Study On Ultrafast Control Of Up-conversion Luminescence In Rare-earth Ions Under Intermediate Femtosecond Laser Field

Controlling the up-conversion luminescence of rare-earth ions in the real-time,dynamical and reversible manners is very important for their applications in laser source,fiber-optic communication,light-emitting diode,color display and biological system.It has been shown that the femtosecond laser phase and polarization modulation are the very simple and well-established methods to control the multi-photon absorption process by the light-matter interaction.In previous studies,the up-conversion luminescence control mainly focused on the weak femtosecond laser field.Here,we further extend this control behavior from the weak to intermediate femtosecond laser fields.In the weak femtosecond laser field,the second-order perturbation theory can well describe the non-resonant two-photon absorption process.However,the higher order nonlinear effect(i.e.,four-photon absorption)can occur in the intermediate femtosecond laser field,and thus we establish a new theoretical model(i.e.,the fourth-order perturbation theory)to explain the physical control mechanism by considering the two-and four-photon absorption processes.The main research results are presented as follows:(1)We experimentally and theoretically demonstrate that the up-conversion luminescence in Dy3+ ion doped glass can be artificially controlled by a ? phase step modulation,but the up-conversion luminescence control behavior will be affected by the femtosecond laser intensity,and the up-conversion luminescence is suppressed with the lower laser intensity while enhanced with the higher laser intensity.The theoretical results show that the relative weight of the four-photon absorption in the whole excitation process will increase with the increase of the laser intensity,and the interference between resonant two-and four-photon absorptions results in the up-conversion luminescence control modulation under different laser intensities.(2)The polarization modulation strategy of the femtosecond laser field has shown to be a well-established method to control the up-conversion luminescence in rare-earth ions.We construct a fourth-order perturbation theory to study the polarization control behavior of the up-conversion luminescence in the Sm3+-doped glass under the intermediate femtosecond laser field excitation.We experimentally show that the polarization control efficiency of the up-conversion luminescence in the Sm3+-doped glass will be affected by the femtosecond laser intensity,which decreases with the increase of the laser intensity.We theoretically propose a fourth-order perturbation theory to explain the experimental observation,which includes the two-photon and four-photon absorptions,and the destructive interference between the nonresonant two-photon and four-photon absorption will result in the suppression of the polarization control efficiency due to their different polarization control degrees.