Photonic Crystal Fiber
Supercontinuum Generation
Applications

Overview•

Photonic crystal fiber (PCF) provides a unique platform for realizing
the desired dispersion, birefringence, confinement, and mode
multiplicity characteristics for myriad of applications. This can beattributed to the freedom in designing the shape, size andarrangement of holes and material composition of the PCF. Using thevector finite element method (VFEM) mode solver in OptiMode,modal analysis of arbitrary PCF designs can be performed, and thelinear/nonlinear fiber model characteristics can be extracted. The
parameters of the PCF can be used in OptiSystem to simulate theevolution of signals and to asses system performance.

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Supercontinuum generation, pulse compression,solitons, etc.
Bio-chemical and environmental sensing
High-power beam delivery
Extreme zero-dispersion wavelengths, dispersion
flattened fibers, etc.
Polarization maintaining and single-mode application
Nonlinear processing
Lasers and amplifiers
Dispersion compensation

OptiMode Software Features

Simulation Description••

A solid-core silica PCF used for supercontinuum generation [1,2] isconsidered. Fig. 1 shows the fiber structure with the air-holes(diameter=1.3μm) arranged in the triangular lattice (pitch=1.7μm).
Imposing the symmetric electric/magnetic boundary conditions along
the X/Y axes in OptiMode reduces the simulation domain by a factorof 4. The triangular mesh is adapted to have finer resolution in thecore in order to accurately approximate air-hole boundaries.

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VFEM mode solver is extraordinarily fast
Triangular mesh can be adapted to accurately
approximate the fine features of the geometry,refractive index profile and the electromagnetic fieldsBuilt-in VB scripting capabilities accelerate the designand optimization of complex waveguide profiles
Exploiting the symmetric boundary conditions
reduces the simulation domain, and modes of certain
symmetry can be readily targeted
Supports lossy, dispersive, and anisotropic materials
in full-vector formulation
Uniaxial perfectly matched layer (UPML) allows
modeling leaky modes

OptiSystem Software Features•••••

Rapid prototyping of complex optical systems using
extensive libraries of optical components
Comprehensive libraries of linear and nonlinear
propagation models
Broad temporal and spectral visualization capabilities
for signals along the optical systems
Co-simulation with external software packages such
as Matlab, Python, Scilab, and C++
Compatible with other Optiwave software products
such as OptiSPICE, OptiGrating and OptiBPM
Figure 1: Schematic of the PCF (inset) and the actual simulation window with theFEM mesh superimposed.

Employing the modal analysis by the VFEM solver inOptiMode, the obtained fiber model parameters are listed
in Table 1. The effective area, group velocity dispersion(GVD) and the 3rd order dispersion (TOD) can becalculated from the field profile of the fundamental modeat the pump wavelength (depicted in Fig. 2). The
dispersion and effective modal index are shown in Fig. 3.
The dispersion and the zero-dispersion wavelength(780nm) match the values reported in references [1,2].
Assuming typical values for the nonlinear refractive indexof silica (n2=3.5x10-20 m2W-1) and fractional Raman
contribution to the nonlinear polarization (fR=0.18), a
supercontinuum can be generated from a 50fs input sechpulse with 10kW peak power in OptiSystem software. The
temporal and spectral evolution of the pulse is shown inFig. 4. Self-phase modulation, intra-pulse Raman
scattering and self-steepening effects are considered in
the nonlinear fiber model implemented in OptiSystem.

(a)

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Another example related to the perturbation of an ideal
soliton pulse by higher order dispersion and Raman
scattering in the PCF is simulated in OptiSystem. A 20fs
fundamental soliton pulse at 835nm with 837.56W peak
power is considered. A comparison of the spectral andtemporal shapes of the ideal case (balanced self-phasemodulation and GVD induced broadening) and theperturbed case after 1m of propagation in the PCF isshown in Fig. 5.

(a)(b)(c)Figure 4: OptiSystem simulation results of the Evolution of a 50fs (FWHM) soliton
pulse with 10KW peak power at 835nm wavelength after propagating different
distances along the PCF: (a) temporal (b) spectral (50dB offset between the curves).
Table 1: PCF characteristics at λ=835nm obtained from OptiMode and used tosimulate nonlinear pulse propagation in OptiSystem.

Figure 2: Electric-field amplitude profile (a) |Ex|, (b) |Ey| and (c) power
density (Poynting vector) of the X-polarized fundamental mode of thePCF at 835nm wavelength.

Figure 3: Modal effective index and dispersion parameter of thefundamental mode of the PCF calculated in OptiMode.

Group velocity dispersion (β2)
Third order dispersion (β3)
Modal effective area (Aeff)-11.46 ps2km-1
8.10x10-2 ps3km-1
2.41 μm2

Figure 5: OptiSystem simulation of a 20fs soliton pulse at 835nm with peak-powerof 837.56W after propagating 1m in the PCF.

References[1] J. Ranka et al., "Visible continuum generation in air–silica microstructure opticalfibers with anomalous dispersion at 800 nm," Opt. Lett. 25, 25 (2000).
[2] J. M. Dudley et al., “Supercontinuum generation in photonic crystal fiber” Rev.
Mod. Phys. 78, 1135 (2006)