Widely tunable sub-30-fs pulses from a compact erbium-doped fiber source

Coupling femtosecond light pulses from an all-fiber Er:laser system into a dispersion-shifted and highly nonlinear fiber, we generate output spectra exhibiting two broadband and mutually coherent maxima. Depending on the chirp of the input pulse, the spectral separation is easily tunable over a wide range up to values exceeding 100 THz. In this way, the source provides access to an ultrabroadband wavelength interval from 1130 to 1950 nm. Because of soliton effects, the long-wave component exhibits a transform-limited pulse width. of 40 fs directly after the nonlinear element. The high-frequency part propagating in the dispersive regime is recompressed to pulse durations as short as 24 fs with an optimized prism sequence. (C) 2004 Optical Society of America.