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A polarization filter is designed at two communication windows of 1310 and 1550 nm based on microstructured optical fiber. The model has four large diameter air holes and two gold-coated air holes. The influence of the geometrical parameters of the photonic crystal fiber on the performance of the polarization filter is analyzed by the finite element method. The numerical simulation shows that when the fiber length is 300 μm, the corresponding extinction ratio is 209.7 dB and 179.8 dB, the bandwidth of extinction ratio (ER) better than 20 dB is 150 nm and 350 nm at the communication wavelength of 1310 nm and 1550 nm. [ABSTRACT FROM AUTHOR]

A broad bandwidth polarization filter based on photonic crystal fiber (PCF) coated with gold layer is proposed and simulated by the full vector finite element method. The surface plasmon resonance coupling theory is studied, and the factors that affect the polarization filtering effect are analyzed. By changing the structural parameters of the PCF, we realize polarization filter at 1.55 and 1.48 μm. In the designed polarization filter, the maximum loss of the unwanted y-polarization at 1.55 μm is 803.56 dB/cm and at 1.48 μm is 732.69 dB/cm. Besides, a broad bandwidth of 1000 nm with the crosstalk better than 20 dB is obtained. The suggested PCF is competitive for polarization device. [ABSTRACT FROM AUTHOR]

A novel photonic crystal fiber polarization filter with Au-coated and liquid-filled air holes is designed in this paper. The coupling theory is introduced to explain the complete coupling and incomplete coupling. We can adjust the resonance point to the communication band by optimizing the parameters of the fiber structure. Numerical simulation results demonstrate that the resonance strength can reach 434 dB cm −1 at the communication wavelength of 1.31 μm in x-polarized direction. By filling liquid analyte can help adjust the resonance peak to the proper place. Furthermore, when the fiber length of L equals to 0.1 cm, the crosstalk peak value can reach 353.74 dB at the wavelength of 1.31 μm, and the bandwidth of the crosstalk better than 20 dB can reach 80 nm when the length of the fiber L is 400 μm. These characteristics make it a promising candidate for designing new types of polarization filter devices. [ABSTRACT FROM AUTHOR]

We design a crystal photonic fiber (PCF) polarization filter with asymmetric structure and two large air-holes coated with gold film. The influence of the thickness of metal layers and the diameter of large air-holes on the filtering characteristic is investigated using finite element method (FEM). In calculations, the sixth and the third order surface plasma modes (SPM) are presented. The resonance positions are well separated by the asymmetry of the structure in vertical direction. The loss of unwanted polarization is 829 and 1267 times than that of wanted polarization at 1.48 and 1.55 μm respectively. When the fiber length is 3 mm, the crosstalk is 1055 dB and 927 dB for 1.48 and 1.55 μm. The bandwidth with crosstalk better than 20 dB can reach to 1000 nm, covering almost all communication band. What’s more, gold excitation of SPR and silver excitation of SPR are compared and studied. [ABSTRACT FROM AUTHOR]

In recent years, photonic crystal fibers have played an important role in the field of optical communications, and the addition of metal materials to photonic crystal fibers have offered new ways to improve the transmission characteristics of optical fibers. We design a new type of gold-coated photonic crystal filter, which utilizes the surface plasmon resonance effect, and study it by using the finite element method. In this paper, we optimise the structure parameters and analyze the numerical results. The numerical results show that the thickness of metal layer and the air holes near the fiber core strongly affect the performance of the polarization filter. For the operating wavelength of 1550 nm, the loss in the y-polarization direction can be as high as 906.9 dB/cm, which is much larger than the x-polarization direction. When the fiber length is longer than 100 μm, the crosstalk in the wavelength range from 1.4 μm to 1.9 μm is greater than 20 dB. The proposed optical fiber can find application as an optical fiber polarization filter. [ABSTRACT FROM AUTHOR]

