阅读说明：本技术 线缺陷排列空气孔和金线引入的单模单偏振光子晶体光纤 (Single-mode single-polarization photonic crystal fiber with air holes arranged by linear defects and introduced by gold wires ) 是由 余志华 金志钊 于 2021-07-21 设计创作，主要内容包括：本发明提供了一种线缺陷排列空气孔和金线引入的单模单偏振光子晶体光纤,整个光子晶体光纤包括两根分布于Y轴的金线,用于加大Y偏振方向偏振光的限制损耗以达到偏振滤波的作用。通过在光子晶体光纤中Y轴引入线缺陷排列的空气孔,使得光纤内沿X偏振方向和Y偏振方向传播的线偏振光之间的有效折射率之差变大,其限制损耗差也加大；通过在内层于Y轴方向引入金线,加大了Y偏振方向和X偏振方向的限制损耗之差,实现了对X偏振方向和Y偏振方向线偏振光的完全分束。本发明的有益效果是：能够较为容易的激发等离子体共振,且金的化学性质稳定,易于加工；通过在外层排列六角形空气孔阵列,使得基模式光被限制在纤芯区域,有利于光的传输。(The invention provides a single-mode single-polarization photonic crystal fiber introduced by a linear defect arrangement air hole and gold wires, wherein the whole photonic crystal fiber comprises two gold wires distributed on a Y axis and is used for increasing the limiting loss of polarized light in the Y polarization direction so as to achieve the effect of polarization filtering. The difference of effective refractive indexes between linearly polarized light propagating along the X polarization direction and the Y polarization direction in the optical fiber is increased by introducing air holes with linear defect arrangement in the Y axis of the photonic crystal fiber, and the limit loss difference is also increased; by introducing gold wires into the inner layer in the Y-axis direction, the difference between the limiting losses in the Y polarization direction and the X polarization direction is increased, and the complete beam splitting of linearly polarized light in the X polarization direction and the Y polarization direction is realized. The invention has the beneficial effects that: the plasma resonance can be easily excited, and the gold has stable chemical property and is easy to process; by arranging the hexagonal air hole array on the outer layer, the light of the base mode is limited in the core area, and the transmission of the light is facilitated.)

1. A single-mode single-polarization photonic crystal fiber with air holes arranged by linear defects and introduced by gold threads is characterized in that: the photonic crystal fiber comprises a photonic crystal fiber (1) and gold threads (2), wherein air holes in linear defect arrangement are arranged in the photonic crystal fiber (1), the air holes and the gold threads (2) are arranged along the Y-axis direction of the cross section of the photonic crystal fiber (1) and are symmetrically distributed around the circle center of the cross section, and the air holes comprise outer-layer air holes (31) and inner-layer air holes (32); inner layer air hole (32), outer layer air hole (31) and gold thread (2) all axially run through photonic crystal fiber (1), and gold thread (2) are located outer layer air hole (31) and inner layer air hole (32) inboard, and inner layer air hole (32) are located gold thread (2) outside and outer layer air hole (31) inboard.

2. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the gold wires (2) are located at the 2.45 mu m position on the Y axis of the photonic crystal fiber (1), and the plurality of gold wires (2) are symmetrically distributed around the fiber core of the photonic crystal fiber (1).

3. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the aperture of the inner layer air hole (32) is larger than that of the outer layer air hole (31).

4. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the photonic crystal fiber (1) is a D-type photonic crystal fiber, and/or the diameter of the photonic crystal fiber (1) is 20 μm.

5. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the minimum distance between adjacent outer layer air holes (31) is 1.5 mu m.

6. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the outer air holes (31), the inner air holes (32) and the gold wires (2) are arranged in plane symmetry with respect to the central axis of the photonic crystal fiber (1).

7. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the number of the outer layer air holes (31) is 76, and/or the pore diameter of the outer layer air holes (31) is 1 μm.

8. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the number of the inner layer air holes (32) is 2, and/or the pore diameter of the inner layer air holes (32) is 2.5 μm.

9. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the number of the gold wires (2) is 2, and/or the diameter of the gold wires (2) is 0.4 μm.

10. The single-mode single-polarization photonic crystal fiber introduced by the linear defect arrangement air holes and the gold wires according to claim 1, wherein: the photonic crystal fiber (1) is made of a silica material.

Technical Field

The invention relates to the field of optical fiber sensing, in particular to a single-mode single-polarization photonic crystal fiber introduced by a linear defect arrangement air hole and a gold wire.

Background

Surface Plasmon Resonance (SPR) is an optical phenomenon in which electrons density oscillations are excited at a metal-dielectric interface by p-polarized light or transverse magnetic waves. Compared with prism-based SPR sensors such as traditional prism structures, the SPR sensor based on the optical fiber or Photonic Crystal Fiber (PCF) has the advantages of small volume, high integration level, low cost and the like, and has great potential in the fields of real-time, remote sensing and distributed measurement.

