Fe-doped ZnS film fabricated by electron beam evaporation and its application as saturable absorber for Er:ZBLAN fiber laser*

High-quality Fe-doped ZnS films have been fabricated by electron beam evaporation. After the doping, the fabricated films still maintain the preferential crystalline orientation and phase purity of the host ZnS. According to the observation of surface morphology, the root mean-square roughness of the samples increases slightly with the increase of doping content. All of the prepared samples are in cubic zinc blende structure of ZnS. Transmission spectrum confirms a more obvious dip near 3 μm with higher dopant concentration and it can be attributed to the typical 5E→5T2 transition of Fe2+. Fe-doped ZnS film is also successfully used for Q-switched Er:ZBLAN fiber laser.