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We report numerical and experimental demonstrations of flexible group-velocity dispersion regimes in step-index tellurite fibers by fine control of the fiber core diameter. Our simple fiber design allowed us to explore various nonlinear propagation regimes beyond 2 μm, which involved careful control of four-wave mixing processes. Combined with the recent development of 2 μm fiber lasers, we present an easy way to tailor supercontinuum generation and related coherence features in the high-demand 1.5-3.5 μm spectral region.

We analyze fiber systems where the linear losses act as a strong perturbation, causing a frequency drift of the modulational instability sidebands. We achieve the total suppression of this frequency drift by means of a technique based on the concept of a photon reservoir, which feeds in situ the process of modulational instability by continually supplying it the amount of photons absorbed by the fiber.

An As2S3 fiber-based supercontinuum source that covers 3500 nm, extending from near visible to the midinfrared, is successfully reported by using a 200-fs-pulsed pump with nJ-level energy at 2.5 μm. The main features of our fiber-based source are two-fold. On the one hand, a low-loss As2S3 microstructured optical fiber has been fabricated, with typical attenuation below 2 dB/m in the 1-4 μm wavelength range. On the other hand, a 20-mm-long microstructured fiber sample is sufficient to enable a spectral broadening, spreading from 0.6 to 4.1 μm in a 40 dB dynamic range.