CaF2:Ho3+has been reported as a visible laser at 5512 Å. Operation is at a relatively high threshold power due, principally, to weak and narrow absorption lines.Preliminary experiments, using Eu2+as a sensitizer, have indicated that an order of magnitude increase in Ho3+, 5512‐Å emission intensity may readily be achieved through transfer of energy from Eu2+to Ho3+ions. Dopant concentrations, for each constituent, were nominally <1 mole%.