Increasing the blue-shift of a supercontinuum by modifying the fiber glass composition.

Supercontinuum light sources spanning into the ultraviolet- visible wavelength region are highly useful for applications such as fluorescence microscopy. A method of shifting the supercontinuum spectrum into this wavelength region has recently become well understood. The method relies on designing the group-velocity profile of the nonlinear fiber in which the supercontinuum is generated, so that red-shifted solitons are group-velocity matched to dispersive waves in the desired ultraviolet-visible wavelength region. The group-velocity profile of a photonic crystal fiber (PCF) can be engineered through the structure of the PCF, but this mostly modifies the group-velocity in the long-wavelength part of the spectrum. In this work, we first consider how the group-velocity profile can be engineered more directly in the short-wavelength part of the spectrum through alternative choices of the glass material from which the PCF is made. We then make simulations of supercontinuum generation in PCFs made of alternative glass materials. It is found that it is possible to increase the blue-shift of the generated supercontinuum by about 20 nm through a careful choice of glass composition, provided that the alternative glass composition does not have a significantly higher loss than silica in the near-infrared. (c) 2008 Optical Society of America