High-power, all-fiber-integrated super-continuum source from 1.57 to 12 microns

Abstract

All-fiber integrated super-continuum (SC) sources are described based on a platform architecture that can operate in the visible, near-infrared, short-wave infrared, mid-wave infrared and long-wave infrared, with demonstrated SC wavelengths ranging from 0.47 to 12 μm. Modulation instability initiated SC generation leads to a simple SC source with no moving parts and that uses o_-the-shelf components from the mature telecommunications and fiber optics industry. The resulting light sources are basically a cascade of fibers pumped by fiber-pigtailed laser diodes and some drive and control electronics; thus, the SC sources have the potential to be cost-effective, compact, robust and reliable. Starting from fused silica fibers, the SC spectrum can be extended to shorter or longer wavelengths by cascading fibers with appropriate dispersion and/or transparency. As one example, we demonstrate a long-wave infrared SC source that generates a continuous spectrum from approximately 1.57 to 12 μm using a fiber cascade comprising fused silica fiber followed by ZBLAN fluoride fiber followed by sulfide fiber and, finally, a high-numerical-aperture selenide fiber. The time-averaged output power is as high as 417 mW at 33% duty cycle, and we observe a near-diffraction-limit, single spatial-mode beam across the entire spectral range. A prototype is described that is based on a three-layer architecture with a form factor of 16.7 × 10 × 5.7 and that plugs into a standard wall plug. This SC prototype has been used in a number of field tests as the active illuminator for stand-off FTIR system over distances of 5 to 25 m, thus enabling identification of targets or samples based on their chemical signature. Further optimization of the SC source will also be described to increase the output power and to reduce the form factor.