Generation and characterization of multimode quantum frequency combs

The study of intensity noise correlations over the optical spectrum spanned by the squeezed frequency comb allows one to extract a covariance matrix, whose eigenvectors are frequency-comb modes directly related to the supermodes and whose eigenvalues give the amount of squeezing in each mode. Performing this analysis for a 0.7-dB intensity squeezed frequency comb, we obtained what constitutes the main result of this work revealing experimentally the intrinsic multimode quantum character of the SPOPO output.