Numerical design of an efficient Ho3+-doped InF3 fiber laser at～3.2 μmOA

In this work,we theoretically unlock the potential of Ho3+-doped InF3 fiber for efficient～3.2 μm laser generation(from the 5F4,5S2→5F5 transition),by employing a novel dual-wavelength pumping scheme at 1150 nm and 980 nm,for the first time.Under clad-coupled 1150 nm pumping of 5 W,～3.2 μm power of 3.6 W has been predicted with the optical-to-optical efficiency of 14.4%.Further efficient power scaling,however,is blocked by the output saturation with 980 nm pumping.To alleviate this behavior,the cascaded 5I5→5I6 transition,targeting～3.9 μm,has been activated simultaneously,therefore accelerating the population circulation between the laser upper level 5F4,5S2 and long-lived 5I6 level under 980 nm pumping.As a result,enhanced～3.2 μm power of 4.68 W has been obtained with optical-to-optical efficiency of 15.6%.Meanwhile the～3.9 μm laser,yielding power of 2.76 W with optical-to-optical efficiency of 9.2%,is theoretically achievable as well with a moderate heat load,of which the performance is even better than the prior experimentally and theoretically reported Ho3+-doped InF3 fiber lasers emitting at～3.9 μm alone.This work demonstrates a versatile platform for laser generation at～3.2 μm and～3.9 μm,thus providing the new opportunities for many potential applications,e.g.,polymer processing,infrared countermeasures,and free-space communications.