A kind of polarized filtering photonic crystal fiber (PCF) with nanoscale gold film is studied by using the finite element method. The cross-section structure of the PCF is composed of a hexagonal lattice of air holes in which an air hole is gold coated, and the air-hole layout is modified. By our structure, the loss of x-polarized mode is further larger than the loss of y-polarized mode and the loss peak appears at the wavelength 1.31 μm. The corresponding loss in x-polarized can reach a value of 85,780 dB/m at the resonance wavelength. It can be used for the communication windows of 1.31 μm which can be used for carrying data/voice. When the length of fiber is longer than 30 μm, the extinction ratio is better than 20 dB at the wavelength 1.31 μm. When the length of fiber is longer than 210 μm, the extinction ratio is better than 20 dB with the wavelength ranging from 1.26 to 2 μm. The broadband polarized filtering PCF covering 740 nm is achieved. [ABSTRACT FROM AUTHOR]

A kind of photonic crystal fibre polarization filter with round lattice based on surface plasmon resonance is proposed. Complete coupling happens between core mode and second-order surface plasmon polariton (SPP) mode when the phase-matching condition is satisfied. We can adjust the resonance point and strength in two polarizations by changing the fibre birefringence and the thickness of gold film. Numerical simulation with the finite-element method shows that the resonance strength can reach 364.8 dB/cm in they-polarized direction at the communication wavelength of 1550 nm, when the diameter of big air holes that lead to the birefringence is 2.0 m and the thickness of gold film is 26 nm. Moreover, when the fibre length is 800 m, the peak value of the crosstalk can reach 231.8 dB and the bandwidth of the crosstalk better than 20 dB can reach 130 nm. This makes it a promising candidate for polarization filter devices. [ABSTRACT FROM PUBLISHER]

The Au film and glycerin selectively infilling photonic crystal fibers are analyzed by the finite element method. One cladding air hole is coated with Au film and infiltrated with glycerin to form a defect core. The simulation results show that both of the defect core modes formed on the glycerin and Au film can inspire resonance with core modes. The maximum sensitivity can reach to 2.50 nm/ C in x polarized direction and 2.00 nm/ C in y polarized direction for the temperature sensor, respectively. Furthermore, we obtain that the confinement losses of the photonic crystal fibers (PCFs) can meet with 321.442 dB/cm and 445.958 dB/cm at a short wavelength band (1460 ∼1530 nm) and an extended wavelengths band (1360 ∼1460 nm) for x polarized direction and y polarized direction respectively, which can be applied in many polarization filter devices as well. The compatibility of temperature sensor and polarization filter based on an identical structure can be realized at different wavelengths. [ABSTRACT FROM AUTHOR]

A polarization filter at the two communication windows of 1.31 and 1.55 μm based on photonic crystal fiber (PCF) coated by nanoscale gold film is proposed. The effects of geometrical parameters of the PCF on the performances of polarization filter are evaluated by finite element method (FEM). Numerical simulations reveal that the polarization filter possesses ultra-short length of 400 μm and high extinction ratios of 41 and −150 dB at the communication wavelengths of 1.31 and 1.55 μm respectively. The bandwidth of extinction ratio (ER) better than 20 dB is 58 nm at the communication window of 1.31 μm. Moreover, the bandwidth of ER better than −20 dB is 164 nm at the communication window of 1.55 μm. [ABSTRACT FROM AUTHOR]

The polarization filter characteristics of Au wires and liquid crystal infiltrated photonic crystal fibers are investigated by using the finite element method. The nematic liquid crystal of E7 being injected into cladding air holes is benefit to induce large birefringence under controllable electrical field. The simulation results show that the surface plasmon resonance is strongly inspired by core modes in y-polarized direction. Meanwhile, the coupling between core modes in x-polarized direction and surface plasmon polaritons modes is faint. The confinement losses can achieve 446 dB/cm in y-polarized direction and 0.8 dB/cm in x-polarized direction at wavelength of 1550 nm in one of our designed fiber. The effects of fiber structural parameters and temperature are investigated with a view of tuning and optimizing the confinement loss spectrum. Own to the large contrast of confinement losses in two orthogonal directions, the designed Au wires and liquid crystal infiltrated photonic crystal fibers promise candidate for tunable polarization filter devices. [ABSTRACT FROM AUTHOR]

