Abstract
The coherent optical response from 140 nm and 65 nm thick ZnO epitaxial layers is studied using four-wave-mixing spectroscopy with picosecond temporal resolution. Resonant excitation of neutral donor-bound excitons results in two-pulse and three-pulse photon echoes. For the donor-bound A exciton () at temperature of 1.8 K we evaluate optical coherence times ps corresponding to homogeneous line widths of , about two orders of magnitude smaller as compared with the inhomogeneous broadening of the optical transitions. The coherent dynamics is determined mainly by the population decay with time ps, while pure dephasing is negligible. Temperature increase leads to a significant shortening of due to interaction with acoustic phonons. In contrast, the loss of coherence of the donor-bound B exciton () is significantly faster () and governed by pure dephasing processes.
- Received 12 February 2017
- Revised 29 May 2017
DOI:https://doi.org/10.1103/PhysRevB.96.035203
©2017 American Physical Society