4. Single-crystal fibers as laser media

In the laser field, as soon as the laser system involves high power levels and absorption exceeds at least ten watts, the issues of heating and thermo-optical effects play a fundamental role. Single-crystal fibers offer a hybrid geometry that combines the advantages of fibers in terms of thermal management and those of solid crystals in terms of intrinsic laser properties. In solid-crystal lasers, the pump is focused in the crystal, then diverges. The part absorbed outside the laser mode is then lost to the laser. What's more, the thermal charge is largely concentrated in the crystal at the point where the pump is focused, heating it up locally and creating a steep thermal gradient. As shown in figure 12 , heat dissipation...