Minimize the Losses of hollow core photonic crystal fibres (HCPCF) through accurate finite element simulations.

Fig. 1: Geometry of a Hollow Core Photonic Crystal Fiber (yellow: glass, magenta: air). The hollow core has a size of 19 unit cells of the periodic cladding.

Photonic crystal fibers, a new class of optical fibers, have impressive optical guiding and confinement properties not accessible to classical fibers. The microstructured cross-sections of these devices can be manufactured at high precision by drawing a structured and heated preform to very small diameters.

Figure 1 shows the geometry of a typical cross section of a photonic crystal fibre with a hollow (i.e., air-filled) core. Light of high intensity can be guided with low losses over relatively large distances. Figure 2 shows a triangular discretization of the geometry (obtained with JCMgeo). Note the accurate geometrical resolution of, e.g., corner roundings and strut widths.

Fig. 2: Detail of an automatically generated mesh for a HCPCF.


Fig. 3: Band structure of the cladding of the microstructured fiber.

Computing the cladding band structures (see Fig. 3) allows, e.g., to optimize the cladding structure for good light confinement in specific wavelength ranges.

Fig. 4: Intensity distribution of a guided mode in a not optimized fiber geometry.

 Figure 4 shows the intensity distribution of a guided mode in a not optimized fiber geometry. For achieving optimum guiding properties, several parameters of the geometrical layout, like e.g. cladding periodicity, strut thickness, or the shape of the central hole have to be optimized. Figure 5 shows the dependence of the field confinement in the central core on a specific structural parameter.

Fig. 5: Optimize the performance of a HCPCF: Dependence of the field confinement on a structural parameter.

Fig. 6: Well confined fiber mode ensures low losses.

Figure 6 shows the field distribution of a guided mode in an optimized fiber geometry. High accuracy and fast computations are extremely helpful in the optimization of such structural parameters. Figure 7 shows the same mode computed on a quarter of the cross section of the (symmetric) fiber as computational domain. The use of symmetries allows to further decrease the computational effort of PCF computations.

Fig. 7: Well confined intensity distribution of a guided mode in an optimized hollow core photonic fiber.


 P.J. Roberts - Numerical methods for the design and analysis of photonic crystal fibres - In this article, P.J. Roberts highlights JCMwave's FEM solvers and states that "These codes are appropriate for finding the linear mode properties of all types of PCF. It is likely to be very difficult for a small university team to improve upon them without spending many man-years in code development. The availability of such codes enables the researcher to concentrate on other aspects of the electromagnetic propagation within PCF."

Finite element simulation of radiation losses in photonic crystal fibers - Paper with details on typical accuracies and computation times achievable with our solvers. (See also preprint at the preprint server.)