Kind Of Photonic Crystal Fiber Research Articles

Highly Birefringent, Low Flattened Dispersion Photonic Crystal Fiber in the Terahertz Region

High-performance photonic crystal fiber (PCF) has an important impact on the development of the full potential of complex terahertz systems. A new kind of PCF with D-shaped air holes in core region was proposed for terahertz (THz) region. The numerical simulation results showed that the proposed PCF has a flat dispersion of 0.09 ± 0.28 ps/THz/cm at 0.8-1.2 THz. At 1 THz, an ultra-high birefringence of 0.0595, a low effective material loss (EML) of 0.0557 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , and dispersion that can be considered zero were obtained. In addition, other characteristics of the proposed PCF were strictly analyzed, such as confinement loss, bending loss, and effective mode area. The PCF is expected to be used for short distance propagation of terahertz, polarization maintaining and sensing applications of terahertz waves.

Numerical development of high performance quasi D-shape PCF-SPR biosensor: An external sensing approach employing gold

In this paper, a proper concept of a kind of photonic crystal fiber known as D-shaped PCF sensor based on SPR or Surface Plasmon Resonance phenomenon has been discussed. The analysis has been performed numerically using FEM or Finite Element Method and PML (Perfectly Matched Layer) boundary conditions. Modal analysis has been performed keeping the smallest mesh as possible. The main mechanism of the sensor is the interaction between the core guided light beam and the metal layer surface that generates free electrons. The proposed sensor shows a refractive index detection range of 1.42–1.46 RIU, with a metal thickness variation of 35 nm-45 nm and a pitch variation of 1.8 μm–2.0 μm. The sensor obtained the highest sensitivity of 15000 nm/RIU with a maximum 6.67 × 10-6 RIU resolution, using the wavelength interrogation method. Average spectral sensitivity is 8000 nm/RIU. The amplitude interrogation method found a maximum sensitivity of 230 RIU−1 with a resolution of 4.348 × 10-5 RIU. The sensor also shows high linearity fitting and Figure of Merit (FoM). For ease of design, high detection range, high wavelength and amplitude sensitivity, less fabrication complexity, high linearity and stability, the sensor can be a great competitor of the PCF sensors previously proposed.

Design a photonic crystal fiber of guiding terahertz orbital angular momentum beams in optical communication

In this letter, a hollow core ring based circular photonic crystal fiber (PCF) is explored and proposed with stably supporting terahertz (THz) orbital angular momentum (OAM) states transmission. The proposed PCF is discussed, investigated, analyzed and simulated with optical properties in a terahertz frequency spectrum ranging from 0.20 THz to 0.55 THz. The OAM and THz communication-based parameters of the fiber are deliberated extensively under various conditions through using the full vector finite element method (FEM). Some significant parameters of PCF like effective refractive index difference, dispersion profile, confinement loss, effective mode area, numerical aperture, power fraction and isolation effects are numerically discussed for the first time with their effects and applications on the THz OAM transmission. The mentioned PCF has supported 48 OAM modes with a large effective refractive index difference up to 10−3. The confinement loss of the PCF around 10−10 dB/cm, and the average dispersion profile variation is 1.0055 ps/THz/cm. Besides, the highest numerical aperture and power fraction of the PCF are 0.35 and 99.7882%, respectively. Also, a higher isolation power effect around 267 dB, and crosstalk less than −14 dB are obtained for the PCF. Moreover, this kind of PCF would be a robust candidate for efficient THz OAM transmission, high capacity and high feasibility of optical fiber communications.

Highly-birefringent and ultra-wideband low-loss photonic crystal fiber with rhombic and elliptical holes

In this paper we propose a novel type of highly-birefringent and ultra-wideband low-loss photonic crystal fiber (PCF) incorporating elliptical holes in the cladding and rhombic holes located along the transversal axes. The PCF is simulated and analyzed with finite-difference time-domain method. The properties of PCFs were investigated for various distribution, shape and size of air holes. For the optimized PCF design the birefringence reaches 8×10−3 at 1550 nm and the confinement loss is as low as 5×10−4dB/km with single mode operation in an ultra-broad transmission band (500 nm–1800 nm). Furthermore, the single mode and single polarization transmission could be achieved in this PCF at longer wavelengths beyond 1600 nm. This kind of PCF has potentials in optical long haul communication and optical fiber sensing.

