Saturation of optical absorption in crystals

A. V. Shubnikov

Vasyl P. Kunets

The nonlinear optical transmission of CdSe single crystals and saturation thresholds at different polarizations of the pumping wave are studied in a range of the exponential absorption tail. Theoretical calculations performed in the framework of a two-level model with the twofold degenerate ground state corresponding to the optical transitions in E ⟂ C and E‖ C polarizations are also presented. Results obtained for the absorption saturation regime clearly witnesses in favour of the polarization self-action effect and relaxation processes between transitions polarized orthogonally.

Hergen Eilers, K.R. Hoffman, William M. Dennis +2 more

Saturation absorption experiments are conducted on the title compound at 1.064 μm with laser light propagating along both the [001] and [111] crystallographic axes. Rotation of the crystals about these axes during the experiments reveals that the transmission of the polarized 1.064 μm radiation is highly anisotropic in the saturation regime. The details of the anisotropy and saturation curves are explained using a simple model of subsets of optical centers along with a relevant set of rate equations. The ground and excited-state absorption cross sections at 1.064 μm are calculated to be σgs=5.7(±2)×10−18 cm2 and σes=8(±2)×10−19 cm2, respectively, and the optimum crystallographic orientation for utilization in optical devices is discussed.

E. Yu. Perlin

Elena Kuznetsova, Roman L. Kolesov, Olga A. Kocharovskaya

Santiago Camacho-López, R.P.M. Green, Graham J. Crofts +1 more

We studied both experimentally and theoretically the transmission and polarization characteristics of a Cr4+ : YAG saturable absorber crystal as a function of the intensity and polarization state of an incident laser beam. We found that a birefringent absorption behaviour is induced and we show that the experimental results are well described by a full numerical model which includes excited-state absorption as well as a ground-state cross-absorption term. By using pump-probe measurements we show that a finite cross-saturation of the absorption is achieved along the crystal axes orthogonal to the polarization of the optical radiation. No induced refractive index birefringence is observed.