Fiber Delivery Systems for Ultrashort Pulse Lasers

Future military and commercial laser-based systems will incorporate high peak energy ultra-short pulse lasers (USPLs) operating in the near or mid-infrared. These USPL will require a beam delivery system (BDS) for use within defensive systems. Step-index optical fibers have been used as BDSs with excellent results at low power levels. However, the high peak energies in these USPLs will irreversibly damage these fibers. An alternative to step-index fibers is the hollow-core photonic band gap (HC-PBG) fiber. Silica based HC-PBG fibers have been produced with low losses, high beam quality and high damage thresholds for wavelength to 2 um, makes them suitable for near-infrared BDS. For wavelengths beyond 2 um, an alternative glass structure must be sought. Phase I work demonstrated the feasibility of developing an innovative chalcogenide glass based HC-PBG fiber beam delivery. Fiber designs were obtained that allow transmission of USPL with high peak energy. Phase II effort will develop the design and fabrication procedures to produce chalcogenide HC-PBG fiber for 2 um. Phase II efforts will build, test and characterize chalcogenide based HC-PBG fiber BDS packaged for USPL transmission at 2 um.