Contribution Of Two-photon Absorption Research Articles

Nonlinear photoluminescence of graded-gap AlxGa1−x As solid solutions

Dependences of photoluminescence (PL) intensity for undoped and doped graded-gap AlxGa1−x As (x≲0.36) solid solutions on the excitation level J (1019 photon cm−2 s−1≲J≲1022 photon cm−2 s−1) were investigated for various built-in electric fields E=e −1▽E g (85 V/cm≲E≲700 V/cm). It was found that the accelerating effect of the field E gives rise to a complex dependence of intensity of the edge PL (I) on the excitation level. The nonlinearity of the I(J) dependence is attributed to the contribution of the two-photon absorption of PL emission when the latter is reemitted. An optimal range of E values exists (120 V/cm≲E≲200 V/cm). In this range, the contribution of two-photon absorption to the reemission process in undoped solid solutions is largest.

Two-photon absorption resonance effects in the third-order responses of transparent liquids

Two-photon absorption (TPA) resonance effects on the ultrafast pump–probe and transient grating (TG) responses of some transparent liquids excited with 400 nm pulses are demonstrated. The contribution of TPA and ground state Raman responses are separated in a TG experiment when the third-order polarization signal is viewed in the appropriate phase-matched direction as shown for the homodyne, TG response of CS 2. The pump–probe dichroic responses of liquids with (CS 2 and CH 3I) and without (H 2O, CCl 4, and CH 3OH) TPA resonances at 200 nm are compared. These results are discussed in the context of a perturbative third-order polarization treatment of TPA.