阅读说明：本技术 涡旋光纤 (Vortex optical fiber ) 是由 闫培光 朱方祥 陈浩 于 2019-09-06 设计创作，主要内容包括：本发明公开了一种涡旋光纤,所述涡旋光纤包括热膨胀纤芯层、折射纤芯层以及包层,所述热膨胀纤芯层为掺杂有热膨胀掺杂物的石英玻璃,所述折射纤芯层为掺杂有折射掺杂物的石英玻璃,所述折射纤芯层的横截面外直径大于热膨胀纤芯层的横截面直径、所述包层的横截面外直径大于所述折射纤芯层,所述折射纤芯层环绕所述热膨胀纤芯层,所述包层环绕所述折射纤芯层。本发明利用圆对称的光纤结构或旋转对称的光纤结构,并通过在纤芯层掺杂高热膨胀系数的掺杂物,利用通过高膨胀系数物质的热应力,产生热应力双折折射,实现光纤中所述涡旋光的稳定传输。(The invention discloses a vortex optical fiber which comprises a thermal expansion fiber core layer, a refraction fiber core layer and a cladding layer, wherein the thermal expansion fiber core layer is made of quartz glass doped with a thermal expansion dopant, the refraction fiber core layer is made of quartz glass doped with a refraction dopant, the outer diameter of the cross section of the refraction fiber core layer is larger than that of the thermal expansion fiber core layer, the outer diameter of the cross section of the cladding layer is larger than that of the refraction fiber core layer, the refraction fiber core layer surrounds the thermal expansion fiber core layer, and the cladding layer surrounds the refraction fiber core layer. The invention utilizes a circularly symmetric optical fiber structure or a rotationally symmetric optical fiber structure, dopes a dopant with high thermal expansion coefficient in a fiber core layer, and generates thermal stress birefringence by utilizing the thermal stress of a substance with high expansion coefficient, thereby realizing the stable transmission of the vortex rotation in the optical fiber.)

1. The vortex optical fiber is characterized by comprising a thermal expansion fiber core layer, a refraction fiber core layer and a cladding layer, wherein the thermal expansion fiber core layer is made of quartz glass doped with a thermal expansion dopant, the refraction fiber core layer is made of quartz glass doped with a refraction dopant, the outer diameter of the cross section of the refraction fiber core layer is larger than that of the thermal expansion fiber core layer, the outer diameter of the cross section of the cladding layer is larger than that of the refraction fiber core layer, the refraction fiber core layer surrounds the thermal expansion fiber core layer, and the cladding layer surrounds the refraction fiber core layer.

2. The vortex fiber of claim 1 wherein said refractive core layer is further doped with an activating dopant.

3. A vortex optical fibre according to claim 1 or 2 wherein the concentration of the thermally expanding dopant in the thermally expanding core layer is uniformly arranged and the concentration of the refractive dopant in the refractive core layer is uniformly arranged.

4. The vortex fiber of claim 3 wherein said thermally expansive core layer is further doped with a refractive dopant.

5. The vortex optical fiber of claim 1 further comprising a buffer core layer disposed between said thermal expansion core layer and said refractive core layer.

6. The vortex fiber of claim 5 wherein the buffer core layer is doped with a thermal expansion dopant and a refractive dopant.

7. The vortex fiber of claim 1 wherein said cladding is a photonic crystal structure.

8. The vortex fiber of claim 1 wherein said cladding layer comprises an outer cladding layer and a pump light conducting layer, said outer cladding layer surrounding said pump light conducting layer.

9. The vortex fiber of claim 1 wherein the thermally expansive dopant comprises phosphorus pentoxide or boron trioxide.

10. The vortex fiber of claim 1 wherein the refractive dopant comprises germanium dioxide or fluorine.

Technical Field

The invention relates to the technical field of optical fibers, in particular to a vortex optical fiber.

