阅读说明：本技术 一种空芯反谐振光纤偏振滤波器 (A kind of hollow antiresonance optical fiber polarisation filter ) 是由 肖力敏 李丽丽 于 2019-07-28 设计创作，主要内容包括：本发明属于光子晶体光纤技术领域,具体为一种空芯反谐振光纤偏振滤波器。该光纤结构包括纤芯区域和包层区域；所述纤芯区域为真空区域；所述包层区域包覆在纤芯区域外；所述包层区域由内包层和包覆在内包层外的外包层组成,所述内包层由若干毛细管等间距排布形成的环圈组成；所述内包层毛细管形成的环圈中,分布于y轴方向的毛细管内填充有金属,其余毛细管未填充金属。当纤芯模式和SPP模式满足相位匹配的条件时,两者发生谐振耦合即表面等离子体激元共振效应。本发明设计的金属填充型空芯反谐振光纤在通信波段可以实现良好的偏振滤波功能,可以实现与空芯反谐振光纤的低损耗集成,从而进一步拓宽空芯反谐振光纤的应用领域。(The invention belongs to photonic crystal fiber technical field, specially a kind of hollow antiresonance optical fiber polarisation filter.The optical fiber structure includes core region and cladding regions；The core region is vacuum area；The cladding regions are coated on outside core region；The cladding regions are made of inner cladding and the surrounding layer that is coated on outside inner cladding, and the inner cladding is made of equidistantly the arrange ring of formation of several capillaries；In the ring that the inner cladding capillary is formed, it is distributed in filled with metal in the capillary in y-axis direction, remaining capillary is not filled by metal.When core mode and SPP mode meet the condition of phase matched, it is surface plasmon resonance effect that resonance coupling, which occurs, for the two.Good polarization filtering function may be implemented in communication band in the metal filled-type hollow antiresonance optical fiber that the present invention designs, and may be implemented to integrate with the low-loss of hollow antiresonance optical fiber, to further widen the application field of hollow antiresonance optical fiber.)

1. a kind of hollow antiresonance optical fiber polarisation filter is based on surface plasmon resonance effect to realize its polarization Filter effect, which is characterized in that the optical fiber structure includes core region and cladding regions；The core region is vacuum area Domain；The cladding regions are coated on outside core region；The cladding regions are by inner cladding and the surrounding layer being coated on outside inner cladding Composition, the inner cladding are made of equidistantly the arrange ring of formation of several capillaries；The ring that the inner cladding capillary is formed In circle, it is distributed in filled with metal in the capillary in y-axis direction, remaining capillary is not filled by metal.

2. hollow antiresonance optical fiber polarisation filter according to claim 1, which is characterized in that remember the fibre of the optical fiber Core diameter isD, cladding capillaries with a thickness oft, number of capillaries isk, capillary inner diameter isd, capillary tube spacing isg；Above-mentioned light Fine structural parameters meet expression formulaD=(d+2t+g)/sin(π/k)-(d+2t)；The fibre core diameter D is 15-35 μm, packet Layer capillary thickness t is 250-400 nm, and cladding capillaries quantity k is 6-10, and capillary inner diameter d is 6-13 μm, capillary Tube spacing is 1-5 μm.

3. hollow antiresonance optical fiber polarisation filter according to claim 1 or 2, which is characterized in that the filling metal Capillary in coating metallic film or filling the micro- stick of metal, to realize the polarization filtering effect of optical fiber.

4. hollow antiresonance optical fiber polarisation filter according to claim 3, which is characterized in that the filling metal is Gold, silver or aluminum metallic material.

Technical field

The invention belongs to photonic crystal fiber technical fields, and in particular to a kind of hollow with polarization filtering function is anti-humorous Shake optical fiber.

