Improving mid-infrared supercontinuum generation efficiency by pumping a fluoride fiber directly into the anomalous regime at 1995 nm

Supercontinuum sources in the mid-infrared may found many potential applications to spectroscopy and material caracterization. Supercontinuum light extending up to 4000 nm has been efficiently generated in fluorozirconate glasses (ZBLAN) with 10.5 W power using an amplified nanosecond pulsed laser diode at 1550 nm [1]. As the dispersion wavelength of the fiber is closed to 1700 nm, pumping at 1550 nm does not directly allow generation of solitons. A first approach is thus to pump a piece of SMF fiber in the anomalous dispersion regime to generate the solitons and shift them to the anomalous dispersion regime of the ZBLAN fiber [1,2]. Another approach is to use a high power femtosecond laser at 1600 nm [3]. In that case, the pulse broadens through self phase modulation up to overlap with the ZBLAN anomalous dispersion regime. In both cases, the pump wavelength is very closed to the zero dispersion wavelength of the fiber to maximize the spectrum broadening. However, a limited amount of power is generated beyond 2500 nm (30%) which is the relevant spectral window for many applications. Here we report on what we believe to be the first demonstration of direct pumping of ZBLAN in the anomalous dispersion regime at 2 µm to generate a supercontinuum extending up to 3800 nm.