For the first time to our knowledge, asymmetric pulse shapes and the L
inear and nonlinear chirp from a passively mode-locked semiconductor l
aser are directly measured. For the laser tuned to various center wave
lengths, fall-time-to-rise-time ratios of 2.0 to 2.5 are measured. Wit
h 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 t
he asymmetrically shaped compressed pulses that produce long-tailed au
tocorrelations.