Background

Vortex optical fibers have been widely used in many fields due to their excellent characteristics, such as orbital angular momentum flux, optical tweezers, super resolution, etc. In optical fiber, vortex optical field is some high-order vector mode, and can be divided into orbital angular momentum field (HE)₂₁Modes, etc.) and vector fields, which in turn can be divided into radially polarized light (TM01 modes, etc.) and azimuthally polarized light (TE)₀₁A mold, etc.). The design of the conventional vortex optical fiber is mainlyThe optical fiber is based on an annular fiber core with high refractive index difference, the high refractive index difference refers to the difference between the refractive index of the annular fiber core and the refractive index of a cladding, and the optical fiber has larger numerical aperture, so that the optical fiber is more in mode number and more suitable for multi-channel optical fiber communication; however, the too large numerical aperture of the optical fiber is not favorable for designing large mode field optical fiber, the number of modes is difficult to control, the mode purity is difficult to guarantee, and the stable transmission of vortex light with high power and high beam quality is not favorable.

Disclosure of Invention

The invention mainly aims to provide a vortex optical fiber to improve the effective refractive index difference between vortex light and realize the stable transmission of vortex optical rotation in the optical fiber.

In order to achieve the above object, the present invention provides a vortex optical fiber, which includes a thermal expansion fiber core layer, a refraction fiber core layer and a cladding layer, wherein the thermal expansion fiber core layer is made of quartz glass doped with a thermal expansion dopant, the refraction fiber core layer is made of quartz glass doped with a refraction dopant, a cross-sectional outer diameter of the refraction fiber core layer is larger than a cross-sectional diameter of the thermal expansion fiber core layer, a cross-sectional outer diameter of the cladding layer is larger than that of the refraction fiber core layer, the refraction fiber core layer surrounds the thermal expansion fiber core layer, and the cladding layer surrounds the refraction fiber core layer.

Further, the refractive core layer is doped with an activating dopant.

Further, the concentration of the thermal expansion dopant in the thermal expansion core layer is uniformly set, and the concentration of the refraction dopant in the refraction core layer is uniformly set.

Further, the thermal expansion fiber core layer is doped with refraction dopants.

Further, the vortex optical fiber further comprises a buffer core layer disposed between the thermal expansion core layer and the refractive core layer.

Further, the buffer core layer is doped with a thermal expansion dopant and a refractive dopant.

Further, the cladding is of a photonic crystal structure.

Further, the cladding layer includes an outer cladding layer surrounding the pump light conducting layer and a pump light conducting layer.

Further, the thermal expansion dopant comprises phosphorus pentoxide or boron trioxide.

Further, the refractive dopant includes germanium dioxide or fluorine.

The invention has the advantages that the circularly symmetrical optical fiber structure or the rotationally symmetrical optical fiber structure is utilized, the adulterant with high thermal expansion coefficient is doped in the fiber core layer, the thermal stress birefringence is generated by utilizing the thermal stress of the substance with high thermal expansion coefficient, and the radial polarized light (TM) in the optical fiber is realized₀₁) And angularly polarized light (TE)₀₁) The effective refractive index separation of (1) and (10) is realized, and the effective refractive difference between the optical rotation of each vortex in the optical fiber and the base film is larger than 1X 10^-4The stable transmission of the vortex optical rotation in the optical fiber is realized, the lower numerical aperture can be realized, and the large mode field optical fiber is convenient to realize.

Drawings

FIG. 1 is a schematic diagram of a vortex optical fiber according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram of the birefringence distribution and vortex optical mode field distribution of the first embodiment of the present invention;

FIG. 3 is an effective index of refraction for each of the vortex light and vector mode in a first embodiment of the present invention;

FIG. 4 is a schematic diagram of a second embodiment of the present invention providing a vortex optical fiber;

FIG. 5 is a schematic diagram of a third embodiment of the present invention providing a vortex optical fiber;

FIG. 6 is a schematic diagram of a vortex optical fiber according to a fourth embodiment of the present invention;

FIG. 7 is a schematic diagram of a vortex optical fiber according to a fifth embodiment of the present invention;

the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, in a first embodiment of the present invention, a vortex optical fiber 100 is a circular symmetric structure formed by combining a plurality of concentric circles. Specifically, the vortex optical fiber 100 includes a thermal expansion fiber core layer 10, a refraction fiber core layer 20, and a cladding layer 30, where the thermal expansion fiber core layer 10 is made of silica glass doped with a thermal expansion dopant, the refraction fiber core layer 20 is made of silica glass doped with a refraction dopant, a cross-sectional outer diameter of the refraction fiber core layer 20 is greater than a cross-sectional diameter of the thermal expansion fiber core layer 10, a cross-sectional outer diameter of the cladding layer 30 is greater than the cross-sectional diameter of the refraction fiber core layer 20, the refraction fiber core layer 20 surrounds the thermal expansion fiber core layer 10, and the cladding layer 30 surrounds the refraction fiber core layer 20.