Highly sensitive dual-core photonic crystal fiber based on a surface plasmon resonance sensor with a silver nano-continuous grating.

Two kinds of photonic crystal fiber (PCF) sensors based on surface plasmon resonance (SPR) with silver nano-continuous gratings (i) and (ii) are designed. The coupling characteristics and sensing properties are analyzed numerically by the finite element method (FEM). The results show that the proposed sensor based on silver nano-continuous grating (i) can achieve better performance than that of the sensors based on silver nano-continuous grating (ii) and plane silver film structures. When the segmented number is 50 and segmented angle is 0.5°, a wavelength sensitivity of the proposed sensor with silver nano-continuous grating (i) is obtained as high as 13,600 nm/RIU in the refractive index (RI) range from 1.330 to 1.365, corresponding to a maximum RI resolution of 7.35×10-6 RIU, which can have promising applications in medical and environmental monitoring and biochemical detection.

Azimuth angle orientation by side scattering for side-polishing of photonic crystal fibers

We propose and demonstrate a nondestructive and contamination-free method for azimuth angle orientation of the photonic crystal fiber (PCF) and its application for fiber side-polishing. This technique is based on the interference pattern analysis of the light forward-scattered from the PCF that is side illuminated by a laser beam. The scattering pattern is analyzed by introducing a characteristic value which is the sum over the intensities of the upper-half or lower-half regions of the scattering pattern. The characteristic value correlates closely with the azimuth angle of PCF, which enables characterizing the azimuth angle through scattering pattern analysis. Three kinds of PCFs are studied for the determination of their azimuth angles, and an angular accuracy better than 0.5° is obtained. This method is subsequently applied to orient the angular azimuth in side-polishing of the PCF, and the accuracy of polishing angle is about 0.5°. This technique is nondestructive, contamination-free, easy to implement, and able to serve for in-line angular orientation during the fabrication of PCF-based optical devices and manipulation of the PCF.

Seven-core photonic liquid crystal fibers for simultaneous mode shaping and temperature sensing

Through doping liquid crystals into the core region, we propose a kind of seven-core photonic crystal fiber (PCF) which can achieve mode shaping and temperature sensing simultaneously in the communication window of 1.1–1.7 μm. To the best of our knowledge, this is the first time that the function of seven-core PCFs as temperature sensors is investigated. By using the full vectorial finite element method, the characteristics of the fiber with the temperature, such as the effective mode area, the waveguide dispersion, and the confinement loss, are analyzed. This kind of PCF can be competitive in providing temperature sensing in multi-core PCF lasers.

Characteristics analysis of photonic crystal fiber with octagonal hybrid cladding

Aiming at the requirements of high birefringence and double zero dispersion points in optical sensing and optical communication, a new kind of photonic crystal fiber (PCF) with hybrid structure is proposed, of which the cladding is arrayed in octagonal and squarely cladding. Birefringence, dispersion and nonlinear coefficient of the proposed PCF are analyzed by using Finite Element Method (FEM). Analysis shows that the birefringence of proposed PCF can reach the magnitude of 10−3 after optimization, which will fulfill the requirement of high birefringence. In addition, the proposed PCF also has double zero dispersion points when wavelength range from 0.8μm to 2μm. This feature will be helpful for the designing of dispersion compensation PCF.

Evaluation of optical properties for real photonic crystal fiber based on total variation in wavelet domain

Abstract An evaluation method based on the total variation model (TV) in wavelet domain is proposed for modeling optical properties of real photonic crystal fibers (PCFs). The TV model in wavelet domain is set up to suppress the noise of the original image effectively and rebuild the cross section images of real PCFs with high accuracy. The optical properties of three PCFs are evaluated, including two kinds of PCFs that supplied from the Crystal Fiber A/S and a homemade side-leakage PCF, by using the combination of the proposed model and finite element method. Numerical results demonstrate that the proposed method can obtain high noise suppression ratio and effectively reduce the noise of cross section images of PCFs, which leads to an accurate evaluation of optical properties of real PCFs. To the best of our knowledge, it is the first time to denoise the cross section images of PCFs with the TV model in the wavelet domain.