The photonic crystal fiber is an open-design fiber, and can flexibly control the light wave mode, the light field distribution and the light field area transmitted in the fiber by designing the internal microstructure and the material composition. The flexible design of the photonic crystal fiber provides unique optical characteristics, and the existence of the air holes provides possibility for inserting functional materials, so that the effective refractive index of the photonic crystal fiber can be adjusted. In recent years, SPR single mode single polarization filters based on PCF have been widely studied and applied. Single mode single polarization photonic crystal fibers have been used for wavelength tuning, high energy lasers, polarization imaging systems and other applications.

However, in practical applications, since the birefringence of the linearly polarized light with different polarization directions is difficult to increase, the difference between the limiting losses is limited to increase, and it is difficult to achieve complete beam splitting of the polarized light with different polarization directions. Designing a line defect arrangement air hole and gold wire introduction becomes the most effective method to increase the difference of confinement loss.

Disclosure of Invention

In order to solve the problems, the invention provides a single-mode single-polarization photonic crystal fiber with linear defect arrangement air holes and gold wires introduced, wherein the linear defect arrangement air holes are introduced into the photonic crystal fiber along the Y axis, so that the difference of effective refractive indexes between linearly polarized light propagating along the X polarization direction and the Y polarization direction in the fiber is increased, and the limit loss difference is also increased; by introducing a gold wire in the Y-axis direction of the inner layer, the difference between the limiting losses in the Y polarization direction and the X polarization direction is further increased, and the complete beam splitting and filtering of the linearly polarized light in the X polarization direction and the Y polarization direction in the working waveband are realized. The single-mode single-polarization photonic crystal fiber comprises a photonic crystal fiber and gold threads, wherein air holes in linear defect arrangement are arranged in the photonic crystal fiber, the air holes and the gold threads are arranged along the Y-axis direction of the cross section of the photonic crystal fiber and are symmetrically distributed around the circle center of the cross section, and the air holes comprise outer air holes and inner air holes;

the inner layer air hole, the outer layer air hole and the gold thread axially penetrate through the photonic crystal fiber, the gold thread is located on the inner sides of the outer layer air hole and the inner layer air hole, and the inner layer air hole is located on the outer side of the gold thread and the inner side of the outer layer air hole. The single-mode single-polarization photonic crystal fiber can realize complete separation of linearly polarized light in the X polarization direction and linearly polarized light in the Y polarization direction.

Further, the aperture of the inner layer air hole is larger than that of the outer layer air hole.

Further, the photonic crystal fiber is a D-type photonic crystal fiber, and/or the diameter of the photonic crystal fiber is 20 μm.

Further, the minimum distance between adjacent outer air holes is 1.5 μm.

Further, the outer air holes, the inner air holes and the gold wires are respectively arranged in plane symmetry with respect to the central axis of the photonic crystal fiber.

Further, the number of the outer layer air holes is 76, and/or the pore diameter of the outer layer air holes is 1 μm.

Further, the number of the inner layer air holes is 2, and/or the pore diameter of the inner layer air holes is 2.5 μm.

Further, the number of the gold wires was 2, and/or the diameter of the gold wires was 0.4 μm.

Further, the photonic crystal fiber is made of a silica material.

The technical scheme provided by the invention has the beneficial effects that: because gold has high sensitivity, plasma resonance can be easily excited, and the gold has stable chemical properties and is easy to process; by arranging the hexagonal air hole array on the outer layer, the light of the base mode is limited in the core area, and the transmission of the light is facilitated.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a structural diagram of a single-mode single-polarization photonic crystal fiber with air holes and gold wires for alignment of line defects introduced therein according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the effective refractive index of the Y-polarization mode, the effective refractive index of the X-polarization mode, the effective refractive index of the plasmon excitation mode, the effective refractive index of the first-order excitation mode, and the effective refractive index of the second-order excitation mode with respect to the wavelength in the wavelength range of 400nm to 1600nm according to the embodiment of the present invention.

FIG. 3 is a graph of the confinement loss of the Y-polarization mode and the confinement loss of the X-polarization mode versus wavelength in the wavelength range of 400nm to 1600nm according to an embodiment of the present invention.

The designations in the figures illustrate the following:

1. a photonic crystal fiber; 2. gold thread; 31. outer layer air holes; 32. inner layer air holes.

Detailed Description

For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

The embodiment of the invention provides a single-mode single-polarization photonic crystal fiber introduced by a linear defect arrangement air hole and a gold wire, which can be used for a single-mode single-polarization filter.

Referring to fig. 1, fig. 1 is a structural diagram of a single-mode single-polarization photonic crystal fiber introduced with line defect arrangement air holes and gold wires, including a photonic crystal fiber 1 and a gold wire 2 axially penetrating through the single-mode single-polarization photonic crystal fiber 1, where a cladding of the photonic crystal fiber 1 is provided with a plurality of air holes axially penetrating through the photonic crystal fiber 1, that is, the photonic crystal fiber 1 is provided with air holes arranged with line defects along the Y axis, the photonic crystal fiber 1 is provided with gold wires 2 in the Y axis direction of an inner layer, the air holes include a plurality of outer layer air holes 31 and a plurality of inner layer air holes 32, where the aperture of the outer layer air holes 31 is 1 μm, the number of the outer layer air holes 31 is 76, the aperture of the inner layer air holes 32 is 2.5 μm, and the number of the inner layer air holes 32 is 2; the diameter of the gold thread 2 is 0.4 μm, the gold thread 2 is positioned at the inner side of the inner layer air hole 32 and the outer layer air hole 31, the gold thread 2 is positioned at the 2.45 μm position on the Y axis of the photonic crystal fiber, and the two gold threads 2 are symmetrically distributed around the fiber core of the photonic crystal fiber 1.

