Abstract
Broadband, mid-infrared supercontinuum generation in a step-index fluoroindate fibre is reported. By using ~70-picosecond laser pulses at 2.02 μm, provided by an optical parametric generator, a wide spectrum with a cut-off wavelength at 5.25 μm and a 5-dB bandwidth covering the entire 2–5 μm spectral interval has been demonstrated for the first time. The behaviour of the supercontinuum was investigated by changing the peak power and the wavelength of the pump pulses. This allowed the optimal pumping conditions to be determined for the nonlinear medium that was used. The optical damage threshold for the fluoroindate fibre was experimentally found to be ~200 GW/cm2.
Highlights
Broadband, mid-infrared supercontinuum generation in a step-index fluoroindate fibre is reported
The material zero dispersion wavelength (ZDW) of this fibre family is located at wavelengths beyond 4.5 μm, which means that direct pumping of the fibres with standard lasers operating at wavelengths up to 2.1 μm is not optimum for efficient SC generation
Supercontinuum generation in the InF3 fibre was investigated as a function of pump wavelength and pulse energy/peak power launched into the fibre
Summary
Mid-infrared supercontinuum generation in a step-index fluoroindate fibre is reported. For SC generation beyond this wavelength, fibres with longer infrared transmission windows, along with an appropriate choice of dispersion and nonlinearity are required. The situation is different in case of fluoride fibres, which have already been used for high power, Watt-level, SC generation[8] Both fluorozirconate (ZBLAN) and fluoroindate (InF3) step-index fibres exhibit a ZDW within the wavelength range covered by the most popular and powerful laser systems operating from ~1.5 to 2.1 μm. Theberge et al.[23] used a 9.5-m long 16 μm core fibre (NA = 0.14) with a cut-off wavelength at 2.8 μm pumping it by 70 fs pulses at 3.4 μm As a result, they achieved the generation of 20 dB spectral flatness SC spanning from 2.7 to 4.7 μm.
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