On chip, self detected terahertz dual comb source
We present a directly generated on chip dual comb source at terahertz (THz) frequencies. The multi heterodyne beating signal of two free running THz quantum cascade laser frequency combs is measured electrically using one of the combs as a detector, fully exploiting the unique characteristics of quantum cascade active regions. Up to 30 modes can be detected corresponding to a spectral bandwidth of 630 GHz, being the available bandwidth of the dual comb configuration. The multi heterodyne signal is used to investigate the equidistance of the comb modes showing an accuracy of 10 12 at the carrier frequency of 2.5 THz.