Coherent propagation of polaritons in semiconductor heterostructures: Nonlinear pulse transmission in theory and experiment

The influence of coherent optical nonlinearities on polariton effects is studied by means of a detailed comparison of theory and experiment. A unique approach that combines a microscopic treatment of the boundary problem in a sample of finite thickness with excitonic and biexcitonic nonlinearities is introduced. Spectral changes that depend on the light polarization are analyzed for single pulse transmission and pump and probe excitation.

Figure 1

(a) Dashed-dotted line: Linear transmission $T$ (depicted as $1-T$) for a pulse energy of $1.2\mathrm{pJ}$ for the $20\text{−}\mathrm{nm}$ ZnSe sample. Dotted line: Spectral shape of the $110\text{−}\mathrm{fs}$ laser pulse. Nonlinear transmission for a pulse energy of $12.2\mathrm{pJ}$ for linear (solid line) and circular (dashed line) light polarization. (b) Optically induced transmission changes $\Delta T$ for linear (solid line) and circular (dashed line) light polarization, corresponding to the data in (a). (c) and (d) Theoretical results corresponding to (a) and (b), without the influence of Fabry-Perot effects (see discussion in the text).

Figure 2

(a) Solid line: Calculated linear transmission spectrum $T$ (depicted as $1-T$) for a GaAs layer with five exciton Bohr radii thickness. Dashed line: Spectral shape of a $120\text{−}\mathrm{fs}$ laser pulse. (b) Differential probe transmission $\Delta T$ for opposite circular (solid line), and cocircular (dashed-dotted line) polarization of pump and probe pulses. (c) Differential probe transmission $\Delta T$ for opposite circular polarization including all Coulomb terms (solid line) and without Coulomb interaction of different polaritons (dashed line).