Two Color micro-photoluminescence excitation studies of exciton states in Coupled Quantum Dots

In this report we examined the charge states of various excitons found in the optical spectra of coupled In$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$As quantum dots (QDs) grown by molecular beam epitaxy, under two color optical excitation. This experiment is performed by using micro-photoluminescence excitation technique, where we keep the excitation energy of one laser fixed at the energy of wetting layer (non-resonant excitation) and tuning the excitation energy of the other laser through the states of quantum dot (resonant excitation). This study may help identifying enhanced states of various charge excitons, which are possibly useful for generating on demand entangle photon pairs with QDs.