Tunable microwave generation method based on birefringence photonic crystal fiber

A new method is proposed to generate tunable microwave by using single-light source and birefringence photonic crystal fiber (PCF), which is based on the interaction and the coupling between the two polarizations of the initial Gaussian optical pulse in PCF. A full vector finite element is used to design a high birefringence PCF. The expressions of the microwave are derived by couple-mode theory. The proof of concept device consists of a light source, a birefringence PCF, a polarizer controller and a photodetector. The frequency of the generated pulses can be controlled by adjusting the parameters of the optical fiber system. The simulation results demonstrate the system can generate the frequency of microwave are 8.03–37.67GHz and 26.82–125.5GHz from two kinds of PCFs, respectively. The system is elastic, stable, brief and highly efficient.

100-W 430-ps all-fiber picosecond laser by using 10-/130-μm ytterbium-doped double-clad fiber and its application in SCS

We report on a theoretical and experimental study on 100-W picosecond pulsed laser produced in 10-μm-core double-clad fiber. Firstly, we make a theoretical simulation based on four-level rate equation and nonlinear Schrodinger equation. In the theoretical simulation, we prove that 100-W picosecond laser can be produced in 10-μm-core doped fiber and find that the length of the doped fiber has a great impact on the spectrum characteristics of the output laser pulse. Then, based on the theoretical analysis results, we make an experimental study introducing Master Oscillator Power Amplifier technology. We do four sets of comparative experiments using different lengths of the doped fiber: 6, 6.5, 7 and 8 m. As a result, 100 W of average output power is obtained in 10-μm fiber core with 6.5 m length. Its repetition rate is 22.7 MHz, its central wavelength is 1,040 nm, and its pulse width is about 430 ps. Moreover, we use the picosecond laser source to pump the nonlinear photonic crystal fiber (PCF) to produce super-continuum source. With two different kinds of PCF, 30 and 36 W average output power are obtained corresponding to spectral broadening range from 550 to 1,650 nm and from 500 to 1,650 nm, respectively.

Temperature sensibility of the birefringence properties in side-hole photonic crystal fiber filled with Indium

We report on the temperature sensitivity of the birefringence properties of a special kind of photonic crystal fiber containing two side holes filled with Indium metal. The modulation of the fiber birefringence is accomplished through the stress field induced by the expansion of the metal. Although the fiber was made at low gas pressures during the indium infiltration process, the birefringence showed anomalous property at a relatively low temperature value, which is completely different from those reported in conventional-like fibers with two holes filled with metal. By modeling the anisotropic changes induced by the metal expansion to the refractive index within the fiber, we are able to reproduce the experimental results. Our results have practical relevance for the design of devices based on this technology.

Designing of a polarization beam splitter for the wavelength of 1310 nm on dual-core photonic crystal fiber with high birefringence and double-zero dispersion

We have proposed a novel kind of photonic crystal fiber which contains two asymmetric cores. The birefringence and the dispersion are numerically analyzed based on finite element method when the size of the air holes and the pitch of two adjacent air holes are changed. It is shown that the proposed photonic crystal fiber has high birefringence up to the order of 10−2 and double-zero dispersion points are at the wavelengths of 1310 nm and 800 nm, simultaneously. At the same time, the normalized power and the extinction ratios of the proposed photonic crystal fiber have been simulated. It is demonstrated that, at the wavelength of 1310 nm, the x-polarized mode and the y-polarized mode are separated when the propagation distance is 2.481 mm.

Analysis of high birefringence photonic crystal fiber with octagonal and squarely lattice

Aiming at the requirement of high birefringence, a new kind of photonic crystal fiber (PCF) with octagonal and squarely lattice is proposed. In this structure, squarely lattices are added in the inner layer to obtain high birefringence. Birefringence and dispersion as a function of wavelength and size of PCF are analyzed by using Finite Element Method (FEM). Simulation results show that this kind of PCF exhibits high birefringence with a magnitude of 10−3, and one zero dispersion point is obtained simultaneously. In addition, the characteristics of PCF can be tuned by changing the size of fiber.