An ultrabroad bandwidth polarization filter based on D-shaped photonic crystal fibers with gold film is proposed. The design of gold film deposited on the polished plane of the D-shaped photonic crystal fibers is benefit to generate multiple resonances between surface plasmon polaritons and photons. In our designed polarization filter, the resonant intensity in y-polarization direction is much stronger than in x-polarization direction. An ultrabroad bandwidth of exceeding 1 μm with extinction ratio better than -20 dB is obtained. The performance characteristics of the filter can be improved further by optimizing the structure parameters of the D-shaped photonic crystal fibers. [ABSTRACT FROM AUTHOR]

A broadband single-polarization photonic crystal fiber polarized filter based on surface plasmon resonance is proposed based on finite element method. Numerical simulations show the confinement loss of y-PCM (y-polarized core mode) is much higher than that of x-PCM (x-polarized core mode) in the wavelength range 1.20-1.63 μm. The confinement loss of y-polarized mode is 45,240 and 10,200 dB/m at the communication wavelength 1.31 and 1.55 um, respectively, and the corresponding loss of x-polarized mode is just 90 and 80 dB/m. When the fiber length is 3 mm, the bandwidth of extinction ratio better than -20 dB is greater than 430 nm covering almost all the communication wavelength. To our best knowledge, the bandwidth is the widest. The impacts of structural parameters on the resonance characteristics are also discussed. The structure could be further optimized for better result. [ABSTRACT FROM AUTHOR]

Highlights • The proposed PCF filter can realize three kinds of filtering effects. • Two ultra-large air holes makes the process of plating gold film more convenient. • Ultra-high crosstalks and losses can be obtained at the communication windows. • The filtering bandwidth can reach 700 nm at the communication window of 1550 nm. Abstract In this study, we present a single-polarization photonic crystal fiber filter. The metallic gold is used as the surface plasmon resonance activity material, which is deposited on the inner wall of the two ultra-large holes. The properties of the photonic crystal fiber filter are investigated by the finite element method. By adjusting the structural parameters and gold film thickness, three kinds of filtering effects can be obtained at the communication windows. When the length of the optical fiber is 1 mm, one of the filtering effects can achieve loss of 588.900 dB/cm at the communication window of 1310 nm, and the corresponding filtering bandwidth equals to 270 nm; the other two kinds of filtering effects can be applied to the communication window of 1550 nm, and the losses are 569.682 and 971.330 dB/cm and the corresponding filtering bandwidths equal to 700 and 630 nm, respectively. The proposed photonic crystal fiber filter shows great advantages compared with some previous reports on filtering. [ABSTRACT FROM AUTHOR]

A dual communication band single-polarization photonic crystal fibre polarizing filter based on surface plasmon resonance is presented in this paper. Numerical simulation results demonstrate that the resonance strength of x- and y-polarized direction can reach 569.83 and 719.25 dB.cm−1 simultaneously at the communication wavelength of 1.31 and 1.55 µm. By filling liquid analyte, the confinement loss of x- and y-polarized direction can simultaneously reach 831.7 and 580.53 dB.cm−1 at the wavelength of 1.31 and 1.55 µm. Furthermore, when the fibre length L is equal to 700 µm, the peak value of the crosstalk can reach 493.86 and −323.67 dB at the same time at the wavelength of 1.31 and 1.55 µm, and when the length of the fibre L is 400 µm, the bandwidths of the crosstalk better than 20 dB and less than −20 dB are about 160 and 210 nm, respectively. These performances make it an ideal candidate for designing dual-band polarization filter equipment. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance induced tunable broadband polarization filters based on photonic crystal fibers (PCFs) were designed and investigated. The characteristics of the designed PCF were calculated by using the finite element method (FEM). The air holes in the PCFs which were arranged in hexagonal lattice were of the same size except one big air hole. The big air hole which was located on the right side of the fiber core was designed to be coated with gold film in the inner wall. Because of the arrangement of the big air hole, the surface plasmon resonance inspired on the surface of gold film was quite different for the two orthogonal polarized incident lights. As the edge of the big air hole approaching the adjacent air holes, the plasmon modes were influenced strongly by the adjacent air holes and as a results the cascaded resonances appeared. The index-matching liquid infilling in the big air hole was used to adjust the resonant wavelengths and strength. Numerical simulation results showed that the bandwidth of the polarization filter was 1200 nm covering the wavelengths from 1.0 μm to 2.2 μm with high extinction ratio (ER). [ABSTRACT FROM AUTHOR]

