title: The impact of elliptical deformations for optimizing the performance of dual-core fluorine-doped photonic crystal fiber couplers.
abstract: In this paper we study the impact of elliptically-deformed features such as cladding air-holes and elliptically-modulated cores, as ingredients for optimizing the coupling characteristics of dual-core fluorine-doped photonic crystal fiber (PCF) couplers. We provide a detailed numerical investigation by using a trial and error approach for optimizing the propagation characteristics of fluorine-doped PCF couplers. Typical characteristics of the newly proposed PCF coupler structure are: wavelength-flattened coupling characteristics between 0.7 mum and 1.6 mum wavelength range, coupling efficiency of 50+/-1 % from 0.9 mum to 1.6 mum, and a reasonably small coupling length of 1.3 cm. In addition we have elaborately derived the design parameters so that our proposed dual-core PCF coupler exhibits polarization-insensitive characteristics verified by using a full-vectorial beam propagation method. The proposed dual-core PCF can be effectively used as a 3-dB coupler, over a wide wavelength range.
authors.forename: Shailendra K
authors.initials: SK
authors.lastname: Varshney
authors.forename: Nikolaos J
authors.initials: NJ
authors.lastname: Florous
authors.forename: Kunimasa
authors.initials: K
authors.lastname: Saitoh
authors.forename: Masanori
authors.initials: M
authors.lastname: Koshiba