Photonic Generation of Microwave Signals Based on Pulse Shaping

A novel approach to generating microwave signals based on optical pulse shaping is proposed and experimentally demonstrated. The proposed system consists of a femtosecond pulse laser source, a Sagnac-loop filter (SLF), a dispersive element, and a photodetector. The spectrum of the femtosecond pulse is shaped by the SLF that has a sinusoidal spectral response. Thanks to the frequency-to-time conversion in the dispersive element, time-domain pulse exhibiting the shape of the optical power spectrum is obtained. Depending on the free-spectral range of the SLF and the total dispersion of the dispersive element, signals with frequencies up to terahertz can be generated. A model to describe the signal generation is developed. Experimental results agree well with the theoretical analysis