Abstract
In the present work, we report on infrared thermography measurements in Nd-doped KPb2Cl5 crystal and powder above and below the barycentre of the F-4(3/2) level that were performed in order to assess the relative weights of both the direct anti-Stokes absorption processes and those assisted by either excited state absorption or energy transfer upconversion when cooling takes place in the material. As the laser induced temperature changes are usually small, we used a special configuration of the samples that allowed us to obtain differential measurements where an undoped sample acted as a temperature baseline. This method allows us to ascertain whether the recorded temperature changes are optically induced or they are due to some other effect.