LAUSR

A multiphoton absorption is one of the main nonlinear optical characteristics of semiconductor quantum dots (QDs). In this paper, we report on four-photon absorption of ZnSe:Mn QDs. The four-photon excitation spectrum is characterized under 1350 nm excitation with 50 fs femtosecond laser pulses. The experimental results indicate that the highest absorption coefficient was 2.87 × 10⁻⁵ cm⁵ /GW³ for Mn doping of 170 μl, and corresponding cross-section is 2.03 × 10⁻⁷⁹ cm⁸·s³. We also proved that it has low biotoxicity. The results of our studies suggest that these QDs can potentially be used to detect electric fields, limit laser power, and for biosensing applications.