Highly Birefringent Elliptical-Hole Photonic Crystal Fibers With Double Defect

A novel elliptical-hole photonic crystal fiber (PCF) with double defect is theoretically investigated, and its high birefringence [including both the phase-index birefringence (PIB) and the group-index birefringence (GIB)] is demonstrated, which can reach an order of 10^-2 Such a PCF can especially have a very high PIB, with a negligible GIB in a small band of normalized frequencies. The PIB of this PCF is much higher than that of the circular-hole PCF with double defect, under comparable parameters. Compared with the elliptical-hole PCF with single defect, the present PCF possesses the advantages of both a higher PIB and a larger modal area for modest ellipticities; thus, it is more suitable in linear applications, as well as in fabrication. Moreover, a novel single-polarization single-mode (SPSM) PCF with a broad wavelength band is proposed and demonstrated. In addition, a new approach in designing broadband SPSM PCFs is suggested.