Background technique

Polarization filter is essential important optical device in optical fiber telecommunications system and optical fiber sensing system, each Field plays its unique effect.Therefore, it minimizes, stability is good, is easy to filter with the optical fiber polarisation that other optical fiber integrate The polarizers such as device early have become research emphasis.As optical device miniaturization, integrated development trend are increasingly apparent, metal Table may be implemented by filling metal or coating metallic film in optical fiber airport in type photonic crystal fiber Polarization filter The excitation of surface plasma excimer (SPP mode), the surface etc. when meeting phase-matching condition using core mode and SPP mode The polarization filtering effect of optical fiber may be implemented in gas ions plasmon resonance effect.Metal mold photonic crystal fiber Polarization filter can be with Surface plasmon resonance effect is combined with the structural versatility of photonic crystal fiber, since its various structures is variable Property, operation wavelength adjustability, extinction ratio it is high, with the advantages characteristics such as wide, metal mold photonic crystal fiber Polarization filter is As a research hotspot.

The filling of metal is successfully realized in photonic crystals optical fiber structure and coating is to realize metal mold photonic crystal fiber The important prerequisite of Polarization filter application.Wherein, metal filled-type photonic crystal fiber can be based on high temperature pressure technology and spelling It connects pressure auxiliary molten filling technique and completes preparation, metal application type photonic crystal fiber can use high-pressure chemical vapor deposition The completions such as method, the reduction reaction precipitation method, chemical coating method based on silver mirror reaction preparation.It is real based on the success of various experimental methods Cash genotype photonic crystal fiber is made as exploring various optical fiber polarizers based on plasmon resonance effect Design is had laid a good foundation.However, many metal mold optical fiber polarisation filters are all based on solid core photonic crystal fiber It is designed.In addition, in order to separate the loss peak of two polarization direction basic modes, it usually needs such as draw in several ways Enter covering asymmetry, modification air pore size, or even fills liquid in covering airport to realize photonic crystal fiber High birefringence, this is all that the actual fabrication of polarizer brings problem.In addition, in recent years, with hollow-core photonic crystal fiber The propulsion of research, hollow-core photonic crystal fiber due to its advantageous characteristic ultrashort pulse or high power laser light transmission, optical fibre gyro, The fields such as supercontinum, Fibre Optical Sensor have broad application prospects.Therefore, grinding for hollow-core fiber polarizer is unfolded extensively Study carefully, can further push the application development of hollow-core fiber.

The present invention proposes a kind of hollow antiresonance optical fiber polarisation filter based on surface plasmon resonance effect, The optical fiber is with new structural metal filled-type hollow antiresonance optical fiber, due to its structural particularity, without in optical fiber packet The loss peak that asymmetry is separable two polarization direction basic modes is introduced in layer, can make certain wave strong point one of them The loss of polarization direction basic mode reaches peak value, and another polarization direction basic mode can then be fettered and be transmitted in a fiber, thus real The function of existing polarization filtering.

Summary of the invention

It is an object of the invention to propose a kind of extinction ratio is high, insertion loss is low, work belt is wide hollow antiresonance light Fine Polarization filter.

Hollow antiresonance optical fiber polarisation filter proposed by the present invention, be based on surface plasmon resonance effect with Realize the polarization filtering effect of optical fiber；The optical fiber structure includes core region and cladding regions；The core region is vacuum Region；The cladding regions are coated on outside core region；The cladding regions are by inner cladding and the outsourcing being coated on outside inner cladding Layer composition, the inner cladding are made of equidistantly the arrange ring of formation of several capillaries；What the inner cladding capillary was formed It in ring, is distributed in the capillary in y-axis direction and is filled with metal material, be not filled by metal material in remaining capillary.

In the present invention, the sum of capillary is generally even number.

In the present invention, the core diameter of the optical fiber isD, cladding capillaries with a thickness oft, number of capillaries isk, capillary Internal diameter isd, capillary tube spacing isg.Above-mentioned optical fiber structure parameter meets expression formulaD=(d+2t+g)/sin(π/k)-(d+2t)。Institute Stating fibre core diameter D is 15-35 μm, and cladding capillaries thickness t is 250-400 nm, and cladding capillaries quantity k is 6-10 A, capillary inner diameter d is 6-13 μm, and capillary tube spacing is 1-5 μm.

In the present invention, in the capillary of the filling metal, filler is metallic film (with coating method) or metal Micro- stick (with filling mode), to realize the polarization filtering effect of optical fiber.

In the present invention, be filled with metal material in the capillary for being distributed in y-axis direction, metal material can for gold, silver, Aluminium etc..It will be further elaborated by taking gold as an example below.

