Ground state depletion - A step towards mid-IR lasing of doped silver halides

We show for the first time ground state absorption saturation in a doped silver halide crystal (AgClxBr1−x), specifically with cobalt. Spectroscopic studies showed absorption bands in the 1.4-2.5 μm region and emission bands in the 3.8-5.0 μm region, with a 1.5 ms lifetime at low temperatures. Absorption saturation indicates a good low and room temperature lasing feasibility at 4.1 μm. In addition, a comparison of cobalt, nickel and iron as dopants is presented. These doped silver halide crystals can be extruded to form optical fibers, possibly introducing a new family of fiber lasers for the middle infrared.