We have investigated the optical anisotropy of single-layer highly uniform InAs quantum dots (QDs) by photoluminescence (PL) measurements. The high uniformity of the QDs, whose PL spectrum was clearly separated into each energy level, enabled us to observe the optical anisotropy of the ground state, the first excited state and the second excited state separately. The degree of linear polarization (DLP) was obtained to be 15.8%, 14.3% and 8.3% for the ground state, the first excited state and the second excited state, respectively. This result shows that the DLP is smaller for higher-energy states. We also measured the time evolutions of the PL polarization components using a streak camera. The DLP was found to remain constant during the measured time range. (c) 2013 Elsevier B.V. All rights reserved.