CN112433293A - Double-core photonic crystal fiber polarization beam splitter - Google Patents
Double-core photonic crystal fiber polarization beam splitter Download PDFInfo
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- CN112433293A CN112433293A CN202011332161.2A CN202011332161A CN112433293A CN 112433293 A CN112433293 A CN 112433293A CN 202011332161 A CN202011332161 A CN 202011332161A CN 112433293 A CN112433293 A CN 112433293A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02042—Multicore optical fibres
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
- G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
- G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
- G02B6/02323—Core having lower refractive index than cladding, e.g. photonic band gap guiding
- G02B6/02328—Hollow or gas filled core
Abstract
The invention discloses a polarization beam splitter of a double-core photonic crystal fiber, which comprises a fiber core region and a cladding region; wherein, the cladding region is positioned at the outer layer of the core region, and the core region and the cladding region are filled with pure quartz glass substrate materials; the fiber core area comprises a first air hole, a first fiber core and a second fiber core, the first air hole is positioned in the center of the fiber core area, and a gold film is arranged on the inner side of the first air hole; the first fiber core and the second fiber core are respectively positioned at two sides of the first air hole; the cladding region includes a plurality of second air holes arranged in a hexagonal pattern around the core region. Compared with the existing beam splitter, the double-core photonic crystal fiber polarization beam splitter has shorter length and wider communication waveband, overcomes the defects of large volume, low extinction ratio, narrow bandwidth and the like of the existing beam splitter, meets the requirements of an all-optical network with super-large capacity and easy integration in the future, and is easy to prepare and controllable in cost.
Description
Technical Field
The invention relates to the technical field of photonic crystal fiber beam splitters, in particular to a dual-core photonic crystal fiber polarization beam splitter.
Background
Polarization beam splitters have the function of splitting a beam of light having two polarization states, and are therefore widely used in optical communication systems as important optical components. Most of the early polarizing beam splitters were fabricated from conventional dual core optical fibers based on the principle of birefringence. However, the traditional optical fiber is often small in birefringence, so that the prepared beam splitter generally has the defects of large volume, low extinction ratio, narrow bandwidth and single structural design, and the integration and transmission capacity of an optical communication system are limited. In addition, the polarization beam splitter based on the conventional optical fiber has wavelength-dependent characteristics and a single working wavelength band, which greatly limits the application range.
The characteristics of the photonic crystal fiber are gradually discovered with the attention of people, the outstanding characteristics of the photonic crystal are urgent requirements of optical communication devices, and the application of the photonic crystal fiber as a polarization beam splitter is reflected in the eyes of people. Because of the flexible structure and the novel characteristic, the photonic crystal fiber polarization beam splitter has the advantages that the traditional beam splitter does not have. At present, people mainly adopt the following schemes when designing the beam splitter:
firstly, the full air hole type photonic crystal fiber, for example, in 2003, Zhang and Yang propose a polarization beam splitter based on a dual-core PCF, which can ensure that the splitting ratio is above 10dB, and the working bandwidth of 40nm is realized at 1550nm band, so that the performance superior to that of the traditional polarization beam splitter is obtained, and the advantages of the photonic crystal fiber in designing the polarization beam splitter are also highlighted. However, because of the low birefringence of such beam splitters, the length of the optical fiber is still long, and the requirement for miniaturization of the device cannot be met.
Then, other materials are filled in the air holes of the photonic crystal fiber or background materials are changed, for example, in 2013, Cao and Cui and the like design a tellurate glass-based two-core photonic crystal fiber polarization beam splitter, and the length of the two-core photonic crystal fiber polarization beam splitter is 0.441 mm. In the same year, Han et al designed a double-core photonic crystal fiber polarization beam splitter with a fluorine-doped fiber core, the length of the beam splitter was 7.362mm, and the bandwidth with the splitting ratio lower than-20 dB was 600 nm. In 2016, Liu et al developed a polarization beam splitter based on a dual-core soft glass PCF and filled with micron-sized gold wires, and the bandwidth of the beam splitter was up to 226 nm. In addition, there are liquid filling, magnetic fluid filling, and the like.
And moreover, a part of air circular holes in the photonic crystal fiber structure are changed into elliptical holes to increase birefringence, for example, in 2014, Jiang and Wang et al design a dual-core photonic crystal fiber polarization beam splitter containing elliptical air holes, wherein the beam splitting length is 0.119mm, and the bandwidth of the splitting ratio lower than-20 dB is 249 nm.
