Fluid-filled Photonic Crystal Fiber Research Articles

A Magnetic Field Sensor Based on Directional Coupling in a Magnetic Fluid-Filled Photonic Crystal Fiber.

In this paper, a dual-core photonic crystal fiber (DC-PCF) sensitivity sensor filled with magnetic liquid is introduced and investigated with the finite element method (FEM). To regulate the energy coupling involving the two cores, the magnetic fluid is filled into the pore between the two cores. To adjust the coupling between the supermodes in the DC-PCF, the refractive index (RI) of the air hole filled magnetic fluid may change due to the external magnetic field. This specifically created a magnetic fluid-filled DC-PCF; the magnetic fluid-filled hole is not used as the core for energy transmission, thus avoiding transmission loss. The dip wavelength and the magnetic field displayed an excellent linear connection between 80 and 260 Oe, depending on the numerical data. The detection sensitivity of the magnetic field reached 515.75 pm/Oe at a short fiber length of 482 µm. The designed magnetic fluid-filled DC-PCF has high sensitivity and small volume and has great application prospects in magnetic field detection in the medical and industrial fields.

Magneto and Electro-Optic Intensity Modulator Based on Liquid Crystal and Magnetic Fluid Filled Photonic Crystal Fiber**Supported by the Joint Research Fund in Astronomy under Cooperative Agreement between the National Natural Science Foundation of China and Chinese Academy of Sciences under Grant No U1531102, the Fundamental Research Funds for the Central Universities under Grant No HEUCF181116, and the National Natural Science

We propose a novel light intensity modulator based on magnetic fluid and liquid crystal (LC) filled photonic crystal fibers (PCFs). The influences of electric and magnetic fields on the transmission intensity are theoretically and experimentally analyzed and investigated. Both the electric and magnetic fields can manipulate the molecular arrangement of LC to array a certain angle without changing the refractive index of the LC. Therefore, light loss in the PCF varies with the electric and magnetic fields whereas the peak wavelengths remain constant. The experimental results show that the transmission intensity decreases with the increase of the electric and magnetic fields. The cut-off electric field is 0.899 V/μm at 20 Hz and the cut-off magnetic field is 195 mT. This simple and compacted optical modulator will have a great prospect in sensing applications.

Multi-modes interferometer for magnetic field and temperature measurement using Photonic crystal fiber filled with magnetic fluid

Abstract An in-line modal Mach–Zehnder interferometer (MZI) based on a magnetic fluid-filled photonic crystal fiber (PCF) was proposed in this paper. The Mach–Zehnder interference was induced by the single mode fiber (SMF)-photonic crystal fiber (PCF)-single mode fiber (SMF) structure. And the photonic crystal fiber was filled with magnetic fluid to measure the magnetic field and temperature. There are multiple cladding modes are involved into the interference. Hence simultaneous measurement of temperature and refractive index can be achieved by simultaneously monitoring the two different modes interference spectra. The sensitivities of magnetic field and temperature can reach up to 0.072 nm/Gs and −0.080 nm/°C, respectively.

Multi-component-intermodal-interference mechanism and characteristics of a long period grating assistant fluid-filled photonic crystal fiber interferometer

A compact in-line modal interferometer based on a long period grating (LPG) inscribed in water-filled photonic crystal fiber (PCF) is proposed and demonstrated. The interferometer works from the interference between fundamental core mode and different vector components of LP(11) core mode. The LPG is especially inscribed to realize the energy exchange between the fundamental core mode and different vector components of LP(11) core mode in the PCF. We build a complete theoretical model and systematically analyze the multi-component-intermodal-interference mechanism of the interferometer based on coupled-mode theory. Due to the asymmetric index distribution over the cross section of the PCF caused by CO(2)-laser side illumination, the dispersion curves and temperature sensitivities referring to different vector components of LP(11) core mode are quite different. Thus the interferometer is polarization-dependent and the adjacent interference fringes according to different components of LP(11) mode show greatly discrimination in sensitivities of temperature and strain, making it a good candidate for multiple physics parameters measurements.