Different supercontinuum generation processes in photonic crystal fibers pumped with a 1064-nm picosecond pulse

Picosecond pulse pumped supercontinuum generation in photonic crystal fiber is investigated by performing a series of comparative experiments. The main purpose is to investigate the supercontinuum generation processes excited by a given pump source through the experimental study of some specific fibers. A 20-W all-fiber picosecond master oscillator-power amplifier (MOPA) laser is used to pump three different kinds of photonic crystal fibers for supercontinuum generation. Three diverse supercontinuum formation processes are observed to correspond to photonic crystal fibers with distinct dispersion properties. The experimental results are consistent with the relevant theoretical results. Based on the above analyses, a watt-level broadband white light supercontinuum source spanning from 500 nm to beyond 1700 nm is demonstrated by using a picosecond fiber laser in combination with the matched photonic crystal fiber. The limitation of the group velocity matching curve of the photonic crystal fiber is also discussed in the paper.

Numerical analysis of a photonic crystal fiber based on two polarized modes for biosensing applications

This paper presents a theoretical study on a photonic crystal fiber plasmonic refractive index biosensor. The proposed photonic crystal fiber sensor introduces the concept of simultaneous detection with the linearly polarized and radially polarized modes because the sensing performance of the sensor based on both modes is relatively high, which will be useful for selecting the modes to make the detection accurately. The sharp single resonant peaks of the linearly polarized mode and radially polarized mode, are stronger and more sensitive to the variation of analyte refractive index than that of any other polarized mode in this kind of photonic crystal fiber. For linearly polarized mode and radially polarized mode, the maximum sensitivities of 10448.5 nm per refractive index unit and 8230.7 nm per refractive index unit can be obtained, as well as 949.8 and 791.4 for figure of merits in the sensing range of 1.33–1.45, respectively. Compared with the conventional Au-metalized surface plasmon resonance sensors, our device is better and can be applied as a biosensor.

Numerical analysis of photonic crystal fiber with chalcogenide core tellurite cladding composite microstructure

Kinds of photonic crystal fibers with chalcogenide core tellurite cladding composite microstructure are proposed. The multi-core photonic crystal fiber can reach the higher nonlinearity coefficient and the larger effective mode area. The small single-core photonic crystal fiber has a very high nonlinearity coefficient. At the wavelength λ = 0.8 μm, the nonlinearity coefficient can reach 31.37053 W−1·m−1, at the wavelength λ = 1.55 μm, the nonlinearity coefficient is 11.19686 W−1·m−1.

Characteristics of photonic crystal fibers designed with an annular core using a single material

We propose a kind of photonic crystal fiber (PCF) designed with an annular core and fabricated using a single material. Characteristics of such fibers, including the mode field distributions of both the core and cladding modes, the effective mode area of the fundamental core mode, and the dispersion profile, are investigated using the finite element method. The coupling between the fundamental mode and an excited core mode or cladding mode is discussed in order to apply the proposed design in mode-coupling devices. Results show that such a PCF may be suitable for both optical communications and optical sensing technologies.

Generation of hollow beam from photonic crystal fiber with an azimuthally polarized mode

A kind of photonic crystal fiber (PCF) with an azimuthally polarized (TE01) mode is proposed to generate hollow beam (HB). The finite element method (FEM) is employed to study the polarization properties of the fiber and normalized intensity of the HB. Simulation results show that the TE01 mode with a low confinement loss in this kind of fiber can provide a high quality HB. By varying arrangement of air holes in the cladding region or changing structure parameters of the PCF, HB of different sizes can be obtained. The smallest dark spot size (DSS) and the narrowest width of HB achieved are about 1μm and 1.4μm at a wavelength of 1.55μm, respectively. This kind of PCF, which can generate HB with an azimuthally polarized mode, has great significance in the technique of optical tweezers.

Theoretical research on the generation of coherent supercontinuum

The degree of coherence of the supercontinuum(SC) directly determine the resolution and the precision in many optical apparatus, so how to achieve highly coherent SC is one of the focuses in nonlinear optics. It is shown that modulation instability (MI) is the key element that influences the coherence of SC. Therefore an effective way of achieving coherent SC is to avoid MI and to use other nonlinear effects such as self-phase modulation (SPM). We design a kind of photonic crystal fiber (PCF) which has an all-normal group velocity dispersion (GVD) profile. After numerical investigation on the generation of SC in the PCF we obtain the degrees of the SC in different lengths. Results indicate that for the generated SC by pumping 50 cm of this PCF with TFWHM=400 fs unchirped pulse Gaussian pulse can realize high coherence in the entire broadening area on condition that relative power is larger than -80 dB.