Tapered chalcogenide optical fibers improve supercontinuum performance

Aug. 9, 2017
Supercontinuum generation from 1 to 11.5 μm from a tapered chalcogenide photonic-crystal fiber has been demonstrated.

When generating mid-infrared (mid-IR) supercontinuum light using a pump laser and a chalcogenide optical fiber, it is difficult to obtain broad wavelength coverage and high average power, primarily because of the low damage threshold of chalcogenide fibers as well as the peak power/average power tradeoff in available mid-IR pump sources. To improve upon current mid-IR supercontinuum performance that spans from 2 to around 15 μm with submilliwatt output powers by pumping chalcogenide large-core step-index fibers with optical parametric amplification (OPA)-based sources, researchers from the Technical University of Denmark, SelenOptics, the University of Rennes, and NKT Photonics demonstrated supercontinuum generation from 1 to 11.5 μm with a high average power of 35.4 mW from a tapered chalcogenide photonic-crystal fiber (PCF).

The large mode area of the untapered germanium arsenide selenide (Ge10As22Se68) PCF enables improved coupling efficiency and high damage threshold when accepting the pump light, while the tapered section offers strong nonlinear interaction and reduced dispersion for the pump wavelength, improving supercontinuum performance. The tapered PCF only allows single-mode propagation of the beam, improving beam quality and reducing losses because of high-order mode stripping. Experimental fiber optimization studies settled on ~31 cm total fiber length with a 15–20 cm long tapered waist with 6 μm core diameter and 2–3 cm long taper-transition regions, while a numerical study concluded that the waist section could be reduced to a few centimeters to reduce losses. Pumping this fiber with a 4 μm single-pass OPA with a 250 fs pulse duration, 21 MHz repetition rate, and 230 mW pump power produced supercontinuum generation at an average power of 57.3 mW from 1 to 8 μm. Reference: C. Rosenberg Petersen et al., Opt. Express, 25, 13, 15336–15348 (2017).

About the Author

Gail Overton | Senior Editor (2004-2020)

Gail has more than 30 years of engineering, marketing, product management, and editorial experience in the photonics and optical communications industry. Before joining the staff at Laser Focus World in 2004, she held many product management and product marketing roles in the fiber-optics industry, most notably at Hughes (El Segundo, CA), GTE Labs (Waltham, MA), Corning (Corning, NY), Photon Kinetics (Beaverton, OR), and Newport Corporation (Irvine, CA). During her marketing career, Gail published articles in WDM Solutions and Sensors magazine and traveled internationally to conduct product and sales training. Gail received her BS degree in physics, with an emphasis in optics, from San Diego State University in San Diego, CA in May 1986.

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