A dual communication band photonic crystal fiber polarizing filter based on coupling between core mode and SPP mode is proposed in this paper. By optimizing the parameters of the fiber structure, the resonant points can be tuned to the communication band. Numerical simulation results demonstrate that the resonance strength of x - and y -polarized direction can simultaneously reach 729.47 and 542 . 78 dB ⋅ cm − 1 at the communication wavelength of 1.55 and 1.31 μ m . By filling liquid analyte the confinement loss of x - and y -polarized direction can simultaneously reach 580.55 and 714 . 48 dB ⋅ cm − 1 at the wavelength of 1.55 and 1.31 μ m . Furthermore, when the fiber length of L is equal to 700 μ m , the peak value of the crosstalk can reach 421.89 and − 322 . 34 dB at the same time at the wavelength of 1.31 and 1.55 μ m , and when the length of the fiber L is 400 μ m , the bandwidths of the crosstalk better than 20 dB and less than − 20 dB are about 170 and 220 nm, respectively. These properties make it an ideal candidate for designing dual-band polarization filter equipment. [ABSTRACT FROM AUTHOR]

We propose a modified design for a photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR). The air holes are arrayed in diamond lattices, and the diameter of the holes around the gold-coated holes are different that can separate the refractive index of the x-polarization and y-polarization second order surface plasmon polariton (SPP) modes. The influences of structural parameters of the photonic crystal fiber (PCF) on the filter characteristics are studied using the finite element method (FEM). Great changes have taken place in the results of numerical simulation by changing the thickness of the gold film and air hole diameter. Simulation results show that the resonance wavelength is communication wavelength 1550 mm, the loss of the y-polarization mode is 43,126.7 dB/m. When the length of the fiber is 500 μm, extinction ratio is more than 20 dB at the communication wavelength, and bandwidth achieve to 190 nm. It is an important property of PCF polarization filter in production. [ABSTRACT FROM AUTHOR]

A chalcogenide hollow-core anti-resonance fiber (HC-ARF) filter based on surface plasmon resonance (SPR) at 3 μm band is designed. The substrate materials are As40S60 and GeAsS, which are used to create the conditions for the formation of SPR, so as to realize the directional energy coupling in the specific polarization direction of the fiber. The effects of core diameter, capillary radius, and capillary wall thickness on the polarization performance of HC-ARF filter are analyzed by full-vector finite element method (FV-FEM). The numerical results show that the confinement loss of x-polarized fundamental mode (FM) reaches 1917.24 dB/m at the wavelength of 3.02 μm, while that of y-polarized FM is 23.11 dB/m. When the fiber length is 8 mm, the bandwidth with extinction ratio (ER) better than 20 dB covers the wavelength range of 320 nm. In addition, the resonance wavelength can be effectively adjusted by changing the capillary wall thickness. The proposed HC-ARF filter has potential applications in biomedicine, scientific research, and atmospheric detection. [ABSTRACT FROM AUTHOR]

