Holmium YAG lasers are applied in many modern technology fields. Besides environmental control, especially medical applications became of increasing importance for this laser type because of the advantages for special surgery, involving osteotomy and cutting of strongly vasculated tissue. For an improved efficiency, most of these applications require Ho:YAG-laser systems with increased output power and better beam parameters. A key problem in the development of this new generation of high power Ho:YAG-lasers is the power handling capability of the available optical components. The present investigations are concentrated on the characterization and optimization of optical laser components for the MIR spectral range. A series of partial reflectors, windows and uncoated substrates of different materials has been investigated by laser calorimetry, spectrophotometry and an adapted electron microscopic method. Also, the temperature shift of the spectral characteristics was measured and evaluated in respect to the microstructure of the coating systems. The results are discussed in consideration of the power handling capability of the produced laser components for 2.1 μm.