Er:CaF2 single crystal fiber Q-switched laser with diode pumping in the mid-infrared region

Abstract Er3+-doped CaF2 single crystal fibers (SCFs) were successfully grown using a modified temperature gradient technique (TGT) method. With a fiber-coupled 976 nm laser diode (LD) pump source and 4 at.% Er:CaF2 SCF, mid-infrared region (MIR) laser operations were realized for the first time. A passively Q-switched Er:CaF2 SCF laser at 2.8 μm was demonstrated by using graphene saturable absorber (SA). Under an absorbed pump power of 1.52 W, a maximum output power of 220 mW was obtained with a pulse duration of 632.9 ns and a repetition rate of 59.41 kHz, corresponding single pulse energy and peak power are 3.70 μJ and 5.85 W, respectively. The dependence of the operational parameters on pump power was also investigated experimentally. We also found that the SCF possess superior laser performance when compared with Er:CaF2 bulk crystal. Those results implied SCF is a promising laser gain medium.