On chip, self detected THz dual comb spectrometer
We present a directly generated on chip dual comb source at THz frequencies. The multiheterodyne 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 multiheterodyne 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.