Enhancement of the efficiency of 2.7 /spl mu/m Er:ZBLAN fiber lasers via cluster formation at high doping densities

Summary form only given. The broadly tunable 2.7 /spl mu/m transition in Er:ZBLAN appears particularly attractive for the design of compact, high power CW fiber lasers of excellent beam quality, as needed for applications ranging from endoscopic laser surgery to countermeasures and spectroscopic monitoring. As is well known, the longer lifetime of the lower laser level (/sup 4/I/sub 13/2/, 9.4 ms) compared to the upper laser level (/sup 4/I/sub 11/2/, 7.5 ms) of this transition poses a serious bottleneck. The paper demonstrates conclusively that in contrast to bulk glasses, strong ion-ion interaction occurs in Er:ZBLAN fibers even at doping densities as low as 10,000 ppm. This is done by experimental and theoretical studies of saturation of absorption at 972 nm as a function of doping density, as well as by measurements of the lifetimes of the /sup 4/I/sub 11/2/ the /sup 4/I/sub 13/2/ levels as a function of doping density.