Octave-spanning high-repetition-rate mid-IR supercontinuum for frequency comb synthesis

Research efforts devoted to supercontinuum (SC) light sources in a fiber-format spanning the mid-infrared (mid-IR) molecular fingerprint region is currently undergoing a dramatic increase, particularly enforced by such demanding applications as biomolecular and environmental sensing. Among various glass compositions, chalcogenides have the highest non-linearity and the broadest transparency range extending further into the mid-IR where fluoride and tellurite glasses are no longer transparent [1]. Here we demonstrate SC generation in tapered suspended-core As2Se3 photonics crystal fibers pumped by a Cr2+:ZnSe ultrafast laser with a pulse duration of 35 fs, a repetition frequency of 170 MHz and an average power of 180 mW (30 kW peak power and 1 nJ pulse energy) at 2.4 µm, based on an improved design of that reported in Ref. [2]. The generated SC covers the spectral region from 1.4 to 4.2 µm.