High-power continuous-wave 3- and 2-μm cascade Ho/sup 3+/:ZBLAN fiber laser and its medical applications

A new medical fiber laser oscillating at two useful wavelengths (3 and 2 /spl mu/m) is reported. We have demonstrated highly efficient and high-power continuous-wave cascade oscillation at room temperature with a holmium ion-doped fluoride glass fiber laser pumped with a 1.15-/spl mu/m fiber Raman laser. The simultaneous oscillation wavelengths were 3 and 2 /spl mu/m, and their combined output power was 3.0 W with a slope efficiency of 65%. To our best knowledge, this is the first achievement of watt-level-output power in the mid-infrared region with ZrF/sub 4/-BaF/sub 2/-LaF/sub 3/-AlF/sub 3/-NaF (ZBLAN) glass fiber. In experiments to evaluate potential for medical applications, we tested the two wavelength beam as a laser surgical knife on soft rabbit tissues and demonstrated that it had strong cutting capability, and that the coagulation layer thickness could be controlled by varying the power ratio of the two-wavelength laser.