Liquid Core Photonic Crystal Fiber Research Articles

Coherence analysis of supercontinuum generation in nitrobenzene liquid-core photonic crystal fiber based on adaptive step-size methods

Coherence analysis of supercontinuum generation in nitrobenzene liquid-core photonic crystal fiber based on adaptive step-size methods

Cascaded anti-resonant reflecting waveguides for simultaneous measurement of temperature and curvature

An optical fiber sensor based on combined anti-resonant reflecting (ARR) mechanism is experimentally demonstrated for simultaneous measurement of temperature and curvature. The sensor head consists of a section of liquid infiltrated simplified hollow core photonic crystal fiber (PCF) spliced to a section of silica capillary. Two types of ARR mechanisms are involved in the sensor structure: the double-layer ARR guidance in the infiltrated PCF, and the single-layer ARR guidance in the silica capillary, which result in two sets of ARR fringes in the transmission spectrum. Due to the difference in the guiding mechanism and waveguide components, the two ARR fringes exhibit different responses to temperature and curvature. By measuring the wavelength shift of the double-layer ARR fringe and the intensity variation of the single-layer ARR fringe, temperature and curvature can be determined simultaneously.

High coherent supercontinuum generation in nitrobenzene liquid-core photonic crystal fiber with elliptical air-hole inner ring

A nitrobenzene liquid-core photonic crystal fiber (NLC-PCF) with eight elliptical air-holes in the innermost ring of the cladding is proposed in this work, and this fiber structure can contribute to flexibly adjusting dispersion and constraining the fiber core. The appreciable dispersion is realized by adjusting the structural parameters of NLC-PCF, which is characterized by three zero-dispersion wavelengths (ZDWs), flat dispersion with the fluctuation of fewer than 40 ps nm−1 km−1, and high nonlinearity as high as 5500 W−1 km−1. The propagation of femtosecond pulse and supercontinuum generation (SCG) in NLC-PCF is studied numerically when the pump wavelength is located in the normal and abnormal dispersion region near different ZDW through solving the generalized nonlinear Schrödinger equation (GNLSE) by the split-step Fourier method. The numerical results show that a highly coherent supercontinuum (SC) spanning from 1.3 to 2.8 µm is obtained when the pump pulse with the center wavelength of 1810 nm, the peak power of 1000 W, and pulse width of 50 fs propagated in the 5 cm long NLC-PCF. This research can find applications in the fields of novel liquid-core PCF design and ultrashort pulse propagation.

Surface plasmon enhanced refractive index sensor based on tunable liquid core photonic crystal fiber covered with four gold-films

Surface plasmon enhanced refractive index sensor based on tunable liquid core photonic crystal fiber covered with four gold-films

A miniaturized and high-bandwidth polarization filter based on a plasmonic and liquid crystal offset core photonic crystal fiber

Miniaturized and broadband polarization-dependent filters with high crosstalk values are extremely desirable for practical applications in the fields of optical communications and sensing. A miniaturized photonic crystal fiber (PCF) with highly broadband polarization filtering properties is proposed in this paper. Two relatively large air holes coated with a gold film on opposite sides of the liquid crystal-filled offset core are introduced in this PCF structure to produce highly broadband polarization-dependent filtering transmissions. The impacts of the filtering properties with variable structural parameters have been studied based on the finite element method. By altering the gold film thickness (t) to be 18.7 nm and 13.8 nm, the proposed broadband polarization filter offers high resonance peaks of 2041.79 dB/cm and 2342.88 dB/cm for y-polarized mode at the wavelengths of 1.31 μm and 1.55 μm, while the corresponding loss for x-polarized one is 0.10 dB/cm and 0.83 dB/cm, respectively. Moreover, the crosstalk of the 100-μm-long PCF polarization filter with t = 18.7 nm and t = 13.8 nm is up to 177.34 dB and 203.43 dB at 1.31 μm and 1.55 μm, respectively. As the fiber length is 100 μm, the bandwidth with the crosstalk less than − 20 dB can be up to 1200 nm, from 1.2 to 2.4 μm. In addition, the proposed broadband and miniaturized PCF filter is not sensitive to the temperature variation and exhibits stable filtering characteristics with the ± 1% fabrication tolerances.

