Ultrashort pulse propagation in highly birefringent photonic crystal fibers

Summary form only given. Supercontinuum generation in "photonic crystal" fibers results from a relatively small core size and anomalous group velocity dispersion. Although the polarization sensitivity of this process has been previously noted it has not been investigated in polarization maintaining highly birefringent fiber. We have fabricated photonic crystal fibers with an intentionally high birefringence by stacking capillaries and rods. Typically, our fibers had a core dimension in the range of 1-4 μm and polarization-mode beat lengths of substantially less than 1 mm-less than that previously reported in conventional fibers. The variation with wavelength of the group index and the dispersion of the two polarization eigenmodes in the single-mode fiber is shown. A Ti:sapphire laser was used to launch pulses of different energies (875 nm, 76 MHz repetition frequency, 200 fs FWHM pulse duration) into the fiber in different polarization states, and the output was analyzed. It is worth noting that the polarization-mode walk-off length for these pulses in this fiber is around 10.4 mm, while the group-index-matched wavelengths for 875 nm excitation are 575 nm and 665 nm. Furthermore, one can readily find wavelengths where the dispersion of the two modes eigenmodes is opposite in sign.