As can be seen from the above research work, in order to enable the polarization beam splitter to have smaller device size and larger operation bandwidth, the current direction is divided into the design concept of introducing other materials into the fiber core or substrate region and changing the structure of the fiber or air hole. However, from the viewpoint of manufacturing, it is difficult to realize the elliptical air holes, fill other materials in the air holes, or change the background material into soft glass or liquid crystal, and the like, and the cost is high.
Disclosure of Invention
The invention provides a double-core photonic crystal fiber polarization beam splitter, which aims to solve the technical problems of large volume, complex preparation process and higher cost of the conventional photonic crystal fiber polarization beam splitter.
In order to solve the technical problems, the invention provides the following technical scheme:
a dual-core photonic crystal fiber polarization beam splitter comprises a fiber core region and a cladding region; wherein the cladding region is located at the outer layer of the core region, and the core region and the cladding region are filled with a pure quartz glass base material; the fiber core area comprises a first air hole, a first fiber core and a second fiber core, the first air hole is positioned in the center of the fiber core area, and a gold film is arranged on the inner side of the first air hole; the first fiber core and the second fiber core are respectively positioned at two sides of the first air hole; the cladding region includes a plurality of second air holes arranged in a hexagonal pattern around the core region.
Optionally, the first core and the second core are distributed in a centrosymmetric manner with the first air hole as a symmetric center.
Optionally, the plurality of second air holes are in a multilayer arrangement structure by taking the fiber core region as a center; the second air holes of the innermost layer are arranged in a rectangular shape, and the second air holes of the rest layers are arranged in a regular hexagon shape.
Optionally, the first air hole and the second air hole are both circular holes.
Optionally, the diameter of the first air hole ranges from 0.95 μm to 1.05 μm.
Optionally, the thickness of the gold film ranges from 55nm to 60 nm.
Optionally, the diameter of the second air hole ranges from 1.45 μm to 1.55 μm.
Optionally, the pitch of the adjacent second air holes ranges from 2.10 μm to 2.14 μm.
The technical scheme provided by the invention has the beneficial effects that at least:
1. the double-core photonic crystal fiber polarization beam splitter introduces the surface plasma resonance SPR effect based on gold film coating, and has shorter length and better fiber beam splitting effect than the full air hole type photonic crystal fiber. The length of the double-core photonic crystal fiber polarization beam splitter optical fiber is only 191 mu m, and the extinction ratio at the wavelength of 1310nm can reach-47 dB; the extinction ratio at the wavelength of 1310nm can reach-46 dB.
2. The double-core photonic crystal fiber polarization beam splitter has wider communication wave band, and can realize single polarization output with extinction ratio lower than-20 dB in the wavelength range of 1.3-1.61 mu m.
3. The double-core photonic crystal fiber polarization beam splitter overcomes the defects of large volume, low extinction ratio, narrow bandwidth and the like of the traditional polarization beam splitter, and meets the requirements of a future full optical network with super-large capacity and easy integration.
4. The structure of the polarization beam splitter of the double-core photonic crystal fiber is the most common regular hexagon structure, only a thin gold film layer is added in a central air hole, based on the current fiber drawing level, the most common stacking method can be used for preparing a prefabricated rod at present, and a chemical vapor deposition method is used for forming the gold film, so that the fiber can be prepared. Therefore, the optical fiber has the advantages of simple structure, easy preparation and controllable cost.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a cross-sectional view of a dual-core photonic crystal fiber polarizing beam splitter provided by an embodiment of the present invention;
FIG. 2 is a graph showing refractive index of each polarization mode of a polarization beam splitter of a dual-core photonic crystal fiber according to an embodiment of the present invention as a function of wavelength;
FIG. 3 is a graph showing the variation of the coupling length ratio with wavelength of a polarization beam splitter of a dual-core photonic crystal fiber according to an embodiment of the present invention;
FIG. 4 is a graph showing normalized energy of a polarization beam splitter of a dual-core photonic crystal fiber according to an embodiment of the present invention;
fig. 5 is a graph showing the extinction ratio of the polarization beam splitter of the two-core photonic crystal fiber according to the embodiment of the present invention as a function of wavelength.