The biochemical sensor based on liquid-core photonic crystal fiber filled with gold, silver and aluminum

A highly sensitive SPR-PCF based biochemical sensor has been proposed based on finite element method simulations. Two metal wires are assumed to fill into two air holes in the y direction and the liquid analyte with refractive index higher than background material is injected into the central air hole. The liquid analyte supports liquid-core mode which couples to SPP mode as the phase matching condition is satisfied. High sensitivity of fiber sensor is achieved by the direct interaction between transmitted light and liquid analyte. The fiber sensor possesses the sensitivities of −8383.9 nm/RIU, −8428.6 nm/RIU and –8776.8 nm/RIU by filling gold, silver and aluminium respectively into the air holes of the PCF as the refractive index of liquid analyte varies from 1.454 to 1.478. The influences of the structural parameters of the PCF on the resonance wavelength and confinement loss are also analyzed.

A theoretical study on the supercontinuum generation in a novel suspended liquid core photonic crystal fiber

We theoretically propose a novel liquid filled suspended core photonic crystal fiber as a new class of microstructure optical fiber for ultrabroad supercontinuum generation. We emphasize the advantage of liquid infiltration in enhancing the fiber nonlinearity. To further enhance the nonlinearity of the liquid-infiltrated fibers, we introduce a suspended liquid core photonic crystal fiber which significantly elevates the fiber nonlinearity through reduced effective area. A comparative study on the continuum generated in conventional microstructured optical fiber (without suspension effect) and the suspended core microstructured optical fiber is performed. A broad continuum is numerically demonstrated through the suspended core fiber, which is substantially broader than the fiber without suspension effect. Thus, we propose a new means to enhance the nonlinearity beyond the intrinsic material dependence. The underlined suspended liquid core photonic crystal fiber can be a new class of fibers for next generation of broadband laser sources.

Numerical simulation and analysis of femtosecond pulse evolution in liquid-core photonic crystal fiber based on adaptive step-size methods

The adaptive step-size methods including conservation quantity error method (CQEM) and local error method (LEM) are described and used to investigate the femtosecond pulse evolution in liquid-core photonic crystal fibers. The efficiency and accuracy of the numerical results obtained from CQEM and LEM in frequency domain (FD) and time domain (TD) are compared and discussed under the fixed numerical parameters respectively. The numerical results represent that LEM has the higher accuracy due to the integration of nonlinear operator that is more efficient than CQEM. The femtosecond pulse evolution in liquid-core photonic crystal fiber is described and analyzed using LEM. Moreover, the influences of the peak power of pulse and length of liquid-core photonic crystal fibers on the supercontinuum generation are also obtained based on LEM-FD. This study is helpful optimizing the numerical process in ultra-short pulse evolution based on adaptive step-size methods.

Compact Hexagonal Liquid Core PCF Package Using a Hollow Optical Fiber

We proposed and demonstrated a novel method to package liquid-core hexagonal photonic crystal fibers (PCFs) by utilizing a hollow optical fiber (HOF) not only as a liquid delivery tube but also as a light launching pedestal. Compact all-fiber packaging with single mode fiber input and output was experimentally achieved. Various configurations of liquid core PCFs were demonstrated by controlling the inner diameter of HOF and offsets. Based on numerical analyses and light launching experiments, we confirmed that this method could substantially enhance the light–liquid interaction efficiency, structurally prevent liquid evaporation within PCF, and providing a new versatile liquid core PCF device platform.

Highly efficient compact temperature sensor using liquid infiltrated asymmetric dual elliptical core photonic crystal fiber

We propose a novel temperature sensor based on asymmetry in dual elliptical core photonic crystal fiber (DECPCF) structure featuring an enhanced sensitivity with wide detecting range over small distances. As we are interested in constructing compact temperature sensor, we put forth a novel design of asymmetric DECPCF where the core is infiltrated by chloroform. To accomplish the proposed aim, we consider the thermo-optic coefficient of chloroform and silica to anlayse the temperature dependent propagation characteristics of the proposed DEPCF. The unique property of temperature dependent effective refractive index has been exploited to tune coupling length and transmission spectrum, using finite element method. The subsequent calculation of transmission spectrum shows a temperature sensitivity of 42.99 nm/°C at 1.41 cm in the proposed asymmetric DECPCF.