The thermal expansion fiber core layer 10 is formed by doping thermal expansion dopants in quartz glass, and the thermal expansion dopants can be materials with high thermal expansion coefficients such as phosphorus pentoxide or boron trioxide. The thermally expanding dopant in the thermally expanding core layer 10 is used to provide thermal stress to the thermally expanding core layer 10, while the refractive dopant is used to readjust the refractive index of the thermally expanding core layer 10. The concentration of the thermal expansion adulterant in the thermal expansion fiber core layer 10 is uniformly arranged so as to generate thermal stress birefringence to realize radial polarized light (TM) in the optical fiber₀₁) And angularly polarized light (TE)₀₁) The effective refractive index separation of (1) and (10) is realized, and the effective refractive difference between the optical rotation of each vortex in the optical fiber and the base film is larger than 1X 10^-4So as to enable the stable transmission of the vortex optical rotation in the optical fiber. In some embodiments, to avoid the influence of the doped thermal expansion dopant on the refractive index of the quartz glass, an adjustment dopant is added to adjust the refractive index profile, such as adding germanium dioxide or phosphorus pentoxide to readjust the refractive index profile.

The refractive fiber core layer 20 is made of quartz glass, a refractive dopant is doped in the quartz glass, the refractive dopant can be dopants with adjustable refractive indexes such as germanium dioxide, and the concentration of the refractive dopant is uniformly arranged in the refractive fiber core layer 20 to adjust the refractive index distribution of the vortex optical fiber core, so that the mode field distribution and the birefringence distribution of vortex optical rotation have a large overlapping degree, and the birefringence of the waveguide medium is fully transmitted to be the mode birefringence. The cladding 30 comprises pure silica glass or fluorine-doped silica glass.

In this embodiment, the core structure of the thermally expanding core layer 10 and the refractive core layer 20 has an effective numerical aperture of approximately 0.073. The refractive core layer 20 has an outer diameter in the range of 12-40 μm, the ratio of the outer diameters of the thermal expansion core layer 10 and the refractive core layer 20 is 0.56, and the cladding layer 30 has an outer diameter in the range of 125-450 μm.

Referring to fig. 2, it can be seen from fig. 2 that the broken-line core layer 20 according to the first embodiment of the present invention has a large birefringence, and the mode field distribution of the vortex rotation and the birefringence distribution have a large overlap, so that the birefringence of the waveguide medium is fully transferred to the mode birefringence.

Referring to fig. 3, fig. 3 shows the effective refractive index of each of the vortex light and the vector mode in the first embodiment. It can be seen from FIG. 3 that the effective refraction between the final modes is greater than 10^-4This embodiment can then be used to stabilize transport vortex rotation.

Referring to fig. 4, fig. 4 shows a vortex optical fiber 100 according to a second embodiment, which is different from the first embodiment in that only the thermal expansion dopant is doped in the thermal expansion core layer 10, and the vortex optical fiber 100 further includes a buffer core layer 40, wherein the buffer core layer 40 is disposed between the thermal expansion core layer 10 and the refractive core layer 20, that is, the refractive core layer 20 surrounds the buffer core layer 40, and the buffer core layer 40 surrounds the thermal expansion core layer 10.

