113, and a light source 20 that excites the wavelength conversion unit 15, and synchrotron radiation L is emitted from the excited wavelength conversion unit 15. RAD The signal is taken into the optical fiber 11 and output from the first end 111.

[0014] Optical fiber 11 is a single-mode fiber. More specifically, the target synchrotron radiation L RADThis is an optical fiber that operates in single mode for a given wavelength. A tapered portion 113 is provided between the first end 111 of the optical fiber 11 and the second end 112 located on the opposite side of the first end. Glass, plastic, single crystal, etc., can be used as the material for the optical fiber 11. Furthermore, from the viewpoint of ease of manufacturing, it is desirable that the optical fiber 11 be a standard single-mode fiber with a cladding diameter of several hundred μm and a core diameter of several μm.

[0015] The tapered portion 113 includes a constricted portion 113a where the diameter is smallest, a first tapered region 113b where the diameter decreases from the second end 112 towards the constricted portion 113a, and a second tapered region 113c where the diameter increases from the constricted portion 113a towards the first end 111. The diameter of the constricted portion 113a is smaller than the diameter of the first end 111 and the diameter of the second end 112, and synchrotron radiation L RAD Its size is less than or equal to the wavelength of the synchrotron radiation L. RAD The wavelength refers to the wavelength of the light that you want to output. For example, if you want to output near-infrared light with a wavelength in the 1 μm band, the diameter of the constricted section 113a will be set to approximately 500 nm. If you want to output white light, the diameter of the constricted section 113a will be set to approximately 230 nm.

[0016] The tapered portion 113 is obtained, for example, by heating and stretching a portion of a single-mode fiber to reduce its diameter to below the desired wavelength. In the constricted portion 113a and its vicinity, the core 101 and cladding 102 of the optical fiber 11 are integrated, and the entire optical fiber 11 functions as a core. The medium surrounding the constricted portion 113a and its vicinity functions as cladding. In this sense, the material of the optical fiber 11 is preferably one with the highest possible refractive index, and particularly preferably one with a refractive index of 1.6 or higher.

[0017] In the narrow portion 113a whose diameter is restricted to be below a wavelength, since the optical propagation mode is distributed up to the outside (i.e., the cladding) of the optical fiber 11, the light emission from the cladding portion propagates along the optical fiber 11 as part of the propagation mode. The wavelength conversion portion 15 disposed in contact with the tapered portion 113 also functions as the cladding of the narrow portion 113a, and thus has a refractive index lower than that of the optical fiber 11.

[0018] Emitted light L RAD is generated by irradiating the wavelength conversion portion 15 with the excitation light L PUMP . Since it is only necessary to irradiate the wavelength conversion portion 15 with the excitation light L PUMP , the excitation light L PUMP may be incident from the second end portion 112 of the optical fiber 11, or the wavelength conversion portion 15 may be directly irradiated from the outside of the optical fiber 11.

[0019] The wavelength conversion portion 15 is formed of an arbitrary material that generates the emitted light L PUMP having a wavelength different from that of the excitation light L PUMP by irradiation. As an example, it contains a fluorescent substance and is formed of a material having a refractive index lower than that of the optical fiber 11. By selecting the type of the fluorescent substance and the wavelength of the excitation light that excites the fluorescent substance, the wavelength of the emitted light L RAD can be designed to a desired wavelength. As the fluorescent substance, a phosphor, a rare earth ion, a quantum dot, or the like can be used. When the wavelength conversion portion 15 contains a phosphor as the fluorescent substance, the diameter of the phosphor is preferably about several μm to several tens of μm, specifically, preferably 1 μm or more and 50 μm or less because the options of the phosphors that can be used are expanded. RAD

[0020]

[0021] The fluorescence emitted from the fluorescent substance by the irradiation of the excitation light L PUMP is incoherent light including waves of various phases and amplitudes. This incoherent light is taken into the optical fiber 11 by the propagation mode of the optical fiber 11 that spreads to the outside of the narrow portion 113a, and propagates through the optical fiber 11 as the emitted light L RAD . More precisely, the emitted light L RADis mainly confined to the core 101, and a part of it penetrates into the cladding 102 and propagates through the optical fiber 11, and is emitted from the first end portion 111.

