A new technique of measuring low-power picosecond optical pulse trains

We present a theoretic approach to the characterization of low-power bright ultrashort optical pulses with an internal frequency modulation simultaneously in both time and frequency domains. This approach exploits the Wigner time-frequency distribution, which can be determined and developed for these bright optical pulses by using a novel interferometric technique under our proposal. At first, the analysis and computer simulations are applied to studying the capability of Wigner distribution to characterize solitary pulses in practically important case of the sech-pulses. Then, the simplest two-beam scanning Michelson interferometer is selected for shaping the field-strength auto-correlation function of low-power picosecond pulse trains. We are proposing the key features of a new interferometric experimental technique for accurate and reliable measurements of the train-average width as well as the value and sign of the frequency chirp of pulses in high-repetition-rate trains. This technique is founded on an ingenious algorithm for the advanced metrology, assumes using a specially designed supplementary semiconductor cell, and suggests carrying out a pair of additional measures with exploiting this semiconductor cell. The procedure makes it possible to construct the Wigner distribution and to describe the time-frequency parameters of low-power bright picosecond optical pulses.