Pulse characteristics of passively mode-locked diode lasers

For the first time to our knowledge, asymmetric pulse shapes and the linear and nonlinear chirp from a passively mode-locked semiconductor laser are directly measured. For the laser tuned to various center wavelengths, fall-time-to-rise-time ratios of 2.0 to 2.5 are measured. With the laser tuned to the shorter-wavelength side of its tuning range, a significant quadratic chirp of -60 fs/nm^2 is measured, along with a linear chirp of -800 fs/nm. The nonlinear chirp is responsible for the asymmetrically shaped compressed pulses that produce long-tailed autocorrelations.