“…First demonstrations were performed on ruby crystals [8,9], but the photon echo spectroscopy also has a long standing history in semiconductor optics. It has been used to study different types of exciton dynamics, ranging from exciton-exciton scattering [10,11,12,13] to exciton-phonon coupling [14,15], and it has been applied to three dimensional bulk [10,16,17], two dimensional quantum well [18,19], one dimensional nanowire [20], and zero dimensional quantum dot structures [21,22,23,24]. However, the technique is not restricted to solid state samples; it has also been applied to liquids [25,26,27].…”