Corresponding author: Feroza Begum ( feroza.begum@ubd.edu.bn ) © 2018 Feroza Begum, Hazwani Suhaimi, Norazanita Shamsuddin, Martin Geoffrey Blundell, Yoshinori Namihira.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Begum F, Suhaimi H, Shamsuddin N, Blundell MG, Namihira Y (2018) Supercontinuum generated high power highly nonlinear photonic crystal fiber for medical and optical communications applications. Modern Electronic Materials 4(2): 5358. https://doi.org/10.3897/j.moem.4.2.33839

This paper investigates a supercontinuum generated high power highly nonlinear photonic crystal fiber for medical and optical communication applications. The full vector finite difference method with perfectly matched layer is used as an analysis tool. Numerical simulation results show that it is possible to achieve high nonlinear coefficient, near zero ultraflattened dispersion, low confinement loss and supercontinuum spectrum with high power. Moreover, numerical results show that short length of the proposed photonic crystal fiber is achieved. The numerical simulation results of supercontinuum generation is conducted by solving the generalized nonlinear Schrödinger equation with the splitstep Fourier method. It is observed adequate supercontinuum spectrum that broaden from 960 to 1870 nm by considering center wavelengths of 1.06, 1.31, and 1.55 μm into silica based index guiding photonic crystal fiber. This simulation results prove that the proposed design of a highly nonlinear photonic crystal fiber is a great solution for broad supercontinuum generation with high power.
photonic crystal fiber, nonlinear coefficient, confinement loss, supercontinuum spectruum
Photonic crystal fibers (PCFs) have attracted a lot of interest of researchers because of their many unique properties which are not found in conventional optical fibers [
To date, different supercontinuum generated highly nonlinear photonic crystal fibers (HNPCFs) have been suggested for optical communications and medical applications [
In this paper, picosecond pulse based SC generated high power HNPCF structure with near zero ultraflattened dispersion, low confinement loss are proposed for the medical and optical communication applications. Numerical simulation results show that the proposed sevenring HNPCF having high nonlinear coefficients of about 106 W^{1}km^{1} at center wavelength 1.06 μm, 74 W^{1}km^{1} at center wavelength 1.30 μm and 53 W^{1}km^{1} at center wavelength 1.55 μm. Moreover, it has been found that the proposed SC generated HNPCF can exhibits very low confinement loss of less than 10^{6} dB/km in the 1.0 to 1.60 μm wavelength range and near zero ultraflattened chromatic dispersion in the targeted wavelength range. Furthermore, a high input power SC spectrum was obtained at center wavelengths 1.06, 1.30 and 1.55 μm. Additionally, it is also represent the fiber length of 1.0 m in all of the center wavelength for the proposed HNPCF.
A simulation tool using finite difference method with anisotropic perfectly matched layer boundary condition for designing and simulating proposed HNPCF [
L _{C} = 8.686k_{0}Im(n_{eff}) (3)
where λ is the wavelength, n_{eff} is the complex refractive index, Re(n_{eff}) is the real part of the complex refractive index, Im(n_{eff}) is the imaginary part of the complex refractive index, k_{0} is the free space wave number, E_{a}(r) is the field amplitude at radius r.
Sellmeier equation is an empirical relationship between refractive index and wavelength for particular transparent and nontransparent medium. This equation is used to determine the dispersion of light. So the equation is define as
where B_{1,2,3} and C_{1,2,3} are coefficients. The coefficients and values of Sellmeier equations are shown in Table
Coefficients and values of Sellmeier equation.
Coefficient  Value 

B _{1}  0.6961663 
B _{2}  0.4079426 
B _{3}  0.8974794 
C _{1}  0.0684043 · 10^{6} 
C _{2}  0.1162414 · 10^{6} 
C _{3}  9.896161 · 10^{6} 
Since PCFs can confine high intensity light, it is expected that PCFs would have high nonlinearity. Nonlinear coefficient γ can be calculated [
Where n_{2} is the nonlinear refractive index.
Fig.
Figures
Figures
Figure
Figures
Spectrum intensity of the proposed SC generated high power HNPCF at the center wavelengths (a) 1.06 μm, (b) 1.30 μm and (c) 1.55 μm.
Fiber parameters.
Parameters  λ _{c}=1.06 [μm]  λ _{c}=1.30 [μm]  λ _{c}=1.55 [μm] 

β_{2} [ps^{2}/km]  1.013  1.524  2.166 
β_{3} [ps^{3}/km  0.014  0.004  0.013 
P_{in} [kW]  2.9  4.1  5.5 
L _{F} [m]  1.0  1.0  1.0 
In this research, a supercontinuum generated high power HNPCF with seven rings of air hole was investigated. High nonlinear coefficients of 106 [Wkm]^{−1}, 74 [Wkm]^{−1} and 53 [Wkm]^{−1} with ultraflattened chromatic dispersion of ±8.5 ps/(nm.km) in a wavelength range of 1.0 µm to 1.60 μm and low confinement loss of less than 10^{6} dB/km in expected wavelength range was achieved. Moreover, it has been observed that this proposed SC generated high power HNPCF could generate broad SC spectrum, and high powers of 2.9 kW, 4.1 kW and 5.5 kW at center wavelengths 1.06 μm, 1.30 μm and 1.55 μm, respectively were achieved. The proposed SC generated high power HNPCF may be suitable for optical communications, optical parametric amplification, alloptical signal processing and supercontinum spectrum generation.