Room-temperature THz sources based on intra-cavity difference-frequency mixing in mid-infrared quantum cascade lasers

I will review the recent progress of semiconductor sources of terahertz radiation based on intra-cavity difference-frequency generation (DFG) in mid-infrared quantum cascade lasers (QCLs). These devices, referred to as THz DFG-QCLs, are similar in fabrication and operation simplicity to THz QCLs, but, unlike THz QCLs, they offer room-temperature operation and broadband spectral tuning in the entire 1-6 THz range.