Thermal Shock - Thermal Shock Parameter in The Physics of Solid-state Lasers

Thermal Shock Parameter in The Physics of Solid-state Lasers

The laser gain medium generates heat. This heat is drained through the heat sink. The transfer of heat occurs at a certain temperature gradient. The non-uniform thermal expansion of a bulk material causes the stress and tension, which may break the device even at a slow change of temperature. (for example, continuous-wave operation). This phenomenon is also called thermal shock. The robustness of a laser material to the thermal shock is characterized by the thermal shock parameter. (see above)

Roughly, at the efficient operation of laser, the power of heat generated in the gain medium is proportional to the output power of the laser, and the coefficient of proportionality can be interpreted as heat generation parameter; then, The heat generation parameter is basically determined by the quantum defect of the laser action, and one can estimate, where and are frequency of the pump and that of the lasing.

Then, for the layer of the gain medium placed at the heat sink, the maximal power can be estimated as

where is thickness of the layer and is the transversal size. This estimate assumes the unilateral heat drain, as it takes place in the active mirrors. For the double-side sink, the coefficient 4 should be applied.