Electrically pumped Terahertz quantum well sources

Far infrared emission from quantum cascade structures is presented. Surface emission from a grating coupler show that the intersubband luminescence of our vertical transition structure is limited at low temperature by electron–electron scattering. As the temperature is increased, the limitation comes from the emission of optical phonons. In order to check for material gain, waveguide loss and differential gain measurements have been performed using a single-pass-type measurement. We report waveguide losses of View the MathML source and differential gain of View the MathML source. Our results strongly suggest the possibility of far-infrared lasers using the quantum cascade technology coupled to double plasmon waveguides.