Ultrafast Optical Control Of Upconversion Luminescence In Rare-earth Ions

Rare-earth ion doped upconversion luminescence materials have the advantages of abundant energy levels,good optical stability and narrow emission band.Therefore,it has been applied to several areas,such as laser source,color display,solar cell and biomedical imaging.To improve the performance of rare-earth ion doped upconversion luminescence materials and further extend its application fields,the upconversion luminescence control in rare-earth ion doped materials has been widely studied,such as the luminescence intensity enhancement and color tuning.Up to now,three strategies have been proposed to control the upconversion luminescence of rare-earth ions: changing component and structure of materials,adjusting external condition and modulating excitation source.Especially,the excitation source modulation has attracted considerable interest because it can provide a convenient,real-time and reversible modulation of upconversion luminescence in a single material.In previous studies,the main work focused on the upconversion luminescence control of rare-earth ions under the excitation of a continuous wave laser.However,the upconversion luminescence generation and control mechanisms of rare-earth ions under the femtosecond laser excitation were rarely studied.In this dissertation,we focused on the study of the upconversion luminescence control in rare-earth ions by modulating the femtosecond laser field,and the main contents are summarized as follows:1.We experimentally studied the influences of femtosecond laser polarization and phase modulation on upconversion luminescence in Dy3+-doped glass.The upconversion luminescence intensity decreases when the laser polarization changes from linear through elliptical to circular.The upconversion luminescence can be suppressed by a ? step phase modulation,and the suppress efficiency depends on the laser polarization.2.We proposed a new method to control the polarization modulation efficiency of upconversion luminescence in rare-earth ions by tailoring the femtosecond spectral components,and the proposed scheme is experimentally confirmed in Dy3+-doped glass.Our experimental results showed that the polarization control efficiency of upconversion luminescence can increase when the central frequency components of femtosecond laser are cutoff,while can decrease when the high and low frequency components are cutoff.3.We built an adaptive feedback femtosecond pulse shaping system based on a genetic algorithm,and achieved the optimal control of green-red upconversion luminescence tuning in Er3+-doped glass using this system.The Green-red intensity ratio can be effectively enhanced and suppressed using the optimal feedback control strategy.Moreover,the enhancement and suppress mechanisms can be well explained based on our proposed theoretical model.4.We utilized two-wavelength continuous wave laser method to enhance the upconversion luminescence in rare-earth ions.The upconversion luminescence intensity of Er3+/Yb3+-codoped glass increases with the two laser excitation with the wavelengths of 800 and 980 nm,and a cooperative upconversion model was proposed to explain the enhancement phenomenon.Besides,the two lasers with the wavelengths of 850 and 980 nm were also used to enhance the upconversion luminescence in Er3+-doped ceramic glass.Similarly,the enhancement mechanism was also explored.