Coherently-averaged dual comb spectrometer at 7.7 µm with master and follower quantum cascade lasers

We demonstrate coherent averaging of the multi-heterodyne beat signal between two quantum cascade laser frequency combs in a master-follower configuration. The are mutually locked by acting on drive current to control their relative offset and radio-frequency extraction injection locking intermode stabilize mode spacing difference. By implementing an analog common-noise subtraction scheme, reduction linewidth all heterodyne notes five orders magnitude is achieved compared free-running lasers. compare stabilization post-processing corrections terms amplitude noise. While they give similar performances signal-to-noise ratio, real-time processing stabilized less demanding computational power. Lastly, proof-of-principle spectroscopic measurement was performed, showing possibility reduce amount data be processed three magnitude, system.