Millersville University 1 article published in JoVE Engineering Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies Michael Jackson1,3, Lyndon R. Zink2 1Department of Physics, Central Washington University, 2Department of Physics, University of Wisconsin-La Crosse, 3College of Science and Technology, Millersville University We describe the generation of far-infrared radiation using an optically pumped molecular laser along with the measurement of their frequencies with heterodyne techniques. The experimental system and techniques are demonstrated using difluoromethane (CH2F2) as the laser medium whose results include three new laser emissions and eight measured laser frequencies.