  An experimental study of the delayed threshold phenomenon in a Vertical
Extended Cavity Semiconductor Emitting Laser is carried out. Under modulation
of the pump power, the laser intensity exhibits a hysteresis behavior in the
vicinity of the threshold. The temporal width of this hysteresis is measured as
a function of the modulation frequency, and is proved to follow the predicted
scaling law. A model based on the rate equations is derived and used to analyze
the experimental observations. A frequency variation of the laser around the
delayed threshold and induced by the phase-amplitude coupling is predicted and
estimated.
