On-chip terahertz dual-comb source based on quantum cascade lasers

We report on a detector-free on-chip dual frequency comb setup based on terahertz quantum cascade lasers. The presented dual-comb covers a bandwidth of 630 GHz with a centre frequency of 2.5 THz. Instead of a fast detector one of the lasers has been used as a fast detector itself. The frequency comb spacing was analysed using frequency counting techniques revealing an accuracy down to δf
_rep
/f
_carrier
~ 10
^-12
at the carrier frequency of 2.5 THz.