Complete Characterization of an Optical Pulse Based on Temporal Interferometry Using an Unbalanced Temporal Pulse Shaping System

We propose and demonstrate a simple method for the full characterization of an ultrashort optical pulse based on temporal interferometry, using an unbalanced temporal pulse shaping (UB-TPS) system. The UB-TPS system consists of a Mach-Zehnder modulator and two dispersive elements (DEs) having opposite dispersion, but nonidentical in magnitude. The entire system can be considered as a typical balanced TPS system for a real-time Fourier transformation to generate two time-delayed replicas of the input optical pulse, followed by a residual DE to perform a second real-time Fourier transformation to convert the two time-delayed pulse replicas to two frequency-sheared optical spectra. The spectral interferometry is performed in the time domain. The spectral magnitude and phase information of the input optical pulse is accurately and unambiguously reconstructed from the recorded temporal interference pattern based on a Fourier transform algorithm. Compared with a conventional pulse characterization system based on linear interferometric measurement using an optical interferometer implemented by using discrete components, the proposed system features better stability, higher adaptability, and single-shot measurement. The use of the proposed system for the characterization of a femtosecond pulse before and after passing through a 60-m-long single-mode fiber is experimentally demonstrated.