The dielectric constant expression formula of gold is defined by Drude-Lorentz model, expression formula are as follows:

Wherein, ε_∞It is high-frequency dielectric constant, ε_∞=5.9673, ω represent guide-lighting angular frequency, ω_DAnd γ_DRespectively represent plasma Body frequency and damped frequency, ω_D/ 2 π=2113.6 THz, γ_DThe THz of/2 π=15.92,It is weighted factor,= 1.09WithIndicate the frequency and spectrum width of Lorentz oscillation,=650.07 THz,=104.86 THz。

Technical staff can make various changes or modifications the present invention, such as modify optical fiber structure size, filling metal species, Method optimizings polarization filtering effect, these equivalence changes such as filling amount of metal, coating metallic film equally fall into power of the present invention Benefit requires limited range.

In metal filled-type hollow antiresonance optical fiber proposed by the present invention, filled in the capillary for being distributed in y-axis direction Metal can inspire each rank SPP mode in filling metal surface, when to meet with SPP mode mode simultaneously effective for core mode When refractive index and the identical condition in polarization direction, that is, meet phase-matching condition.For example, being made by changing optical fiber structure parameter Core mode the implementation pattern effective refractive index at different wave length is identical with SPP mode and the identical condition in polarization direction, i.e., Meet phase-matching condition.

Core mode will occur resonance with SPP mode and couple, and cause energy to be transferred to wire surface from fibre core and be excited SPP mode.And due to the high loss characteristic of SPP mode, the loss of the polarization direction fibre core basic mode reaches peak value.It is being based on In the Polarization filter of solid core photonic crystal fiber, it usually needs pass through the size of change airport, arrangement mode in a fiber To introduce the birefringent separation to realize two polarization direction fundamental mode loss peak values, this also brings for actual fabrication even filling liquid Difficulty.And due to the unique structure of hollow antiresonance optical fiber, the dispersion curve of each rank different polarization direction SPP mode can be with It is automatically separated, so that the high loss peak of two polarization direction basic modes occurs at different wave length respectively, shows that metal filled-type is empty Core antiresonance optical fiber is advantageous to the design of hollow-core fiber Polarization filter.

The invention has the beneficial effects that:

1. photonic crystal fiber of the present invention is hollow antiresonance optical fiber, without changing the big of optical fiber inner cladding capillary The small separation being automatically separated to realize two polarization directions fundamental mode loss peak that different polarization direction SPP mode can be realized；

2. photonic crystal fiber of the present invention is hollow antiresonance optical fiber, the capillary diameter of metal is filled compared to other The airport of metal mold photonic crystal fiber filling metal is relatively large in diameter, it is easy to accomplish the selective filling of metal；

3. hollow antiresonance optical fiber polarisation filter proposed by the invention has High Extinction Ratio, low insertion loss, wide work belt The advantages that wide.

Detailed description of the invention

Fig. 1 is metal filled-type hollow antiresonance optical fiber structure schematic diagram in the embodiment of the present invention.

Fig. 2 is by the x-polarisation that metal filled-type hollow antiresonance optical fiber excites in the embodiment of the present invention and y-polarisation direction The mould field figure (a-f) of each rank SPP super model.

Fig. 3 is the fibre core basic mode of metal filled-type hollow antiresonance optical fiber and the mode of SPP super model in the embodiment of the present invention Dispersion curve figure.

Fig. 4 is the fibre core fundamental mode loss curve graph of metal filled-type hollow antiresonance optical fiber in the embodiment of the present invention.

Fig. 5 is that metal filled-type hollow antiresonance optical fiber is inclined in different resonance wave strong point x-polarisations and y in the embodiment of the present invention The mould field figure of vibration direction fibre core basic mode.

Fig. 6 is the Extinction ratio curve graph of metal filled-type hollow antiresonance optical fiber in the embodiment of the present invention.

Fig. 7 is that metal filled-type hollow antiresonance optical fiber and metal are not filled by type hollow antiresonance light in the embodiment of the present invention The integrated schematic diagram of fibre.