All-fiber magnetic field sensors based on magnetic fluid-filled photonic crystal fibers

A method for measurement of a magnetic field by combining photonic crystal fibers (PCFs) and magnetic fluid is presented and experimentally demonstrated. The magnetic fluid is filled into the air holes of the cladding layer in the PCF. Due to the tunable refractive index property of the magnetic fluid, the refractive index difference between the fiber core and cladding layer is changed with the external magnetic field. The magnetic field can be directly detected by measuring the intensity of the transmission light. A series of magnetic fields with different strengths have been measured with the sensor. The experimental results show that a resolution of up to 0.09 Oe is achieved, and a good repetition is demonstrated experimentally. Compared with other expensive methods, the proposed method possesses high sensitivity and low cost.

Tunable thermo-optic switch based on fluid-filled photonic crystal fibers

A tunable thermo-optic intensity-modulated switch is investigated theoretically and numerically. It is based on the infiltration of temperature-sensitive mixture liquids into index-guiding photonic crystal fibers (PCFs). The switching function attributes to the thermo-optic effect of the effective refractive index of the cladding. The simulation illustrates that the switch presents a tunable transition point according to the concentration of the mixture liquids, and the on-off switching functionality can be realized within a narrow temperature range of 2 °C. The switches have wide application for innovative all-in-fiber optical communication and logic devices.

Simultaneous temperature and force measurement using Fabry-Perot interferometer and bandgap effect of a fluid-filled photonic crystal fiber

A novel fiber sensor capable of simultaneously measuring force and temperature is proposed and investigated. A section of high-index-fluid-filled photonic bandgap fiber (HIFF-PBGF) is inserted in a fiber loop to act as the sensing head. Photonic bandgap effect of the HIFF-PBGF as well as Fabry-Perot interferometer (FPI) introduced by controlling the splicing between the HIFF-PBGF and single mode fiber is used for achieving force and temperature discrimination. Taking advantage of the bandgap being high sensitivity to the temperature, a high temperature sensitivity of more than -1.94 dB/°C is achieved, which is the highest based on the intensity measurement, to our best knowledge. Meanwhile, a force sensitivity of 3.25 nm/N (~3.9 pm/με) is obtained, which could be enhanced by controlling the FPI shape. The device also has the strong points of easy fabrication, compact structure and high interference fringe contrast.

Improved bending property of half-filled photonic crystal fiber

A half-filling technique was demonstrated to improve the bending properties of a fluid-filled photonic crystal fiber. Such a technique can realize to fill selectively a fluid into half of air holes in a PCF. The bending properties of the half-filled PCF are quite different from those of the fully-filled PCF. Distinct bending properties were observed when the half-filled PCF was bent toward different fiber orientations. Especially, the transmission spectrum of the half-filled PCF was hardly affected while the fiber was bent toward the filled-hole orientation.

Temperature-controlled transformation in fiber types of fluid-filled photonic crystal fibers and applications

We investigated experimentally and theoretically an invertible fiber-type transformation from a photonic bandgap fiber into a nonideal waveguide and then into an index-guiding photonic crystal fiber via the thermo-optic effect of the fluid filled in the air holes. Such a transformation could be used to develop an in-fiber optical switch/attenuator with a high-extinction ratio of more than 35 dB over an extremely broad wavelength range from 600 to 1700 nm via a small temperature adjustment.

Optical switch based on a fluid-filled photonic crystal fiber Bragg grating

We report the implementation of an in-fiber optical switch by means of filling a fluid into the air holes of a photonic crystal fiber with a fiber Bragg grating. Such a switch can turn on/off light transmission with an extinction ratio of up to 33 dB within a narrow wavelength range (Bragg wavelength) via a small temperature adjustment of +/-5 degrees C. The switching function is based on the temperature-dependent coupling between the fundamental core mode and the rod modes in the fluid-filled holes resulting from the thermo-optic effect of the filled fluid.