Numerical simulation of surface plasmon resonance based on Au-metalized nanowires in the liquid-core photonic crystal fibers

Surface plasmon resonance sensors based on Au-metalized nanowires in the liquid-core photonic crystal fibers are theoretically analyzed by using finite element method. It is found that the negative refractive index sensitivity exists in the proposed design. The average negative refractive index sensitivity of −4125nm/RIU (Refractive Index Unit) is achieved in the sensing range of 1.45–1.49, and the sensor resolution is −4.5×10−4RIU. The sensor with high linearity and accuracy is demonstrated. The new structure is compact in size and easy to fabricate, making it promising for miniaturized complex communication devices. The effects of tuning and optimizing the structural parameters on the plasmonic excitations are also studied. This study provides a basis for investigating the PCF refractive index sensor based on the SPR of the metal nanowires.

Spontaneous four-wave mixing in liquid-core fibers: towards fibered Raman-free correlated photon sources

We experimentally demonstrate, for the first time to our knowledge, the generation of correlated photon pairs in a liquid-core photonic crystal fiber. Moreover, we show that, thanks to the specific Raman properties of liquids, the Raman noise (which is the main limitation of the performance of silica-core fiber-based correlated photon pair sources) is highly reduced. With a demonstrated coincident-to-accidental ratio equal to 63 and a pair generation efficiency of about 10−4 per pump pulse, this work contributes to the development of high-quality correlated photon pair sources for quantum communications.

Refractive index sensor based on selectively liquid infiltrated dual core photonic crystal fibers

In this paper, a novel refractive index sensor based on liquid infiltrated dual-core photonic crystal fibers (PCFs) is proposed. The two fiber cores, separated by an air hole inside the cross-section of the designed PCFs, are filled with analyte liquids which form two independent waveguides. A novel and simple refractive index sensing system is proposed using mode coupling theory and its sensing performances have been studied numerically. The results show that the refractive index sensor with 1cm length PCF has a large sensing range and high sensitivity of −65,166.10nm/RIU at wavelength 1.25μm.

Liquid core photonic crystal fiber with low-refractive-index liquids for optofluidic applications.

A defectless hexagonal air-silica photonic crystal fiber (PCF) structure with its central hole selectively filled by a low-refractive-index liquid is numerically analyzed. Despite the fact that the refractive index of the liquid is significantly lower than that of silica, we found an optimal range of waveguide parameters to ensure light guidance through the liquid core in the fundamental mode, maximizing the light-liquid interaction over a desired wavelength range. Using the vectorial finite element method (FEM), we report detailed parametric studies in terms of the effective index, chromatic dispersion, optical loss, and modal intensity distribution of the liquid core PCFs.

液芯高双折射率光子晶体光纤的特性研究

A kind of highly birefringent Photont Crystal Fiber(PCF)was proposed,a central defect elliptical hole and two other elliptical holes just below and above the central one were introduced in the core region of PCF.The central defect elliptical air hole was filled with high refractive index of liquid such as carbon disulfide.The birefringence,power confinement factor,fundament mode field and dispersion characteristic of the fiber were studied by the full-vector finite element method.The results show that the liquid-core PCF has high power confinement factor,the high negative dispersion is realized in a wavelength range from 0.6to 1.8μm,and the birefringence up to 6.8×10-2 at 1.55μm.The proposed PCF has achieved both the high birefrigence and broadband high negative dispersion characteristics,and showes good polarization stability by analyzing stucutural parameter fluctuation.

New characteristics of a resonant coupling between an analyte-filled core mode and a supermode of a liquid-core photonic crystal fiber based plasmonic sensor

