Interference between third- and fifth-order polarizations in semiconductor doped glasses

We report on time-delayed wave-mixing experiments which allowed, for the first time, the observation of ultrafast modulation due to the interference between third- and fifth-order optical polarizations. The new effect was observed in semiconductor doped glasses by controlling the relative phase of the optical fields which induce distinct wave-mixing processes. The experiments allowed us to measure the relative phase between the nonlinear susceptibilities χ⁽³⁾ and χ⁽⁵⁾ as well as their relative magnitude. In principle the interference effect may be observed in a large variety of materials and the exploitation of this phenomenon to develop a new technique for nonlinear spectroscopy is also discussed.