Octave-spanning semiconductor laser

We present a semiconductor injection laser operating in continuous wave with emission covering more than one octave in frequency and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous quantum cascade structure operating in the terahertz range. Laser emission in continuous wave takes place from 1.64 THz to 3.35 THz with optical powers in the milliwatt range and more than 80 modes above threshold. For narrow waveguides, a collapse of the free-running beatnote to linewidths of 980 Hz, limited by jitter, indicate frequency comb operation on a spectral bandwidth as wide as 624 GHz, making such devices ideal candidates for octave-spanning semiconductor-laser-based terahertz frequency combs. The authors report a semiconductor injection laser with a continuous wave emission spanning more than one octave, from 1.64 THz to 3.35 THz, with optical powers in the milliwatt range and more than 80 modes above threshold.