Abstract

We have investigated the spectra of the spontaneous and stimulated emission and transmission of CdTe at temperatures below 50K using a N₂-laser pumped dye laser for the plasma excitation. Fig. 1 depicts the spatially resolved results of luminescence measurements in a back-scattering geometry. In going from the edge to the centre of the excitation spot of approximately 40 μm diameter we observe a strong line width narrowing. At intermediate positions even two distinct emissions are observed. We attribute this to a fast carrier drift from the surface into the bulk of the sample, resulting in a spatial carrier distribution which - particularly at the center of the excitation - extends deep into the sample. The spatial variation of the luminescence is explained straightforwardly, if the two bands in Fig. 1 are attributed to the spontaneous and stimulated emission of the plasma: The stimulated emission is observed mainly at the center of the excitation since the optical amplification is strongly enhanced by the wide spatial range over which the carriers are distributed. If the plasma were limited to the absorption length of the laser, the optical path would be too short for a significant amplification.

© 1984 Optical Society of America