Room temperature single-mode terahertz sources based on intracavity difference-frequency generation in quantum cascade lasers

We demonstrate room temperature single-mode THz emission at 4 THz based on intracavity difference-frequency generation from mid-infrared dual-wavelength quantum cascade lasers. An integrated dual-period distributed feedback grating is defined on the cap layer to purify both mid-infrared pumping wavelengths and in turn the THz spectra. Single mode operation of the pumping wavelengths results in a single-mode THz operation with a narrow linewidth of 6.6 GHz. A maximum THz power of 8.5 mu W with a power conversion efficiency of 10 mu W/W(2) is obtained at room temperature. (C) 2011 American Institute of Physics. [doi:10.1063/1.3645016]