[0021] The light output from the first end portion 111 of the optical fiber 11, which is a single-mode fiber, is collimated single transverse-mode CW incoherent light. Despite being incoherent light, it propagates over a long distance with suppressed diffusion. In order to further enhance the collimation of the output light, a collimating lens 19 may be disposed at the first end portion 111 of the optical fiber 11. When the collimating lens 19 is disposed, light can be irradiated onto a minute spot. Further, by using the collimating lens 19 as an achromatic lens, the light L RAD contained in can be made into uniform parallel light for lights of various wavelengths. Also, for the light L RAD a wavelength filter that transmits only a specific wavelength component contained in may be disposed to output monochromatic light, or only a specific wavelength component may be cut to output a combination of specific wavelengths.

[0022] <First Configuration Example> FIG. 2 is a schematic diagram of the optical fiber light source 10A of the first configuration example. In the first configuration example, a method of propagating the excitation light in the optical fiber 11 is adopted. The optical fiber light source 10A includes an optical fiber 11 having a tapered portion 113, a wavelength conversion portion 15 in contact with the tapered portion 113, a light source 20A for exciting the wavelength conversion portion 15, and a support portion 17 in contact with the wavelength conversion portion 15. The light source 20A is, for example, a laser diode (LD) that injects the excitation light L PUMP into the second end portion 112 of the optical fiber 11. The optical fiber structure 110 is formed in the portion of the optical fiber light source 10A excluding the light source 20A.

[0023] The diameter D1 of the constricted portion 113a of the tapered portion 113 of the optical fiber 11 is smaller than the diameters D2 of the second end portion 112 and the first end portion 111 of the optical fiber 11 (D1 < D2), and is smaller than the wavelength of the emission light L RAD The excitation light L incident from the second end portion 112 of the optical fiber 11 PUMPIn the constricted portion 113a and its vicinity, the light is distributed to the wavelength conversion unit 15 as evanescent light. The wavelength conversion unit 15 is excited by this evanescent light and emits light with a high degree of freedom in the wavelength spectrum.

[0024] Excitation light L PUMP The light generated in the wavelength conversion unit 15 by irradiation is CW incoherent light containing waves of various phases and amplitudes. This CW incoherent light is incorporated into the propagation mode of the optical fiber 11 in and near the constricted portion 113a, and synchrotron radiation L RAD It propagates through optical fiber 11 as synchrotron radiation L. RAD This light is emitted as a single transverse mode from the first end 111 of the optical fiber 11, which is a single-mode fiber.

[0025] The configuration shown in Figure 2 realizes a single transverse mode CW incoherent light source with high wavelength spectral freedom.

[0026] <Second example configuration> Figure 3 is a schematic diagram of the optical fiber light source 10B in the second configuration example. In the second configuration example, the excitation light L PUMP The optical fiber light source 10B employs a method in which the wavelength conversion unit 15 is irradiated from the outside by a light source 20B located on the outside of the optical fiber 11, rather than being incident from the second end 112 of the optical fiber 11. The optical fiber light source 10B includes an optical fiber 11 having a tapered portion 113, a wavelength conversion unit 15 in contact with the tapered portion 113, a light source 20B for exciting the wavelength conversion unit 15, and a support portion 17 in contact with the wavelength conversion unit 15. The light source 20B is, for example, a laser diode (LD) or light-emitting diode (LED) positioned to irradiate the wavelength conversion unit 15 with light. The optical fiber structure 110 is formed from the portion of the optical fiber light source 10B excluding the light source 20B.

