A. Ortigosa-Blanch

Highly birefringent photonic crystal fibers

We report a strongly anisotropic photonic crystal fiber. Twofold rotational symmetry was introduced into a single-mode fiber structure by creation of a regular array of airholes of two sizes disposed about a pure-silica core. Based on spectral measurements of the polarization mode beating, we estimate that the fiber has a beat length of approximately 0.4 mm at a wavelength of 1540 nm, in good agreement with the results of modeling.

Anomalous dispersion in photonic crystal fiber

We describe the measured group-velocity dispersion characteristics of several air-silica photonic crystal fibers with anomalous group-velocity dispersion at visible and near-infrared wavelengths. The values measured over a broad spectral range are compared to those predicted for an isolated strand of silica surrounded by air. We demonstrate a strictly single-mode fiber which has zero dispersion at a wavelength of 700 mm. These fibers are significant for the generation of solitons and supercontinua using ultrashort pulse sources.

Structural rocking filters in highly birefringent photonic crystal fiber

We report what we believe is the first example of efficient rocking filter formation in polarization-maintaining photonic crystal fiber. Very high coupling efficiencies (as much as -23.5-dB suppression of the input polarization) and loss of < 0.02 dB were achieved for fibers as short as 11 mm. The filters, which we prepared by periodic mechanical twisting and heating with a scanned CO2 laser beam, are highly compact, and they are expected to be temperature stable.

Pulse breaking and supercontinuum generation with 200-fs pump pulses in photonic crystal fibers

We have carried out a detailed experimental study of the behavior of 200-fs pulses in highly nonlinear photonic crystal fiber to elucidate the mechanisms for supercontinuum generation. To avoid unwanted polarization effects, our experiments were performed using polarization-maintaining fiber. The experimental evidence shows that, as in conventional fibers, Raman scattering leads to the breakup of higher-order solitons, which is accompanied by the generation of radiation at shorter wavelengths than the pump, leading eventually to an ultrabroad supercontinuum.