  A review of theoretical and experimental studies of thermal effects in
solid-state lasers is presented, with a special focus on diode-pumped
ytterbium-doped materials. A large part of this review provides however general
information applicable to any kind of solid-state laser. Our aim here is not to
make a list of the techniques that have been used to minimize thermal effects,
but instead to give an overview of the theoretical aspects underneath, and give
a state-of-the-art of the tools at the disposal of the laser scientist to
measure thermal effects. After a presentation of some general properties of
Yb-doped materials, we address the issue of evaluating the temperature map in
Yb-doped laser crystals, both theoretically and experimentally. This is the
first step before studying the complex problem of thermal lensing (part III).
We will focus on some newly discussed aspects, like the definition of the
thermo-optic coefficient: we will highlight some misleading interpretations of
thermal lensing experiments due to the use of the dn/dT parameter in a context
where it is not relevant. Part IV will be devoted to a state-of-the-art of
experimental techniques used to measure thermal lensing. Eventually, in part V,
we will give some concrete examples in Yb-doped materials, where their
peculiarities will be pointed out.

Optics