Locking of Terahertz Semiconductor Dual-Comb Laser Sources

We report on an active stabilization of a terahertz quantum cascade laser (QCL) dual-comb source by phase locking one of the dual-comb lines. Although only one dual-comb line is locked, the phase noise of other dual-comb lines close to the phase locked line is significantly reduced. Furthermore, it is demonstrated that the QCL comb without a control of the repetition rate can produce pulsed-type waveforms.