Fig. 8 is that metal is not filled by type hollow antiresonance optical fiber x-polarisation and y-polarisation direction fibre core base at 1550 nm wavelength X-polarisation and y-polarisation direction are fine at 1550 nm wavelength in the mould field figure (a, b) and metal filled-type hollow antiresonance optical fiber of mould The mould field figure (c, d) of core basic mode.

Specific embodiment

In order to which the present invention is described in more detail, specific with reference to the accompanying drawing the present invention is further elaborated.

Fig. 1 is novel metal filled-type hollow antiresonance optical fiber structure schematic diagram proposed by the invention, including air fibre Core, the circle capillary inner cladding for being looped around fiber core, the surrounding layer that is coated on outside capillary ring and in y-axis direction The metallic gold filled in capillary.The diameter of air-coreDIt is 20 μm, the quantity k of quartz capillary is 8, each quartz wool The interior diameter of tubuledIt is 10 μm, capillary thickness is 362 nm, and the gap of adjacent capillaries is that g is 1.03 μm.

Each rank SPP super model that Fig. 2 (a-d) is excited by metal filled-type hollow antiresonance optical fiber proposed by the invention Mould field figure, wherein arrow indicates its polarization direction.As shown in Fig. 2 (a-d), metal filled-type hollow antiresonance optical fiber will be in y Filling metal surface in axis direction capillary inspires each rank SPP super model in x-polarisation and y-polarisation direction, such as x-SPP0a, x- SPP0b, y-SPP1a, y-SPP1b, x-SPP2a, x-SPP2b mode, and can be seen that according to the mould field figure of each rank SPP super model The polarization direction of x-SPP0b, y-SPP1b and x-SPP2b super model is identical, and x-SPP0a, y-SPP1a and x-SPP2a super model Polarization direction be opposite.

Fig. 3 is the fibre core basic mode of metal filled-type hollow antiresonance optical fiber proposed by the invention and the mode of SPP super model Dispersion curve figure.It can be found that the dispersion curve of each rank SPP super model all can be with x-polarisation and y-polarisation direction fibre core base from Fig. 3 The dispersion curve of mould intersects, but the effective refractive index of fibre core basic mode only fibre core basic mode with identical polarization direction SPP super model Dispersion curve intersection occur obviously increasing.That is, SPP super model and fibre core basic mode with opposite polarization Dispersion curve intersection when can't have a significant effect to the dispersion curve of core mode, only with identical polarization direction SPP super model just meets phase-matching condition when intersecting with the dispersion curve of fibre core basic mode, so that the polarization direction fibre core basic mode There is obvious rise in dispersion curve.

Fig. 4 is the fibre core fundamental mode loss curve graph of metal filled-type hollow antiresonance optical fiber proposed by the invention.Work as tool When having the SPP super model of identical polarization direction and fibre core basic mode to meet phase-matching condition, the fibre core basic mode of the polarization direction can To be coupled to the SPP super model of metal surface excitation, due to the high loss characteristic of SPP mode, the loss of the polarization direction basic mode Peak value is reached, as shown in Figure 4.Due to automatic point of the modal dispersion curve of x-polarisation in Fig. 3 and y-polarisation direction SPP super model From, so that x-polarisation and the loss peak of y-polarisation direction basic mode occur at different wave length, the loss peak point of x-polarisation direction basic mode Occur not at 1447 nm and 1550 nm wavelength, and the loss peak of y-polarisation direction basic mode appears in 1493 nm, so as to Realize the polarization filtering function of hollow antiresonance optical fiber.At 1550 nm wavelength, the loss of x-polarisation direction basic mode is 45.52 DB/cm, and the loss in y-polarisation direction is 0.60dB/cm, therefore the polarization filtering at 1550 nm of communication wavelengths may be implemented.

Fig. 5 is that metal filled-type hollow antiresonance optical fiber proposed by the invention is inclined in different resonance wave strong point x-polarisations and y The fibre core foundational model field figure in vibration direction.As shown, at 1447 nm and 1550 nm wavelength, the basic mode and tool in x-polarisation direction There is the SPP super model of identical polarization direction obvious coupling phenomenon occur, part mode distributions are in metal surface, and y-polarisation direction The mould field of basic mode is then strapped in fibre core.At 1493 nm wavelength, the basic mode in y-polarisation direction with identical polarization direction There is obvious coupling in SPP super model, and the mould field of the basic mode in x-polarisation direction can be then strapped in fibre core.

