Ultrahigh negative dispersion compensating Hexagonal photonic crystal fiber with large nonlinearity

Abstract

Photonic crystal fibers (PCFs) are microstructure optical fibers which demonstrate unique optical properties by exploiting the guiding mechanism of electromagnetic waves through the periodic formation of refractive indices. PCF with high negative dispersion and enhanced nonlinearity is often desirable for improving the signal quality in long-haul light-wave communication and different nonlinear optical applications. Investigations have been carried out previously on dispersion and nonlinearity for several numerical designs of PCF through the variation of structural parameters. However, the designs of photonic fibers, which are comprised of noncircular air holes, are difficult and challenging to fabricate with existing technologies. In this work, an analytical design of hexagonal photonic crystal fiber (H-PCF), which consists of all circular air holes is proposed. The primary aim of the proposed numerical design is to attain desired optical characteristics by using circular air holes only to make the fiber simple and feasible for standard fabrication process. The proposed H-PCF consists of a regular hexagonal lattice structure, where the size and location of the few air holes are changed in order to obtain high optical dispersion and enhanced nonlinearity. The corresponding modal properties resulting from geometrical modification and the optimal values of the geometrical parameters are investigated using the numerical electromagnetic solver based on finite element method (FEM). The numerical results show that our proposed H-PCF achieves a large dispersion of −2304 ps/(nm. km) and nonlinearity of 110.8 W−1km−1 at the operating wavelength of 1.55 µm. The proposed structure offers design flexibility since only circular air holes are involved in the design. Our proposed H-PCF structure can be considered a prospective candidate for dispersion compensation in long-haul optical communication and several other applications such as optical modulation and amplification.