A broadband core shift photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance is proposed in this paper. The fiber is consisted of an asymmetric hexagonal lattice of holes in which a small air hole is coated with gold film and another one large air hole destroyed the structure around the core. The loss of y-polarized core mode is 2232.61 dB/cm at the communication wavelength of 1.55 μm, however, the loss of x-polarized core mode is very weak. When the PCF length is 300 μm, the bandwidth of exceeding 420 nm with extinction ratio better than −20 dB is achieved. To our best knowledge, the bandwidth is the widest. As a consequence, this special fiber filter has a wider range of applications. [ABSTRACT FROM AUTHOR]

A square structure of dual communication band single polarizing plasma photonic crystal fiber filter is presented in this paper. The resonance point can be adjusted to the communication band by optimizing the parameters of fiber structure. High birefringence can be produced by changing the refractive index of the filled liquid, the thickness of the metal film, and the diameter of the air holes near the core. Numerical simulation results demonstrate that the resonance strength of x - and y -polarized direction can simultaneously reach 781.87 and 463.04 dB cm −1 at the communication wavelength of 1.31 and 1.55 μm. By filling liquid analyte the confinement loss of x - and y -polarized direction can simultaneously reach 804.71 and 451.69 dB cm −1 at the wavelength of 1.31 and 1.55 μm. Furthermore, when the fiber length of L is equal to 700 μm, the peak value of the crosstalk can reach 474.63 and −243.61 dB at the same time at the wavelength of 1.31 and 1.55 μm, and when the length of the fiber L is 400 μm, the bandwidths of the crosstalk better than 20 dB and less than −20 dB are about 160 and 220 nm, respectively. These features make it an ideal candidate for the design of a dual band polarization filter device. [ABSTRACT FROM AUTHOR]

In this paper, a photonic crystal fiber with the gold layer is simulated by finite element method. Due to birefringence, surface plasmon resonance only occurs in the y-polarization direction. The loss of y-polarization mode is much larger than that of x-polarization mode. The photonic crystal fiber is suitable for the polarization filter. The polarization filter has the short length and high extinction ratio. Furthermore, the insertion loss of the x-polarization mode is only 0.07 dB, which is the smallest as far as we know. [ABSTRACT FROM AUTHOR]

We propose a modified design for a Core shift photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance. The Core shiftting is achieved by the air holes with different diameters around the gold-coated holes, which can separate the refractive index of the x-polarization and y-polarization second order surface plasmon polariton modes. The influences of structural parameters of the PCF on the filter characteristics are studied using the finite element method. Simulation results great changes have taken place in the results of numerical simulation by changing the thickness of the gold film and air hole diameter. We obtain a resonance wavelength with 1550 nm. The y-polarization mode is supressed significantly with the loss of 58,456.7 dB/m. With the length of the fiber is 300 μm, a extinction ratio is higher than 20 dB and a bandwidth achieve to 450 nm at the communication wavelength can be got. All these properties we achieved in the core shift PCF are important properties of PCF in broadband polarization filter in application. Our design can offer some guidance to the production of the polarization filter. [ABSTRACT FROM AUTHOR]

A single-polarization photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) is proposed. Finite element method is employed in simulating the PCF with gold-coated. The resonance wavelength can be modulated by changing the thickness of gold layer. At the resonance wavelength 1.55 μm, the loss of y-polarized mode is much larger than the loss of x-polarized mode. When the fiber length is set to 2 mm, the value of extinction ratio reaches to −118.7 dB, the y-polarized mode is suppressed and only x-polarized mode can be guided. The fiber is applicable in the production of single-polarization filter. The PCF has a simple structure and a big error tolerance, it has a good practicability. [ABSTRACT FROM AUTHOR]