The Extinction ratio that Fig. 6 is metal filled-type hollow antiresonance fiber lengths proposed by the invention when being 1 centimetre is bent Line chart.Extinction ratio is the important parameter for measuring Polarization filter filtering characteristic, when extinction ratio is greater than 20dB or is less than -20dB When, the light in x-polarisation direction and y-polarisation direction can be separated well and (be filtered the light in wherein some direction by Polarization filter Fall), and the higher filter effect of extinction ratio is better.Can significantly it find out from figure, at 1550 nm wavelength, polarization extinction It is 44.92dB than ER, y-polarisation direction fundamental mode loss is 0.60dB/cm, and bandwidth of operation of the extinction ratio greater than 20dB is 41 nm, Designed metal filled-type hollow antiresonance optical fiber can be realized well in the wave-length coverage of 1528 nm to 1569 nm Polarization filtering effect.

Fig. 7 is that metal filled-type hollow antiresonance optical fiber and metal proposed by the invention are not filled by type hollow antiresonance light The integrated schematic diagram of fibre, the both ends of metal filled-type hollow antiresonance optical fiber are not filled by type hollow antiresonance optical fiber phase with metal respectively Welding, wherein the hollow antiresonance optical fiber of right end should be polarization maintaining optical fibre to keep the basic mode in y-polarisation direction at 1550 nm wavelength Stablize transmission.Consider the factors such as the mould field size of fiber end face, model shape, Fresnel reflection, it is anti-to be not filled by metal mold hollow The coupling loss of the docking point of resonator fiber optic and added metal type hollow antiresonance optical fiber are as follows:

Wherein E_i, H_i (E_t, H_t) it is the normalization electric and magnetic fields vector for being not filled by optical fiber (filling optical fiber) basic mode respectively.Its Middle normalization expression formula are as follows:

Wherein, A is cross section of optic fibre area；For the unit vector in the direction z.

Fig. 8 (a, b) is respectively that metal is not filled by type hollow antiresonance optical fiber x-polarisation and y-polarisation side at 1550 nm wavelength To the mould field figure of basic mode；Fig. 8 (c, d) is respectively x-polarisation and y at 1550 nm wavelength in metal filled-type hollow antiresonance optical fiber The mould field figure of polarization direction basic mode.Type hollow antiresonance optical fiber and metal filled-type are not filled by for metal proposed by the invention Hollow antiresonance optical fiber integrates, and the coupling loss of x-polarisation direction and y-polarisation direction basic mode is respectively at 1550 nm wavelength The coupling loss of 3.78 dB and 0.02 dB, x-polarisation direction basic mode are significantly greater than the coupling loss of y-polarisation direction basic mode, this is Since at 1550 nm wavelength, x-polarisation direction basic mode is coupled with SPP super model generation resonance leads to its part mould field energy localization In cladding capillaries metal surface, and the mould field of y-polarisation direction basic mode can be very good to be strapped in fibre core, such as Fig. 8 (a-d) institute Show.X-polarisation direction basic mode is greater than y-polarisation direction basic mode in the coupling loss of the docking point of two kinds of optical fiber to be damaged in the coupling of docking point Consumption can further enhance the polarization filtering effect of the metal filled-type hollow antiresonance optical fiber.Further, since filling metal point It is distributed in optical fiber middle position, therefore the coupling loss of both ends splice point requires to consider.In addition, small between identical hollow-core fiber The insertion loss of y-polarisation direction basic mode can be made to be significantly less than 0.5 dB in the splice loss, splice attenuation of 0.2 dB, show that the metal is filled out The basic mode for filling the y-polarisation direction of type hollow antiresonance optical fiber, which can be very good to be strapped in fibre core, to be transmitted.As stated above, of the invention The metal filled-type hollow antiresonance optical fiber polarisation filter proposed can realize polarization extinction at 1550 nm of communication band Than for 44.92 dB, for insertion loss less than 0.5 dB, bandwidth of operation is the good polarization filtering effect of 41 nm.