[0027] In the second configuration example, at least synchrotron radiation L RADIt is sufficient that the portion from the tapered portion 113 into which light is incident to the first end portion 111 is a single-mode fiber. However, from the viewpoint of the method for manufacturing the tapered portion 113, it may be a single-mode fiber as a whole, similar to the first configuration example. The diameter D1 of the constricted portion 113a of the tapered portion 113 is smaller than the diameters D2 of the second end portion 112 and the first end portion 111 of the optical fiber 11 (D1 < D2), and is smaller than the wavelength of the emitted light L RAD The wavelength conversion portion 15 that is in contact with the tapered portion 113 is directly irradiated with the excitation light L

[0028] from the light source 20B. By irradiating with the excitation light L PUMP , the wavelength conversion portion 15 emits light having a wavelength different from that of the excitation light L PUMP . The emitted light is CW incoherent light including waves of various phases and amplitudes. The wavelength of this CW incoherent light can be designed with a high degree of freedom by appropriately selecting the material used for the wavelength conversion portion 15. PUMP

[0029] In the configurations of FIGS. 2 and 3, the support portion 17 that is in contact with the wavelength conversion portion 15 is made of an epoxy resin, a silicone resin, rubber, etc., and supports the tapered portion 113 and the wavelength conversion portion 15. From the viewpoint of strength, it is preferable that the thickness of the support portion 17 is not less than the thickness of the wavelength conversion portion 15 and not more than twice the diameter D2 of the second end portion 112 and the first end portion 111 of the optical fiber 11. In the configuration of FIG. 3, it is preferable that the support portion 17 that is in contact with the wavelength conversion portion 15 transmits 70% or more, preferably 80% or more, more preferably 90% or more of the excitation light L PUMP from the light source 20B, but in the configuration of FIG. 2, there is no particular limitation, and it does not have to transmit light. Since the diameter D1 of the constricted portion 113a of the tapered portion 113 is very small, the strength is improved by being supported by the support portion 17. Further, when manufacturing the optical fiber light sources 10A and 10B, movement of the optical fiber 11 is suppressed, and the manufacturing of the optical fiber light sources 10A and 10B becomes easy.

[0030] The CW incoherent light generated in the wavelength conversion portion 15 is taken into the propagation mode of the optical fiber 11 in the constricted portion 113a and its vicinity, and the emitted light L RAD ​It is emitted from the first end 111 of the optical fiber 11. The configuration shown in Figure 3 also realizes a single transverse mode CW incoherent light source with high wavelength spectral freedom.

[0031] <Example of optical fiber structure configuration including wavelength conversion section and support section> Figures 4 to 6 show examples of the configuration of an optical fiber structure 110A including a wavelength conversion section 15 and a support section 17. In the optical fiber structure 110A of Figure 4, a solid wavelength conversion section 15A is used. The wavelength conversion section 15A is a wavelength conversion film 151 formed on the outer circumference of at least the tapered section 113 of the optical fiber 11. The wavelength conversion film 151 can be formed by an appropriate method such as coating, spraying, or dip coating. The support section 17A is formed in contact with the wavelength conversion film 151 and can be formed by an appropriate method such as dip curing or ultraviolet curing.

[0032] The wavelength conversion film 151 contains a fluorescent substance. The wavelength conversion film 151 may contain only one type of fluorescent substance, or a mixture of multiple types of fluorescent substances. This allows for free design of the emitted light spectrum. By mixing a fluorescent substance that emits fluorescence at a desired wavelength with a low refractive index substrate such as acrylic resin or epoxy resin to form the wavelength conversion film 151, the emission characteristics of the wavelength conversion film 151 can be adjusted. The substrate is exposed to excitation light L PUMP and synchrotron radiation L RAD It is transparent to light, and the excitation light L PUMP or synchrotron radiation L RAD It is preferable that 70% or more, preferably 80% or more, and more preferably 90% or more of the light is transmitted.

