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Full vector beam propagation method modelling of dual core photonic crystal fiber couplers

We analyse the coupling characteristics of dual-core photonic crystal fibre couplers by a 3D finite difference vector beam propagation method. Beam propagation analysis of photonic crystal fibre couplers is performed in terms of coupling length and coupling efficiency. The determination of the guiding properties such as the propagation constants is evaluated using a mode solver based on plane wave method. We study the influence of the photonic crystal fibre coupler geometrical parameters on the coupling length at different wavelengths. Variable size of the central hole is considered to improve the coupling between the two cores. It is shown that it is possible to design shorter photonic crystal fibre couplers with coupling lengths of hundred micrometers compared to conventional optical fibre couplers. We demonstrate that the designed coupler can operate as a polarization preserving directional coupler. This study confirms that this device can act as an efficient ultra small wavelength selective coupler.