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We present mid-infrared supercontinuum sources based on chalcogenide, tellurite, and liquid-filled capillary fibers and sub-picosecond oscillator pumping. Depending on the fiber geometry and material, the experimentally achieved spectral bandwidths and output powers vary significantly. In As 2 S 3 chalcogenide step-index fibers we achieve a maximum output power of 550 mW at a spectral width of 2 μm, covering the important transparent atmospheric window between 3 and 5 μm. In tellurite step-index fibers we attain an ultra-broadband spectrum ranging from 1.3 to 5.3 μm with an average power of 150 mW. The spectral behavior of the supercontinua is investigated by changing the pump wavelength, core diameter, fiber length, and pump power. As pump source we use high repetition rate (42 MHz) optical parametric oscillators/amplifiers which deliver Watt-level pulses tunable between 1.4 – 4.1 μm. These supercontinuum sources promise to be excellent laboratory tools for high resolution spectroscopy owing to their high brilliance and near TEM00 spatial beam profiles.

We use liquid-filled capillary fibers with different core diameters to precisely characterize the nonlinear refractive index of the highly nonlinear liquids carbon disulfide, nitrobenzene, and toluene. We present measurements with two different femtosecond pump sources at wavelengths of 1032 and 1560 nm. The large nonlinearity of the liquids results from the retarded nonlinear optical response of the liquid molecules which includes a strong non-instantaneous contribution due to molecular reorientation. The nonlinear refractive index of the liquids is determined by fitting numerical simulations based on solving the generalized nonlinear Schrodinger equation including retarded response to the measured broadened output spectra. Our work is important for the novel field of near- and mid-IR supercontinuum generation in liquid-core optical fibers.

The evolution of supercontinuum generation in chalcogenide suspended-core microstructured optical fibers is studied with regard to their exposure to the room atmosphere. We report the experimental proof of aging-induced supercontinuum generation drift in chalcogenide microstructured fibers. Mid-infrared supercontinuum covering the 2.5–5.5-µm spectral region is demonstrated in a fresh and 7-month-aged counterpart As2S3 fibers, by means of a home-built multistage oscillator power amplifier delivering 300 fs pulses at a repetition rate of 43 MHz in the 3.0–4.1-µm range. Numerical simulations based on the generalized nonlinear Schrodinger equation confirm the significant alteration of supercontinuum generation due to increasing fundamental OH and SH absorption bands.

We are able to generate red-shifted dispersive waves up to a wavelength of 5.1 µm by pumping a W-type index tellurite fiber in the anomalous dispersion regime between its two zero dispersion wavelengths.

We demonstrate a tunable and robust femtosecond supercontinuum source with a maximum output power of 550 mW and a maximum spectral width of up to 2.0 μm which can cover the mid-infrared region from 2.3 μm up to 4.9 μm by tuning the pump wavelength. As light source we use a synchronously pumped fiber-feedback OPO and a subsequent OPA which delivers femtosecond, Watt level idler pulses tunable between 2.5 μm and 4.1 μm. These pulses are launched into As 2 S 3 chalcogenide step-index fibers with core diameters of 7 and 9 μm. The spectral behavior of the supercontinuum is investigated by changing the pump wavelength, core diameter, fiber length, and pump power. Self-phase modulation is identified as the main broadening mechanism in the normal dispersion regime. This source promises to be an excellent laboratory tool for infrared spectroscopy owing to its high brilliance as demonstrated for the CS 2 - absorption bands around 3.5 μm.

We demonstrate broadband supercontinuum generation over two infrared octaves, spanning from 1.3 to 5.3 μm, with an output power of 150 mW in robust step-index tellurite fibers with core diameters between 3.5 and 4.3 μm. As a pump source, we use femtosecond mid-IR pulses from a home-built post-amplified optical parametric oscillator tunable between 1.5 and 4.0 μm at a 43 MHz repetition rate. We study the influence of core size, pump wavelength, and fiber length to optimize the spectral bandwidth. A key requirement for efficient spectral broadening is a low and rather flat average anomalous dispersion over a wide spectral range that can be tailored accordingly by changing the fiber core diameter. Numerical simulations based on the generalized nonlinear Schrodinger equation are in good agreement with experimental results.

We report on a precisely tunable and highly stable femtosecond oscillator-pumped optical parametric amplifier at a 41.7 MHz repetition rate for spectroscopic applications. A novel concept based on cw-seeding of a first amplification stage with subsequent spectral broadening and shaping, followed by two further amplification stages, allows for precise sub-nanometer and gap-free tuning from 1.35 to 1.75 μm and 2.55 to 4.5 μm. Excellent spectral stability is demonstrated with deviations of less than 0.008% rms central wavelength and 1.6% rms bandwidth over 1 h. Spectral shaping of the seed pulse allows precise adjustment of both the bandwidth and the pulse duration over a broad range at a given central wavelength. Transform-limited pulses nearly as short as 107 fs are achieved. More than half a Watt of average power in the near- and more than 200 mW in the mid-infrared with power fluctuations less than 0.6% rms over 1 h provide an excellent basis for spectroscopic experiments. The pulse-to-pulse power fluctuations are as small as 1.8%. Further, we demonstrate for the first time, to the best of our knowledge, that by using hollow-core capillaries with highly nonlinear liquids as a host medium for self-phase modulation, the signal tuning range can be extended and covers the region from 1.4 μm up to the point of degeneracy at 2.07 μm. Hence, the idler covers 2.07 to 4.0 μm.