[0033] The wavelength conversion film 151 is preferably positioned to cover the tapered portion 113, but it is not necessary to coat the entire circumference of the tapered portion 113; the coating area is not limited as long as it is in contact with the constricted portion 113a and its vicinity. Furthermore, the thickness of the wavelength conversion film 151 is preferably several tens of micrometers to several hundred micrometers because it is easier to manufacture.

[0034] The excitation light may be incident from the second end 112 of the optical fiber 11 as shown in Figure 2, or it may be irradiated directly onto the wavelength conversion film 151 from the outside of the tapered portion 113 as shown in Figure 3. The configuration of the wavelength conversion unit in Figure 4 is advantageous in terms of portability and assembly because the wavelength conversion unit 15A is fixed to the single-mode optical fiber 11. In addition, by providing a support portion 17A that is in contact with the wavelength conversion unit 15A, the tapered portion 113 of the optical fiber 11 and the wavelength conversion unit 15A are stably held.

[0035] Figure 5 shows an optical fiber structure 110B that includes a liquid wavelength conversion section 15B and a support section 17B. The wavelength conversion section 15B is, for example, a wavelength conversion liquid 152 contained in a container 5. The wavelength conversion liquid 152 is a liquid mixture of a solvent such as distilled water or a fluorine-based inert liquid and a fluorescent substance. The support section 17B is preferably made of a material with a refractive index lower than that of the optical fiber 11, as this can suppress the influence on the propagation mode. Furthermore, it is preferable that the support section 17B be made of a material with a refractive index similar to that of the wavelength conversion liquid 152, as this can further suppress the influence on the propagation mode. For example, it is a plate-shaped member made of a low refractive index acrylic resin or epoxy resin. A width and height of 3 cm to 7 cm and a thickness of 1 mm to 10 mm are preferable from the viewpoint of miniaturization and strength, but are not limited to these. The first tapered region 113b, the constricted region 113a, and the second tapered region 113c are fixed to the support portion 17B with a fixing material 154 such as epoxy resin, which has a refractive index close to that of the wavelength conversion solution 152. The optical fiber 11 is immersed in the wavelength conversion solution 152 while fixed to the support portion 17B. Even if the entire optical fiber 11 is not immersed in the wavelength conversion solution 152, it is sufficient if at least the tapered portion 113, including the narrowed portion 113a, is immersed in the wavelength conversion solution 152. In the example in Figure 5, the extended tapered portion 113 is folded back into a U-shape and immersed in the wavelength conversion solution 152, but the tapered portion 113 may also be placed in a sealed container filled with the wavelength conversion solution 152 without being folded back. Alternatively, the tapered portion 113 may be made to meander within a sealed container filled with the wavelength conversion solution 152. By appropriately determining the arrangement pattern of the tapered portion 113 on the support portion 17B, at least the tapered portion 113 can be immersed in the wavelength conversion solution 152.

[0036] The excitation light may be incident from the second end 112 of the optical fiber 11 as shown in Figure 2, or the wavelength conversion solution 152 may be irradiated from the outside of the container 5. When the wavelength conversion solution 152 is excited from the outside of the container 5, the container 5 is made of a material that is transparent to the excitation light. The configuration of the wavelength conversion unit in Figure 5 allows for easy replacement of the wavelength conversion solution 152 and enables the output of light of a desired wavelength. If the container 5 is a sealed container, it is also easy to carry and assemble. By providing a support part 17B in contact with the wavelength conversion unit 15B, the tapered portion 113 of the optical fiber 11 can be stably held inside the wavelength conversion unit 15B, and the manufacturing of the optical fiber structure 110B becomes easier.

