Supercontinuum based mid-infrared OCT, spectroscopy, and hyperspectral imaging

Mid-infrared (MIR) spatially coherent supercontinuum (SC) fiber lasers with high brightness and average power find important applications in spectroscopy-based trace gas detection, such as in pollution and food-quality monitoring. Early commercial MIR SC lasers have been limited to about 4.5m, mainly by the transmission bandwidth of the fluoride fibers typically used for the SC generation. Research-based MIR SC lasers have reached 15m, but with very low power and/or bulky and expensive pump lasers, making them irrelevant for applications. Recently the use of SC cascading in a combination of fluoride and chalcogenide fibers have seen MIR SC lasers reaching 11m with average powers around 100mW and high repetition rates [1], [2]. Here we review the state-of-the art in MIR SC lasers and demonstrate a design that provides MHz repetition rates while not using any amplifier along the fiber chain, which makes it simple, cheap and robust [2] [see spectrum in Fig. 1(g) ]. Such MHz MIR SC lasers covering most of the molecular fingerprint region are ideal for hyperspectral imaging [3] [see Fig. 1(a-f) ] and real-time Optical Coherence tomography (OCT) when combined with ultra-fast upconversion detectors [4] [see Fig. 1(h-k) ]. We present the latest results within these two particular applications, as well as in spectroscopy based trace-gas detection.