The outer air holes 31 and the inner air holes 32 are symmetrically distributed about the Y axis of the photonic crystal fiber 1, the inner air holes 32 are positioned on the outer side of the gold thread 2, and the outer air holes 31 are positioned on the outer side of the inner air holes 32; the diameter of the photonic crystal fiber is 20 μm; the minimum distance between the outer layer air holes 31 and the inner layer air holes 32 is 1.5 μm, the minimum distance between each outer layer air hole 31 is 1.5 μm, namely the minimum distance between adjacent outer layer air holes 31 is 1.5 μm; the material of the photonic crystal fiber 1 is silica.

Adopting a wavelength modulation method, wherein the wavelength variation range is 400-1600 nm, carrying out mode analysis on the designed experimental model by using a full vector Finite Element Method (FEM) -based COMSOL Multiphysics calculation software, solving the effective refractive index of a mode field, and then according to a wave limiting loss formulaCalculating the confinement loss, where λ represents the wavelength, n_effDenotes the effective refractive index of the fiber mode, Im (n)_eff) Is the imaginary part of the effective index of refraction of the fiber mode.

FIG. 2 shows the corresponding curves of the effective refractive index of the X-polarization mode, the effective refractive index of the Y-polarization mode, the effective refractive index of the plasma excitation mode, the effective refractive index of the first-order excitation mode, and the effective refractive index of the second-order excitation mode with respect to the wavelength, respectively, as shown in FIG. 2, the effective refractive index of the Y-polarization mode intersects with the effective refractive index of the Y-polarization mode at 954nm wavelength, and the effective refractive index of the Y-polarization mode at 954nm wavelength, which means that the effective refractive index of the Y-polarization mode is equal to the effective refractive index of the Y-polarization mode, and the Y-polarization mode is coupled to the surface of the gold wire to the maximum extent, and the strong plasma excitation mode is excited, so that the confinement loss of the Y-polarization mode at 954nm wavelength is greatly enhanced to reach a peak value, and the effective refractive index of the second-order excitation mode does not intersect with the effective refractive index of the X-polarization mode, and the effective refractive index of the X-polarization mode does not intersect with each other, the X-polarization mode confinement loss here is maintained at a low level. As can be seen from fig. 2, the effective refractive index of the X-polarization mode intersects with the effective refractive index of the first-order excitation mode at a wavelength of 1238nm, and the effective refractive index of the X-polarization mode changes abruptly at this point, which means that the effective refractive index of the first-order excitation mode at a wavelength of 1238nm is equal to the effective refractive index of the X-polarization mode, and at this time, the X-polarization mode is coupled to the surface of the gold wire to the maximum extent, and the strong plasmon excitation mode is excited, so that the confinement loss of the X-polarization mode at a wavelength of 1238nm is greatly enhanced to reach a peak value, and the effective refractive index of the first-order excitation mode does not intersect with the effective refractive index of the Y-polarization mode, and the effective refractive index of the Y-polarization mode does not change abruptly, so that the Y-polarization mode is maintained at a lower level.

FIG. 3 is a corresponding curve of the limiting loss of the X polarization mode and the limiting loss of the Y polarization mode with respect to the wavelength, as can be seen from FIG. 3, the limiting loss of the Y polarization mode reaches the peak value at the 954nm wavelength, the value is 1450.19dB/cm, the limiting loss of the X polarization mode at the 954nm wavelength is 37.87dB/cm, and the difference between the limiting loss of the Y polarization mode and the limiting loss of the X polarization mode is 1412.32dB/cm, which indicates that the X polarization mode and the Y polarization mode are completely separated at the 954nm wavelength, the limiting loss difference is much larger than 20dB/cm, and the polarization effect is superior to that of any photonic crystal fiber of the same kind. As can be seen from FIG. 3, at a wavelength of 1238nm, the X-polarization mode confinement loss reaches a peak value of 714dB/cm, the Y-polarization mode confinement loss at a wavelength of 1238nm is 57.95dB/cm, the difference between the X-polarization mode confinement loss and the Y-polarization mode confinement loss is 656.05dB/cm, and the difference between the X-polarization mode confinement loss and the Y-polarization mode confinement loss is far greater than 20dB/cm, which can be considered to achieve complete separation of the X-polarization mode and the Y-polarization mode.

The invention has the beneficial effects that: the plasma resonance can be easily excited, and the gold has stable chemical property and is easy to process; by arranging the hexagonal air hole array on the outer layer, the light of the base mode is limited in the core area, and the transmission of the light is facilitated.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.