[0037] Figure 6 shows an optical fiber structure 110C that includes a gaseous wavelength conversion section 15C and a support section 17C. The wavelength conversion section 15C is, for example, a wavelength conversion gas 153 sealed in a sealed container 6. The wavelength conversion gas 153 contains alkali metal gases such as rubidium and cesium, molecules such as iodine, and ions such as alkaline earth metals, which act as fluorescent substances. The support section 17C is preferably made of a material with a refractive index lower than that of the optical fiber 11, as this can suppress the influence on the propagation mode. For example, it is a plate-shaped member made of low refractive index acrylic resin or epoxy resin. A width and height of 3 cm to 7 cm and a thickness of 1 mm to 10 mm are preferable from the viewpoint of miniaturization and strength, but are not limited to these. The first tapered region 113b, the constricted region 113a, and the second tapered region 113c are fixed to the support section 17C with a fixing material 154 such as acrylic resin or epoxy resin. The optical fiber 11 is fixed to the support portion 17C and then sealed in the sealed container 6. Even if the entire optical fiber 11 is not sealed in the sealed container 6, it is sufficient that at least the tapered portion 113, including the constricted portion 113a, is located inside the sealed container 6.

[0038] The sealed container 6 has holes 61 and 62 through which the optical fiber 11 passes, and is sealed with a sealing material such as a vacuum device filler while the optical fiber 11 is inserted. The holes 61 and 62 do not necessarily have to be located on both sides of the sealed container 6, but may be located on the same side.

[0039] The excitation light may be incident from the second end 112 of the optical fiber 11 as shown in Figure 2, or the wavelength conversion gas 153 may be irradiated from the outside of the sealed container 6. When the wavelength conversion gas 153 is excited from the outside of the sealed container 6, the sealed container 6 is formed of a material that transmits 70% or more, preferably 80% or more, and more preferably 90% or more of the excitation light. By providing the support portion 17C in contact with the wavelength conversion portion 15C, the tapered portion 113 of the optical fiber 11 can be stably held within the wavelength conversion portion 15C, and the manufacturing of the optical fiber structure 110C is facilitated.

[0040] <Selection of output wavelength> In the optical fiber light source 10 of this embodiment, by selecting the fluorescent material contained in the wavelength conversion unit 15 and the wavelength of the excitation light that excites the fluorescent material, light of various wavelengths can be output. Even when using a solid wavelength conversion film 151 as shown in Figure 4, it is possible to output light of different wavelengths by changing the wavelength of the excitation light. Instead of forming the wavelength conversion film 151 around the tapered portion 113 of the optical fiber 11, the tapered portion 113 of the optical fiber 11 can also be mounted on a substrate on which the wavelength conversion film 151 is formed, so that the synchrotron radiation can be taken into the optical fiber and output from the first end 111, allowing for free selection of the output wavelength.

[0041] When using a phosphor as the fluorescent material, as an example of a combination of phosphor and excitation light, for example, when generating blue-green light with a full width at half maximum (FWHM) of about 30 nm, the phosphor used is europium-doped barium silicon oxynitride (BaSi2O2N2:Eu 2+ ) may be used, and a gallium nitride LD (GaN-LD) with an emission wavelength of 405 nm may be used as the excitation light source. SrSi2O2N2:Eu 2+ When using this, a broader green light with a wider FWHM can be obtained, and CaSi2O2N2:Eu 2+ When using this method, an even broader yellow-green synchrotron radiation from the FWHM can be obtained.

[0042] When using YAG as the yellow phosphor, a GaN-LD with an emission wavelength of 450 nm can be used as the excitation light source to obtain yellow light with an FWHM of approximately 100 nm. White light can also be generated by mixing multiple phosphors. For example, using SCASN((Sr,Ca)AlSiN3) as the red phosphor and β-sialon(Si) as the green phosphor. 6-z Al z O z N 8-z ) and the blue light-emitting material JEM(LaAl(Si 6-z Al z )N 10-z O z By using this and exciting it with a GaN-LD with an emission wavelength of 405 nm, white light can be generated.

