Spectrally resolved far-fields of terahertz quantum cascade lasers
  We demonstrate a convenient and fast method to measure the spectrally resolved far-fields of multimode terahertz quantum cascade lasers by combining a microbolometer focal plane array with an FTIR spectrometer. Far-fields of fundamental TM0 and higher lateral order TM1 modes of multimode Fabry-P\'erot type lasers have been distinguished, which very well fit to the results obtained by a 3D finite-element simulation. Furthermore, multimode random laser cavities have been investigated, analyzing the contribution of each single laser mode to the total far-field. The presented method is thus an important tool to gain in-depth knowledge of the emission properties of multimode laser cavities at terahertz frequencies, which become increasingly important for future sensing applications. 
Martin Brandstetter, Sebastian Sch\"onhuber, Michael Krall, Martin A.   Kainz, Hermann Detz, Tobias Zederbauer, Aaron M. And...
physics.optics