Photonic generation of flat microwave frequency combs based on stimulated Brillouin scattering and linear spectral filtering

A photonic method for generating a flat microwave frequency comb (MFC) is proposed and experimentally demonstrated. By spectrally shaping an optical Nyquist pulse-specifically, implementing a linearly decreasing spectral profile and selectively amplifying a single optical spectral line-a near-flat MFC can be achieved. Theoretical analysis and simulations confirm the feasibility of the approach. In a proof-of-concept experiment, a 14-line MFC with a flatness of 4.6 dB is successfully generated. When the number of comb lines is increased to 54, the flatness is maintained at 6.5 dB.