Demonstration of mid-IR supercontinuum generation using all-normal dispersion engineered tapered chalcogenide fiber

The mid-IR supercontinuum generation has attracted much attention during the recent years because many unique molecular absorption bands of most of the molecules exist in this domain. Additionally, mid-IR supercontinuum light sources are expected to have potential applications including astro-photonics, bio-photonic diagnostics, nonlinear spectroscopy, infrared imaging and sensing. For high spatial resolution imaging a spatially coherent supercontinuum light source is desirable. The soft-glass optical fiber is the promising medium for the design and development of a high spatially coherent mid-IR light source with the high brightness. Earlier, the broadband mid-IR supercontinuum generation has been reported using the optical fibers in different materials including tellurite, and chalcogenide, but, its coherence property has not been demonstrated extensively. In this work, we experimentally demonstrate the mid-IR supercontinuum spectrum spanning ⁓1.6 μm to 3.7 μm using a 3 cm long tapered chalcogenide step-index optical fiber pumped with femtosecond laser pulses at 2.6 μm. To justify the experimentally obtained results, a numerical simulation also carried out for the same fiber and pulse parameters. The measured supercontinuum spectrum matches well with the simulated spectrum and generated supercontinuum spectrum is highly coherent within the whole spectral range of the supercontinuum generation.