Description of reference numerals:
1. a first air hole;
2. a second air hole;
3. a pure quartz glass substrate material;
A. a first core;
B. a second core.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, the present embodiment provides a dual-core photonic crystal fiber polarization beam splitter, which includes a core region and a cladding region; wherein, the cladding region is positioned at the outer layer of the core region, and the core region and the cladding region are filled with a pure quartz glass substrate material 3; the fiber core area comprises a first air hole 1, a first fiber core A and a second fiber core B, the first air hole 1 is positioned in the center of the fiber core area, and a gold film is arranged on the inner side of the first air hole 1; the first fiber core A and the second fiber core B are respectively positioned at the left side and the right side of the first air hole 1 in the horizontal direction and are distributed in a centrosymmetric manner by taking the first air hole 1 as a symmetric center.
The cladding region includes a plurality of second air holes 2, the plurality of second air holes 2 being arranged in a hexagonal pattern around the core region. In this embodiment, the core region is taken as the center, and the plurality of second air holes 2 are periodically arranged in a multi-layer manner; the second air holes of the innermost layer are arranged in a rectangular shape, and the second air holes of the other layers are arranged in a regular hexagon shape.
Wherein, the first air hole 1 and the second air hole 2 are both circular holes. The diameter d1 of the first air hole 1 ranges from 0.95 μm to 1.05 μm, and the thickness t of the gold film ranges from 55nm to 60 nm. The diameter d of the second air hole 2 ranges from 1.45 μm to 1.55 μm, and is of a standard size and easy to manufacture. The horizontal distance from the center of the first fiber core A to the first air hole 1 and the second air hole 2, the horizontal distance from the center of the second fiber core B to the first air hole 1 and the second air hole 2, and the hole spacing of the adjacent second air holes 2 are all
Specifically, in the present embodiment,
is in a range of 2.10 μm &2.14μm。
In a possible embodiment, the diameter d1 of the first air hole 1 is 1 μm; the thickness t of the gold film on the inner side of the first air hole 1 is 56 nm; the diameter d of second air holes periodically distributed in the cladding is 1.5 mu m; space distance between adjacent air holes
2.12 μm; the base material of the cladding and the core is pure silica.
The first air hole 1 forms two light guiding core paths of a first fiber core a and a second fiber core B that can be used to confine and transmit light. It is through these two paths that the polarization beam splitter separates the light waves of two orthogonal polarization states. When light is emitted into the optical fiber, the gold film in the first air hole 1 generates a surface plasmon mode, and according to the coupled mode theory, a mode coupling effect occurs between the surface plasmon mode and the base films of the first fiber core A and the second fiber core B, so that the mode of X polarization and the mode of Y polarization are different.
As shown in fig. 2, since the surface plasmon resonance effect occurs after the gold film is filled in the first air hole 1, the effective refractive index of each supermode changes due to the coupling of the 2-step spp mode with the fundamental mode. The X polarization odd-antisymmetric film and the Y polarization odd-antisymmetric film have sudden change at respective resonance wavelengths, and the X polarization even-symmetric mode and the Y polarization even-symmetric mode are not influenced. It can be seen that the beam splitting effect of the polarization beam splitter of the present embodiment is greatly improved due to the SPR effect generated by adding the gold film.
As shown in fig. 3, it can be seen that the X, Y polarization coupling length and coupling length ratio characteristics of the present embodiment. X, Y the coupling length of the polarization decreases with increasing wavelength before the resonant wavelength. Then, sudden change occurs at the resonance wavelength, the coupling length after sudden change changes smoothly, and the coupling length ratio close to 2 is a crucial factor in the performance of the optical fiber polarization beam splitter. The coupling length ratio decreases with increasing wavelength before the resonance wavelength, and after the abrupt change the change stabilizes near 2, nearest 2 at 1550 nm.
As shown in fig. 4, the variation of the normalized power output of the device with the transmission length can be seen. When the length of the optical fiber is 191 μm, the energy of x-polarized light at 1550nm wavelength reaches a maximum in one core, while the light of y-polarized light reaches a maximum in the other core, and the two lights are completely separated.
