In this paper, we review various nonlinear wavelength conversion experiments based upon a femtosecond erbium-fiber source operating at the telecommunication wavelength of 1.55 (mu)m. By use of harmonic and sum frequency generation a nearly continuous ultra-wide band coverage from the ultraviolet through the entire visible to the near-infrared is achieved. The up-converted radiation appears in the form of ultra-short pulses with a repetition rate of approximately 100 MHz and average power levels ranging from few to more than 100 mW. In addition, we report on a concept for broadband-to-narrowband frequency doubling. Under this novel, highly efficient scheme, the harmonic component is subjected to simultaneous spectral filtering and brightness enhancement. Such performance characteristics may be of great interest to numerous applications, including high-capacity data storage, frequency-comb generation, bioimaging and spectroscopy.
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