Multiphonon absorption coefficients in solids: a universal curve

Nonlinear spectra of ZnO: reverse saturable, two- and three-photon absorption

“…2(a) and Fig. 2(b) are theoretical fits determined from modelling the nonlinear optical absorption coefficient as described by Brandi and Araujo [15]. For these fittings we used the characteristic parameters (effective mass of the conduction band, reduced effective mass, refractive index and band-gap energy) of ZnO, obtained from the literature [10].…”

“…Simultaneous absorption of twoand three-photons were observed in the ranges of 540-760 nm and 820-980 nm, respectively. The multiphoton absorption processes were modeled by a theory developed by Brandi and Araujo [15], which properly describe the experimental results. In the region of 460-500 nm we observed a reverse saturable absorption due to one-photon excitation of deep levels in ZnO.…”

“…The reason is that near E photon /E gap = 0.46, there is a mixture of two-and three-photon absorption. It is important to mention that in the theoretical fitting with Brandi and Araujo [15] theory, represented by the solid lines in Fig. 2, the effective mass of conduction band, the reduced effective mass and the refractive index of ZnO used are those reported in the literature [9].…”

Three-photon absorption in ZnO and ZnS crystals

“…3PA coefficients plotted as a function of E photon /E g , where E photon is the photon energy and E g is the band-gap energy. The solid stars and squares are the experimental data, while the solid and dashed lines are calculated from the theory of Brandi and de Araujo [19] and the theory of Wherrett [25], respectively. For comparison, the experimental result (the empty square) of Catalano et al is also displayed [17].…”

Keldysh photoionization theory: through the barriers

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