A new fiber optic sensor recently proposed for sensing an analyte with a large refractive index, such as benzene, is investigated using a finite element method in order to optimize its sensitivity. The device exploits the resonant coupling between some modes in a microstructured optical fiber made by a SiO2 rod with several holes, some filled with air, some filled with a liquid analyte, and a central hollow core surrounded by a gold layer and filled with the analyte as well. The structure presents three resonant frequencies, at λ = 0.7105 μm, λ = 2.611 μm and λ = 1.094 μm, depending on the hollow core radius and the different couplings between guided and polariton modes. The first resonant coupling, at λ = 0.7105 μm, is due to a perfect phase matching condition between a mode in the analyte and a supermode; its advantages are a small value of the full width at half maximum (8.6 nm), and a high value of the signal-to-noise ratio (0.29). The second resonant coupling, at λ = 2.611 μm, is due to a loss matching condition between a supermode and a plasmon mode, and its main advantages are large spectral sensitivity and sensor resolution (1.3 × 10-6 RIU). This resonance has also some disadvantages due to a very large value of the full width at half maximum (102 nm for a symmetric line shape), and a small value of the signal-to-noise ratio (0.13). The third resonant coupling is at λ = 1.094 μm and is related again to a phase matching condition between a supermode and a plasmon mode, but for a smaller value of the radius of the central core filled with the analyte. Its advantages are a high value of the amplitude sensitivity (5741.2 RIU-1) and a better value of the sensor resolution (1.74 × 10-6 RIU). The major disadvantages of this structure are a small value of the shift (1.0 nm) towards longer wavelengths of the phase matching point for an increase of the analyte refractive index by 0.001 RIU, a small value of the signal-to-noise ratio (0.03) and a small value of the spectral sensitivity (1000 nm RIU-1).

A theoretical investigation of soliton induced supercontinuum generation in liquid core photonic crystal fiber and dual core optical fiber

The supercontinuum generation (SCG) in liquid core photonic crystal fiber (LCPCF) with versatile nonlinear response and the spectral broadening in dual core optical fiber is presented. The analysis is presented in two phase, phase I deals with the SCG in LCPCF with the effect of saturable nonlinearity and re-orientational nonlinearity. We identify and discuss the generic nature of the saturable nonlinearity and reorientational nonlinearity in the SCG, using suitable model. For the physical explanation, modulational instability and soliton fission techniques is implemented to investigate the impact of saturable nonlinear response and slow nonlinear response, respectively. It is observed that the saturable nonlinearity inevitably suppresses the MI and the subsequent SCG. On the other hand, the re-orientational nonlinearity contributes to the slow nonlinear response in addition to the conventional fast response due to the electronic contribution. The phase II features the exclusive investigation of the spectral broadening in the dual core optical fiber.

Coexistence of positive and negative refractive index sensitivity in the liquid-core photonic crystal fiber based plasmonic sensor

We present and numerically characterize a liquid-core photonic crystal fiber based plasmonic sensor. The coupling properties and sensing performance are investigated by the finite element method. It is found that not only the plasmonic mode dispersion relation but also the fundamental mode dispersion relation is rather sensitive to the analyte refractive index (RI). The positive and negative RI sensitivity coexist in the proposed design. It features a positive RI sensitivity when the increment of the SPP mode effective index is larger than that of the fundamental mode, but the sensor shows a negative RI sensitivity once the increment of the fundamental mode gets larger. A maximum negative RI sensitivity of -5500nm/RIU (Refractive Index Unit) is achieved in the sensing range of 1.50-1.53. The effects of the structural parameters on the plasmonic excitations are also studied, with a view of tuning and optimizing the resonant spectrum.

Dispersion properties of liquid-core photonic crystal fibers

Dispersion properties of liquid-core photonic crystal fibers (PCFs) with large air fraction in clads between 300 to 2000 nm have been calculated by a multipole method for various liquids including CS(2), toluene, chloroform, and water for different core diameters. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica, and a central hole is filled with liquid to create a core. The results are compared with those obtained by a fully vectorial effective index method, and fitting parameters for core sizes are found for each liquid except for water, where the latter method does not give correct dispersions at short wavelengths. Also, the power ratios inside liquid cores and effective core areas were calculated at different wavelengths.

Novel Sealing Technique for Practical Liquid-Core Photonic Crystal Fibers

In this letter, we describe a simple and effective technique to prevent evaporation in liquid-core photonic crystal fibers (PCFs). The technique consists of using a micropipette to deploy a micro-droplet of an ultraviolet curable polymer adhesive in both core inputs. After it is cured, the adhesive creates sealing polymer plugs with quite satisfactory insertion loss (overall optical transmission of about 15%). Processed fibers remained liquid-filled for at least six weeks. From a practical point of view, we conducted a supercontinuum generation experiment in a water-core PCF to demonstrate a 120-minute spectral width stability and the ability to withstand at least 3-mW average power at the sealed fiber input. Similar experiments carried out with nonsealed fibers produced supercontinuum spectra lasting no longer than 10 minutes, with average powers kept below 0.5 mW to avoid thermally induced evaporation.