Chalcogenide-glass clad fiber delivers high power at mid-IR wavelengths
Newly developed sulfide and telluride glass fibers show potential for delivery of high-power infrared (IR) radiation. Developed by researchers at the Naval Research Laboratory (NRL, Washington DC), an arsenic sulfide (AsS) clad, arsenic sulfur selenide (AsSSe) core fiber was tested with a Ho:YLF laser operating at 2 µm with a 15-ns pulsewidth. The output power was monitored with time; reductions in transmission efficiency and subsequent visible inspection indicated damage. A 0.35-m-long, 150-µm-core-diameter, 240-µm-cladding-diameter sample tolerated a peak power density of 50 MW/cm2 without degradation. A 1-m-long piece of the same fiber was tested with 6.2 W of CW input power at 5.4 µm from a CO laser. Fiber core diameter was 200 µm, cladding diameter was 330 µm, and peak input-power density was 126 kW/cm2. Transmission efficiency was 60%, although after a few minutes at peak power the epoxy surrounding the input endface in the connector began to melt. The group also examined the robustness of glass-clad germanium arsenic selenium telluride (GeAsSeTe) fiber with 1.73 W of input power from a CO2 laser at 10.6 µm. A 1-m sample with 162-µm core diameter and 270-µm cladding diameter transmitted roughly 35% of the input power. Maximum input-power density was 54 kW/cm2, and no fiber damage was detected. Team member Lynda Busse reported these results last month at the Annual Symposium on Optical Materials for High Power Lasers (Boulder, CO) and said that the materials have potential for industrial-laser fiber delivery systems.