In the present embodiment, the refractive core layer 20 and the buffer core layer 40 have large birefringence, and the mode field distribution of the vortex rotation of the vortex optical fiber and the birefringence distribution have a large degree of overlap, and the birefringence of the waveguide medium is sufficiently transferred to the mode birefringence. The effective refraction between the final modes is greater than 10^-4Then the vortex optical fiber is usableVortex rotation is carried out at stable transmission. Specifically, the buffer core layer 40 is doped with a thermal expansion dopant and a refractive dopant. The buffer core layer 40 is disposed between the thermal expansion core layer and the refractive core layer 20 to achieve a buffering effect, and prevents thermal stress generated by the thermal expansion core layer 10 from being attenuated too fast in a radial direction during direct contact of the refractive core layer 20. The core of the thermally expanding core layer 10, the refractive core layer 20 and the buffer core layer 40 has an effective numerical aperture of about 0.1-0.2, preferably 0.118. The buffer core layer 40 has an outer diameter in the range of 12-40 μm, and specifically, the buffer core layer 40 may be 15 μm, 18 μm, 25 μm, or 30 μm. Preferably, the ratio of the outer diameters of the thermally expanding core layer 10 and the refractive core layer 20 is in the range of 0.5 to 0.7, and preferably the ratio of the outer diameters is 0.6. Preferably, the ratio of the outer diameters of the buffer core layer 40 and refractive core layer 20 is 11/15. Preferably, the outer diameter of the cladding 30 is in the range of 125-450 μm, and specifically, the outer diameter of the cladding 30 is in the range of 130 μm, 200 μm, 300 μm, 400 μm.

Preferably, referring to fig. 5, fig. 5 shows a vortex optical fiber 100 provided in a third embodiment, which is different from the first embodiment in that the cladding 30 is provided as a photonic crystal structure 31. By providing the photonic crystal structure 31, the optical fiber can be made to have an effective numerical aperture of 0.069. Specifically, the photonic crystal structure 31 may be an air hole structure, or a fluorine-doped silica glass formed by doping fluorine in the silica glass. The refractive core layer 20 has an outer diameter in the range of 12-40 μm, the ratio of the outer diameters of the thermal expansion core layer 10 and the refractive core layer 20 is 0.672, the ratio of the center distance of the photonic crystal structure 31 to the outer diameter of the refractive core layer 20 is 0.406, the ratio of the diameter of the photonic crystal structure 31 to the center distance of the photonic crystal structure is 0.19, and the outer diameter of the cladding layer 30 is 125-450 μm.

Preferably, referring to fig. 6, fig. 6 is a vortex optical fiber 100 provided in a fourth embodiment, in this embodiment, a refractive core layer of the vortex optical fiber is further uniformly doped with an active dopant, which is used as an active vortex optical fiber, and the active dopant can increase laser generation when the active vortex optical fiber is connected to an optical fiber device. Meanwhile, the optical fiber is doped with a co-doping agent to stabilize the active doping agent, so that the active doping agent is uniformly distributed in the refractive fiber core layer, the refractive index is regulated and controlled, and the like. Specifically, the activating dopants include, but are not limited to, rare earth metals having activating properties such as ytterbium, erbium, thulium, holmium, neodymium, dysprosium, and praseodymium. Preferably, the refractive core layer 20 is doped with a co-dopant including aluminum oxide, phosphorus pentoxide, fluorine, and the like. In this embodiment, the cladding layer 30 includes an outer cladding layer 32 and a pump light conducting layer 33, and the pump light conducting layer 33 serves as a waveguide structure for pump light in the active optical fiber. In particular, the outer cladding 32 may include a low index coating. The outer cladding 32 may also comprise fluorine-doped quartz glass. The pump light conducting layer 33 may comprise pure quartz glass.

Referring to fig. 7, in a fifth embodiment, the outer cladding 32 includes a layer of air 321 and an outer sleeve 322.

In the present embodiment, the thermally expandable core layer 10 is disposed at the center of the cladding layer 30. The vortex fiber is structured and doped such that at a particular wavelength, the vortex fiber can support LP₀₁Mould and at least one LP₁₁Vector mode of mode (TM)₀₁、HE₂₁、TE₀₁) And at least one LP₁₁The difference between the vector mode of the mode and the effective refractive index of its adjacent mode is at least 1 × 10^-4I.e. at least one vortex of light can be stably transmitted.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.