Phase jumps in the reflected light of a ZnSe layer

We study the spectrum of light reflected at a ZnSe layer in terms of the density of carriers, which previously were injected by a pump pulse. Applying the method of phase‐resolved spectral interferometry we are able to investigate both amplitude and phase of the reflected light. While there are only weak changes in the amplitude with increasing excitation, the phase changes drastically. In case of the non‐excited sample the phase exhibits a jump at the hh‐exciton resonance by 2π. The jump vanishes with increasing intensity of the pump.