In this work, we propose an octagonal photonic crystal fiber (PCF) filter based on tellurite. Selective gold coating in air holes couples the core mode to a surface plasmon mode. The finite element method is used to analyze the structure in the mid-infrared band. The simulated results and analysis show that the losses in the y and x polarization modes at 2.55 µm are 2063.2 and 21 dB/cm, respectively. Therefore, the unwanted y-polarization mode is filtered out. The higher loss ratio optimizes the formant position and intensity of surface plasmon mode and core mode. When the fiber length of the filter is optimized to 500 µm, the extinction ratio of − 102 dB is achieved at 2.55 µm. Consequently, the single polarization transmission with a 500 nm width is realized. When the length of the fiber is greater than 500 µm, it realizes the 1500 nm (2.2–3.7 µm) ultra-wideband filtering. We also analyze the manufacturing feasibility of the proposed PCF and the influence of structural parameters on the limiting loss characteristics. • Introduce a new type of substrate material: TZLB, which breaks the limitation of conventional quartz glass. • The loss of the y-polarization state is much higher than the x-direction. • When the fiber length is 500 µm, the ER reaches −102 dB and the effective filtering range is 2.4‐2.9 μm. • When the fiber length is greater than 500 µm, it achieves the 1500 nm ultra-wideband filtering. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance (SPR) biosensor based on dual-side polished photonic crystal fiber (PCF) has been presented in this paper. An external gold (Au) coating was used as a plasmonic material to detect changes in an analyte refractive index (RI). Sensor’s structural parameters were optimized for better performance. The proposed sensor’s simulation was conducted using the finite element method (FEM). Analytes within the RI range of 1.30 to 1.40 were used to develop a sensor. The numerical results are expected to have a wavelength sensitivity (WS) of 9400 nm/RIU and amplitude sensitivity (AS) of 27.27 RIU−1, respectively, and a spectral wavelength resolution of 1.063 × 10−5. Furthermore, it is expected to obtain maximum loss of 161,270 dB/m for a Y-polarization (Y-P) odd mode with an analyte RI = 1.37. We obtained an extinction ratio of − 321.54 dB for the polarization filter effect, which is considered to be good. This structure has the advantages of being easy to fabricate, affordable, and expected to show better sensitivity than many other sensors. It assumes to detect a wide range of analytes, making it suitable for organic chemical sensing, pharmaceutical inspection, and biosensor applications. [ABSTRACT FROM AUTHOR]

Highlights • The PCF is simple, novel and easy to apply. • The filter can simultaneously achieve polarization filtering effects on the input signals of the 1310 and 1550 nm communication bands. • When the length of the PCF is 0.8 mm, the crosstalk is less than −20 dB or better than 20 dB in the 1550 and 1310 nm bands, the optical bandwidth can reach 220 and 150 nm, respectively. Abstract A photonic crystal fiber (PCF) polarization filter with dual communication bands is proposed in this paper. The polarization characteristics of the double-hole gold-coated PCF are numerically analyzed by utilizing the finite element method (FEM). As we know, the filter can achieve polarization filtering effect on input signals at 1310 nm (y-polarized mode) and 1550 nm (x-polarized mode) bands simultaneously in two orthogonal polarization states. In the above two communication bands, the confinement losses of the unwanted polarization mode can reach 192.7 dB/cm (y-polarized mode) and 427.5 dB/cm (x-polarized mode), whereas other polarization mode losses are very low. Furthermore, when the transmission length of the PCF is 800 μm, x and y polarization mode crosstalk can reach −275.4 and 126.9 dB in the 1550 and 1310 nm bands, respectively. Meanwhile, the crosstalk is less than −20 dB or better than 20 dB, the optical bandwidth can reach 220 and 150 nm, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a dual-polarizated photonic crystal fiber filter (PCF) based on surface plasmon resonance (SPR) was proposed. Its polarization characteristics were numerically researched by finite element method (FEM). The results indicate that the polarization filtering of the filter be able to fulfill in dual communication bands of 1310 and 1550 nm. The confinement loss reaches 80,711.4 dB/m for the x polarization core mode at the wavelength of 1310 nm, while 46,614.5 dB/m for the y polarization core mode at the wavelength of 1550 nm. When the length of PCF is 2.5 mm, the extinction ratios of x and y polarization core modes can achieve 1705.27 and − 883.46 dB, respectively. For the communication windows of 1310 and 1550 nm, the filtering bandwidths can reach to 390 and 350 nm, respectively. These excellent characteristics are beneficial to the design and manufacture of filter devices. • A PCF dual windows polarization filter based on SPR is proposed. The square arrangement of air holes is easy to prepare. • The losses of the filter at dual windows can reach 80,711.4 dB/m and 46,614.5 dB/m. • When L PCF = 2.5 mm, the ER of the two orthogonal modes can reach 1705.27 and − 883.46 dB. The bandwidth can reach 390 nm and 350 nm. [ABSTRACT FROM AUTHOR]

