Spectral broadening of femtosecond pulses in a single-mode As-S glass fiber.

We report a strong spectral broadening of femtosecond pulses propagating in a single-mode As-S glass fiber of 1.5 m length. The pump pulse spectrum is broadened by a factor of five when the input power is grown up to 16.4 mW. The broadened spectra are nearly symmetric and self-phase modulation is believed to be the dominant nonlinear effect responsible for this process.