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A highly birefringent polarization-maintaining dual-core photonic crystal fiber (DC-PCF) structure with elliptical air holes around the cores has been designed for possible supercontinuum generation over two octaves spanning a spectral bandwidth in the 400- to 1800-nm wavelength range. The supercontinuum (SC) spectrum covers the near-UV, visual, and near-infrared regions of electromagnetic spectra when a hyperbolic secant pulse of 50 fs duration, 322 mW average power, and 80 MHz repetition rate corresponding to 4.03 nJ energy is launched into the DC-PCF around a 1060-nm pumping wavelength. The generated SC spectrum satisfies the necessary requirements for applications in biophotonics, telecommunications, and frequency metrology.

The concept of employing a central air hole in the core is exploited to obtain an ultralarge negative dispersion photonic crystal fiber (PCF) over the wavelength range of 1350 to 1650 nm. The results show that the fiber may exhibit an average dispersion well over −500 ps/nm-km with a flattened dispersion profile. It is also found that the fiber shows a high birefringence in the order of 10−2 over the entire wavelength bands of interest. The endlessly single-mode behavior of PCFs is utilized to ensure the single modedness of the proposed fiber. Also, the technique of liquid crystal infiltration is exploited to suppress one of the two orthogonal modes of the fundamental mode. Along with the single-polarization behavior, the fiber shows an even more negative dispersion profile with less dispersion variation.

The leakage losses of a bent equiangular spiral photonic crystal fiber (ES-PCF) have been analyzed in this paper by employing a full-vectorial finite element method. The analysis shows that the confinement and bending losses of ES-PCF are several orders of magnitude less than that of the conventional hexagonal lattice PCF (H-PCF) with similar dimensions. Also, the bending loss increases less rapidly in ES-PCF than in H-PCF for similar bending radii. It has also been found that no mode degeneration between fundamental core mode and first cladding mode occurs in ES-PCF. The reason of higher field confinement in ES-PCF than its hexagonal counterpart is also discussed.

A novel photonic crystal fiber (PCF) having circular arrangement of cladding air holes has been designed and numerically optimized to obtain a bend insensitive single mode fiber with large mode area for both wavelength division multiplexing (WDM) communication and fiber-to-the-home (FTTH) application. The bending loss of the proposed bent PCF lies in the range of 10 −3 to 10 −4 dB / turn or lower over 1300 to 1700 nm, and 2 × 10 −4 dB/turn at the wavelength of 1550 nm for a 30-mm bend radius with a higher order mode (HOM) cut-off frequency below 1200 nm for WDM application. When the whole structure of the PCF is scaled down, a bending loss of 6.78 × 10 −4 dB / turn at 1550 nm for a 4-mm bend radius is obtained, and the loss remains in the order of 10 −4 dB / turn over the same range of wavelength with an HOM cut-off frequency below 700 nm, and makes the fiber useful for FTTH applications. Furthermore, this structure is also optimized to show a splice loss near zero for fusion-splicing to a conventional single-mode fiber (SMF).