Excited-state absorption at 1.57 μm in U2+:CaF2 and Co2+:ZnSe saturable absorbers

Abstract Appreciable excited-state absorption (ESA) in U2+:CaF2 and Co2+:ZnSe saturable absorbers was measured at λ=1.573 μ m by optical transmission versus light fluence curves of 30–40 ns long pulses. The ground- and excited-state absorption cross-sections obtained were (9.15±0.3)×10−20 and (3.6±0.2)×10 −20 cm 2 , respectively, for U2+:CaF2, and (57±4)×10−20 and (12.5±1)×10 −20 cm 2 for Co2+:ZnSe. Thus, ESA is not negligible in U2+:CaF2 and Co2+:ZnSe, as previously estimated.