Fabrication and application of small core chalcogenide glass fibers in nonlinear optics

High purity Ge-As-Se and Ge-As-S chalcogenide glasses were synthesized by a dynamic distillation technique. Small-core step-index fibers with Ge-As-Se glass core and Ge-As-S glass cladding were fabricated through a two-step rod-in-tube approach. Supercontinuum generation was measured using a femtosecond laser as the pump. The impurities associated with C, H and O could be efficiently eliminated when Al and GaCl₃ were used as the oxygen getter and C/H scavenging agent, respectively. The as-fabricated GeAsSe/GeAsS fibers have a numerical aperture of ~1.3, and show good transmitting property in the 2-9 μm spectral range. When a 22 cm long fiber with a core diameter of 6 µm is pumped with 4.6 kW peak power and 320 fs pulses at a repetition rate of 10.5 MHz at 4.0 μm, supercontinuum spanning from ~1.9 to ~8.2 µm is generated with a dynamic range of ±10 dB and an average power of ~4.5 mW.