High-power 2.8 μm lasing in a lightly-doped Er:CaF2 crystal

Abstract

Er3+-doped crystals pumped by laser diode (LD) is an effective way to obtain near 3 μm laser, which has advantages of low cost and compact structure. CaF2 and SrF2 crystals have the fluorite structure makes Er3+ ions easy to form “clusters”, this effect shortens the space between Er3+ ions, then bring intense interionic energy transfer inside the lightly-doped crystal. Due to the existence of “clusters”, not only the self-termination process was solved, but also the severe thermal damage during the Er3+ 2.8 μm laser generation was avoided. In this work, high quality 1.7 at.% Er:CaF2 laser crystals have been successfully grown by temperature gradient method. LD pumped 2756.6 nm laser with maximum output power of 2.32 W was achieved. It is the highest laser output power generated by LD-pumped Er3+-doped fluoride crystals in recent years. Furthermore, we also demonstrated the 1532 nm LD pumped 1.7 at.% Er:CaF2 laser performance, which proved the strongly energy transfer inside the lightly-doped Er:CaF2 crystal. These results are valuable to the development of the mid-infrared laser towards the direction of compact structure and low cost.