As shown in fig. 5, it can be seen that the extinction ratio characteristic of the polarization beam splitter of the present embodiment varies with wavelength. It can be seen from the figure that in the bandwidth range of the wavelength range of 1.30 μm to 1.61 μm, the extinction ratios of the polarization beam splitter of the present embodiment are all less than-20 dB, the bandwidth can reach 310nm, and the polarization beam splitter can completely cover the E + S + C band. The extinction ratio at the wavelength of 1310nm can reach 47dB, and the extinction ratio at the wavelength of 1550nm can reach 46dB, which shows that the extinction ratios at the two common communication wavelengths reach extreme values, and the beam splitting effect is good.
Moreover, it is noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or terminal that comprises the element.
Finally, it should be noted that while the above describes a preferred embodiment of the invention, it will be appreciated by those skilled in the art that, once the basic inventive concepts have been learned, numerous changes and modifications may be made without departing from the principles of the invention, which shall be deemed to be within the scope of the invention. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.
Claims (8)
1. A polarization beam splitter of a double-core photonic crystal fiber is characterized by comprising a fiber core region and a cladding region; wherein the cladding region is located at the outer layer of the core region, and the core region and the cladding region are filled with a pure quartz glass base material; the fiber core area comprises a first air hole, a first fiber core and a second fiber core, the first air hole is positioned in the center of the fiber core area, and a gold film is arranged on the inner side of the first air hole; the first fiber core and the second fiber core are respectively positioned at two sides of the first air hole; the cladding region includes a plurality of second air holes arranged in a hexagonal pattern around the core region.
2. The dual-core photonic crystal fiber polarization beam splitter of claim 1, wherein the first core and the second core are distributed centrosymmetrically with the first air hole as a center of symmetry.
3. The dual-core photonic crystal fiber polarization beam splitter of claim 1, wherein the plurality of second air holes are arranged in multiple layers with the core region as the center; the second air holes of the innermost layer are arranged in a rectangular shape, and the second air holes of the rest layers are arranged in a regular hexagon shape.
4. The dual core photonic crystal fiber polarizing beam splitter of claim 1, wherein the first air hole and the second air hole are both circular holes.
5. The dual-core photonic crystal fiber polarization beam splitter of claim 4, wherein the diameter of the first air hole ranges from 0.95 μm to 1.05 μm.
6. The polarization beam splitter of the two-core photonic crystal fiber according to claim 5, wherein the thickness of the gold film ranges from 55nm to 60 nm.
7. The dual-core photonic crystal fiber polarization beam splitter of claim 6, wherein the diameter of the second air hole ranges from 1.45 μm to 1.55 μm.
8. The polarization beam splitter of the two-core photonic crystal fiber according to claim 7, wherein the hole pitch of the adjacent second air holes ranges from 2.10 μm to 2.14 μm.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113296183A (en) * | 2021-05-25 | 2021-08-24 | 北京科技大学 | Double-core photonic crystal fiber polarization beam splitter based on liquid crystal filling |
| CN114488386A (en) * | 2022-01-20 | 2022-05-13 | 南京南辉智能光学感控研究院有限公司 | Ultra-wideband dual-core photonic crystal fiber based on silver filling |
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| CN103091770A (en) * | 2012-12-28 | 2013-05-08 | 江苏大学 | Photonic crystal fiber polarization beam splitting component |
| CN103217743A (en) * | 2013-03-05 | 2013-07-24 | 西北工业大学 | Polarizing coupler based on double-core photonic crystal fibers mixed with metal wire |
| CN110068888A (en) * | 2019-06-03 | 2019-07-30 | 南京邮电大学 | A kind of broadband double-core photonic crystal fiber polarization beam apparatus |
| CN111650687A (en) * | 2020-06-12 | 2020-09-11 | 南京邮电大学 | Ultra-wideband dual-core photonic crystal fiber polarization beam splitter |
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2020
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| CN103217743A (en) * | 2013-03-05 | 2013-07-24 | 西北工业大学 | Polarizing coupler based on double-core photonic crystal fibers mixed with metal wire |
| CN110068888A (en) * | 2019-06-03 | 2019-07-30 | 南京邮电大学 | A kind of broadband double-core photonic crystal fiber polarization beam apparatus |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113296183A (en) * | 2021-05-25 | 2021-08-24 | 北京科技大学 | Double-core photonic crystal fiber polarization beam splitter based on liquid crystal filling |
| CN114488386A (en) * | 2022-01-20 | 2022-05-13 | 南京南辉智能光学感控研究院有限公司 | Ultra-wideband dual-core photonic crystal fiber based on silver filling |
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Application publication date: 20210302 |