Simultaneously Achieving a Large Negative Dispersion and a High Birefringence Over Er and Tm Dual Gain Bands in a Square Lattice Photonic Crystal Fiber

We proposed a novel photonic crystal fiber composed of a double-cladding square lattice that could be used in dual-band, Er and Tm optical gain bands, simultaneously supporting a large negative dispersion and a high birefringence. We theoretically investigated the light guiding property through the proposed photonic crystal fiber by using a vectorial finite-element method with a perfectly matched layer. By optimizing the structural parameters, we obtained an ultra-large negative dispersion of -20,186 ps/(nm·km) and a very high birefringence of 9.27 × 10
^-3
at the wavelength of 1.55 μm in the Er gain band and a very large negative dispersion of -8,067 ps/(nm·km) and a high birefringence of 1.0 × 10
^-3
at the wavelength of 1.87 μm in the Tm band. We further discussed the roles of waveguide parameters on the chromatic dispersion, its slope, and the birefringence of the fiber as well as the mode field diameter. The proposed fiber could be directly applied for dual-band dispersion and polarization control in fiber laser cavities as well as optical communications and sensors in the dual bands.