Temporal Imaging of Optical Asymmetric Waveform Pulses With a Time Lens

In this paper, we investigated the imaging condition of asymmetric pulses on a temporal imaging (TI) system comprising two optical fibers and a phase modulator. We introduced a fitness function to evaluate the difference between target and output waveforms to quantitatively estimate TI characteristics. We successfully determined the optimal combination of phase modulation index and phase deviation to provide good TI by simulating the fitness function. We generated chirp-free pulses with symmetric and asymmetric waveforms using an in-line waveguide pulse synthesizer, i.e., an optical pulse synthesizer, based on pulse shaping and experimentally confirmed the TI condition in a time lens system. Moreover, TI was achieved not only at a theoretical value of the modulation index satisfying the TI condition but at a much smaller value than the theoretical value for a time-reversal mode as well. Measured waveforms of the experimental output agreed with simulation results. This may be important for practical applications because a TI system requires a much smaller modulation power.