[0043] By taking the generated light into the fiber from the narrowed portion 113a of the tapered portion 113 of the optical fiber 11 and its vicinity, CW incoherent light with a high degree of freedom in wavelength spectrum in a single transverse mode can be output from the first end 111.

[0044] The optical fiber light source 10 is incoherent light, yet possesses high focusing and directivity, making it suitable for use as spot illumination for microscopes and as excitation light for fluorescent markers in endoscopes. Furthermore, its high degree of flexibility in wavelength spectrum allows for the design of emission wavelengths and linewidths with a high degree of freedom by appropriately selecting the fluorescent material and excitation light.

[0045] The optical fiber light source 10 is not limited to the above-described configuration example and can be modified, substituted, etc., without departing from the spirit of the invention. The combination of phosphor used in the wavelength conversion section and the wavelength of the excitation light is not limited to the above-described example and can be appropriately selected depending on the application. The optical fiber light source 10 of the embodiment may be arranged in a single package and used as a light source module. In that case, at least a portion of the optical fiber 11 may be wound onto a reel and housed in the package. As shown in Figure 3, when the excitation light is irradiated from the outside of the optical fiber 11, the excess portion on the second end 112 side of the optical fiber 11 may be removed.

[0046] As the wavelength conversion unit 15, a component with a wavelength conversion film 151 formed on its surface may be interchangeably arranged within the package. As the excitation light source 20, a laser diode (LD) or light-emitting diode (LED) may be used. The optical characteristics of the radiant light from the optical fiber light source 10 may be adjusted by combining the material of the wavelength conversion unit 15 with the wavelength of the excitation light output from the light source 20. [Explanation of Symbols]

[0047] 10, 10A, 10B optical fiber light source 5 containers 6. Airtight container 15, 15A~15C Wavelength conversion section 151 wavelength conversion film 152 Wavelength conversion solution 153 Wavelength conversion gas 154 Fixed materials 11 Optical Fiber 111 First end 112 Second end 113 Tapered section 113a Stenosis 113b First tapered region 113c Second taper region 17, 17A~17C Support part 20, 20A, 20B light source 110, 110A~110C Optical Fiber Structure

Claims

1. An optical fiber that is a single-mode fiber having a first end that emits light, a second end located on the opposite side of the first end, and a tapered portion located between the first end and the second end, A wavelength conversion section in contact with the tapered portion, A light source for exciting the wavelength conversion unit, A support portion in contact with the wavelength conversion portion, It has, The first end outputs synchrotron radiation from the excited wavelength conversion unit, The tapered portion includes a constricted portion where the diameter is smallest, a first tapered region where the diameter decreases from the second end towards the constricted portion, and a second tapered region where the diameter increases from the constricted portion towards the first end. The diameter of the constricted portion is smaller than the diameter of the first end and the diameter of the second end, and is less than or equal to the wavelength of the synchrotron radiation. The wavelength conversion unit is a liquid or a gas, and is arranged to surround at least the outer circumference of the narrowed portion of the tapered portion. The light source is an optical fiber light source that simultaneously excites the portion of the wavelength conversion unit that surrounds the outer periphery.

2. The optical fiber light source according to claim 1, wherein the light source emits excitation light of a desired wavelength into the optical fiber from the second end.

3. The optical fiber light source according to claim 1, wherein the light source irradiates the wavelength conversion unit with excitation light of a desired wavelength from the outside of the optical fiber.

4. The container has the wavelength conversion unit located inside, The light source irradiates the wavelength conversion unit with excitation light of a desired wavelength from outside the container. The optical fiber light source according to claim 1, wherein the container is made of a material that transmits 70% or more of the excitation light.

5. The container has the wavelength conversion unit located inside, The optical fiber light source according to any one of claims 1 to 4, wherein the container seals the wavelength conversion unit.

6. The optical fiber light source according to any one of claims 1 to 5, wherein the synchrotron radiation output from the optical fiber is incoherent light.

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