Low-loss, robust fusion splicing of silica to chalcogenide fiber for integrated mid-infrared laser technology development

We demonstrate a low-loss, repeatable, and robust splice between single-mode silica fiber and single-mode chalcogenide (CHG) fiber. These splices are particularly difficult to create because of the significant difference in the two fibers' glass transition temperatures (similar to 1000 degrees C) as well as the large difference in the coefficients of thermal expansion between the fibers (similar to 20 x 10(-6)/degrees C). With 90% light coupled through the silica -CHG fiber splice, predominantly in the fundamental circular-symmetric mode, into the core of the CHG fiber and with 0.5 dB of splice loss measured around the wavelength of 2.5 mu m, after correcting only for the Fresnel loss, the silica-CHG splice offers excellent beam quality and coupling efficiency. The tensile strength of the splice is greater than 12 kpsi, and the laser damage threshold is greater than 2 W (CW) and was limited by the available laser pump power. We also utilized this splicing technique to demonstrate 2 to 4.5 mu m ultrabroadband supercontinuum generation in a monolithic all-fiber system comprising a CHG fiber and a high peak power 2 mu m pulsed Raman-shifted thulium fiber laser. This is a major development toward compact form factor commercial applications of soft-glass mid-IR fibers. (C) 2015 Optical Society of America