In this paper, an asymmetric photonic crystal fiber (PCF) polarization filter near the gold-clad hole based on surface plasmon resonance (SPR) is proposed. The outer walls of the two air holes in the y-direction are coated with a gold film, and the two kinds of cladding air holes are introduced near the coated holes to increase the difference in the coupling strength of x and y polarization modes and SPP modes, thus separating the two polarization states. The finite element method is used to study the characteristics of the polarization filter, and the result shows that the polarization loss in the y-direction is as high as 1565.98 dB/cm at 1. 55 μ m , while the loss in the x-direction is relatively small. When the fiber length is 1 mm, the crosstalk peak reaches 1322.7 dB. From 1 μ m to 2 μ m (range: 1000 nm), the crosstalk is always greater than 20 dB. If four kinds of pores with different sizes are used in the cladding layer, the symmetry around the gold-coated holes will be destroyed, and a better filtering effect can be obtained. The excellent performance of the proposed polarization filter makes it a good candidate material for broadband polarization filters. • Propose a new idea for filter design: improve the asymmetry near the gold-clad hole. • The loss peak in y-polarization is much higher than in x-polarization at communication wavelength 1.55 μ m. • When the fiber length is 1 mm, the crosstalk peak reaches 1322.7 dB. From 1 μ m to 2 μ m, the crosstalk is always greater than 20 dB. • The higher the asymmetry near the gold-plated hole, the better the polarization filtering performance. [ABSTRACT FROM AUTHOR]

• The polarization filter we designed is novel and have a high performance. • The loss peak in Y-polarization is much higher than in X-polarization. • Air-holes except the innermost layer also influence the loss peak well. • The PCF filter can be widely used in system integration. In this study, a novel photonic crystal fiber (PCF) polarization filter has been designed. To resonate the surface plasma mode with the core mode, gold is selectively filled in the air holes. Using numerical simulations based on the finite element method, the influence of structural parameters on the filter is analyzed, and a set of rules for designing the PCF polarization filter is determined. The numerical simulation shows that the peak loss in the y-polarization direction at 1.31 μm reaches 1209.57 dB/cm, whereas the peak loss in the x-polarization is close to zero. Working at 1310 nm in the communication band, a new type of PCF is designed using these characteristics. [ABSTRACT FROM AUTHOR]

A novel polarization filter based on photonic crystal fiber with two open-ring channels is proposed. The optical device is compatible with both broadband filtering and sensing. The calculation results show that the loss of the y-polarized core mode is as high as 1147.79 dB/cm at a communication wavelength of 1.55 μm, while the loss of the x-polarized core mode is only 1.86 dB/cm. When the length of PCF is 800 μm, the optical bandwidth of crosstalk greater than 20 dB can reach 790 nm at the wavelength band of 1.55 μm, and the corresponding crosstalk peak is 796.4 dB. In addition, the simulation results show that the proposed PCF is applied in the field of sensing as long as the thickness of the gold film is changed from 22.5 nm to 40 nm. Further, when the refractive index of the tested material varies from 1.32 to 1.37, the average sensitivities of 3057 nm/RIU and 1000 nm/ RIU are obtained in x- and y-polarized modes, respectively. [ABSTRACT FROM AUTHOR]