[en] In recent years the calorimetric absorption spectroscopy has been developed to a powerful tool of semiconductor spectroscopy based on the detection of nonradiative relaxation processes. Calorimetric absorption spectroscopy is an ultra sensitive quantitative absorption technique. Recent investigations of Fe in III-V semiconductors and InAs/GaAS quantum dots are presented here to illustrate the potential of the method. Sharp absorption lines have been observed at the low energy onset of the Fe^3+/2+ charge transfer band in III-V semiconductors. Calorimetric absorption spectroscopy demonstrates ground state absorption coinciding in energy with luminescence for self-organized InAs/GaAs quantum dot structures grown by MBE. Transitions to excited hole states are resolved and a comparison to photoluminescence excitation spectroscopy is presented. (author)