Influence on photonic crystal fiber dispersion of the size of air holes in different rings within the cladding

The influence on photonic crystal fiber dispersion of the size of air holes in different rings within the cladding is investigated using a semivectorial finite difference method. Numerical results reveal that the photonic crystal fiber dispersion is more sensitive to the variation of the air hole size in the first and second rings, indicating that design of photonic crystal fibers with desirable dispersion properties requires more precise control of the parameters of the air holes in the vicinity of the fiber core.     

Broadband dispersion compensating fiber using index-guiding photonic crystal fiber with defected core

We present a novel broadband dispersion compensating photonic crystal fiber with defected core in this paper. The small central defect of air hole can flexibly control the chromatic dispersion properties of this kind of photonic crystal fiber. This kind of fiber has broadband large negative chromatic dispersion, and the chromatic dispersion coefficient varies from -440 to -480 ps/（nm.km） in the measured wavelength range of 1500 - 1625 nm. The calculated chromatic dispersion curve is well matched to the measured chromatic dispersion coefficient in the range of 1500 - 1625 nm. The proposed photonic crystal fiber can be used to design the dispersion compensating fiber in the desired wavelength range by adjusting its structural parameters.     

Broadband dispersion compensating fiber using index-guiding photonic crystal fiber with defected core

We present a novel broadband dispersion compensating photonic crystal fiber with defected core in this paper.The small central defect of air hole can flexibly control the chromatic dispersion properties of this kind of photonic crystal fiber.This kind of fiber has broadband large negative chromatic dispersion,and the chromatic dispersion coefficient varies from-440 to-480 ps/(nm·km)in the measured wavelength range of 1500-1625 nm.The calculated chromatic dispersion curve is well matched to the measured chromatic dispersion coefficient in the range of 1500-1625 nm.The proposed photonic crystal fiber can be used to design the dispersion compensating fiber in the desired wavelength range by adjusting its structural parameters.     

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 photonie crystal fibers with distinct dis- persion 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.     

Polarization properties of elliptical core non-hexagonal symmetry polymer photonic crystal fibre

In this paper, polarization properties and propagation characteristics of polymer photonic crystal fibres with elliptical core and non-hexagonal symmetry structure are investigated by using the full vectorial plane wave method. The results show that the birefringence of the fibre is induced by asymmetries of both the cladding and the core. Moreover, by adjusting the non-symmetrical ratio factor of cladding $\eta$ from 0.4 to 1 in step 0.1, we find the optimized design parameters of the fibre with high birefringence and limited polarization mode dispersion, operating in a single mode regime at an appropriate wavelength range. The range of wavelength approaches the visible and near-infrared which is consistent with the communication windows of polymer optical fibres.     

Influence on photonic crystal fiber dispersion of the size of air holes in different rings within the cladding

The influence on photonic crystal fiber dispersion of the size of air holes in different rings within thecladding is investigated using a semivectorial finite difference method.Numerical results reveal that thephotonic crystal fiber dispersion is more sensitive to the variation of the air hole size in the first and secondrings,indicating that design of photonic crystal fibers with desirable dispersion properties requires moreprecise control of the paxameters of the air holes in the vicinity of the fiber core.     

Properties of Zero Dispersion Wavelengths in Silica Strands and Photonic Crystal Fibres

To design and calculate the zero-dispersion wavelength is one of the important aspects for highly nonlinear photonic crystal fibres. By using the air filling fraction f defined as f = （ 6d） / （ 2π∧ ） here for the cladding effective index, and the step effective index model, the relationship between the properties of chromatic dispersion and the two different structures has been analysed. It is pointed that the variation of the zero dispersion wavelength is insensitive to the core diameter change in one range of core diameter D, while keeping the air filling fraction f constant. In the other range of core diameter D, the photonic crystal fibres have the best nearly-zero ultraflattened dispersion. These properties are significant to the design of chromatic dispersion and zero dispersion wavelength in photonic crystal fibres.     

Novel method for fiber chromatic dispersion measurement based on microwave photonic technique

In this letter,we propose and demonstrate a simple and novel method for fiber chromatic dispersion(CD) measurement based on microwave photonic technique.The radio frequency(RF) signal is modulated simultaneously on two light-waves with different wavelengths,and the light-wave carrying RF signals transmit through the dispersive medium under test.CD can be obtained by monitoring the power changing of the interference RF signals after photo detector.The CD values of the single-mode and dispersion compensation fibers are both measured within the wavelength range from 1 525 to 1 605 nm,which verifies the feasibility of this method.     

Characteristics of Photonic Bandgap Fibres with Hollow Core＇s Inner Surface Coated by a Layer Material

Hollow core＇s inner surface coating in a photonic bandgap fibre （PBCF） is investigated by means of finite element method. The coat material and thickness-dependence dispersion curve and group velocity dispersion are numerically studied. The coating with materials of low index or small thickness will rise up the dispersion curve but will not induce surface modes. However, coating with materials of high index or big coat thickness will induce surface modes and avoided-crossings. By varying coat material＇s refractive index and thickness, the appearances of surface modes and avoided-crossings can be changed. It is found that the avoided-crossing can enormously enlarge the negative dispersion which can find applications in dispersion compensation. We numerically achieve a negative dispersion as large as -21416.15ps/nm/km. The results give a physical insight into the propagation properties of PBGFs with the hollow core coated by a layer of material and are of crucial significance in the applications of PBGF coating.     

Fabrication of a Two-Dimensional Organic Photonic Crystal

A high-quality two-dimensional polystyrene photonic crystal is fabricated by the method of focused ion beam etching. The scanning electron microscopy (SEM) and the transmittance spectrum are used to characterize the properties of the photonic crystal. The measured transmittance spectrum is in agreement with the theoretical one. The influences of the disorders caused by the random perturbations in the diameter or the position of the air holes on the photonic band structure are analysed. It is found that the phtonic bandgap can tolerate less than 10% degree of disorder.