Modifying exciton optical properties in quantum dots with coherent phonons induced by ultrafast optical pulses

The distinctive effects of coherent phonons (groups of phase-matched phonons) on exciton states are reported by using single dot photoluminescence (PL) spectroscopy in semiconductor quantum dots (QDs). Coherent phonons that were induced with titanium thin metal films close to QDs by irradiating ultrafast optical pulses caused marked changes in the PL spectra including changes to the PL peak energies and PL intensities. Time-dependent reflectance measured with a pump-probe technique confirmed that coherent phonons were created at the surface of the QD sample. These results suggest that coherent phonons provide a good way to manipulate the optical properties of QDs.