Tapered Chalcogenide-Glass Rods for Multi-Octave Mid-Infrared Supercontinuum Generation

Supercontinuum (SC) generation has been studied extensively in various optical fibers. During the last 15 years, the interest has significantly shifted toward the mid-infrared (mid-IR) spectral region where molecules display fundamental vibration absorptions [1]–[2]. Among soft glasses, chalcogenides exhibit suitable transparency that makes them the unique candidate for fiber-based SC sources spanning the entire mid-IR (2–20 µm). However, the ability to handle high-quality glasses and fiber drawing to fabricate engineered low-loss fibers for SC generation beyond 10–12 µm is very challenging [3]. Here we propose an alternative approach to facilitate future developments of fiber SC sources reaching the 15–20 µm waveband, by simply post-processing of a chalcogenide rod-type fiber (i.e., a single-index fiber). We then demonstrate its efficiency by reporting on mid-IR SC generation spanning from 1.7 to 16 µm with femtosecond pulse pumping of a 5-cm-long tapered Ge-Se- Te rod.