The paper presents results of experimental investigations of spatial distribution of radiation emitted by quantum
cascade lasers. Measurements have been performed by means of a unique goniometric profilometer specially de-
signed for the large angle laser beams. The advantages and limitations of the set-up and the applied experimental
method are discussed. The obtained results have enabled the analysis of dependence of geometry of the beam
on the geometry of the laser structure and on the mount method of the laser chips. The angular divergence of
the beams has also been tested as a function of laser power supply.
Quantum cascade lasers (QCL’s) have proven their usefulness as light sources in many applications, like remote gas
sensing, molecular spectroscopy or free-space communication. In most cases the high-quality low-divergence beam is
desired. This work presents the theoretical analysis of QCL’s beam divergence. The electromagnetic field in the
resonator is calculated according to effective index method. Theoretical results are compared with measurements.