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.
Highlights
Over the last decade, an exponential growth has been observed in theoretical and practical implementation of photonic crystal fibers (PCFs), due to their remarkable properties such as, wide-band single mode operation [1], large effective mode area, high nonlinearities, and overall controlled dispersion properties [2]
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 fluorinedoped 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
Summary
An exponential growth has been observed in theoretical and practical implementation of photonic crystal fibers (PCFs), due to their remarkable properties such as, wide-band single mode operation [1], large effective mode area, high nonlinearities, and overall controlled dispersion properties [2]. At short wavelengths the modal field remains confined into the silica core region and as the wavelength of light increases, the field penetrates to the air-hole cladding and lowers the effective refractive index of the cladding. This unusual interaction of light with air-holes causes unique properties which are not possible to be observed using conventional optical fiber technology. Polarization-independent PCF wavelength splitters have been proposed recently [10], based on the inclusion of elliptical air-holes in the cladding of the fiber In all these reports the central problem was the design of dual-core PCF couplers that can operate at one or two distinct wavelengths.
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